CN104659813A - Multiple-inverter parallel control method for quickly restraining harmonic circulating current - Google Patents

Abstract

The invention discloses a multiple-inverter parallel control method for quickly restraining harmonic circulating current. The method comprises the following steps: obtaining harmonic circulating current of output current of inverters by adopting an ip-iq algorithm, reversing the phase of the harmonic circulating current to be superposed to a voltage loop to be output to obtain an instruction of a current regulating loop, so that the harmonic circulating current of the output current of the inverters can be efficiently and quickly restrained, and the fact that the harmonic circulating current is restrained through parallel connection of multiple inverters is realized. The invention further provides a variable-window computing method for the moving average power to improve the average power calculation, reduce deviation caused by conventional fixed period calculation and improve the calculating accuracy for average power; with the moving average calculation, the average power can be calculated once in each sampling period, so that the real-time property for power calculation is greatly improved, the power sharing can be well realized through performing droop control on power, the harmonic circulating current can be further reduced. The multiple-inverter parallel control method for quickly restraining the harmonic circulating current can be widely applied to a multiple-inverter parallel control system of a microgrid, and especially suitable for a microgrid with nonlinear load operation.

Description

The multi-inverter parallel control method that a kind of quick harmonic circulating current suppresses

Technical field

The present invention relates to micro-capacitance sensor multi-inverter parallel control technology field, the multi-inverter parallel control method of particularly a kind of quick harmonic circulating current suppression.

Background technology

Increasingly serious along with global energy crisis and problem of environmental pollution, people more and more pay attention to the development and utilization of new forms of energy, new forms of energy as a kind of widely distributed high-efficiency cleaning energy, to the alternative ratio of traditional energy by increasing.At present, generation of electricity by new energy is considered to new energy technology most with prospects in the world, and various countries drop into a huge sum of money one after another and develop research, and expands the application of its market energetically.Micro-capacitance sensor, as a kind of effective means of the development and utilization of new forms of energy, can utilize distributed power source efficiently.

The key issue that micro-capacitance sensor runs is the parallel running of multi-inverter, and when parallel running owing to controlling improper or line impedance is inconsistent, can produce circulation between inverter, when being especially with nonlinear-load, between inverter, harmonic circulating current can be very large.At present, the general method of virtual impedance that adopts reduces circulation, good to first-harmonic loop current suppression effectiveness comparison, but is difficult to realize the suppression to harmonic circulating current, even can increase the aberration rate of inverter output voltage.Therefore the multi-inverter parallel control method studying a kind of quick harmonic circulating current suppression is significant.

Summary of the invention

Technical problem to be solved by this invention is, not enough for prior art, provides the multi-inverter parallel control method that a kind of quick harmonic circulating current suppresses.

For solving the problems of the technologies described above, the technical solution adopted in the present invention is: the multi-inverter parallel control method that a kind of quick harmonic circulating current suppresses, and is applicable to micro-capacitance sensor multi-inverter parallel system; Described micro-capacitance sensor multi-inverter parallel system comprises the three-phase inversion system of multiple parallel connection; Described three-phase inversion system comprises the DC energy storage electric capacity, three phase inverter bridge, the LCL filter circuit that connect successively; Described three-phase inversion system is by line impedance access micro-capacitance sensor ac bus; Comprise the following steps:

1) in the starting point in each sampling period, sample circuit is to inverter output voltage u _a, u _b, u _c, output current i _a, i _b, i _csample, then by controller, the data obtained of sampling are read, stored;

2) controller inverter output voltage u that the 1st step is collected _abe sent to digital phase-locked loop (PLL module) in real time, calculate current phase place angular frequency _oand frequency f;

3) by output current i that the 1st step collects _a, i _b, i _cfrom abc coordinate system transformation to α β coordinate system, obtain i _α, i _β, its computing formula is:

$\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{\mathrm{abc}/\mathrm{\α\β}}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]$

4) by the current i under α β coordinate system _α, i _βtransform under rotating dq coordinate system, obtain the current i under rotating coordinate system _p, i _q, its computing formula is as follows:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C_{\mathrm{\α\β}/\mathrm{dq}}\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=\left[\begin{array}{cc}\sin {\mathrm{\ω}}_{o}t& -\cos {\mathrm{\ω}}_{o}t\\ -\cos {\mathrm{\ω}}_{o}t& -\sin {\mathrm{\ω}}_{o}t\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]$

5) current i _p, i _qdC component can be decomposed into and alternating current component by current i _p, i _qafter low pass filter LPF, obtain DC component

6) by DC component under transforming to α β coordinate system, obtain the DC component electric current under α β coordinate system its computing formula is as follows:

$\left[\begin{array}{c}\stackrel{\‾}{i_{\mathrm{\α}}}\\ \stackrel{\‾}{i_{\mathrm{\β}}}\end{array}\right]=C_{\mathrm{dq}/\mathrm{\α\β}}\left[\begin{array}{c}\stackrel{\‾}{i_p}\\ \stackrel{\‾}{i_q}\end{array}\right]=\left[\begin{array}{cc}\sin {\mathrm{\ω}}_{o}t& -\cos {\mathrm{\ω}}_{o}t\\ -\cos {\mathrm{\ω}}_{o}t& -\sin {\mathrm{\ω}}_{o}t\end{array}\right]\left[\begin{array}{c}\stackrel{\‾}{i_p}\\ \stackrel{\‾}{i_q}\end{array}\right]$

7) current i is used again _α, i _βbecome and deduct DC component electric current obtain the alternating current component under α β coordinate system its computing formula is as follows:

$\left\{\begin{array}{c}\widetilde{i_{\mathrm{\α}}}=i_{\mathrm{\α}}-\stackrel{\‾}{i_{\mathrm{\α}}}\\ \widetilde{i_{\mathrm{\β}}}=i_{\mathrm{\β}}-\stackrel{\‾}{i_{\mathrm{\β}}}\end{array}\right.$

8) by inverter output voltage u that the 1st step collects _a, u _b, u _cfrom abc coordinate system transformation to α β coordinate system, obtain u _α, u _β, its computing formula is:

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=C_{\mathrm{abc}/\mathrm{\α\β}}\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]$

9) the output current i that the 3rd step obtains is utilized _α, i _βwith the output voltage u that the 8th step obtains _α, u _β, calculate instantaneous active power p and reactive power q, its computing formula is as follows:

$\left[\begin{array}{c}p\\ q\end{array}\right]=\left[\begin{array}{cc}{u}_{\mathrm{\α}}& u_{\mathrm{\β}}\\ u_{\mathrm{\β}}& -u_{\mathrm{\α}}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]$

10) the instantaneous active power p calculated and reactive power q is sent into change window sliding average power and calculate module, calculate average active power P and reactive power Q, and the current average active power P that calculates and reactive power Q are stored, use in order to calculating next time.Its computing formula is as follows:

$\left\{\begin{array}{c}P\left(k\right)=P(k-1)+\frac{1}{N}(p\left(k\right)-p(k-N))\\ Q\left(k\right)=Q(k-1)+\frac{1}{N}(q\left(k\right)-q(k-N))\end{array}\right.$

Wherein k is present sample number of times, and N is the total sampling number in a grid cycle, and is directly proportional to incoming frequency;

11) utilize the average active power P calculated and reactive power Q, calculate reference voltage amplitude E and angular frequency by power droop control, specific formula for calculation is as follows:

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

Wherein m, n are respectively meritorious and idle sagging coefficient, and concrete value is determined by the meritorious capacity of three-phase inversion system and reactive capability;

12) phase place that the reference voltage amplitude E utilizing the 11st step to calculate and angular frequency and the 2nd step obtain carry out three-phase voltage synthesis and obtain three-phase reference voltage its computing formula is as follows:

13) three-phase reference voltage obtained will be synthesized under transforming to α β coordinate system, obtain the reference voltage under α β coordinate system its computing formula is:

$\left[\begin{array}{c}{u}_{\mathrm{\α}}^{*}\\ u_{\mathrm{\β}}^{*}\end{array}\right]=C_{\mathrm{abc}/\mathrm{\α\β}}\left[\begin{array}{c}{u}_a^{*}\\ u_b^{*}\\ u_c^{*}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{u}_a^{*}\\ u_b^{*}\\ u_c^{*}\end{array}\right]$

14) by i that the 3rd step obtains _α, i _β, be multiplied by virtual resistance, then the reference voltage that is added to on, obtain the voltage reference value of quasi-resonance PR control voltage outer shroud the reference current of current inner loop is obtained after being controlled by quasi-resonance PR

15) alternating current component under the α β coordinate system the 7th step obtained phase place negate, the reference current of the current inner loop that is added to on, obtain reference current

16) with reference to electric current under transforming to abc coordinate system, obtain the reference current of dead-beat current control the duty ratio D of three phase inverter bridge drive singal is obtained through track with zero error _a, D _b, D _c.Be sent to Drive Protecting Circuit, produce drive singal, be used for driving inverter.

Compared with prior art, the beneficial effect that the present invention has is: the outer voltage that is added to after anti-phase for the harmonic current of inverter output current exports by the multi-inverter parallel control method that the quick harmonic circulating current that the present invention proposes suppresses, obtain the instruction of current inner loop, thus efficiently, rapidly inhibit harmonic circulating current.In addition, the present invention proposes the average power that a kind of computational methods becoming window sliding average power are come needed for rated output droop control, the proposition that moving average calculates improves the real-time of power calculation, makes to calculate an average power in each sampling period; The proposition of " change window " decreases fixed cycle and calculates the error introduced, and improves the accuracy that average power calculates, thus achieves the power-sharing of multi-inverter parallel, reduce further harmonic circulating current.The harmonic circulating current that present invention achieves micro-capacitance sensor multi-inverter parallel suppresses, and can be widely applied in micro grid control system.

Accompanying drawing explanation

Fig. 1 is one embodiment of the invention multi-inverter parallel structural representation;

Fig. 2 is the multi-inverter parallel control method schematic diagram that the quick harmonic circulating current of one embodiment of the invention suppresses;

Fig. 3 is one embodiment of the invention single-phase phase-locked loop computing block diagram;

Fig. 4 is two inverter parallel current simulations oscillograms of the multi-inverter parallel control method that one embodiment of the invention adopts quick harmonic circulating current to suppress.

The two inverter parallel circulation harmonic analysis result figure that Fig. 5 (a) is traditional droop control method; Fig. 5 (b) is for adopting the circulation harmonic analysis result figure of the inventive method.

Embodiment

Fig. 1 is one embodiment of the invention multi-inverter parallel structural representation, comprises three-phase inversion system, control system, line impedance, micro-capacitance sensor ac bus, threephase load; Described three-phase inversion system comprises DC energy storage electric capacity, three phase inverter bridge, LCL filter circuit; DC energy storage electric capacity, three phase inverter bridge, LCL filter circuit, line impedance, micro-capacitance sensor ac bus, threephase load connect successively.Control system comprises dsp controller, A/D sample circuit, phase-locked loop module and Drive Protecting Circuit.

Fig. 2 is the multi-inverter parallel control method schematic diagram that the quick harmonic circulating current of one embodiment of the invention suppresses, suppress part primarily of harmonic circulating current, become the calculating of window sliding average power module, phase-locked loop module, power droop control module, virtual resistance module, quasi-resonance PR control module and dead-beat current control module composition, the multi-inverter parallel control method that concrete quick harmonic circulating current suppresses comprises the following steps:

1) in the starting point in each sampling period, sample circuit is to inverter output voltage u _a, u _b, u _c, output current i _a, i _b, i _csample, then by controller, the data obtained of sampling are read, stored;

2) controller inverter output voltage u that the 1st step is collected _abe sent to digital phase-locked loop (PLL module) in real time, calculate current phase place angular frequency _oand frequency f;

3) by output current i that the 1st step collects _a, i _b, i _cfrom abc coordinate system transformation to α β coordinate system, obtain i _α, i _β, its computing formula is:

$\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{\mathrm{abc}/\mathrm{\α\β}}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]$

4) by the current i under α β coordinate system _α, i _βtransform under rotating dq coordinate system, obtain the current i under rotating coordinate system _p, i _q, its computing formula is as follows:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C_{\mathrm{\α\β}/\mathrm{dq}}\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=\left[\begin{array}{cc}\sin {\mathrm{\ω}}_{o}t& -\cos {\mathrm{\ω}}_{o}t\\ -\cos {\mathrm{\ω}}_{o}t& -\sin {\mathrm{\ω}}_{o}t\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]$

5) current i _p, i _qdC component can be decomposed into and alternating current component by current i _p, i _qafter low pass filter LPF, obtain DC component

6) by DC component under transforming to α β coordinate system, obtain the DC component electric current under α β coordinate system its computing formula is as follows:

$\left[\begin{array}{c}\stackrel{\‾}{i_{\mathrm{\α}}}\\ \stackrel{\‾}{i_{\mathrm{\β}}}\end{array}\right]=C_{\mathrm{dq}/\mathrm{\α\β}}\left[\begin{array}{c}\stackrel{\‾}{i_p}\\ \stackrel{\‾}{i_q}\end{array}\right]=\left[\begin{array}{cc}\sin {\mathrm{\ω}}_{o}t& -\cos {\mathrm{\ω}}_{o}t\\ -\cos {\mathrm{\ω}}_{o}t& -\sin {\mathrm{\ω}}_{o}t\end{array}\right]\left[\begin{array}{c}\stackrel{\‾}{i_p}\\ \stackrel{\‾}{i_q}\end{array}\right]$

7) current i is used again _α, i _βbecome and deduct DC component electric current obtain the alternating current component under α β coordinate system its computing formula is as follows:

$\left\{\begin{array}{c}\widetilde{i_{\mathrm{\α}}}=i_{\mathrm{\α}}-\stackrel{\‾}{i_{\mathrm{\α}}}\\ \widetilde{i_{\mathrm{\β}}}=i_{\mathrm{\β}}-\stackrel{\‾}{i_{\mathrm{\β}}}\end{array}\right.$

8) by inverter output voltage u that the 1st step collects _a, u _b, u _cfrom abc coordinate system transformation to α β coordinate system, obtain u _α, u _β, its computing formula is:

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=C_{\mathrm{abc}/\mathrm{\α\β}}\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]$

9) the output current i that the 3rd step obtains is utilized _α, i _βwith the output voltage u that the 8th step obtains _α, u _β, calculate instantaneous active power p and reactive power q, its computing formula is as follows:

$\left[\begin{array}{c}p\\ q\end{array}\right]=\left[\begin{array}{cc}{u}_{\mathrm{\α}}& u_{\mathrm{\β}}\\ u_{\mathrm{\β}}& -u_{\mathrm{\α}}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]$

10) the instantaneous active power p calculated and reactive power q is sent into change window sliding average power and calculate module, calculate average active power P and reactive power Q, and the current average active power P that calculates and reactive power Q are stored, use in order to calculating next time.Its computing formula is as follows:

$\left\{\begin{array}{c}P\left(k\right)=P(k-1)+\frac{1}{N}(p\left(k\right)-p(k-N))\\ Q\left(k\right)=Q(k-1)+\frac{1}{N}(q\left(k\right)-q(k-N))\end{array}\right.$

Wherein k is present sample number of times, and N is the total sampling number in a grid cycle, and is directly proportional to incoming frequency;

11) utilize the average active power P calculated and reactive power Q, calculate reference voltage amplitude E and angular frequency by power droop control, specific formula for calculation is as follows:

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

Wherein m, n are respectively meritorious and idle sagging coefficient, and concrete numerical value is determined by the meritorious capacity of each inverter and reactive capability;

12) phase place that the reference voltage amplitude E utilizing the 11st step to calculate and angular frequency and the 2nd step obtain carry out three-phase voltage synthesis and obtain three-phase reference voltage its computing formula is as follows:

13) three-phase reference voltage obtained will be synthesized under transforming to α β coordinate system, obtain the reference voltage under α β coordinate system its computing formula is:

$\left[\begin{array}{c}{u}_{\mathrm{\α}}^{*}\\ u_{\mathrm{\β}}^{*}\end{array}\right]=C_{\mathrm{abc}/\mathrm{\α\β}}\left[\begin{array}{c}{u}_a^{*}\\ u_b^{*}\\ u_c^{*}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{u}_a^{*}\\ u_b^{*}\\ u_c^{*}\end{array}\right]$

14) by i that the 3rd step obtains _α, i _β, be multiplied by virtual resistance, then the reference voltage that is added to on, obtain the voltage reference value of quasi-resonance PR control voltage outer shroud the reference current of current inner loop is obtained after being controlled by quasi-resonance PR

15) alternating current component under the α β coordinate system the 7th step obtained phase place negate, the reference current of the current inner loop that is added to on, obtain reference current

16) with reference to electric current under transforming to abc coordinate system, obtain the reference current of dead-beat current control the duty ratio D of three phase inverter bridge drive singal is obtained through track with zero error _a, D _b, D _c.Be sent to Drive Protecting Circuit, produce drive singal, be used for driving inverter.

Fig. 3 is one embodiment of the invention single-phase phase-locked loop computing block diagram, u in figure _afor line voltage, by line voltage u _adelayed phase 90 ° to construct β phase virtual orthographic signal u _β, thus construct two-phase virtual orthographic system, obtain two-phase quadrature voltage u _α, u _β, then to two-phase quadrature voltage u _α, u _βdo α β/dq coordinate transform, obtain micro-capacitance sensor magnitude of voltage d axle component u _dwith micro-capacitance sensor magnitude of voltage q axle component u _q, by u _dreference value be set to 0, PI control is carried out to it, the angular frequency of current electric grid can be obtained, then obtain the phase place of current electric grid through integration

Fig. 4 is two inverter parallel current simulations oscillograms of the multi-inverter parallel control method that one embodiment of the invention adopts quick harmonic circulating current to suppress.Assuming that inverter capacity is 9kVA, inverter 1 line impedance value is 0.2+j0.03 Ω, and inverter 2 line impedance value is 0.25+j0.04 Ω, and carrier frequency is set to 10kHZ, and load is the resistive load of 6.6kW, i _a1, i _a2be respectively the A phase current flowing through inverter 1,2, i _aHfor the A phase circulation between inverter, be defined as i _aH=(i _a1-i _a2)/2, only have inverter 1 isolated operation, i before _aH=i _a1/ 2; After 0.5s, inverter 2 is incorporated to system, current i _a1gradually become original half, after transient process terminates, i _a1with i _a2amplitude, phase place substantially identical, i _aHalso zero is tended to be essentially.

Fig. 5 is two inverter parallel circulation harmonic analysis comparison diagrams of one embodiment of the invention multi-inverter parallel control method of adopting quick harmonic circulating current to suppress and traditional droop control method.Wherein scheming a is traditional control method circulation harmonic analysis result, figure b is quick harmonic circulating current inhibitory control method circulation harmonic analysis result proposed by the invention, by the contrast of two figure, obviously can see that after adopting quick harmonic circulating current inhibitory control method proposed by the invention, the high-frequency harmonic content of harmonic circulating current obviously reduces.

Claims (5)

1. a multi-inverter parallel control method for quick harmonic circulating current suppression, is applicable to micro-capacitance sensor multi-inverter parallel system; Described micro-capacitance sensor multi-inverter parallel system comprises the three-phase inversion system of multiple parallel connection; Described three-phase inversion system comprises the DC energy storage electric capacity, three phase inverter bridge, the LCL filter circuit that connect successively; Described three-phase inversion system is by line impedance access micro-capacitance sensor ac bus; It is characterized in that, comprise the following steps:

1) in the starting point in each sampling period, to three-phase inversion system output voltage u _a, u _b, u _c, output current i _a, i _b, i _csample;

2) by described three-phase inversion system output voltage u _abe sent to digital phase-locked loop, calculate current phase place angular frequency _oand frequency f; By described three-phase inversion system output voltage u _a, u _b, u _cfrom abc coordinate system transformation to α β coordinate system, obtain the voltage u under α β coordinate system _α, u _β; By three-phase inversion system output current i _a, i _b, i _cfrom abc coordinate system transformation to α β coordinate system, obtain the current i under α β coordinate system _α, i _β;

3) by the current i under α β coordinate system _α, i _βtransform under rotating dq coordinate system, obtain the current i under rotating coordinate system _p, i _q;

4) by current i _p, i _qafter low pass filter, obtain DC component

5) by DC component under transforming to α β coordinate system, obtain DC component electric current

6) current i is used _α, i _βdeduct DC component electric current obtain the alternating current component under α β coordinate system

7) current i is utilized _α, i _β, voltage u _α, u _βcalculate instantaneous active power p and the reactive power q of three-phase inversion system:

$\left[\begin{array}{c}p\\ q\end{array}\right]=\left[\begin{array}{cc}{u}_{\mathrm{\α}}& u_{\mathrm{\β}}\\ u_{\mathrm{\β}}& -u_{\mathrm{\α}}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right];$

8) instantaneous active power p and reactive power q is utilized to calculate average active power P and reactive power Q:

$\left\{\begin{array}{c}P\left(k\right)=P(k-1)+\frac{1}{N}(p\left(k\right)-p(k-N))\\ Q\left(k\right)=Q(k-1)+\frac{1}{N}(q\left(k\right)-q(k-N))\end{array}\right.;$

Wherein k is present sample number of times; N is the total sampling number in a grid cycle; P (k) is the instantaneous active power of kth time sampling; Q (k) is the instantaneous reactive power of kth time sampling; P (k) is the average active power of kth time sampling; The average reactive power of Q (k) kth time sampling;

9) utilize described average active power P and reactive power Q, calculate reference voltage amplitude E and angular frequency by power droop control:

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

Wherein E ^*, ω ^*represent the rated output voltage amplitude of three-phase inversion system and specified output angle frequency respectively, m, n are respectively meritorious and idle sagging coefficient;

10) reference voltage amplitude E, angular frequency and phase place is utilized carry out three-phase voltage synthesis, obtain three-phase reference voltage

11) three-phase reference voltage obtained will be synthesized under transforming to α β coordinate system, obtain the reference voltage under α β coordinate system

12) by the current i under α β coordinate system _α, i _βbe multiplied by virtual resistance, then the reference voltage that is added to on, obtain the voltage reference value of quasi-resonance PR control voltage outer shroud the reference current of current inner loop is obtained after being controlled by quasi-resonance PR

13) by the alternating current component under α β coordinate system phase place negate, the reference current of the current inner loop that is added to on, obtain reference current

14) with reference to electric current under transforming to abc coordinate system, obtain the reference current of dead-beat current control the duty ratio D of three phase inverter bridge drive singal is obtained through track with zero error _a, D _b, D _c, by duty ratio D _a, D _b, D _cbe sent to Drive Protecting Circuit, produce drive singal, be used for driving three-phase inversion system.

2. the multi-inverter parallel control method of quick harmonic circulating current suppression according to claim 1, is characterized in that, described step 2) in, the current i under α β coordinate system _α, i _βand the voltage u under α β coordinate system _α, u _βcomputing formula is respectively:

$\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}1-\frac{1}{2}& -\frac{1}{2}\\ 0\frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right];$

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}1-\frac{1}{2}& -\frac{1}{2}\\ 0\frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right].$

3. the multi-inverter parallel control method of quick harmonic circulating current suppression according to claim 1, is characterized in that, described step 3) in, the current i under rotating coordinate system _p, i _qcomputing formula is:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]\left[\begin{array}{cc}\sin {\mathrm{\ω}}_{o}t& -\cos {\mathrm{\ω}}_{o}t\\ -\cos {\mathrm{\ω}}_{o}t& -\sin {\mathrm{\ω}}_{o}t\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right].$

4. the multi-inverter parallel control method of quick harmonic circulating current suppression according to claim 1, is characterized in that, described step 5) in, DC component electric current computing formula is:

$\left[\begin{array}{c}\stackrel{\‾}{i_{\mathrm{\α}}}\\ \stackrel{\‾}{i_{\mathrm{\β}}}\end{array}\right]=\left[\begin{array}{cc}\sin {\mathrm{\ω}}_{o}t& -\cos {\mathrm{\ω}}_{o}t\\ -\cos {\mathrm{\ω}}_{o}t& -\sin {\mathrm{\ω}}_{o}t\end{array}\right]\left[\begin{array}{c}\stackrel{\‾}{i_p}\\ \stackrel{\‾}{i_q}\end{array}\right].$

5. the multi-inverter parallel control method of quick harmonic circulating current suppression according to claim 1, is characterized in that, described step 8) in, the computing formula of N is: N=round (λ f); Wherein λ is coefficient correlation, and the value of λ is the ratio of sample frequency and mains frequency.