CN102842921A - Micro-grid multi-inverter parallel voltage control method for droop control of robust power - Google Patents

Abstract

The invention discloses a micro-grid multi-inverter parallel voltage control method for droop control of robust power. The method comprises the following steps of: specific to each inverter in a micro-grid, computing and synthesizing an inverter output reference voltage by adopting a robust power droop controller; and introducing virtual complex impedance containing a resistance component and an inductive impedance component, and keeping inverter output impedance in a pure resistance state under a power frequency condition by adopting a multi-loop voltage control method based on virtual impedance and quasi-resonance PR (Proportional-Resonant) control, thereby realizing micro-grid multi-inverter parallel running and power equation, wherein the robustness of a micro-grid parallel system on numeric value computing errors, parameter drift, noise interference and the like is enhanced. Due to the adoption of the method, the defects of larger loop current of a parallel system, non-uniform power distribution and the like caused by the inductivity of the impedance output by inverters in the conventional droop method are overcome; and the method is suitable for multi-grid parallel uniform current control in a low-voltage micro-grid.

Description

Little electrical network multi-inverter shunt voltage control method of the sagging control of robust power

Technical field

The present invention relates to little electrical network multi-inverter control field, little electrical network multi-inverter shunt voltage control method of the sagging control of particularly a kind of robust power.

Background technology

In order to excavate the potentiality of distributed power generation better, solve distributed power generation to the adverse effect that big electrical network brings, adopt the form tissue distribution formula power supply of little electrical network to insert the focus that has become the current power system research.In recent years; Operation along with the little electrical network of many experimental; Obtained certain achievement at aspects such as microgrid energy management system and the controls of power electronics interface, but a large amount of existence of the down middle low capacity distributed power source of physical condition make the little electrical network of low-voltage become the research focus day by day.

A parallel running that key issue is a multi-inverter of the little operation of power networks of low-voltage.The control strategy of single inverter has determined its output impedance characteristic, and output impedance characteristic is different, and the sagging control method of employing is also just inequality.At present, the voltage control mode of shunt chopper employing generally adopts the PI control mode.Inverter output impedance under this kind control mode generally is inductive, thereby sagging control method just adopts the sagging control mode of tradition based on emotional resistance.Yet; Inverter output resistance and line resistance can not ignore under most of situation in the little electrical network of low-voltage; Especially for low-voltage circuit; Its line resistance is much larger than circuit induction reactance, thereby is applied to the little electrical network of low-voltage based on the traditional sagging control method of perceptual output impedance, may cause situation such as the power-sharing precision is not high, circulation is bigger.

Summary of the invention

Technical problem to be solved by this invention is; Not enough to prior art; Little electrical network multi-inverter shunt voltage control method of the sagging control of a kind of robust power is provided; When solving existing method and being applied in the little electrical network of low-voltage the multi-inverter current sharing control, the problem that the power-sharing precision is not high, circulation is bigger.

For solving the problems of the technologies described above; The technical scheme that the present invention adopted is: little electrical network multi-inverter shunt voltage control method of the sagging control of a kind of robust power; Comprise little electrical network multi-inverter parallel system; Said little electrical network multi-inverter parallel system comprises the inverter that several are parallelly connected, and said inverter inserts electrical network; Said inverter comprises DC power supply, inverter circuit, LC filter circuit, A/D sample circuit, phase-locked loop circuit, controller, Drive Protecting Circuit, touch-screen; Said DC power supply, inverter circuit, LC filter circuit connect successively, and said LC filter circuit inserts little electrical network; Said A/D sample circuit input is connected with said LC filter circuit; Said controller is connected with said Drive Protecting Circuit input, A/D sample circuit output, touch-screen, phase-locked loop circuit output; Said phase-locked loop circuit input is connected with little electrical network; Said Drive Protecting Circuit drives said inverter circuit, and the step of this method is following:

1) in the starting point in each sampling period, controller passes through the A/D sample circuit to inverter output filter capacitor voltage u _oWith the filter capacitor current i _c, line current i _oSample respectively, sampled data is given controller and is handled;

2) inverter is exported LC filtering circuit capacitor voltage u _oAfter 90 ° of the phase shifts, with line current i _oMultiplying each other obtains q, inverter output LC filtering circuit capacitor voltage u _oWith line current i _oMultiplying each other obtains p, and the reactive power mean value Q in the power frequency period and the computing formula of active power average value P are following:

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}p\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}q\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o(k-\frac{N}{4})\end{array}\right.,$

Wherein, k is a sampling sequence number in the power frequency period, and N is the sampling number in the power frequency period;

3) utilize discrete Fourier transform to calculate LC filtering circuit capacitor voltage u _oEffective value U at one-period _o, output voltage amplitude reference value E ^*Deduct U _o, the difference that obtains multiply by COEFFICIENT K _e, deducting the product of P and sagging coefficient n again, the difference that obtains obtains the effective value E of reference voltage through integral operation, and its time domain expression formula is:

$E=(K_e(E^{*}-U_o)-\mathrm{nP})\frac{K_I}{s},$

Wherein, K _IBe integral coefficient, s is a complex frequency;

4) angular frequency reference value ω ^*Add that Q and sagging Coefficient m are long-pending, both sums obtain the reference angle frequencies omega through integral operation, and its time domain expression formula is:

$\mathrm{\ω}=({\mathrm{\ω}}^{*}+\mathrm{mQ})\frac{K_I}{s};$

5) by the effective value E of reference voltage and reference angle frequencies omega and phase-locked loop circuit output synchronous phase angle

Synthesized reference voltage u ^* _Ref, its computing formula is:

Wherein, phase angle

is the presynchronization signal;

6) introduce virtual resistance component and virtual inductor component, with reference voltage u ^* _RefDeduct line current i _oWith amassing of virtual impedance, obtain LC filtering circuit capacitor voltage reference value u _Ref, its computing formula is:

$u_{\mathrm{ref}}={u^{*}}_{\mathrm{ref}}-(R_D-k_L{L}_s\frac{s}{s+{\mathrm{\ω}}_c})i_o$

Wherein, ω _cBe the cut-off frequency of low pass filter, R _DBe virtual resistance value, L _sBe LC filter circuit inductance value, k _LBe the virtual inductor coefficient;

7) with u _RefAnd u _oAs the input of quasi-resonance PR controller, obtain the reference value i of LC filtering circuit capacitor electric current _Ref

8) introduce LC filtering circuit capacitor electric voltage feed forward link k _Uu _o, obtain reference current

9)

With LC filtering circuit capacitor current feedback signal k _ci _cCarry out ratio and regulate, obtain SPWM modulation wave signal D;

10) SPWM modulating wave and triangular carrier carry out the bipolarity modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, and control switch pipe S ₁～S ₄Open and turn-off.

Compared with prior art; The beneficial effect that the present invention had is: the present invention has introduced the virtual complex impedance that contains virtual resistance component and virtual induction reactance component; Virtual resistance increases the inverter output resistance, can further suppress inner circulation, improves the power-sharing effect; Virtual induction reactance has reduced inverter output induction reactance, and the output impedance of shunt chopper is designed to resistive under the power frequency condition, has guaranteed the consistency of inverter output impedance and line impedance, but has not produced corresponding power loss.Introduced the sagging controller of robust power at the little electrical network of low-voltage, power-sharing precision when further having improved the parallel running of different capabilities distributed power source, and logarithm value error of calculation, parameter drift, noise jamming etc. have stronger robustness.

Description of drawings

Fig. 1 is the little electrical network multi-inverter of an one embodiment of the invention parallel system structural representation;

Fig. 2 is little electrical network multi-inverter shunt voltage control method sketch map of the sagging control of one embodiment of the invention robust power;

Fig. 3 is the sagging controller architecture sketch map of one embodiment of the invention robust power;

Fig. 4 is the many loop voltag control block diagrams of one embodiment of the invention based on virtual complex impedance technology;

Fig. 5 adopts the two inverters parallel connection simulation waveform figure of little electrical network multi-inverter shunt voltage control method of the sagging control of robust power for one embodiment of the invention.

Embodiment

As shown in Figure 1, the little electrical network multi-inverter of one embodiment of the invention parallel system comprises the inverter that several are parallelly connected, and said inverter inserts electrical network; Said inverter comprises DC power supply, inverter circuit, LC filter circuit, A/D sample circuit, phase-locked loop circuit, dsp controller, Drive Protecting Circuit, touch-screen; Said DC power supply, inverter circuit, LC filter circuit connect successively, and said LC filter circuit inserts little electrical network; Said A/D sample circuit input is connected with said LC filter circuit; Said dsp controller is connected with said Drive Protecting Circuit input, A/D sample circuit output, touch-screen, phase-locked loop circuit output; Said phase-locked loop circuit input is connected with little electrical network; Said Drive Protecting Circuit drives said inverter circuit.Inverter circuit is IGBT switching tube S ₁～S ₄The single-phase inversion circuit of forming.Inductance L and capacitor C are formed the inverter output filter circuit, are used for the high-frequency harmonic that filtering inverter AC side produces.U _DcBe distributed power source output dc voltage, u _InvBe inverter output voltage, i _oBe line current, i _LBe inductive current, i _cBe capacitance current, u _oBe output filter capacitor voltage,

Be the presynchronization signal.A plurality of inverters are connected on the ac bus points of common connection PCC through connection line, and the decline energy in source of distribution is offered little electrical network load.DC power supply is connected with inverter circuit, and inverter circuit is connected with output filter circuit, and dsp controller is connected with A/D sample circuit, phase-locked loop pll circuit, Drive Protecting Circuit, touch-screen respectively, and Drive Protecting Circuit is connected with the switching tube of inverter circuit.Switching tube S in the output control inverter circuit of Drive Protecting Circuit ₁～S ₄Break-make.Inverter output filter capacitor voltage u _o, line current i _o, capacitance current i _cBehind the A/D sample circuit, send into dsp controller and carry out calculation process.

Little electrical network multi-inverter shunt voltage control method of the sagging control of robust power of the present invention is following:

1) in the starting point in each sampling period, dsp controller is through the A/D sample circuit, to inverter output filter capacitor voltage u _oWith the filter capacitor current i _c, line current i _oSample respectively, sampled data is given dsp controller and is handled;

2) inverter output filter capacitor voltage u _o, line current i _o, idler angular frequency reference value ω ^*, unloaded output voltage amplitude reference value E ^*As the input of the sagging controller of robust power, calculate and draw reference voltage u through the sagging control method of robust power ^* _Ref, concrete implementation procedure is following:

(1) with inverter output filter capacitor voltage u _oAfter 90 ° of the phase shifts, with line current i _oMultiplying each other obtains q, inverter output filter capacitor voltage u _oWith line current i _oMultiplying each other obtains p, and reactive power mean value Q in the power frequency period and active power average value P are asked for through mean value and calculated;

(2) utilize discrete Fourier transform DFT to calculate inverter output voltage u _oEffective value U at one-period _o, output voltage amplitude reference value E ^*Deduct U _o, the difference that obtains multiply by COEFFICIENT K _e, deduct the product of P and sagging coefficient n again, the difference that obtains is through integral operation, reference voltage effective value E;

(3) angular frequency reference value ω ^*Add that Q and sagging Coefficient m are long-pending, both sums obtain the reference angle frequencies omega through integral operation;

(4) by the effective value E of reference voltage and reference angle frequencies omega and phase-locked loop output synchronous phase angle

Synthesized reference voltage u ^* _RefPhase angle

is the presynchronization signal; When inserting little electrical network, keep and common point voltage same-phase, withdraw from after inserting little electrical network.

3) reference voltage u ^* _Ref, inverter output filter capacitor voltage u _o, line current i _o, the filter capacitor current i _cAs the input of many loop voltags controller, calculate SPWM modulating wave D through many loop voltags control algolithm, its concrete steps are:

(1) reference voltage u ^* _RefDeduct line current i _oMultiply by the long-pending of virtual impedance, obtain the Voltage Reference u of many loop voltags controller _Ref

(2) u _RefAnd u _oAs the input of quasi-resonance PR controller, its output obtains the reference value i of capacitance current _Ref

(3) introduce electric voltage feed forward link k _Uu _o, obtain reference current

(4) With capacitor current feedback signal k _ci _cCarry out ratio and regulate, obtain SPWM modulation wave signal D.

4) SPWM modulating wave and triangular carrier carry out the bipolarity modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, and control switch pipe S ₁～S ₄Open and turn-off.

Fig. 2 is little electrical network multi-inverter shunt voltage control method structured flowchart of the sagging control of a kind of robust power of invention.Inverter output filter capacitor voltage u _o, line current i _o, idler angular frequency reference value ω ^*, unloaded output voltage amplitude reference value E ^*As the input of the sagging controller of robust power, calculate and draw reference voltage u through the sagging control method of robust power ^* _RefReference voltage u ^* _Ref, inverter output voltage u _o, line current i _o, the filter capacitor current i _cAs the input of many loop voltags controller, calculate SPWM modulating wave D through many loop voltags control algolithm based on virtual complex impedance technology and quasi-resonance PR control.SPWM modulating wave and triangular carrier carry out the bipolarity modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, and control IGBT switching tube S ₁～S ₄Open and turn-off, thereby make the shunt chopper output AC voltage.

Fig. 3 is the sagging controller architecture sketch map of robust power.For the little power network line of low-voltage, its line resistance is much larger than circuit induction reactance, at this moment; If the output impedance of inverter is controlled to be resistive, then inverter output impedance and line impedance sum still are resistive, at this moment; Use traditional sagging control method, then sagging governing equation is:

$\left\{\begin{array}{c}\mathrm{\ω}={\mathrm{\ω}}^{*}+\mathrm{mQ}\\ E=E^{*}-\mathrm{nP}\end{array}\right.---\left(1\right)$

Wherein, m, n are sagging coefficient, ω ^*Be idler angular frequency reference value, E ^*Be unloaded output voltage amplitude reference value.The active power of output of shunt chopper and the expression formula of reactive power do

$\left\{\begin{array}{c}P=2(U_o{U}_{\mathrm{pcc}}\cos \mathrm{\θ}-U_{\mathrm{pcc}}^2)/R_o\\ Q=-2U_o{U}_{\mathrm{pcc}}\sin \mathrm{\θ}/R_o\end{array}\right.---\left(2\right)$

Wherein, U _o, U _PccBe respectively the effective value of inverter output filter capacitor voltage and the effective value of bus points of common connection voltage, θ is the phase difference of inverter output voltage and points of common connection voltage, R _oBe substitutional connection resistance.

In using the sagging control method of conventional power process, when the inverter parallel of a plurality of same capabilities,, then can obtain inverter parallel current-sharing effect preferably if the parameter of each inverter is identical and connection line electric parameter difference is less.But under or situation that the connection line parameter differs greatly different, use and occur when the sagging control method of conventional power can make little electrical network parallel running that system's circulation is big, inverter power distributes unequal problem in each inverter rated capacity.

The sagging control method of robust power can effectively address the above problem.As shown in Figure 3, with inverter output filter capacitor voltage effective value U _o, with E ^*Difference multiply by COEFFICIENT K _e, the value that obtains substitutes the E in the formula (1) ^*Through in the sagging control of conventional power, introducing integral element 1/s; And then realize active power by accurate pro rate, make active power output not receive the influence of equivalent output impedance, in like manner; To Reactive Power Control link structure integrator, can realize that also reactive power presses accurate pro rate.The more traditional sagging control method of the sagging control method of robust power can weaken the influence to system such as error in numerical calculation, parameter drift, noise jamming effectively, and the system that makes has stronger robustness for the existence of these extraneous factors.Simultaneously, the sagging control method of robust can also effectively weaken the influence of load variations to little line voltage.

The concrete implementation procedure of the sagging controller of robust power is following:

1) with inverter output filter capacitor voltage u _oAfter 90 ° of the phase shifts, with line current i _oMultiplying each other obtains q, filter capacitor voltage u _oWith line current i _oMultiplying each other obtains p, and reactive power mean value Q in the power frequency period and active power average value P are asked for formula through mean value and be calculated as:

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}p\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}q\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o(k-\frac{N}{4})\end{array}\right.---\left(3\right)$

Wherein, k is a sampling sequence number in the power frequency period, and N is the sampling number in the power frequency period.

2) utilize discrete Fourier transform DFT to calculate inverter output filter capacitor voltage u _oEffective value U at one-period _o, output voltage amplitude reference value E ^*Deduct U _o, the difference that obtains multiply by COEFFICIENT K _e, deduct the product of P and sagging coefficient n again, the difference that obtains is through integral operation, the effective value E of reference voltage, its time domain expression formula is:

$E=(K_e(E^{*}-U_o)-\mathrm{nP})\frac{K_I}{s}---\left(4\right)$

Wherein, m, n are sagging coefficient, ω ^*Be idler angular frequency reference value, E ^*Be unloaded output voltage amplitude reference value.It is pointed out that under the limit that the input variable of integrator should be 0, promptly has:

nP=K _e(E ^*-U _o) （5）

As far as all shunt choppers, work as parameter K _eWhen value was identical, the amount on equal sign right side was also identical in the formula (5).Be under the limit, the nP value of whole system is a constant.

3) angular frequency reference value ω ^*Add that Q and sagging Coefficient m are long-pending, both sums obtain the reference angle frequencies omega through integral operation, and expression formula does

$\mathrm{\ω}=({\mathrm{\ω}}^{*}+\mathrm{mQ})\frac{K_I}{s}---\left(6\right)$

4) by the effective value E of reference voltage and reference angle frequencies omega and phase-locked loop output synchronous phase angle

Synthesized reference voltage u ^* _RefIts computing formula is:

Wherein, Phase angle

is the presynchronization signal; When inserting little electrical network, keep and common point voltage same-phase, withdraw from after inserting little electrical network.

Shown in Figure 4 is to control block diagrams based on many loop voltags of virtual complex impedance and quasi-resonance PR control.The principal character of many loop voltag controls is: introduce the virtual complex impedance that contains resistive component and induction reactance component, and make inverter output impedance under power frequency, be pure resistive through many rings control method.Labor is following:

Concern by shown in Fig. 1, suppose that the filter inductance value is L _s, the equivalent resistance of filter inductance is R _L, inverter output voltage is u _Inv, the electric current of the filter inductance of flowing through is i _L, can get by circuit:

$L\frac{{\mathrm{di}}_L}{\mathrm{dt}}=u_{\mathrm{inv}}-u_o-R_L{i}_L---\left(8\right)$

$C\frac{{\mathrm{du}}_o}{\mathrm{dt}}=i_c=i_L-i_o---\left(9\right)$

Above two formulas of simultaneous:

$\mathrm{LC}\frac{d^2{u}_o}{\mathrm{dt}}+R_{L}C\frac{{\mathrm{du}}_o}{\mathrm{dt}}+u_o+L\frac{{\mathrm{di}}_o}{\mathrm{dt}}+R_L{i}_o=u_{\mathrm{inv}}---\left(10\right)$

In the conventional voltage control method; Mostly adopt PI to control and realize the control of inverter parallel connection output voltage; In order to realize the astatic control of inverter output voltage; Improve the control performance when little mains frequency changes simultaneously, adopted quasi-resonance PR controller to realize voltage control, the transfer function of quasi-resonance PR controller is:

$G\left(s\right)=k_{\mathrm{pr}}+\frac{{2k}_r{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{\mathrm{\ω}}^2}---\left(11\right)$

Wherein, k _PrAnd k _rBe the coefficient of quasi-resonance PR controller, ω _cCut-off frequency for low pass filter.

In order to make inverter output impedance under the power frequency condition, be resistive, and possess more high-performance, introduced virtual complex impedance

Wherein, R _DBe virtual resistance value, L _sBe output inductor value, k _LBe virtual inductor coefficient, ω _cThe introducing of low pass filter can avoid high-frequency noise to disturb effectively.Suppose that the output voltage reference value is u _Ref, can obtain thus

$u_{\mathrm{ref}}={u^{*}}_{\mathrm{ref}}-(R_D-L_D\frac{s}{s+{\mathrm{\ω}}_c})i_o={u^{*}}_{\mathrm{ref}}-Z_V\left(s\right)i_o---\left(12\right)$

The virtual complex impedance Z that contains resistive component and induction reactance component through introducing _V(s), the virtual resistance component has increased the inverter output resistance, and virtual induction reactance component has reduced inverter output induction reactance, and the output impedance that can make shunt chopper is pure resistive under the power frequency condition.

In order further to improve system control performance, introduced the capacitive current inner ring controlling unit, with the robustness of enhanced system.Simultaneously, in order to reduce the influence of voltage fluctuation, introduce electric voltage feed forward link k to current inner loop _Uu _o, k _UBe the output voltage feedback factor.Reference current

computing formula does

$i_c^{*}=(u_{\mathrm{ref}}-u_o)G\left(s\right)+k_U{u}_o---\left(13\right)$

Introduce the capacitor current feedback coefficient k _c, constituting capacitive current inner ring control, it is exported as modulation signal.Instruction current With capacitor current feedback signal k _ci _cCarry out ratio and regulate, obtain SPWM modulation wave signal D, its computing formula is:

$D=k_{\mathrm{pc}}(i_c^{*}-k_c{i}_c)---\left(14\right)$

Wherein, k _PcBe proportionality coefficient.

SPWM modulating wave that obtains and triangular carrier carry out the bipolarity modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, and control switch pipe S ₁～S ₄Open and turn-off.With the equivalence of pulse-width modulation link is the ratio gain amplifier k that a multiplication factor is proportional to DC bus-bar voltage _PWM, then through being inverter output voltage u after this link _InvInverter output voltage is carried out LC filtering, and the filtering high fdrequency component can get inverter output fundamental voltage, i.e. inverter output filter capacitor voltage u _o

Shown in Figure 5 for adopting two inverter parallel-current simulation waveform figure based on little electrical network multi-inverter shunt voltage control method of the sagging control of robust power.Suppose that the inverter capacity is 2.5kVA, inverter 1 line impedance value is 0.15+j0.02 Ω, and inverter 2 line impedance values are 0.25+j0.035 Ω, and carrier frequency is made as 12.8kHz, and load is the resistive load of 2.2kW.i ₁, i ₂Be respectively the electric current that flows through inverter 1,2 connection lines, i _HCirculation between the inverter is defined as i _H=(i ₁-i ₂)/2.0.6s have only inverter 1 isolated operation, i before _H=i ₁/ 2; 0.6s inverter 2 is incorporated system into, current i ₁Gradually become original half the.After transient process finishes, i ₁With i ₂Amplitude, phase place basic identical, i _HAlso tend to be essentially zero.

Claims (5)

1. little electrical network multi-inverter shunt voltage control method of the sagging control of robust power comprises little electrical network multi-inverter parallel system, and said little electrical network multi-inverter parallel system comprises the inverter that several are parallelly connected, and said inverter inserts little electrical network; Said inverter comprises DC power supply, inverter circuit, LC filter circuit, A/D sample circuit, phase-locked loop circuit, controller, Drive Protecting Circuit, touch-screen; Said DC power supply, inverter circuit, LC filter circuit connect successively, and said LC filter circuit inserts little electrical network; Said A/D sample circuit input is connected with said LC filter circuit; Said controller is connected with said Drive Protecting Circuit input, A/D sample circuit output, touch-screen, phase-locked loop circuit output; Said phase-locked loop circuit input is connected with electrical network; Said Drive Protecting Circuit drives said inverter circuit, it is characterized in that, the step of this method is following:

1) in the starting point in each sampling period, controller passes through the A/D sample circuit to inverter output filter capacitor voltage u _oWith the filter capacitor current i _c, line current i _oSample respectively, sampled data is given controller and is handled;

2) inverter is exported LC filtering circuit capacitor voltage u _oAfter 90 ° of the phase shifts, with line current i _oMultiplying each other obtains q, inverter output LC filtering circuit capacitor voltage u _oWith line current i _oMultiplying each other obtains p, and the reactive power mean value Q in the power frequency period and the computing formula of active power average value P are following:

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}p\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}q\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o(k-\frac{N}{4})\end{array}\right.$

Wherein, k is a sampling sequence number in the power frequency period, and N is the sampling number in the power frequency period;

3) utilize discrete Fourier transform to calculate LC filtering circuit capacitor voltage u _oEffective value U at one-period _o, output voltage amplitude reference value E ^*Deduct U _o, the difference that obtains multiply by COEFFICIENT K _e, deducting the product of P and sagging coefficient n again, the difference that obtains obtains the effective value E of reference voltage through integral operation, and its time domain expression formula is:

$E=(K_e(E^{*}-U_o)-\mathrm{nP})\frac{K_I}{s},$

Wherein, K _IBe integral coefficient, s is a complex frequency;

4) angular frequency reference value ω ^*Add that Q and sagging Coefficient m are long-pending, both sums obtain the reference angle frequencies omega through integral operation, and its time domain expression formula is:

$\mathrm{\ω}=({\mathrm{\ω}}^{*}+\mathrm{mQ})\frac{K_I}{s};$

5) by the effective value E of reference voltage and reference angle frequencies omega and phase-locked loop circuit output synchronous phase angle Synthesized reference voltage u ^* _Ref, its computing formula is:

Wherein, phase angle is the presynchronization signal;

6) introduce virtual resistance component and virtual inductor component, with reference voltage u ^* _RefDeduct line current i _oWith amassing of virtual impedance, obtain LC filtering circuit capacitor voltage reference value u _Ref, its computing formula is:

$u_{\mathrm{ref}}={u^{*}}_{\mathrm{ref}}-(R_D-k_L{L}_s\frac{s}{s+{\mathrm{\ω}}_c})i_o$

Wherein, ω _cBe the cut-off frequency of low pass filter, R _DBe virtual resistance value, L _sBe LC filter circuit inductance value, k _LBe the virtual inductor coefficient;

7) with u _RefAnd u _oAs the input of quasi-resonance PR controller, obtain the reference value i of LC filtering circuit capacitor electric current _Ref

8) introduce LC filtering circuit capacitor electric voltage feed forward link k _Uu _o, obtain reference current

9) With LC filtering circuit capacitor current feedback signal k _ci _cCarry out ratio and regulate, obtain SPWM modulation wave signal D;

10) SPWM modulating wave and triangular carrier carry out the bipolarity modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, and control switch pipe S ₁～S ₄Open and turn-off.

2. little electrical network multi-inverter shunt voltage control method of the sagging control of robust power according to claim 1 is characterized in that said controller is a dsp controller.

3. little electrical network multi-inverter shunt voltage control method of the sagging control of robust power according to claim 1 is characterized in that in the said step 7), the transfer function of quasi-resonance PR controller is:

$G\left(s\right)=k_{\mathrm{pr}}+\frac{{2k}_r{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{\mathrm{\ω}}^2}$

Wherein, k _PrAnd k _rCoefficient for quasi-resonance PR controller.

4. little electrical network multi-inverter shunt voltage control method of the sagging control of robust power according to claim 3; It is characterized in that; In the said step 8), the computing formula of reference current

is:

$i_c^{*}=(u_{\mathrm{ref}}-u_o)G\left(s\right)+k_U{u}_o,$

Wherein, k _UBe the Voltage Feedback coefficient.

5. little electrical network multi-inverter shunt voltage control method of the sagging control of robust power according to claim 1 is characterized in that in the said step 9), the computing formula of SPWM modulation wave signal D is:

$D=k_{\mathrm{pc}}(i_c^{*}-k_c{i}_c)$

Wherein, k _PcBe proportionality coefficient, k _cBe the capacitor current feedback coefficient.

Images