Feedforward control method and device for grid-connected inverter, medium and wind turbine generator set

Abstract

The present disclosure provides a feedforward control method and device, medium and wind turbine generator set of a grid-connected inverter. The feedforward control method may include obtaining a first voltage based on the capacitor voltage of a capacitor in a filter connected to the output end of the grid-connected inverter; obtaining a second voltage by filtering the capacitor voltage; multiplying the first voltage by a first weighting coefficient to obtain a first weighted voltage; multiplying the second voltage by a second weighting coefficient to obtain a second weighted voltage; adding the first weighted voltage to the second weighted voltage to obtain a feedforward voltage control component; and controlling the grid-connected inverter based on the feedforward voltage control component. The feedforward control method and feedforward control device of the grid-connected inverter according to the embodiments of the present invention can reduce the current harmonics of the grid connection point and improve the phase angle stability margin.

Description

Technical Field

[0001] The present invention generally relates to the field of grid-connected inverters, and more specifically, to a feedforward control method and device, a medium and a wind turbine generator set of a grid-connected inverter. Background Art

[0002] As the capacity of wind turbines connected to the grid gradually increases, the harmonics at the grid connection points of wind turbines are receiving more and more attention from grid companies, and the requirements for the performance of grid-connected inverters are becoming higher and higher.

[0003] The grid-connected inverters connected to the wind farm are relatively scattered and the wiring impedance within the field is complex. This requires the grid-connected inverter to have a certain adaptability to the grid impedance and to be adaptable to a wide range of grid impedance parameters, so as to adapt to the operating requirements of both weak and strong grids.

[0004] Grid-connected power quality is an important indicator of the grid-connected performance of the inverter. Grid voltage feedforward can suppress the influence of grid voltage harmonics on grid-connected current, improve the quality of grid-connected current, and increase the current response speed. Therefore, it is widely used in the control of grid-connected inverters.

[0005] However, grid voltage feedforward will introduce an additional grid-connected current positive feedback loop, which will significantly reduce the stability margin of the system and thus reduce the robust stability of the system to grid impedance.

[0006] Furthermore, the phase angle stability margin during capacitor voltage feedforward is relatively small. Summary of the invention

[0007] An exemplary embodiment of the present invention provides a feedforward control method and a feedforward control device for a grid-connected inverter, which can reduce current harmonics at a grid-connected point and improve a phase angle stability margin.

[0008] According to one aspect of the present invention, a feedforward control method for a grid-connected inverter is provided, the feedforward control method comprising: obtaining a first voltage based on a capacitor voltage of a capacitor in a filter connected to an output end of the grid-connected inverter; obtaining a second voltage by filtering the capacitor voltage; multiplying the first voltage by a first weighting coefficient to obtain a first weighted voltage; multiplying the second voltage by a second weighting coefficient to obtain a second weighted voltage; adding the first weighted voltage to the second weighted voltage to obtain a feedforward voltage control component; and controlling the grid-connected inverter based on the feedforward voltage control component.

[0009] According to a preferred embodiment of the present invention, the step of obtaining the second voltage by filtering the capacitor voltage may include: obtaining the second voltage by performing bandpass filtering within the first frequency band on the capacitor voltage.

[0010] According to a preferred embodiment of the present invention, the step of obtaining a first voltage based on the capacitor voltage of a capacitor in a filter connected to the output end of the grid-connected inverter may include: obtaining the first voltage by performing transformation and / or filtering on the capacitor voltage, wherein the first voltage includes a fundamental voltage component of the capacitor voltage.

[0011] According to a preferred embodiment of the present invention, the step of obtaining the first voltage by performing transformation and / or filtering on the capacitor voltage may include: obtaining the first voltage by performing a fast Fourier transform on the capacitor voltage or performing a bandpass filtering on the capacitor voltage within a second frequency band, wherein the first frequency band is wider than the second frequency band.

[0012] According to a preferred embodiment of the present invention, the feedforward control method may further include: obtaining the phase angle of the capacitor voltage, and the step of obtaining the first voltage by performing transformation and / or filtering on the capacitor voltage includes: performing a rotating coordinate transformation on the capacitor voltage based on the phase angle, performing a low-pass filtering on the capacitor voltage in a rotating coordinate system, and performing an inverse rotating coordinate transformation on the filtered voltage to obtain the first voltage.

[0013] According to a preferred embodiment of the present invention, controlling a grid-connected inverter based on a feed-forward voltage control component may include: obtaining an inductor current flowing through an inductor in a filter; obtaining a first output voltage based on the inductor current and a phase angle; and controlling a pulse modulation unit of the grid-connected inverter based on the sum of the feed-forward voltage control component and the first output voltage.

[0014] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores instructions or programs, and when the instructions or programs are executed by a processor, the above feedforward control method is implemented.

[0015] According to another aspect of the present invention, a feedforward control device for a grid-connected inverter is provided, the feedforward control device comprising: a first voltage obtaining unit, configured to obtain a first voltage based on a capacitor voltage of a capacitor in a filter connected to an output end of the grid-connected inverter; a first filtering unit, configured to obtain a second voltage by filtering the capacitor voltage; a first proportional unit, configured to multiply the first voltage by a first weighting coefficient to obtain a first weighted voltage; a second proportional unit, configured to multiply the second voltage by a second weighting coefficient to obtain a second weighted voltage; a first adder, configured to add the first weighted voltage to the second weighted voltage to obtain a feedforward voltage control component; and a feedforward control unit, for controlling the grid-connected inverter based on the feedforward voltage control component.

[0016] According to a preferred embodiment of the present invention, the first filtering unit may be configured to obtain the second voltage by performing bandpass filtering within the first frequency band on the capacitor voltage.

[0017] According to a preferred embodiment of the present invention, the first voltage obtaining unit may be further configured to obtain the first voltage by performing transformation and / or filtering on the capacitor voltage, wherein the first voltage includes a fundamental voltage of the capacitor voltage.

[0018] According to a preferred embodiment of the present invention, the first voltage obtaining unit may be further configured to obtain the first voltage by performing a fast Fourier transform on the capacitor voltage or performing a bandpass filtering on the capacitor voltage within a second frequency band, wherein the first frequency band is wider than the second frequency band.

[0019] According to a preferred embodiment of the present invention, the feedforward control device may further include a phase-locked loop, which is configured to obtain the phase angle of the capacitor voltage, and the first voltage acquisition unit is further configured to: perform a rotating coordinate transformation on the capacitor voltage based on the phase angle, perform a low-pass filtering on the capacitor voltage in a rotating coordinate system, and perform a rotating coordinate inverse transformation on the filtered voltage to obtain the first voltage.

[0020] According to a preferred embodiment of the present invention, the feedforward control unit may further include a current loop and a grid-connected inverter controller, the current loop being configured to obtain a first output voltage by using a phase angle and an inductor current flowing through an inductor in a filter, and the grid-connected inverter controller comprising: a second adder configured to add a feedforward voltage control component to the first output voltage to output a control voltage; and a pulse modulation unit configured to receive the control voltage and modulate according to the control voltage.

[0021] According to another aspect of the present invention, a wind turbine generator set is provided. The wind turbine generator set includes the above-mentioned feedforward control device.

[0022] The feedforward control device and feedforward control method of the grid-connected inverter according to the embodiment of the present invention make it easier to detect and sample the capacitor voltage, and the system has high robustness stability to the grid impedance.

[0023] Additional aspects and / or advantages of the present general inventive concept will be set forth in part in the following description and in part will be obvious from the description, or may be learned through practice of the present general inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other objects and features of the exemplary embodiments of the present invention will become more apparent through the following description in conjunction with the accompanying drawings which exemplarily illustrate the embodiments, in which:

[0025] Figure 1 is a control block diagram showing a feedforward control device for a grid-connected inverter according to a first embodiment of the present invention;

[0026] Figure 2 is a control block diagram showing a feedforward control device for a grid-connected inverter according to a second embodiment of the present invention;

[0027] Figure 3 is a control block diagram showing a feedforward control device for a grid-connected inverter according to a third embodiment of the present invention;

[0028] Figure 4 FIG. 1 is a diagram showing a detailed configuration of a first voltage obtaining unit included in the feedforward control device for a grid-connected inverter according to the first embodiment of the present invention.

[0029] Figure 5 and Figure 6 is a flow chart illustrating a feedforward control method of a grid-connected inverter according to an exemplary embodiment of the present invention;

[0030] Figure 7 This is the analysis diagram of grid-connected current harmonics when capacitor voltage is fed forward;

[0031] Figure 8 is an analysis diagram of grid-connected current harmonics when capacitor voltage is weighted feed-forward; and

[0032] Fig. 9 It is a comparative diagram of the amplitude-frequency and phase-frequency characteristic curves of the grid-connected inverter output impedance corresponding to capacitor voltage feedforward and capacitor voltage weighted feedforward. DETAILED DESCRIPTION

[0033] Reference will now be made in detail to embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein like reference numerals refer to like parts throughout. The embodiments will be described below with reference to the drawings in order to explain the present invention.

[0034] The feedforward control method and feedforward control device of a grid-connected inverter according to the embodiments of the present invention may be applicable to a grid-connected inverter in the field of wind power, but is not limited thereto.

[0035] According to an embodiment of the present invention, the capacitor voltage weighted feedforward control strategy is used to reduce the current harmonics of the grid connection point and improve the phase stability margin of the system. Furthermore, according to an embodiment of the present invention, the capacitor voltage is filtered (e.g., bandpass filtering) to obtain a weighted component, and the weighted component is superimposed with the fundamental voltage weighted component (e.g., weighted superposition) to obtain a control component.

[0036] Compared with control strategies such as grid voltage feedforward and capacitor voltage direct feedforward, the feedforward control device and feedforward control method of the present invention can obtain a higher phase stability margin and a smaller total harmonic distortion.

[0037] Figure 1 is a control block diagram showing a feedforward control device for a grid-connected inverter according to a first embodiment of the present invention, Figure 2 is a control block diagram showing a feedforward control device for a grid-connected inverter according to a second embodiment of the present invention, Figure 3 is a control block diagram showing a feedforward control device for a grid-connected inverter according to a third embodiment of the present invention, Figure 4 FIG. 1 is a diagram showing a detailed configuration of a first voltage obtaining unit included in the feedforward control device for a grid-connected inverter according to the first embodiment of the present invention.

[0038] like Figures 1 to 3 As shown, the DC voltage input module 100 inputs a DC voltage to the grid-connected inverter 110. The grid-connected inverter 110 may be an inverter implemented by an IGBT, which may convert the DC voltage into an AC voltage and output the converted voltage to the filter 120. The filter 120 may output the filtered voltage to the public power grid 3.

[0039] Filter 120 is an "LCL" type filter, where the capacitor voltage refers to the capacitor voltage of the capacitor C of the LCL type filter. The "LCL type" filter can refer to a filter formed by two inductors (L1 and L2) and a capacitor C, or it can refer to a filter that is equivalent to two inductors and a capacitor.

[0040] According to an embodiment of the present invention, the capacitance voltage u of the capacitor is used c Feed forward instead of based on the grid voltage u pcc For example, for a system where the inductor L2 (the inductor close to the grid connection point in the LCL filter) is a transformer leakage inductance, it is difficult to sample the grid connection point voltage.

[0041] The feedforward control method and feedforward control device of the grid-connected inverter according to the embodiment of the present invention can be used to generate a feedforward voltage control component u f , which can be used to perform feedforward control on the grid-connected inverter 110.

[0042] The feedforward control device of the grid-connected inverter of the present invention may include a first voltage obtaining unit 141 and a first filtering unit 142, and a first adder 145 as a part of the feedforward voltage control component generating unit 140. The feedforward control device of the grid-connected inverter of the present invention may also include a first proportional unit 143 and a second proportional unit 144 as a part of the feedforward voltage control component generating unit 140, and may also include a feedforward control unit (not shown) for controlling the grid-connected inverter based on the feedforward voltage control component.

[0043] The feedforward control device of the grid-connected inverter according to the embodiment of the present invention may further include a phase-locked loop 170. The phase-locked loop 170 may obtain the capacitor voltage u c The phase angle can be a synchronous phase-locked loop, etc.

[0044] The first voltage obtaining unit 141 may be based on the capacitance voltage u of the capacitor C in the filter 120 connected to the output terminal of the grid-connected inverter. c Get the first voltage u cf2 .

[0045] like Figures 1 to 3 As shown, the first voltage obtaining unit 141 can obtain the first voltage u by performing transformation and / or filtering on the capacitor voltage. cf2 , the first voltage u cf2 May include the fundamental voltage of the capacitor voltage.

[0046] In addition, if Figures 1 to 3 As shown, the first filtering unit 142 can c Filter to obtain the second voltage u cf1 Specifically, the first filtering unit 142 can c Perform bandpass filtering within the first frequency band to obtain a second voltage u cf1 .

[0047] like Figure 1 As shown, the first voltage obtaining unit 141 may include two coordinate conversion units and a low-pass filtering unit 146. The first voltage obtaining unit may obtain the first voltage u by performing coordinate conversion and filtering on the capacitor voltage. cf2 For example, the first voltage obtaining unit 141 may obtain the capacitor voltage u based on the phase angle obtained via the phase-locked loop 170. c The rotating coordinate conversion is performed, the capacitor voltage is low-pass filtered by the low-pass filter unit 146 in the rotating coordinate system, and the filtered voltage is inversely transformed to obtain the first voltage u cf2 .

[0048] like Figure 4 As shown, the first voltage obtaining unit 141 can perform both positive sequence conversion and negative sequence conversion. Specifically, the first voltage obtaining unit 141 can obtain the capacitor voltage u c Carry out positive sequence abc coordinates to dq + The coordinates are transformed, and then low-pass filtering is performed by the low-pass filtering unit 146, and then the filtered voltage is dq + Similarly, the first voltage obtaining unit 141 can simultaneously convert the capacitor voltage u c Carry out negative sequence abc coordinate to dq - The coordinates are transformed, and then low-pass filtering is performed by the low-pass filtering unit 146, and the filtered voltage is dq - The conversion of coordinates to abc coordinates, after superposition, the first voltage u is obtained cf2 .

[0049] Optionally, the negative sequence conversion may be omitted, and when the first voltage obtaining unit 141 performs positive sequence conversion and negative sequence conversion simultaneously, the fundamental voltage component may be accurately obtained.

[0050] like Figure 2 As shown, unlike the first embodiment of the present invention, in the second embodiment of the present invention, the first voltage obtaining unit 141 can obtain the capacitor voltage u c Perform a fast Fourier transform (FFT) to obtain the first voltage u cf2 , when the first voltage u is obtained by performing FFT on the capacitor voltage cf2 When the calculation is large, the transformation time is long, and the software algorithm running speed and / or hardware configuration requirements are relatively high.

[0051] like Figure 3 As shown, different from the first and second embodiments according to the present invention, in the third embodiment of the present invention, the first voltage obtaining unit 141 can obtain the capacitor voltage u c Perform bandpass filtering in the second frequency band to obtain the first voltage u cf2 .

[0052] Unlike the first frequency band bandpass-filtered by the first filtering unit 142, the second frequency band is narrower than the first frequency band.

[0053] As described above, the first filtering unit 142 can c Perform bandpass filtering within the first frequency band to obtain a second voltage u cf1 .

[0054] The transfer function of the bandpass filter of the first filtering unit 142 can be

[0055]

[0056] Wherein, ω0 is the center frequency, and optionally, the center frequency may be 1250 Hz, and the center frequency may be the resonant frequency of the filter 120, ω c is the bandwidth, for example, the bandwidth may be 800 Hz.

[0057] The feedforward control device of the grid-connected inverter according to the embodiment of the present invention can perform band-pass filtering on the capacitor voltage through the first filtering unit 142, so as to extract a specific component of the capacitor voltage (for example, 850Hz∽1650Hz), and then superimpose it with the fundamental voltage component obtained by the first voltage obtaining unit (for example, weighted superposition). Therefore, the feedforward control method according to the embodiment of the present invention can not only suppress low-frequency harmonics, but also has a resonant frequency band damping effect.

[0058] In addition, compared with the technical solution of obtaining the feedforward control component only through coordinate transformation, the feedforward control device of the grid-connected inverter according to the embodiment of the present invention and the feedforward control method to be described below can retain the frequency components within the resonant frequency range of the capacitor voltage, the phase margin can be improved more, the control accuracy is higher, the current harmonics of the power grid are smaller, and the harmonic suppression characteristics are better.

[0059] like Figures 1 to 3 As shown, the first proportional unit 143 can convert the first voltage u cf2 With the first weighting coefficient k f2 Multiply to obtain a first weighted voltage.

[0060] The second proportional unit 144 can convert the second voltage u cf1 and the second weighting coefficient k f1 Multiply to obtain a second weighted voltage.

[0061] Optionally, the first proportional unit 143 and the second proportional unit 144 can be implemented by a multiplier, etc. The first adder 145 can add the first weighted voltage to the second weighted voltage to obtain the feedforward voltage control component u f .

[0062] The first weighting coefficient k f2 and the second weighting coefficient k f1 can be within the range of greater than 0 and less than or equal to 1. Optionally, the first weighting coefficient k can be adjusted according to the type of power grid (for example, a strong power grid or a weak power grid). f2 and the second weighting coefficient k f1 Here, it is not necessary to require the first weighting coefficient k f2 and the second weighting coefficient k f1 The sum of is 1, therefore, the feedforward control device and feedforward control method of the grid-connected inverter according to the embodiment of the present invention can have a higher degree of adjustment freedom.

[0063] like Figures 1 to 3 As shown, the feedforward control unit of the grid-connected inverter according to the embodiment of the present invention may further include a current loop 150 and a grid-connected inverter controller 160 .

[0064] The current loop 150 can obtain a first output voltage u by using the phase angle θ and the inductor current i1 of the inductor L1. i Specifically, the input of the current loop 150 can be a preset current i ref , the current loop 150 can be i ref The AC current i1* is multiplied by the sine of θ, and then the AC current i1* is subtracted from the inductor current i1. The current difference is input to the proportional resonant controller (whose transfer function can be G i(s)), and then the first output voltage u is obtained through the proportional resonant controller output i .

[0065] The grid-connected inverter controller 160 may include a second adder 161 and a pulse modulation unit 162. The second adder 161 may add the feed-forward voltage control component u f With the first output voltage u i Add together to output control voltage u * inv , the pulse modulation unit 162 can receive the control voltage u * inv And output the control signal to the grid-connected inverter 110. The pulse modulation unit 162 can receive the control voltage and modulate the control voltage. The pulse modulation unit 162 can be a space vector pulse width modulation (SVPWM) unit, etc., but the present invention is not limited thereto.

[0066] It should be understood that each unit or module in the feedforward control device according to the exemplary embodiment of the present invention can be implemented as a hardware component and / or a software component. Those skilled in the art can implement each unit according to the processing performed by each defined unit, for example, using a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a software algorithm, etc.

[0067] Figure 5 and Figure 6 is a flow chart illustrating a feedforward control method of a grid-connected inverter according to an exemplary embodiment of the present invention.

[0068] Reference Figure 5 , the feedforward control method of the grid-connected inverter according to the embodiment of the present invention may include steps S110, S120, S130, S140, S150 and S160.

[0069] In step S110, a first voltage is obtained based on a capacitance voltage of a capacitor in a filter connected to an output terminal of the grid-connected inverter. As described above, the filter is an LCL type filter.

[0070] Here, the first voltage may include a fundamental voltage component of the capacitor voltage. In other words, the weighted feedforward control method according to the embodiment of the present invention uses the fundamental voltage component as a weighting term.

[0071] As an example, the step S110 of obtaining the first voltage based on the capacitor voltage of the capacitor in the filter connected to the output terminal of the grid-connected inverter may include: obtaining the first voltage by performing transformation and / or filtering on the capacitor voltage.

[0072] As described above, the transformation here may include at least one of coordinate transformation and fast Fourier transformation, and the filtering may include at least one of low-pass filtering and band-pass filtering. When the transformation is a coordinate transformation, the coordinate transformation may be a conversion from abc coordinates to dq coordinates, or from dq coordinates to abc coordinates.

[0073] As an example, the step of obtaining the first voltage by transforming and / or filtering the capacitor voltage may include: obtaining the first voltage by performing a fast Fourier transform on the capacitor voltage or performing a bandpass filter on the capacitor voltage within a second frequency band. Fast Fourier transform is a known technology and will not be described in detail here.

[0074] In step S120, the second voltage is obtained by filtering the capacitor voltage. The step S120 of obtaining the second voltage by filtering the capacitor voltage may include: obtaining the second voltage by performing a bandpass filter within a first frequency band on the capacitor voltage. The first frequency band here may be a wider frequency band than the second frequency band.

[0075] The feedforward control method of the grid-connected inverter according to the embodiment of the present invention can perform a bandpass filter on the capacitor voltage, thereby extracting a specific component of the capacitor voltage, and then superimposing it with the fundamental voltage component (for example, weighted superposition). Therefore, the feedforward control method of the grid-connected inverter according to the embodiment of the present invention can both suppress low-frequency harmonics and have a resonant frequency band damping effect.

[0076] In step S130, the first voltage is multiplied by the first weighting coefficient to obtain a first weighted voltage. As described above, the first weighting coefficient may be in a range of greater than 0 and less than or equal to 1.

[0077] In step S140, the second voltage is multiplied by the first weighting coefficient to obtain a second weighted voltage. Similar to the first weighted voltage, the second weighting coefficient may also be in a range greater than 0 and less than or equal to 1.

[0078] In step S150, the first weighted voltage is added to the second weighted voltage to obtain a feedforward voltage control component.

[0079] It should be noted that the above steps S110 to S150 may not have a specific order. For example, steps S110 and S120 have no sequence, and steps S130 and S140 have no sequence. In other words, the second voltage may be obtained first and then the first voltage, or the first voltage and the second voltage may be obtained at the same time. The first weighted voltage may be obtained first and then the second weighted voltage, or the first weighted voltage and the second weighted voltage may be obtained at the same time.

[0080] In step S160, the grid-connected inverter may be controlled based on the feed-forward voltage control component.

[0081] Reference Figure 6 , controlling the grid-connected inverter based on the feedforward voltage control component may also include steps S1601, S1602 and S1603.

[0082] In step S1601, the inductor current of the inductor is obtained. For example, the inductor current, capacitor voltage, etc. can be obtained by auxiliary devices such as a sampling unit (eg, a sensor).

[0083] Step S1601 may be performed simultaneously with step S110 and step S120, or may be performed before or after step S110 and step S120.

[0084] In step S1602, a first output voltage is obtained according to the inductor current and the phase angle. For example, the first output voltage can be obtained through a current loop, and the detailed configuration or implementation of the current loop can be as described above, which will not be repeated here.

[0085] In step S1603, the pulse modulation unit of the grid-connected inverter is controlled based on the sum of the feedforward voltage control component and the first output voltage. As described above, the pulse modulation unit as an SVPWM unit can receive the control voltage and output a control signal to the grid-connected inverter.

[0086] Figure 7 This is the analysis diagram of capacitor voltage and grid current harmonics. Figure 8 This is the analysis diagram of capacitor voltage weighted feedforward grid-connected current harmonics. Fig. 9 It is a comparative diagram of the amplitude-frequency and phase-frequency characteristic curves of the grid-connected inverter output impedance corresponding to capacitor voltage feedforward and capacitor voltage weighted feedforward.

[0087] like Figure 7 and Figure 8 As shown, when the capacitor voltage is directly feed-forward controlled, the total harmonic distortion is about 3.71%; when the capacitor voltage is weighted feed-forward controlled, the total harmonic distortion is about 1.67%.

[0088] Compared with the case where the capacitor voltage is directly feed-forward controlled, the total harmonic distortion is relatively lower when the capacitor voltage is weighted feed-forward controlled.

[0089] like Fig. 9 As shown in the figure, compared with the direct capacitor voltage feedforward, the capacitor voltage weighted feedforward control scheme has a larger phase stability margin and a better effect of suppressing current harmonics.

[0090] In addition, compared with the scheme of feeding forward the grid-connected voltage, the phase stability margin of the capacitor voltage weighted feedforward is larger, and compared with sampling the grid-connected voltage, sampling the capacitor voltage is relatively easier.

[0091] The feedforward control device and feedforward control method of the grid-connected inverter according to the embodiment of the present invention can suppress the current harmonics of the grid-connected point and improve the robust stability of the system to the grid impedance.

[0092] Compared with the technical solution of obtaining the feedforward control component only through coordinate transformation, the feedforward control method and feedforward control method of the grid-connected inverter according to the embodiments of the present invention can retain the frequency components within the resonant frequency range of the capacitor voltage, the phase stability margin of the system can be improved more, the control accuracy is higher, the current harmonics of the power grid are smaller, and the harmonic suppression characteristics are better.

[0093] Each operation of the above steps can be written as a software program or instruction. Therefore, the feedforward control method according to the exemplary embodiment of the present invention can be implemented via software. The computer-readable storage medium of the exemplary embodiment of the present invention can store a computer program. When the computer program is executed by the processor, the feedforward control method of the grid-connected inverter as described in the above exemplary embodiment is implemented.

[0094] According to various embodiments of the present disclosure, a device (e.g., a module or their functions) or a method may be implemented by a program or instruction stored in a computer-readable storage medium. When the instruction is executed by a processor, the processor may perform a function corresponding to the instruction or perform a method corresponding to the instruction. At least a portion of a module may be implemented (e.g., executed) by a processor. At least a portion of a programming module may include a module, a program, a routine, an instruction set, and a process for performing at least one function. In one example, an instruction or software includes a machine code (such as a machine code generated by a compiler) directly executed by one or more processors or computers. In another example, an instruction or software includes a higher level code executed by one or more processors or computers using an interpreter. Instructions or software may be written in any programming language based on the block diagrams and flow charts shown in the accompanying drawings and the corresponding descriptions in the specification.

[0095] Computer-readable storage media include magnetic media such as floppy disks and magnetic tapes, optical media (including compact disks (CD) ROMs and DVD ROMs), magneto-optical media such as floppy disks, hardware devices such as ROMs, RAMs, and flash memories designed to store and execute program commands. The program commands include language codes executable by a computer using an interpreter and machine language codes generated by a compiler. The above-mentioned hardware devices can be implemented by one or more software modules for executing the operations of the various embodiments of the present disclosure.

[0096] The module or programming module of the present disclosure may include at least one of the aforementioned components when some components are omitted or other components are added. The operation of the module, programming module or other components may be performed sequentially, in parallel, in a loop or in a tentative manner. In addition, some operations may be performed in different orders, may be omitted or extended with other operations.

[0097] The computer-readable storage medium and / or the feedforward control device of the exemplary embodiments of the present invention may be a part of a wind turbine generator set, or a part of a controller or a control system, or a part of a wind power converter.

[0098] For example, according to an exemplary embodiment of the present invention, a controller of a grid-connected inverter may be provided, and the controller may include: a processor (not shown) and a memory (not shown), wherein the memory stores a computer program, and when the computer program is executed by the processor, the feedforward control method of the grid-connected inverter as described in the above exemplary embodiment is implemented.

[0099] Although certain exemplary embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that modifications may be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents; for example, the technical features of different embodiments may be combined.

Claims

1. A feedforward control method for a grid-connected inverter, characterized in that: include: obtaining a first voltage based on a capacitance voltage of a capacitor in a filter connected to an output terminal of the grid-connected inverter; Obtaining a second voltage by filtering the capacitor voltage; multiplying the first voltage by a first weighting coefficient to obtain a first weighted voltage; multiplying the second voltage by a second weighting coefficient to obtain a second weighted voltage; adding the first weighted voltage and the second weighted voltage to obtain a feedforward voltage control component; controlling the grid-connected inverter based on the feedforward voltage control component, The first voltage includes a fundamental voltage component of the capacitor voltage, and the second voltage includes a weighted component of the capacitor voltage.

2. The feedforward control method of the grid-connected inverter according to claim 1, characterized in that: The step of obtaining the second voltage by filtering the capacitor voltage includes obtaining the second voltage by performing bandpass filtering within a first frequency band on the capacitor voltage.

3. The feedforward control method of the grid-connected inverter according to claim 2, characterized in that: The step of obtaining a first voltage based on the capacitance voltage of a capacitor in a filter connected to the output terminal of the grid-connected inverter comprises: The first voltage is obtained by performing transformation and / or filtering on the capacitor voltage.

4. The feedforward control method of the grid-connected inverter according to claim 3, characterized in that: The step of obtaining the first voltage by performing transformation and / or filtering on the capacitor voltage comprises: The first voltage is obtained by performing a fast Fourier transform on the capacitor voltage or performing a bandpass filter on the capacitor voltage within a second frequency band, wherein the first frequency band is wider than the second frequency band.

5. The feedforward control method of the grid-connected inverter according to claim 3, characterized in that: Also includes: Obtain the phase angle of the capacitor voltage, The step of obtaining the first voltage by performing transformation and / or filtering on the capacitor voltage comprises: The capacitor voltage is subjected to a rotation coordinate transformation based on the phase angle, the capacitor voltage is subjected to a low-pass filter in a rotation coordinate system, and the filtered voltage is subjected to a rotation coordinate inverse transformation to obtain a first voltage.

6. The feedforward control method of the grid-connected inverter according to claim 5, characterized in that: Controlling the grid-connected inverter based on the feedforward voltage control component includes: obtaining an inductor current flowing through an inductor in the filter; Obtaining a first output voltage according to the inductor current and the phase angle; and A pulse modulation unit of the grid-connected inverter is controlled based on a sum of the feed-forward voltage control component and the first output voltage.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores instructions or programs, and when the instructions or programs are executed by a processor, the feedforward control method according to any one of claims 1 to 6 is implemented.

8. A feedforward control device for a grid-connected inverter, characterized in that: include: A first voltage obtaining unit (141) is configured to obtain a first voltage based on a capacitance voltage of a capacitor in a filter connected to an output terminal of the grid-connected inverter; A first filtering unit (142) is configured to obtain a second voltage by filtering the capacitor voltage; A first proportional unit (143) configured to multiply the first voltage by a first weighting coefficient to obtain a first weighted voltage; A second proportional unit (144) configured to multiply the second voltage by a second weighting coefficient to obtain a second weighted voltage; A first adder (145) configured to add the first weighted voltage and the second weighted voltage to obtain a feedforward voltage control component; a feedforward control unit, configured to control the grid-connected inverter based on the feedforward voltage control component, The first voltage includes a fundamental voltage component of the capacitor voltage, and the second voltage includes a weighted component of the capacitor voltage.

9. The feedforward control device for the grid-connected inverter according to claim 8, characterized in that: The first filtering unit (142) is configured to obtain a second voltage by performing a bandpass filtering within a first frequency band on the capacitor voltage.

10. The feedforward control device for the grid-connected inverter according to claim 9, characterized in that: The first voltage obtaining unit (141) is further configured to obtain the first voltage by performing transformation and / or filtering on the capacitor voltage.

11. The feedforward control device for a grid-connected inverter according to claim 10, characterized in that: The first voltage obtaining unit (141) is further configured to obtain the first voltage by performing a fast Fourier transform on the capacitor voltage or performing a bandpass filter on the capacitor voltage within a second frequency band, wherein the first frequency band is wider than the second frequency band.

12. The feedforward control device for the grid-connected inverter according to claim 10, characterized in that: The feedforward control device further comprises a phase-locked loop (170), the phase-locked loop being configured to obtain a phase angle of the capacitor voltage, and the first voltage obtaining unit (141) being further configured to: perform a rotation coordinate conversion on the capacitor voltage based on the phase angle, perform a low-pass filter on the capacitor voltage in a rotation coordinate system, and perform a rotation coordinate inverse conversion on the filtered voltage to obtain a first voltage.

13. The feedforward control device for the grid-connected inverter according to claim 12, characterized in that: The feedforward control unit further comprises a current loop (150) and a grid-connected inverter controller (160), wherein the current loop (150) is configured to obtain a first output voltage by using the phase angle and an inductor current flowing through the inductor in the filter, and the grid-connected inverter controller (160) comprises: A second adder (161) is configured to add the feedforward voltage control component to the first output voltage to output a control voltage; and The pulse modulation unit (162) is configured to receive the control voltage and perform modulation according to the control voltage.

14. A wind turbine generator set, comprising the feedforward control device according to any one of claims 8 to 13.

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