Active power filter control method in hybrid compensation system and computer device

Abstract

The invention discloses an active power filter control method in a hybrid compensation system and a computer device. The hybrid compensation system comprises a power grid, an active power filter and a passive power filter. The active power filter and the passive power filter are connected in parallel between a power grid and a load. According to the invention, the APF is controlled to simulate the resistance at the harmonic frequency to realize harmonic suppression of the load, so that the current resonance amplification of the PPF can be avoided when the APF and the PPF compensate the harmonic at the same frequency, and the stable operation of the hybrid compensation system is ensured.

Description

Technical Field

[0001] The invention relates to the field of current conversion technology in electrical engineering, in particular to an active power filter control method and a computer device in a hybrid compensation system. Background Art

[0002] With the development and popularization of nonlinear loads such as power electronic equipment and motors, power quality problems in power grids have become increasingly serious, especially low power factor and harmonic pollution. Power quality problems increase losses, reduce equipment reliability and safety, and affect service life. PPF has high reliability and APF has good compensation flexibility. Therefore, PPF, APF and the hybrid compensation system composed of them are the main power quality management methods for power grids.

[0003] In a hybrid compensation system, PPF and APF usually compensate for harmonics of different frequencies. However, when the harmonic content of a certain frequency is too high, in order to ensure the compensation effect, APF and PPF need to compensate for the harmonics of the same frequency. However, using traditional control strategies may cause current resonance amplification in PPF, causing overcurrent tripping and affecting system operation reliability. Therefore, it is necessary to suppress PPF resonance in the hybrid compensation system to ensure stable system operation.

[0004] In recent years, the invention patent applications in the field of power quality management are compared as follows: "Control method for HAPF harmonic compensation and resonance suppression based on grid-side current sampling" (publication number: CN109149579A, publication date: January 4, 2019), "A method for automatic detection of grid resonance based on active injection current" (publication number: CN104330627A, publication date: February 4, 2015), both of which study the resonance problem of passive compensation equipment in hybrid compensation systems, but the passive compensation equipment is a fixed capacitor, and the resonance problem of inductor-capacitor series passive power filters is not studied. The method based on grid-side current sampling in CN109149579A cannot suppress the current resonance amplification of LC series passive filters, and CN104330627A is used for online detection of resonance, and does not include resonance suppression. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an active power filter control method and a computer device in a hybrid compensation system in view of the deficiencies in the prior art, which can avoid PPF resonance while achieving power quality management and ensure stable operation of the system.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for controlling an active power filter in a hybrid compensation system, the hybrid compensation system comprising a power grid, an active power filter and a passive power filter; the active power filter and the passive power filter are both connected in parallel between the power grid and the load; the method comprises:

[0007] S1, collect the three-phase voltage v at the common coupling point a 、v b 、v c and the three-phase compensation current i of the active power filter ca 、i cb 、i cc And the grid voltage phase θ is obtained through the phase-locked loop;

[0008] S2, according to the obtained grid voltage phase θ, the PCC three-phase voltage is transformed through park C abc / dq Get the d and q axis voltage v d 、v q , extract the DC component through a low-pass filter Further get the AC component The AC component is transformed by park inverse transformation C dq / abc Get PCC three-phase harmonic voltage v ah 、v bh 、v ch ;

[0009] S3, pass the PCC three-phase harmonic voltage through the virtual resistance link to obtain the active power filter three-phase current reference value i ca_ref 、i cb_ref 、i cc_ref ,i cx_ref =-v xh G R Among them, G R is a virtual resistor, x = a, b, c;

[0010] S4, after comparing the three-phase current reference value of the active power filter with the three-phase compensation current of the active power filter, the difference is sent to the current loop controller to obtain the modulation wave signal of the active power filter;

[0011] S5. Perform pulse width modulation on the active power filter modulation wave signal to obtain an active power filter switch trigger signal.

[0012] The present invention realizes harmonic control of the load by controlling the APF to simulate resistance at the harmonic frequency, so that when the APF and PPF compensate for the same frequency harmonics, the PPF current resonance amplification can be avoided, thereby ensuring the stable operation of the hybrid compensation system.

[0013] Rh is the harmonic virtual resistance, R n is the 5th, 7th, 11th and 13th harmonic virtual resistance, ω0 is the fundamental frequency angular frequency, ω c is the cut-off frequency.

[0014] The current loop controller transfer function is: Among them, K P is the proportionality coefficient, K R is the resonance coefficient, ω0 is the fundamental angular frequency.

[0015] As an inventive concept, the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the steps of the above method.

[0016] Compared with the prior art, the present invention has the following beneficial effects: the present invention achieves harmonic control of the load by controlling the APF to simulate resistance at the harmonic frequency, so that when the APF and PPF compensate for the same frequency harmonics, the PPF current resonance amplification can be avoided, thereby ensuring the stable operation of the hybrid compensation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a main circuit structure diagram of the hybrid compensation system involved in the present invention;

[0018] Figure 2 This is a control block diagram of an active power filter in a hybrid compensation system proposed by the present invention;

[0019] Figure 3 The PCC point voltage, grid current, load current and PPF current after power quality management using traditional methods;

[0020] Figure 4 The PCC point voltage, grid current, load current and PPF current after the power quality management is performed by using the present invention;

[0021] Figure 5 It is a locally enlarged waveform diagram of the PCC point voltage, grid current, load current and PPF current after the power quality is managed by using the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] like Figure 1 and Figure 2 As shown, an APF control method in an APF and PPF hybrid compensation system of an embodiment of the present invention, the hybrid compensation system includes: a power grid, an APF, a PPF and a load. The power grid includes a line equivalent inductance, the APF is a three-phase full-bridge inverter with LCL filtering, and the PPF is composed of an inductor and a capacitor in series, which are connected in parallel with the APF at a common coupling point to achieve reactive power compensation and harmonic control for the load, and the load is a diode rectifier nonlinear load. The control method includes the following steps:

[0025] S1, collect the three-phase voltage v at the common coupling point (PCC) a 、v b 、v c and APF three-phase compensation current i ca 、i cb 、i cc , and obtain the grid voltage phase θ through a phase-locked loop (PLL);

[0026] S2, according to the obtained grid voltage phase, the PCC three-phase voltage is transformed through park C abc / dq Get the d and q axis voltage v d 、v q , extract the DC component through a low-pass filter (LPF) Further get the AC component After park inverse transformation C dq / abc Get PCC three-phase harmonic voltage v ah 、v bh 、v ch ;

[0027] S3, the PCC three-phase harmonic voltage is obtained through the virtual resistance link to obtain the APF three-phase current reference value i ca_ref 、i cb_ref 、i cc_ref ,i cx_ref =-v xh G R ;

[0028] S4, after comparing the APF three-phase current reference value with the APF three-phase compensation current, the difference current loop controller G i , get the APF modulation wave signal, the current loop control adopts proportional resonance control K P is the proportionality coefficient, K R is the resonance coefficient, ω0 is the fundamental angular frequency;

[0029] S5. Obtaining a switch trigger signal of the active power inverter part through pulse width modulation.

[0030] Among them, the virtual resistance link in step S3 is: R h is the harmonic virtual resistance, R n is the 5th, 7th, 11th and 13th harmonic virtual resistance, ω0 is the fundamental frequency angular frequency, ω c By controlling the virtual resistance based on the harmonic voltage of the power grid, the passive filter current amplification caused by the compensation of the load harmonic current can be avoided.

[0031] The following is used to verify that the embodiment of the present invention can effectively suppress the passive filter current resonance amplification and ensure the load harmonic compensation effect.

[0032] System parameters:

[0033] System line voltage V S =380V, system frequency f=50Hz, grid impedance L S =0.2mH;

[0034] PPF parameters:

[0035] Capacitor C PPF =80μF, inductor L PPF =5.1mH;

[0036] Load parameters:

[0037] Inductance L nl =2mH, resistor R nL =15Ω, capacitor C nl =330μF.

[0038] The following are the simulation results for the above parameters:

[0039] Figure 3 The simulation results after using traditional methods to manage power quality are PCC point voltage, grid current, load current and PPF current. Using traditional control methods, APF and PPF perform harmonic compensation at the same frequency, which will cause the PPF current to be amplified, resulting in overcurrent tripping and affecting the normal operation of the system.

[0040] Figure 4 The simulation results after using the embodiment of the present invention to manage power quality are as follows: PCC point voltage, grid current, load current and PPF current. Using the control strategy proposed in the present invention, APF and PPF perform harmonic compensation at the same frequency, which will not cause the PPF current to be amplified, thus ensuring the normal operation of the system. Figure 5This is a partial enlarged diagram of the simulation results after the power quality management is performed using the present invention, which are the PCC point voltage, grid current, load current and PPF current. The load current THD is 31.1%, and the grid current THD after the hybrid compensation system is compensated is 4.2%. Therefore, the control strategy proposed in the present invention can ensure the harmonic compensation effect under the hybrid compensation system.

[0041] The above simulation results prove that when the present invention enables APF and PPF to compensate for harmonics of the same frequency, the PPF current resonance amplification can be avoided and the harmonic compensation effect can be ensured.

[0042] Example 2

[0043] Embodiment 2 of the present invention provides a computer device corresponding to the above-mentioned embodiment 1, which may be a processing device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of the above-mentioned embodiment.

[0044] The terminal device of this embodiment includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method in the above-mentioned embodiment 1.

[0045] In some implementations, the memory may be a high-speed random access memory (RAM), and may also include a non-volatile memory, such as at least one disk memory.

[0046] In some other implementations, the processor may be a central processing unit (CPU), a digital signal processor (DSP), or other general-purpose processors of various types, which are not limited herein.

[0047] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0048] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A control method for an active power filter in a hybrid compensation system, wherein the hybrid compensation system comprises a power grid, an active power filter and a passive power filter; the active power filter and the passive power filter are both connected in parallel between the power grid and the load; characterized in that: The method includes: S1, collect the three-phase voltage v at the common coupling point a 、v b 、v c and the three-phase compensation current i of the active power filter ca 、i cb 、i cc And the grid voltage phase θ is obtained through the phase-locked loop; S2, according to the obtained grid voltage phase θ, the PCC three-phase voltage is transformed through park C abc / dq Get the d and q axis voltage v d 、v q , extract the DC component through a low-pass filter Further get the AC component The AC component is transformed by park inverse transformation C dq / abc Get PCC three-phase harmonic voltage v ah 、v bh 、v ch ; S3, pass the PCC three-phase harmonic voltage through the virtual resistance link to obtain the active power filter three-phase current reference value i ca_ref 、i cb_ref 、i cc_ref ,i cx_ref =-v xh G R Among them, G R is a virtual resistor, x = a, b, c; S4, after comparing the three-phase current reference value of the active power filter with the three-phase compensation current of the active power filter, the difference is sent to the current loop controller to obtain the modulation wave signal of the active power filter; S5. Perform pulse width modulation on the active power filter modulation wave signal to obtain an active power filter switch trigger signal.

2. The active power filter control method in the hybrid compensation system according to claim 1, characterized in that: R h is the harmonic virtual resistance, R n is the 5th, 7th, 11th and 13th harmonic virtual resistance, ω0 is the fundamental frequency angular frequency, ω c is the cut-off frequency.

3. The active power filter control method in the hybrid compensation system according to claim 1, characterized in that: The current loop controller transfer function is: Among them, K P is the proportionality coefficient, K R is the resonance coefficient, ω0 is the fundamental angular frequency.

4. A computer device comprising a memory, a processor and a computer program stored in the memory; characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 3.

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