Control method and system of grid-type active power filter

Abstract

The present invention provides a control method and system for a grid-forming active power filter, belonging to the field of power electronics technology. The control method of the present invention comprises: generating a harmonic voltage instruction by detecting the voltage at the common connection point, controlling the AC output voltage via a voltage controller, and causing the converter to generate a corresponding compensating harmonic voltage, resulting in the converter presenting an approximate short-circuit characteristic to harmonics; the present invention avoids the injection of harmonic currents generated by nonlinear loads into the grid, and has a grid-forming function while compensating for harmonic currents.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a control method of a grid-type active power filter and a control system of a grid-type active power filter. Background Art

[0002] The statements in this section merely provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Thanks to the development of power electronics technology, the controllability of various electrical equipment in production and life has been greatly improved, but it has also led to power quality problems such as reactive power and harmonic pollution. At present, the equipment for harmonic control is mainly divided into passive power filters and active power filters. Among them, passive filters are large in size, only effective for specific harmonics, and there is a risk of harmonic amplification and resonance; active power filters are small in size, flexible in operation, and can suppress system oscillations.

[0004] As the penetration rate of new energy and power electronic devices increases, the inertia and damping of the power system decrease, the system strength weakens, and the stability problem becomes more serious. Grid-Forming (GFM) control technology can improve the voltage and frequency support capabilities of the converter and enhance the stability of the power system. However, the inventors found that the existing grid-forming active power filter does not have a grid-forming performance, or even if it has a certain grid-forming performance, it cannot effectively prevent the harmonic current generated by nonlinear loads from being injected into the power grid. Summary of the invention

[0005] In order to address the deficiencies in the prior art, the present invention provides a control method and system for a grid-type active power filter, which has the voltage source characteristics of a grid-type device and can play the role of rapid frequency and voltage regulation, increased inertia and damping, short-circuit capacity support, and suppression of broadband oscillations; at the same time, the present invention avoids complex calculations and parameter settings, realizes compensation for harmonic currents through a simple and effective implementation method, and is easy to expand and apply.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a control method for a grid-type active power filter.

[0008] A control method for a grid-type active power filter includes the following steps:

[0009] generating a harmonic voltage command according to the voltage at the common connection point of the grid-type active power filter;

[0010] According to the filter capacitor voltage and the phase command of the filter capacitor voltage as the input of the first dq transformation, the sum of the d-axis harmonic voltage command, the fundamental voltage command and the d-axis component of the first dq transformation is used as the first input of the voltage control unit, and the sum of the q-axis harmonic voltage command and the q-axis component of the first dq transformation is used as the second input of the voltage control unit;

[0011] The voltage control unit generates a control instruction according to the first input and the second input to control the output voltage of the grid-type active power filter. When the difference in amplitude and phase between the output voltage of the grid-type active power filter and the voltage at the common connection point is less than the corresponding threshold value, the grid-type active power filter is connected to the grid and operated.

[0012] As a further limitation of the first aspect of the present invention, the phase command of the converter output current and the filter capacitor voltage is used as the input of the second dq transformation, and the current control command output by the voltage control unit and the output of the second dq transformation are used as the input of the current control unit;

[0013] The output of the current control unit and the phase command of the filter capacitor voltage are used as inputs of the third dq transformation, and the output of the third dq transformation is used as input of the PWM modulator to realize control of the converter.

[0014] As a further limitation of the first aspect of the present invention, according to the output current of the grid-type active power filter and the voltage at the common connection point, the output active power and the output reactive power of the grid-type active power filter are generated, according to the input current of the nonlinear load and the voltage at the common connection point, the output reactive power instruction of the grid-type active power filter is obtained, and the output active power, the output reactive power and the output reactive power instruction are used as inputs of the power control unit;

[0015] The reactive power control part of the power control unit generates a fundamental voltage command, and the active power control part of the power control unit generates a power angle, which is added to the voltage phase at the common connection point to generate a phase command of the filter capacitor voltage;

[0016] When the difference in amplitude and phase between the output voltage of the grid-forming active power filter and the voltage at the common connection point is less than the corresponding threshold value, a relay drive instruction is generated to close the switch between the grid-forming active power filter and the nonlinear load, so that the grid-forming active power filter can be connected to the grid and operated.

[0017] As a further limitation of the first aspect of the present invention, based on the voltage at the common connection point, a harmonic voltage component at the common connection point is generated through harmonic extraction, and a phase instruction of the harmonic voltage component at the common connection point and the filter capacitor voltage is used as an input of the fourth dq transformation, and a d-axis harmonic voltage instruction and a q-axis harmonic voltage instruction are obtained after the harmonic instruction calculation.

[0018] In a second aspect, the present invention provides a control system for a grid-type active power filter.

[0019] A control system for a grid-type active power filter, comprising:

[0020] The harmonic instruction generation module is configured to: generate a harmonic voltage instruction according to the voltage at the common connection point of the grid-type active power filter;

[0021] The voltage control module is configured as follows: using the filter capacitor voltage and the phase command of the filter capacitor voltage as the input of the first dq transformation, using the sum of the d-axis harmonic voltage command, the fundamental voltage command and the d-axis component of the first dq transformation as the first input of the voltage control unit, using the sum of the q-axis harmonic voltage command and the q-axis component of the first dq transformation as the second input of the voltage control unit, the voltage control unit generates a control command according to the first input and the second input to control the output voltage of the grid-forming active power filter, when the difference in amplitude and phase between the output voltage of the grid-forming active power filter and the voltage at the common connection point is less than the corresponding threshold value, the grid-forming active power filter is connected to the grid and operated.

[0022] As a further limitation of the second aspect of the present invention, in the voltage control module, the phase command of the converter output current and the filter capacitor voltage is used as the input of the second dq transformation, and the current control command output by the voltage control unit and the output of the second dq transformation are used as the input of the current control unit;

[0023] The output of the current control unit and the phase command of the filter capacitor voltage are used as inputs of the third dq conversion, and the output of the third dq conversion is used as input of the PWM modulator to realize control of the converter.

[0024] As a further limitation of the second aspect of the present invention, it further includes a power control module, wherein the power control module is configured to:

[0025] The output active power and output reactive power of the mesh active power filter are generated according to the output current of the mesh active power filter and the voltage at the common connection point, and the output reactive power instruction of the mesh active power filter is obtained according to the input current of the nonlinear load and the voltage at the common connection point. The output active power, the output reactive power and the output reactive power instruction are used as inputs of the power control unit. The reactive power control part of the power control unit generates a fundamental voltage instruction, and the active power control part of the power control unit generates a power angle. The power angle is added to the voltage phase at the common connection point to generate a phase instruction of the filter capacitor voltage.

[0026] As a further limitation of the second aspect of the present invention, in the harmonic instruction generation module, a harmonic voltage component at the common connection point is generated through harmonic extraction based on the voltage at the common connection point, and a phase instruction of the harmonic voltage component at the common connection point and the filter capacitor voltage is used as an input of the fourth dq transformation, and a d-axis harmonic voltage instruction and a q-axis harmonic voltage instruction are obtained after the harmonic instruction calculation.

[0027] In a third aspect, the present invention provides a computer device, comprising: a processor and a computer-readable storage medium;

[0028] a processor adapted to execute a computer program;

[0029] A computer-readable storage medium having a computer program stored therein, wherein when the computer program is executed by the processor, the control method of the grid-type active power filter as described in the first aspect of the present invention is implemented.

[0030] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program is suitable for being loaded by a processor and executing the control method of the grid-type active power filter as described in the first aspect of the present invention.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention innovatively proposes a control method for a grid-type active power filter, which has the voltage source characteristics of a grid-type device and can play the role of rapid frequency and voltage regulation, increased inertia and damping, short-circuit capacity support, and suppression of broadband oscillation; at the same time, the present invention avoids complex calculations and parameter settings, and realizes compensation of harmonic currents through a simple and effective implementation method, which is easy to expand and apply.

[0033] 2. The present invention innovatively proposes a control method for a grid-type active power filter. According to the voltage at the common connection point, a harmonic voltage component at the common connection point is generated through harmonic extraction. The phase command of the harmonic voltage component at the common connection point and the filter capacitor voltage is used as the input of the fourth dq transformation. After the harmonic command is calculated, the d-axis harmonic voltage command and the q-axis harmonic voltage command are obtained, thereby realizing high-precision generation of harmonic voltage and further improving the control accuracy.

[0034] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0036] Figure 1 A schematic diagram of a circuit and control of a grid-type active power filter according to Embodiment 1 of the present invention;

[0037] Figure 2 This is a schematic diagram of the structure of a voltage controller of a grid-type active power filter according to Embodiment 1 of the present invention;

[0038] Figure 3 This is a schematic diagram of the harmonic compensation principle proposed in Example 1 of the present invention.

[0039] Figure 4 A schematic diagram of the relationship between the amplitude of the harmonic voltage at the PCC and the amplitude of the harmonic voltage command during the harmonic compensation process proposed in Embodiment 1 of the present invention;

[0040] Figure 5 After using the method of embodiment 1 of the present invention, the grid outputs active power p s , reactive power q s The simulation waveform diagram of

[0041] Figure 6 After using the method of embodiment 1 of the present invention, when performing harmonic compensation, the load current output i labc , active power filter output current i ggabc and grid current i sabc The simulation waveform diagram of

[0042] Figure 7 The grid current i is the grid current i proposed in Embodiment 1 of the present invention. sabc Schematic diagram of FFT analysis of the simulation waveform after harmonic compensation reaches steady state. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0044] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0045] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0046] Embodiment 1:

[0047] In this implementation, a control method for a grid-forming active power filter (GFM-APF) is proposed. By detecting the voltage at the point of common coupling (PCC), a harmonic voltage command is generated, and the AC output voltage is controlled via a voltage controller, so that the converter generates a corresponding compensating harmonic voltage, resulting in the converter presenting an approximate short-circuit characteristic to harmonics, thereby avoiding the harmonic current generated by nonlinear loads from being injected into the power grid, and having a grid-forming function while compensating for the harmonic current.

[0048] The grid-type active power filter (subsequent) control method proposed in this implementation is implemented through a voltage control module, a power control module and a harmonic command generation module; the sum of the harmonic voltage command and the fundamental voltage command in the voltage control module of the active power filter is used as the command of the voltage loop, the harmonic voltage command comes from the harmonic command generation module, and the fundamental voltage command is generated by the power control module.

[0049] In this implementation, the voltage controller in the voltage control module of the active power filter is a combination of a repetitive controller and a PI controller, but in other implementations, it may also be other controllers that can track harmonic components.

[0050] In this implementation, the power control module of the active power filter is based on a virtual synchronous motor (VSM) control strategy, but in other implementations, it may also be other power control strategies such as droop control.

[0051] In this implementation, the harmonic instruction generation module of the active power filter is mainly composed of a harmonic extraction part and a harmonic instruction calculation part; wherein the harmonic extraction part is responsible for extracting the harmonic voltage at the PCC, and the harmonic instruction calculation part is responsible for calculating the harmonic voltage instruction.

[0052] In this implementation, when the "short-circuit coefficient" K of the active power filter is 1 and the harmonic compensation reaches a steady state, the harmonic voltage at the PCC will approach 0V; the "short-circuit coefficient" K can be adjusted as needed, and a larger short-circuit coefficient can further reduce the THD at the PCC, but it will affect the stability of the system.

[0053] More specifically, an example is provided below:

[0054] like Figure 1 As shown in the figure, the grid-type active power filter is connected to the grid through an LCL filter (composed of three inverter-side inductors L gi , 3 grid-side inductors L gg , 3 filter capacitors C gf Composition), relay S grThe nonlinear load is connected to the grid at the PCC, and the grid-type active power filter increases damping through the current control module to improve stability; the capacitor voltage v is controlled by the voltage control module. gfabc The control includes fundamental voltage and harmonic voltage; the output active power of active filter is realized through external power control module g and output reactive power q g The harmonic voltage command v is generated by the harmonic command generation module. gfd_ref_har and v gfq_ref_har .

[0055] exist Figure 1 In the main circuit, the DC side voltage is v gdc , the converter output current is i giabc , filter capacitor C gf The voltage is v gfabc , the active filter output current is i ggabc , the voltage at PCC is v gabc , the nonlinear load input current is i labc , the grid voltage is v sabc In this implementation, the current control module controls the converter output current i giabc , the current command is i gid_ref and i giq_ref , the voltage control module controls the filter capacitor voltage v gfabc , the fundamental voltage command is v gfd_ref_base and 0, the harmonic voltage command is v gfd_ref_har and v gfq_ref_har .

[0056] According to the filter capacitor voltage v gfabc And the phase command θ of the filter capacitor voltage g_ref As the input of the first dq transformation, the d-axis harmonic voltage command v gfd_ref_har , fundamental voltage command v gfd_ref_base and the first dq transformed d-axis component v gfd The sum of is used as the first input of the voltage control unit, with the q-axis harmonic voltage command v gfq_ref_har With the first dq transformation q-axis component v gfq The sum of is used as the second input of the voltage control unit;

[0057] The voltage control unit generates a control instruction according to the first input and the second input to control the output voltage of the grid-type active power filter. When the difference in amplitude and phase between the output voltage of the grid-type active power filter and the voltage at the common connection point is less than the corresponding threshold value, the grid-type active power filter is connected to the grid and operated.

[0058] The output current i of the converter is giabcand the phase command θ of the filter capacitor voltage g_ref As the input of the second dq conversion, the current control command (i gid_ref and i giq_ref ) and the output i of the second dq conversion gi_dq As the input of the current control unit;

[0059] The phase command θ between the output of the current control unit and the voltage of the filter capacitor g_ref As the input of the third dq transformation, the output of the third dq transformation is used as the input of the PWM modulator to realize the control of the converter.

[0060] The power control module controls the active filter to output active power g And output reactive power q g (The active filter output current i ggabc and the voltage at PCC v gabc The input current i of the nonlinear load is sampled. labc and the voltage at PCC v gabc , the reactive power absorbed by the nonlinear load is calculated by power, which is the output reactive power instruction q of the active filter. g_ref , the output active power command is 0; the reactive power control part of the power controller generates a fundamental voltage command v gfd_ref_base , the active control part generates a power angle θ g ; Power angle θ g With v gabc The phase of the capacitor voltage v is generated by adding gfabc The phase command θ g_ref (This phase command is also used as the reference phase for coordinate transformation). When the output voltage of the active filter and the voltage at the PCC are consistent in amplitude and phase, the synchronous controller generates a relay drive command to make S gr Close to realize grid-connected operation of active filter.

[0061] The harmonic command generation module generates harmonic voltage command v gfd_ref_har and v gfq_ref_har , sample the voltage v at PCC gabc , the harmonic voltage component v at PCC is generated by harmonic extraction ghabc , for details on the calculation of harmonic voltage instructions, see Figure 3 and Figure 4 Specifically, according to the voltage v at the common connection point gabc , the harmonic voltage component v at the common connection point is generated by harmonic extraction ghabc , with the harmonic voltage component v at the common connection point gabc The phase command θ of the filter capacitor voltage g_refAs the input of the fourth dq transformation, the d-axis harmonic voltage command v is obtained after the harmonic command calculation. gfd_ref_har and q-axis harmonic voltage command v gfq_ref_ha .

[0062] Figure 2 The voltage controller of the grid-type active power filter proposed in the present disclosure is demonstrated, in which an "embedded repetitive controller" is adopted, which is composed of a repetitive controller and a PI controller and has the control performance of tracking signals (harmonics) containing multiple frequency components.

[0063] like Figure 3 As shown, a harmonic compensation principle diagram of a simplified model of an equivalent voltage source based on the grid-type active power filter connecting the grid and the local nonlinear load is shown. Generally, the grid is simplified to a series circuit of an AC voltage source and an inductor. Due to the fast speed and high precision of AC voltage control, the grid-type converter can be regarded as a controllable AC voltage source. In addition, the transmission line is generally purely inductive, and the inductor L gg and L s Based on the above assumptions, the simplified model is as follows Figure 3 As shown. For the convenience of analysis, this figure only analyzes the harmonics in the line and omits the analysis of the fundamental wave. As shown in the figure, after the grid-type active power filter is connected to the grid and reaches stability, the harmonic voltage value at the PCC is V gh ∠0°; add harmonic voltage command K×V gh ∠180°, equivalent to line impedance L gg The impedance of the line is converted to L gg / (1+K).

[0064] It is worth noting that the system will be in a transient state immediately after the harmonic voltage command is added; after dynamic adjustment, the system reaches a steady state, and the steady-state value of the harmonic voltage at the PCC is In summary, the harmonic compensation of the grid-type active power filter proposed in the present invention is to reduce the line impedance L gg , thereby providing a low-impedance path for the harmonic current of the power grid (the fundamental part is not affected), achieving a method of harmonic current compensation.

[0065] like Figure 4 As shown, it shows the harmonic voltage amplitude v at the PCC when the harmonic compensation method of the present disclosure is used. gd_har (v gq_har ) and harmonic voltage command amplitude v gfd_ref_har (v gfd_ref_har ) changes with time, at the initial moment v gd_har (v gq_har ) has a value of V, v gfd_ref_har (v gfd_ref_har) is -K×V; the harmonic voltage command is added at time T0, and the harmonic compensation process reaches a steady state at time T1, v gd_har (v gq_har ) has a steady-state value of ΔV, v gfd_ref_har (v gfd_ref_har )’s steady-state value is -K×ΔV.

[0066] like Figure 5 As shown, the simulation waveform of the power grid output power when the method disclosed in the present invention is used for harmonic compensation is shown. The simulation parameters are shown in Table 1. Before the power control starts, the load is started. After the power compensation starts, the power grid outputs reactive power q s Tends to 0W, active power p s Approaching the active power absorbed by the load.

[0067] Figure 6 The load current i when the harmonic compensation method is used is shown in FIG. labc , active power filter output current i ggaabc , grid output current i sabc The simulation waveform diagram and simulation parameters are shown in Table 1. Before the start of harmonic compensation, the power grid has reached balance; after the start of harmonic compensation, the harmonic current content of the power grid is greatly reduced, and its FFT analysis is as follows Figure 7 shown.

[0068] Table 1: Simulation parameters.

[0069]

[0070]

[0071] Figure 7 Shown Figure 6 China grid current i sabc FFT analysis of the grid output current i sabc The THD value is 3.58% (the fundamental current amplitude is 45.85A), which can be adjusted by adjusting the short-circuit coefficient K, line impedance L gg , voltage controller parameters (amplitude compensation, phase compensation), etc. are further optimized.

[0072] Embodiment 2:

[0073] This implementation method proposes a control system of a network-type active power filter, including the following processes:

[0074] A control system for a grid-type active power filter, comprising:

[0075] The harmonic instruction generation module is configured to: generate a harmonic voltage instruction according to the voltage at the common connection point of the grid-type active power filter;

[0076] The voltage control module is configured as follows: using the filter capacitor voltage and the phase command of the filter capacitor voltage as the input of the first dq transformation, using the sum of the d-axis harmonic voltage command, the fundamental voltage command and the d-axis component of the first dq transformation as the first input of the voltage control unit, using the sum of the q-axis harmonic voltage command and the q-axis component of the first dq transformation as the second input of the voltage control unit, the voltage control unit generates a control command according to the first input and the second input to control the output voltage of the grid-forming active power filter, when the difference in amplitude and phase between the output voltage of the grid-forming active power filter and the voltage at the common connection point is less than the corresponding threshold value, the grid-forming active power filter is connected to the grid and operated.

[0077] In the voltage control module of this implementation, the phase command of the converter output current and the filter capacitor voltage is used as the input of the second dq conversion, and the current control command output by the voltage control unit and the output of the second dq conversion are used as the input of the current control unit;

[0078] The output of the current control unit and the phase command of the filter capacitor voltage are used as inputs of the third dq conversion, and the output of the third dq conversion is used as input of the PWM modulator to realize control of the converter.

[0079] The system of this implementation further includes a power control module, wherein the power control module is configured to:

[0080] The output active power and output reactive power of the mesh active power filter are generated according to the output current of the mesh active power filter and the voltage at the common connection point, and the output reactive power instruction of the mesh active power filter is obtained according to the input current of the nonlinear load and the voltage at the common connection point. The output active power, the output reactive power and the output reactive power instruction are used as inputs of the power control unit. The reactive power control part of the power control unit generates a fundamental voltage instruction, and the active power control part of the power control unit generates a power angle. The power angle is added to the voltage phase at the common connection point to generate a phase instruction of the filter capacitor voltage.

[0081] In the harmonic instruction generation module of the present implementation, the harmonic voltage component at the common connection point is generated through harmonic extraction according to the voltage at the common connection point, and the phase instruction of the harmonic voltage component at the common connection point and the filter capacitor voltage is used as the input of the fourth dq transformation. After the harmonic instruction calculation, the d-axis harmonic voltage instruction and the q-axis harmonic voltage instruction are obtained.

[0082] The specific working details of each module are the same as the control method in Example 1 and will not be repeated here.

[0083] It is understandable that the above-mentioned modules can be respectively or completely combined into one or several other units to constitute, or some of the units can also be split into multiple smaller units in function to constitute, which can achieve the same operation without affecting the realization of the technical effects of the embodiments of the present application. The above-mentioned units are divided based on logical functions. In practical applications, the functions of a unit can also be realized by multiple units, or the functions of multiple units can be realized by one unit. In other embodiments of the present application, the system can also include other units. In practical applications, these functions can also be implemented with the assistance of other units, and can be implemented by the collaboration of multiple units.

[0084] According to another embodiment of the present application, the system described in this embodiment can be constructed, and the control method of the embodiment of the present application can be implemented by running a computer program (including program code) capable of executing the steps involved in the corresponding method described in Example 1 on a general computing device such as a computer including processing elements and storage elements such as a central processing unit (CPU), random access memory (RAM), and read-only memory (ROM). The computer program can be recorded on, for example, a computer-readable recording medium, and loaded into the above-mentioned computing device through the computer-readable recording medium and run therein.

[0085] Embodiment 3:

[0086] This implementation provides an electronic device, which includes a processor, a communication interface, and a computer-readable storage medium, wherein the processor, the communication interface, and the computer-readable storage medium may be connected via a bus or other means.

[0087] Among them, the communication interface is used to receive and send data, the computer-readable storage medium can be stored in the memory of the electronic device, the computer-readable storage medium is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer-readable storage medium.

[0088] A processor (or CPU (Central Processing Unit)) is the computing core and control core of an electronic device, which is suitable for implementing one or more instructions, and specifically suitable for loading and executing one or more instructions to implement corresponding method flows or corresponding functions.

[0089] The processor is configured to perform the following process:

[0090] generating a harmonic voltage command according to the voltage at the common connection point of the grid-type active power filter;

[0091] According to the filter capacitor voltage and the phase command of the filter capacitor voltage as the input of the first dq transformation, the sum of the d-axis harmonic voltage command, the fundamental voltage command and the d-axis component of the first dq transformation is used as the first input of the voltage control unit, and the sum of the q-axis harmonic voltage command and the q-axis component of the first dq transformation is used as the second input of the voltage control unit;

[0092] The voltage control unit generates a control instruction according to the first input and the second input to control the output voltage of the grid-type active power filter. When the difference in amplitude and phase between the output voltage of the grid-type active power filter and the voltage at the common connection point is less than the corresponding threshold value, the grid-type active power filter is connected to the grid and operated.

[0093] Embodiment 4:

[0094] This implementation provides a computer-readable storage medium (Memory), which is a memory device in an electronic device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the electronic device and, of course, extended storage media supported by the electronic device. The computer-readable storage medium provides a storage space that stores the processing system of the electronic device.

[0095] In addition, the storage space also stores one or more instructions suitable for being loaded and executed by the processor, and these instructions may be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here may be a high-speed RAM memory, or a non-volatile memory (non-volatile memory), such as at least one disk storage; optionally, it may also be at least one computer-readable storage medium located away from the aforementioned processor.

[0096] In one embodiment, the computer-readable storage medium stores one or more instructions; the processor loads and executes the one or more instructions stored in the computer-readable storage medium to implement the following process:

[0097] generating a harmonic voltage command according to the voltage at the common connection point of the grid-type active power filter;

[0098] According to the filter capacitor voltage and the phase command of the filter capacitor voltage as the input of the first dq transformation, the sum of the d-axis harmonic voltage command, the fundamental voltage command and the d-axis component of the first dq transformation is used as the first input of the voltage control unit, and the sum of the q-axis harmonic voltage command and the q-axis component of the first dq transformation is used as the second input of the voltage control unit;

[0099] The voltage control unit generates a control instruction according to the first input and the second input to control the output voltage of the grid-type active power filter. When the difference in amplitude and phase between the output voltage of the grid-type active power filter and the voltage at the common connection point is less than the corresponding threshold value, the grid-type active power filter is connected to the grid and operated.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control method for a grid-type active power filter, characterized in that: The process includes: generating a harmonic voltage command according to the voltage at the common connection point of the grid-type active power filter; According to the filter capacitor voltage and the phase command of the filter capacitor voltage as the input of the first dq transformation, the sum of the d-axis harmonic voltage command, the fundamental voltage command and the d-axis component of the first dq transformation is used as the first input of the voltage control unit, and the sum of the q-axis harmonic voltage command and the q-axis component of the first dq transformation is used as the second input of the voltage control unit; The voltage control unit generates a control instruction according to the first input and the second input to control the output voltage of the grid-forming active power filter. When the difference in amplitude and phase between the output voltage of the grid-forming active power filter and the voltage at the common connection point is less than the corresponding threshold value, the grid-forming active power filter is connected to the grid for operation; Generate output active power and output reactive power of the grid-type active power filter according to the output current of the grid-type active power filter and the voltage at the common connection point, obtain output reactive power instruction of the grid-type active power filter according to the input current of the nonlinear load and the voltage at the common connection point, and use the output active power, output reactive power and output reactive power instruction as inputs of the power control unit; The reactive power control part of the power control unit generates a fundamental voltage command, and the active power control part of the power control unit generates a power angle, which is added to the voltage phase at the common connection point to generate a phase command of the filter capacitor voltage; When the difference in amplitude and phase between the output voltage of the grid-forming active power filter and the voltage at the common connection point is less than the corresponding threshold value, a relay drive instruction is generated to close the switch between the grid-forming active power filter and the nonlinear load, so that the grid-forming active power filter is connected to the grid for operation; According to the voltage at the common connection point, the harmonic voltage component at the common connection point is generated through harmonic extraction, and the phase instruction of the harmonic voltage component at the common connection point and the filter capacitor voltage is used as the input of the fourth dq transformation. After the harmonic instruction calculation, the d-axis harmonic voltage instruction and the q-axis harmonic voltage instruction are obtained.

2. The control method of the grid-type active power filter according to claim 1, characterized in that: The phase command of the converter output current and the filter capacitor voltage is used as the input of the second dq conversion, and the current control command output by the voltage control unit and the output of the second dq conversion are used as the input of the current control unit; The output of the current control unit and the phase command of the filter capacitor voltage are used as inputs of the third dq transformation, and the output of the third dq transformation is used as input of the PWM modulator to realize control of the converter.

3. A control system for a grid-type active power filter, characterized in that: include: The harmonic instruction generation module is configured to: generate a harmonic voltage instruction according to the voltage at the common connection point of the grid-type active power filter; in the harmonic instruction generation module, a harmonic voltage component at the common connection point is generated through harmonic extraction according to the voltage at the common connection point, and a phase instruction of the harmonic voltage component at the common connection point and the filter capacitor voltage is used as an input of the fourth dq transformation, and a d-axis harmonic voltage instruction and a q-axis harmonic voltage instruction are obtained after harmonic instruction calculation; The voltage control module is configured to: use the filter capacitor voltage and the phase command of the filter capacitor voltage as the input of the first dq transformation, use the sum of the d-axis harmonic voltage command, the fundamental voltage command and the d-axis component of the first dq transformation as the first input of the voltage control unit, use the sum of the q-axis harmonic voltage command and the q-axis component of the first dq transformation as the second input of the voltage control unit, the voltage control unit generates a control command according to the first input and the second input to control the output voltage of the grid-forming active power filter, and when the difference in amplitude and phase between the output voltage of the grid-forming active power filter and the voltage at the common connection point is less than the corresponding threshold value, the grid-forming active power filter is grid-connected and operated; It also includes a power control module, wherein the power control module is configured to: The output active power and output reactive power of the mesh active power filter are generated according to the output current of the mesh active power filter and the voltage at the common connection point, and the output reactive power instruction of the mesh active power filter is obtained according to the input current of the nonlinear load and the voltage at the common connection point. The output active power, the output reactive power and the output reactive power instruction are used as inputs of the power control unit. The reactive power control part of the power control unit generates a fundamental voltage instruction, and the active power control part of the power control unit generates a power angle. The power angle is added to the voltage phase at the common connection point to generate a phase instruction of the filter capacitor voltage.

4. The control system of the grid-type active power filter according to claim 3, characterized in that: In the voltage control module, the phase command of the converter output current and the filter capacitor voltage is used as the input of the second dq conversion, and the current control command output by the voltage control unit and the output of the second dq conversion are used as the input of the current control unit; The output of the current control unit and the phase command of the filter capacitor voltage are used as inputs of the third dq transformation, and the output of the third dq transformation is used as input of the PWM modulator to realize control of the converter.

5. A computer device, characterized in that: include: A processor and a computer readable storage medium; a processor adapted to execute a computer program; A computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium, and when the computer program is executed by the processor, the control method of the grid-type active power filter according to any one of claims 1 to 2 is implemented.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and the computer program is suitable for being loaded by a processor and executing the control method of the grid-type active power filter according to any one of claims 1-2.

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