A control method and device for parallel APF

Abstract

The present invention provides a control method and device for a parallel APF. The method includes: obtaining the real-time current of the load side of the power grid and the AC side of the parallel APF, as well as the positive bus voltage and the negative bus voltage of the DC side of the parallel APF; performing PI calculation based on the positive bus voltage and the negative bus voltage, and the real-time current of the AC side of the parallel APF to obtain the fundamental voltage, which has the same phase as the voltage of the power supply side of the power grid; performing harmonic analysis based on the real-time current of the load side and the AC side of the parallel APF to obtain the harmonic voltage, which is used to characterize the harmonic situation on the load side; determining the target voltage of the AC side of the parallel APF based on the fundamental voltage and the harmonic voltage, and determining the duty cycle of each switch tube in the parallel APF based on the target voltage to adjust the real-time voltage of the AC side of the parallel APF to the target voltage. The present invention can improve the compensation accuracy of the parallel APF for current harmonics.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power grid, and in particular to a control method and device for parallel APF. Background Art

[0002] With the advent of the era of big data, cloud computing, and the Internet of Things, nonlinear loads such as large servers are increasing, and have gradually become one of the important sources of harmonic pollution in distribution networks. Harmonic pollution leads to a decline in power quality, which has a significant impact on the safe and economical operation of power supply and power consumption equipment. Harmonic suppression is an important issue that needs to be urgently addressed in the development of modern power. The parallel active power filter (APF) can be controlled into a current source, and through appropriate control algorithms, it can be used to compensate for current harmonics in the power system. Therefore, APF has received widespread attention.

[0003] For traditional parallel active power filters, proportional integral (PI) control is mostly used. Since the active power filter needs to compensate for current harmonics of multiple frequencies, the PI controller cannot achieve zero-error tracking of the AC signal. In order to achieve high-precision compensation of multiple current harmonics, multi-pulse rectifier (MPR) control is required for parallel APF. Since the gain of resonant control at the resonant frequency is infinite, compensation of current harmonics of various frequencies can be achieved.

[0004] However, the current current control loop design does not take into account the changes in grid component parameters. In practical applications, due to frequent load changes and the different working environment temperatures, the parameters of the inductance components of the converter and the grid will change, resulting in large errors and low compensation accuracy when the parallel APF compensates for various frequency current harmonics. Summary of the invention

[0005] The present invention provides a control method and device for a parallel APF, which can reduce the error when the parallel APF compensates for current harmonics and improve the compensation accuracy of the parallel APF for current harmonics.

[0006] In a first aspect, the present invention provides a control method for a parallel APF, comprising: obtaining the real-time current on the load side of a power grid and the AC side of a parallel APF, and the positive bus voltage and the negative bus voltage on the DC side of the parallel APF; performing PI calculation based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain a fundamental voltage, and the fundamental voltage has the same phase as the voltage on the power supply side of the power grid; performing harmonic analysis based on the real-time current on the load side and the AC side of the parallel APF to obtain a harmonic voltage, and the harmonic voltage is used to characterize the harmonic situation on the load side; determining the target voltage on the AC side of the parallel APF based on the fundamental voltage and the harmonic voltage, and determining the duty cycle of each switch tube in the parallel APF based on the target voltage to adjust the real-time voltage on the AC side of the parallel APF to the target voltage.

[0007] The present invention provides a control method for a parallel APF, which performs PI calculation on a positive bus voltage and a negative bus voltage, and a real-time current on an AC side of the parallel APF to obtain a fundamental voltage, performs harmonic analysis based on the real-time current on a load side and an AC side of the parallel APF to obtain a harmonic voltage, determines a target voltage on the AC side of the parallel APF based on the fundamental voltage and the harmonic voltage, and determines a duty cycle of each switch tube in the parallel APF based on the target voltage to adjust the real-time voltage on the AC side of the parallel APF to the target voltage. Since the fundamental voltage has the same phase as the voltage on the power supply side of the power grid, it can characterize the fundamental condition on the power supply side; the harmonic voltage is used to characterize the harmonic condition on the load side, that is, it characterizes the real-time changes in the parameters of the power grid components on the load side. The target voltage on the AC side of the parallel APF determined in this way takes into account both the fundamental condition on the power supply side and the real-time changes in the parameters of the power grid components on the load side, so that the final harmonic compensation on the load side is adapted to the changes in the parameters of the power grid components, reducing the error when the parallel APF compensates for current harmonics and improving the compensation accuracy of the parallel APF for current harmonics.

[0008] In one possible implementation, PI calculation is performed based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain the fundamental voltage, which also includes: performing DQ conversion on the real-time current on the load side of the power grid and the AC side of the parallel APF, respectively, to obtain the D-axis component, Q-axis component and zero-axis component of the real-time current on the load side of the power grid, and the D-axis component, Q-axis component and zero-axis component of the real-time current on the AC side of the parallel APF.

[0009] In one possible implementation, a PI calculation is performed based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain the fundamental voltage, including: performing total voltage control and equalizing voltage control based on the positive bus voltage and the negative bus voltage to obtain a target value of the D-axis component and a target value of the zero-axis component of the fundamental voltage; performing a PI calculation based on the error between the target value of the D-axis component of the fundamental voltage and the D-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the D-axis component of the fundamental voltage; performing a PI calculation based on the error between the zero and Q-axis components of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the Q-axis component of the fundamental voltage; performing a PI calculation based on the target value of the zero-axis component of the fundamental voltage and the error between the zero-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the zero-axis component of the fundamental voltage; determining the fundamental voltage based on the D-axis component, Q-axis component, and zero-axis component of the fundamental voltage.

[0010] In one possible implementation, total voltage control and equalizing voltage control are performed based on the positive bus voltage and the negative bus voltage to obtain a target value of the D-axis component and a target value of the zero-axis component of the fundamental voltage, including: calculating the sum of the positive bus voltage and the negative bus voltage, and performing PI calculation based on the error between the target value and the real-time value of the sum to obtain the target value of the D-axis component of the fundamental voltage; calculating the difference between the positive bus voltage and the negative bus voltage, and performing PI calculation based on the error between the target value and the real-time value of the difference to obtain the target value of the zero-axis component of the fundamental voltage.

[0011] In one possible implementation, the transfer function of the CVPI controller is:

[0012]

[0013] Among them, W c '(s) is the function value of the transfer function of the CVPI controller, k cp is the proportional gain coefficient of the CVPI controller, k ci is the integral gain coefficient of the CVPI controller, ω0 is the angular frequency of the fundamental voltage, L i is the equivalent inductance between the parallel APF and the grid, L g is the equivalent inductance of the power supply side of the grid, is the sum of the equivalent inductance on the grid supply side and the equivalent inductance between the parallel APF and the grid, r is the equivalent resistance between the parallel APF and the grid, s is the input quantity of the transfer function of the CVPI controller, and j is the imaginary unit.

[0014] In a possible implementation, harmonic analysis is performed based on the real-time current on the load side and the AC side of the parallel APF to obtain the harmonic voltage, including: determining the D-axis component of the harmonic voltage based on the D-axis component of the real-time current on the load side, the D-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determining the Q-axis component of the harmonic voltage based on the Q-axis component of the real-time current on the load side, the Q-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determining the zero-axis component of the harmonic voltage based on the zero-axis component of the real-time current on the load side, the zero-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determining the harmonic voltage based on the D-axis component, Q-axis component, and zero-axis component of the harmonic voltage.

[0015] In one possible implementation, the transfer function of the multi-harmonic controller is:

[0016]

[0017] Among them, G R1 (s) is the function value of the transfer function of the multi-harmonic controller, h is the harmonic order, k is hr is the gain of the multiharmonic controller at the hth harmonic frequency, ω c is the open-loop cut-off frequency of the multi-harmonic controller, T s is the period of the fundamental voltage, ω0 is the angular frequency of the fundamental voltage, and s is the input quantity of the transfer function of the multi-harmonic controller.

[0018] In the second aspect, an embodiment of the present invention provides a control device for a parallel APF, including: a communication module and a processing module, the communication module being used to obtain the real-time current on the load side of the power grid and the AC side of the parallel APF, and the positive bus voltage and the negative bus voltage on the DC side of the parallel APF; the processing module being used to perform PI calculation based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain a fundamental voltage, and the fundamental voltage has the same phase as the voltage on the power supply side of the power grid; the processing module is also used to perform harmonic analysis based on the real-time current on the load side and the AC side of the parallel APF to obtain a harmonic voltage, and the harmonic voltage is used to characterize the harmonic situation on the load side; the processing module is also used to determine the target voltage on the AC side of the parallel APF based on the fundamental voltage and the harmonic voltage, and based on the target voltage, determine the duty cycle of each switch tube in the parallel APF to adjust the real-time voltage on the AC side of the parallel APF to the target voltage.

[0019] In one possible implementation, the processing module is also used to perform DQ conversion on the real-time current on the load side of the power grid and the AC side of the parallel APF, respectively, to obtain the D-axis component, Q-axis component and zero-axis component of the real-time current on the load side of the power grid, and the D-axis component, Q-axis component and zero-axis component of the real-time current on the AC side of the parallel APF.

[0020] In one possible implementation, the processing module is specifically used to perform total voltage control and equalizing voltage control based on the positive bus voltage and the negative bus voltage to obtain a target value of the D-axis component and a target value of the zero-axis component of the fundamental voltage; perform PI calculation based on the error between the target value of the D-axis component of the fundamental voltage and the D-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the D-axis component of the fundamental voltage; perform PI calculation based on the error between the zero and Q-axis components of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the Q-axis component of the fundamental voltage; perform PI calculation based on the target value of the zero-axis component of the fundamental voltage and the error between the zero-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the zero-axis component of the fundamental voltage; determine the fundamental voltage based on the D-axis component, Q-axis component, and zero-axis component of the fundamental voltage.

[0021] In one possible implementation, the processing module is specifically used to calculate the sum of the positive bus voltage and the negative bus voltage, and perform PI calculation based on the error between the target value and the real-time value of the sum to obtain the target value of the D-axis component of the fundamental voltage; calculate the difference between the positive bus voltage and the negative bus voltage, and perform PI calculation based on the error between the target value and the real-time value of the difference to obtain the target value of the zero-axis component of the fundamental voltage.

[0022] In one possible implementation, the transfer function of the CVPI controller is:

[0023]

[0024] Among them, W c '(s) is the function value of the transfer function of the CVPI controller, k cp is the proportional gain coefficient of the CVPI controller, k ci is the integral gain coefficient of the CVPI controller, ω0 is the angular frequency of the fundamental voltage, L i is the equivalent inductance between the parallel APF and the grid, L g is the equivalent inductance of the power supply side of the grid, is the sum of the equivalent inductance on the grid supply side and the equivalent inductance between the parallel APF and the grid, r is the equivalent resistance between the parallel APF and the grid, s is the input quantity of the transfer function of the CVPI controller, and j is the imaginary unit.

[0025] In one possible implementation, the processing module is specifically used to determine the D-axis component of the harmonic voltage based on the D-axis component of the real-time current on the load side, the D-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determine the Q-axis component of the harmonic voltage based on the Q-axis component of the real-time current on the load side, the Q-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determine the zero-axis component of the harmonic voltage based on the zero-axis component of the real-time current on the load side, the zero-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determine the harmonic voltage based on the D-axis component, Q-axis component, and zero-axis component of the harmonic voltage.

[0026] In one possible implementation, the transfer function of the multi-harmonic controller is:

[0027]

[0028] Among them, G R1 (s) is the function value of the transfer function of the multi-harmonic controller, h is the harmonic order, k is hr is the gain of the multiharmonic controller at the hth harmonic frequency, ω c is the open-loop cut-off frequency of the multi-harmonic controller, T s is the period of the fundamental voltage, ω0 is the angular frequency of the fundamental voltage, and s is the input quantity of the transfer function of the multi-harmonic controller.

[0029] In a third aspect, an embodiment of the present invention provides an electronic device, characterized in that the electronic device includes a memory and a processor, the memory stores a computer program, and the processor is used to call and run the computer program stored in the memory to perform the steps of the above-mentioned first aspect and any possible implementation method of the first aspect.

[0030] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores a computer program, and is characterized in that when the computer program is executed by a processor, it implements the steps of the above-mentioned first aspect and any possible implementation method of the first aspect.

[0031] The technical effects brought about by any implementation method of the second to fourth aspects mentioned above can refer to the technical effects brought about by the corresponding implementation method of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 Schematic diagram of a three-phase four-wire three-level parallel active power filter structure provided by an embodiment of the present invention;

[0034] Figure 2 is a control logic diagram of a control method for a parallel APF provided by an embodiment of the present invention;

[0035] Figure 3 It is a flow chart of a control method of a parallel APF provided by an embodiment of the present invention;

[0036] Figure 4 It is a block diagram of a fundamental current loop control based on a complex vector provided by an embodiment of the present invention;

[0037] Figure 5 is a Bode diagram corresponding to a current open-loop transfer function provided by an embodiment of the present invention;

[0038] Figure 6 is a Bode diagram corresponding to a current closed-loop transfer function based on a CVPI controller provided in an embodiment of the present invention;

[0039] Figure 7 is a Bode diagram corresponding to another current closed-loop transfer function based on a CVPI controller provided in an embodiment of the present invention;

[0040] Figure 8 It is a composite current control block diagram based on CVPI and multi-resonance control provided by an embodiment of the present invention;

[0041] Fig. 9 It is a Nyquist diagram of the current open-loop transfer function under a multi-harmonic controller of a CVPI+18th resonant frequency with different gain coefficients provided by an embodiment of the present invention;

[0042] Fig.10 It is a Bode diagram of the current open-loop transfer function of a multi-harmonic controller of CVPI+18th resonant frequency before and after a phase compensation link is added to a multi-harmonic controller provided by an embodiment of the present invention;

[0043] Fig.11 It is a Bode diagram of a resonant control current open-loop system based on CVPI+multi-harmonic frequency provided by an embodiment of the present invention;

[0044] Fig.12It is a current waveform and grid current spectrum diagram during CVPI+multi-resonance control provided by an embodiment of the present invention;

[0045] Fig.13 It is a compensation current waveform diagram of a load and a parallel APF when a load is suddenly added, provided by an embodiment of the present invention;

[0046] Fig.14 is a structural schematic diagram of a control device for a parallel APF provided by an embodiment of the present invention;

[0047] Fig.15 It is a structural schematic diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0049] In the description of the present invention, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, "at least one" and "plurality" refer to two or more. The words "first", "second", etc. do not limit the quantity and execution order, and the words "first", "second", etc. do not limit them to be different.

[0050] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way for easy understanding.

[0051] In addition, the terms "including" and "having" and any variations thereof mentioned in the description of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include other steps or modules that are not listed, or may optionally include other steps or modules that are inherent to these processes, methods, products or devices.

[0052] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following will be described through specific embodiments in conjunction with the accompanying drawings of the present invention.

[0053] As the background technology, there is currently a technical problem that when a parallel APF is used to compensate for various frequency current harmonics, the error is large and the compensation accuracy is low.

[0054] To solve this technical problem, an embodiment of the present invention provides a control method for a parallel APF, which is applied to a parallel active power filter structure. Figure 1 The schematic diagram of a three-phase four-wire three-level parallel active power filter structure provided by an embodiment of the present invention. The nonlinear load of the three-phase power grid is a three-phase four-wire diode rectifier bridge; the three-level voltage source converter is connected to the power grid through an output filter to form a parallel active filter. Figure 1 Shown: u sa ,u sb and u sc are the three-phase voltages on the power supply side of the grid, i sa ,i sb and i sc are the three-phase currents on the power supply side of the grid, i s0 is the neutral line current, L g is the equivalent inductance of the power supply side of the grid, L i is the equivalent inductance between the parallel APF and the grid, r is the equivalent resistance between the parallel APF and the grid, U P is the positive bus voltage on the DC side of the parallel APF, U N is the negative bus voltage on the DC side of the parallel APF, C is the positive and negative bus capacitance on the DC side of the parallel APF, i ca 、i cb 、i cc and i c0 is the compensation current output by the parallel APF, i La 、i Lb 、i Lc and i L0 is the load current on the load side of the power grid.

[0055] Figure 2 A control logic diagram of a control method for a parallel APF provided by an embodiment of the present invention. The control logic of the control method for a parallel APF provided by an embodiment of the present invention includes two parts: DC voltage control and AC current control. Considering the problem of DC bus voltage balance, a voltage balance control is set on the basis of total voltage control, and its feedback signal is the DC side positive and negative bus voltage difference U dc =U P -U NThe current control part is composed of a fundamental current loop and a harmonic current loop. The command of the fundamental d-axis current component control loop is the output of the total voltage loop to achieve stable control of the bus voltage. The command of the q-axis current component control loop is 0 to achieve the same phase of the fundamental current and voltage. Both the d-axis and q-axis current loops use CVPI controllers. The zero-sequence current loop command is the output of the voltage-balanced control loop. By adjusting the zero-sequence current, the positive and negative bus voltages are balanced. The loop uses a PI controller. The harmonic current control loop introduces a multi-harmonic controller to achieve high-precision compensation of each harmonic on the load side. The multi-harmonic controller can be flexibly designed for any harmonic.

[0056] based on Figure 1 and Figure 2 , Figure 3 A flow chart of a control method of a parallel APF provided in an embodiment of the present invention. The execution subject of the method is a control device of the parallel APF. The method includes steps S101-S103.

[0057] S101, obtaining the real-time current of the load side of the power grid and the AC side of the parallel APF, and the positive bus voltage and the negative bus voltage of the DC side of the parallel APF.

[0058] S102: Perform PI calculation based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain the fundamental voltage.

[0059] In the embodiment of the present application, the fundamental voltage has the same phase as the voltage on the power supply side of the power grid.

[0060] As a possible implementation manner, the control device may determine the fundamental voltage based on steps S1021 - S1025 .

[0061] S1021. Perform total voltage control and voltage sharing control based on the positive bus voltage and the negative bus voltage to obtain a target value of a D-axis component and a target value of a zero-axis component of the fundamental voltage;

[0062] As a possible implementation manner, the control device may determine the target value of the D-axis component and the target value of the zero-axis component of the fundamental voltage based on steps A1-A2.

[0063] A1. Calculate the sum of the positive bus voltage and the negative bus voltage, and perform PI calculation based on the error between the target value and the real-time value of the sum to obtain the target value of the D-axis component of the fundamental voltage.

[0064] A2. Calculate the difference between the positive bus voltage and the negative bus voltage, and perform PI calculation based on the error between the target value and the real-time value of the difference to obtain the target value of the zero-axis component of the fundamental voltage.

[0065] S1022, based on the error between the target value of the D-axis component of the fundamental voltage and the D-axis component of the real-time current on the AC side of the parallel APF, and the CVPI controller, perform PI calculation to obtain the D-axis component of the fundamental voltage.

[0066] S1023, based on the error between the Q-axis component of the real-time current on the AC side of the zero and parallel APFs, and the CVPI controller, perform PI calculation to obtain the Q-axis component of the fundamental voltage.

[0067] S1024, based on the target value of the zero-axis component of the fundamental voltage and the error between the zero-axis component of the real-time current on the AC side of the parallel APF, and the CVPI controller, perform PI calculation to obtain the zero-axis component of the fundamental voltage;

[0068] S1025 . Determine the fundamental voltage based on the D-axis component, the Q-axis component, and the zero-axis component of the fundamental voltage.

[0069] In some embodiments, the transfer function of the CVPI controller is:

[0070]

[0071] Among them, W c '(s) is the function value of the transfer function of the CVPI controller, k cp is the proportional gain coefficient of the CVPI controller, k ci is the integral gain coefficient of the CVPI controller, ω0 is the angular frequency of the fundamental voltage, L i is the equivalent inductance between the parallel APF and the grid, L g is the equivalent inductance of the power supply side of the grid, is the sum of the equivalent inductance on the grid supply side and the equivalent inductance between the parallel APF and the grid, r is the equivalent resistance between the parallel APF and the grid, s is the input quantity of the transfer function of the CVPI controller, and j is the imaginary unit.

[0072] Optionally, before step S102, the control device may perform DQ conversion on the real-time current on the load side of the power grid and the AC side of the parallel APF, respectively, to obtain the D-axis component, Q-axis component and zero-axis component of the real-time current on the load side of the power grid, and the D-axis component, Q-axis component and zero-axis component of the real-time current on the AC side of the parallel APF.

[0073] It should be noted that, from the mathematical model of the dq0 coordinate system of the three-level converter, it can be seen that there is coupling between the dq components of the AC side current. In the embodiment of the present invention, the PI controller is improved to a CVPI controller to achieve current decoupling, and the zero point of the CVPI controller is set as the pole of the complex vector model in the dq0 coordinate system to design the current control loop. The complex vector of the dq complex plane is expressed as Depend on Figure 2 The control logic diagram can be obtained, and the fundamental current loop control block diagram based on complex vector is as follows Figure 4 The CVPI controller transfer function of the current control loop is shown in Figure 2. c (s) is:

[0074]

[0075] Among them, k cp is the proportional gain coefficient of the CVPI controller, k ci is the integral gain coefficient of the CVPI controller, and ω0 is the angular frequency of the fundamental voltage.

[0076] It should be noted that for high-power APF devices, the current control loop bandwidth is much smaller than the switching frequency fs, the influence of SPWM modulation can be ignored, and the corresponding transfer function is approximately 1. Therefore, the current open-loop transfer function W of the CVPI controller is introduced. o (s) can be expressed as:

[0077]

[0078] Let k ci / k cp =r / (L i +L g ), we can get the current closed-loop transfer function W c (s) is:

[0079]

[0080] From the above formula, we can see that by using the CVPI controller and designing it according to the principle of zero-pole cancellation, the current loop can be decoupled and reduced to a first-order system. cp Determined by the current control loop bandwidth, for example, taking a 20kVA three-level APF device as an example, the corresponding parameters are Lg = 0.05mH, Li = 0.9mH, resistance r = 0.5Ω, the switching frequency of the converter fs = 10kHz, and the current control loop bandwidth is 1500Hz, and k can be calculated cp =9.2, k ci =4869. The Bode plot corresponding to the current open-loop transfer function is as follows Figure 5 As shown, the current loop phase margin is 90° and the control system is stable. Figure 5 (a) is the amplitude-frequency characteristic curve. Figure 5 (b) in the figure is the phase-frequency characteristic curve.

[0081] In practical applications, since the load often changes and the parameters of the inductance components of the converter and the power grid change with the different working environment temperatures, the robustness of the control loop must be considered when designing the control system. From the above formula, according to the displacement theorem of Laplace transform, the current closed-loop transfer function W in the stationary coordinate system can be obtained: c (s) is:

[0082]

[0083] make is the sum of the equivalent inductance on the power supply side of the grid and the equivalent inductance between the parallel APF and the grid. The closed-loop transfer function of the current control loop in the stationary coordinate system under the general PI controller with current decoupling can be obtained as follows:

[0084]

[0085] Assuming that the actual inductance value is m times the theoretical value due to different environments, Figure 6 and Figure 7 The Bode plots of the current closed-loop transfer function of the PI controller with current decoupling and the CVPI controller when m = 0.5, 1.0 and 1.5 respectively. Figure 6 and Figure 7 It can be seen that if the parameter estimation is accurate, both control methods can achieve dq current component decoupling, fundamental frequency signal difference-free control, and have good steady-state performance. If there is a deviation in the parameter estimation, when the current decoupling PI control strategy is adopted, the current closed-loop characteristic gain changes significantly with the inductance value, while the current closed-loop gain based on the CVPI controller is always 1 near the fundamental frequency, indicating that the current control loop based on the CVPI control method has better robustness.

[0086] The zero-axis current control loop is independent of the dq current control loop and can be designed separately. From the model of the controlled object, it can be seen that the corresponding loop is a first-order link. This paper adopts a PI controller and sets the bandwidth of the zero-axis current loop to 1500Hz. In order to ensure that the PI controller does not affect the phase at the bandwidth frequency, its turning frequency is set to 20Hz, and the proportional gain k0p=1.6 and the integral gain k0i=200 of the zero-axis current control loop PI controller are obtained.

[0087] S103: Perform harmonic analysis based on the real-time current on the load side and the AC side of the parallel APF to obtain harmonic voltage.

[0088] In the embodiment of the present application, the harmonic voltage is used to characterize the harmonic condition on the load side.

[0089] As a possible implementation manner, the control device may determine the harmonic voltage based on steps S1031 - S1034 .

[0090] S1031. Determine the D-axis component of the harmonic voltage based on the D-axis component of the real-time current on the load side, the D-axis component of the real-time current on the AC side of the parallel APF, and the multi-harmonic controller.

[0091] S1032. Determine the Q-axis component of the harmonic voltage based on the Q-axis component of the real-time current on the load side, the Q-axis component of the real-time current on the AC side of the parallel APF, and the multi-harmonic controller.

[0092] S1033. Determine the zero-axis component of the harmonic voltage based on the zero-axis component of the real-time current on the load side, the zero-axis component of the real-time current on the AC side of the parallel APF, and the multi-harmonic controller.

[0093] S1034. Determine the harmonic voltage based on the D-axis component, Q-axis component, and zero-axis component of the harmonic voltage.

[0094] In some embodiments, the transfer function of the multi-harmonic controller is:

[0095]

[0096] Among them, G R1 (s) is the function value of the transfer function of the multi-harmonic controller, h is the harmonic order, k is hr is the gain of the multiharmonic controller at the hth harmonic frequency, ω c is the open-loop cut-off frequency of the multi-harmonic controller, T s is the period of the fundamental voltage, ω0 is the angular frequency of the fundamental voltage, and s is the input quantity of the transfer function of the multi-harmonic controller.

[0097] It should be noted that for a three-phase symmetrical power supply system, the load current i L The harmonic frequencies are mainly negative sequence 5, 11, 17, positive sequence 7, 13, 19 and zero sequence 6, 9. The positive and negative sequence currents become ±6, ±12 and ±18 respectively (positive sequence harmonics are positive and negative sequence harmonics are negative). Since the multi-harmonic controller is the inner model of the cosine signal and the cosine function is an even function, the multi-harmonic controller can achieve open-loop high gain control under positive and negative angular frequencies. Based on the above analysis, a multi-harmonic controller with 6, 12 and 18 harmonic frequencies is designed to achieve high-precision control of harmonic currents. Let the transfer function GR(s) of the multi-harmonic controller be:

[0098]

[0099] Where: h is the harmonic order, khr is the gain of the multi-harmonic controller at the hth harmonic frequency. In order to improve the frequency adaptability of the multi-harmonic controller, the open-loop cutoff frequency ωc of the multi-harmonic controller is set to form a quasi-multi-harmonic controller.

[0100] The multi-harmonic controller will cause a 90° phase lag to the right of the resonant frequency. Figure 3 The phase curve of the current open-loop transfer function based on the CVPI controller shows that the phase is -90° at the compensated harmonic frequency. The introduction of the multi-harmonic controller of formula (6) will inevitably affect the stability of the control system. Therefore, it is necessary to design a phase compensation link for the multi-harmonic controller. The improved multi-harmonic controller GR1(s) can be expressed as:

[0101]

[0102] in:

[0103] Figure 8 This is a block diagram of a composite current control based on CVPI and multi-resonance control. Since each multi-harmonic controller and CVPI controller are connected in parallel, the parameter design method of a multi-harmonic controller can be analyzed in combination with the current control loop with CVPI controller, and the parameter design of other multi-harmonic controllers can be deduced in the same way. For high-order harmonic control, the influence of SPWM link and digital delay needs to be considered. The corresponding delay time is 1.5Ts, where Ts is the switching period of the converter. The delay link can be equivalent to the first-order inertia link, and the corresponding transfer function Gd(s) is:

[0104]

[0105] The current open-loop transfer function W under the multi-harmonic controller of CVPI+h sub-resonant frequency h (s) is:

[0106]

[0107] Considering the contradiction between the frequency selection range of the multi-harmonic controller and the resonant point frequency gain, ωc is generally taken between 3 and 5. h (s) Under the condition that the phase margin (PM) at the resonant frequency is greater than zero, determine the gain coefficient khr, and the PM expression is:

[0108]

[0109] Fig. 9 Nyquist diagram of the current open-loop transfer function under the multi-harmonic controller of CVPI+18th resonant frequency with different gain coefficients. Fig. 9The Nyquist diagram corresponding to the current open-loop transfer function of the multi-harmonic controller at the CVPI+18th resonant frequency with ωc=3 and different gain coefficients k18r, k18r varies from 300 to 600. It can be found that with the increase of k18r, the phase margin of the control loop gradually decreases. When k18r=600, the system phase margin is 25°.

[0110] Fig.10 Bode plot of the current open-loop transfer function of the multi-harmonic controller at CVPI+18th resonant frequency before and after adding the phase compensation link to the multi-harmonic controller. Fig.10 (a) is the amplitude-frequency characteristic curve. Fig.10 (b) is the phase-frequency characteristic curve. Fig.10 It can be seen that after the introduction of phase compensation, the phase margin of the current control loop at the resonant frequency is significantly improved.

[0111] Similarly, taking ωc=3, the gain coefficient of the corresponding multi-harmonic controller is determined based on the positive phase margin of the current control loop at the 6th and 12th harmonic frequencies, and k6r=1200 and k12r=900 are obtained. Figure 8 The current open-loop transfer function W of the multi-harmonic controller based on CVPI+multi-resonant frequency is shown as ch (s) is:

[0112]

[0113] Based on the above controller parameter design, the Bode plot corresponding to the current open-loop transfer function of the proposed control method can be obtained as follows: Fig.11 shown. Fig.11 The Bode diagram of the resonant control current open-loop system based on CVPI+multi-harmonic frequency. Figure 4 Compared with the CVPI control shown in the figure, it can be seen that after the multi-resonance control with phase compensation is introduced, the bandwidth of the current control loop is not affected, but due to the delay of the SPWM link and digital implementation, the phase margin of the current control loop is reduced to 45°, but the control system still has a certain stability margin. The zero-axis current is mainly composed of the third harmonic, and the multi-harmonic controller with three times the fundamental frequency can be superimposed. In a similar way, the parameters of the multi-harmonic controller are designed according to the phase margin at the resonant frequency. ωc=3 can be taken, and the gain coefficient of the multi-harmonic controller is k3r=950.

[0114] S104. Determine the target voltage of the AC side of the parallel APF based on the fundamental voltage and the harmonic voltage, and determine the duty cycle of each switch in the parallel APF based on the target voltage to adjust the real-time voltage of the AC side of the parallel APF to the target voltage.

[0115] The present invention provides a control method for a parallel APF, which performs PI calculation on a positive bus voltage and a negative bus voltage, and a real-time current on an AC side of the parallel APF to obtain a fundamental voltage, performs harmonic analysis based on the real-time current on a load side and an AC side of the parallel APF to obtain a harmonic voltage, determines a target voltage on the AC side of the parallel APF based on the fundamental voltage and the harmonic voltage, and determines a duty cycle of each switch tube in the parallel APF based on the target voltage to adjust the real-time voltage on the AC side of the parallel APF to the target voltage. Since the fundamental voltage has the same phase as the voltage on the power supply side of the power grid, it can characterize the fundamental condition on the power supply side; the harmonic voltage is used to characterize the harmonic condition on the load side, that is, it characterizes the real-time changes in the parameters of the power grid components on the load side. The target voltage on the AC side of the parallel APF determined in this way takes into account both the fundamental condition on the power supply side and the real-time changes in the parameters of the power grid components on the load side, so that the final harmonic compensation on the load side is adapted to the changes in the parameters of the power grid components, reducing the error when the parallel APF compensates for current harmonics and improving the compensation accuracy of the parallel APF for current harmonics.

[0116] For example, a three-phase four-wire three-level parallel APF is used as an example, and the hardware circuit and controller parameters of the system are shown in Table 1. The control system is composed of TMS320F2812.

[0117] Table 1

[0118]

[0119] Fig.12 The current waveform and grid current spectrum diagram of the CVPI+multi-resonance control of the parallel APF control method provided by the embodiment of the present invention. Fig.12 (a) is the current waveform. Fig.12 (b) is the grid current spectrum. When the load is 15kW, the a-phase related current waveform and grid current harmonic distribution, where i La 、i sa and i ca They are the load current, grid current and compensation current of phase a respectively. From the spectrum distribution of grid current, it can be seen that the characteristic subharmonic current of the load is obviously compensated, the quality of grid current is good, and the total harmonic distortion THD is 3.5%.

[0120] Fig.13 Figure 2 shows the load and compensation current waveform of the parallel APF when the load is suddenly added. It can be seen that the dynamic adjustment time of the control system is within one power frequency cycle, and the current control system has a faster tracking performance.

[0121] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0122] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0123] Fig.14 A schematic structural diagram of a control device for a parallel APF provided in an embodiment of the present invention is shown. The determination device 200 includes: a communication module 201 and a processing module 202 .

[0124] The communication module 201 is used to obtain the real-time current on the load side of the power grid and the AC side of the parallel APF, as well as the positive bus voltage and negative bus voltage on the DC side of the parallel APF.

[0125] The processing module 202 is used to perform PI calculation based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain the fundamental voltage, which has the same phase as the voltage on the power supply side of the power grid.

[0126] The processing module 202 is also used to perform harmonic analysis based on the real-time current on the load side and the AC side of the parallel APF to obtain the harmonic voltage, and the harmonic voltage is used to characterize the harmonic situation on the load side;

[0127] The processing module 202 is also used to determine the target voltage on the AC side of the parallel APF based on the fundamental voltage and the harmonic voltage, and determine the duty cycle of each switch tube in the parallel APF based on the target voltage to adjust the real-time voltage on the AC side of the parallel APF to the target voltage.

[0128] In one possible implementation, the processing module 202 is also used to perform DQ conversion on the real-time current on the load side of the power grid and the AC side of the parallel APF, respectively, to obtain the D-axis component, Q-axis component and zero-axis component of the real-time current on the load side of the power grid, and the D-axis component, Q-axis component and zero-axis component of the real-time current on the AC side of the parallel APF.

[0129] In one possible implementation, the processing module 202 is specifically used to perform total voltage control and voltage sharing control based on the positive bus voltage and the negative bus voltage to obtain a target value of the D-axis component and a target value of the zero-axis component of the fundamental voltage; perform PI calculation based on the error between the target value of the D-axis component of the fundamental voltage and the D-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the D-axis component of the fundamental voltage; perform PI calculation based on the error between the zero and Q-axis components of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the Q-axis component of the fundamental voltage; perform PI calculation based on the target value of the zero-axis component of the fundamental voltage and the error between the zero-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller to obtain the zero-axis component of the fundamental voltage; determine the fundamental voltage based on the D-axis component, Q-axis component, and zero-axis component of the fundamental voltage.

[0130] In one possible implementation, the processing module 202 is specifically used to calculate the sum of the positive bus voltage and the negative bus voltage, and perform PI calculation based on the error between the target value and the real-time value of the sum to obtain the target value of the D-axis component of the fundamental voltage; calculate the difference between the positive bus voltage and the negative bus voltage, and perform PI calculation based on the error between the target value and the real-time value of the difference to obtain the target value of the zero-axis component of the fundamental voltage.

[0131] In one possible implementation, the transfer function of the CVPI controller is:

[0132]

[0133] Among them, W c '(s) is the function value of the transfer function of the CVPI controller, k cp is the proportional gain coefficient of the CVPI controller, k ci is the integral gain coefficient of the CVPI controller, ω0 is the angular frequency of the fundamental voltage, L i is the equivalent inductance between the parallel APF and the grid, L g is the equivalent inductance of the power supply side of the grid, is the sum of the equivalent inductance on the grid supply side and the equivalent inductance between the parallel APF and the grid, r is the equivalent resistance between the parallel APF and the grid, s is the input quantity of the transfer function of the CVPI controller, and j is the imaginary unit.

[0134] In one possible implementation, the processing module 202 is specifically used to determine the D-axis component of the harmonic voltage based on the D-axis component of the real-time current on the load side, the D-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determine the Q-axis component of the harmonic voltage based on the Q-axis component of the real-time current on the load side, the Q-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determine the zero-axis component of the harmonic voltage based on the zero-axis component of the real-time current on the load side, the zero-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; determine the harmonic voltage based on the D-axis component, Q-axis component, and zero-axis component of the harmonic voltage.

[0135] In one possible implementation, the transfer function of the multi-harmonic controller is:

[0136]

[0137] Among them, G R1 (s) is the function value of the transfer function of the multi-harmonic controller, h is the harmonic order, k is hr is the gain of the multiharmonic controller at the hth harmonic frequency, ω c is the open-loop cut-off frequency of the multi-harmonic controller, T s is the period of the fundamental voltage, ω0 is the angular frequency of the fundamental voltage, and s is the input quantity of the transfer function of the multi-harmonic controller.

[0138] Fig.15 Schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. Fig.15 As shown, the electronic device 300 of this embodiment includes: a processor 301, a memory 302, and a computer program 303 stored in the memory 302 and executable on the processor 301. When the processor 301 executes the computer program 303, the steps in the above-mentioned method embodiments are implemented, for example Figure 3 Alternatively, when the processor 301 executes the computer program 303, the functions of each module / unit in the above-mentioned device embodiments are realized, for example, Fig.14 The functions of the communication module 201 and the processing module 202 are shown.

[0139] Exemplarily, the computer program 303 may be divided into one or more modules / units, which are stored in the memory 302 and executed by the processor 301 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments that can implement specific functions, and the instruction segments are used to describe the execution process of the computer program 303 in the electronic device 300. For example, the computer program 303 may be divided into Fig.14 The communication module 201 and the processing module 202 are shown.

[0140] The processor 301 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0141] The memory 302 may be an internal storage unit of the electronic device 300, such as a hard disk or memory of the electronic device 300. The memory 302 may also be an external storage device of the electronic device 300, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the electronic device 300. Further, the memory 302 may also include both an internal storage unit of the electronic device 300 and an external storage device. The memory 302 is used to store the computer program and other programs and data required by the terminal. The memory 302 may also be used to temporarily store data that has been output or is to be output.

[0142] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0143] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0144] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0145] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0146] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0147] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0148] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0149] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A control method for a parallel APF, characterized in that: include: Obtaining the real-time current on the load side of the power grid and the AC side of the parallel APF, as well as the positive bus voltage and negative bus voltage on the DC side of the parallel APF; Perform PI calculation based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain a fundamental voltage, wherein the fundamental voltage has the same phase as the voltage on the power supply side of the power grid; Performing harmonic analysis based on the real-time current on the load side and the AC side of the parallel APF to obtain a harmonic voltage, wherein the harmonic voltage is used to characterize the harmonic situation on the load side; Based on the fundamental voltage and the harmonic voltage, determine the target voltage of the AC side of the parallel APF, and based on the target voltage, determine the duty cycle of each switch tube in the parallel APF to adjust the real-time voltage of the AC side of the parallel APF to the target voltage; The PI calculation is performed based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain the fundamental voltage, and the method also includes: performing DQ conversion on the real-time current on the load side of the power grid and the AC side of the parallel APF, respectively, to obtain the D-axis component, Q-axis component and zero-axis component of the real-time current on the load side of the power grid, and the D-axis component, Q-axis component and zero-axis component of the real-time current on the AC side of the parallel APF; The PI calculation based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain the fundamental voltage includes: based on the positive bus voltage and the negative bus voltage, total voltage control and equalizing voltage control are performed to obtain the target value of the D-axis component and the target value of the zero-axis component of the fundamental voltage; based on the error between the target value of the D-axis component of the fundamental voltage and the D-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller, PI calculation is performed to obtain the D-axis component of the fundamental voltage; based on the error between zero and the Q-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller, PI calculation is performed to obtain the Q-axis component of the fundamental voltage; based on the target value of the zero-axis component of the fundamental voltage and the error between the zero-axis component of the real-time current on the AC side of the parallel APF, and a CVPI controller, PI calculation is performed to obtain the zero-axis component of the fundamental voltage; the fundamental voltage is determined based on the D-axis component, Q-axis component and zero-axis component of the fundamental voltage.

2. The control method of the parallel APF according to claim 1, characterized in that: The total voltage control and the voltage sharing control are performed based on the positive bus voltage and the negative bus voltage to obtain the target value of the D-axis component and the target value of the zero-axis component of the fundamental voltage, including: Calculating the sum of the positive bus voltage and the negative bus voltage, and performing PI calculation based on the error between the target value and the real-time value of the sum to obtain the target value of the D-axis component of the fundamental voltage; The difference between the positive bus voltage and the negative bus voltage is calculated, and a PI calculation is performed based on the error between the target value and the real-time value of the difference to obtain a target value of the zero-axis component of the fundamental voltage.

3. The control method of parallel APF according to claim 1, characterized in that: The transfer function of the CVPI controller is: Among them, W c '(s) is the function value of the transfer function of the CVPI controller, k cp is the proportional gain coefficient of the CVPI controller, k ci is the integral gain coefficient of the CVPI controller, ω0 is the angular frequency of the fundamental voltage, L i is the equivalent inductance between the parallel APF and the grid, L g is the equivalent inductance of the power supply side of the grid, is the sum of the equivalent inductance of the power supply side of the grid and the equivalent inductance between the parallel APF and the grid, r is the equivalent resistance between the parallel APF and the grid, s is the input quantity of the transfer function of the CVPI controller, and j is an imaginary unit.

4. The control method of parallel APF according to claim 1, characterized in that: The harmonic analysis is performed based on the real-time current on the load side and the AC side of the parallel APF to obtain the harmonic voltage, including: Determine the D-axis component of the harmonic voltage based on the D-axis component of the real-time current on the load side, the D-axis component of the real-time current on the AC side of the parallel APF, and a multi-harmonic controller; Determine the Q-axis component of the harmonic voltage based on the Q-axis component of the real-time current on the load side, the Q-axis component of the real-time current on the AC side of the parallel APF, and the multi-harmonic controller; Determine the zero-axis component of the harmonic voltage based on the zero-axis component of the real-time current on the load side, the zero-axis component of the real-time current on the AC side of the parallel APF, and the multi-harmonic controller; The harmonic voltage is determined based on a D-axis component, a Q-axis component, and a zero-axis component of the harmonic voltage.

5. The control method of the parallel APF according to claim 4, characterized in that: The transfer function of the multi-harmonic controller is: Among them, G R1 (s) is the function value of the transfer function of the multi-harmonic controller, h is the harmonic order, k is hr is the gain of the multi-harmonic controller at the hth harmonic frequency, ω c is the open-loop cut-off frequency of the multi-harmonic controller, T s is the period of the fundamental voltage, ω0 is the angular frequency of the fundamental voltage, and s is the input quantity of the transfer function of the multi-harmonic controller.

6. A control device for parallel APF, characterized in that: include: A communication module, used to obtain the real-time current of the load side of the power grid and the AC side of the parallel APF, as well as the positive bus voltage and negative bus voltage of the DC side of the parallel APF; A processing module, configured to perform PI calculation based on the positive bus voltage and the negative bus voltage, and the real-time current on the AC side of the parallel APF to obtain a fundamental voltage, wherein the fundamental voltage has the same phase as the voltage on the power supply side of the power grid; The processing module is further used to perform harmonic analysis based on the real-time current of the load side and the AC side of the parallel APF to obtain a harmonic voltage, and the harmonic voltage is used to characterize the harmonic situation of the load side; The processing module is further used to determine the target voltage of the AC side of the parallel APF based on the fundamental voltage and the harmonic voltage, and determine the duty cycle of each switch in the parallel APF based on the target voltage, so as to adjust the real-time voltage of the AC side of the parallel APF to the target voltage; The processing module is also used to perform DQ conversion on the real-time current on the load side of the power grid and the AC side of the parallel APF, respectively, to obtain the D-axis component, Q-axis component and zero-axis component of the real-time current on the load side of the power grid, and the D-axis component, Q-axis component and zero-axis component of the real-time current on the AC side of the parallel APF; The processing module is specifically used to perform total voltage control and voltage sharing control based on the positive bus voltage and the negative bus voltage to obtain a target value of a D-axis component and a target value of a zero-axis component of the fundamental voltage; Based on the error between the target value of the D-axis component of the fundamental voltage and the D-axis component of the real-time current on the AC side of the parallel APF, and the CVPI controller, a PI calculation is performed to obtain the D-axis component of the fundamental voltage; Based on the error between zero and the Q-axis component of the real-time current on the AC side of the parallel APF, and the CVPI controller, a PI calculation is performed to obtain the Q-axis component of the fundamental voltage; Based on the error between the target value of the zero-axis component of the fundamental voltage and the zero-axis component of the real-time current on the AC side of the parallel APF, and the CVPI controller, a PI calculation is performed to obtain the zero-axis component of the fundamental voltage; The fundamental wave voltage is determined based on a D-axis component, a Q-axis component, and a zero-axis component of the fundamental wave voltage.

7. An electronic device, characterized in that: The electronic device comprises a memory and a processor, wherein the memory stores a computer program, and the processor is configured to call and run the computer program stored in the memory to execute the method according to any one of claims 1 to 5.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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