CN116706990A - Net-structured control method and system applied to photovoltaic system - Google Patents

Net-structured control method and system applied to photovoltaic system Download PDF

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Publication number
CN116706990A
CN116706990A CN202310620101.8A CN202310620101A CN116706990A CN 116706990 A CN116706990 A CN 116706990A CN 202310620101 A CN202310620101 A CN 202310620101A CN 116706990 A CN116706990 A CN 116706990A
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grid
output
voltage
connected inverter
current
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唐彬伟
陈烁
郭江涛
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MingYang Smart Energy Group Co Ltd
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MingYang Smart Energy Group Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a grid-formation control method and a grid-formation control system applied to a photovoltaic system, which are mainly applied to the photovoltaic system which adopts a unipolar grid-connected inverter for grid connection. The method comprises the following steps: MPPT (maximum power tracking) control link, frequency-voltage control link, current inner loop control link and modulation link. The voltage source characteristic and the grid-structured control strategy of the invention are more stable in running in the weak power grid, the grid-structured control strategy does not depend on the frequency/phase of the power grid, and the regulation of the frequency and the voltage in the weak power grid is more stable, thereby being beneficial to the stable running of the system.

Description

Net-structured control method and system applied to photovoltaic system
Technical Field
The invention relates to the technical field of grid connection of photovoltaic systems, in particular to a grid-formation control method, a grid-formation control system, a storage medium and computing equipment applied to the photovoltaic systems.
Background
With the increase of new energy and permeability of power electronic equipment, the power system has the trend of inertia reduction and weakening of system strength, and the stability problem is more serious. The grid-formed control technology can improve the voltage and frequency supporting capability of the grid-connected inverter and enhance the stability of the power system.
The grid-connected inverter is controlled by adopting a follow-up network, and is synchronous with a power grid, phase information of the grid-connected point is measured by a phase-locked loop, so that stability problem exists in a weak power grid. In a power grid with weak system strength and low physical inertia, the grid-connected inverter is preferably controlled by adopting a grid structure, and can realize synchronization without a phase-locked loop, so that the operation stability of the photovoltaic system can be effectively improved.
The existing grid-formed control technology adopts a sagging control technology, under the condition of disturbance, the adjusting speed is slower, the system control is easy to be unstable, and large short-circuit current is easy to be caused in the power grid fault, so that the stable operation of the grid-connected inverter is not facilitated.
Disclosure of Invention
The first aim of the invention is to overcome the defects and shortcomings of the prior art, and provide a grid-formed control method applied to a photovoltaic system, which introduces DC side voltage deviation as correction quantity on the basis of the traditional grid-formed active-frequency droop control mode to generate the amplitude and phase angle of the output reference voltage of a grid-connected inverter, supports a power grid during disturbance, can quickly adjust and recover the steady-state operation of the system, and improves the stability of grid-connected operation of the photovoltaic system.
A second object of the present invention is to provide a grid-formation control system applied to a photovoltaic system.
A third object of the present invention is to provide a storage medium.
It is a fourth object of the present invention to provide a computing device.
The first object of the invention is achieved by the following technical scheme: a network construction type control method applied to a photovoltaic system is applied to the photovoltaic system which adopts a unipolar grid-connected inverter for grid connection, and comprises the following steps:
MPPT control link for operating photovoltaic system at maximum power point to obtain grid-connected inverter output active power reference value P ref And a DC side voltage reference value V dcref ；
A frequency-voltage control link, according to the P generated by MPPT control link ref And V dcref The amplitude V of the output reference voltage of the grid-connected inverter is obtained through control operation * And a phase angle theta, then Clark and Park conversion are carried out to obtain the dq axis component of the output reference voltage of the grid-connected inverter, and the dq axis component of the three-phase voltage of the grid-connected point is compared, and the difference value is used as the output of the frequency-voltage control link;
the current inner loop control link takes the output current of the grid-connected inverter as a control target, receives the output from the frequency-voltage control link as input, then sends the output to the PI controller, limits the output of the PI controller, superimposes the dq axis component of the instantaneous value of the three-phase current of the grid-connected point and the dq axis component of the capacitance current of the LC type filter of the photovoltaic system on the limited value to respectively obtain the dq axis component of the reference value of the output current of the grid-connected inverter, and sends the dq axis component of the output current of the grid-connected inverter to the PI controller after differencing with the dq axis component of the three-phase voltage of the grid-connected point, and the output of the PI controller is differenced with the dq axis component of the inductance voltage of the LC type filter to obtain the output of the current inner loop control link;
and the modulation control link is input as the output of the current inner loop control link, compares the generated three-phase voltage reference signal with the triangular wave signal, and obtains the trigger pulse for driving the grid-connected inverter to operate through sine pulse width modulation.
Further, the photovoltaic system comprises a photovoltaic module PV and a direct-current side capacitor C dc The grid-connected inverter, the controller and the LC filter; the photovoltaic module PV is used for converting received light energy into electric energy; the DC side capacitor C dc As an intermediate unit for energy transmission, the stable direct-current side voltage can be provided for the grid-connected inverter; the Grid-connected inverter is used for receiving trigger pulses of the controller, converting direct current generated by the photovoltaic module PV into alternating current by controlling the on-off of the IGBT of the Grid-connected inverter, and transmitting power to the Grid; the controller is a core control component of the photovoltaic system, can collect voltage and current signals, controls the voltage stability of the direct current side, and generates trigger pulses to drive the IGBT of the grid-connected inverter to be turned on and off; the LC type filter is used forThe higher harmonic components of the voltage and the current output by the grid-connected inverter are filtered, so that the voltage and the current output by the grid-connected inverter are more similar to sine waves, and the electric energy quality of the grid-connected inverter is improved;
wherein the controller collects three-phase voltage and phase current instantaneous value v of the grid-connected point in real time gx 、i gx The grid-connected inverter outputs three-phase voltage and phase current instantaneous value e x 、i x Voltage and current v output by photovoltaic module PV PV 、i PV And a DC side voltage real-time value V dc The method comprises the steps of carrying out a first treatment on the surface of the Where x=a, b, c.
Further, in the MPPT control link, v collected by the controller is obtained by adopting a disturbance observation algorithm PV 、i PV Control is carried out to obtain an active power reference value P output by the grid-connected inverter ref And a DC side voltage reference value V dcref 。
Further, the frequency-voltage control link comprises a frequency control link and a voltage control link; the frequency control link adopts active power droop control and direct-current side voltage droop control, and the droop equation is omega=omega 0 +Δω 1 +Δω, where ω 0 Is the power frequency angular frequency omega of the power grid 0 ＝2πf 0 ，f 0 Is the power frequency of the power grid, delta omega 1 Angular frequency deviation, Δω, for active power droop control 1 ＝d P *(P ref -P LPF ) Δω is the angular frequency deviation amount obtained by the dc side voltage droop control; in active power droop control, the controller is controlled according to v gx 、i gx Calculating real-time value P of output active power of grid-connected inverter, and performing first-order low-pass filtering (omega c For the filter cut-off frequency) to obtain a filtered active power P LPF And an active power reference value P ref Taking the difference and multiplying the droop coefficient d P Obtaining the angular frequency deviation delta omega 1 After the grid-connected inverter is synchronized with the power grid, P ref ＝P LPF The output frequency of the grid-connected inverter is consistent with the frequency of the power grid; in direct-current side voltage droop control, a controller acquires V in real time dc And V is equal to dcref Comparing, correcting the difference by PI controllerAfter that, delta omega is obtained, and when the photovoltaic system operates normally, V is present dcref ＝V dc Δω=0, at which time the dc side voltage droop control is not active, and in the case of disturbance, the deviation between the dc side voltage reference value and the real time value becomes large, at which time Δω becomes small, and by decreasing the angular frequency ω, the system is accelerated to return to the maximum power operation state; because the grid-connected inverter always needs to keep the maximum power to track and run and only supports the down regulation of the output power, the phase angle theta of the output voltage of the grid-connected inverter can be obtained by integrating omega after the PI controller sets the amplitude limiting upper limit value of the PI controller to be 0 and the omega is obtained; the control logic of the voltage control link is that the controller collects v according to the collection gx Calculating the phase voltage amplitude V g Reference amplitude V of phase voltage ref Comparing, and sending the difference to PI controller to obtain V * The method comprises the steps of carrying out a first treatment on the surface of the Then, θ and V * Clark and Park conversion are carried out to obtain d-axis component of output reference voltage of grid-connected inverterAnd q-axis component>D-axis component v of three-phase voltage with grid-connected point gd And q-axis component v gq And comparing, wherein the difference value is used as the output of the frequency-voltage control link.
Further, in the current inner loop control link, receiving the output from the frequency-voltage control link as the input thereof, then sending the output to the PI controller, and clipping the output of the PI controller, the clipped value and i gx D-axis component i of (2) gd And q-axis component i gq Q-axis component ωcv of LC filter capacitance current gd And d-axis component ωCv gq Respectively obtaining d-axis components of output current reference values of grid-connected inverters after superpositionAnd q-axis component>Then, the d-axis component i of the output current of the grid-connected inverter is matched with the d-axis component i of the output current of the grid-connected inverter d And q-axis component i q After difference, the difference is sent into a PI controller, and the output of the PI controller is respectively connected with the d-axis component v of the three-phase voltage of the grid-connected point gd And q-axis component v gq Sum and match q-axis component ωLi of LC filter inductance voltage q And d-axis component ωLi d And performing difference to obtain the output of the current inner loop control link.
Further, in the modulation control link, the input is the output of the current inner loop control link, and the input signal is subjected to inverse Park conversion and inverse Clark conversion to obtain the grid-connected inverter output voltage modulation signal e abc And comparing the trigger pulse with the set triangular wave to obtain the trigger pulse of the grid-connected inverter, thereby controlling the normal operation of the grid-connected inverter.
Further, in the current inner loop control link, current limiting is added to the output of the PI controller, so that the output current of the grid-connected inverter can be limited during the power grid fault period, and the overcurrent condition is prevented; wherein the current is limited by I gdup 1.2I is taken n ，I gdup For the upper limit value of the d-axis component of the output current of the grid-connected inverter, I n For rated current of a photovoltaic system, the lower limit value I of d-axis component of output current of grid-connected inverter gddw take-1.2I n Upper limit value I of q-axis component of grid-connected inverter output current gqup Taking outLower limit value I of q-axis component of grid-connected inverter output current gqdw Taking 0.
The second object of the invention is achieved by the following technical scheme: the utility model provides a be applied to net type control system of photovoltaic system for realize above-mentioned net type control method that is applied to photovoltaic system, it includes:
the MPPT control module is used for enabling the photovoltaic system to work at a maximum power point to obtain an active power reference value P output by the grid-connected inverter ref And a DC side voltage reference value V dcref ；
The frequency-voltage control module is used for controlling P generated in the link according to MPPT ref And V dcref The amplitude V of the output reference voltage of the grid-connected inverter is obtained through control operation * And a phase angle theta, then Clark and Park conversion are carried out to obtain the dq axis component of the output reference voltage of the grid-connected inverter, and the dq axis component of the three-phase voltage of the grid-connected point is compared, and the difference value is used as the output of the frequency-voltage control link;
the current inner loop control module takes the output current of the grid-connected inverter as a control target, receives the output from the frequency-voltage control link as input, then sends the output to the PI controller, limits the output of the PI controller, superimposes the dq axis component of the instantaneous value of the three-phase current of the grid-connected point and the dq axis component of the capacitance current of the LC type filter of the photovoltaic system, respectively obtains the dq axis component of the reference value of the output current of the grid-connected inverter, and sends the dq axis component of the reference value of the output current of the grid-connected inverter to the PI controller after differencing with the dq axis component of the three-phase voltage of the grid-connected point, and the output of the PI controller is respectively summed with the dq axis component of the inductance voltage of the LC type filter to obtain the output of the current inner loop control link;
and the modulation control module is input into the output of a current inner loop control link, compares the generated three-phase voltage reference signal with a triangular wave signal, and obtains trigger pulses for driving the grid-connected inverter to operate through sine pulse width modulation.
The third object of the invention is achieved by the following technical scheme: a storage medium storing a program which, when executed by a processor, implements the above-described grid-formation control method applied to a photovoltaic system.
The fourth object of the invention is achieved by the following technical scheme: the computing device comprises a processor and a memory for storing a program executable by the processor, wherein the processor realizes the network construction type control method applied to the photovoltaic system when executing the program stored by the memory.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the grid-formation control method and system applied to the photovoltaic system provided by the invention have the advantages that the voltage source characteristic and the grid-formation control strategy are more stable in running in a weak power grid, the grid-formation control strategy does not depend on the frequency/phase of the power grid, the regulation of the frequency and the voltage in the weak power grid is more stable, and the stable running of the system is facilitated.
Drawings
Fig. 1 is a block diagram of a photovoltaic system.
Fig. 2 is a control schematic block diagram of the method of the present invention.
FIG. 3 is a block diagram of a system according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.
Example 1
The embodiment discloses a grid-formation control method applied to a photovoltaic system, which is mainly applied to the photovoltaic system grid-connected by adopting a unipolar grid-connected inverter, and as shown in fig. 1, the photovoltaic system comprises a photovoltaic module PV and a direct-current side capacitor C dc The grid-connected inverter, the controller and the LC filter; the photovoltaic module PV is used for converting received light energy into electric energy; the DC side capacitor C dc As an intermediate unit for energy transmission, the stable direct-current side voltage can be provided for the grid-connected inverter; the Grid-connected inverter is used for receiving trigger pulses of the controller, converting direct current generated by the photovoltaic module PV into alternating current by controlling the on-off of the IGBT of the Grid-connected inverter, and transmitting power to the Grid; the controller is a core control component of the photovoltaic system, can collect voltage and current signals, controls the voltage stability of the direct current side, and generates trigger pulses to drive the IGBT of the grid-connected inverter to be turned on and off; the LC filter is used for filtering out higher harmonic components of the output voltage and current of the grid-connected inverter, so that the voltage and current output by the grid-connected inverter are more similar to sine waves, and the electric energy quality of the grid-connected inverter is improved; wherein the controller collects three-phase voltage and phase current instantaneous value v of the grid-connected point in real time gx 、i gx The grid-connected inverter outputs three-phase voltage and phase current instantaneous value e x 、i x Voltage and current v output by photovoltaic module PV PV 、i PV And a DC side voltage real-time value V dc Where x=a, b, c.
As shown in fig. 2, the network formation control method includes: MPPT (maximum power tracking) control link, frequency-voltage control link, current inner loop control link and modulation link.
The MPPT control link can enable the photovoltaic system to work at a maximum power point, and the energy utilization rate of the photovoltaic system is improved; MPPT adopts disturbance observation algorithm to collect v PV ，i PV Control is carried out to obtain an active power reference value P output by the grid-connected inverter ref And a DC side voltage reference value V dcref 。
The frequency-voltage control link is a core link of the network construction control method and is based on P generated by the MPPT control link ref And V dcref The amplitude V of the output reference voltage of the grid-connected inverter is obtained through control operation * And a phase angle θ. The frequency-voltage control link comprises a frequency control link and a voltage control link; the frequency control link adopts active power droop control and direct-current side voltage droop control, and the droop equation is omega=omega 0 +Δω 1 +Δω, where ω 0 For the power frequency angular frequency (omega) 0 ＝2πf 0 ，f 0 The power frequency of the power grid is generally 50 Hz); Δω 1 Angular frequency deviation (Δω) for active power droop control 1 ＝d P *(P ref -P LPF ) A) is provided; Δω is the angular frequency deviation amount obtained by the dc-side voltage droop control. In active power droop control, the controller is controlled according to v gx 、i gx Calculating the real-time value P of the output active power of the grid-connected inverter, and performing first-order low-pass filtering (omega c For the filter cut-off frequency) to obtain a filtered active power P LPF And an active power reference value P ref Taking the difference and multiplying the droop coefficient d P Obtaining the angular frequency deviation delta omega 1 After the grid-connected inverter is synchronized with the power grid, P ref ＝P LPF The output frequency of the grid-connected inverter is consistent with the frequency of the power grid; in direct-current side voltage droop control, a controller acquires V in real time dc And V is equal to dcref Comparing, correcting the difference value by a PI controller to obtain delta omega, when the photovoltaic system operates normally,with V dcref ＝V dc Δω=0, at which time the dc side voltage droop control is not active, and in the case of disturbance, the deviation between the dc side voltage reference value and the real time value becomes large, at which time Δω becomes small, and by decreasing the angular frequency ω, the system is accelerated to return to the maximum power operation state; because the grid-connected inverter always needs to keep the maximum power to track and run and only supports the down regulation of the output power, the phase angle theta of the output voltage of the grid-connected inverter can be obtained by integrating omega after the PI controller sets the amplitude limiting upper limit value of the PI controller to be 0 and the omega is obtained. The voltage control link control logic is that the controller is used for controlling the voltage according to the collected v gx Calculating the phase voltage amplitude V g Reference amplitude V of phase voltage ref Comparing, and sending the difference to PI controller to obtain V * The method comprises the steps of carrying out a first treatment on the surface of the Then, θ and V * Clark and Park conversion are carried out to obtain d-axis component of output reference voltage of grid-connected inverterAnd q-axis component>D-axis component v of three-phase voltage with grid-connected point gd And q-axis component v gq And comparing, wherein the difference value is used as the output of the frequency-voltage control link.
The current inner loop control link takes the output current of the grid-connected inverter as a control target, and the accuracy of the control link can be effectively improved. Receiving output from the frequency-voltage control link as input of the current loop control link, sending the input to the PI controller, and limiting the output of the PI controller (increasing current limiting, limiting the output current of the grid-connected inverter during grid faults to prevent over-current conditions; wherein, the current limiting I gdup 1.2I is taken n ，I gdup For the upper limit value of the d-axis component of the output current of the grid-connected inverter, I n For rated current of a photovoltaic system, the lower limit value I of d-axis component of output current of grid-connected inverter gddw take-1.2I n Upper limit value I of q-axis component of grid-connected inverter output current gqup Taking outLower limit value I of q-axis component of grid-connected inverter output current gqdw Taking 0), the clipped value is equal to i gx D-axis component i of (2) gd And q-axis component i gq Q-axis component ωcv of LC filter capacitance current gd And d-axis component ωCv gq After superposition, d-axis components of the output current reference value of the grid-connected inverter are obtained respectively>And q-axis component>Then, the d-axis component i of the output current of the grid-connected inverter is matched with the d-axis component i of the output current of the grid-connected inverter d And q-axis component i q After difference, the difference is sent into a PI controller, and the output of the PI controller is respectively connected with the d-axis component v of the three-phase voltage of the grid-connected point gd And q-axis component v gq Sum and match q-axis component ωLi of LC filter inductance voltage q And d-axis component ωLi d And performing difference to obtain the output of the current inner loop control link.
The purpose of the modulation control link is to compare the generated three-phase voltage reference signal with the triangular wave signal, and obtain the trigger pulse for driving the grid-connected inverter to operate through sine pulse width modulation. The input is the output of the current inner loop control link, and the input signal is subjected to inverse Park conversion and inverse Clark conversion to obtain the grid-connected inverter output voltage modulation signal e abc And comparing the trigger pulse with the set triangular wave to obtain the trigger pulse of the grid-connected inverter, thereby controlling the normal operation of the grid-connected inverter.
Example 2
The embodiment discloses a grid-formation control system applied to a photovoltaic system, which is used for implementing the method of the grid-formation control system applied to the photovoltaic system described in embodiment 1, as shown in fig. 3, and the system comprises the following functional modules:
the MPPT control module is used for enabling the photovoltaic system to work at a maximum power point to obtain an active power reference value P output by the grid-connected inverter ref And a DC side voltage reference value V dcref ；
The frequency-voltage control module is used for controlling P generated in the link according to MPPT ref And V dcref The amplitude V of the output reference voltage of the grid-connected inverter is obtained through control operation * And a phase angle theta, then Clark and Park conversion are carried out to obtain the dq axis component of the output reference voltage of the grid-connected inverter, and the dq axis component of the three-phase voltage of the grid-connected point is compared, and the difference value is used as the output of the frequency-voltage control link;
the current inner loop control module takes the output current of the grid-connected inverter as a control target, receives the output from the frequency-voltage control link as input, then sends the output to the PI controller, limits the output of the PI controller, superimposes the dq axis component of the instantaneous value of the three-phase current of the grid-connected point and the dq axis component of the capacitance current of the LC type filter of the photovoltaic system, respectively obtains the dq axis component of the reference value of the output current of the grid-connected inverter, and sends the dq axis component of the reference value of the output current of the grid-connected inverter to the PI controller after differencing with the dq axis component of the three-phase voltage of the grid-connected point, and the output of the PI controller is respectively summed with the dq axis component of the inductance voltage of the LC type filter to obtain the output of the current inner loop control link;
and the modulation control module is input into the output of a current inner loop control link, compares the generated three-phase voltage reference signal with a triangular wave signal, and obtains trigger pulses for driving the grid-connected inverter to operate through sine pulse width modulation.
Example 3
The present embodiment discloses a storage medium storing a program which, when executed by a processor, implements the method of the grid-formation type control system applied to a photovoltaic system described in embodiment 1.
The storage medium in this embodiment may be a magnetic disk, an optical disk, a computer Memory, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a usb disk, a removable hard disk, or the like.
Example 4
The embodiment discloses a computing device, which comprises a processor and a memory for storing a program executable by the processor, wherein when the processor executes the program stored by the memory, the method of the network construction type control system applied to the photovoltaic system described in the embodiment 1 is realized.
The computing device described in this embodiment may be a desktop computer, a notebook computer, a smart phone, a PDA handheld terminal, a tablet computer, a programmable logic controller (PLC, programmable Logic Controller), or other terminal devices with processor functionality.
The above embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, so variations in shape and principles of the present invention should be covered.

Claims (10)

1. The networking control method applied to the photovoltaic system is applied to the photovoltaic system which adopts a unipolar grid-connected inverter for grid connection, and is characterized by comprising the following steps:
MPPT control link for operating photovoltaic system at maximum power point to obtain grid-connected inverter output active power reference value P ref And a DC side voltage reference value V dcref ；
A frequency-voltage control link, according to the P generated by MPPT control link ref And V dcref The amplitude V of the output reference voltage of the grid-connected inverter is obtained through control operation * And a phase angle theta, then Clark and Park conversion are carried out to obtain the dq axis component of the output reference voltage of the grid-connected inverter, and the dq axis component of the three-phase voltage of the grid-connected point is compared, and the difference value is used as the output of the frequency-voltage control link;
the current inner loop control link takes the output current of the grid-connected inverter as a control target, receives the output from the frequency-voltage control link as input, then sends the output to the PI controller, limits the output of the PI controller, superimposes the dq axis component of the instantaneous value of the three-phase current of the grid-connected point and the dq axis component of the capacitance current of the LC type filter of the photovoltaic system on the limited value to respectively obtain the dq axis component of the reference value of the output current of the grid-connected inverter, and sends the dq axis component of the output current of the grid-connected inverter to the PI controller after differencing with the dq axis component of the three-phase voltage of the grid-connected point, and the output of the PI controller is differenced with the dq axis component of the inductance voltage of the LC type filter to obtain the output of the current inner loop control link;
and the modulation control link is input as the output of the current inner loop control link, compares the generated three-phase voltage reference signal with the triangular wave signal, and obtains the trigger pulse for driving the grid-connected inverter to operate through sine pulse width modulation.
2. The method for controlling the network formation applied to the photovoltaic system according to claim 1, wherein: the photovoltaic system comprises a photovoltaic module PV, a direct-current side capacitor C dc The grid-connected inverter, the controller and the LC filter; the photovoltaic module PV is used for converting received light energy into electric energy; the DC side capacitor C dc As an intermediate unit for energy transmission, the stable direct-current side voltage can be provided for the grid-connected inverter; the Grid-connected inverter is used for receiving trigger pulses of the controller, converting direct current generated by the photovoltaic module PV into alternating current by controlling the on-off of the IGBT of the Grid-connected inverter, and transmitting power to the Grid; the controller is a core control component of the photovoltaic system, can collect voltage and current signals, controls the voltage stability of the direct current side, and generates trigger pulses to drive the IGBT of the grid-connected inverter to be turned on and off; the LC filter is used for filtering out higher harmonic components of the output voltage and current of the grid-connected inverter, so that the voltage and current output by the grid-connected inverter are more similar to sine waves, and the electric energy quality of the grid-connected inverter is improved;
wherein the controller collects three-phase voltage and phase current instantaneous value v of the grid-connected point in real time gx 、i gx The grid-connected inverter outputs three-phase voltage and phase current instantaneous value e x 、i x Voltage and current v output by photovoltaic module PV PV 、i PV And a DC side voltage real-time value V dc The method comprises the steps of carrying out a first treatment on the surface of the Where x=a, b, c.
3. The method for controlling the network formation applied to the photovoltaic system according to claim 2, wherein: in the MPPT control link, disturbance observation calculation is adoptedV collected by the method for the controller PV 、i PV Control is carried out to obtain an active power reference value P output by the grid-connected inverter ref And a DC side voltage reference value V dcref 。
4. A method of controlling a grid formation for a photovoltaic system according to claim 3, wherein: the frequency-voltage control link comprises a frequency control link and a voltage control link; the frequency control link adopts active power droop control and direct-current side voltage droop control, and the droop equation is omega=omega 0 +Δω 1 +Δω, where ω 0 Is the power frequency angular frequency omega of the power grid 0 ＝2πf 0 ，f 0 Is the power frequency of the power grid, delta omega 1 Angular frequency deviation, Δω, for active power droop control 1 ＝d P *(P ref -P LPF ) Δω is the angular frequency deviation amount obtained by the dc side voltage droop control; in active power droop control, the controller is controlled according to v gx 、i gx Calculating real-time value P of output active power of grid-connected inverter, and performing first-order low-pass filtering (omega c For the filter cut-off frequency) to obtain a filtered active power P LPF And an active power reference value P ref Taking the difference and multiplying the droop coefficient d P Obtaining the angular frequency deviation delta omega 1 After the grid-connected inverter is synchronized with the power grid, P ref ＝P LPF The output frequency of the grid-connected inverter is consistent with the frequency of the power grid; in direct-current side voltage droop control, a controller acquires V in real time dc And V is equal to dcref Comparing, correcting the difference value by a PI controller to obtain delta omega, and when the photovoltaic system operates normally, V is present dcref ＝V dc Δω=0, at which time the dc side voltage droop control is not active, and in the case of disturbance, the deviation between the dc side voltage reference value and the real time value becomes large, at which time Δω becomes small, and by decreasing the angular frequency ω, the system is accelerated to return to the maximum power operation state; because the grid-connected inverter always needs to keep the maximum power to track and run and only supports the down regulation of the output power, after the PI controller sets the limiting upper limit value of the PI controller to 0 and obtains omega, the PI controller performs the following of the omegaThe phase angle theta of the output voltage of the grid-connected inverter can be obtained through line integration; the control logic of the voltage control link is that the controller collects v according to the collection gx Calculating the phase voltage amplitude V g Reference amplitude V of phase voltage ref Comparing, and sending the difference to PI controller to obtain V * The method comprises the steps of carrying out a first treatment on the surface of the Then, θ and V * Clark and Park conversion are carried out to obtain d-axis component of output reference voltage of grid-connected inverterAnd q-axis component>D-axis component v of three-phase voltage with grid-connected point gd And q-axis component v gq And comparing, wherein the difference value is used as the output of the frequency-voltage control link.
5. The method for controlling the network formation applied to the photovoltaic system according to claim 4, wherein: in the current inner loop control link, receiving the output from the frequency-voltage control link as the input, then sending the output to the PI controller, and limiting the output of the PI controller, wherein the limited value is equal to i gx D-axis component i of (2) gd And q-axis component i gq Q-axis component ωcv of LC filter capacitance current gd And d-axis component ωCv gq Respectively obtaining d-axis components of output current reference values of grid-connected inverters after superpositionAnd q-axis component>Then, the d-axis component i of the output current of the grid-connected inverter is matched with the d-axis component i of the output current of the grid-connected inverter d And q-axis component i q After difference, the difference is sent into a PI controller, and the output of the PI controller is respectively connected with the d-axis component v of the three-phase voltage of the grid-connected point gd And q-axis component v gq Sum and match q-axis component ωLi of LC filter inductance voltage q And d-axis component ωLi d And performing difference to obtain the output of the current inner loop control link.
6. The method for controlling the network formation applied to the photovoltaic system according to claim 5, wherein: in the modulation control link, the input is the output of the current inner loop control link, and the input signal is subjected to inverse Park conversion and inverse Clark conversion to obtain the grid-connected inverter output voltage modulation signal e abc And comparing the trigger pulse with the set triangular wave to obtain the trigger pulse of the grid-connected inverter, thereby controlling the normal operation of the grid-connected inverter.
7. The method for controlling the network formation applied to the photovoltaic system according to claim 6, wherein: in the current inner loop control link, current limiting is added to the output of the PI controller, so that the output current of the grid-connected inverter can be limited during the power grid fault period, and the overcurrent condition is prevented; wherein the current is limited by I gdup 1.2I is taken n ，I gdup For the upper limit value of the d-axis component of the output current of the grid-connected inverter, I n For rated current of a photovoltaic system, the lower limit value I of d-axis component of output current of grid-connected inverter gddw take-1.2I n Upper limit value I of q-axis component of grid-connected inverter output current gqup Taking outLower limit value I of q-axis component of grid-connected inverter output current gqdw Taking 0.
8. A grid-formation control system applied to a photovoltaic system, for implementing the grid-formation control method applied to a photovoltaic system according to any one of claims 1 to 7, comprising:
the MPPT control module is used for enabling the photovoltaic system to work at a maximum power point to obtain an active power reference value P output by the grid-connected inverter ref And a DC side voltage reference value V dcref ；
Frequency-voltage control module for MPPT controlLink generated P ref And V dcref The amplitude V of the output reference voltage of the grid-connected inverter is obtained through control operation * And a phase angle theta, then Clark and Park conversion are carried out to obtain the dq axis component of the output reference voltage of the grid-connected inverter, and the dq axis component of the three-phase voltage of the grid-connected point is compared, and the difference value is used as the output of the frequency-voltage control link;
the current inner loop control module takes the output current of the grid-connected inverter as a control target, receives the output from the frequency-voltage control link as input, then sends the output to the PI controller, limits the output of the PI controller, superimposes the dq axis component of the instantaneous value of the three-phase current of the grid-connected point and the dq axis component of the capacitance current of the LC type filter of the photovoltaic system, respectively obtains the dq axis component of the reference value of the output current of the grid-connected inverter, and sends the dq axis component of the reference value of the output current of the grid-connected inverter to the PI controller after differencing with the dq axis component of the three-phase voltage of the grid-connected point, and the output of the PI controller is respectively summed with the dq axis component of the inductance voltage of the LC type filter to obtain the output of the current inner loop control link;
and the modulation control module is input into the output of a current inner loop control link, compares the generated three-phase voltage reference signal with a triangular wave signal, and obtains trigger pulses for driving the grid-connected inverter to operate through sine pulse width modulation.
9. A storage medium storing a program, wherein the program, when executed by a processor, implements the grid-formation control method applied to a photovoltaic system according to any one of claims 1 to 7.
10. A computing device comprising a processor and a memory for storing a program executable by the processor, wherein the processor, when executing the program stored in the memory, implements the grid-formation control method of any one of claims 1 to 7 for use in a photovoltaic system.
CN202310620101.8A 2023-05-29 2023-05-29 Net-structured control method and system applied to photovoltaic system Pending CN116706990A (en)

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