Control method, system and storage medium of hybrid active power filter

Abstract

The application discloses a control method and system of a hybrid active power filter and a storage medium, wherein the inductance value and the capacitance value of a passive power filter are taken as inputs of a particle swarm optimization method to obtain optimized inductance value and capacitance value; when the harmonic number filtered by the passive power filter is the same as the harmonic number filtered by the active power filter, the active power filter is equivalent to a virtual LC filter with the same structure as the passive power filter; otherwise, the active power filter is equivalent to a virtual resistor; a harmonic compensation current reference value of the active power filter is obtained; the harmonic compensation current reference value and a reactive compensation current reference value are superimposed to obtain a total reference current of the active power filter, and the total reference current is taken as an input of a proportional resonant controller, and the output of the proportional resonant controller is PWM modulated. The application eliminates the harmonic current amplification problem of the passive power filter and improves the stability and compensation performance of the power system.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a control method, system, and storage medium for a hybrid active power filter. Background Technology

[0002] In power systems, hybrid active power filters (HAPFs) are widely used for power quality compensation due to their high reliability and flexibility. Traditional HAPFs achieve harmonic suppression by connecting an active power filter (APF) and a passive power filter (PPF) in parallel, but this approach has the following drawbacks:

[0003] 1. Sensor redundancy: Traditional methods require independent measurement of load current and PPF current to generate APF reference current, which increases hardware costs.

[0004] 2. Current divergence: If the total current (load current + PPF current) is used as the APF reference current, it will cause the PPF harmonic current to diverge, triggering overcurrent protection and reducing system reliability.

[0005] 3. Insufficient stability: Existing control strategies are mostly aimed at suppressing single resonances, without considering the balance between compensation effect and stability when APF and PPF are running in tandem.

[0006] Existing solutions (such as TCLC-HAPF and adaptive control strategies) can partially alleviate the problem, but they do not fundamentally solve the issues of PPF current amplification and system stability. Therefore, there is an urgent need for a co-design method that can eliminate harmonic amplification, reduce sensor dependence, and ensure system stability. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a control method, system and storage medium for a hybrid active power filter to address the shortcomings of the prior art, thereby eliminating the harmonic current amplification problem of passive power filters and improving the stability and compensation performance of the power system.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a control method for a hybrid active power filter, wherein the hybrid active power filter includes an active power filter and a passive power filter, and the active power filter and the passive power filter are connected in parallel to the power grid; comprising the following steps:

[0009] The inductance and capacitance values ​​of the passive power filter are used as inputs to the particle swarm optimization method to obtain the optimized inductance and capacitance values.

[0010] The harmonic order filtered by the passive power filter is determined based on the optimized inductance and capacitance values. When the harmonic order filtered by the passive power filter is the same as that filtered by the active power filter, the active power filter is equivalent to a virtual LC filter with the same structure as the passive power filter; otherwise, the active power filter is equivalent to a virtual resistor.

[0011] Extract the harmonic voltage at the common coupling point of the active power filter and the passive power filter to obtain the reference value of the harmonic compensation current of the active power filter;

[0012] The harmonic compensation current reference value is superimposed with the reactive power compensation current reference value of the active power filter to obtain the total reference current of the active power filter. The total reference current is used as the input of the proportional resonant controller, and the output of the proportional resonant controller is PWM modulated to obtain the drive signal for switching the active power filter transistor on and off.

[0013] The objective function used to optimize the inductance and capacitance values ​​is: Where, min H is the minimum harmonic content of the grid current, and I sn and I Loadn These are the nth harmonic currents of the power grid and the load, respectively; the constraints include a power factor ≥ 0.97 after compensation, and the passive power filter being inductive at the harmonic frequency.

[0014] The parameters of the virtual LC filter satisfy: L virtual =0.98L PPF C virtual =0.98C PPF L virtual and C virtual L represents virtual inductance and virtual capacitance. PPF and C PPF The inductors and capacitors represent the optimized passive power filter.

[0015] The process of obtaining the harmonic compensation current reference value of the active power filter includes: extracting the harmonic voltage V at the common coupling point using a notch filter. xh The harmonic voltage V xh Input intelligent impedance section G SI Get i cx_ref1 Calculate the reference value i of reactive power compensation current based on the load conditions. Lxq The two are added together to obtain the reference value i of the harmonic compensation current of the active power filter. cx_ref =i cx_ref1 +i Lxq ;icx_ref1=G SI ·V xh .

[0016] X SI Represents the intelligent impedance value, G BPF This represents a bandpass filter, Num represents the compensation rate coefficient, and L... virtual =0.98L PPF C virtual =0.98C PPF L virtual and C virtual Represents virtual inductance and virtual capacitance;

[0017] When the active power filter is used as a virtual resistor:

[0018]

[0019] When the active power filter is used as a virtual LC filter:

[0020]

[0021] X PPF X represents the harmonic reactance of a passive power filter. s Harmonic reactance, K, represents the inductance of the power grid. C This represents the harmonic compensation rate of the active power filter. I cn and I Loadn These are the nth harmonic current compensated by the active power filter and the nth harmonic current of the load, respectively.

[0022] Q Total Q represents the total reactive power demand. PPF V represents the reactive power compensated by the passive power filter. pcc The effective value of the line voltage at the common coupling point.

[0023] The transfer function G of the proportional resonant controller i (s) is: Where K p K is the proportionality coefficient. rn Let ω be the resonant coefficient of the nth harmonic. cn ω is the bandwidth of the proportional resonant controller, ω0 is the fundamental angular frequency of the power grid, and s is the Laplace operator.

[0024] When the grid frequency deviation exceeds the set value, the inductance and capacitance values ​​of the passive power filter are re-optimized.

[0025] As an inventive concept, the present invention also provides a control system for a hybrid active power filter, 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.

[0026] As an inventive concept, the present invention also provides a computer-readable storage medium having a computer program / instructions stored thereon; when the computer program / instructions are executed by a processor, they implement the steps of the above-described method.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. Elimination of harmonic amplification: Simulation and experiments show that the method of the present invention can reduce the harmonic amplification rate of PPF current to below 0.17 (0.41 in the traditional method), effectively avoiding overcurrent protection triggering.

[0029] 2. Improved compensation performance: When the APF is used as a virtual LC filter, the total harmonic distortion (THD) of the grid current is reduced from 27% to 5.3%, which is better than the 10.4% of the virtual resistance mode.

[0030] 3. Enhanced reliability: Through PSO (Particle Swarm Optimization) and intelligent impedance control, the system maintains stable operation even when the grid frequency fluctuates by ±0.5Hz. Attached Figure Description

[0031] Figure 1 This is a circuit structure diagram of the HAPF system, including the APF, PPF, and load connection methods.

[0032] Figure 2 By comparing different current detection locations (point A and point B), the mechanism by which total current detection causes PPF current divergence is explained.

[0033] Figure 3 The harmonic equivalent circuit under the traditional control strategy (before and after compensation).

[0034] Figure 4 For the transfer function I Ph (s) / I Loadh The system block diagram of (s) reveals the existence of poles in the right half-plane.

[0035] Figure 5 The zero-pole distribution diagram of the system based on intelligent impedance control shows the improved system stability.

[0036] Figure 6 A flowchart for PPF parameter optimization is provided to illustrate the iterative process of the PSO algorithm.

[0037] Figure 7 The current harmonic content after PPF filtering by PSO design indicates that the grid current harmonics have been effectively reduced.

[0038] Figure 8 For I sn / I LoadnThe amplitude-frequency response curve indicates that the nth harmonic will not be amplified.

[0039] Figure 9 The comparison of harmonic residual rates under different compensation modes highlights the advantages of the virtual LC filter.

[0040] Figure 10 This is an overall block diagram of the intelligent impedance control strategy, which includes harmonic extraction, impedance generation, and current control modules.

[0041] Figure 11 For i px and i cx Simulation waveforms: (a) under conventional control strategy; (b) control strategy proposed in the embodiments of the present invention.

[0042] Figure 12 When APF is used as a virtual resistor, v x i sx i cx i px i Loadx Experimental waveforms of THD.

[0043] Figure 13 When the APF is used as a virtual LC filter, v x i sx i cx i px i Loadx Experimental waveforms of THD. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for the collaborative design and harmonic suppression of hybrid active power filters based on intelligent impedance, including the following steps:

[0047] 1. Analysis of PPF Harmonic Current Amplification Mechanism: A harmonic equivalent circuit of the HAPF is established to reveal the cause of PPF current divergence from both circuit and frequency domain perspectives. When point B (the sum of load current and PPF current) is used as the APF reference current sampling point for compensation, the APF compensation current increases the PPF current. This increased current then serves as the reference value for the APF compensation current, causing the APF compensation current and PPF current to diverge, ultimately leading to the PPF overcurrent protection shutdown. Analysis of the system's transfer function and pole-zero plot reveals the presence of right-half-plane poles, resulting in system instability.

[0048] 2. PPF Optimization Design: The PPF parameters are optimized based on the load reactive power and the number of filters. The optimization objective is to minimize the harmonic content of the grid current. Constraints include avoiding overcompensation of reactive power (limiting the compensated power factor to 0.97, and calculating the reactive power compensated by the PPF accordingly) and avoiding grid current harmonic amplification (ensuring the PPF is inductive at harmonic frequencies; considering grid frequency fluctuations and component parameter uncertainties, the resonant frequency of the PPF is set to 97% of the rated harmonic frequency). The Particle Swarm Optimization (PSO) algorithm is used for PPF parameter optimization. The specific steps are as follows:

[0049] 1) Initialize particle position (X) i Represents PPF (inductance value, capacitance and inductance values ​​are subject to boundary conditions) and speed.

[0050] 2) Calculate the fitness value of the particles based on the fitness function, and select the harmonic content optimization target as the fitness function.

[0051] 3) Compare the fitness value of each particle with its historical best value. If the fitness value is better, update the individual's best value.

[0052] 4) Compare the individual fitness value of each particle with the global optimal fitness value. If the individual fitness value is better, update the global optimal value.

[0053] 5) Update the position and velocity of the particles according to the basic principles of particle swarm optimization.

[0054] 6) Check if the termination condition is met (reaching the minimum fitness value or the maximum number of iterations). If not, update the inertia weights and return to step 2.

[0055] 3. APF intelligent impedance control strategy:

[0056] 1) Virtual LC Filter Mode: For harmonics already compensated by the PPF (e.g., the 5th harmonic), the APF is equivalent to a virtual LC filter with the same structure as the PPF. The compensation rate of the APF for the 5th harmonic current, the residual rate of the 5th harmonic on the grid side, and the harmonic suppression rate are calculated under different impedance values. Comparison shows that when the APF operates as a virtual LC filter, it achieves better harmonic suppression on the grid side. Therefore, in cases where the PPF does not compensate for other low-order harmonics, the APF can operate as a resistor; however, when compensating for harmonics of the same frequency as the PPF, the APF is more suitable as an LC filter, enhancing the harmonic suppression effect. The specific control flow is as follows:

[0057] S1. Harmonic voltage at the point of common coupling (PCC) is extracted using a notch filter;

[0058] S2. Obtain the APF harmonic compensation current reference value through the intelligent impedance section;

[0059] S3. Add the reactive power compensation current reference value to obtain the APF compensation current reference value.

[0060] S4. The gate signal is obtained through APF current control and pulse width modulation (PWM).

[0061] 2) Virtual Resistance Mode: For low-order harmonics (such as 7th, 11th, and 13th harmonics) without a PPF, the APF is equivalent to a resistor. The compensation rate of the APF for the 5th harmonic current, the residual rate of the 5th harmonic on the grid side, and the harmonic suppression rate are calculated under different impedance values. The impedance value required for different load harmonic current compensation rates is obtained to suppress the residual harmonics.

[0062] 4. PPF Stability Analysis: Based on the proposed intelligent impedance control strategy, the harmonic equivalent circuit of the HAPF system is established, the system transfer function is calculated, and the pole-zero plot is drawn. The results show that the system has no right-half-plane poles, the PPF current does not diverge, and the system is stable.

[0063] Power grid parameters: line voltage 10kV, frequency 50Hz, power grid inductance L s =0.3mH.

[0064] PPF parameters: After PSO optimization, the passive filter inductor L PPF =5.28mH, passive filter capacitor C PPF =81.7μF. The optimized PPF was used to filter out grid harmonics, and the resulting harmonic content after filtering is as follows: Figure 7 As shown in the figure. After PPF compensation, the harmonics of the grid current are reduced to about 0.5 times that of the load current harmonics. Figure 8 isI sn / I LoadnThe amplitude-frequency characteristic curve shows that the nth load harmonic is not amplified in the power grid, indicating a good optimization effect.

[0065] APF control parameter: proportional coefficient K p =1.2, resonance coefficient K rn =10, bandwidth ω cn =15 rad / s. Figure 9 The APF was demonstrated at a harmonic current compensation rate K across a series of identical loads. c Below, the residual harmonic rate K on the grid side is obtained by using two different schemes: virtual resistor and virtual LC filter. h It is easy to see that when compensating for harmonics of the same order as the PPF, the APF, operating as an LC filter, can achieve lower harmonic residuals. This achieves the optimal effect of simultaneously compensating for grid harmonics with both the APF and PPF in parallel. When compensating for harmonics of different orders as the PPF, the APF can operate in virtual resistance mode, i.e., intelligent impedance adaptive control technology. Figure 10 This is the overall control block diagram of the technology.

[0066] Figure 10 The PPF (Power Filter) is the state after PSO (Power Optimization) parameter optimization, and it is directly connected in parallel with the power grid as a separate filter. In the APF (Auxiliary Filter) section, the load harmonic current i on the power grid is first extracted. Lx After a 3 / 2 transformation, the q-axis component i is obtained. Lq i is then obtained through a low-pass filter. Lq The DC component is then transformed by 2 / 3 to obtain the reactive power compensation current reference value i. Lxq Meanwhile, harmonic voltages at the coupling point are extracted using a notch filter and controlled by the intelligent impedance section G. SI Obtain the reference value i of the APF harmonic compensation current. cxh_ref This current is compared with the compensation current i output by the APF. cx Add and combine with i Lxq By forming negative feedback, the final drive current signal can be obtained. After PI modulation, a PWM signal is generated and input into the inverter of the APF to complete the task of filtering harmonics together with the PPF.

[0067] ● Simulation platform: The HAPF model is built based on MATLAB / Simulink, and the load includes linear load (RL series) and nonlinear load (diode rectifier).

[0068] • Experimental results:

[0069] Figure 11 This indicates that under both conventional current compensation and the control strategy proposed in this embodiment of the invention, the APF compensation current i cx and PPF output current ipx Simulation results. Under traditional control, the APF compensation current i cx and PPF output current i px The divergence is severe (exceeding 1000A), while the APF compensation current i under the proposed method is... cx and PPF current i px Stable (not exceeding 500A), indicating that the APF compensation current i under the traditional current compensation strategy is stable. cx and PPF output current i px The two currents diverge, but the control strategy proposed based on the embodiments of the present invention will not cause the two currents to diverge;

[0070] Figure 12 When APF is used as a virtual resistance, v x i sx i cx i px i Loadx The experimental waveforms of THD are shown in the figure. It can be seen from the figure that the harmonic THD is 27.1% on the load side. After being filtered by APF and PPF, it is reduced to 10.4%, which has a certain filtering effect. At this time, the voltage waveform is basically sinusoidal, while the current waveform has a certain degree of distortion.

[0071] Figure 13 Indicates v when the APF is used as a virtual LC filter x i sx i cx i px i Loadx The experimental waveforms for THD are shown in the figure. It can be seen from the figure that the THD on the load side is 27.1%, which is reduced to 5.3% after being filtered by both APF and PPF, demonstrating excellent filtering effect. At this point, both the voltage and current waveforms are essentially sinusoidal. Figure 12 The comparison shows that when the APF is used as a virtual LC filter, the THD of the grid current is smaller (reduced from 10.4% to 5.3%), and the grid current waveform is closer to a sine wave. This indicates that under the same compensation current, the harmonic current residual rate is lower and the harmonic compensation effect is better.

[0072] Example 2

[0073] Embodiment 2 of the present invention provides a control system corresponding to Embodiment 1 above, including 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 of Embodiment 1 above.

[0074] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0075] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0076] Example 3

[0077] Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to Embodiment 1 above, on which a computer program / instructions are stored. When the computer program / instructions are executed by a processor, they implement the steps of the method of Embodiment 1 above.

[0078] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof.

[0079] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0080] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0081] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0082] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0083] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A control method for a hybrid active power filter, the hybrid active power filter comprising an active power filter and a passive power filter, wherein the active power filter and the passive power filter are connected in parallel to the power grid; characterized in that, Includes the following steps: The inductance and capacitance values ​​of the passive power filter are used as inputs to the particle swarm optimization method to obtain the optimized inductance and capacitance values. The harmonic order filtered by the passive power filter is determined based on the optimized inductance and capacitance values. When the harmonic order filtered by the passive power filter is the same as that filtered by the active power filter, the active power filter is equivalent to a virtual LC filter with the same structure as the passive power filter; otherwise, the active power filter is equivalent to a virtual resistor. Extract the harmonic voltage at the common coupling point of the active power filter and the passive power filter to obtain the reference value of the harmonic compensation current of the active power filter; The harmonic compensation current reference value is superimposed with the reactive power compensation current reference value of the active power filter to obtain the total reference current of the active power filter. The total reference current is used as the input of the proportional resonant controller, and the output of the proportional resonant controller is PWM modulated to obtain the drive signal for the switching of the active power filter. The process of obtaining the harmonic compensation current reference value of the active power filter includes: extracting the harmonic voltage V at the common coupling point using a notch filter. xh The harmonic voltage V xh Input intelligent impedance section G SI Get i cx_ref1 Calculate the reference value i of reactive power compensation current based on the load conditions. Lxq The two are added together to obtain the reference value i of the harmonic compensation current of the active power filter. cx_ref =i cx_ref1 +i Lxq ;icx_ref1 =G SI ⋅V xh ; X SI Represents the intelligent impedance value, G BPF This represents a bandpass filter, Num represents the compensation rate coefficient, and L... virtual =0.98L PPF C virtual =0.98C PPF L virtual and C virtual Represents virtual inductance and virtual capacitance; When the active power filter is used as a virtual resistor: ； When the active power filter is used as a virtual LC filter: ； X PPF X represents the harmonic reactance of a passive power filter. s Harmonic reactance, K, represents the inductance of the power grid. C This represents the harmonic compensation rate of the active power filter. I cn and I Loadn These are the nth harmonic current compensated by the active power filter and the nth harmonic current of the load, respectively.

2. The control method for the hybrid active power filter according to claim 1, characterized in that, The objective function used to optimize the inductance and capacitance values ​​is: Where, min H is the minimum harmonic content of the grid current, and I sn and I Loadn These are the nth harmonic currents of the power grid and the load, respectively; the constraints include a power factor ≥ 0.97 after compensation, and the passive power filter being inductive at the harmonic frequency.

3. The control method for the hybrid active power filter according to claim 1, characterized in that, The parameters of the virtual LC filter satisfy: L virtual =0.98L PPF C virtual =0.98C PPF L virtual and C virtual L represents virtual inductance and virtual capacitance. PPF and C PPF The inductors and capacitors represent the optimized passive power filter.

4. The control method for the hybrid active power filter according to claim 1, characterized in that, Q Total Q represents the total reactive power demand. PPF V represents the reactive power compensated by the passive power filter. pcc The effective value of the line voltage at the common coupling point.

5. The control method for the hybrid active power filter according to claim 1, characterized in that, The transfer function of the proportional resonant controller for: K p K is the proportionality coefficient. rn Let ω be the resonant coefficient of the nth harmonic. cn ω is the bandwidth of the proportional resonant controller, ω0 is the fundamental angular frequency of the power grid, and s is the Laplace operator.

6. The control method for the hybrid active power filter according to claim 1, characterized in that, When the grid frequency deviation exceeds the set value, the inductance and capacitance values ​​of the passive power filter are re-optimized.

7. A control system for a hybrid active power filter, 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 6.

8. A computer-readable storage medium having a computer program / instructions stored thereon; characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method according to any one of claims 1 to 6.

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