CN103997245A - Direct current voltage minimum fluctuation method based on power feedforward and current micro differential feedforward - Google Patents

Abstract

The present invention is a kind of DC voltage minimal ripple method to be feedovered based on power feedforward and electric current elementary errors. System passes through voltage control unit (2) first, given voltage It subtracts sampling DC voltage udc and difference input regulator G1 is obtained into output quantity i; IL is obtained by the sampling to load current in DC side load unit (7), iL passes through power feedforward unit (3), obtain electric current id1 needed for net side when power grid or load variation, id1 is fed forward to the output end of adjuster G1, it is sent into current control unit (6), is added to obtain with G1 output quantity D axis actual current id is subtracted, the input quantity of adjuster G2 is taken the difference as; Electric current id1 is sent into electric current elementary errors feed forward element (4) again, ud1 is obtained after operation, then subtract each other with the output of adjuster G2, obtained It as control amount, is sent into space vector generating unit (5), generates 6 road pulse-width signals, control DC voltage. The present invention can inhibit DC voltage fluctuation to greatest extent, and reduce the influence to current following performance.

Description

Based on the direct voltage minimal ripple method of power feedforward and the feedforward of electric current elementary errors

Technical field

The present invention relates to a kind of direct voltage minimal ripple method based on the feedforward of power feedforward and electric current elementary errors, especially a kind of suppress grid-connected converter direct current press fluctuation based on power feedforward and electric current elementary errors feed forward control method.

Background technology

Three-phase grid converter, in the field extensive use such as generate electricity by way of merging two or more grid systems of the regenerative resources such as active power filtering (APF), unified trend control (UPFC), superconducting energy storage (SMES), Electric Drive and solar energy, wind energy, is also the main jockey of the following intelligent grid technology such as electrical network energy storage, flexible power transmission and transformation, renewable energy power generation, controllable load.

The impact of the voltage ripple of power network that the control of grid-connected converter is subject to existing in actual electric network, is also subject to the disturbance that the load of grid-connected converter DC side or power supply suddenly change on a large scale.The existence of these problems all can cause the wide fluctuations that direct current is pressed, and even collapse, affects control performance, and this just requires the control of grid-connected converter DC bus will have good Immunity Performance.Generally use two closed-loop controls in, in the time that disturbance occurs, realize direct current pressure-controlled, direct voltage need to produce fluctuation, then by departure by voltage regulator and current regulator, could produce control.Instruction generation and passing time are long, cause overshoot and stabilization time inevitable larger.According to this reason, generally adopt certain feed forward control method, by the transmission of bypassing the immediate leadership of instruction, the response speed of raising.Current control algolithm mainly contains two kinds: the first is the method for feedback DC capacitor electric current, owing to having differentiation element in its feedback item, various High-frequency Interference are easily amplified, and grid-connected converter DC side is generally made busbar form, capacitance current is difficult to direct-detection, can only estimate, due to reasons such as losses, also easily produce evaluated error.Other method is that in meritorious shaft current, given place adds power feedforward item based on grid-connected converter DC side and electrical network two ends power-balance principle.The method is conducive to given value of current amplitude limit, ensures not overcurrent, also needs through current regulator but control to realize, and response speed is still under some influence.

Summary of the invention

The object of the invention is to provide a kind of direct voltage minimal ripple method based on power feedforward and the feedforward of electric current elementary errors, solve in the load of grid-connected converter DC side or line voltage mutation process, both sides energy is uneven and cause direct voltage wide fluctuations problem, and adopts the tradition inhibition method of power feedforward to be subject to the shortcoming of current regulator parameter restriction.

For addressing the above problem, the technical solution adopted in the present invention is:

Direct voltage minimal ripple method based on power feedforward and the feedforward of electric current elementary errors comprises five steps: step 1, the realization of three-phase voltage, electric current coordinate transform; Step 2, the realization of control loop voltage link; Step 3, the realization of power feedforward and Current Control; Step 4, the realization of the feedforward of electric current elementary errors and space vector controlled quentity controlled variable; Step 5, the generation of grid-connected convertor controls signal; Concrete steps are as follows:

Step 1, the realization of three-phase voltage, electric current coordinate transform link:

In the conversion of three-phase-two-phase static coordinate and rotating coordinate transformation unit, sampling three-phase line voltage, electric current, by three-phase voltage e under three phase static coordinate system _a, e _b, e _cwith three-phase current i _a, i _b, i _cby the conversion of three-phase-two-phase static coordinate, obtain e _α, e _βand i _α, i _β; In the conversion of three-phase-two-phase static coordinate and rotating coordinate transformation unit, then by e _α, e _βand i _α, i _βby rotating coordinate transformation, obtain e _d, e _qand i _d, i _q, when rotating coordinate transformation, d axle is set on three phase network voltage vector;

Step 2, the realization of control loop voltage link:

The given voltage of system deduct the direct voltage u of converter output _dcobtain difference DELTA u _dc; By Δ u _dcinput first pi regulator G ₁; G ₁transfer function be G ₁=kp ₁+ ki ₁/ s, kp ₁for proportionality coefficient, ki ₁for integral coefficient;

Step 3, the realization of power feedforward and Current Control link:

Sampling DC side load current i _lthe direct voltage u obtaining with sampling _dc; i _d1add G ₁output variable deducts electric current d axle component i again _d, send into second pi regulator G ₂input variable, obtain G ₂output variable; Wherein e _dfor the d shaft voltage component of step 1 gained, i _dfor the d shaft current component of step 1 gained; G ₂transfer function be G ₂=kp ₂₊ki ₂/ s, kp ₂for proportionality coefficient, ki ₂for integral coefficient;

Step 4, the realization of the feedforward of electric current elementary errors and space vector controlled quentity controlled variable:

By the current i obtaining by power feedforward _d1deduct i _dobtain Δ i _d; e _ddeduct k Δ i _d, then deduct G ₂output variable, obtain the input variable of space vector generating unit (5) ; Wherein k is feed-forward coefficients, k=LT _s-kp ₂, L is grid-connected converter inductance, T _sfor the sampling period, kp ₂for G ₂proportionality coefficient;

Step 5, the generation of grid-connected convertor controls signal:

By the input variable of space vector generating unit as controlled quentity controlled variable, send into space vector generating unit, space vector generating unit produces 6 road pulse-width modulation control signals, in the grid-connected power converter cells of sending into, controls direct voltage.

Beneficial effect, owing to having adopted such scheme, has overcome in traditional power feedforward control and restricted by parameter, responds slowlyer, and the larger problem of DC voltage fluctuation amplitude, realizes direct voltage minimal ripple.The present invention's proposition adds respectively the control method of power feedforward and the feedforward of electric current elementary errors at active current and the given place of space vector controlled quentity controlled variable.By showing without the comparative analysis of feedfoward control, conventional power feedfoward control and the three kinds of control methods such as feedfoward control of carrying, can not weaken current following performance based on power feedforward and electric current elementary errors feed forward control method, and response speed the fastest of realizing outer voltage, realize the minimal ripple of direct voltage.

Brief description of the drawings

Fig. 1 three-phase grid converter of the present invention equivalent model figure.

Grid-connected converter equivalent circuit diagram after Fig. 2 rotation transformation of the present invention.

Fig. 3 is of the present invention based on power feedforward and electric current elementary errors feedfoward control block diagram.

Direct voltage response diagram under Fig. 4 loading unit step disturbance of the present invention.

The response wave shape figure (without feed forward control method, kp2=5, ki2=157) of converter when Fig. 5 (a) load changing of the present invention.

The response wave shape figure (conventional power feed forward control method, kp2=5, ki2=157) of converter when Fig. 5 (b) load changing of the present invention.

The response wave shape figure of converter when Fig. 5 (c) load changing of the present invention (based on power feedforward and electric current elementary errors feed forward control method, kp2=5, ki2=15700).

The response wave shape figure (conventional power feed forward control method, kp2=15, ki2=157) of converter when Fig. 5 (d) load changing of the present invention.

The stable state oscillogram (without feed forward control method, kp2=5, ki2=157) of Fig. 6 (a) converter of the present invention.

The stable state oscillogram (conventional power feed forward control method, kp2=5, ki2=157) of Fig. 6 (b) converter of the present invention.

The stable state oscillogram (based on power feedforward and electric current elementary errors feed forward control method, kp2=5, ki2=15700) of Fig. 6 (c) converter of the present invention.

The stable state oscillogram (conventional power feed forward control method, kp2=15, ki2=157) of Fig. 6 (d) converter of the present invention.

The oscillogram of converter when Fig. 7 the present invention starts (based on power feedforward and electric current elementary errors feedfoward control, kp2=5, ki2=15700).

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described further.

Embodiment 1: the direct voltage minimal ripple method based on power feedforward and the feedforward of electric current elementary errors comprises five steps: step 1, the realization of three-phase voltage, electric current coordinate transform; Step 2, the realization of control loop voltage link; Step 3, the realization of power feedforward and Current Control; Step 4, the realization of the feedforward of electric current elementary errors and space vector controlled quentity controlled variable; Step 5, the generation of grid-connected convertor controls signal; Concrete steps are as follows:

Step 1, the realization of three-phase voltage, electric current coordinate transform link:

In the conversion of three-phase-two-phase static coordinate and rotating coordinate transformation unit 1, sampling three-phase line voltage, electric current, by three-phase voltage e under three phase static coordinate system _a, e _b, e _cwith three-phase current i _a, i _b, i _cby the conversion of three-phase-two-phase static coordinate, obtain e _α, e _βand i _α, i _β; In the conversion of three-phase-two-phase static coordinate and rotating coordinate transformation unit 1, then by e _α, e _βand i _α, i _βby rotating coordinate transformation, obtain e _d, e _qand i _d, i _q, when rotating coordinate transformation, d axle is set on three phase network voltage vector;

Step 2, the realization of control loop voltage link:

The given voltage of system deduct the direct voltage u of converter output _dcobtain difference DELTA u _dc; By Δ u _dcinput first pi regulator G ₁; G ₁transfer function be G ₁=kp ₁₊ki ₁/ s, kp ₁for proportionality coefficient, ki ₁for integral coefficient;

Step 3, the realization of power feedforward and Current Control link:

Sampling DC side load current i _lthe direct voltage u obtaining with sampling _dc; i _d1add G ₁output variable deducts electric current d axle component i again _d, send into second pi regulator G ₂input variable, obtain G ₂output variable; Wherein e _dfor the d shaft voltage component of step 1 gained, i _dfor the d shaft current component of step 1 gained; G ₂transfer function be G ₂=kp ₂+ ki ₂/ s, kp ₂for proportionality coefficient, ki ₂for integral coefficient;

Step 4, the realization of the feedforward of electric current elementary errors and space vector controlled quentity controlled variable:

By the current i obtaining by power feedforward _d1deduct i _dobtain Δ i _d; e _ddeduct k Δ i _d, then deduct G ₂output variable, obtain the input variable of space vector generating unit 5 ; Wherein k is feed-forward coefficients, k=LT _s-kp ₂, L is grid-connected converter inductance, T _sfor the sampling period, kp ₂for G ₂proportionality coefficient;

Step 5, the generation of grid-connected convertor controls signal:

By the input variable of space vector generating unit 5 as controlled quentity controlled variable, send into space vector generating unit 5, space vector generating unit 5 produces 6 road pulse-width modulation control signals, in the grid-connected power converter cells 8 of sending into, controls direct voltage.

As shown in Figure 1, the residual voltage that space vector generating unit produces is not participate in Energy Transfer to the equivalent model of three-phase grid converter, so be left in the basket.Ignore the internal resistance of inductance, according to the hree-phase symmetry of model, the present invention only provides a phase equation group of three-phase grid converter.

$e_k=L\frac{{\mathrm{di}}_k}{\mathrm{dt}}+u_{\mathrm{dc}}{d}_k-\frac{u_{\mathrm{dc}}}{3}\underset{k=a,b,c}{\mathrm{\Σ}}{d}_k---\left(1\right)$

$C\frac{{\mathrm{du}}_{\mathrm{dc}}}{\mathrm{dt}}=\underset{k=a,b,c}{\mathrm{\Σ}}{i}_k{d}_k-i_L---\left(2\right)$

E in formula _k, i _kbe electrical network phase voltage and the phase current of a phase, k=a, b, c; d _kit is the duty ratio of k phase; i _lfor DC side load current; L is three-phase grid converter inductance; C is dc-link capacitance; u _dcfor the direct voltage of sampling and obtaining.

As shown in Figure 1, need through grid-connected converter DC side and net side, energy could transmit between electrical network and the load of grid-connected converter DC side, has formed the two-stage character of grid-connected converter Energy Transfer.Due to inductance time constant, to be less than dc-link capacitance time constant many, and this makes the speed of following of the far super DC voltage control of the speed of following of Current Control, and institute thinks inhibition DC voltage fluctuation, generally according to formula (1), change d _k, first obtain required current on line side, realize power p ₁with power p ₄balance.But duty ratio now can not meet power p ₂or power p ₃equal power p ₁, even contrary.It is inconsistent that thereby electric capacity two ends power occurs, and direct voltage produces fluctuation thus.The calculating formula of each power is respectively suc as formula shown in (3)-(5).

p ₁＝e _ai _a+e _bi _b+e _ci _c (3)

p ₂＝p ₃＝u _dc(d _ai _a+d _bi _b+d _ci _c) (4)

p ₄＝u _dci _L (5)

Suppose that grid-connected converter is operated in (this is the general work state of grid-connected converter) under unity power factor, convert and rotating coordinate transformation by Isometric coordinate, three-phase grid converter equation group under three phase static coordinate system is transformed under synchronous rotating frame.If rotating coordinate system d axle is located on line voltage vector, three-phase grid converter equation group can be reduced to so.

$L=\frac{{\mathrm{di}}_d}{\mathrm{dt}}=e_d-u_d---\left(6\right)$

$L\frac{{\mathrm{di}}_q}{\mathrm{dt}}=-u_q-{\mathrm{\ωLi}}_d---\left(7\right)$

$C\frac{{\mathrm{du}}_{\mathrm{dc}}}{\mathrm{dt}}=\frac{3}{2}\·\frac{u_d}{u_{\mathrm{dc}}}{i}_d-i_L---\left(8\right)$

u _d＝u _dcd _d (9)

u _q＝u _dcd _q (10)

$p_1=\frac{3}{2}{e}_d{i}_d---\left(11\right)$

$p_2=p_3=\frac{3}{2}{u}_d---\left(12\right)$

Three-phase-two-phase static coordinate conversion of voltage and the mathematic(al) representation of rotating coordinate transformation are respectively:

Three-phase-two-phase static coordinate conversion of electric current and the mathematic(al) representation of rotating coordinate transformation are respectively:

Wherein e _a, e _b, e _cfor three phase network phase voltage, for line voltage azimuth, its rotating coordinate system d axle is set on line voltage vector.E _d, e _qbe respectively d axle component and the q axle component of three-phase voltage voltage after Isometric coordinate conversion and rotating coordinate transformation.Similarly, i _a, i _b, i _cfor three phase network phase current, for line voltage azimuth, its rotating coordinate system d axle is set on line voltage vector.I _d, i _qbe respectively d axle component and the q axle component of three-phase current through Isometric coordinate conversion and rotating coordinate transformation after-current. obtained by electrical network phase locking unit.

As shown in Figure 2, can obtain grid-connected converter equivalent circuit diagram after rotation transformation according to formula (6)-(8), in formula (6)-(8), each variable also marks in Fig. 2.Known, to direct voltage u _dccontrol can pass through d axle component i _dwith d axle controlled quentity controlled variable u _dcontrolled.Through type (6), in the time that load reduces, first needs to increase u _d, with the required current i that obtains as early as possible being calculated by formula (15) _d1.And then reduction u _d, make its maintenance and e _dequate, to stablize i _d1, now power p ₃just can equal power p ₄.So direct voltage must fluctuate, but fluctuating range and time depend on time constant and the control command given speed of inductance, electric capacity.

$G_3=i_{d1}=\frac{u_{\mathrm{dc}}{i}_L}{{3e}_d/2}---\left(15\right)$

The DC voltage fluctuation inhibition method of conventional power feedforward is according to power p ₁with power p ₄balance principle, directly feedovers the variation through type (15) of grid-connected converter DC side and line voltage in given value of current, and control block diagram is as the power feedforward unit (4) in Fig. 3.The transfer function of pi regulator is G ₂=kp+ki/s, kp, ki are respectively proportionality coefficient and integral coefficient.In patent of the present invention, the transfer function of first pi regulator is made as G ₂=kp ₁₊ki ₁/ s, the transfer function of the second pi regulator is made as G ₂=kp ₂₊ki ₂/ s.Power feedforward method has been saved the response time of controlling outer shroud, supposes that Current Control and the process of following can instantaneously complete, and direct voltage can not be subject to any interference effect.But because Current Control and the process of following need could produce controlled quentity controlled variable by current regulator, for considering other performances of Current Control, when design of Regulator, need sacrificial section rapidity, thereby weakened direct voltage stationarity.

Curent change in a switch periods can be thought linear, and if the variation of required electric current can complete in a switch periods, change formula (6), just can draw the required d axle controlled quentity controlled variable u of sudden change such as adapting to line voltage or load _d, shown in (16), (17).

$u_d=e_d-L\frac{{\mathrm{\Δi}}_d}{T_s}---\left(16\right)$

${\mathrm{\Δi}}_d=\frac{u_{\mathrm{dc}}{i}_L}{{3e}_d/2}-i_d---\left(17\right)$

Wherein, T _sit is a switch periods time.After formula (17) is line voltage or load changing, the difference of required electric current and actual current.In the time that grid-connected converter is stablized, obviously this value is zero.Formula (16), (17) result of calculation are feedovered in current regulator G ₂output variable, as shown in electric current elementary errors feed forward element (4) in Fig. 4, form the electric current elementary errors feedforward part of feed forward control method.With G ₂output variable obtain the control signal of vector generating unit (5) after subtracting each other , the 6 road pulse-width signals that finally produce by unit (5) are realized the control of the direct voltage to grid-connected converter.Due to the proportional link of current regulator, be equivalent to a part of elementary errors component, electric current elementary errors feed-forward coefficients is no longer LT so _s, but k=LT _s-current regulator G ₂proportionality coefficient kp ₂, in formula, L is grid-connected converter inductance, T _sbe a switch periods time, kp ₂for G ₂proportionality coefficient.By power feedforward and the feedforward of electric current elementary errors, bring into play each homeostasis and dynamically suppress DC voltage fluctuation performance, realize the maximum interference rejection ability of grid-connected converter direct voltage, reach the minimal ripple of direct voltage.Fig. 4 be without feedfoward control, conventional power feedfoward control and novel based on power feedforward and electric current elementary errors feedforward control, direct voltage response diagram under loading unit step disturbance, can obviously draw: under the control action based on power feedforward and the feedforward of electric current elementary errors, DC voltage fluctuation amplitude and adjustment time are obviously little a lot of than first two control method.

For verifying feasibility of the present invention, on the grid-connected converter experiment porch of 2.5kW, to verify, experiment parameter is as shown in table 1.This experiment porch adopts LCL filter, and owing to analyzing, L filter used is consistent in medium and low frequency section character with LCL filter, so adopt LCL filter not affect the correctness of checking conclusion.Experiment adopts control methods, and three kinds of control methods in experiment (without feedfoward control, conventional power feedfoward control and based on power feedforward and electric current elementary errors feedfoward control etc.) have identical voltage regulator parameter: kp ₁=3.3, ki ₁=825.

Table 1 experiment parameter table

The response wave shape figure of grid-connected converter when Fig. 5 provides load changing--A phase current and direct voltage (0.1kW-2kW).For verifying DC voltage fluctuation characteristic under three kinds of control method effects, also need to ensure that current closed-loop characteristic is basically identical.According to current closed-loop control theory analytical calculation under each control method, get kp in Fig. 5 (a), Fig. 5 (b) and Fig. 5 (c) ₂=5, three kinds of control method current regulator proportionality coefficients are consistent, the ki in Fig. 5 (a), Fig. 5 (b) ₂=157, consistent without current regulator integral coefficient in feedfoward control, conventional power feedfoward control, and the current regulator integral coefficient of scheming (c) is ki ₂=15700, be and keep consistent with first two method with the electric current loop characteristic of electric current elementary errors feedfoward control based on power feedforward, current regulator integral coefficient needs certain increase.Can find out, make used time direct voltage drop range maximum without feed forward control method, direct voltage drop range minimum during based on power feedforward and electric current elementary errors feedforward control action.And the current regulator proportionality coefficient of working as under conventional power feedforward control action is got kp ₂=15 o'clock, as shown in Fig. 5 (d), effect when direct voltage drop range can reach based on power feedforward and electric current elementary errors feedforward control action, but from Fig. 6 (c), now electric current obviously distorts, illustrate that under conventional power feedforward control action, current regulator proportionality coefficient adjustable range is limited, need sacrificial section response speed.

Fig. 6 is the stable state oscillogram of converter while adopting respectively three kinds of control methods--A phase current and direct voltage.Fig. 6 (a), Fig. 6 (b), Fig. 6 (c) and Fig. 6 (d) adopt respectively and Fig. 5 (a), Fig. 5 (b), current regulator parameter that Fig. 5 (c) is identical with Fig. 5 (d).Can find out without current distortion minimum under feedforward control action (the kp when current waveform during based on power feedforward and electric current elementary errors feedforward control action and conventional power feedforward control action ₂be all 5) current waveform aberration rate be basically identical, but slightly high when without feedfoward control.Mainly that feedforward link has been introduced the high fdrequency component in some line voltages and direct voltage, but electric current elementary errors feedforward link also may be introduced some high frequency componentses, so while adopting based on power feedforward and electric current elementary errors feed forward control method, current distortion rate also can increase to some extent, but from scheming, can find out that impact is little.And work as kp ₂=15 o'clock, the current waveform aberration rate of conventional power feedfoward control will rise rapidly.Can reach a conclusion through above-mentioned analysis, based on power feedforward and electric current elementary errors feedforward (current regulator parameter kp ₂=5, ki ₂=15700) with conventional power feedforward (current regulator parameter kp ₂=5, ki ₂=157) current following performance is basically identical, and both are more or less the same at current waveform aberration rate, but the control method based on power feedforward and the feedforward of electric current elementary errors, and DC voltage fluctuation is further suppressed.

Finally from Fig. 7--based on the startup oscillogram (A phase current and direct voltage) of power feedforward and electric current elementary errors feedfoward control downconverter, its direct voltage starts rapidly, when startup, electric current reaches rapidly rated current (amplitude limit value of setting) herein, and is controlled at amplitude limit place (system nominal current peak value is 20A).Show that the current overshoot amount based on power feedforward and electric current elementary errors feed forward control method is less, the controllability of its Current Control.

By reaching a conclusion without the Comparison of experiment results analysis of feedfoward control, conventional power feedfoward control and the three kinds of control methods such as feedfoward control of carrying: can not weaken current following performance based on power feedforward and electric current elementary errors feed forward control method, and realize the fastest of direct voltage response speed, realize the minimal ripple of direct voltage.

Claims (1)

1. the direct voltage minimal ripple method based on power feedforward and the feedforward of electric current elementary errors, it is characterized in that, the described direct voltage minimal ripple method based on power feedforward and the feedforward of electric current elementary errors comprises five steps: step 1, the realization of three-phase voltage, electric current coordinate transform link; Step 2, the realization of control loop voltage link; Step 3, the realization of power feedforward and Current Control; Step 4, the realization of the feedforward of electric current elementary errors and space vector controlled quentity controlled variable; Step 5, the generation of grid-connected convertor controls signal; Concrete steps are as follows:

Step 1, the realization of three-phase voltage, electric current coordinate transform link:

In the conversion of three-phase-two-phase static coordinate and rotating coordinate transformation unit, sampling three-phase line voltage, electric current, by three-phase voltage e under three phase static coordinate system _a, e _b, e _cwith three-phase current i _a, i _b, i _cby the conversion of three-phase-two-phase static coordinate, obtain e _α, e _βand i _α, i _β; In the conversion of three-phase-two-phase static coordinate and rotating coordinate transformation unit, then by e _α, e _βand i _α, i _βby rotating coordinate transformation, obtain e _d, e _qand i _d, i _q, when rotating coordinate transformation, d axle is set on three phase network voltage vector;

Step 2, the realization of control loop voltage link:

The given voltage of system deduct the direct voltage u of converter output _dcobtain difference DELTA u _dc; By Δ u _dcinput first pi regulator G ₁; G ₁transfer function be G ₁=kp ₁₊ki ₁/ s, kp ₁for proportionality coefficient, ki ₁for integral coefficient;

Step 3, the realization of power feedforward and Current Control link:

Sampling DC side load current i _lthe direct voltage u obtaining with sampling _dc; i _d1add G ₁output variable deducts electric current d axle component i again _d, send into second pi regulator G ₂input variable, obtain G ₂output variable; Wherein e _dfor the d shaft voltage component of step 1 gained, i _dfor the d shaft current component of step 1 gained; G ₂transfer function be G ₂=kp2+ki2/s, kp2 is proportionality coefficient, ki ₂for integral coefficient;

Step 4, the realization of the feedforward of electric current elementary errors and space vector controlled quentity controlled variable:

By the current i obtaining by power feedforward _d1deduct i _dobtain Δ i _d; e _ddeduct k Δ i _d, then deduct G ₂output variable, obtain the input variable of space vector generating unit ; Wherein k is feed-forward coefficients, k=LT _s-kp ₂, L is grid-connected converter inductance, T _sfor the sampling period, kp ₂for G ₂proportionality coefficient;

Step 5, the generation of grid-connected convertor controls signal:

By the input variable of space vector generating unit as controlled quentity controlled variable, send into space vector generating unit, space vector generating unit produces 6 road pulse-width modulation control signals, in the grid-connected power converter cells of sending into, controls direct voltage.