CN103560658B - The cyclic swing suppressing method of photovoltaic power generation system current in direct-current grid - Google Patents

Abstract

The cyclic swing suppressing method of photovoltaic power generation system current in direct-current grid, belong to field of conversion of electrical energy, the cyclic swing suppressing method being specifically related in direct-current grid photovoltaic power generation system current, solve the problem that the cyclic swing of the photovoltaic cell electric current that there is photovoltaic generating system when existing photovoltaic generation direct-current grid connects load is big, device for power switching dutycycle in booster circuit is input to booster circuit by the present invention, the control signal of device for power switching in booster circuit is obtained by the pulse width modulation module in booster circuit, and by the device for power switching in this signal input to booster circuit, complete once to the suppression of the cyclic swing of photovoltaic power generation system current in direct-current grid. the present invention is suitable in suppressing the cyclic swing of photovoltaic power generation system current direct-current grid.

Description

The cyclic swing suppressing method of photovoltaic power generation system current in direct-current grid

Technical field

The invention belongs to field of conversion of electrical energy, the cyclic swing suppressing method being specifically related in direct-current grid photovoltaic power generation system current.

Background technology

Photovoltaic power generation technology becomes the effective way solving mankind's energy scarcity and environmental pollution Double jeopardy because it has the advantage such as cleaning, energy near infinite and becomes study hotspot. And based on the photovoltaic generation source integrated form of direct-current grid without substantial amounts of AC inverter, save great amount of cost, effectively reduce system complexity, it is shown that huge development potentiality and wide application prospect.

When photovoltaic generation direct-current grid connects single-phase DC-ac inverter even load, the cyclic fluctuation of DC bus-bar voltage can be produced, cause photovoltaic generating system cannot be continuously in maximum power point, reduce system effectiveness. Existing for, in the achievement in research of photovoltaic generating system, controlling technology with MPPT maximum power point tracking on the one hand and attach most importance to. MPPT technique can be divided into following a few class: determining voltage method, disturbance observation method, conductance increment method, based on the MPPT method of impedance matching and based on the method such as modern control theory and Based Intelligent Control. Additionally, literature research is also had to control technology for the MPPT of the photovoltaic generating system of direct-current grid, utilize the feature that dc bus remains unchanged, it is obtained in that output and the linear relationship of dutycycle in DC transfer circuit, thus the output voltage of photovoltaic cell only need to be detected or its output just can be controlled by electric current, thus eliminating a part of sensor. But above-mentioned achievement is all output as research emphasis with the maximum power of photovoltaic cell based on DC-DC circuit, and the problem that the cyclic swing of unresolved DC voltage is big, cause photovoltaic generating system cannot be continuously in maximum power point, reduce system effectiveness.

It is in the closed loop control of general DC-DC circuit on the other hand, wherein proportional-integration control, Sliding mode variable structure control, feedback linearization method, passive coherent locating, Self Adaptive Control, internal model control and fuzzy, ANN Control etc. The studies above achievement is all constant in target with VD, the problem that the cyclic swing of same unresolved DC voltage is big, causes photovoltaic generating system cannot be continuously in maximum power point, reduces system effectiveness.

Summary of the invention

The problem that the cyclic swing of the photovoltaic cell electric current of photovoltaic generating system is big is there is, it is proposed that the cyclic swing suppressing method of photovoltaic power generation system current in direct-current grid when the present invention is to solve the connection load of existing photovoltaic generation direct-current grid.

The cyclic swing suppressing method of photovoltaic power generation system current in direct-current grid of the present invention, described photovoltaic generating system include moving average filter, pi controller, photovoltaic cell current collection circuit, photovoltaic cell, booster circuit, adder, with the repetitive controller of feedforward, No. two adders and No. three adders;

Photovoltaic cell current collection circuit is for gathering the current signal of photovoltaic cell output, the signal output part that gathers of photovoltaic cell current collection circuit connects an input of No. three adders, the input of the set-point that another input is photovoltaic cell electric current of No. three adders, the outfan of No. three adders is simultaneously connected with the filtering signal input of moving average filter and an input of No. two adders, the filtered signal outfan of moving average filter is simultaneously connected with another input of No. two adders and the signal input part of pi controller, the signal output part of pi controller connects a signal input part of an adder, the outfan of No. two adders connects the signal input part of the repetitive controller with feedforward, the signal output part of the repetitive controller with feedforward connects another signal input part of an adder,

Booster circuit also includes filter inductance, diode, switching device and pulse width modulation module, one power supply signal outfan of photovoltaic cell connects one end of filter inductance, the other end of filter inductance is simultaneously connected with the negative electrode of diode and the power input of switching device, the power take-off of switching device connects another power supply signal outfan of photovoltaic cell, the drive end of the modulation signal output part connecting valve device of pulse width modulation module; The signal output part of a number adder connects the modulation signal input part of the pulse width modulation module of booster circuit;

It is characterized in that: based on the cyclic swing suppressing method of photovoltaic power generation system current in the direct-current grid of above-mentioned photovoltaic generating system, concretely comprising the following steps of the method:

Step one, set photovoltaic cell electric current set-point, by photovoltaic cell current collection circuit gather photovoltaic cell electric current, it is thus achieved that the actual value of photovoltaic cell electric current;

Step 2, the set-point of the photovoltaic cell electric current in step one is deducted the actual value of photovoltaic cell electric current, it is thus achieved that the set-point of photovoltaic cell electric current and the poor x (k) of actual value; Wherein, k is for calculating period index;

Step 3, by the poor x (k) of the set-point of photovoltaic cell electric current obtained in step 2 and actual value, be input to the discretization equation of moving average filter, it is thus achieved that moving average filter is at the output valve y in this calculating cycle_f(k);

The discretization equation of moving average filter is:

$y_f\left(k\right)=y_f(k-1)+\frac{\[x\left(k\right)-{\mathrm{\λ}}_1\left(0\right)\]}{N}$

Wherein λ₁(0) it is array λ₁First element value, described λ₁Being the array for storing x (k), its width is N, N is the positive integer more than 100, y_f(k-1) output valve of the moving average filter in cycle is calculated for kth-1;

Step 4, renewal array λ₁In each element value: make λ₁(i)=λ₁(i+1), wherein, i is array λ₁The label of each element, 0≤i≤N-2, it is judged that whether i is equal to N-2, if the determination result is YES, then make λ (N-1)=x (k), perform step 5; Otherwise, step 4 one is performed;

Step 4 one, make i=i+1, return and perform step 4;

Step 5, the set-point of photovoltaic cell electric current obtained by step 2 and the poor x (k) of actual value deduct the moving average filter of step 3 acquisition at the output valve y in this calculating cycle_f(k), it is thus achieved that the cyclic swing component of x (k)

Step 6, by output valve y in this calculating cycle of the moving average filter that obtains in step 3_fK () is input to the discretization equation of pi controller, it is thus achieved that pi controller is at the output valve y in this calculating cycle_PI(k);

The discretization equation of pi controller is:

y_PI(k)=y_PI(k-1)+K_P[y_f(k)-y_f(k-1)]+K_IT_Sy_f(k)]

Wherein, y_PI(k-1) output valve of the pi controller in cycle, K is calculated for kth-1_PFor proportionality coefficient, K_IFor integral coefficient, T_SIt is calculate periodic quantity;

Step 7, the cyclic swing component of x (k) that will obtain in step 5It is input to the discretization equation of repetitive controller, it is thus achieved that repetitive controller is at the output valve y in this calculating cycle_RC(k); Again by y_RC(k) withIt is added, it is thus achieved that repetitive controller is at the output valve y in this calculating cycle_RC1(k);

The discretization equation of repetitive controller is: $y_{\mathrm{RC}}\left(k\right)={\mathrm{\λ}}_2\left(a\right)+\tilde{x}\left(k\right),$

Wherein, λ₂A () is array λ₂The a element value, λ₂For being used for storing the array of repetitive controller output valve, described array λ₂Width be M; 0≤a≤M, and a is integer, M is the positive integer more than 100;

Step 8, to array λ₂In element be updated, make λ₂(a)=y_RCK (), it is judged that whether a is more than M, if the determination result is YES, then makes a=a-M, performs step 9, otherwise, perform step Aug. 1st;

Step Aug. 1st, make a=a+1, perform step 9;

Step 9, the output valve y that step 6 is obtained_PIK output valve y that () and step 7 obtain_RC1K () is added, it is thus achieved that the dutycycle of device for power switching in booster circuit;

Step 10, dutycycle step 9 obtained are input to booster circuit, the control signal of device for power switching in booster circuit is obtained by the pulse width modulation module in booster circuit, and by the device for power switching in this signal input to booster circuit, complete once to the suppression of the cyclic swing of photovoltaic power generation system current in direct-current grid.

The present invention combines the method with the repetitive controller feedovered by the photovoltaic cell electric current usage ratio integral controller in the photovoltaic generating system of linked direct-current grid, ensure that the floating of photovoltaic cell electric current is run, and then effectively inhibit the photovoltaic generating system that DC voltage cyclic fluctuation causes to export the fluctuation of electric current, so that photovoltaic cell is in lasting maximum generation power points, improve its work efficiency. It addition, the present invention adopts total digitalization mode to realize, it is not necessary to extra increase detection or other hardware circuit, it is achieved relatively easy, and its work efficiency improves 10% compared with the conventional method.

Accompanying drawing explanation

Fig. 1 is the electrical structure schematic diagram of direct-current grid;

In figure, A is photovoltaic generating system, and B is dc bus, and C is unidirectional inversion load, and D is energy-storage system of accumulator;

Fig. 2 is the photovoltaic generating system electrical structure schematic diagram of adoption rate integral controller;

In figure, a is booster circuit, and b is photovoltaic cell, and c is photovoltaic cell current collection circuit, and d is adder, and e is pi controller;

Fig. 3 is the DC bus-bar voltage simulation waveform figure of direct-current grid;

The photovoltaic cell current simulations oscillogram of the photovoltaic generating system of Fig. 4 adoption rate integral controller;

The photovoltaic cell voltage simulation waveform figure of the photovoltaic generating system of Fig. 5 adoption rate integral controller;

The photovoltaic power simulation waveform figure of the photovoltaic generating system of Fig. 6 adoption rate integral controller;

Fig. 7 is the electrical structure block diagram of photovoltaic generating system of the present invention;

Fig. 8 is the cyclic swing suppressing method flow chart of photovoltaic power generation system current in direct-current grid of the present invention;

Fig. 9 is the photovoltaic cell current simulations oscillogram of the photovoltaic generating system adopting the method for the invention;

In figure, 0.1s to 0.2s is the waveform of adoption rate integral controller, and 0.2s to 0.3s is the waveform adopting the method for the invention;

Figure 10 is the photovoltaic cell voltage simulation waveform figure of the photovoltaic generating system adopting the method for the invention;

In figure, 0.1s to 0.2s is the waveform of adoption rate integral controller, and 0.2s to 0.3s is the waveform adopting the method for the invention;

Figure 11 is the photovoltaic power simulation waveform figure of the photovoltaic generating system adopting the method for the invention;

In figure, 0.1s to 0.2s is the waveform of adoption rate integral controller, and 0.2s to 0.3s is the waveform adopting the method for the invention.

Detailed description of the invention

Detailed description of the invention one, in conjunction with Fig. 7 and Fig. 8, present embodiment is described, the cyclic swing suppressing method of photovoltaic cell electric current in direct-current grid described in present embodiment, described photovoltaic generating system include moving average filter 1, pi controller 2, photovoltaic cell current collection circuit 3, photovoltaic cell 4,5, adder 6 of booster circuit, with feedforward 7, No. two adders 8 of repetitive controller and No. three adders 9;

Photovoltaic cell current collection circuit 3 is for gathering the current signal of photovoltaic cell 4 output, the signal output part that gathers of photovoltaic cell current collection circuit 3 connects an input of No. three adders 9, the input of the set-point that another input is photovoltaic cell electric current of No. three adders 9, the outfan of No. three adders 9 is simultaneously connected with the filtering signal input of moving average filter 1 and an input of No. two adders 8, the filtered signal outfan of moving average filter 1 is simultaneously connected with another input of No. two adders 8 and the signal input part of pi controller 2, the signal output part of pi controller 2 connects a signal input part of an adder 6, the outfan of No. two adders 8 connects the signal input part of the repetitive controller 7 with feedforward, the signal output part of the repetitive controller 7 with feedforward connects another signal input part of an adder 6,

Booster circuit 5 also includes filter inductance 5-1, diode 5-2, switching device 5-3 and pulse width modulation module 5-4, one power supply signal outfan of photovoltaic cell 4 connects one end of filter inductance 5-1, the other end of filter inductance 5-1 is simultaneously connected with the negative electrode of diode 5-2 and the power input of switching device 5-3, the power take-off of switching device 5-3 connects another power supply signal outfan of photovoltaic cell 4, the drive end of the modulation signal output part connecting valve device 5-3 of pulse width modulation module 5-4; The signal output part of a number adder 6 connects the modulation signal input part of the pulse width modulation module 5-4 of booster circuit 5;

The cyclic swing suppressing method of photovoltaic power generation system current in direct-current grid, concretely comprising the following steps of the method:

Step one, set photovoltaic cell electric current set-point, by photovoltaic cell current collection circuit gather photovoltaic cell electric current, it is thus achieved that the actual value of photovoltaic cell electric current;

Step 2, the set-point of the photovoltaic cell electric current in step one is deducted the actual value of photovoltaic cell electric current, it is thus achieved that the set-point of photovoltaic cell electric current and the poor x (k) of actual value; Wherein, k is for calculating period index;

Step 3, by the poor x (k) of the set-point of photovoltaic cell electric current obtained in step 2 and actual value, be input to the discretization equation of moving average filter, it is thus achieved that moving average filter is at the output valve y in this calculating cycle_f(k);

The discretization equation of moving average filter is:

$y_f\left(k\right)=y_f(k-1)+\frac{\[x\left(k\right)-{\mathrm{\λ}}_1\left(0\right)\]}{N}$

Wherein λ₁(0) it is array λ₁First element value, described λ₁Being the array for storing x (k), its width is N, N is the positive integer more than 100, y_f(k-1) output valve of the moving average filter in cycle is calculated for kth-1;

Step 4, renewal array λ₁In each element value: make λ₁(i)=λ₁(i+1), wherein, i is array λ₁The label of each element, 0≤i≤N-2, it is judged that whether i is equal to N-2, if the determination result is YES, then make λ (N-1)=x (k), perform step 5; Otherwise, step 4 one is performed;

Step 4 one, make i=i+1, return and perform step 4;

Step 5, the set-point of photovoltaic cell electric current obtained by step 2 and the poor x (k) of actual value deduct the moving average filter of step 3 acquisition at the output valve y in this calculating cycle_f(k), it is thus achieved that the cyclic swing component of x (k)

Step 6, by output valve y in this calculating cycle of the moving average filter that obtains in step 3_fK () is input to the discretization equation of pi controller, it is thus achieved that pi controller is at the output valve y in this calculating cycle_PI(k);

The discretization equation of pi controller is:

y_PI(k)=y_PI(k-1)+K_P[y_f(k)-y_f(k-1)]+K_IT_Sy_f(k)],

Wherein, y_PI(k-1) output valve of the pi controller in cycle, K is calculated for kth-1_PFor proportionality coefficient, K_IFor integral coefficient, T_SIt is calculate periodic quantity;

Step 7, the cyclic swing component of x (k) that will obtain in step 5It is input to the discretization equation of repetitive controller, it is thus achieved that repetitive controller is at the output valve y in this calculating cycle_RC(k); Again by y_RC(k) withIt is added, it is thus achieved that repetitive controller is at the output valve y in this calculating cycle_RC1(k);

The discretization equation of repetitive controller is: $y_{\mathrm{RC}}\left(k\right)={\mathrm{\λ}}_2\left(a\right)+\tilde{x}\left(k\right),$

Wherein, λ₂A () is array λ₂The a element value, λ₂For being used for storing the array of repetitive controller output valve, described array λ₂Width be M; 0≤a≤M, and a is integer, M is the positive integer more than 100;

Step 8, to array λ₂In element be updated, make λ₂(a)=y_RCK (), it is judged that whether a is more than M, if the determination result is YES, then makes a=a-M, performs step 9, otherwise, perform step Aug. 1st;

Step Aug. 1st, make a=a+1, perform step 9;

Step 9, the output valve y that step 6 is obtained_PIK output valve y that () and step 7 obtain_RC1K () is added, it is thus achieved that the dutycycle of device for power switching in booster circuit;

Step 10, dutycycle step 9 obtained are input to booster circuit, the control signal of device for power switching in booster circuit is obtained by the pulse width modulation module in booster circuit, and by the device for power switching in this signal input to booster circuit, complete once to the suppression of the cyclic swing of photovoltaic power generation system current in direct-current grid.

DC micro-electric web frame involved in the present invention is as shown in Figure 1, including photovoltaic generating system and energy-storage system, drive single-phase inversion load, the main function realized is by the coordination of photovoltaic generating system and energy-storage system is controlled, thus ensureing to keep stablizing of DC bus-bar voltage when different photovoltaic generation power.

The DC voltage cyclic swing impact on the output power from photovoltaic cells when photovoltaic generating system adopts single closed loop control of pi controller of photovoltaic cell electric current in analysis conventional method below, Fig. 2 is the photovoltaic generating system electrical structure schematic diagram of adoption rate integral controller, photovoltaic generating system includes photovoltaic cell, booster circuit and photovoltaic cell current collection circuit, the outfan of photovoltaic cell is connected with the input of booster circuit, photovoltaic cell current collection circuit gathers photovoltaic cell electric current, booster circuit includes the filter inductance of input, full-controlled switch device, the diode of outfan, pulse width modulation module and drive circuit.

In present embodiment, the set-point of photovoltaic cell electric current is given by outside. assume that DC bus-bar voltage exists sinusoidal cycles fluctuation, adopt MATLAB simulation software that system has been carried out simulation study in this case, Fig. 3 gives the waveform when DC bus-bar voltage of direct-current grid exists cyclic swing, Fig. 4, Fig. 5 and Fig. 6 sets forth the electric current of photovoltaic cell in the photovoltaic generating system of adoption rate integral controller, the simulation result of voltage and power, by Fig. 3, Fig. 4, Fig. 5 and Fig. 6 can be seen that, when there is cyclic swing in DC bus-bar voltage, photovoltaic cell electric current, all there is the cyclic swing of same frequency in voltage and power, make photovoltaic cell cannot be continuously in maximum power point, thus reducing its work efficiency.

The principle Analysis of links of the present invention, the ultimate principle of moving average filter is, arranges an array λ with one fixed width₁What each element in this array stored respectively is the actual value of each photovoltaic cell current error signal before this calculating cycle, in each calculating cycle, the error signal of the photovoltaic cell electric current of sampling input, and each element of this array is moved one by one from high to low, then the error signal of the photovoltaic cell electric current in this calculating cycle is assigned to the highest element λ of this array₁(N-1), namely ensure that what store in first element of this array is the oldest data volume. Then the meansigma methods of all elements in this array is asked for, thus reaching the purpose of filtering. Obtaining its discretization equation according to its principle is

$y_f\left(k\right)=y_f(k-1)+\frac{\[x\left(k\right)-{\mathrm{\λ}}_1\left(0\right)\]}{N}$

The discretization equation of pi controller is:

y_PI(k)=y_PI(k-1)+K_P[x(k)-x(k-1)]+K_IT_Sx(k)]

For repetitive controller, its ultimate principle is, with the cycle of photovoltaic cell current wave momentum for benchmark, in each calculating cycle, by the input value of the repetitive controller output valve plus repetitive controller corresponding to cycle on photovoltaic cell current wave momentum. From above-mentioned principle, repetitive controller be actually with cycle of input quantity be time constant integrator, by the continuous superposition of the complete cycle to input quantity, play the effect of the accumulation of error, it is zero in input quantity, namely during controlled volume floating, the output of repetitive controller remains unchanged, thus realizing the control to controlled volume. For realizing above-mentioned functions, it is necessary to the output valve of the repetitive controller in a cycle on the photovoltaic cell current wave momentum that this calculating cycle of real-time storage is corresponding, it is therefore desirable to arrange the array λ that width is M₂For storing the output valve of repetitive controller. The discretization equation being derived from repetitive controller is

$y_{\mathrm{RC}}\left(k\right)={\mathrm{\λ}}_2\left(a\right)+\tilde{x}\left(k\right)$

Again by array λ₂The element of middle correspondence is updated, even λ₂(a)=y_RCK (), to be used at next cycle. Wherein a is an integer variable, is used in each calculating cycle array λ₂It is updated, in each cycle, makes a=a+1, if a > M, then make a=a-M. M is greater than the positive integer of 100.

In order to improve the gain of repetitive controller, present invention introduces the feedforward, by the output of repetitive controller plus its input value, namely

$y_{\mathrm{RC}1}\left(k\right)=y_{\mathrm{RC}}\left(k\right)+\tilde{x}\left(k\right)$

Output valve by the output valve of pi controller with the output valve addition whole controller of acquisition of the repetitive controller of feedforward is again

y(k)=y_RC1(k)+y_PI(k)

In above-mentioned formula, y_f(k-1) output valve of the moving average filter in cycle, λ is calculated for kth-1₁(0) it is array λ₁First element value; y_PI(k-1) output valve of the pi controller in cycle, λ is calculated for kth-1₂A () is array λ₂The a element value, K_PFor proportionality coefficient, K_IFor integral coefficient, T_SIt is calculate periodic quantity.

Output valve y (k) is namely as the dutycycle of booster circuit, and the pulse width modulation module that dutyfactor value is input to booster circuit obtains the control signal of device for power switching in booster circuit. The ultimate principle of pulse width modulation module is, the triangular wave of one high frequency is set, and compared with dutycycle, when dutycycle is more than triangular wave, comparative result is high level, is otherwise low level, is derived from a series of high level width and square wave that dutycycle is directly proportional, thus as the control signal of device for power switching in booster circuit, to realize the closed loop control to photovoltaic cell electric current.

Build the emulation platform based on SIMULINK, control method proposed by the invention is carried out simulating, verifying. Fig. 9, Figure 10 and Figure 11 sets forth employing traditional proportional_integral control device and add the battery of the method for the invention, voltage and Simulation of SAR power image result. As seen from the figure, when adopting traditional proportional_integral control device the 0.1s to 0.2s of Figure 10 and Figure 11 (corresponding diagram 9), it is implicitly present in the fluctuation of DC voltage, in turn result in photovoltaic cell output electric current, voltage and power and there is principle fluctuation, make it cannot be in maximum power point, power swing reaches 5%, has had a strong impact on its work efficiency. At 0.2s, proposed method joined the device for power switching in booster circuit, as seen from the figure, 0.2s to 0.3s eliminates the DC voltage fluctuation impact on the output power from photovoltaic cells well, and the fluctuation of output, less than 1%, significantly improves its work efficiency.

Claims (1)

1. the cyclic swing suppressing method of photovoltaic power generation system current in direct-current grid, described photovoltaic generating system include moving average filter (1), pi controller (2), photovoltaic cell current collection circuit (3), photovoltaic cell (4), booster circuit (5), adder (6), with the repetitive controller (7) of feedforward, a subtractor (8) and No. two subtractors (9);

Photovoltaic cell current collection circuit (3) is used for gathering the current signal that photovoltaic cell (4) exports, the collection signal output part of photovoltaic cell current collection circuit (3) connects an input of No. two subtractors (9), the set-point that another input is photovoltaic cell electric current of No. two subtractors (9), the outfan of No. two subtractors (9) is simultaneously connected with the filtering signal input of moving average filter (1) and an input of a subtractor (8), the filtered signal outfan of moving average filter (1) is simultaneously connected with another input of a subtractor (8) and the signal input part of pi controller (2), the signal output part of pi controller (2) connects a signal input part of an adder (6), the outfan of a number subtractor (8) connects the signal input part of the repetitive controller (7) with feedforward, the signal output part of the repetitive controller (7) with feedforward connects another signal input part of an adder (6),

Booster circuit (5) also includes filter inductance (5-1), diode (5-2), switching device (5-3) and pulse width modulation module (5-4), one power supply signal outfan of photovoltaic cell (4) connects one end of filter inductance (5-1), the other end of filter inductance (5-1) is simultaneously connected with the negative electrode of diode (5-2) and the power input of switching device (5-3), the power take-off of switching device (5-3) connects another power supply signal outfan of photovoltaic cell (4), the drive end of modulation signal output part connecting valve device (5-3) of pulse width modulation module (5-4),The signal output part of a number adder (6) connects the modulation signal input part of the pulse width modulation module (5-4) of booster circuit (5);

It is characterized in that: based on the cyclic swing suppressing method of photovoltaic power generation system current in the direct-current grid of above-mentioned photovoltaic generating system, concretely comprising the following steps of the method:

Step one, set photovoltaic cell electric current set-point, by photovoltaic cell current collection circuit gather photovoltaic cell electric current, it is thus achieved that the actual value of photovoltaic cell electric current;

Step 2, the set-point of the photovoltaic cell electric current in step one is deducted the actual value of photovoltaic cell electric current, it is thus achieved that the set-point of photovoltaic cell electric current and the poor x (k) of actual value; Wherein, k is for calculating period index;

Step 3, by the poor x (k) of the set-point of photovoltaic cell electric current obtained in step 2 and actual value, be input to the discretization equation of moving average filter, it is thus achieved that moving average filter is at the output valve y in this calculating cycle_f(k);

The discretization equation of moving average filter is:

$y_f\left(k\right)=y_f(k-1)+\frac{\[x\left(k\right)-{\mathrm{\λ}}_1\left(0\right)\]}{N}$

Wherein λ₁(0) it is array λ₁First element value, described λ₁Being the array for storing x (k), its width is N, N is the positive integer more than 100, y_f(k-1) output valve of the moving average filter in cycle is calculated for kth-1;

Step 4, renewal array λ₁In each element value: make λ₁(i)=λ₁(i+1), wherein, i is array λ₁The label of each element, 0≤i≤N-2, it is judged that whether i is equal to N-2, if the determination result is YES, then make λ (N-1)=x (k), perform step 5; Otherwise, step 4 one is performed;

Step 4 one, make i=i+1, return and perform step 4;

Step 5, the set-point of photovoltaic cell electric current obtained by step 2 and the poor x (k) of actual value deduct the moving average filter of step 3 acquisition at the output valve y in this calculating cycle_f(k), it is thus achieved that the cyclic swing component of x (k)

Step 6, by output valve y in this calculating cycle of the moving average filter that obtains in step 3_fK () is input to the discretization equation of pi controller, it is thus achieved that pi controller is at the output valve y in this calculating cycle_PI(k);

The discretization equation of pi controller is:

y_PI(k)=y_PI(k-1)+K_P[y_f(k)-y_f(k-1)]+K_IT_Sy_f(k)],

Wherein, y_PI(k-1) output valve of the pi controller in cycle, K is calculated for kth-1_PFor proportionality coefficient, K_IFor integral coefficient, T_SIt is calculate periodic quantity;

Step 7, the cyclic swing component of x (k) that will obtain in step 5It is input to the discretization equation of repetitive controller, it is thus achieved that repetitive controller is at the output valve y in this calculating cycle_RC(k); Again by y_RC(k) withIt is added, it is thus achieved that with the repetitive controller of feedforward at the output valve y in this calculating cycle_RC1(k);

The discretization equation of repetitive controller is:

Wherein, λ₂A () is array λ₂The a element value, λ₂For being used for storing the array of repetitive controller output valve, described array λ₂Width be M; 0≤a≤M, and a is integer, M is the positive integer more than 100;

Step 8, to array λ₂In element be updated, make λ₂(a)=y_RCK (), it is judged that whether a is more than M, if the determination result is YES, then makes a=a-M, performs step 9, otherwise, perform step Aug. 1st;

Step Aug. 1st, make a=a+1, perform step 9;

Step 9, the output valve y that step 6 is obtained_PIK output valve y that () and step 7 obtain_RC1K () is added, it is thus achieved that the dutycycle of device for power switching in booster circuit;

Step 10, dutycycle step 9 obtained are input to booster circuit, the control signal of device for power switching in booster circuit is obtained by the pulse width modulation module in booster circuit, and by the device for power switching in this signal input to booster circuit, complete once to the suppression of the cyclic swing of photovoltaic power generation system current in direct-current grid.