CN114465270A - One-stop intelligent megawatt box system based on TE-SVM modulation, intelligent controller and control method thereof - Google Patents

Abstract

The invention discloses a one-stop intelligent megawatt box system based on TE-SVM modulation, an intelligent controller thereof and a control method thereof_fAnd R_fA current correction module for correcting the three-phase average current output by the assembly, a positive and negative sequence theory active reference current conversion module, a positive and negative sequence theory reactive reference current conversion module and an output voltage U_α+、U_β+ two-phase positive sequence static voltageChanging module, output voltage U_α‑、U_β-a two-phase negative sequence static voltage transformation module, a TE-SVM wave-transmitting module for estimating the smart grid frequency based on the TLS-ESPRIT algorithm, the TE-SVM wave-transmitting module using the voltage U_α+、U_β+ and U_α‑、U_β-synthesizing the reference voltage and controlling inverter inversion based on the estimated smart grid frequency ripple.

Description

One-stop intelligent megawatt box system based on TE-SVM modulation, intelligent controller and control method thereof

Technical Field

The invention belongs to the field of power transmission and distribution of an Internet of things smart power grid, and relates to a one-stop smart megawatt box system based on TE-SVM modulation, a smart controller friendly to access to the smart power grid and a control method of the smart controller.

Background

With the fact that the proportion of the new photovoltaic energy accessed to the traditional power grid is close to the upper acceptance limit, the smart power grid is used as a basic unit of the global energy Internet, and the advanced power electronic controller is introduced, so that the purpose that the one-stop smart megawatt box system is friendly to grid-connected smart power grid, and clean energy is efficiently supplied is achieved. In practical applications, the above research results reveal some problems that need to be solved urgently: one-stop intelligent megawatt box system photovoltaic power generation is a green clean energy, and brings some adverse effects to the distribution network, such as overvoltage, three-phase imbalance, frequency deviation, harmonic pollution, voltage sag and other electric energy quality problems, for example: the existing synchronous coordinate software phase-locked loop control method has the advantages of simplicity, high response speed and the like, but when three phases are unbalanced and contain high-frequency subharmonic voltage, the phase-locked result has large error, a proportional-integral (PI) regulator can be adopted to reduce the bandwidth of a system to reduce the error, but the response speed is greatly reduced, and the requirement of the system is difficult to meet. The existing phase locking technology does not have the function of adjusting the optimal frequency matched with the phase and the amplitude in time when the frequency of the power grid deviates, and the frequency and the phase of the power grid which do not deviate are still locked, so that the inversion fails. Especially when voltage drops greatly, the phase locking can not be achieved due to the absence of voltage, the reactive power is 0, the reactive power supporting capability to a power grid is insufficient, the voltage stability is reduced, and the fault voltage fluctuation is large.

At present, PI regulation and low-pass filtering adopted by an inverter modulation technology relate to limited management and control factors, effective regulation of all voltage, current, phase, amplitude, power and other factors from an input end of a photovoltaic cell array to an output and grid-connected point phase lock is not included, but the fluctuation of any one factor of all voltage, current, phase, amplitude, power and other factors from the input end of the photovoltaic cell array to the output and grid-connected point phase lock can greatly reduce the efficiency and the inversion quantity of a converter and an inverter. The unbalanced disturbance current component is difficult to correct by adopting current Proportional Integral (PI) control, the positive sequence current component and the negative sequence current component cannot be independently controlled, the compensation capability of low-order harmonic waves is poor, the power grid is widely accessed, the power grid has weak power grid characteristics, time-varying linear impedance and background harmonic waves exist, and particularly, the inductance part of the power grid impedance has influence on the current control performance even if the active or passive damping of LCL filtering is adopted to suppress the harmonic waves. When the inductance of the power grid is large, for an LCL type inverter adopting a current open single-loop control strategy, the change of the inductance of the power grid can cause the deviation of the resonant frequency of the LCL type inverter, the existing modulation controller cannot track the frequency of the deviation, an LCL filter is a three-order system, and a resonant peak and a brought harmonic problem exist at the resonant frequency of the LCL filter, so that the system is unstable and becomes an important factor influencing the power quality of the power grid and the normal operation of electric equipment. The conventional modulation controller adopting algorithm transformation such as SVM (space vector machine), Fourier algorithm, neural network, ESPRIT (rotation invariant subspace) and the like has large calculated amount and long consumed time of harmonics and inter-harmonics, noise of a noise subspace is large, frequency, amplitude and phase cannot be accurately and sequentially estimated, and the real-time and synchronization requirements of the smart grid cannot be met; at present, no clean and friendly grid-connected intelligent power grid controller which meets real-time performance and synchronism and comprehensively controls the phase-locked end connected to the power grid from the input end exists.

Disclosure of Invention

In order to solve the problems, the invention provides a one-stop intelligent megawatt box system based on TE-SVM modulation, an intelligent controller and a control method thereof, which aim to solve the problems that the reactive support capability of a power grid is insufficient after the occupation ratio of new photovoltaic energy is increased, the voltage stability is reduced, the fluctuation of fault voltage is large, PI control cannot independently control positive sequence current and negative sequence current, eliminate low-order harmonic and higher harmonic, and has slow response speed and low capability, the problem that a PLL phase lock of a controller of the existing photovoltaic power generation system does not control all factors such as voltage, current, phase, amplitude, power and the like from an input end to a phase lock end, the problem that the controller of the existing photovoltaic power generation system cannot track the resonance frequency deviation of an LCL type inverter adopting a current open single-loop control strategy, and the problem that resonance peak exists at the resonance frequency of an LCL filter and causes harmonic waves to influence the power quality of the power grid, the problem that the inversion efficiency of the existing inverter is low and the problem that the frequency, the amplitude and the phase cannot be accurately estimated by a controller of the existing photovoltaic power generation system, so that a photovoltaic inverter power generation grid-connected intelligent power grid cannot meet the requirement of real-time synchronism.

The technical scheme adopted by the invention is that the intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation comprises:

MPPT controller for tracking maximum power of DC/DC converter and outputting positive sequence DC reference voltage U_ref+ and a DC reference current

A positive and negative sequence voltage decomposition module for detecting the three-phase voltage V at the side of the inverter network_a、V_b、V_cDecomposed into positive sequence three-phase voltage V_a+、V_b+、V_c+ and negative sequence three-phase voltage V_a-、V_b-、V_c-；

Phase-locked loop for positive sequence three-phase voltage V according to input_a+、V_b+、V_cGive the initial angle of voltageθ and frequency f;

a current correction module for correcting the current according to the three-phase standard current I'_a、I′_b、I′_cAnd inverter side inductance L of LCL filter_fThree-phase detection current I of_a、I_b、I_cFor C of LCL filter_fAnd R_fThree-phase average current I output at the module_aavg、I_bavg、I_cavgCorrecting;

a first 3S/2R conversion module for detecting the input three-phase current I_a、I_b、I_cPerforming 3S/2R conversion to output positive sequence actual active current I'_d+Positive sequence actual reactive current I'_q+Negative sequence actual active current I'_d-Negative sequence actual reactive current I'_q-；

A positive and negative sequence theory active reference current conversion module for converting the three-phase voltage V at the input grid-connected point_ga、V_gb、V_gcAnd standard three-phase voltage V'_a、V′_b、V′_cComparing, and PI controlling the comparison result to output theoretical active reference current

Positive sequence theory active reference current

Negative sequence theory active reference current

A positive and negative sequence theory reactive reference current conversion module for converting the input theoretical active reference current

And using formulas

Obtaining theoretical reactive reference current by inverse calculation

Then to the DC reference current

And theoretical reactive reference current

Comparing and outputting positive sequence theoretical reactive reference current

Negative sequence theory reactive reference current

The two-phase positive sequence static voltage conversion module is used for converting the three-phase standard voltage V 'according to the input three-phase standard voltage'_a、V′_b、V′_cOutput of the current correction module, voltage initial angle theta, positive sequence three-phase voltage V_a+、V_b+、V_cd.C bus capacitor voltage U_busPositive sequence DC reference voltage U_refOutput current I of the photovoltaic array_pvAverage current I output by the whole DC system of the photovoltaic array_pvavgPositive and negative sequence theory active reference current

Actual active current I 'of positive and negative sequences'_d+、I′_d-Converted to obtain two-phase positive sequence static voltage U_α+、U_β+；

The two-phase negative sequence static voltage conversion module is used for converting the three-phase standard voltage V 'according to the input three-phase standard voltage'_a、V′_b、V′_cOutput of the current correction module, voltage initial angle theta, negative sequence three-phase voltage V_a-、V_b-、V_cPositive sequence reactive DC reference current I_qrefPositive and negative sequence theoretical reactive reference current

Actual reactive current I 'of positive and negative sequence'_q+、I′_q-Converted to obtain two-phase negative sequence static voltage U_α-、U_β-；

The TE-SVM wave-transmitting module estimates the frequency of the smart grid based on the TLS-ESPRIT algorithm and utilizes the two-phase positive sequence static voltage U_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_βSynthesizing three-phase reference voltage, taking the power grid frequency output by the phase-locked loop or the smart power grid frequency solved by the TLS-ESPRIT algorithm as wave-sending frequency, and sending waves by combining the synthesized three-phase reference voltage to control the inverter to invert.

Further, the current modification module includes:

a first comparator of the current correction module for comparing C of the LCL filter_fAnd R_fThree-phase average current I at the assembly_aavg、I_bavg、I_cavgInverter side inductor L with LCL filter_fThree-phase current I of_a、I_b、I_cConverging and carrying out error comparison;

a proportional controller for proportionally controlling the output of the first comparator;

a second comparator of the current correction module for comparing the output of the comparative controller with the three-phase standard current I'_a、I′_b、I′_cCarrying out error comparison;

the two-phase positive sequence static voltage conversion module comprises:

a positive sequence active and reactive current conversion module for converting the output result of the current correction module to obtain positive sequence theoretical active current I_d+ and positive-sequence theoretical reactive current I_q+；

A positive sequence voltage conversion module for converting the input three-phase standard voltage V'_a、V′_b、V′_cCoordinate transformation and filtering are carried out to obtain positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+；

A first positive-sequence active reference current conversion module for converting the input DCCapacitor voltage U_busPositive sequence DC reference voltage U_ref+ performing coordinate transformation and PI control to obtain a first positive-sequence active reference current I_dref1+；

A second positive-sequence active reference current conversion module for outputting current I to the input photovoltaic array_pvAverage current I output by the whole direct current system of the photovoltaic array_pvavgComparing and PI controlling to obtain a second positive sequence active reference current I_dref2+；

A positive sequence third comparator for the first positive sequence active DC reference current I_dref1+A second positive-sequence active direct-current reference current I_dref2+Positive sequence theoretical active current I_dPositive and negative sequence theory active reference current

And positive sequence actual active current I'_d+Converging and carrying out error comparison;

a third PI controller for performing proportional-integral control on the output current of the positive sequence third comparator and outputting a positive sequence active DC reference voltage U_d+；

A positive sequence fourth comparator for positive sequence reactive DC reference current I_qrefPositive and negative sequence theory idle current I_qPositive and negative sequence theory reactive reference current

And positive sequence actual reactive current I'_q+Converging and carrying out error comparison;

a fourth PI controller for performing proportional-integral control on the output current of the positive sequence fourth comparator and outputting a positive sequence reactive DC reference voltage U_q+；

A positive sequence low voltage ride through control module for detecting whether voltage drop occurs at the grid-connected point, performing low voltage ride through control when the voltage drop occurs at the grid-connected point, controlling the input of the third PI controller and the fourth PI controller, and further controlling the generation of positive sequence reactive DC reference voltage U at different moments_qInjecting reactive power into the power grid to enable the photovoltaic power generation to operate without grid disconnection;

first cross coupler ω L for aligning positive sequence reactive current I_d+ and positive sequence reactive current I_q+ cross-coupling to counteract reactive current I_d+ and positive sequence reactive current I_q+ coupling term, subjecting d-axis component to I_dAction of + q-axis component by I_q+ to function;

a positive sequence fifth comparator for positive sequence active DC reference voltage U_dPositive and negative active voltage V_dThe active outputs of the + and the +/-omega L of the first cross coupler are converged to carry out error comparison;

a positive sequence sixth comparator for positive sequence reactive DC reference voltage U_qPositive and negative sequence reactive voltage V_q+ and the reactive output of the first cross coupler +/-omega L are converged, and error comparison is carried out;

a first 2R/2S coordinate transformation module for performing 2R/2S coordinate transformation on the outputs of the positive sequence fifth comparator and the positive sequence sixth comparator according to the input voltage initial angle theta to obtain a two-phase positive sequence static voltage U_α+、U_β+。

Further, the positive sequence active and reactive current conversion module comprises:

a second 3S/2R conversion module for performing 3S/2R coordinate conversion on the output result of the current correction module according to the input voltage initial angle theta and outputting a positive sequence active current I_d+ and positive sequence reactive current I_q+；

A first low pass filter LPF for correcting the positive sequence active current I_d+ and positive sequence reactive current I_q+ low-pass filtering to eliminate high frequency part and maintain low frequency part;

a first band pass filter BPF for performing band pass filtering on the output of the first LPF, filtering noise outside the bandwidth, and outputting a clean positive-sequence active current I_d+ and positive sequence reactive current I_q+；

The positive sequence voltage conversion module includes:

a third 3S/2R conversion module for converting the input three-phase standard voltage V 'according to the input voltage starting angle theta'_a、V′_b、V′_cPerforming 3S/2R coordinate conversion and outputting positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+；

A second low pass filter LPF for correcting the positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+ low-pass filtering to eliminate high frequency part and maintain low frequency part;

a second band-pass filter BPF for performing band-pass filtering on the output voltage of the second low-pass filter LPF, filtering noise outside the bandwidth, and outputting a clean positive-sequence active voltage V_d+ and positive sequence reactive voltage V_q+；

The first positive sequence active reference current conversion module comprises:

positive sequence first comparator for DC capacitor voltage U_busAnd positive sequence DC reference voltage U_ref+ converging and comparing errors;

the fourth 3S/2R conversion module is used for performing 3S/2R coordinate conversion on the output result of the positive sequence first comparator and removing alternating current harmonic components in the direct current voltage;

a first PI controller for performing proportional-integral control on the output voltage of the fourth 3S/2R conversion module and outputting a first positive-sequence active direct-current reference current I_dref1+；

The second positive sequence active reference current conversion module comprises:

a positive sequence second comparator for the output current I of the photovoltaic array_pvAverage current I output by the whole direct current system of the photovoltaic array_pvavgConverging and comparing errors;

a second PI controller for performing proportional-integral control on the output current of the positive sequence second comparator and outputting a second positive sequence active direct current reference current I_dref2+。

Further, the positive sequence low voltage ride through control module comprises:

a first low voltage ride through module for outputting three-phase voltage V according to input_a、V_b、V_cDetecting whether voltage drop occurs at a grid-connected point, performing droop control, and outputting a droop voltage root-mean-square;

the first root mean square detection module is used for performing root mean square detection on the output of the first low-voltage ride-through module;

the reference power calculation module is used for calculating a fundamental wave active power instantaneous value and a fundamental wave reactive power instantaneous value, and correspondingly comparing the fundamental wave active power instantaneous value and the reactive power instantaneous value with standard active power and reactive power and actual power at an intelligent grid-connected point to obtain reference power P^*；

A third 2R/2S coordinate conversion module for correcting positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+ 2R/2S coordinate conversion to obtain negative sequence positive sequence two-phase static voltage U_a、U_B；

A first reference current calculation module for calculating a reference power P^*Two-phase static voltage U_a、U_BCalculating a positive sequence reference current

A first voltage and current calculation module for calculating a positive-sequence two-phase static voltage U_a、U_BAnd positive sequence reference current

Combination formula

And

calculating the voltage U of the grid-connected point_NAnd current I_total；

The first voltage drop determining module is used for determining the voltage drop delta U according to the result of the first root mean square detection module when low voltage ride through occurs, and determining the voltage when the low voltage ride through is performed on the voltage drop of the grid-connected point and the grid-connected point voltage U when the droop voltage root mean square exists_NComparing to obtain a voltage drop delta U; when the droop voltage root mean square does not exist, namely the voltage drop at the grid-connected point is lowVoltage during voltage ride through and grid point voltage U_NWhen the two phases are equal, the zero voltage ride through is shown to occur, and the three-phase average voltage V output by the inverter is adopted_iava、V_iavb、V_iavcAnd grid point voltage U_NComparing to obtain a voltage drop delta U;

the first low voltage ride through control module sets the positive sequence active power to 0 when low voltage ride through occurs, namely the positive sequence active current

I_d+、I’_d+Is 0, the power factor is set to be 1, and the positive sequence reactive reference current I under the condition of 1 power factor is output_qref+Performing low voltage ride through control according to the voltage drop delta U; then current flows

I_q+、I’_q+、I_qref+Comparing to obtain the maximum difference value delta i_q+Positive sequence reactive current Δ i_q+As initial suitable current I_rectiveInputting the positive sequence reactive voltage U generated by the fourth PI controller_q+Performing reactive compensation and adapting to the current I_rectiveAnd the total current I_totalGradually rises to 20%, and the voltage drop delta U and the voltage U are_NThe ratio reaches 10 percent; positive sequence active current

I_d+、I’_d+、I_dref1+、I_dref2+Comparing to obtain the maximum difference value delta i_d+Will be positive sequence active current Δ i_d+Inputting the positive sequence active voltage U generated by a third PI controller_d+Positive sequence active current Δ i_d+And positive sequence reactive current Δ i_q+Synthesized as a suitable current I_rectivVoltage drop Δ U and voltage U_NThe ratio is gradually increased from 10% to 20%, and the active current delta i is in positive sequence_d+And positive sequence reactive current Δ i_q+Under continuous injection of (2), current ratio I_rective/I_totalGradually increasing from 20% to 45%, and keeping the inverter in uninterrupted operation for 1sThe power factor decreases from 1, Δ U/U_NGradually increased to 50% and adapted to the current I_rectiveReach I from 0 within 4s_totalThe power factor is reduced to 0, and the positive sequence reactive current is delta i_q+And 0, normally injecting positive sequence active power into the power grid.

Further, the two-phase negative sequence static voltage conversion module includes:

a voltage initial phase angle determining module for determining the three-phase voltage V according to the input voltage initial angle theta and the negative sequence three-phase voltage V_a-、V_b-、V_c-, converting to obtain a voltage initial phase angle

A negative sequence active and reactive current conversion module for converting the output result of the current correction module to obtain the negative sequence theoretical active current I_dAnd negative sequence theoretical reactive current I_q-；

A negative sequence voltage conversion module for converting the input three-phase standard voltage V'_a、V′_b、V′_cConverting to obtain negative-sequence active voltage V_d-and positive sequence reactive voltage V_q-；

A fifth PI controller for negative-sequence active current I_dNegative sequence actual active current I'_d-And negative sequence theory active reference current

PI control is carried out, and negative sequence active direct current reference voltage U is output_d-；

Negative sequence first comparator for negative sequence reactive current I_qNegative sequence reactive DC reference current I_qrefNegative sequence actual reactive current I'_q-And negative sequence theory reactive reference current

Converging and carrying out error comparison;

a sixth PI controller for PI controlling the output current of the negative sequence first comparator to output negative sequence withoutReference voltage U of power direct current_q-；

The negative sequence low voltage ride through control module is used for detecting whether voltage drop occurs at the grid-connected point or not, performing low voltage ride through control when the voltage drop occurs at the grid-connected point, controlling the input of the fifth PI controller and the sixth PI controller, and further controlling the generation of a negative sequence active direct current reference voltage U at different moments_qInjecting reactive power into the power grid, so that the photovoltaic power generation does not run off the grid;

a second cross-coupler ω L for the negative-sequence reactive current I_dWith negative-sequence reactive current I_q-cross-coupling to cancel the negative sequence reactive current I_dWith negative-sequence reactive current I_qCoupling term of (d) by the d-axis component_dThe q-axis component is given by_q-an effect of;

negative sequence second comparator for negative sequence active DC reference voltage U_dNegative-sequence active voltage V_dConverging the active outputs of the second cross-coupler by +/-omega L to carry out error comparison;

a negative sequence third comparator for negative sequence reactive DC reference voltage U_qNegative sequence reactive voltage V_q-and reactive outputs of the second cross-couplers ± ω L converge, making an error comparison;

a second 2R/2S coordinate transformation module for transforming the initial voltage angle theta and the initial voltage phase angle theta

2R/2S coordinate transformation is carried out on the output of the negative sequence second comparator and the negative sequence third comparator to obtain two-phase negative sequence static voltage U_α-、U_β-；

The TE-SVM wave-transmitting module comprises:

the TLS-ESPRIT frequency estimation module is used for estimating the frequency of the smart grid based on a TLS-ESPRIT algorithm;

the SVM wave-transmitting module is used for transmitting the two-phase positive sequence static voltage U_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_β-, synthesizing three-phase reference voltages

Wave sending is carried out according to the power grid frequency output by the phase-locked loop or the frequency of the intelligent power grid estimated by the TLS-ESPRIT frequency estimation module;

and the gate controller is used for controlling each switch module of the inverter to be switched on or switched off according to the vector signal sent by the SVM wave sending module.

Further, the voltage initial phase angle determination module comprises:

a fifth 3S/2R conversion module for converting the input negative sequence three-phase voltage V according to the input voltage initial angle theta_a-、V_b-、V_c-carrying out 3S/2R coordinate conversion to obtain an active voltage V_dAnd a reactive voltage V_q；

A module for calculating an initial phase angle according to the active voltage V_dAnd a reactive voltage V_qCalculating to obtain the initial phase angle of voltage

The negative sequence active and reactive current conversion module comprises:

a sixth 3S/2R transformation module for transforming the voltage according to the voltage initial angle theta and the voltage initial phase angle

3S/2R coordinate conversion is carried out on the output current of the current correction module, and negative-sequence active current I is output_d-and a negative sequence reactive current I_q-；

A third low pass filter LPF for the negative sequence active current I_d-and a negative sequence reactive current I_q-low-pass filtering to remove the high frequency part and to retain the low frequency part;

a third band-pass filter BPF for performing band-pass filtering on the output current of the third low-pass filter LPF, filtering noise outside the bandwidth and outputting a clean negative-sequence active current I_d-and a negative sequence reactive current I_q-；

The negative sequence voltage conversion module includes:

seventh 3S/2R transformA module for determining the initial voltage angle

To the input three-phase standard voltage V'_a、V′_b、V′_c3S/2R coordinate conversion is carried out, and negative sequence active voltage V is output_d-and negative sequence reactive voltage V_q-；

A fourth low pass filter LPF for applying a negative sequence active voltage V_d-and negative sequence reactive voltage V_q-low-pass filtering to remove the high frequency part and to retain the low frequency part;

a fourth band-pass filter BPF for band-pass filtering the output voltage of the fourth LPF, filtering out noise outside the bandwidth and outputting clean negative-sequence active voltage V_d-and positive sequence reactive voltage V_q-；

The negative sequence low voltage ride through control module comprises:

a second low voltage ride through module for outputting a negative sequence three-phase voltage V according to the input_a-、V_b-、V_cDetecting whether voltage drop occurs at a grid-connected point, performing droop control, and outputting a droop voltage root mean square;

the second root mean square detection module is used for performing root mean square detection on the output of the second low-voltage ride through module;

a third-order negative-sequence maximum current calculating module for calculating the positive-sequence reactive DC reference current I_qref+, maximum current I_maxInitial phase angle of sum voltage

Calculating the third-order negative-sequence maximum current I_qmax-；

A fourth 2R/2S coordinate conversion module for converting the negative-sequence active voltage V_d-and negative sequence reactive voltage V_q-2R/2S coordinate transformation to obtain a negative-sequence two-phase rest voltage U_a、U_B；

A second reference current calculation module for calculating a reference power P^*Negative sequence two-phase static voltage U_a、U_BCalculating a negative sequence reference current

A second voltage and current calculation module for calculating two-phase static voltage U according to negative sequence_a、U_BAnd negative sequence reference current

Combination formula

And

calculating the voltage U of the grid-connected point_NAnd current I_total；

The second voltage drop determining module is used for determining the voltage drop delta U according to the result of the second root mean square detection module when low voltage ride through occurs, and determining the voltage when the low voltage ride through is performed on the voltage drop of the grid-connected point and the grid-connected point voltage U when the droop voltage root mean square exists_NComparing to obtain a voltage drop delta U; when no droop voltage root mean square exists, namely the voltage of the grid-connected point during low voltage ride through when the grid-connected point has voltage drop and the grid-connected point voltage U_NWhen the two phases are equal, the zero voltage ride through is shown to occur, and the three-phase average voltage V output by the inverter is adopted_iava、V_iavb、V_iavcAnd grid point voltage U_NComparing to obtain a voltage drop delta U;

the second low voltage ride through control module performs low voltage ride through control according to the voltage drop delta U when low voltage ride through occurs, and sets the negative sequence reactive power to 0, namely negative sequence reactive current

I_q-、I’_q-Set to 0; power factor is set to 1, and low voltage ride-through control is performed according to voltage drop delta UPreparing; then the

I_d-、I’_d-Comparing to obtain the maximum difference value delta i_d-Negative sequence active current Δ i_d-As initial suitable current I_rectiveInputting the negative sequence active voltage U into a fifth PI controller_d-Is adapted to the current I_rectivAnd the total current I_totalGradually rises to 20%, and the voltage drop delta U and the voltage U are_NThe ratio of (A) to (B) reaches 10% and starts to rise; negative sequence reactive current

I_q-、I’_q-、I_qref-Comparing to obtain the maximum difference value delta i_q-Negative sequence reactive current Δ i_q-Inputting the voltage into a sixth PI controller which generates a negative sequence reactive voltage U_q-Negative sequence reactive current Δ i_q-And negative sequence active current delta i_d-Synthesized as a suitable current I_rectivVoltage drop Δ U and voltage U_NThe ratio is gradually increased from 10% to 20%, and the reactive current delta i in the negative sequence_q-And negative sequence active current delta i_d-Under continuous injection of (2), current ratio I_rective/I_totalGradually increasing from 20% to 45%, keeping the inverter in uninterrupted operation for 1s, and decreasing the power factor from 1 to delta U/U_NGradually increased to 50% and adapted to the current I_rectiveReach I from 0 within 4s_totalAnd when the power factor is reduced to 0, the negative sequence active current injects negative sequence active power to the power grid normally, and the negative sequence reactive voltage of the negative sequence reactive power is limited.

Another technical solution adopted in the embodiments of the present invention is a control method for a one-stop intelligent megawatt box system based on TE-SVM modulation to access to an intelligent power grid in a friendly manner, wherein the intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation is adopted, and the control method is performed according to the following steps:

step S1, receiving the actual active power and reactive power at the intelligent grid-connected point, and outputting a three-phase voltage V by the inverter_a、V_b、V_cThree-phase voltage V at grid-connected point_ga、V_gb、V_gcThree-phase average voltage V_iava、V_iavb、V_iavcThree-phase current I_a、I_b、I_cThree-phase average current I_aavg、I_bavg、I_cavgDC bus capacitor voltage U_busOutput current I of the photovoltaic array_pvAverage current I_pvavgAnd tracking the maximum power of the DC/DC converter by adopting an MPPT controller to output a positive sequence direct current reference voltage U_ref+ and a DC reference current

Step S2, calculating standard active power and reactive power, and an active power instantaneous value and a reactive power instantaneous value at an intelligent grid connection point;

step S3, judging whether the actual active power and reactive power at the intelligent grid-connected point are corresponding to the calculated active power instantaneous value and reactive power instantaneous value at the intelligent grid-connected point and the standard active power and reactive power; judging whether the frequency output by the phase-locked loop is within the range of 50 +/-0.1 Hz;

s4, when the actual active power and the reactive power at the intelligent grid-connected point are correspondingly consistent with the calculated active power instantaneous value and the calculated reactive power instantaneous value at the intelligent grid-connected point, and the standard active power and the calculated reactive power are consistent, and the frequency output by the phase-locked loop is within the range of 50 +/-0.1 Hz, taking the frequency output by the phase-locked loop as the wave-transmitting frequency of the SVM wave-transmitting module; otherwise, carrying out frequency search of the smart power grid by using the TLS-ESPRIT frequency estimation module, and taking the searched frequency as the wave transmitting frequency of the SVM wave transmitting module;

step S5, calculating three-phase standard voltage V 'according to the voltage and current signals received in step S1'_a、V′_b、V′_cThree-phase Standard Current I'_a、I′_b、I′_cStandard active power and reactive power, active power instantaneous value and reactive power instantaneous value at intelligent grid-connected point, by means of two-phase positive sequence static voltage conversion module andthe two-phase negative sequence static voltage conversion module obtains a two-phase positive sequence static voltage U_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_β-; utilizing an SVM wave-transmitting module to transmit a voltage U according to a two-phase positive sequence_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_βSynthesizing a reference voltage, then carrying out SVM wave-sending based on the wave-sending frequency and the reference voltage, and controlling each switch module of the inverter to be switched on or switched off by adopting SVPWM (space vector pulse width modulation) according to a vector signal generated by the SVM wave-sending by a voltage-sharing gate controller.

Further, in step S5:

calculating a three-phase standard voltage V 'according to the formula (1)'_a、V′_b、V′_c：

Wherein, V_pIs the positive sequence voltage peak, V_nIs the peak value of the negative-sequence voltage,

is the initial phase angle of the positive sequence voltage,

is the initial phase angle of the negative sequence voltage; ω is the fundamental voltage angular frequency;

three-phase standard current I'_a、I′_b、I′_cCalculating according to the formula (2):

wherein, I_pIs the peak value of the positive sequence current, I_nIs the peak value of the negative-sequence current, theta_pIs the starting angle of the positive and negative sequence currents with respect to the positive sequence voltage, θ_nIs the starting angle of the negative sequence voltage relative to the negative sequence voltage;

in step S5, positive and negative sequence impedances are calculated when the first low voltage ride through module and the second low voltage ride through module perform droop control, wherein:

positive sequence impedance Z_P(S) calculating according to the formula (3):

wherein, K_mIs the inverter voltage gain, V_dcIs the voltage difference between two ends of the DC bus capacitor, H_i(s-j2πf₁) Is the closed loop transfer function, T, of the current inner loop PI controller, i.e. the first PI controller_PLL(s-j2πf₁) Is the closed loop transfer function of the phase locked loop, f₁At fundamental frequency, K_dAs a gain of a weighting function, K_fAs integral proportional parameter, G_i(s) is the equivalent transfer function of the current filter consisting of the first low-pass filter LPF and the first band-pass filter BPF, L_fInductance value of inverter-side inductor of LCL filter, c₁Is a DC bus capacitance value; g_v(s) is the equivalent transfer function of the voltage filter consisting of the second low pass filter LPF and the second band pass filter BPF, s denotes the complex frequency domain,

is the initial phase angle of the fundamental current, I₁Is the peak value of the fundamental current, V₁Is the peak value of the grid voltage;

negative sequence impedance Z_n(S) calculating according to the formula (4):

wherein H_i(s+j2πf₁) Is the closed loop transfer function of the current inner loop PI controller, i.e. the first PI controller, G_i(s) is the equivalent transfer function of the current filter consisting of the first low-pass filter LPF and the first band-pass filter BPF, G_v(s) is the equivalent transfer function of the voltage filter consisting of the fourth low pass filter LPF and the fourth band pass filter BPF;

the standard active power and the standard reactive power are calculated according to formulas (7) to (8):

wherein P (t) is standard active power, Q (t) is standard reactive power, V_α、V_βFor corresponding voltages in the stationary reference frame of α β, I_α、I_βFor corresponding currents in the stationary reference frame of α β, θ₁For the starting angle of the actual current of the grid with respect to the voltage, theta₂A starting angle for the phase-locked loop output;

the active power instantaneous value and the reactive power instantaneous value at the intelligent grid-connected point are calculated according to a formula (9):

wherein, P₀(t) is the instantaneous value of the active power of the fundamental wave, Q₀(t) is the fundamental reactive power instantaneous value; v_pIs the positive sequence voltage peak, V_nIs the negative sequence voltage peak; i is_pIs the peak value of the positive sequence current, I_nIs the peak value of the negative-sequence current, theta_pIs the starting angle of the positive sequence current with respect to the positive sequence voltage, θ_nIs the starting angle of the negative sequence current relative to the negative sequence voltage;

the step S5 synthesizes the vector reference voltage according to the following formula

Another technical solution adopted in the embodiments of the present invention is a one-stop intelligent megawatt box system based on TE-SVM modulation, comprising:

the photovoltaic array is used for carrying out solar power generation and outputting electric energy;

the at least two inverter integrated megawatt boxes are respectively used for sequentially converging, reducing voltage and inverting the direct current output of the photovoltaic array and outputting three-phase alternating current;

the system comprises at least two SVM controllers, a power supply module and a power supply module, wherein the at least two SVM controllers are connected with inverters of all inverter integrated megawatt boxes in a one-to-one correspondence manner, and each SVM controller carries out inversion control on the inverter connected with the SVM controller based on TE-SVM modulation;

the power supply switching module is used for automatically switching all the inverter integrated megawatt boxes connected with the power supply switching module, so that only one inverter integrated megawatt box supplies power to the intelligent power grid at the same time;

the measurement and control power cabinet is used for performing master-slave competitive control on all the inverter integrated megawatt boxes according to the frequency, amplitude and phase of three-phase alternating current output by the inverters of all the inverter integrated megawatt boxes and the temperature detection result of each switch module of all the inverters, selecting the optimal one of all the inverter integrated megawatt boxes in real time by adopting a competitive ranking first standard, taking the currently selected optimal one as a master inverter, taking the rest inverter integrated megawatt boxes as slave inverters, and controlling a double-power-supply switching device correspondingly connected with the master inverter to work and perform automatic switching so as to enable the master inverter to supply power for an intelligent power grid;

the boost transformer is used for boosting the three-phase alternating current output by the double-power-supply switching device correspondingly connected with the main inverter integrated megawatt box and inputting the boosted three-phase alternating current into the smart grid;

wherein:

the power supply switching module is composed of at least one dual-power switching device, each dual-power switching device is correspondingly connected with two inverter integrated megawatt boxes, and each dual-power switching device automatically switches the two inverter integrated megawatt boxes connected with the dual-power switching device according to a control signal when working.

Further, the one-stop intelligent megawatt box system based on TE-SVM modulation further comprises an intelligent electric energy meter group arranged at a public point of an intelligent power grid;

each of the inverter integrated megawatt boxes comprises:

the junction box is used for merging the output of the photovoltaic array, and a first circuit breaker is arranged on each connecting line of the junction box and the photovoltaic array;

the DC/DC conversion module is used for carrying out voltage reduction conversion on the direct current output by the combiner box;

the direct current bus capacitor is used for filtering direct current output by the DC/DC conversion module and then using the filtered direct current as a direct current power supply;

the three-bridge arm inverter is used for performing DC/AC conversion on the direct current subjected to voltage reduction conversion and outputting three-phase alternating current;

the LCL filter is used for filtering the three-phase alternating current output by the three-bridge-arm inverter;

the output end of the SVM controller is connected with the input end of the measurement and control power cabinet through a paired cloud manager;

every the net side of the integrated megawatt case of dc-to-ac converter is provided with the second circuit breaker, and the three-phase line of second circuit breaker output divides two the tunnel, and wherein the three-phase line of one kind inserts the third circuit breaker, and the external observing and controlling power cabinet of third circuit breaker, another three-phase line of second circuit breaker output external dual supply auto-change over device who corresponds.

The invention has the beneficial effects that:

on the aspect of power grid interaction, a vector control coordinate transformation technology in a three-phase system is applied, low-pass and band-pass filtering characteristics are considered, extra filter design is saved, meanwhile, the phase and frequency of commercial power can be directly locked by a full-factor control closed-loop phase lock, tracking and matching of a power grid are perfectly realized, and a foundation is laid for replacing a traditional non-renewable energy power station from a photovoltaic power station. The positive sequence current and the negative sequence current are respectively controlled through a double-vector closed loop, and finally output is synthesized under a two-phase static coordinate system, so that when a power grid is sent to drop (even if the voltage drops to 0 voltage), expected active current or reactive current is injected into the power grid, actual current is regulated, the active power and reactive power of the power grid are regulated by an inverter, the photovoltaic power generation is ensured not to drop off the grid and continuously operates, low-voltage ride-through faults are automatically realized, meanwhile, a system can play a role in restraining the negative sequence voltage, and automatic compensation of the reactive power to the power grid and self-adaptive regulation of unbalanced voltage are realized; the positive sequence current and the negative sequence current are independently controlled, and low-order harmonic waves and high-order harmonic waves are effectively eliminated by adopting multiple times of coordinate transformation, P control, PI control and LPF + BPF filtering; the output of the phase-locked loop is controlled by five paths to control all factors such as voltage, current, phase, amplitude, power and the like from the input end to the phase-locked end; the method has the advantages that the TLS-ESPRIT frequency estimation is adopted to realize the resonant frequency offset adjustment of the LCL type inverter, the real-time performance and synchronization requirements of the frequency and amplitude phase friendly access to the intelligent power grid are improved, the inversion efficiency is improved, the power consumption is reduced, the real-time performance and synchronization rate of the one-station intelligent megawatt box system accessing to the intelligent power grid reach 93.5%, the conversion efficiency is more than or equal to 99.9%, the resonant frequency offset and the resonant peak under the unbalanced fault are eliminated, the causal switching loss is reduced by 90%, the output current harmonic THD is below 2.23, the voltage utilization rate of a direct current bus is improved by 5% compared with the most advanced prior art, the modulation ratio is large, the dynamic performance is good, the pulse level synchronization is realized, and the high-efficiency intelligent interactive operation with the intelligent power grid is realized. The problems that the reactive power supporting capability of a power grid is insufficient, the voltage stability is reduced and the fault voltage fluctuation is large after the existing photovoltaic new energy ratio is increased, the problems that the positive sequence current and the negative sequence current cannot be independently controlled through PI control, the low-order harmonic and the high-order harmonic are compensated, the response speed is low and the fault voltage fluctuation is large are effectively solved, the problems that all the voltage, the current, the phase, the amplitude, the power and other factors from the input end to the phase-locked end cannot be controlled through PLL phase locking of a controller of an existing photovoltaic power generation system, the problem that the resonant frequency of an LCL type inverter adopting a current open single-loop control strategy cannot be tracked through the controller of the existing photovoltaic power generation system, the problem that the power quality of the power grid is affected due to resonance peaks and harmonic waves existing at the resonant frequency of an LCL filter, the inversion efficiency of the existing inverter is low, and the problem that the controller of the existing photovoltaic power generation system cannot accurately control the frequency, the amplitude, the phase of the power grid, the power generation system and the power generation system, And estimating the phase to ensure that the photovoltaic inverter power generation grid-connected intelligent power grid can not meet the requirement of real-time synchronism.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a block diagram of a one-stop intelligent megawatt box system based on TE-SVM modulation according to an embodiment of the invention.

Fig. 2 is a specific structural diagram of a one-stop intelligent megawatt box system (a single inverter and a single controller) based on TE-SVM modulation according to an embodiment of the invention.

Fig. 3 is a specific structural diagram of an intelligent controller of a one-stop intelligent megawatt box system (single inverter and single controller) friendly access intelligent power grid based on TE-SVM modulation according to an embodiment of the invention.

Fig. 4 is a simplified positive and negative sequence circuit diagram of fig. 3.

FIG. 5 is a schematic diagram of the connection between the TE-SVM wave-generating principle and the voltage-sharing gate controller according to the embodiment of the invention.

FIG. 6 is a diagram illustrating the relationship between the spatial sector of the SVM module according to the embodiment of the present invention, the upper switch, the lower switch, and the vector frequency.

FIG. 7 is a graph of the RMS current waveform for the dq axis after TE-SVM modulation and synchronous rotation reference coordinate transformation, before PI modulation.

Fig. 8 is a network measurement harmonic diagram of a one-stop intelligent megawatt box friendly-accessed smart grid based on TE-SVM modulation and an SVM controller according to an embodiment of the present invention.

Fig. 9 is an inversion waveform diagram of the smart controller and the one-stop smart megawatt box based on TE-SVM modulation after being friendly-accessed to the smart grid according to the embodiment of the present invention.

Fig. 10 is a power generation operation diagram when the voltage of a PLL (PCC) drops to 0 after the smart controller and a one-stop smart megawatt box based on TE-SVM modulation are friendly connected to a smart grid, where (a) is a current amplitude diagram on an ac grid side of an inverter, (b) is a voltage amplitude diagram on a dc bus side of the inverter, (c) is a reactive current amplitude diagram provided to the PCC, and (d) is an active power amplitude diagram of the inverter.

Fig. 11 is a waveform diagram of LVRT waveforms of the photovoltaic grid-connected inverter when the intelligent controller and the one-stop intelligent megawatt box based on TE-SVM modulation are friendly-accessed to the smart grid and then symmetrical.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

As shown in fig. 1, the one-stop intelligent megawatt box system based on TE-SVM modulation according to the embodiment of the present invention includes:

the photovoltaic array is used for carrying out solar power generation and outputting electric energy;

the at least two inverter integrated megawatt boxes are respectively used for sequentially converging, reducing voltage and inverting the direct current output of the photovoltaic array and outputting three-phase alternating current;

the system comprises at least two SVM controllers, a power supply module and a power supply module, wherein the at least two SVM controllers are connected with inverters of all inverter integrated megawatt boxes in a one-to-one correspondence manner, and each SVM controller carries out inversion control on the inverter connected with the SVM controller based on TE-SVM modulation;

the power supply switching module is used for automatically switching all the inverter integrated megawatt boxes connected with the power supply switching module, so that only one inverter integrated megawatt box supplies power to the smart grid at the same time, wherein:

the power supply switching module consists of at least one double-power-supply switching device, each double-power-supply switching device is correspondingly connected with two inverter integrated megawatt boxes, and each double-power-supply switching device can automatically switch the two inverter integrated megawatt boxes connected with the double-power-supply switching device according to a control signal when working;

the measurement and control power cabinet is used for performing master-slave competitive control on all the inverter integrated megawatt boxes according to the frequency, amplitude and phase (namely, inversion effect) of three-phase alternating current output by the inverters of all the inverter integrated megawatt boxes and the temperature detection result (whether a switch tube of each switch module is intact) of each switch module of all the inverters, selecting the best one of all the inverter integrated megawatt boxes in real time by adopting a competitive ranking first standard, taking the currently selected best one as a master inverter, taking the rest inverter integrated megawatt boxes as slave inverters, controlling a dual-power switching device correspondingly connected with the master inverter to work and automatically switching the dual-power switching device to enable the master inverter to supply power for an intelligent power grid, and taking the slave inverters as the supplementary work of the master inverter only under the conditions of failure of the master inverter and the like, so that the problem of circulating current existing when a plurality of inverters supply power for the intelligent power grid at the same time can be solved, the problem of unstable and unbalanced working voltage and power of an unbalanced power source, a photovoltaic unhealthy battery and an unhealthy IGBT/IGCT power switch module is solved.

And the step-up transformer is used for stepping up the three-phase alternating current output by the double-power-supply switching device correspondingly connected with the main inverter integrated megawatt box and inputting the stepped-up three-phase alternating current into the smart grid.

Furthermore, each SVM controller based on TE-SVM modulation is connected with the control end of each switch module of the inverter correspondingly connected with the SVM controller through a voltage-sharing gate controller.

Further, each of the inverter integrated megawatt boxes includes:

the junction box is used for merging the output of the photovoltaic array, and a first circuit breaker is arranged on each connecting line of the junction box and the photovoltaic array;

the DC/DC conversion module is used for carrying out voltage reduction conversion on the direct current output by the combiner box;

the direct current bus capacitor is used for filtering direct current output by the DC/DC conversion module and then using the filtered direct current as a direct current power supply;

the three-bridge arm inverter is used for performing DC/AC conversion on the direct current subjected to voltage reduction conversion and outputting three-phase alternating current;

and the LCL filter is used for filtering the three-phase alternating current output by the three-bridge-arm inverter.

Furthermore, the output end of the SVM controller is connected with the input end of the measurement and control power cabinet through the paired cloud manager, so that various controlled parameter signals are transmitted to the measurement and control power cabinet, and bidirectional control is facilitated.

Furthermore, the step-up transformer has the functions of lightning protection, short circuit protection and grounding protection.

Furthermore, each the net side of the integrated megawatt case of dc-to-ac converter is provided with the second circuit breaker, and the three-phase line of second circuit breaker output divides two tunnel, and wherein three-phase line inserts the third circuit breaker all the way, and the external observing and controlling power cabinet of third circuit breaker, another external dual supply auto-change over device that corresponds of three-phase line of second circuit breaker output.

Further, the three-bridge arm inverter consists of 6 switches

The composition is as follows:

the switch

And switch

Form a first bridge arm and a switch

Is an upper switch of the first bridge arm

A lower switch of a first bridge arm;

the switch

And switch

Form a second arm, a switch

Upper switch for the second leg

A lower switch of a second bridge arm;

the switch

And switch

Form a third bridge arm and a switch

Is an upper switch of the first bridge arm

The lower switch of the third bridge arm.

Further, the switch

The IGBT/IGCT power switch module has the functions of undervoltage, overvoltage, voltage regulation and temperature detection.

The TE-SVM modulation-based one-stop intelligent megawatt box system of the embodiment of the invention also comprises:

intelligent ammeter group for the net side of two switching of power devices is voltage, electric current, active power, reactive power of public point department of smart power grids and measures, and intelligent ammeter group includes:

an active power meter PJP1 for measuring the actual active power at the input of the step-up transformer, the three-phase voltage (measured by a voltage sensor inside the active power meter PJP 1) and the three-phase current (measured by a current sensor inside the active power meter PJP 1);

and the reactive power meter PJQ1 is used for measuring the actual reactive power, three-phase voltage (measured by a voltage sensor in the reactive power meter PJQ 1) and three-phase current (measured by a current sensor in the reactive power meter PJQ 1) at the input end of the step-up transformer.

Furthermore, the output end of the measurement and control power cabinet is externally connected with an Ethernet communication port.

Further, the one-stop intelligent megawatt box system based on TE-SVM modulation further includes:

photovoltaic power plant intelligence cloud monitored control system for with ethernet communication, transfer information and control instruction overcome the tradition and patrol and examine artificially.

Example 2

The intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation in the embodiment of the present invention, that is, the SVM controller in embodiment 1, as shown in fig. 2 to 3, includes:

MPPT controller for tracking maximum power of DC/DC converter and outputting positive sequence DC reference voltage U_ref+ and DC reference current

A positive and negative sequence voltage decomposition module for detecting three-phase detection voltage V provided by the voltage sensor on the inverter network side_a、V_b、V_cDecomposed into positive sequence three-phase voltage V_a+、V_b+、V_c+ and negative sequence three-phase voltage V_a-、V_b-、V_c-；

Phase-locked loop for positive sequence three-phase voltage V according to input_a+、V_b+、V_cGiving a voltage starting angle theta and a frequency f;

a current correction module for correcting the current according to the three-phase standard current I'_a、I′_b、I′_cAnd inverter side inductance L of LCL filter_fThree-phase current I provided by current sensor_a、I_b、I_cFor C of LCL filter_fAnd R_fThree-phase average current I of current sensor output at assembly_aavg、I_bavg、I_cavgAnd correcting, wherein the current correction module comprises:

a first comparator of the current correction module for comparing C of the LCL filter_fAnd R_fThree-phase average current I provided by current sensor at assembly_aavg、I_bavg、I_cavgInverter side inductor L with LCL filter_fThree-phase current I provided by current sensor_a、I_b、I_cConverging and carrying out error comparison;

the proportional controller is used for carrying out proportional control on the output of the first comparator of the current correction module;

a second comparator of the current correction module for comparing the output of the comparative controller with the three-phase standard current I'_a、I′_b、I′_cError comparison is carried out, and the error between the real measured power and the calculated power of the intelligent electric meter set is converted into current adjustment and compensation;

the intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation further comprises:

a first 3S/2R conversion module for detecting the input three-phase current I_a、I_b、I_c(three-phase I (n +1) of FIG. 2) is subjected to 3S/2R conversion to output a positive-sequence actual active current I'_d+Positive sequence actual reactive current I'_q+Negative sequence actual active current I'_d-Negative sequence actual reactive current I'_q-；

A positive and negative sequence theory active reference current conversion module for converting the three-phase voltage V at the input grid-connected point_ga、V_gb、V_gcAnd standard three-phase voltage V'_a、V′_b、V′_cComparing, and PI controlling the comparison result to output theoretical active reference current

Positive sequence theory active reference current

Negative sequence theory active reference current

A positive and negative sequence theory reactive reference current conversion module for converting the input theoretical active reference current

And using formulas

Obtaining theoretical reactive reference current by inverse calculation

I_dref+For a first positive-sequence active reference current I_dref1+And a second positive-sequence active direct current reference current I_dref2+The larger of which, then, the DC reference current

And theoretical reactive reference current

Comparing and outputting positive sequence theoretical reactive reference current

Negative sequence theory reactive reference current

The two-phase positive sequence static voltage conversion module is used for converting the three-phase standard voltage V 'according to the input three-phase standard voltage'_a、V′_b、V′_cOutput of the current correction module, voltage initial angle theta, positive sequence three-phase voltage V_a+、V_b+、V_cd.C bus capacitor voltage U_busPositive sequence DC reference voltage U_ref+，Output current I of photovoltaic array_pvAverage current I output by the whole DC system of the photovoltaic array_pvavgPositive and negative sequence theory active reference current

Actual active current I 'of positive and negative sequences'_d+、I′_d-Converted to obtain two-phase positive sequence static voltage U_α+、U_βThe two-phase positive sequence static voltage conversion module comprises:

a positive sequence active and reactive current conversion module for converting the output result of the current correction module to obtain positive sequence theoretical active current I_d+ and positive-sequence theoretical reactive current I_qThe positive sequence active and reactive current conversion module comprises:

a second 3S/2R conversion module for performing 3S/2R coordinate conversion on the output result of the current correction module according to the input voltage initial angle theta and outputting a positive sequence active current I_d+ and positive sequence reactive current I_q+；

A first low pass filter LPF for correcting positive sequence active current I_d+ and positive sequence reactive current I_q+ low-pass filtering to eliminate high frequency part and maintain low frequency part;

a first band pass filter BPF for performing band pass filtering on the output of the first LPF, filtering noise outside the bandwidth, and outputting a clean positive-sequence active current I_d+ and positive sequence reactive current I_q+。

The two-phase positive sequence static voltage conversion module further comprises:

a positive sequence voltage conversion module for converting the input three-phase standard voltage V'_a、V′_b、V′_cCoordinate transformation and filtering are carried out to obtain positive sequence active voltage V_d+ and positive sequence reactive voltage V_qThe positive sequence voltage conversion module comprises:

a third 3S/2R conversion module for converting the input three-phase standard voltage V 'according to the input voltage starting angle theta'_a、V′_b、V′_cPerforming 3S/2R coordinate conversion and outputting positive sequence active voltage V_d+ and positive order noneWork voltage V_q+；

A second low pass filter LPF for correcting the positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+ low-pass filtering to eliminate high frequency part and maintain low frequency part;

a second band-pass filter BPF for performing band-pass filtering on the output voltage of the second low-pass filter LPF, filtering noise outside the bandwidth, and outputting a clean positive-sequence active voltage V_d+ and positive sequence reactive voltage V_q+。

The two-phase positive sequence static voltage conversion module further comprises:

a first positive-sequence active reference current conversion module for converting the input DC capacitor voltage U_busPositive sequence DC reference voltage U_ref+ performing coordinate transformation and PI control to obtain a first positive-sequence active reference current I_dref1+The first positive-sequence active reference current conversion module comprises:

positive sequence first comparator for DC capacitor voltage U_busAnd positive sequence DC reference voltage U_ref+ converging and comparing errors;

the fourth 3S/2R conversion module is used for performing 3S/2R coordinate conversion on the output result of the positive sequence first comparator and removing alternating current harmonic components in the direct current voltage;

a first PI controller for performing proportional-integral control on the output voltage of the fourth 3S/2R conversion module and outputting a first positive-sequence active direct-current reference current I_dref1+。

The two-phase positive sequence static voltage conversion module further comprises:

a second positive-sequence active reference current conversion module for outputting current I to the input photovoltaic array_pvAverage current I output by the whole direct current system of the photovoltaic array_pvavgComparing and PI controlling to obtain a second positive sequence active reference current I_dref2+The second positive-sequence active reference current conversion module comprises:

a positive sequence second comparator for the output current I of the photovoltaic array_pvAverage current I output by the whole direct current system of the photovoltaic array_pvavgConverging and carrying out error comparison;

a second PI controller for performing proportional-integral control on the output current of the positive sequence second comparator and outputting a second positive sequence active direct current reference current I_dref2+。

The two-phase positive sequence static voltage conversion module further comprises:

a positive sequence third comparator for the first positive sequence active DC reference current I_dref1+A second positive-sequence active direct-current reference current I_dref2+Positive sequence theoretical active current I_dPositive and negative sequence theory active reference current

And positive sequence actual active current I'_d+Converging and carrying out error comparison;

a third PI controller for performing proportional-integral control on the output current of the positive sequence third comparator and outputting a positive sequence active DC reference voltage U_d+；

A positive sequence fourth comparator for positive sequence reactive DC reference current I_qrefPositive and negative sequence theoretical reactive current I_qPositive and negative sequence theory reactive reference current

And positive sequence actual reactive current I'_q+Converging and carrying out error comparison;

a fourth PI controller for performing proportional-integral control on the output current of the positive sequence fourth comparator and outputting a positive sequence reactive DC reference voltage U_q+。

The two-phase positive sequence static voltage conversion module further comprises:

a positive sequence low voltage ride through control module for detecting whether voltage drop occurs at the grid-connected point, performing low voltage ride through control when the voltage drop occurs at the grid-connected point, controlling the input of the third PI controller and the fourth PI controller, and further controlling the generation of a positive sequence reactive DC reference voltage U at different moments_qInjecting reactive power into the power grid to enable the photovoltaic power generation to run without grid disconnection, wherein the positive sequence low voltage ride through control module comprises:

first low voltageA traversing module for passing through the three-phase voltage V_a、V_b、V_cDetecting whether voltage drop occurs at a grid-connected point, performing droop control, and outputting a droop voltage root-mean-square;

the first root mean square detection module is used for performing root mean square detection on the output of the first low-voltage ride-through module;

the reference power calculation module is used for calculating a fundamental wave active power instantaneous value and a fundamental wave reactive power instantaneous value, and correspondingly comparing the fundamental wave active power instantaneous value and the reactive power instantaneous value with standard active power and reactive power and actual power at an intelligent grid-connected point to obtain reference power P^*；

A third 2R/2S coordinate conversion module for correcting positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+ 2R/2S coordinate conversion to obtain negative sequence positive sequence two-phase static voltage U_a、U_B；

A first reference current calculation module for calculating a reference power P^*Two-phase static voltage U_a、U_BCalculating a positive sequence reference current

A first voltage and current calculation module for calculating a positive-sequence two-phase static voltage U_a、U_BAnd positive sequence reference current

Combination formula

And

calculating the voltage U of the grid-connected point_NAnd current I_total；

A first voltage drop determination module for determining a voltage drop DeltaU (n +1)) according to the result of the first RMS detection module when a low voltage ride through occurs, and combining the voltage drop DeltaU (n +1)) when a droop voltage RMS existsVoltage when voltage drop occurs on a grid point and low voltage ride through is carried out and grid-connected point voltage U_NComparing to obtain a voltage drop delta U; when no droop voltage root mean square exists, namely the voltage of the grid-connected point during low voltage ride through when the grid-connected point has voltage drop and the grid-connected point voltage U_NWhen the two phases are equal, the zero voltage ride through is shown to occur, and the three-phase average voltage V output by the inverter is adopted_iava、V_iavb、V_iavcAnd grid point voltage U_NComparing to obtain a voltage drop delta U;

the first low voltage ride through control module sets the positive sequence active power to 0 when low voltage ride through occurs, namely the positive sequence active current

I_d+、I’_d+Is 0, the power factor is set to be 1, and the positive sequence reactive reference current I under the condition of 1 power factor is output_qref+Performing low voltage ride through control according to the voltage drop delta U; then current flows

I_q+、I’_q+、I_qref+Comparing to obtain the maximum difference value delta i_q+Positive sequence reactive current Δ i_q+As initial suitable current I_rectiveInputting the positive sequence reactive voltage U generated by the fourth PI controller_q+Performing reactive compensation and adapting to the current I_rectiveAnd the total current I_totalGradually increases to 20%, voltage drop Δ U and voltage U_NThe ratio reaches 10 percent; positive sequence active current

I_d+、I’_d+、I_dref1+、I_dref2+Comparing to obtain the maximum difference value delta i_d+Will be positive sequence active current Δ i_d+Inputting the positive sequence active voltage U generated by a third PI controller_d+Positive sequence active current Δ i_d+And positive sequence reactive current Δ i_q+Synthesized as a suitable current I_rectivVoltage drop Δ U and voltage U_NThe ratio is gradually increased from 10% to 20% in positiveSequence active current Δ i_d+And positive sequence reactive current Δ i_q+Under continuous injection of (2), current ratio I_rective/I_totalGradually increasing from 20% to 45%, keeping the inverter in uninterrupted operation for 1s, and decreasing the power factor from 1 to delta U/U_NGradually increased to 50% for a current I_rectiveReach I from 0 within 4s_totalThe power factor is reduced to 0, and the positive sequence reactive current is delta i_q+And 0, normally injecting positive sequence active power into the power grid.

Under the normal condition of the voltage of the power grid, the photovoltaic grid-connected inverter works in a unit power factor state of 0, only active power is transmitted to the power grid, reactive power is 0, when the voltage drops (LVRT), the voltage of a grid-connected point is compared with the normal voltage (including standard voltage), and the active and reactive current commands are dynamically distributed through the outer ring of the voltage of the power grid and redistributed on the basis of the grid-connected control TE-SVM modulation strategy of the invention through the PI regulator, so that the distribution of the output power of the phase power grid of the inverter is achieved. The deeper the grid dip, the more reactive power the inverter provides to the grid. The method comprises the steps of judging whether voltage fluctuation is in a normal range or not through accurate detection of the voltage of the power grid, if not, enabling an inverter to work in a unit power factor grid-connected state, and otherwise, providing reactive power to the power grid.

The two-phase positive sequence static voltage conversion module further comprises:

first cross coupler ω L for aligning positive sequence reactive current I_d+ and positive sequence reactive current I_q+ cross-coupling to counteract reactive current I_d+ and positive sequence reactive current I_q+ coupling term, subjecting d-axis component to I_dAction of + q-axis component by I_q+ the positive sequence having a reactive current I_d+ input ω L_fThe product of (a) is subjected to coupling cancellation, and the d-axis coupling term is-omega Li_dAdding omega Lid and positive sequence active current I on d axis_dThe coupled phase-omega Lid on + is offset; positive sequence reactive current I_q+ input- ω L_fThe product of (a), the coupling cancellation is carried out, and the q-axis coupling term is omega Li_qOnly-omega Li is added to the q-axis_qAnd positive sequence reactive current I_q+ onCoupled phase of (ii) (. omega.Li)_qCarrying out offset;

a positive sequence fifth comparator for positive sequence active DC reference voltage U_dPositive and negative active voltage V_dThe active outputs of the + and the +/-omega L of the first cross coupler are converged to carry out error comparison;

a positive sequence sixth comparator for positive sequence reactive DC reference voltage U_qPositive and negative sequence reactive voltage V_q+ and the reactive output of the first cross coupler +/-omega L are converged, and error comparison is carried out;

a first 2R/2S coordinate transformation module for performing 2R/2S coordinate transformation on the outputs of the positive sequence fifth comparator and the positive sequence sixth comparator according to the input voltage initial angle theta to obtain a two-phase positive sequence static voltage U_α+、U_β+。

The intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation of the embodiment of the invention also comprises:

the two-phase negative sequence static voltage conversion module is used for converting the three-phase standard voltage V 'according to the input three-phase standard voltage'_a、V′_b、V′_cOutput of the current correction module, voltage initial angle theta, negative sequence three-phase voltage V_a-、V_b-、V_cPositive sequence reactive DC reference current I_qrefPositive and negative sequence theoretical reactive reference current

Actual reactive current I 'of positive and negative sequence'_q+、I′_q-Converted to obtain two-phase negative sequence static voltage U_α-、U_βThe two-phase negative sequence static voltage conversion module includes:

a voltage initial phase angle determining module for determining the three-phase voltage V according to the input voltage initial angle theta and the negative sequence three-phase voltage V_a-、V_b-、V_c-, converting to obtain a voltage initial phase angle

The voltage initial phase angle determination module comprises:

a fifth 3S/2R conversion module forAccording to the input voltage initial angle theta, the negative sequence three-phase voltage V is applied to the input_a-、V_b-、V_c-carrying out 3S/2R coordinate conversion to obtain an active voltage V_dAnd a reactive voltage V_q；

A module for calculating an initial phase angle according to the active voltage V_dAnd a reactive voltage V_qCalculating to obtain the initial phase angle of voltage

The two-phase negative-sequence static voltage conversion module further comprises:

a negative sequence active and reactive current conversion module for converting the output result of the current correction module to obtain the negative sequence theoretical active current I_dAnd negative sequence theoretical reactive current I_qNegative sequence active and reactive current conversion module comprising:

a sixth 3S/2R transformation module for transforming the voltage according to the voltage initial angle theta and the voltage initial phase angle

3S/2R coordinate conversion is carried out on the output current of the current correction module, and negative-sequence active current I is output_d-and a negative sequence reactive current I_q-；

A third low pass filter LPF for the negative sequence active current I_d-and a negative sequence reactive current I_q-low-pass filtering to remove the high frequency part and to retain the low frequency part;

a third band-pass filter BPF for performing band-pass filtering on the output current of the third low-pass filter LPF, filtering noise outside the bandwidth and outputting a clean negative-sequence active current I_d-and a negative sequence reactive current I_q-。

The two-phase negative-sequence static voltage conversion module further comprises:

a negative sequence voltage conversion module for converting the input three-phase standard voltage V'_a、V′_b、V′_cConverting to obtain negative-sequence active voltage V_d-and positive sequence reactive voltage V_q-the negative sequence voltage conversion module comprises:

a seventh 3S/2R transformation module for transforming the voltage according to the voltage initial angle theta and the voltage initial phase angle

To the input three-phase standard voltage V'_a、V′_b、V′_c3S/2R coordinate conversion is carried out, and negative sequence active voltage V is output_d-and negative sequence reactive voltage V_q-；

A fourth low pass filter LPF for applying a negative sequence active voltage V_d-and negative sequence reactive voltage V_q-low-pass filtering to remove the high frequency part and to retain the low frequency part;

a fourth band-pass filter BPF for band-pass filtering the output voltage of the fourth LPF, filtering out noise outside the bandwidth and outputting clean negative-sequence active voltage V_d-and positive sequence reactive voltage V_q-。

The two-phase negative-sequence static voltage conversion module further comprises:

a fifth PI controller for negative-sequence active current I_dNegative sequence actual active current I'_d-And negative sequence theory active reference current

PI control is carried out, and negative sequence active direct current reference voltage U is output_d-；

Negative sequence first comparator for negative sequence reactive current I_qNegative sequence reactive DC reference current I_qrefNegative sequence actual reactive current I'_q-And negative sequence theory reactive reference current

Converging and comparing errors;

a sixth PI controller for PI controlling the output current of the negative sequence first comparator and outputting a negative sequence reactive DC reference voltage U_q-；

The negative sequence low voltage ride through control module is used for detecting whether voltage drop occurs at the grid-connected point or not and carrying out low voltage ride through when the voltage drop occurs at the grid-connected pointControlling the input of the fifth PI controller and the sixth PI controller to generate negative sequence active direct current reference voltage U at different moments_qInjecting reactive power into the grid so that the photovoltaic power generation does not run off the grid, wherein the negative sequence low voltage ride through control module comprises:

a second low voltage ride through module for outputting a negative sequence three-phase voltage V according to the input_a-、V_b-、V_cDetecting whether voltage drop occurs at a grid-connected point, performing droop control, and outputting a droop voltage root mean square;

the second root mean square detection module is used for performing root mean square detection on the output of the second low-voltage ride through module;

a third-order negative-sequence maximum current calculating module for calculating the positive-sequence reactive DC reference current I_qref+, maximum current I_maxInitial phase angle of sum voltage

Calculating the third-order negative-sequence maximum current I_qmax-；

A fourth 2R/2S coordinate conversion module for converting the negative-sequence active voltage V_d-and negative sequence reactive voltage V_q-2R/2S coordinate transformation to obtain a negative-sequence two-phase rest voltage U_a、U_B；

A second reference current calculation module for calculating a reference power P^*Negative sequence two-phase static voltage U_a、U_BCalculating a negative sequence reference current

A second voltage and current calculation module for calculating two-phase static voltage U according to negative sequence_a、U_BAnd a negative sequence reference current

Combination formula

And

calculating the voltage U of the grid-connected point_NAnd current I_total；

The second voltage drop determining module is used for determining the voltage drop delta U according to the result of the second root mean square detection module when low voltage ride through occurs, and determining the voltage when the low voltage ride through is performed on the voltage drop of the grid-connected point and the grid-connected point voltage U when the droop voltage root mean square exists_NComparing to obtain a voltage drop delta U; when no droop voltage root mean square exists, namely the voltage of the grid-connected point during low voltage ride through when the grid-connected point has voltage drop and the grid-connected point voltage U_NWhen the two phases are equal, the zero voltage ride through is shown to occur, and the three-phase average voltage V output by the inverter is adopted_iava、V_iavb、V_iavcAnd grid point voltage U_NComparing to obtain a voltage drop delta U;

the second low voltage ride through control module performs low voltage ride through control according to the voltage drop delta U when low voltage ride through occurs, and sets the negative sequence reactive power to 0, namely negative sequence reactive current

I_q-、I’_q-Set to 0; setting the power factor to be 1, and performing low voltage ride through control according to the voltage drop delta U; then the

I_d-、I’_d-The comparison (which is not shown in fig. 3) yields the maximum difference Δ i_d-Negative sequence active current Δ i_d-As initial suitable current I_rectiveInputting the negative sequence active voltage U into a fifth PI controller_d-Is adapted to the current I_rectivAnd the total current I_totalGradually rises to 20%, and the voltage drop delta U and the voltage U are_NThe ratio of (A) to (B) reaches 10% and starts to rise; negative sequence reactive current

I_q-、I’_q-、I_qref-Comparing to obtain the maximum difference value delta i_q-Negative sequence reactive current Δ i_q-Inputting the voltage into a sixth PI controller which generates a negative sequence reactive voltage U_q-Negative sequence reactive current Δ i_q-And negative sequence active current delta i_d-Synthesized as a suitable current I_rectivVoltage drop Δ U and voltage U_NThe ratio is gradually increased from 10% to 20%, and the reactive current delta i in the negative sequence_q-And negative sequence active current delta i_d-Under continuous injection of (2), current ratio I_rective/I_totalGradually increasing from 20% to 45%, keeping the inverter in uninterrupted operation for 1s, and decreasing the power factor from 1 to delta U/U_NGradually increased to 50% and adapted to the current I_rectiveReach I from 0 within 4s_totalAnd when the power factor is reduced to 0, the negative sequence active current injects negative sequence active power to the power grid normally, and the negative sequence reactive voltage of the negative sequence reactive power is limited.

The two-phase negative sequence static voltage conversion module further comprises:

a second cross-coupler ω L for the negative-sequence reactive current I_dWith negative-sequence reactive current I_q-cross-coupling to cancel the negative sequence reactive current I_dWith negative-sequence reactive current I_qCoupling term of (d) by the d-axis component_dThe q-axis component is given by_q-an effect of; the negative sequence has reactive current I_d-input- ω L_fThe product of (a) and (b) is coupled to cancel out, the d-axis coupling term is ω Li_dAdding-omega Lid and negative sequence active current I on d axis_dThe coupling phase ω Lid on the-cancels; applying negative sequence reactive current I_q-input ω L_fThe product of (a) is coupled and cancelled, and the q-axis coupling term is-omega Li_qAdding ω Li to the q-axis_qAnd negative sequence reactive current I_qCoupled phase at- ω Li_qCarrying out offset;

negative sequence second comparator for negative sequence active DC reference voltage U_dNegative-sequence active voltage V_dError ratio by convergence of the active outputs of the second cross-couplers ± ω LComparing;

a negative sequence third comparator for negative sequence reactive DC reference voltage U_qNegative sequence reactive voltage V_q-and reactive outputs of the second cross-couplers ± ω L converge, making an error comparison;

a second 2R/2S coordinate transformation module for transforming the initial voltage angle theta and the initial voltage phase angle theta

2R/2S coordinate transformation is carried out on the output of the negative sequence second comparator and the negative sequence third comparator to obtain two-phase negative sequence static voltage U_α-、U_β-。

In order to evaluate and analyze the topological simplification of the intelligent controller of the embodiment of the invention, the intelligent controller is divided into a positive sequence circuit and a negative sequence circuit, and as shown in fig. 4, the positive sequence circuit and the negative sequence circuit are respectively composed of INV, Powergrid, an active table and a reactive table.

The intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation realizes low voltage ride through with more excellent current tracking performance when a power grid is disturbed or has a fault drop, and transmits positive sequence reactive power and negative sequence active power to the power grid, supports the voltage of a grid-connected point and is beneficial to the safety and stability of the system.

The intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation of the embodiment of the invention also comprises:

the TE-SVM wave-transmitting module is used for estimating the frequency of the smart power grid based on the TLS-ESPRIT algorithm and utilizing the two-phase positive sequence static voltage U_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_βSynthesizing three-phase reference voltage, taking the power grid frequency output by the phase-locked loop or the smart power grid frequency solved by the TLS-ESPRIT algorithm as wave-sending frequency, sending waves by combining the synthesized three-phase reference voltage, and controlling inversion of an inverter bridge, wherein the TE-SVM wave-sending module comprises:

the TLS-ESPRIT frequency estimation module is used for estimating the frequency of the smart grid based on a TLS-ESPRIT (rotation invariant subspace frequency search) algorithm;

the SVM wave-transmitting module is used for transmitting the two-phase positive sequence static voltageU_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_β-, synthesizing three-phase reference voltages

Wave sending is carried out according to the power grid frequency output by the phase-locked loop or the frequency of the intelligent power grid estimated by the TLS-ESPRIT frequency estimation module;

and the gate controller is used for controlling each switch module of the inverter to be switched on or switched off according to the vector signal sent by the SVM wave sending module.

After the SVM wave-generating module outputs to the outer ring control, the inner ring control and the gate control, the control electrode of the power switch tube of the inverter switch module is modulated according to SVPWM, as shown in figure 2, the voltage initial angle theta output by the phase-locked loop is input into the voltage and current inner ring controller, the temperature sensor detection control of the photovoltaic array and the intelligent module switch and the direct current conversion voltage U_dcThe power is input into an external power controller and the voltage U of a direct current bus capacitor after passing through an AD converter_busInputting the voltage into a gate pole controller after AD, and outputting three-phase voltage u by the gate pole controller_c、u_b、u_aSum frequency, three phase voltage u_c、u_b、u_aAnd frequency input SVPWM, wherein each phase of SVPWM controls two switch modules on one bridge arm of the inverter to work.

Specifically, as shown in fig. 5, the vector output end of the SVM wave generation module is connected to a gate controller, the gate controller may adopt a voltage-sharing gate controller, the output 6 vectors are correspondingly connected to the driving ends of 6 gates of the voltage-sharing gate controller, and the driving wires are sequentially connected to the gates of the corresponding power switches of the inverter; output current I is output between the drain electrode of the upper bridge arm power switching tube, the source electrode of the lower bridge arm power switching tube and the drain electrode of the lower bridge arm power switching tube of each bridge arm_A、I_B、I_COutput current I_A、I_B、I_CAccessing a corresponding isolation circuit through a corresponding A/D, wherein the corresponding isolation circuit is connected with a voltage-sharing gate electrode controller; between the source of the upper bridge arm power switch tube and the drain of the lower bridge arm power switch tube of the three bridge armsIs connected with corresponding equalizing voltage U_AE、U_BE、U_CEEqualizing voltage U_AE、U_BE、U_CEAnd the three-phase power switching tube is respectively connected with corresponding isolating circuits through A/D, and the corresponding isolating circuits are connected with a voltage-sharing gate electrode controller to averagely balance the voltage of the three-phase power switching tube.

Example 3

A control method for friendly access of a one-stop intelligent megawatt box to an intelligent power grid based on TE-SVM modulation is implemented by adopting an intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation in embodiment 2, and comprises the following steps:

step S1, receiving actual active power and reactive power at the intelligent grid-connected point, and detecting voltage V by three phases_a、V_b、V_cThree-phase voltage V at grid-connected point_ga、V_gb、V_gcThree-phase average voltage V_iava、V_iavb、V_iavcThree-phase current I_a、I_b、I_cThree-phase average current I_aavg、I_bavg、I_cavgDC bus capacitor voltage U_busOutput current I of the photovoltaic array_pvAverage current I_pvavgAnd tracking the maximum power of the DC/DC converter by adopting an MPPT controller to output a positive sequence direct current reference voltage U_ref+ and DC reference current

Step S2, calculating standard active power and reactive power, and an active power instantaneous value and a reactive power instantaneous value at an intelligent grid connection point;

step S3, judging whether the actual active power and reactive power at the intelligent grid-connected point are corresponding to the calculated active power instantaneous value and reactive power instantaneous value at the intelligent grid-connected point and the standard active power and reactive power; judging whether the frequency output by the phase-locked loop is within the range of 50 +/-0.1 Hz;

s4, when the actual active power and the reactive power at the intelligent grid-connected point are correspondingly consistent with the calculated active power instantaneous value and the calculated reactive power instantaneous value at the intelligent grid-connected point and the frequency output by the phase-locked loop is within the range of 50 +/-0.1 Hz, taking the frequency output by the phase-locked loop as the wave-transmitting frequency of the SVM wave-transmitting module; otherwise, carrying out frequency search of the smart power grid by using the TLS-ESPRIT frequency estimation module, and taking the searched frequency as the wave transmitting frequency of the SVM wave transmitting module;

step S5, calculating three-phase standard voltage V 'according to the voltage and current signals received in the step S1'_a、V′_b、V′_cThree-phase Standard Current I'_a、I′_b、I′_cStandard active power and reactive power, and an active power instantaneous value and a reactive power instantaneous value at an intelligent grid-connected point, and a two-phase positive-sequence static voltage U is obtained by using a two-phase positive-sequence static voltage conversion module and a two-phase negative-sequence static voltage conversion module_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_β-; utilizing an SVM wave-transmitting module to transmit a voltage U according to a two-phase positive sequence_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_βSynthesizing a reference voltage, then performing SVM wave generation based on the wave generation frequency and the reference voltage, and controlling each switching module of the inverter to be turned on or off by adopting SVPWM modulation according to a vector signal generated by the SVM wave generation by the voltage-sharing gate controller, which specifically operates as follows:

as shown in FIG. 5, the 6 IGBT/IGCT switch modules of the inverter are distributed in the SVM corresponding to 6 sectors, and the 6 sectors are defined by voltage vectors V₁、V₂、V₃、V₄、V₅、V₆、V₀、V₇As a boundary value, where V₀、V₇Is the origin; the starting boundary time of each sector is T₁The time of the termination boundary of adjacent 60 degrees is T₂，T₁、T₂And T₀Is a synthetic reference voltage

The driving time of the decomposition vector of (1). T is₀And T₇Is the time of virtual time for replacing the B phase and the C phase, repeating wave-emitting time with the A phase, and repeating the actual B phase and the C phase with the A phaseThe complex section only runs along a time period to achieve synchronization, the repeated wave emission of the power tubes is eliminated, only 1 power tube emits wave to generate power every time, and the invalid power consumption is reduced. By voltage vector V along 6 sectors₁、V₂、V₃、V₄、V₅、V₆、V₀、V₇A vector rotating counterclockwise by 360 degrees for 1 cycle, corresponding to 6 vector switching frequency signals S₁、S₂、S₃、S₄、S₅、S₆Driving 6 power switch modules.

Corresponding vector switch S in SVM₁、S₂、S₃、S₄、S₅、S₆The switching frequency, switching state, and space vector of (a) are defined as follows, and are specifically shown in table 1:

S₁: frequency:

switching state: 100, respectively; vector: 0 degree; the equation value: (2/3, 0); vector voltage V₁(ii) a Reference voltage:

S₂: frequency:

switching state: 110; vector: 60 degrees; the equation value:

vector voltage V₂(ii) a Reference voltage:

S₃: frequency:

switching state: 010; vector: 120 degrees; the equation value:

vector voltage V₃(ii) a Reference voltage:

S₄: frequency:

switching state: 011; vector: 180 degrees; the equation value: (-2/3, 0); vector voltage V₄(ii) a Reference voltage:

S₅: frequency:

switching state: 001; vector: 240 degrees; the equation value:

vector voltage V₅(ii) a Reference voltage:

S₆: frequency:

switching state: 101, a first electrode and a second electrode; vector: 300 degrees; the equation value:

vector voltage V₆(ii) a Reference voltage:

s7: frequency:

switching state: 111; vector: 0 degree;

s0: frequency:

switching state: 000; vector: 0 deg.

TABLE 2 vector switch, space vector, switch state, line voltage correspondence definitions

Corresponding vector switch S in SVM₁、S₂、S₃、S₄、S₅、S₆And wave frequency

As shown in fig. 6, the frequency ripple of the 6 sectors of the space vector SVM driving the upper and lower switches is defined as follows:

1 sector:

the wave-making time of the upper switch S1 is S₁＝T₁+T₂+T₀/2, the wave-emitting time of the upper switch S3 is S₃＝T₂+T₀/2, the wave-emitting time of the upper switch S5 is S₅＝T₀/2, the wave generation time of the lower switch S4 is S₄＝T₀/2, the wave generation time of the lower switch S6 is S₆＝T₁+T₀/2, the wave generation time of the lower switch S2 is S₂＝T₁+T₂+T₀/2。

2 sectors:

the wave-making time of the upper switch S1 is S₁＝T₁+T₀/2, the wave-emitting time of the upper switch S3 is S₃＝T₁+T₂+T₀/2, the wave-emitting time of the upper switch S5 is S₅＝T₀/2, the wave generation time of the lower switch S4 is S₄＝T₂+T₀/2, the wave generation time of the lower switch S6 is S₆＝T₀/2, the wave generation time of the lower switch S2 is S₂＝T₁+T₂+T₀/2。

3 sectors:

upper switch S1Wave generation time of S₁＝T₀/2, the wave-emitting time of the upper switch S3 is S₃＝T₁+T₂+T₀/2, the wave-emitting time of the upper switch S5 is S₅＝T₂+T₀/2, the wave generation time of the lower switch S4 is S₄＝T₁+T₂+T₀/2, the wave generation time of the lower switch S6 is S₆＝T₀/2, the wave generation time of the lower switch S2 is S₂＝T₁+T₀/2。

4 sectors:

the wave-making time of the upper switch S1 is S₁＝T₀/2, the wave-emitting time of the upper switch S3 is S₃＝T₁+T₀/2, the wave-emitting time of the upper switch S5 is S₅＝T₁+T₂+T₀/2, the wave generation time of the lower switch S4 is S₄＝T₁+T₂+T₀/2, the wave generation time of the lower switch S6 is S₆＝T₂+T₀/2, the wave generation time of the lower switch S2 is S₂＝T₀/2。

5 sectors:

the wave-sending time of the upper switch S1 is S₁＝T₂+T₀/2, the wave-emitting time of the upper switch S3 is S₃＝T₀/2, the wave-emitting time of the upper switch S5 is S₅＝T₁+T₂+T₀The wave-making time of the switch S4 is S₄＝T₁+T₀/2, the wave generation time of the lower switch S6 is S₆＝T₁+T₂+T₀/2, the wave generation time of the lower switch S2 is S₂＝T₀/2。

6 sectors:

the wave-making time of the upper switch S1 is S₁＝T₁+T₂+T₀/2, the wave-emitting time of the upper switch S3 is S₃＝T₀/2, the wave-emitting time of the upper switch S5 is S₅＝T₁+T₀/2, the wave generation time of the lower switch S4 is S₄＝T₀/2, the wave generation time of the lower switch S6 is S₆＝T₁+T₂+T₀/2, the wave generation time of the lower switch S2 is S₂＝T₂+T₀/2。

Space vector SVM drives the frequency S of the upper and lower switches according to the vector state, 6 sectors₁、S₃、S₅、S₄、S₆、S₂Wave definition, driving the upper switch S of the inverter by means of a voltage-sharing gate controller_1·,S_3·,S_5·Control gate (gate G) in turn defining S as a vector switch₁→S₃→S₅The wave generating work is turned on, and the switch S is turned on_1·The current IA is respectively input into the corresponding A/D through the emitter and the collector and returns to the voltage-sharing gate controller through the isolating circuit to realize the balanced control inversion of the voltage, and the lower switch S_4·Closing the device to be out of work; upper switch S_3·The current IB is respectively input into the corresponding A/D through the emitter and the collector and returns to the voltage-sharing gate controller through the isolating circuit to realize the balanced control inversion of the voltage, and the lower switch S_6·Closing the device to be out of work; upper switch S_5·The current IC respectively inputs the corresponding A/D through the emitter and the collector and returns to the voltage-sharing gate controller through the isolation circuit to realize the balanced control inversion of the voltage, and the lower switch S_2·Closing the device to be out of work; otherwise, when the switch S is turned off_4·→S_6·→S_2·Operating according to the wave-emitting time and sequence of sector 1, the upper switch S_1·→S_3·→S_5·The shutdown is not operative. Sector 2, sector 3, sector 4, sector 5, sector 6, work in sequence according to the above process in the order of 1 sector to 6 sectors.

TE-SVM modulation-based RMS current I of intelligent controller of one-stop megawatt box system accessed to intelligent power grid_dRMS、I_qRMSThe waveform of the double-vector current is shown in figure 7, which illustrates that the precision of the frequency, the phase and the amplitude of the double-vector current control meets the requirements of synchronization and real time and provides necessary conditions for double intelligent controllers. The TE-SVM modulation-based one-stop intelligent megawatt box friendly-access intelligent power grid intelligent controller has good performance of controlling dq axis current in a synchronous rotation (dq) coordinate system in balanced load and unbalanced load.

The harmonic wave of the grid measurement is shown in a figure 8, the waveform of the three-phase inversion is shown in a figure 9, and figures 8-9 illustrate that the intelligent controller which is friendly to be connected into the intelligent power grid by adopting the one-stop intelligent megawatt box based on the TE-SVM modulation is adopted, the synchronism and the real-time property of the output three-phase current, the three-phase voltage, the line voltage and the line current of the inverter all meet the real-time synchronism requirement of the intelligent power grid, the intelligent controller has high-quality harmonic component processing capacity, the harmonic wave THD of the grid measurement reaches 2.23 percent, the intelligent controller which is friendly to be connected into the intelligent power grid by the one-stop intelligent megawatt box based on the TE-SVM modulation is obtained, unbalanced positive sequence and negative sequence components can be independently processed, and the intelligent controller has excellent processing capacity for low higher harmonic waves.

The intelligent controller of the one-stop intelligent megawatt box friendly access intelligent power grid based on TE-SVM modulation enables the real-time performance and the synchronization rate of the one-stop intelligent megawatt box system access intelligent power grid to reach 93.5%, the conversion efficiency is more than or equal to 99.9%, resonance frequency deviation and resonance peak under unbalanced fault are eliminated, the no-reason switching loss is reduced by 90%, the output current harmonic THD is below 2.23, the direct current bus voltage utilization rate is improved by 5% compared with the current bus voltage utilization rate which is advanced by 90% in the world, the modulation ratio is large, the dynamic performance is good, and the pulse level synchronization is realized by referring to table 2; and the intelligent interactive operation with the intelligent power grid with high efficiency is realized.

TABLE 2 comparative information (2020-8-17)

Index name	Index of the invention	German SMA/SUNBOY	The index is improved
				Conversion rate	＞99.9％	97.5％	2.4％
Output harmonic	＜2.23％	＜4％	1.77％
				Power density	＞4.5w/in3	＞1.7w/in3	2.8w/in3
Weight volume	12∶31∶03	217.38	38.32
				Real-time synchronicity	93.5％	83％	13.5％
Without causing loss	6％	11.4％	The reduction is 90 percent
				Utilization rate of DC bus	95％	90％	5％

As shown in fig. 10, when the common point voltage of the PLL phase lock drops to 0 and the unbalanced fault duration is 140ms, the operation effect of the intelligent controller according to the embodiment of the present invention is as shown in fig. 10, which can reduce the ac side overvoltage and the dc bus overvoltage of the network inverter, and the voltage peak value and the fluctuation of the active power are small, and when the grid voltage drops to 0 voltage, the present invention injects 1100A reactive current into the grid, so that the inverter injects 100% of reactive current into the grid.

Fig. 11 shows LVRT waveforms of the photovoltaic grid-connected inverter when the grid voltage is symmetric, where the grid voltage drop depth is 15%, the fault duration is 350ms, and according to the provision of the grid-connected rule, the positive sequence reactive current instruction output by the photovoltaic system at the fault duration stage should be: expressed by a per unit value, the upper limit value is 1 Pu; the reactive current compensation coefficient is determined according to the permeability of the photovoltaic system to the power grid, 2 is usually selected, and the reactive current instruction is equal to the reactive current compensation coefficient multiplied by the voltage drop depth ratio of the power grid; the output reactive current instruction of the grid-connected inverter at the fault continuation stage can be obtained to be 0.3 pu; according to the embodiment of the invention, the power factor is 1 as the maximum factor, the limit of an active current instruction is 0.7pu is obtained by the limit of the rated capacity of the system, the voltage of a direct current bus is increased during the fault period, the LVRT response speed of the photovoltaic grid-connected inverter is high, the uninterrupted operation is carried out in 1 second, the reactive compensation is completed in 4 seconds, and active power is injected into a power grid.

The method comprises the following application scenarios of a one-stop intelligent megawatt box friendly access intelligent controller of the intelligent power grid based on TE-SVM modulation:

no reactive power is injected when the current control system, namely sag (sag is droop control);

in the current control system, when the active power of the sag is 0, injecting reactive power;

full current feedback, and positive sequence voltage feedforward and negative sequence voltage feedforward are carried out simultaneously, and the feedback is called VCCF;

double-vector control, negative sequence current is not controlled, and negative sequence voltage is not fed forward, and only positive sequence control is carried out, namely DVCC 1;

double vector control, negative sequence current control to 0, and negative sequence voltage feed forward, called DVCC 2;

the dual vector control has a current limiting function (active power limit) called DVCCL.

In the step S5, the three-phase standard voltage V'_a、V′_b、V′_cCalculating according to the formula (1):

wherein, V_pIs the positive sequence voltage peak, V_nIs the peak value of the negative-sequence voltage,

is the initial phase angle of the positive sequence voltage,

is the initial phase angle of the negative sequence voltage; ω is the fundamental voltage angular frequency;

three-phase standard current I'_a、I′_b、I′_cCalculating according to the formula (2):

wherein, I_pIs the peak value of the positive sequence current, I_nIs the peak value of the negative-sequence current, theta_pIs the starting angle, theta, of the positive and negative sequence currents relative to the positive sequence voltage_nIs the starting angle of the negative sequence voltage relative to the negative sequence voltage;

in step S5, positive and negative sequence impedances are calculated when the first low voltage ride through module and the second low voltage ride through module perform droop control, wherein:

positive sequence impedance Z_P(S) calculating according to the formula (3):

wherein, K_mIs the inverter voltage gain, V_dcIs the voltage difference between two ends of the DC bus capacitor, H_i(s-j2πf₁) For current-loop PI controllers, i.e. first PI controlClosed loop transfer function of the system, T_PLL(s-j2πf₁) Is the closed loop transfer function of the phase locked loop, f₁At fundamental frequency, K_dAs a gain of a weighting function, K_fAs integral proportional parameter, G_i(s) is the equivalent transfer function of the current filter consisting of the first low-pass filter LPF and the first band-pass filter BPF, L_fInductance value of inverter-side inductor of LCL filter, c₁Is a DC bus capacitance value; g_v(s) is the equivalent transfer function of the voltage filter consisting of the second low pass filter LPF and the second band pass filter BPF, s denotes the complex frequency domain,

is the initial phase angle of the fundamental current, I₁Is the peak value of the fundamental current, V₁Is the peak value of the grid voltage;

negative sequence impedance Z_n(S) calculating according to the formula (4):

wherein H_i(s+j2πf₁) Is the closed loop transfer function of the current inner loop PI controller, i.e. the first PI controller, G_i(s) is the equivalent transfer function of the current filter consisting of the first low-pass filter LPF and the first band-pass filter BPF, G_v(s) is the equivalent transfer function of the voltage filter consisting of the fourth low pass filter LPF and the fourth band pass filter BPF;

according to a constant amplitude Clark transformation formula, the expression of the voltage and the current under a two-phase rotating coordinate system can be obtained as follows:

wherein, V_dIs divided into twoD-axis voltage, V, in a phase rotation coordinate system_qIs the q-axis voltage, I, in a two-phase rotating coordinate system_dIs d-axis current in a two-phase rotating coordinate system, I_qQ-axis current under a two-phase rotating coordinate system;

the standard active power and the standard reactive power are calculated according to formulas (7) to (8):

wherein P (t) is standard active power, Q (t) is standard reactive power, V_α、V_βFor voltages in a stationary reference (α β) coordinate system, I_α、I_βFor currents in a stationary reference (α β) coordinate system, θ₁、θ₂Respectively, the initial phase angles of the voltages in the stationary reference (alpha beta) coordinate system.

In a three-phase symmetrical system, dq is direct-current components in a stable state of fundamental waves, and a d axis is superposed with a voltage vector of a power grid, so that active power and reactive power can be independently controlled, and if 2-order harmonic waves are filtered, the expressions of an active power instantaneous value and a reactive power instantaneous value of the fundamental waves can be seen as follows:

P₀(t) is the instantaneous value of the active power of the fundamental wave, Q₀And (t) is a fundamental wave reactive power instantaneous value, and the active power instantaneous value and the reactive power instantaneous value at the intelligent grid-connected point are calculated according to the formula (9).

Initial phase angle of dq conversion voltage

Calculated according to equation (10):

third order negative maximum current I_qmax-Calculated according to equation (11):

wherein, I_maxIs the maximum current, k is a positive integer of coefficient, α ═ ω t;

the negative sequence reactive reference current I_qref-calculated according to the following formula:

the SVM synthesizes a vector reference voltage according to formula (13)

Example 4

The TLS-ESPRIT frequency estimation search algorithm flow is as follows:

the sampling real signal expression of the power grid is as follows:

wherein x (n) is the real grid sampling signal of the nth sampling point, p is the harmonic component of the real grid sampling signal, and alpha_kSampling the amplitude, omega, of the kth and inter-harmonic components of a real signal for a power grid_kThe angular frequency of the kth harmonic and inter-harmonic components of the real signal are sampled for the grid,

for mining of electric networkAnd (2) the phase of the k-th harmonic and inter-harmonic components of the sample real signal, n is a sampling point, and W (n) is the noise component of the power grid sampling real signal of the nth sampling point.

Solving the power grid frequency based on TLS-ESPRIT, and transforming a formula (14) into a sampling complex signal through Euler transformation:

wherein, alpha'_kIs the amplitude, ω 'of the kth harmonic and inter-harmonic components of the sampled complex signal'_kTo sample the angular frequencies of the kth harmonic and inter-harmonic components of the complex signal,

is the phase of the kth harmonic and inter-harmonic components of the sampled complex signal;

when k is more than or equal to 1 and less than or equal to p,

ω′_k＝ω_k,

when p is<When k is less than or equal to 2p,

ω′_k＝-ω_k-p,

α_k-psampling the amplitude, omega, of the k-p harmonic and inter-harmonic components of the real signal for the grid_k-pThe frequencies of the k-p th harmonic and inter-harmonic components of the real signal are sampled for the grid,

sampling the initial phase angles of the k-p harmonic and inter-harmonic components of the real signals for the power grid;

defining an L x 1 dimensional semaphore X (n), L >2p, in combination with equation (15) having:

X(n)＝[x(n),x(n+1),L,x(n+L-1)]^T； (16)

equation (15) can be described using equation (14) as:

X(n)＝S(n)+W(n)＝Aφⁿα+W(n)； (17)

where, s (n) is the vector of the nth sample point, α is the inter-harmonic amplitude, a is the phase, Φ is the twiddle factor matrix, s (n) is a Φ matrixⁿα＝[x(n),x(n+1),L,x(n+L-1)]^T，Α＝[α(ω₁),α(ω₂),L,α(ω_2p)]，

W(n)＝[W(n),W(n+1),L,W(n+L-1)]^T；

The first row S (n) and the last row are removed, and vectors S1 and S2 which are mutually staggered are obtained by a vertical decomposition method respectively:

let S2 be S1 phi, the frequency information of the signal is completely contained in the twiddle factor matrix phi.

Based on the constraint of minimum overall mean square error, estimating the frequency parameters of the inter-harmonics, wherein the process is as follows:

(1) constructing a HANKEL matrix by using the sampled data:

wherein M is the array element number, N is the fast beat number, and M > L > >2 p.

(2) Singular value decomposition is performed on the matrix X:

wherein L is a left singular vector matrix, U^HIs a right singular vector matrix, L_sLeft singular vector matrix, L, corresponding to the maximum singular value_nIs a left singular vector matrix corresponding to the minimum singular value, sigma is a diagonal matrix of singular values arranged in descending order,

is a right singular value vector matrix corresponding to 2P maximum singular values, where Σ s is

To form a signal subspace;

is a right singular value vector matrix corresponding to L-2P minimum singular values, and sigma n is

To a noise subspace;

(3) remove

The first line and the last line of the vector are respectively obtained by a vertical decomposition method to form two mutually staggered vectors U₁And U₂Let U₁＝ΨU₂Using least squares to pair the matrix [ U ]₁,U₂]Singular value decomposition is carried out:

(4) will be provided with

The matrix is decomposed into 4 2P × 2P square matrices:

then there are:

(5) to psi_TLSDecomposing the characteristic value to obtain the characteristic value lambda_kThe SVM wave-emitting frequency parameter estimated thereby

Comprises the following steps:

the above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. The intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation is characterized by comprising the following components:

MPPT controller for tracking maximum power of DC/DC converter and outputting positive sequence DC reference voltage U_ref+ and DC reference current

A positive and negative sequence voltage decomposition module for detecting the three-phase voltage V at the side of the inverter network_a、V_b、V_cDecomposed into positive sequence three-phase voltage V_a+、V_b+、V_c+ and negative sequence three-phase voltage V_a-、V_b-、V_c-；

Phase-locked loop for positive sequence three-phase voltage V according to input_a+、V_b+、V_cGiving a voltage starting angle theta and a frequency f;

a current correction module for correcting the current according to the three-phase standard current I'_a、I′_b、I′_cAnd inverter side inductance L of LCL filter_fThree-phase detection current I of_a、I_b、I_cFor C of LCL filter_fAnd R_fThree-phase average current I output at the module_aavg、I_bavg、I_cavgCorrecting;

a first 3S/2R conversion module for detecting the input three-phase current I_a、I_b、I_cPerforming 3S/2R conversion to output positive sequence actual active current I'_d+Positive sequence actual reactive current I'_q+Negative sequence actual active current I'_d-Negative sequence actual reactive current I'_q-；

A positive and negative sequence theory active reference current conversion module for converting the three-phase voltage V at the input grid-connected point_ga、V_gb、V_gcAnd standard three-phase voltage V'_a、V′_b、V′_cComparing, and PI controlling the comparison result to output theoretical active reference current

Positive sequence theory active reference current

Negative sequence theory active reference current

A positive and negative sequence theory reactive reference current conversion module for converting the input theoretical active reference current

And using the formula

Obtaining theoretical reactive reference current by inverse calculation

Then to the DC reference current

And theoretical reactive reference current

Comparing and outputting positive sequence theoretical reactive reference current

Negative sequence theory reactive reference current

The two-phase positive sequence static voltage conversion module is used for converting the three-phase standard voltage V 'according to the input three-phase standard voltage'_a、V′_b、V′_cOutput of the current correction module, voltage initial angle theta, and positive sequence three-phase voltage V_a+、V_b+、V_cd.C bus capacitor voltage U_busPositive sequence DC reference voltage U_refOutput current I of the photovoltaic array_pvAverage current I output by the whole DC system of the photovoltaic array_pvavgPositive and negative sequence theory active reference current

Positive and negative sequence actual active current I'_d+、I′_d-Converted to obtain two-phase positive sequence static voltage U_α+、U_β+；

The two-phase negative sequence static voltage conversion module is used for converting the three-phase standard voltage V 'according to the input three-phase standard voltage'_a、V′_b、V′_cOutput of the current correction module, voltage initial angle theta, negative sequence three-phase voltage V_a-、V_b-、V_cPositive sequence reactive DC reference current I_qrefPositive and negative sequence theoretical reactive reference current

Actual reactive current I 'of positive and negative sequence'_q+、I′_q-Converted to obtain two-phase negative sequence static voltage U_α-、U_β-；

The TE-SVM wave-transmitting module estimates the frequency of the smart grid based on the TLS-ESPRIT algorithm and utilizes the two-phase positive sequence static voltage U_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_βSynthesizing three-phase reference voltage, taking the power grid frequency output by the phase-locked loop or the smart power grid frequency solved by the TLS-ESPRIT algorithm as wave-sending frequency, and sending waves by combining the synthesized three-phase reference voltage to control the inverter to invert.

2. The intelligent controller of a one-stop intelligent megawatt box system based on TE-SVM modulation of claim 1,

the current correction module includes:

a first comparator of the current correction module for comparing C of the LCL filter_fAnd R_fThree-phase average current I at the assembly_aavg、I_bavg、I_cavgInverter side inductor L with LCL filter_fThree-phase current I of_a、I_b、I_cConverging and carrying out error comparison;

the proportion controller is used for carrying out proportion control on the output of the first comparator of the current correction module;

a second comparator of the current correction module for comparing the output of the comparative controller with the three-phase standard current I'_a、I′_b、I′_cCarrying out error comparison;

the two-phase positive sequence static voltage conversion module comprises:

a positive sequence active and reactive current conversion module for converting the output result of the current correction module to obtain positive sequence theoretical active current I_d+ and positive-sequence theoretical reactive current I_q+；

A positive sequence voltage conversion module for converting the input three-phase standard voltage V'_a、V′_b、V′_cCoordinate transformation and filtering are carried out to obtain positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+；

A first positive-sequence active reference current conversion module for converting the input DC capacitor voltage U_busPositive sequence DC reference voltage U_ref+ performing coordinate transformation and PI control to obtain a first positive sequence active reference current I_dref1+；

A second positive-sequence active reference current conversion module for outputting current I to the input photovoltaic array_pvAverage current I output by the whole direct current system of the photovoltaic array_pvavgComparing and PI controlling to obtain a second positive sequence active reference current I_dref2+；

A positive sequence third comparator for the first positive sequence active DC reference current I_dref1+A second positive-sequence active direct-current reference current I_dref2+Positive sequence theoretical active current I_dPositive and negative sequence theory active reference current

And positive sequence actual active current I'_d+Converging and carrying out error comparison;

a third PI controller for performing proportional-integral control on the output current of the positive sequence third comparator and outputting a positive sequence active DC reference voltage U_d+；

A positive sequence fourth comparator for positive sequence reactive DC reference current I_qrefPositive and negative sequence theoretical reactive current I_qPositive and negative sequence theory reactive reference current

And positive sequence actual reactive current I'_q+Converging and carrying out error comparison;

a fourth PI controller for performing proportional-integral control on the output current of the positive sequence fourth comparator and outputting a positive sequence reactive DC reference voltage U_q+；

A positive sequence low voltage ride through control module for detecting whether voltage drop occurs at the grid-connected point, performing low voltage ride through control when the voltage drop occurs at the grid-connected point, controlling the input of the third PI controller and the fourth PI controller, and further controlling the generation of positive sequence reactive direct current at different momentsCurrent reference voltage U_qInjecting reactive power into the power grid to enable the photovoltaic power generation to operate without grid disconnection;

first cross coupler ω L for aligning positive sequence reactive current I_d+ and positive sequence reactive current I_q+ cross-coupling to counteract reactive current I_d+ and positive sequence reactive current I_q+ coupling term, subjecting d-axis component to I_dAction of + q-axis component by I_q+ to function;

a positive sequence fifth comparator for positive sequence active DC reference voltage U_dPositive and negative active voltage V_dThe active outputs of the + and the +/-omega L of the first cross coupler are converged to carry out error comparison;

a positive sequence sixth comparator for positive sequence reactive DC reference voltage U_q ⁺Positive sequence reactive voltage V_q ⁺And the reactive outputs of the first cross coupler +/-omega L are converged, and error comparison is carried out;

a first 2R/2S coordinate transformation module for performing 2R/2S coordinate transformation on the outputs of the positive sequence fifth comparator and the positive sequence sixth comparator according to the input voltage initial angle theta to obtain a two-phase positive sequence static voltage U_α+、U_β+。

3. The intelligent controller of a one-stop intelligent megawatt box system based on TE-SVM modulation of claim 2,

the positive sequence active and reactive current conversion module comprises:

a second 3S/2R conversion module for performing 3S/2R coordinate conversion on the output result of the current correction module according to the input voltage initial angle theta and outputting a positive sequence active current I_d+ and positive sequence reactive current I_q+；

A first low pass filter LPF for correcting the positive sequence active current I_d+ and positive sequence reactive current I_q+ low-pass filtering to eliminate high frequency part and maintain low frequency part;

a first band pass filter BPF for performing band pass filtering on the output of the first LPF to filter out noise outside the bandwidth and output clean positive sequence active powerCurrent I_d+ and positive sequence reactive current I_q+；

The positive sequence voltage conversion module includes:

a third 3S/2R conversion module for converting the input three-phase standard voltage V 'according to the input voltage starting angle theta'_a、V′_b、V′_cPerforming 3S/2R coordinate conversion and outputting positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+；

A second low pass filter LPF for correcting the positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+ low-pass filtering to eliminate high frequency part and maintain low frequency part;

a second band-pass filter BPF for performing band-pass filtering on the output voltage of the second low-pass filter LPF, filtering noise outside the bandwidth, and outputting a clean positive-sequence active voltage V_d+ and positive sequence reactive voltage V_q+；

The first positive sequence active reference current conversion module comprises:

positive sequence first comparator for DC capacitor voltage U_busAnd positive sequence DC reference voltage U_ref+ converging and comparing errors;

the fourth 3S/2R conversion module is used for performing 3S/2R coordinate conversion on the output result of the positive sequence first comparator and removing alternating current harmonic components in the direct current voltage;

a first PI controller for performing proportional-integral control on the output voltage of the fourth 3S/2R conversion module and outputting a first positive-sequence active direct-current reference current I_dref1+；

The second positive sequence active reference current conversion module comprises:

a positive sequence second comparator for the output current I of the photovoltaic array_pvAverage current I output by the whole direct current system of the photovoltaic array_pvavgConverging and comparing errors;

a second PI controller for performing proportional-integral control on the output current of the positive sequence second comparator and outputting a second positive sequence active direct current reference current I_dref2+。

4. The intelligent controller for a one-stop intelligent megawatt box system based on TE-SVM modulation of claim 2 wherein the positive sequence low voltage ride through control module comprises:

a first low voltage ride through module for outputting three-phase voltage V according to input_a、V_b、V_cDetecting whether voltage drop occurs at a grid-connected point, performing droop control, and outputting a droop voltage root-mean-square;

the first root mean square detection module is used for performing root mean square detection on the output of the first low-voltage ride-through module;

a reference power calculation module for calculating the instantaneous value of the active power and the instantaneous value of the reactive power of the fundamental wave, and comparing the instantaneous values of the active power and the reactive power with the standard active power and the reactive power and the actual power at the intelligent grid-connected point to obtain a reference power P^*；

A third 2R/2S coordinate conversion module for correcting positive sequence active voltage V_d+ and positive sequence reactive voltage V_q+ 2R/2S coordinate conversion to obtain negative sequence positive sequence two-phase static voltage U_a、U_B；

A first reference current calculation module for calculating a reference power P^*Two-phase static voltage U_a、U_BCalculating a positive sequence reference current

A first voltage and current calculation module for calculating a positive-sequence two-phase static voltage U_a、U_BAnd positive sequence reference current

Combination formula

And

computing grid connectionPoint voltage U_NAnd current I_total；

The first voltage drop determining module is used for determining the voltage drop delta U according to the result of the first root mean square detection module when low voltage ride through occurs, and determining the voltage when the low voltage ride through is performed on the voltage drop of the grid-connected point and the grid-connected point voltage U when the droop voltage root mean square exists_NComparing to obtain a voltage drop delta U; when no droop voltage root mean square exists, namely the voltage of the grid-connected point during low voltage ride through when the grid-connected point has voltage drop and the grid-connected point voltage U_NWhen the two phases are equal, the zero voltage ride through is shown to occur, and the three-phase average voltage V output by the inverter is adopted_iava、V_iavb、V_iavcAnd grid point voltage U_NComparing to obtain a voltage drop delta U;

the first low voltage ride through control module sets the positive sequence active power to 0 when low voltage ride through occurs, namely the positive sequence active current

I_d+、I’_d+Is 0, the power factor is set to be 1, and the positive sequence reactive reference current I under the condition of 1 power factor is output_qref+Performing low voltage ride through control according to the voltage drop delta U; then current flows

I_q+、I’_q+、I_qref+Comparing to obtain the maximum difference value delta i_q+Positive sequence reactive current Δ i_q+As initial suitable current I_rectiveInputting the positive sequence reactive voltage U generated by the fourth PI controller_q+Performing reactive compensation and adapting to the current I_rectiveAnd the total current I_totalGradually rises to 20%, and the voltage drop delta U and the voltage U are_NThe ratio reaches 10 percent; positive sequence active current

I_d+、I’_d+、I_dref1+、I_dref2+Comparing to obtain the maximum difference value delta i_d+Will be positive sequence active current Δ i_d+Inputting the positive sequence active voltage U generated by a third PI controller_d+Positive sequence active current Δ i_d+And positive sequence reactive current Δ i_q+Synthesized as a suitable current I_rectivVoltage drop Δ U and voltage U_NThe ratio is gradually increased from 10% to 20%, and the active current delta i is in positive sequence_d+And positive sequence reactive current Δ i_q+Under continuous injection of (2), current ratio I_rective/I_totalGradually increasing from 20% to 45%, keeping the inverter in uninterrupted operation for 1s, and decreasing the power factor from 1 to delta U/U_NGradually increased to 50% and adapted to the current I_rectiveReach I from 0 within 4s_totalThe power factor is reduced to 0, and the positive sequence reactive current is delta i_q+And 0, normally injecting positive sequence active power into the power grid.

5. The intelligent controller of one-stop intelligent megawatt box system based on TE-SVM modulation according to any one of claims 1 to 4,

the two-phase negative sequence quiescent voltage conversion module comprises:

a voltage initial phase angle determining module for determining the three-phase voltage V according to the input voltage initial angle theta and the negative sequence three-phase voltage V_a-、V_b-、V_c-, converting to obtain a voltage initial phase angle

A negative sequence active and reactive current conversion module for converting the output result of the current correction module to obtain the negative sequence theoretical active current I_dAnd negative sequence theoretical reactive current I_q-；

A negative sequence voltage conversion module for converting the input three-phase standard voltage V'_a、V′_b、V′_cConverting to obtain negative-sequence active voltage V_d-and positive sequence reactive voltage V_q-；

A fifth PI controller for negative-sequence active current I_dNegative sequence actual active current I'_d-And negative sequence theory active reference current

PI control is carried out, and negative sequence active direct current reference voltage U is output_d-；

Negative sequence first comparator for negative sequence reactive current I_qNegative sequence reactive DC reference current I_qrefNegative sequence actual reactive current I'_q-And negative sequence theory reactive reference current

Converging and carrying out error comparison;

a sixth PI controller for PI controlling the output current of the negative sequence first comparator and outputting a negative sequence reactive DC reference voltage U_q-；

The negative sequence low voltage ride through control module is used for detecting whether voltage drop occurs at the grid-connected point or not, performing low voltage ride through control when the voltage drop occurs at the grid-connected point, controlling the input of the fifth PI controller and the sixth PI controller, and further controlling the generation of a negative sequence active direct current reference voltage U at different moments_qInjecting reactive power into the power grid, so that the photovoltaic power generation does not run off the grid;

a second cross-coupler ω L for the negative-sequence reactive current I_dWith negative-sequence reactive current I_q-cross-coupling to cancel the negative sequence reactive current I_dWith negative-sequence reactive current I_qCoupling term of (d) by the d-axis component_dThe q-axis component is given by_q-an effect;

negative sequence second comparator for negative sequence active DC reference voltage U_dNegative-sequence active voltage V_d-converging the active outputs of the second cross-couplers ± ω L for error comparison;

a negative sequence third comparator for negative sequence reactive DC reference voltage U_qNegative sequence reactive voltage V_q-and reactive outputs of the second cross-couplers ± ω L converge, making an error comparison;

a second 2R/2S coordinate transformation module for transforming the initial voltage angle theta and the initial voltage phase angle theta

2R/2S coordinate transformation is carried out on the output of the negative sequence second comparator and the negative sequence third comparator to obtain two-phase negative sequence static voltage U_α-、U_β-；

The TE-SVM wave-transmitting module comprises:

the TLS-ESPRIT frequency estimation module is used for estimating the frequency of the smart grid based on a TLS-ESPRIT algorithm;

the SVM wave-transmitting module is used for transmitting the two-phase positive sequence static voltage U_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_β-, synthesizing three-phase reference voltages

Wave sending is carried out according to the power grid frequency output by the phase-locked loop or the frequency of the intelligent power grid estimated by the TLS-ESPRIT frequency estimation module;

and the gate controller is used for controlling each switch module of the inverter to be switched on or switched off according to the vector signal sent by the SVM wave sending module.

6. The intelligent controller of a one-stop intelligent megawatt box system based on TE-SVM modulation of claim 5,

the voltage initial phase angle determination module includes:

a fifth 3S/2R conversion module for converting the input negative sequence three-phase voltage V according to the input voltage initial angle theta_a-、V_b-、V_c-carrying out 3S/2R coordinate conversion to obtain an active voltage V_dAnd a reactive voltage V_q；

A module for calculating an initial phase angle according to the active voltage V_dAnd a reactive voltage V_qCalculating to obtain the initial phase angle of voltage

The negative sequence active and reactive current conversion module comprises:

a sixth 3S/2R transformation module for transforming the voltage according to the voltage initial angle theta and the voltage initial phase angle

3S/2R coordinate conversion is carried out on the output current of the current correction module, and negative-sequence active current I is output_d-and a negative sequence reactive current I_q-；

A third low pass filter LPF for the negative sequence active current I_d-and a negative sequence reactive current I_q-low-pass filtering to remove the high frequency part and to retain the low frequency part;

a third band-pass filter BPF for performing band-pass filtering on the output current of the third low-pass filter LPF, filtering noise outside the bandwidth and outputting a clean negative-sequence active current I_d-and a negative sequence reactive current I_q-；

The negative sequence voltage conversion module includes:

a seventh 3S/2R transformation module for transforming the voltage according to the voltage initial angle theta and the voltage initial phase angle

To input three-phase standard voltage V'_a、V′_b、V′_c3S/2R coordinate conversion is carried out, and negative sequence active voltage V is output_d-and negative sequence reactive voltage V_q-；

A fourth low pass filter LPF for applying a negative sequence active voltage V_d-and negative sequence reactive voltage V_q-low-pass filtering to remove the high frequency part and to retain the low frequency part;

a fourth band-pass filter BPF for band-pass filtering the output voltage of the fourth LPF, filtering out noise outside the bandwidth and outputting clean negative-sequence active voltage V_d-and positive sequence reactive voltage V_q-；

The negative sequence low voltage ride through control module comprises:

a second low voltage ride through module for outputting a negative sequence three-phase voltage V according to the input_a-、V_b-、V_c-detecting whether a voltage drop occurs at the grid connection point, andcarrying out droop control and outputting droop voltage root-mean-square;

the second root mean square detection module is used for performing root mean square detection on the output of the second low-voltage ride through module;

a third-order negative-sequence maximum current calculating module for calculating the positive-sequence reactive DC reference current I_qref+, maximum current I_maxInitial phase angle of sum voltage

Calculating the third-order negative-sequence maximum current I_qmax-；

A fourth 2R/2S coordinate conversion module for converting the negative-sequence active voltage V_d-and negative sequence reactive voltage V_q-2R/2S coordinate transformation to obtain a negative-sequence two-phase rest voltage U_a、U_B；

A second reference current calculation module for calculating a reference power P^*Negative sequence two-phase static voltage U_a、U_BCalculating a negative sequence reference current

A second voltage and current calculation module for calculating two-phase static voltage U according to negative sequence_a、U_BAnd negative sequence reference current

Combination formula

And

calculating the voltage U of the grid-connected point_NAnd current I_total；

The second voltage drop determining module is used for determining the voltage drop delta U according to the result of the second root mean square detection module when low voltage ride through occurs, and determining the voltage drop delta U when the voltage drop occurs to the grid-connected point and the low voltage ride through is performed when the voltage drop occurs to the grid-connected point when the drop occurs to the root mean square of the drop voltageVoltage and grid point voltage U_NComparing to obtain a voltage drop delta U; when no droop voltage root mean square exists, namely the voltage of the grid-connected point during low voltage ride through when the grid-connected point has voltage drop and the grid-connected point voltage U_NWhen the two phases are equal, the zero voltage ride through is shown to occur, and the three-phase average voltage V output by the inverter is adopted_iava、V_iavb、V_iavcAnd grid point voltage U_NComparing to obtain a voltage drop delta U;

the second low voltage ride through control module performs low voltage ride through control according to the voltage drop delta U when low voltage ride through occurs, and sets the negative sequence reactive power to 0, namely negative sequence reactive current

I_q-、I’_q-Set to 0; setting the power factor to be 1, and performing low voltage ride through control according to the voltage drop delta U; then the

I_d-、I’_d-Comparing to obtain the maximum difference value delta i_d-Negative sequence active current Δ i_d-As initial suitable current I_rectiveInputting the negative sequence active voltage U into a fifth PI controller_d-Is adapted to the current I_rectivAnd the total current I_totalGradually rises to 20%, and the voltage drop delta U and the voltage U are_NThe ratio of (A) to (B) reaches 10% and starts to rise; negative sequence reactive current

I_q-、I’_q-、I_qref-Comparing to obtain the maximum difference value delta i_q-Negative sequence reactive current Δ i_q-Inputting the negative sequence reactive voltage U into a sixth PI controller_q-Negative sequence reactive current Δ i_q-And negative sequence active current delta i_d-Synthesized as a suitable current I_rectivVoltage drop Δ U and voltage U_NThe ratio is gradually increased from 10% to 20%, and the reactive current delta i in the negative sequence_q-With negative-sequence active currentΔi_d-Under continuous injection of (2), current ratio I_rective/I_totalGradually increasing from 20% to 45%, keeping the inverter running for 1s without interruption, and reducing the power factor from 1 by delta U/U_NGradually increased to 50% and adapted to the current I_rectiveReach I from 0 within 4s_totalAnd when the power factor is reduced to 0, the negative sequence active current injects negative sequence active power to the power grid normally, and the negative sequence reactive voltage of the negative sequence reactive power is limited.

7. The control method of the one-stop intelligent megawatt box system based on TE-SVM modulation is characterized in that the intelligent controller of the one-stop intelligent megawatt box system based on TE-SVM modulation, which is disclosed by any one of claims 1-6, is adopted, and the control method comprises the following steps:

step S1, receiving the actual active power and reactive power at the intelligent grid-connected point, and outputting a three-phase voltage V by the inverter_a、V_b、V_cThree-phase voltage V at grid-connected point_ga、V_gb、V_gcThree-phase average voltage V_iava、V_iavb、V_iavcThree-phase current I_a、I_b、I_cThree-phase average current I_aavg、I_bavg、I_cavgDC bus capacitor voltage U_busOutput current I of the photovoltaic array_pvAverage current I_pvavgAnd tracking the maximum power of the DC/DC converter by adopting an MPPT controller to output a positive sequence direct current reference voltage U_ref+And a DC reference current

Step S2, calculating standard active power and reactive power, and an active power instantaneous value and a reactive power instantaneous value at an intelligent grid connection point;

step S3, judging whether the actual active power and reactive power at the intelligent grid-connected point are corresponding to the calculated active power instantaneous value and reactive power instantaneous value at the intelligent grid-connected point and the standard active power and reactive power; judging whether the frequency output by the phase-locked loop is within the range of 50 +/-0.1 Hz;

s4, when the actual active power and the reactive power at the intelligent grid-connected point are correspondingly consistent with the calculated active power instantaneous value and the calculated reactive power instantaneous value at the intelligent grid-connected point, and the standard active power and the calculated reactive power are consistent, and the frequency output by the phase-locked loop is within the range of 50 +/-0.1 Hz, taking the frequency output by the phase-locked loop as the wave-transmitting frequency of the SVM wave-transmitting module; otherwise, carrying out frequency search of the smart power grid by using the TLS-ESPRIT frequency estimation module, and taking the searched frequency as the wave transmitting frequency of the SVM wave transmitting module;

step S5, calculating three-phase standard voltage V 'according to the voltage and current signals received in the step S1'_a、V′_b、V′_cThree-phase Standard Current I'_a、I′_b、I′_cStandard active power and reactive power, and an active power instantaneous value and a reactive power instantaneous value at an intelligent grid-connected point, and a two-phase positive-sequence static voltage U is obtained by using a two-phase positive-sequence static voltage conversion module and a two-phase negative-sequence static voltage conversion module_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_β-; utilizing an SVM wave-transmitting module to transmit a voltage U according to a two-phase positive sequence_α+、U_β+ and two-phase negative sequence rest voltage U_α-、U_βSynthesizing a reference voltage, then carrying out SVM wave-sending based on the wave-sending frequency and the reference voltage, and controlling each switch module of the inverter to be switched on or switched off by adopting SVPWM (space vector pulse width modulation) according to a vector signal generated by the SVM wave-sending by a voltage-sharing gate controller.

8. The TE-SVM modulation based control method for one-stop smart megawatt-box system friendly access to a smart grid according to claim 7, wherein in the step S5:

calculating three-phase standard voltage V 'according to formula (1)'_a、V′_b、V′_c：

Wherein, V_pIs the positive sequence voltage peak, V_nIs the peak value of the negative-sequence voltage,

is the initial phase angle of the positive sequence voltage,

is the initial phase angle of the negative sequence voltage; ω is the fundamental voltage angular frequency;

three-phase standard current I'_a、I′_b、I′_cCalculating according to the formula (2):

wherein, I_pIs the peak value of the positive sequence current, I_nIs the peak value of the negative-sequence current, theta_pIs the starting angle, theta, of the positive and negative sequence currents relative to the positive sequence voltage_nIs the starting angle of the negative sequence voltage relative to the negative sequence voltage;

in step S5, positive and negative sequence impedances are calculated when the first low voltage ride through module and the second low voltage ride through module perform droop control, wherein:

positive sequence impedance Z_P(S) calculating according to the formula (3):

wherein, K_mIs the inverter voltage gain, V_dcIs the voltage difference between two ends of the DC bus capacitor, H_i(s-j2πf₁) Is the closed loop transfer function, T, of the current inner loop PI controller, i.e. the first PI controller_PLL(s-j2πf₁) Is the closed loop transfer function of the phase locked loop, f₁At fundamental frequency, K_dAs a gain of a weighting function, K_fAs integral proportional parameter, G_i(s) is the equivalent transfer function of the current filter consisting of the first low-pass filter LPF and the first band-pass filter BPF, L_fInductance value of inverter-side inductor of LCL filter, c₁Is a DC bus capacitance value; g_v(s) is the equivalent transfer function of the voltage filter consisting of the second low pass filter LPF and the second band pass filter BPF, s denotes the complex frequency domain,

is the initial phase angle of the fundamental current, I₁Is the peak value of the fundamental current, V₁Is the peak value of the grid voltage;

negative sequence impedance Z_n(S) calculating according to the formula (4):

wherein H_i(s+j2πf₁) Is the closed loop transfer function of the current inner loop PI controller, i.e. the first PI controller, G_i(s) is the equivalent transfer function of the current filter consisting of the first low-pass filter LPF and the first band-pass filter BPF, G_v(s) is the equivalent transfer function of the voltage filter consisting of the fourth low pass filter LPF and the fourth band pass filter BPF;

the standard active power and the standard reactive power are calculated according to formulas (7) to (8):

wherein P (t) is standard active power, Q (t) is standard reactive power, V_α、V_βFor corresponding voltages in the stationary reference frame of α β, I_α、I_βFor corresponding currents in the stationary reference frame of α β, θ₁For the starting angle of the actual current of the grid with respect to the voltage, theta₂For starting of phase-locked loop outputAn angle;

the active power instantaneous value and the reactive power instantaneous value at the intelligent grid-connected point are calculated according to a formula (9):

wherein, P₀(t) is the instantaneous value of the active power of the fundamental wave, Q₀(t) is the fundamental reactive power instantaneous value; v_pIs the positive sequence voltage peak, V_nIs the negative sequence voltage peak; i is_pIs the peak value of the positive sequence current, I_nIs the peak value of the negative-sequence current, theta_pIs the starting angle of the positive sequence current with respect to the positive sequence voltage, θ_nIs the starting angle of the negative sequence current relative to the negative sequence voltage;

the step S5 synthesizes the vector reference voltage according to the following formula

9. One-stop intelligent megawatt box system based on TE-SVM modulation is characterized by comprising the following components:

the photovoltaic array is used for carrying out solar power generation and outputting electric energy;

the at least two inverter integrated megawatt boxes are respectively used for sequentially converging, reducing voltage and inverting the direct current output of the photovoltaic array and outputting three-phase alternating current;

the system comprises at least two SVM controllers, a power supply module and a power supply module, wherein the at least two SVM controllers are connected with inverters of all inverter integrated megawatt boxes in a one-to-one correspondence manner, and each SVM controller carries out inversion control on the inverter connected with the SVM controller based on TE-SVM modulation;

the power supply switching module is used for automatically switching all the inverter integrated megawatt boxes connected with the power supply switching module, so that only one inverter integrated megawatt box supplies power to the intelligent power grid at the same time;

the measurement and control power cabinet is used for performing master-slave competitive control on all the inverter integrated megawatt boxes according to the frequency, amplitude and phase of three-phase alternating current output by the inverters of all the inverter integrated megawatt boxes and the temperature detection result of each switch module of all the inverters, selecting the optimal one of all the inverter integrated megawatt boxes in real time by adopting a competitive ranking first standard, taking the currently selected optimal one as a master inverter, taking the rest inverter integrated megawatt boxes as slave inverters, and controlling a double-power-supply switching device correspondingly connected with the master inverter to work and perform automatic switching so as to enable the master inverter to supply power for an intelligent power grid;

the boost transformer is used for boosting the three-phase alternating current output by the double-power-supply switching device correspondingly connected with the main inverter integrated megawatt box and inputting the boosted three-phase alternating current into the smart grid;

wherein:

the power supply switching module is composed of at least one dual-power switching device, each dual-power switching device is correspondingly connected with two inverter integrated megawatt boxes, and each dual-power switching device automatically switches the two inverter integrated megawatt boxes connected with the dual-power switching device according to a control signal when working.

10. The TE-SVM modulation based one-stop smart megawatt box system of claim 9 further comprising a smart electric energy meter bank disposed at a utility point of a smart grid;

each of the inverter integrated megawatt boxes comprises:

the junction box is used for merging the output of the photovoltaic array, and a first circuit breaker is arranged on each connecting line of the junction box and the photovoltaic array;

the DC/DC conversion module is used for carrying out voltage reduction conversion on the direct current output by the combiner box;

the direct current bus capacitor is used for filtering direct current output by the DC/DC conversion module and then using the filtered direct current as a direct current power supply;

the three-bridge arm inverter is used for performing DC/AC conversion on the direct current subjected to voltage reduction conversion and outputting three-phase alternating current;

the LCL filter is used for filtering the three-phase alternating current output by the three-bridge-arm inverter;

the output end of the SVM controller is connected with the input end of the measurement and control power cabinet through a paired cloud manager;

every the net side of the integrated megawatt case of dc-to-ac converter is provided with the second circuit breaker, and the three-phase line of second circuit breaker output divides two the tunnel, and wherein the three-phase line of one kind inserts the third circuit breaker, and the external observing and controlling power cabinet of third circuit breaker, another three-phase line of second circuit breaker output external dual supply auto-change over device who corresponds.

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