Control Method, Device and Storage Medium of Active Power Filter

Abstract

The present application provides a control method for an active power filter, which is applied to an active power filter system and includes: performing fundamental wave difference processing on the acquired A-phase load current, B-phase load current, C-phase load current and voltage outer loop control quantity to obtain the A-phase command current and C-phase command current of a three-phase bridge inverter; performing linear prediction processing on the A-phase command current and C-phase command current to obtain the A-phase command current and C-phase command current at the next moment; inputting the acquired first line voltage, second line voltage, first output current, second output current, first capacitor voltage, second capacitor voltage, and the obtained A-phase command current and C-phase command current at the next moment into a preset active power filter model to obtain a first line voltage modulation signal and a second line voltage modulation signal, and obtaining a PWM pulse signal through modulation processing. Adjust the two line voltages of the inverter to make the compensation current follow the specified current and achieve harmonic compensation.

Description

Technical Field

[0001] The present invention relates to the technical field of power grids, and particularly relates to a control method, device and storage medium for an active power filter. Background Art

[0002] With the development of industry, the application of non-linear loads and equipment is becoming increasingly widespread, resulting in the decline of power grid power quality. Among them, the problem of power grid harmonic pollution is particularly serious. The harmonic pollution in the power grid will cause the following impacts: harmonics interfere with the normal operation of relay protection, causing misoperation of protection devices and affecting the stable operation of the system; harmonic currents increase the copper loss and iron loss of transformers, causing the temperature to rise and leading to the burning of transformers, and at the same time causing serious harmonic noise; harmonics increase the losses of motors and reduce the mechanical efficiency; harmonics cause overcurrent and overvoltage in reactive power compensation capacitors, reducing the capacitor life; the induced electromagnetic fields generated by harmonics affect communication equipment and reduce the communication quality, etc.

[0003] Currently, active power filters are usually used to filter out the harmonic components in the power grid, and the commonly used control methods for active power filters are triangular carrier control and hysteresis current control. Among them, the working principle of the triangular carrier control method is relatively simple and easy to implement, but the dynamic response speed is generally average and the real-time performance is poor. Its frequency may always be in a high-frequency state, resulting in large losses of switching devices. In addition, a high-pass filter needs to be additionally added when dealing with harmonic components. The hysteresis current control method belongs to closed-loop control, and its real-time performance and dynamic response speed are better than those of triangular carrier control. However, when the size of the hysteresis width parameter is fixed, the switching frequency of the circuit will change with the fluctuation of the compensation circuit. The frequency may always be in a high-frequency state, resulting in large losses and short life of switching devices; the frequency may also always be in a low-frequency state, resulting in poor accuracy and large errors. That is to say, the commonly used inner-loop current control methods in active power filters at present have problems such as poor real-time performance, slow dynamic response speed, low modulation degree of pulse drive signals, and low voltage utilization rate. Summary of the Invention

[0004] Based on this, the present invention provides a control method, device and storage medium for an active power filter, which has a fast dynamic response speed, good real-time performance, improves the modulation degree of pulse drive signals, and improves the voltage utilization rate.

[0005] In a first aspect, the present invention provides a control method for an active power filter. The control method for the active power filter is applied to an active power filter system, which includes a three-phase bridge inverter circuit, an asymmetric filter circuit, and a nonlinear load circuit. The asymmetric filter circuit includes a first filter circuit and a second filter circuit. The three-phase bridge inverter circuit includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and a DC-side capacitor connected in parallel. The input end of the nonlinear load circuit is connected to the output end of a three-phase power grid. One end of the first filter circuit is connected to the A-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the A-phase bridge arm. One end of the second filter circuit is connected to the C-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the C-phase bridge arm. The midpoint between the upper and lower bridge arms of the B-phase bridge arm is connected to the B-phase output end of the three-phase power grid. The method includes:

[0006] Obtain the A-phase load current, B-phase load current, and C-phase load current at the input end of the nonlinear load circuit at the current moment, the voltage outer-loop control quantity of the DC-side capacitor, the first line voltage between A and B and the second line voltage between C and B at the output end of the three-phase power grid, as well as the first output current of the first filter circuit, the first capacitor voltage of the first filter circuit, the second output current of the second filter circuit, and the second capacitor voltage of the second filter circuit;

[0007] Perform fundamental wave difference processing on the A-phase load current, B-phase load current, C-phase load current, and the voltage outer-loop control quantity to obtain the A-phase command current and C-phase command current of the three-phase bridge inverter;

[0008] Perform linear prediction processing on the A-phase command current and C-phase command current to obtain the A-phase command current and C-phase command current at the next moment;

[0009] Input the first line voltage, the second line voltage, the first output current, the second output current, the first capacitor voltage, the second capacitor voltage, the A-phase command current at the next moment, and the C-phase command current at the next moment into a preset first active power filter model to obtain the first line voltage modulation signal between A and B and the second line voltage modulation signal between C and B of the three-phase bridge inverter circuit;

[0010] Perform modulation processing on the first line voltage modulation signal and the second line voltage modulation signal to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate the harmonics of the three-phase power grid.

[0011] Second aspect, the present invention also provides another control method for an active power filter. The control method for the active power filter is applied to an active power filter system. The active power filter system includes a three-phase bridge inverter circuit, an asymmetric filter circuit, and a nonlinear load circuit. The asymmetric filter circuit includes a third filter circuit and a fourth filter circuit. The three-phase bridge inverter circuit includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and a DC-side capacitor connected in parallel. The input end of the nonlinear load circuit is connected to the output end of the three-phase power grid. One end of the third filter circuit is connected to the A-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the A-phase bridge arm. One end of the fourth filter circuit is connected to the C-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the C-phase bridge arm. The midpoint between the upper and lower bridge arms of the B-phase bridge arm is connected to the B-phase output end of the three-phase power grid. The method includes:

[0012] Obtain the A-phase load current, B-phase load current, and C-phase load current at the input end of the nonlinear load circuit at the current moment, the voltage outer-loop control quantity of the DC-side capacitor, the first line voltage between A and B and the second line voltage between C and B at the output end of the three-phase power grid, as well as the third output current of the third filter circuit and the fourth output current of the fourth filter circuit;

[0013] Perform fundamental wave difference processing on the A-phase load current, B-phase load current, C-phase load current, and the voltage outer-loop control quantity to obtain the A-phase command current and C-phase command current of the three-phase bridge inverter;

[0014] Perform linear prediction processing on the A-phase command current and C-phase command current to obtain the A-phase command current and C-phase command current at the next moment;

[0015] Input the first line voltage, the second line voltage, the third output current, the fourth output current, the A-phase command current at the next moment, and the C-phase command current at the next moment into a preset second active power filter model to obtain the third line voltage modulation signal between A and B and the fourth line voltage modulation signal between C and B of the three-phase bridge inverter circuit;

[0016] Perform modulation processing on the third line voltage modulation signal and the fourth line voltage modulation signal to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate the harmonics of the three-phase power grid.

[0017] The beneficial effects of adopting the above technical solution are as follows: For the control method of the active power filter in this application, by adjusting the voltages of two phases of the three-phase bridge inverter circuit, the current on the DC side can fully follow the given specified current, achieving harmonic compensation; with the reduction of the number of filter circuits, it can achieve the effects of fast dynamic response speed and good real-time performance for harmonic compensation, and improve the utilization rate of voltage, increasing the modulation degree of the pulse drive signal. Brief Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art.

[0019] Figure 1 Schematic diagram of the active filtering system provided by an embodiment of this application;

[0020] Figure 2 Schematic diagram of the control method of the active power filter provided by an embodiment of this application;

[0021] Figure 3 Schematic diagram of the grid current when the control method of the active power filter provided by an embodiment of this application is applied to the active filtering system;

[0022] Figure 4 Schematic diagram of the DC-side capacitor voltage when the control method of the active power filter provided by an embodiment of this application is applied to the active filtering system;

[0023] Figure 5 Schematic diagram of the Fourier analysis of the grid current when the control method of the active power filter provided by an embodiment of this application is applied to the active filtering system;

[0024] Figure 6 Schematic diagram of the control device of the active power filter provided by an embodiment of this application;

[0025] Figure 7 Schematic diagram of the active filtering system provided by another embodiment of this application;

[0026] Figure 8 Schematic diagram of the control method of the active power filter provided by another embodiment of this application;

[0027] Figure 9 Schematic diagram of the grid current when the control method of the active power filter provided by another embodiment of this application is applied to the active filtering system;

[0028] Figure 10 Schematic diagram of the DC-side capacitor voltage when the control method of the active power filter provided by another embodiment of this application is applied to the active filtering system;

[0029] Figure 11 Schematic diagram of Fourier analysis of grid current of the active power filter provided for another embodiment of the present application applied in an active filtering system;

[0030] Figure 12 Schematic diagram of the control device of the active power filter provided for another embodiment of the present application. Specific embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. To describe the present invention in more detail, a control method, a control device, and a system of an active power filter provided by the present invention will be specifically described below in conjunction with the accompanying drawings.

[0032] Harmonic pollution in the power grid will affect the normal operation of the power grid, including: harmonics interfering with the normal operation of relay protection, causing the protection device to malfunction and affecting the stable operation of the system; harmonic current increasing the copper loss and iron loss of the transformer, causing the temperature to rise and leading to the burning of the transformer, and at the same time causing serious harmonic noise; harmonics increasing the loss of the motor and reducing the mechanical efficiency; harmonics causing overcurrent and overvoltage in the reactive power compensation capacitor, reducing the capacitor life; the induced electromagnetic field generated by harmonics affecting communication equipment and reducing the communication quality, etc.

[0033] In a first aspect, refer to the attached Figure 1 , the attached Figure 1 shows a schematic diagram of the application scenario of the control method of the active power filter provided by the embodiments of the present invention. This application scenario includes an active power filter system, including a three-phase bridge inverter circuit 202, an asymmetric filter circuit 201, and a nonlinear load circuit 102. The asymmetric filter circuit 201 includes a first filter circuit and a second filter circuit. The three-phase bridge inverter circuit 202 includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and a DC-side capacitor connected in parallel. The input end of the nonlinear load circuit 102 is connected to the output end of the three-phase power grid 101. One end of the first filter circuit is connected to the A-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the A-phase bridge arm; one end of the second filter circuit is connected to the C-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the C-phase bridge arm; the midpoint between the upper and lower bridge arms of the B-phase bridge arm is connected to the B-phase output end of the three-phase power grid.

[0034] Based on this, the control method of the active power filter provided by the embodiments of the present invention, as shown in the attached Figure 2 , shown in the attached Figure 2The figure shows a schematic diagram of the control method of the active power filter provided by an embodiment of the present invention. This method takes the active power filter system in the appendix Figure 1 as the application environment and includes the following steps:

[0035] Step S1001: Obtain the phase A load current i la1 at the input end of the nonlinear load circuit 102 at the current moment, the phase B load current i lb1 and the phase C load current i lc1 , the voltage outer loop control quantity Δi q of the DC side capacitor, the first line voltage e ab1 between phases A and B at the output end of the three-phase power grid, and the second line voltage e cb1 between phases C and B, as well as the first output current i ca1 of the first filter circuit, the first capacitor voltage u ca of the first filter circuit, the second output current i cc1 of the second filter circuit, and the second capacitor voltage u cc of the second filter circuit.

[0036] Step S1002: Perform fundamental wave difference processing on the phase A load current i la1 , the phase B load current i lb1 , the phase C load current i lc1 and the voltage outer loop control quantity Δi q to obtain the phase A command current i ca1 (k) and the phase C command current i cc1 (k) of the three-phase bridge inverter.

[0037] Specifically, the above step S1002 includes the following specific steps:

[0038] Step S2001: Perform abc-dq coordinate transformation processing on the phase A load current i la , the phase B load current i lb1 and the phase C load current i lc to obtain the active component i ld and the reactive component i lq of the three-phase load current.

[0039] Among them, the specific expression of the abc-dq coordinate transformation processing is:

[0040]

[0041] C abc / dq is the abc-dq coordinate transformation matrix.

[0042] Step S2002: For the active component i ld1 and the reactive component ilq1 Perform filtering processing to obtain the active DC component of the three-phase load current and the reactive DC component

[0043] Specifically, the filtering processing filters out the AC component through a low-pass filter.

[0044] Step S2003: Add the reactive DC component of the three-phase load current to the voltage outer-loop control quantity Δi q to obtain the q-axis fundamental component Obtain the d-axis fundamental component according to the active DC component of the three-phase load current

[0045] Since the filter circuit in this embodiment is an LC series connection, and the LC filter is capacitive to the fundamental wave, resulting in the current of this branch leading the grid-side voltage by 90° in phase, and it is impossible to generate active power to control the DC side. Therefore, the control quantity needs to be added to the q-axis component to generate a current with the same phase, generate active power, and then control the DC side. In addition, the acquisition process of the voltage outer-loop control quantity Δi q is as follows:

[0046] Step S3001: Obtain the difference ΔU of the capacitor voltage according to the actual capacitor voltage U of the DC side obtained dc and the command capacitor voltage That is, obtain the difference between the actual measured value and the ideal value of the DC-side capacitor voltage; dc1

[0047] Step S3002: Input the difference ΔU of the capacitor voltage dc1 into a PI controller to obtain the voltage outer-loop control quantity Δi q , where the PI controller is specifically K p is the proportional coefficient, and K i is the integral coefficient.

[0048] Step S2004: Perform dq-abc coordinate transformation processing on the q-axis fundamental component and the d-axis fundamental component to obtain the A-phase load fundamental component i fa1 and the C-phase load fundamental component i fc .

[0049] Among them, the specific expression of the dq-abc coordinate transformation processing is:

[0050]

[0051] C dq / abcIs the dq-abc coordinate transformation matrix

[0052] Step S2005: Respectively subtract the fundamental component i fa1 of the A-phase load and the fundamental component i fc1 of the C-phase load from the A-phase load current i la1 and the C-phase load current i lb to obtain the command current i ca (k) of the A-phase of the three-phase bridge inverter circuit and the command current i cc1 (k) of the C-phase.

[0053] Step S1003: Perform linear prediction processing on the command current i ca1 (k) of the A-phase and the command current i cc1 (k) of the C-phase to obtain the command current i ca1 (k + 1) of the A-phase at the next moment and the command current i cc1 (k + 1) of the C-phase.

[0054] Specifically, the specific expression of the linear prediction processing is:

[0055]

[0056] Step S1004: Input the first line voltage e ab , the second line voltage e cb , the first output current i ca , the second output current i cc , the first capacitor voltage u ca , the second capacitor voltage u cc , the command current i ca (k + 1) of the A-phase at the next moment and the command current i cc (k + 1) of the C-phase at the next moment into a preset first active power filter model to obtain the first line voltage modulation signal U fab1 (k) between the A and B phases of the three-phase bridge inverter circuit and the second line voltage modulation signal U fcb1 (k) between the C and B phases.

[0057] Among them, the first active power filter model is specifically:

[0058]

[0059] Among them, U fab1 (k) is the first line voltage modulation signal between the A and B phases of the three-phase bridge inverter circuit, U fcb1 (k) is the second line voltage modulation signal between the C and B phases of the three-phase bridge inverter circuit, T is the sampling period, L is the inductance value of the filter circuit, R is the resistance value of the asymmetric filter circuit, i ca(k + 1) is the command current of phase A of the three-phase bridge inverter circuit at time k + 1, i ca (k) is the command current of phase A of the three-phase bridge inverter circuit at time k, i cc (k + 1) is the command current of phase C of the three-phase bridge inverter circuit at time k + 1, i cc1 (k) is the command current of phase C of the three-phase bridge inverter circuit at time k, u Ca (k) is the voltage of the first capacitor at time k, u cc (k) is the voltage of the second capacitor at time k, e ab1 (k) is the first line voltage at time k, e cb1 (k) is the second line voltage at time k.

[0060] Step S1005: Modulate the output signal U fab1 (k) of phase A and the output signal U fcb1 (k) of phase C to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate the harmonics of the three-phase power grid.

[0061] The control method of the above active power filter adjusts the two-phase voltages output by the three-phase bridge inverter circuit, and the current output by the filter circuit completely tracks the given specified current, realizing harmonic compensation, achieving the effects of fast dynamic response speed of harmonic compensation, good real-time performance, and improving the utilization rate of voltage.

[0062] To better illustrate the control method of the above active power filter, specific simulation results are provided for the above method to verify the effectiveness of harmonic filtering.

[0063] According to the specific parameters of the active power filter system shown in the following table for simulation, the simulation results as shown in the appendix Figure 3 - Appendix Figure 5 are obtained:

[0064]

[0065] As shown in the appendix Figure 3 When the control method of the active power filter is applied to the active harmonic filtering system, the current change of the three-phase power grid before and after the load suddenly changes by 30%. Before 2 s, the grid current presents a sine shape, and the three-phase currents are basically symmetrical; after 2 s, the load suddenly increases by 30%, and the grid current fluctuates; after 3 cycles of the system, it reaches a stable state again, and the shape of the three-phase currents is corrected from a saddle shape to a sine shape. It can be seen that in the case of only setting two filter circuits in the present invention, by controlling the output voltage of the three-phase bridge inverter circuit, the harmonics of the three-phase power grid current are filtered out, reducing the complexity of the filter circuit, and having good dynamic performance while providing good compensation performance.

[0066] As shown in the appendix Figure 4 The figure shows the changes in the three-phase grid currents before and after the control method of the active power filter is put into use. At 0.1 s, the control method of the active power filter is applied to the active power filter system. It can be seen that after using the control method of the active power filter, the DC-side voltage is adjusted from 550 V to the command voltage of 500 V, effectively reducing the DC-side bus voltage.

[0067] The appendix Figure 5 shows the FFT analysis of the grid current when the control method of the active power filter is applied to the active power filter system. The total distortion rate of the three-phase grid system drops from 25% to 3.26%, meeting the harmonic control standard and having good harmonic compensation ability.

[0068] It should be understood that although the steps in the flow chart in the appendix Figure 2 are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise clearly stated in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in the appendix Figure 2 may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential either, but can be executed alternately or in turn with at least a part of other steps or sub-stages or stages of other steps.

[0069] For the control method of the active power filter described in detail in the above embodiments disclosed by the present invention, various forms of devices can be used to implement the above methods disclosed by the present invention. Therefore, the present invention also discloses a control device for the active power filter corresponding to the above method, which is applied to the same active power filter system. Specific embodiments are given below for detailed description.

[0070] As shown in the appendix Figure 6 The embodiment of the present invention also provides a control device for the active power filter, including:

[0071] A first parameter acquisition module 4001, configured to acquire the phase-A load current, phase-B load current, and phase-C load current at the input end of the nonlinear load circuit at the current moment, the voltage outer-loop control quantity corresponding to the DC-side capacitor, the first line voltage between phases A and B and the second line voltage between phases C and B at the output end of the three-phase grid, and the first output current of the first filter circuit, the first capacitor voltage of the first filter circuit, the second output current of the second filter circuit, and the second capacitor voltage of the second filter circuit;

[0072] The first instruction current calculation module 4002 is configured to perform fundamental wave difference processing on the A-phase load current, B-phase load current, C-phase load current, and the voltage outer loop control quantity to obtain the A-phase instruction current and C-phase instruction current of the three-phase bridge inverter;

[0073] The first instruction current prediction module 4003 is configured to perform linear prediction processing on the A-phase instruction current and C-phase instruction current to obtain the A-phase instruction current and C-phase instruction current at the next moment;

[0074] The first output signal calculation module 4004 is configured to input the first line voltage, the second line voltage, the first output current, the second output current, the first capacitor voltage, the second capacitor voltage, the A-phase instruction current at the next moment, and the C-phase instruction current at the next moment into a preset first active power filter model to obtain the first line voltage modulation signal between phases A and B and the second line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit;

[0075] The first pulse signal generation module 4005 is configured to perform modulation processing on the first line voltage modulation signal and the second line voltage modulation signal to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate the harmonics of the three-phase power grid.

[0076] In a second aspect, refer to the attached Figure 7 , the attached Figure 7 shows a schematic diagram of an application scenario of the control method of the active power filter provided by the embodiment of the present invention. This application scenario includes an active power filter system, which includes a three-phase bridge inverter circuit 402, an asymmetric filter circuit 401, and a nonlinear load circuit 302. The asymmetric filter circuit 401 includes a third filter circuit and a fourth filter circuit. The three-phase bridge inverter circuit 402 includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and a DC-side capacitor connected in parallel. The input end of the nonlinear load circuit 302 is connected to the output end of the three-phase power grid 301. One end of the third filter circuit is connected to the A-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the A-phase bridge arm; One end of the fourth filter circuit is connected to the C-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the C-phase bridge arm; The midpoint between the upper and lower bridge arms of the B-phase bridge arm is connected to the B-phase output end of the three-phase power grid.

[0077] Based on this, the control method of the active power filter provided by the embodiment of the present invention, as shown in the attached Figure 8 shown, the attached Figure 8 shows a schematic diagram of the control method of the active power filter provided by the embodiment of the present invention. This method takes the active power filter system in the attached Figure 7 as the application environment and includes the following steps:

[0078] Step S5001: Obtain the phase-A load current \(i\) at the input end of the non-linear load circuit 302 at the current moment la2 , phase-B load current \(i\) lb2 and phase-C load current \(i\) lc2 , the voltage outer-loop control quantity \(\Delta i\) of the DC-side capacitor d , the first line voltage \(e\) between phases A and B at the output end of the three-phase power grid ab2 and the second line voltage \(e\) between phases C and B cb2 , and the third output current of the third filter circuit \(i\) ca2 and the fourth output current \(i\) of the fourth filter circuit cc2 ;

[0079] Step S5002: Perform fundamental wave difference processing on the phase-A load current \(i\) la2 , phase-B load current \(i\) 1b2 , phase-C load current \(i\) lc2 and the voltage outer-loop control quantity \(\Delta i\) d to obtain the phase-A command current \(i\) ca2 (k) and phase-C command current \(i\) cc (k);

[0080] Specifically, the above Step S5002 includes the following specific steps:

[0081] Step S6001: Perform abc-dq coordinate transformation processing on the phase-A load current \(i\) la2 , phase-B load current \(i\) lb2 and phase-C load current \(i\) lc2 to obtain the active component \(i\) ld2 and reactive component \(i\) lq of the three-phase load current.

[0082] Among them, the specific expression of the abc-dq coordinate transformation processing is:

[0083]

[0084] C abc / dq is the abc-dq coordinate transformation matrix.

[0085] Step S6002: Perform filtering processing on the active component \(i\) ld2 and reactive component \(i\) lq of the three-phase load current to obtain the active DC component and reactive DC component

[0086] Specifically, the filtering processing filters out the AC components through a low-pass filter.

[0087] Step S6003: The active DC component of the three-phase load current is superimposed with the outer-loop DC voltage control quantity Δi d to obtain the fundamental d-axis component According to the reactive DC component of the three-phase load current the fundamental q-axis component is obtained

[0088] Since the filter circuit in this embodiment only has an inductor, the d-axis component needs to be adjusted, while the fundamental q-axis component does not need to be adjusted. In addition, the specific acquisition process of the outer-loop voltage control quantity Δi d is as follows:

[0089] Step S7001: According to the actually measured capacitor voltage U of the DC side obtained dc2 and the commanded capacitor voltage the voltage difference ΔU of the capacitor is obtained dc2 , that is, the difference between the actually measured value and the ideal value of the DC-side capacitor voltage is obtained;

[0090] Step S7002: The voltage difference ΔU of the capacitor dc2 is input into a PI controller to obtain the outer-loop voltage control quantity Δi d , where the PI controller is specifically K p is the proportional coefficient, and K i is the integral coefficient.

[0091] Step S6004: The fundamental q-axis component and the fundamental d-axis component are processed through a dq-abc coordinate transformation to obtain the fundamental A-phase load component i fa2 and the fundamental C-phase load component i fc .

[0092] Among them, the specific expression of the dq-abc coordinate transformation is:

[0093]

[0094] C dq / abc is the dq-abc coordinate transformation matrix

[0095] Step S6005: The fundamental A-phase load component i fa2 and the fundamental C-phase component i fc2 are respectively subtracted from the A-phase load current i la and the C-phase load current i lb2 to obtain the A-phase commanded current i ca2 (k) and the C-phase commanded current i cc2 (k) of the three-phase bridge inverter circuit.

[0096] Step S5003: Perform linear prediction processing on the phase A command current i ca2 (k) and the phase C command current i cc2 (k) to obtain the phase A command current i ca (k + 1) and the phase C command current i cc2 (k + 1).

[0097] Specifically, the specific expression of the linear prediction processing is:

[0098]

[0099] Step S5004: Input the first line voltage e ab2 , the second line voltage e cb2 , the third output current i ca2 , the fourth output current i cc2 , the phase A command current i ca2 (k + 1) and the phase C command current i cc2 (k + 1) at the next moment into the preset second active power filter model to obtain the third line voltage modulation signal U fab2 (k) between phases A and B and the fourth line voltage modulation signal U fcb2 (k) between phases C and B of the three-phase bridge inverter circuit.

[0100] Among them, the second active power filter system is specifically:

[0101]

[0102] Among them, U fab2 (k) is the third line voltage modulation signal between phases A and B of the three-phase bridge inverter circuit, U fcb2 (k) is the fourth line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit, T is the sampling period, L is the inductance value of the filter circuit, r is the internal resistance value of the asymmetric filter circuit, i ca2 (k + 1) is the phase A command current of the three-phase bridge inverter circuit at the (k + 1)th moment, i ca2 (k) is the phase A command current of the three-phase bridge inverter circuit at the kth moment, i cc2 (k + 1) is the phase C command current of the three-phase bridge inverter circuit at the (k + 1)th moment, i cc2 (k) is the phase C command current of the three-phase bridge inverter circuit at the kth moment, e ab2 (k) is the first line voltage at the kth moment, e cb2 (k) is the second line voltage at the kth moment.

[0103] Step S5005: Modulate the third line voltage modulation signal U fab2 (k) and the fourth line voltage modulation signal U fcb2 (k) to obtain a PWM pulse signal, which is used to eliminate the harmonics of the three-phase power grid.

[0104] For the above control method of the active power filter, by adjusting the two-phase voltages output by the three-phase bridge inverter circuit, the current output by the filter circuit completely tracks the given specified current, realizing harmonic compensation, and achieving the effects of fast dynamic response speed of harmonic compensation, good real-time performance, and improved voltage utilization rate.

[0105] To better illustrate the above control method of the active power filter, specific simulation results are provided for the above method to verify the effectiveness of harmonic filtering.

[0106] Perform simulation according to the specific parameters of the active power filter system shown in the following table, and obtain the simulation results as shown in the appendix Figure 9 - Appendix Figure 11 as follows:

[0107]

[0108] As shown in the appendix Figure 9 When the control method of the active power filter is applied to the active harmonic filter system. At 0.1 s, the control method of the active power filter is applied. It can be seen that after using the control method of the active power filter, after three cycles, the grid current reaches stability, and the shape of the three-phase current is corrected from the saddle shape to the sine shape. In the case where only two filter circuits are set in the present invention, by controlling the output voltage of the three-phase bridge inverter circuit, the harmonics of the three-phase grid current are filtered out, reducing the complexity of the filter circuit.

[0109] Appendix Figure 10 shows that after the control method of the active power filter is applied to the active power filter system, the DC side bus voltage can be stabilized at the specified value of 700 V, providing a stable DC voltage for the three-phase bridge inverter circuit. In the case of only setting two filter circuits, the voltage and current ratings of the power devices are not increased.

[0110] Appendix Figure 11 shows the FFT analysis of the grid current of the active power filter system when the control method of the active power filter is applied. The harmonics generated by the non-linear load circuit are suppressed to less than 0.4%, and the total distortion rate of the system drops to 1.35%, having excellent harmonic compensation ability.

[0111] It should be understood that although the appendix Figure 8In the flowchart, the steps are shown in sequence according to the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in the appendix Figure 8 may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or sub-stages or stages of other steps.

[0112] For the control method of the active power filter described in detail in the above embodiments of the present invention, various forms of devices can be used to implement the above method of the present invention. Therefore, the present invention also discloses a control device for an active power filter corresponding to the above method, which is applied to the same active power filter system. Specific embodiments are given below for detailed description.

[0113] As shown in the appendix Figure 12 , the embodiment of the present invention also provides a control device for an active power filter, including:

[0114] A second parameter acquisition module 8001, configured to acquire the phase A load current, phase B load current, and phase C load current at the input end of the nonlinear load circuit at the current moment, the voltage outer loop control quantity corresponding to the DC side capacitor, the first line voltage between phases A and B and the second line voltage between phases C and B at the output end of the three-phase power grid, and the third output current of the third filter circuit and the fourth output current of the fourth filter circuit;

[0115] A second command current calculation module 8002, configured to perform fundamental wave difference processing on the phase A load current, phase B load current, phase C load current, and the voltage outer loop control quantity to obtain the phase A command current and phase C command current of the three-phase bridge inverter;

[0116] A second command current prediction module 8003, configured to perform linear prediction processing on the phase A command current and phase C command current to obtain the phase A command current and phase C command current at the next moment;

[0117] A second output signal calculation module 8004, configured to input the first line voltage, the second line voltage, the third output current, the fourth output current, the phase A command current at the next moment, and the phase C command current at the next moment into a preset second active power filter model to obtain the third line voltage modulation signal between phases A and B and the fourth line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit;

[0118] The second pulse signal generation module 8005 is configured to perform modulation processing on the third line voltage modulation signal and the fourth line voltage modulation signal to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate harmonics of a three-phase power grid.

[0119] In a third aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the control method of the active power filter in the first aspect or the second aspect are implemented.

[0120] The computer-readable storage medium may be an electronic memory such as a flash memory, an EEPROM (electrically erasable programmable read-only memory), an EPROM (erasable programmable read-only memory), a hard disk, or a ROM. Optionally, the computer-readable storage medium includes a non-transitory computer-readable storage medium. The computer-readable storage medium has a storage space for program codes for executing any method steps in the above methods. These program codes can be read from or written into one or more computer program products, and the program codes can be compressed in a suitable form.

[0121] In a fourth aspect, the present invention further provides a computer device, including a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the control method of the active power filter in the first aspect or the second aspect is executed.

[0122] The computer device includes a memory, a processor, and one or more computer programs, where one or more computer programs can be stored in the memory and configured to be executed by one or more processors, and one or more application programs are configured to execute the control method of the active power filter described above.

[0123] The processor may include one or more processing cores. The processor utilizes various interfaces and circuits to connect various parts within the entire computer device. By running or executing instructions, programs, code sets, or instruction sets stored in the memory, and by invoking data stored in the memory, it performs various functions of the computer device and processes data. Optionally, the processor may be implemented in at least one hardware form of digital signal processing (DSP), field-programmable gate array (FPGA), or programmable logic array (PLA). The processor may integrate one or a combination of several of a central processing unit (CPU), a reporting validator for buried point data (Graphics Processing Unit, GPU), and a modem, etc. Among them, the CPU mainly processes the operating system, user interface, application programs, etc.; the GPU is responsible for rendering and drawing the displayed content; the modem is used to process wireless communications. It can be understood that the above-mentioned modem may not be integrated into the processor and may be implemented separately through a communication chip.

[0124] The memory may include random access memory (RAM) and may also include read-only memory. The memory can be used to store instructions, programs, code, code sets, or instruction sets. The memory may include a program storage area and a data storage area. Among them, the program storage area may store instructions for implementing the operating system, instructions for implementing at least one function (such as touch function, sound playback function, image playback function, etc.), instructions for implementing the above-mentioned various method embodiments, etc. The data storage area may also store data created during the use of the terminal device.

[0125] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A control method for an active power filter, the control method of the active power filter being applied to an active power filter system, the active power filter system including a three-phase bridge inverter circuit, an asymmetric filter circuit, and a nonlinear load circuit, wherein the asymmetric filter circuit includes a first filter circuit and a second filter circuit, the three-phase bridge inverter circuit includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and a DC-side capacitor connected in parallel, the input end of the nonlinear load circuit is connected to the output end of a three-phase power grid, one end of the first filter circuit is connected to the A-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the A-phase bridge arm; one end of the second filter circuit is connected to the C-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the C-phase bridge arm; the midpoint between the upper and lower bridge arms of the B-phase bridge arm is connected to the B-phase output end of the three-phase power grid, characterized in that, The method includes: Obtaining the phase-A load current, phase-B load current, and phase-C load current at the input end of the non-linear load circuit at the current moment, the voltage outer-loop control quantity of the DC-side capacitor, the first line voltage between phases A and B and the second line voltage between phases C and B at the output end of the three-phase power grid, as well as the first output current of the first filter circuit, the first capacitor voltage of the first filter circuit, the second output current of the second filter circuit, and the second capacitor voltage of the second filter circuit; Performing fundamental wave difference processing on the phase-A load current, phase-B load current, phase-C load current, and the voltage outer-loop control quantity to obtain the phase-A command current and phase-C command current of the three-phase bridge inverter; Performing linear prediction processing on the phase-A command current and phase-C command current to obtain the phase-A command current and phase-C command current at the next moment; Inputting the first line voltage, the second line voltage, the first output current, the second output current, the first capacitor voltage, the second capacitor voltage, the phase-A command current at the next moment, and the phase-C command current at the next moment into a preset first active power filter model to obtain the first line voltage modulation signal between phases A and B and the second line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit; Performing modulation processing on the first line voltage modulation signal and the second line voltage modulation signal to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate the harmonics of the three-phase power grid.

2. The control method of the active power filter according to claim 1, characterized in that, The specific expression of the first active power filter model is: Among them, U fab1 (k) is the first line voltage modulation signal between phases A and B of the three-phase bridge inverter circuit, U fcb1 (k) is the second line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit, T is the sampling period, L is the inductance value of the filter circuit, R is the resistance value of the asymmetric filter circuit, i ca1 (k + 1) is the command current of phase A of the three-phase bridge inverter circuit at the (k + 1)-th moment, i ca1 (k) is the command current of phase A of the three-phase bridge inverter circuit at the k-th moment, i cc1 (k + 1) is the command current of phase C of the three-phase bridge inverter circuit at the (k + 1)-th moment, i cc1 (k) is the command current of phase C of the three-phase bridge inverter circuit at the k-th moment, u Ca (k) is the first capacitor voltage at the k-th moment, u Cc (k) is the second capacitor voltage at the k-th moment, e ab1 (k) is the first line voltage at the k-th moment, e cb1 (k) is the second line voltage at the k-th moment.

3. The control method of the active power filter according to claim 1, characterized in that The performing fundamental wave difference processing on the phase-A load current, phase-B load current, phase-C load current, and the voltage outer-loop control quantity to obtain the phase-A command current and phase-C command current of the three-phase bridge inverter is specifically: Performing abc-dq coordinate transformation processing on the phase-A load current, phase-B load current, and phase-C load current to obtain the active component and reactive component of the three-phase load current; Performing filtering processing on the active component and reactive component of the three-phase load current to obtain the active DC component and reactive DC component of the three-phase load current; Superposing the reactive DC component of the three-phase load current and the voltage outer-loop control quantity to obtain the q-axis fundamental wave component, and obtaining the d-axis fundamental wave component according to the active DC component of the three-phase load current; Performing dq-abc coordinate transformation processing on the q-axis fundamental wave component and the d-axis fundamental wave component to obtain the phase-A load fundamental wave component and phase-C load fundamental wave component; Respectively performing difference processing on the phase-A load fundamental wave component and phase-C fundamental wave component with the phase-A load current and phase-C load current to obtain the phase-A command current and phase-C command current of the three-phase bridge inverter circuit.

4. A control method for an active power filter, the control method for the active power filter being applied to an active power filter system, the active power filter system including a three-phase bridge inverter circuit, an asymmetric filter circuit, and a nonlinear load circuit, wherein the asymmetric filter circuit includes a third filter circuit and a fourth filter circuit, the three-phase bridge inverter circuit includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and a DC-side capacitor connected in parallel, the input end of the nonlinear load circuit is connected to the output end of a three-phase power grid, one end of the third filter circuit is connected to the A-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the A-phase bridge arm; one end of the fourth filter circuit is connected to the C-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the C-phase bridge arm; the midpoint between the upper and lower bridge arms of the B-phase bridge arm is connected to the B-phase output end of the three-phase power grid, characterized in that, The method includes: Obtaining the phase-A load current, phase-B load current, and phase-C load current at the input end of the non-linear load circuit at the current moment, the voltage outer-loop control quantity of the DC-side capacitor, the first line voltage between phases A and B and the second line voltage between phases C and B at the output end of the three-phase power grid, as well as the third output current of the third filter circuit and the fourth output current of the fourth filter circuit; Perform fundamental wave difference processing on the A-phase load current, B-phase load current, C-phase load current, and the voltage outer loop control quantity to obtain the A-phase command current and C-phase command current of the three-phase bridge inverter; Perform linear prediction processing on the A-phase command current and C-phase command current to obtain the A-phase command current and C-phase command current at the next moment; Input the first line voltage, the second line voltage, the third output current, the fourth output current, the A-phase command current at the next moment, and the C-phase command current at the next moment into a preset second active power filter model to obtain the third line voltage modulation signal between phases A and B and the fourth line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit; Perform modulation processing on the third line voltage modulation signal and the fourth line voltage modulation signal to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate the harmonics of the three-phase power grid.

5. The control method of the active power filter according to claim 4, characterized in that The second active power filter model is specifically: Among them, U fab2 (k) is the third line voltage modulation signal between phases A and B of the three-phase bridge inverter circuit, U fcb2 (k) is the fourth line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit, T is the sampling period, L is the inductance value of the filter circuit, r is the internal resistance value of the asymmetric filter circuit, i ca2 (k + 1) is the command current of phase A of the three-phase bridge inverter circuit at the (k + 1)-th moment, i ca2 (k) is the command current of phase A of the three-phase bridge inverter circuit at the k-th moment, i cc2 (k + 1) is the command current of phase C of the three-phase bridge inverter circuit at the (k + 1)-th moment, i cc2 (k) is the command current of phase C of the three-phase bridge inverter circuit at the k-th moment, e ab2 (k) is the first line voltage at the k-th moment, e cb2 (k) is the second line voltage at the k-th moment.

6. The control method of the active power filter according to claim 4, characterized in that The performing fundamental wave difference processing on the A-phase load current, B-phase load current, C-phase load current, and the voltage outer loop control quantity to obtain the A-phase command current and C-phase command current of the three-phase bridge inverter is specifically: Perform abc-dq coordinate transformation processing on the A-phase load current, B-phase load current, and C-phase load current to obtain the active component and reactive component of the three-phase load current; Perform filtering processing on the active component and reactive component of the three-phase load current to obtain the active DC component and reactive DC component of the three-phase load current; Superimpose the active DC component of the three-phase load current with the voltage outer loop control quantity of the DC side to obtain the d-axis fundamental wave component, and obtain the q-axis fundamental wave component according to the reactive DC component of the three-phase load current; Perform dq-abc coordinate transformation processing on the q-axis fundamental wave component and the d-axis fundamental wave component to obtain the A-phase load fundamental wave component and the C-phase load fundamental wave component; Perform subtraction processing on the A-phase load fundamental wave component and the C-phase fundamental wave component with the A-phase load current and the C-phase load current respectively to obtain the A-phase command current and C-phase command current of the three-phase bridge inverter circuit.

7. A control device for an active power filter, the control device for the active power filter being applied to an active power filter system, the active power filter system including a three-phase bridge inverter circuit, an asymmetric filter circuit, and a nonlinear load circuit, wherein the asymmetric filter circuit includes a first filter circuit and a second filter circuit, the three-phase bridge inverter circuit includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and a DC-side capacitor connected in parallel, the input end of the nonlinear load circuit is connected to the output end of a three-phase power grid, one end of the first filter circuit is connected to the A-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the A-phase bridge arm; one end of the second filter circuit is connected to the C-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the C-phase bridge arm; the midpoint between the upper and lower bridge arms of the B-phase bridge arm is connected to the B-phase output end of the three-phase power grid, characterized in that, Include: A first parameter acquisition module, configured to acquire the A-phase load current, B-phase load current, and C-phase load current at the input end of the non-linear load circuit at the current moment, the voltage outer loop control quantity corresponding to the DC side capacitor, the first line voltage between phases A and B and the second line voltage between phases C and B at the output end of the three-phase power grid, as well as the first output current of the first filter circuit, the first capacitor voltage of the first filter circuit, the second output current of the second filter circuit, and the second capacitor voltage of the second filter circuit; A first command current calculation module, configured to perform fundamental wave difference processing on the A-phase load current, B-phase load current, C-phase load current, and the voltage outer loop control quantity to obtain the A-phase command current and C-phase command current of the three-phase bridge inverter; A first command current prediction module, configured to perform linear prediction processing on the A-phase command current and C-phase command current to obtain the A-phase command current and C-phase command current at the next moment; The first output signal calculation module is configured to input the first line voltage, the second line voltage, the first output current, the second output current, the first capacitor voltage, the second capacitor voltage, the A-phase command current at the next moment, and the C-phase command current at the next moment into a preset first active power filter model to obtain the first line voltage modulation signal between phases A and B and the second line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit; The first pulse signal generation module is configured to perform modulation processing on the first line voltage modulation signal and the second line voltage modulation signal to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate harmonics of the three-phase power grid.

8. A control device for an active power filter, the control device for the active power filter being applied to an active power filter system. The active power filter system includes a three-phase bridge inverter circuit, an asymmetric filter circuit, and a non-linear load circuit. The asymmetric filter circuit includes a third filter circuit and a fourth filter circuit. The three-phase bridge inverter circuit includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and a DC-side capacitor connected in parallel. The input end of the non-linear load circuit is connected to the output end of a three-phase power grid. One end of the third filter circuit is connected to the A-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the A-phase bridge arm. One end of the fourth filter circuit is connected to the C-phase output end of the three-phase power grid, and the other end is connected to the midpoint between the upper and lower bridge arms of the C-phase bridge arm. The midpoint between the upper and lower bridge arms of the B-phase bridge arm is connected to the B-phase output end of the three-phase power grid, and it is characterized in that, including: The second parameter acquisition module is configured to acquire the A-phase load current, B-phase load current, and C-phase load current at the input end of the nonlinear load circuit at the current moment, the voltage outer loop control quantity corresponding to the DC side capacitor, the first line voltage between phases A and B and the second line voltage between phases C and B at the output end of the three-phase power grid, as well as the third output current of the third filter circuit and the fourth output current of the fourth filter circuit; The second command current calculation module is configured to perform fundamental wave difference processing on the A-phase load current, B-phase load current, C-phase load current, and the voltage outer loop control quantity to obtain the A-phase command current and C-phase command current of the three-phase bridge inverter; The second command current prediction module is configured to perform linear prediction processing on the A-phase command current and C-phase command current to obtain the A-phase command current and C-phase command current at the next moment; The second output signal calculation module is configured to input the first line voltage, the second line voltage, the third output current, the fourth output current, the A-phase command current at the next moment, and the C-phase command current at the next moment into a preset second active power filter model to obtain the third line voltage modulation signal between phases A and B and the fourth line voltage modulation signal between phases C and B of the three-phase bridge inverter circuit; The second pulse signal generation module is configured to perform modulation processing on the third line voltage modulation signal and the fourth line voltage modulation signal to obtain a PWM pulse signal, and the PWM pulse signal is used to eliminate harmonics of the three-phase power grid.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, the steps of the control method of the active power filter according to any one of claims 1-3 or claims 4-6 are implemented.

10. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, the control method of the active power filter according to any one of claims 1-3 or claims 4-6 is executed.

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