CN110086173A - Parallel APF harmonic amplification effect suppression method and system - Google Patents

Abstract

The disclosure relates to a method and a system for suppressing APF harmonic amplification effect of a parallel active power filter. Wherein, the method comprises the following steps: generating a transfer function from the output voltage of the inverter to the network side current based on a two-level parallel APF main circuit topological structure, determining a system control loop according to the transfer function, and establishing a control system model; and controlling the harmonic amplification effect of the parallel APF according to the control system model. The method can effectively realize the suppression of harmonic amplification effect, balance the system efficiency and improve the system stability.

Description

Parallel APF harmonic amplification effect suppression method and system

technical field

The present disclosure relates to the field of power electronics, in particular, to a method and system for suppressing the harmonic amplification effect of a parallel APF.

Background technique

Active Power Filter (APF) is one of the effective methods to suppress harmonics in the power grid, and has been extensively studied in recent years. Since the loads put into the power grid have different characteristics, the treatment effect after APF is put into use is also different. Parallel APF is suitable for compensating current source non-linear loads, and series APF is suitable for compensating voltage source non-linear loads. The series APF has not been applied on a large scale due to its large loss and complicated control mechanism; compared with this, the theory and technology research of the parallel APF is more mature, so it is widely used in industrial sites and used in Compensates voltage source nonlinear loads. When the parallel APF compensates the voltage source nonlinear load, the system has the characteristics of resonance and peak current overcurrent, that is, the harmonic amplification effect. The countermeasures of the existing technology are generally: 1) A reactor with a certain inductance value is connected in series on the AC side of the load ; 2) Reduce the harmonic compensation rate.

For the existing technology 1), although the system resonance can be effectively reduced, the reactive power caused by the reactance is still compensated by the APF; for the existing technology 2), if the load changes, the originally set compensation rate may no longer be suitable.

It can be seen from the above that it is necessary to provide one or more technical solutions capable of at least solving the above problems.

It should be noted that the information disclosed in the above background section is only for enhancing the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to those of ordinary skill in the art.

SUMMARY OF THE INVENTION

The purpose of the present disclosure is to provide a parallel APF harmonic amplification effect suppression method and system, and then at least to some extent overcome one or more problems caused by limitations and defects of related technologies.

According to one aspect of the present disclosure, a parallel APF harmonic amplification effect suppression method is provided, including:

The step of establishing the control system is to generate a transfer function from the inverter output voltage to the grid-side current based on the two-level parallel APF main circuit topology, determine the system control loop according to the transfer function, and establish a control system model; wherein, Determining the system control loop according to the transfer function includes: according to the vector proportional integral controller based on the two-phase stationary coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and using the harmonic current compensation determined based on the fuzzy controller rate to achieve output current oscillation suppression;

The amplification effect suppression step is to control the parallel APF according to the control system model to suppress the harmonic amplification effect of the parallel APF.

In an exemplary embodiment of the present disclosure, the control system modeling step further includes:

The vector proportional integral controller of the two-phase static coordinate system is obtained based on the harmonic current controller with delay compensation added to the multi-synchronous rotating coordinate system harmonic current compensation strategy, and the open-loop transfer function of the harmonic current control is:

After the harmonic current amplitude and the rate of change of the harmonic current amplitude are acquired, the harmonic current compensation rate is obtained by looking up a table in a preset harmonic current compensation rate fuzzy rule table.

In an exemplary embodiment of the present disclosure, the control system modeling step further includes:

The two-level parallel APF main circuit topology AC filter is an LCLCLC filter, the damping strategy is a parallel connection of a grid-side inductor with a damping resistor, and the transfer function from the inverter output voltage to the grid-side current is

in,

L _g , L _o , C _f are the main filter, R _d is the damping resistor, which is the main output filter, L _x , C _x form the LC notch filter, which is used to filter out the switching frequency sub-ripple of the APF output, C _d is the supporting capacitance of the DC bus, e _a , e _b , e _c are the three-phase power supply voltages at the common coupling point, i _ga , i _gb , i _gc are the grid currents, i _la , i _lb , i _lc are the load currents , i _fa , i _fb , if _fc are the compensation current output by APF, u _dc is the DC bus voltage;

The system control loop includes fundamental positive sequence current control based on fundamental positive sequence synchronous rotating coordinate system, vector proportional integral control based on two-phase stationary coordinate system, and harmonic compensation rate control based on fuzzy controller.

In an exemplary embodiment of the present disclosure, the control system modeling step further includes:

In the described frequency division harmonic control strategy, the delay compensation angle θ _n is composed of two parts, the digital control delay angle θ _nD and the analog sampling angle θ _nF , and the calculation formula is:

θ _nD = nω _g T _s

θ _nF = arctan(nω _s RC)

θ _n = θ _nFliter + θ _nD

Among them, T _s is the digital sampling period, n is the harmonic order, R and C are the resistance and capacitance of the analog low-pass filter, and ω _s is the cut-off frequency of the low-pass filter;

The transfer function of the multi-synchronous rotating coordinate system harmonic current compensation strategy of the harmonic current controller with delay compensation is:

Among them, k _p and _ki are the proportional coefficient and integral coefficient of the nth harmonic current PI controller under the MSRF strategy, respectively.

In an exemplary embodiment of the present disclosure, the harmonic current amplitude is calculated by the following formula:

The rate of change of the harmonic current amplitude is calculated and determined according to dividing the currently calculated harmonic current amplitude by the harmonic current amplitude a preset number of sampling periods ago.

In an exemplary embodiment of the present disclosure, the control system modeling step further includes:

The harmonic current amplitude is divided into multiple fuzzy subsets of different levels by specifying the sub-harmonic current amplitude 0.15 and 0.35 inflection points;

The harmonic current amplitude change rate passes through the 5% step value inflection point to divide multiple fuzzy subsets of different levels.

In an exemplary embodiment of the present disclosure, the control system modeling step further includes:

The harmonic current amplitude fuzzy subset and the harmonic current amplitude change rate fuzzy subset are defuzzified through the mamdani fuzzy model, and the area center of gravity method is selected to generate the harmonic current amplitude fuzzy subset and the harmonic current amplitude fuzzy subset. The harmonic current compensation rate fuzzy rule table of the corresponding relationship between the value change rate and the harmonic current compensation rate.

In an exemplary embodiment of the present disclosure, the control system modeling step further includes:

The harmonic current compensation rate is not less than 80%.

In one aspect of the present disclosure, a parallel APF harmonic amplification effect suppression system is provided, wherein the system includes:

The control system building module is used to generate a transfer function from the inverter output voltage to the grid side current based on the two-level parallel APF main circuit topology, determine the system control loop according to the transfer function, and establish a control system model; Wherein, determining the system control loop according to the transfer function includes: according to the vector proportional integral controller based on the two-phase stationary coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and using the harmonic current control determined based on the fuzzy controller The current compensation rate realizes the suppression of output current oscillation;

The amplification effect suppression module is used to control the parallel APF according to the control system model, and suppress the harmonic amplification effect of the parallel APF.

The method for suppressing the harmonic amplification effect of the parallel APF provided by the present disclosure is based on the topological structure of the two-level parallel APF main circuit to generate a transfer function from the output voltage of the inverter to the grid-side current, and determine the system control loop according to the transfer function. And establish a control system model; control the parallel APF according to the control system model, and suppress the harmonic amplification effect of the parallel APF. On the one hand, this disclosure proposes a parallel APF compound current control strategy, which dynamically adjusts the compensation rate of each harmonic through a fuzzy controller to balance system efficiency and system stability; on the other hand, this disclosure uses a static coordinate system based The VPI control strategy extracts and compensates each harmonic, effectively suppressing the harmonic amplification effect.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.

Description of drawings

The above and other features and advantages of the present disclosure will become more apparent by describing in detail example embodiments thereof with reference to the accompanying drawings.

FIG. 1 shows a flowchart of a method for suppressing a harmonic amplification effect of a parallel APF according to an exemplary embodiment of the present disclosure;

FIG. 2 shows a topology diagram of a parallel APF main circuit according to an exemplary embodiment of the present disclosure;

Fig. 3 schematically shows an overall control block diagram of a parallel APF according to an exemplary embodiment of the present disclosure;

Fig. 4 schematically shows a control block diagram of an improved MSRF harmonic compensation strategy according to an exemplary embodiment of the present disclosure;

FIG. 5 schematically shows a single-phase equivalent circuit diagram of a parallel-connected APF compensating a voltage source-type nonlinear load according to an exemplary embodiment of the present disclosure;

Fig. 6 schematically shows the fuzzy subset distribution of harmonic compensation rate and its membership function graph according to an exemplary embodiment of the present disclosure;

Fig. 7 shows a system diagram of a parallel-connected APF harmonic amplification effect suppression system according to an exemplary embodiment of the present disclosure.

Detailed ways

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals denote the same or similar parts in the drawings, and thus their repeated descriptions will be omitted.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided in order to give a thorough understanding of embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or that other methods, components, materials, devices, steps, etc. may be employed. In other instances, well-known structures, methods, devices, implementations, materials, or operations are not shown or described in detail to avoid obscuring aspects of the present disclosure.

The block diagrams shown in the drawings are merely functional entities and do not necessarily correspond to physically separate entities. That is, these functional entities may be implemented in software, or in one or more software-hardened modules, or in part of them, or in different networks and/or processor devices and/or microcontroller devices Realize these functional entities in.

In this exemplary embodiment, a method for suppressing the harmonic amplification effect of a parallel APF is firstly provided, as shown in FIG. 1 , the method for suppressing the harmonic amplification effect of the parallel APF may include the following steps:

Control system establishment step S110, based on the two-level parallel APF main circuit topology, generate a transfer function from the inverter output voltage to the grid side current, determine the system control loop according to the transfer function, and establish a control system model; , determining the system control loop according to the transfer function includes: according to the vector proportional integral controller based on the two-phase stationary coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and using the harmonic current determined based on the fuzzy controller The compensation rate realizes the suppression of output current oscillation;

The amplification effect suppression step S120 is to control the parallel APF according to the control system model to suppress the harmonic amplification effect of the parallel APF.

The disclosure provides a parallel APF harmonic amplification effect suppression method. On the one hand, the disclosure proposes a parallel APF compound current control strategy, which dynamically adjusts the harmonic compensation rate of each order through a fuzzy controller to balance the system efficiency and system efficiency. Stable; on the other hand, the present disclosure extracts and compensates each harmonic through a VPI control strategy based on a static coordinate system, thereby effectively suppressing the harmonic amplification effect.

In the control system establishment step S110, the transfer function from the inverter output voltage to the grid-side current can be generated based on the two-level parallel APF main circuit topology, and the system control loop can be determined according to the transfer function, and the control system can be established model; wherein, determining the system control loop according to the transfer function includes: according to the vector proportional integral controller based on the two-phase stationary coordinate system, as a frequency division harmonic control strategy to carry out harmonic current control, and using the method determined based on the fuzzy controller The harmonic current compensation rate realizes output current oscillation suppression.

In an exemplary embodiment of the present invention, the control system modeling step further includes:

The vector proportional integral controller of the two-phase static coordinate system is obtained based on the harmonic current controller with delay compensation added to the multi-synchronous rotating coordinate system harmonic current compensation strategy, and the open-loop transfer function of the harmonic current control is:

After the harmonic current amplitude and the rate of change of the harmonic current amplitude are acquired, the harmonic current compensation rate is obtained by looking up a table in a preset harmonic current compensation rate fuzzy rule table.

In an exemplary embodiment of the present invention, the control system modeling step further includes:

As shown in Figure 2, it is the topological structure diagram of the parallel APF main circuit. The AC filter of the two-level parallel APF main circuit topology is an LCLCLC filter. The transfer function from voltage to grid side current is

in,

L _g , L _o , C _f are the main filter, R _d is the damping resistor, which is the main output filter, L _x , C _x form the LC notch filter, which is used to filter out the switching frequency sub-ripple of the APF output, C _d is the supporting capacitance of the DC bus, e _a , e _b , e _c are the three-phase power supply voltages at the common coupling point, i _ga , i _gb , i _gc are the grid currents, i _la , i _lb , i _lc are the load currents , i _fa , i _fb , if _fc are the compensation current output by APF, u _dc is the DC bus voltage;

As shown in Figure 3, it is the overall control block diagram of APF, ωg is the grid frequency, ed and _{e q} are the grid voltage in the fundamental positive sequence synchronous rotating coordinate system, and i _lα and i _lβ are the loads in the two-phase stationary coordinate system Current, if _fα and i _fβ are the output currents in the two-phase static coordinate system, u _{Hα_ref} and u _{Hβ_ref} are the harmonic current commands in the two-phase static coordinate system, i _ld and i _lq are the fundamental positive sequence synchronous rotating coordinate system load current under , if _fd , i _fq are the output currents in the fundamental positive sequence synchronous rotating coordinate system, u _{Hd_ref} , u _{Hq_ref} are the harmonic current commands in the fundamental positive sequence synchronous rotating coordinate system, and u _{dc_ref} is the DC bus Voltage given value, i _{Fd_ref} is the given value of the fundamental positive sequence active current loop, u _{Fd_ref} and u _{Fq_ref} are the output commands of the fundamental positive sequence current loop, u _{d_ref} and u _{q_ref} are the comprehensive current commands, λ _n (n= 2,3,…) is the compensation rate of the specified sub-harmonic current, u _{Hnα_ref} and u _{Hnβ_ref} are the specified sub-harmonic current commands under the two-phase static coordinate system, i ⁺ _hnd , i ⁺ _hnq are the specified sub-harmonic positive sequence The load current in the synchronous rotating coordinate system, i ^- _hnd and i ^- _hnq are the load currents in the negative sequence synchronous rotating coordinate system of the specified sub-harmonic, i _hnm is the amplitude of the specified sub-harmonic current, and di _hnm is the specified harmonic current Amplitude conversion rate, LPF is a digital low-pass filter (Low Pass Filter, LPF); T ^P _αβ-dq1 , T ^P _dq1-αβ are transformation matrices from a two-phase stationary coordinate system to a fundamental positive sequence synchronous rotating coordinate system and its inverse transformation matrix, T ^P _αβ-dqn and T ^N _αβ-dqn are the transformation matrices from the two-phase stationary coordinate system to the harmonic positive sequence and harmonic negative sequence synchronous rotating coordinate system, T _abc-αβ is the three-phase static The transformation matrix from the coordinate system to the two-phase stationary coordinate system. In order to improve the phase-locking accuracy of the system, a dual second-order generalized integrator software phase-locked loop (Dual Second-order Generalized Integrator PLL, DSPGI-PLL) is used; the PWM strategy is SPWM injected by the third harmonic.

The system control loop includes fundamental positive sequence current control based on fundamental positive sequence synchronous rotating coordinate system, vector proportional integral control based on two-phase stationary coordinate system, and harmonic compensation rate control based on fuzzy controller.

In an exemplary embodiment of the present invention, the control system modeling step further includes:

A vector proportional integral (Vector Proportional Integral, VPI) controller based on Two Phase Static Frame (TPSF) is used as the frequency division harmonic control strategy. This strategy is based on the equivalent simplification of the improved multi-synchronization rotating frame (Multi-Synchronization Reference Frame, MSRF) harmonic current compensation strategy. Compared with the traditional MSRF strategy, the improved MSRF strategy extracts and controls both the positive sequence component and the negative sequence component of each harmonic current, and the compensation performance is improved. The control block diagram is shown in Figure 4, where, T ^P _dqn-αβ and T ^N _dqn-αβ are transformation matrices from the harmonic positive sequence and harmonic negative sequence synchronous rotating coordinate system to the two-phase stationary coordinate system.

In the described frequency division harmonic control strategy, the delay compensation angle θ _n is composed of two parts, the digital control delay angle θ _nD and the analog sampling angle θ _nF , and the calculation formula is:

θ _nD = nω _g T _s

θ _nF = arctan(nω _s RC)

θ _n = θ _nFliter + θ _nD

Among them, T _s is the digital sampling period, n is the harmonic order, R and C are the resistance and capacitance of the analog low-pass filter, and ω _s is the cut-off frequency of the low-pass filter;

Transfer function by the VPI controller

It can be seen that, taking k _p ω _h =k _i sinθ _n , the controller is equivalent to the VPI controller, so the VPI control strategy based on TPSF is equivalent to the PI control strategy for compensation delay under MSRF. The wave current control loop shows that when the improved TPSF-based harmonic control strategy achieves the same control goal, the amount of digital resources required is greatly reduced. In fact, the VPI controller can actually be regarded as a PR controller with a first-order differential link, which improves the phase margin of the system to improve system stability and is more conducive to the compensation of high-order harmonics. The transfer function of the multi-synchronous rotating coordinate system harmonic current compensation strategy of the harmonic current controller with delay compensation is:

Among them, k _p and _ki are the proportional coefficient and integral coefficient of the nth harmonic current PI controller under the MSRF strategy, respectively.

In an exemplary embodiment of the present invention, as shown in Figure 5 is a single-phase equivalent circuit diagram of a parallel APF compensation voltage source nonlinear load, where e _sh is the grid voltage, Z _sh is the grid impedance, and Z _Lh is the load side AC impedance, Z _Loh is the equivalent input impedance of the voltage source nonlinear load, V _Loh is the equivalent power supply of the voltage source nonlinear load, λ is the harmonic current compensation rate, and I _c is the compensation current. Then the change relationship of load current I _Lh before and after compensation is:

In the formula, μ is the AC voltage change rate of the voltage source nonlinear load. It can be seen from the change relationship that, assuming that the impedance values of the system are constant and μ is constant, when λ increases, the current on the load side will increase; when λ and μ remain unchanged, increasing the load AC side impedance Z _Lh can suppress harmonics increase in current.

If the harmonic compensation rate is set to 100%, it will cause the amplitude of the specified sub-harmonic in the load and its adjacent harmonics to increase, and the increase of the adjacent load harmonics will cause the specified sub-harmonic amplitude of the load to increase. High, the two are coupled with each other, so the waveform of the specified sub-harmonic of the load will show low-frequency fluctuations.

The strategy adopted in this disclosure is to calculate the amplitude i _hnm of the load harmonic current and its rate of change di _hnm when the control command value of the specified sub-harmonic exceeds a certain threshold, and calculate the amplitude of the specified sub-harmonic current and the Its rate of change calculates the current harmonic current compensation rate. However, it is difficult to establish a definite mathematical relationship between the specified harmonic current amplitude and its change rate and the specified sub-harmonic current compensation rate in the model. Therefore, a method for calculating harmonic compensation rate based on a fuzzy controller is publicly proposed. The harmonic current amplitude is calculated by the following formula:

The rate of change of the harmonic current amplitude is calculated and determined according to dividing the currently calculated harmonic current amplitude by the harmonic current amplitude a preset number of sampling periods ago.

In order to avoid errors caused by sampling and other links, the obtained harmonic current amplitude is processed by a digital low-pass filter, and the harmonic current change rate is calculated by dividing the current calculated harmonic current amplitude by 20 sampling periods Input the calculated harmonic current amplitude and its rate of change into the fuzzy controller, and after processing by the fuzzy controller, the specified sub-harmonic current compensation rate can be obtained.

In an exemplary embodiment of the present invention, as shown in FIG. 6, the fuzzy subset distribution of harmonic compensation rate and its membership function diagram, the control system modeling step also includes:

The harmonic current amplitude is divided into three fuzzy subsets of different levels by specifying the sub-harmonic current amplitude 0.15 and 0.35 inflection points; the harmonic current amplitude i _hnm selects three fuzzy subsets: harmonic current amplitude Low (S), medium harmonic current amplitude (M), high harmonic current amplitude (L). Considering that the harmonic current compensation used in this paper is frequency division compensation, when designing the fuzzy subset membership function, it is considered that when the specified sub-harmonic current amplitude is higher than 0.35 (per unit value), the current current amplitude input value The maximum saturation is reached; and when the specified sub-harmonic current amplitude is lower than 0.15, it is considered that the current input value of the current amplitude has reached the minimum saturation.

The harmonic current amplitude change rate passes through the 5% step value inflection point to divide multiple fuzzy subsets of different levels. Harmonic current amplitude change rate di _hnm selects five fuzzy subsets: the load harmonic current amplitude drops quickly (DNL), the load harmonic current amplitude drops generally (DNS), and the load harmonic current amplitude basically does not Change (ZERO), load harmonic current amplitude increases generally (UPS), load harmonic current amplitude increases rapidly (UPL). Each inflection point of the membership function has a step of 5% (if it falls, take the reciprocal).

In an exemplary embodiment of the present invention, the control system modeling step further includes:

The harmonic current amplitude fuzzy subset and the harmonic current amplitude change rate fuzzy subset are defuzzified through the mamdani fuzzy model, and the area center of gravity method is selected to generate the harmonic current amplitude fuzzy subset and the harmonic current amplitude fuzzy subset. Please refer to Table 1 for the harmonic current compensation rate fuzzy rule table of the corresponding relationship between the value change rate and the harmonic current compensation rate.

Table 1 Fuzzy rule table of harmonic current compensation rate

In an exemplary embodiment of the present invention, as shown in Figure 5, the harmonic current compensation rate λ _n selects five fuzzy subsets: the harmonic current compensation rate is low (S), the harmonic current compensation rate is low (MS) , The harmonic current compensation rate is medium (M), the harmonic current compensation rate is medium high (ML), and the harmonic current compensation rate is high (L). In order not to make the harmonic compensation performance drop too much, the lowest harmonic compensation rate can be set to 80%.

In an exemplary embodiment of the present invention, when the harmonic current amplitude is substantially constant (ZERO), the output of the harmonic current compensation rate is higher; when the harmonic current amplitude is small, the output of the harmonic current compensation rate is The overall value is high; and when the harmonic current amplitude is large, the overall harmonic current compensation output is low. This is because when the harmonic current amplitude is large, harmonic current oscillation can easily cause system output overcurrent , causing the system to shut down.

With the help of the Fuzzy Logic Designer toolbox of MATLAB, the fuzzy controller can be conveniently designed. In this paper, the mamdani fuzzy model is used, and the area center of gravity method is selected to defuzzify. In order to reduce the difficulty of system development and save data processing resources, this paper uses the systemtest system test tool (supported below MATLAB 2015b) of MATLAB to conduct offline input and output tests on the fuzzy controller to establish an offline look-up table design. The final designed fuzzy data table is a 30×25 two-dimensional array, and the harmonic current compensation rate is obtained by querying the fuzzy table.

In the amplification effect suppression step S120, the parallel APF may be controlled according to the control system model to suppress the harmonic amplification effect of the parallel APF.

In the exemplary embodiment of the present invention, in order to verify the specific phenomenon of the harmonic amplification effect theory, the present disclosure builds a simulation model. The load is a three-phase symmetrical RC type six-pulse uncontrolled rectified current (voltage source type nonlinear load). In order to fully verify the harmonic amplification effect, the real grid impedance in the actual grid should not be ignored. The grid-side inductance set in the simulation model of this disclosure is 100 μH, and the load AC side has no inductance. The rest of the parameters can be referred to in Table 2.

Table 2 Electrical parameters of the main circuit

According to the data analysis of the simulation results, the 5th, 7th, and 11th grid voltage, load current, and grid current content of phase A before and after compensation are shown in Table 3.

Table 3 each harmonic content

For the convenience of calculation, the equivalent input impedance Z _Loh of the voltage source nonlinear load is 0, then the change relationship of the load current I _Lh before and after compensation can be simplified as:

Combining the above formula with Table 3, the theoretical and actual harmonic current amplification ratios of each order can be obtained as shown in Table 4:

Table 4 Harmonic compensation rate calculation example table

According to the example table of harmonic compensation rate shown in Table 4, it can be seen that the theoretically calculated harmonic amplification rate is almost consistent with the simulated actual harmonic amplification rate, which further verifies the correctness of the harmonic amplification effect theory.

It should be noted that although the steps of the method in the present disclosure are described in a specific order in the drawings, this does not require or imply that these steps must be performed in this specific order, or that all shown steps must be performed to achieve achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step for execution, and/or one step may be decomposed into multiple steps for execution, etc.

In addition, in this exemplary embodiment, a parallel APF harmonic amplification effect suppression system is also provided. Referring to Figure 7, the parallel APF harmonic amplification effect suppression system 700 may include a control system establishment module 710 and an amplification effect suppression module 720, wherein:

The control system building module 710 is used to generate a transfer function from the inverter output voltage to the grid-side current based on the two-level parallel APF main circuit topology, determine the system control loop according to the transfer function, and establish a control system model ; Wherein, determining the system control loop according to the transfer function includes: according to the vector proportional integral controller based on the two-phase stationary coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and adopting the harmonic current control based on the fuzzy controller The wave current compensation rate realizes the suppression of output current oscillation;

The amplification effect suppression module 720 is configured to control the parallel APF according to the control system model to suppress the harmonic amplification effect of the parallel APF.

The specific details of the above-mentioned control device modules of each FPGA-based power electronic converter have been described in detail in the corresponding parallel-connected APF harmonic amplification effect suppression method, so details will not be repeated here.

It should be noted that although several modules or units of the parallel-connected APF harmonic amplification effect suppression system are mentioned in the above detailed description, this division is not mandatory. Actually, according to the embodiment of the present disclosure, the features and functions of two or more modules or units described above may be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided to be embodied by a plurality of modules or units.

In addition, in an exemplary embodiment of the present disclosure, an electronic device capable of implementing the above method is also provided.

Those skilled in the art can understand that various aspects of the present invention can be implemented as systems, methods or program products. Therefore, various aspects of the present invention can be embodied in the following forms, that is: a complete hardware embodiment, a complete software embodiment (including firmware, microcode, etc.), or an embodiment combining hardware and software aspects, which can be collectively referred to herein as "circuit", "module" or "system".

Through the description of the above embodiments, those skilled in the art can easily understand that the exemplary embodiments described here can be implemented by software, or by combining software with necessary hardware. Therefore, the technical solutions according to the embodiments of the present disclosure can be embodied in the form of software products, and the software products can be stored in a non-volatile storage medium (which can be CD-ROM, U disk, mobile hard disk, etc.) or on the network , including several instructions to make a computing device (which may be a personal computer, a server, a terminal device, or a network device, etc.) execute the method according to the embodiment of the present disclosure.

In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present invention, and are not intended to be limiting. It is easy to understand that the processes shown in the above figures do not imply or limit the chronological order of these processes. In addition, it is also easy to understand that these processes may be executed synchronously or asynchronously in multiple modules, for example.

Other embodiments of the disclosure will be readily apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, and these modifications, uses or adaptations follow the general principles of the present disclosure and include common knowledge or conventional technical means in the technical field not disclosed in the present disclosure . The specification and examples are to be considered exemplary only, with the true scope and spirit of the disclosure indicated by the appended claims.

It should be understood that the present disclosure is not limited to the precise constructions which have been described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims (9)

1. A parallel active power filter APF harmonic amplification effect suppression method is characterized in that, the method comprises: The step of establishing the control system is to generate a transfer function from the inverter output voltage to the grid-side current based on the two-level parallel APF main circuit topology, determine the system control loop according to the transfer function, and establish a control system model; wherein, Determining the system control loop according to the transfer function includes: according to the vector proportional integral controller based on the two-phase stationary coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and using the harmonic current compensation determined based on the fuzzy controller rate to achieve output current oscillation suppression; The amplification effect suppression step is to control the parallel APF according to the control system model to suppress the harmonic amplification effect of the parallel APF. 2. The method according to claim 1, wherein the control system modeling step further comprises: The vector proportional integral controller of the two-phase static coordinate system is obtained based on the harmonic current controller with delay compensation added to the multi-synchronous rotating coordinate system harmonic current compensation strategy, and the open-loop transfer function of the harmonic current control is: After the harmonic current amplitude and the rate of change of the harmonic current amplitude are acquired, the harmonic current compensation rate is obtained by looking up a table in a preset harmonic current compensation rate fuzzy rule table. 3. The method of claim 1, wherein the control system modeling step further comprises: The two-level parallel APF main circuit topology AC filter is an LCLCLC filter, the damping strategy is a parallel connection of a grid-side inductor with a damping resistor, and the transfer function from the inverter output voltage to the grid-side current is in, L _g , L _o , C _f are the main filter, R _d is the damping resistor, which is the main output filter, L _x , C _x form the LC notch filter, which is used to filter out the switching frequency sub-ripple of the APF output, C _d is the supporting capacitance of the DC bus, e _a , e _b , e _c are the three-phase power supply voltages at the common coupling point, i _ga , i _gb , i _gc are the grid currents, i _la , i _lb , i _lc are the load currents , i _fa , i _fb , if _fc are the compensation current output by APF, u _dc is the DC bus voltage; The system control loop includes fundamental positive sequence current control based on fundamental positive sequence synchronous rotating coordinate system, vector proportional integral control based on two-phase stationary coordinate system, and harmonic compensation rate control based on fuzzy controller. 4. The method of claim 1, wherein the control system modeling step further comprises: In the described frequency division harmonic control strategy, the delay compensation angle θ _n is composed of two parts, the digital control delay angle θ _nD and the analog sampling angle θ _nF , and the calculation formula is: θ _nD = nω _g T _s θ _nF = arctan(nω _s RC) θ _n = θ _nFliter + θ _nD Among them, T _s is the digital sampling period, n is the harmonic order, R and C are the resistance and capacitance of the analog low-pass filter, and ω _s is the cut-off frequency of the low-pass filter; The transfer function of the multi-synchronous rotating coordinate system harmonic current compensation strategy of the harmonic current controller with delay compensation is: Among them, k _p and _ki are the proportional coefficient and integral coefficient of the nth harmonic current PI controller under the MSRF strategy, respectively. 5. The method according to claim 2, wherein the harmonic current amplitude is calculated by the following formula: The rate of change of the harmonic current amplitude is calculated and determined according to dividing the currently calculated harmonic current amplitude by the harmonic current amplitude a preset number of sampling periods ago. 6. The method according to claim 2 or 5, wherein the control system modeling step further comprises: The harmonic current amplitude is divided into multiple fuzzy subsets of different levels by specifying the sub-harmonic current amplitude 0.15 and 0.35 inflection points; The harmonic current amplitude change rate passes through the 5% step value inflection point to divide multiple fuzzy subsets of different levels. 7. The method of claim 1, wherein the control system modeling step further comprises: The harmonic current amplitude fuzzy subset and the harmonic current amplitude change rate fuzzy subset are defuzzified through the mamdani fuzzy model, and the area center of gravity method is selected to generate the harmonic current amplitude fuzzy subset and the harmonic current amplitude fuzzy subset. The harmonic current compensation rate fuzzy rule table of the corresponding relationship between the value change rate and the harmonic current compensation rate. 8. The method of claim 7, wherein the control system modeling step further comprises: The harmonic current compensation rate is not less than 80%. 9. A parallel type APF harmonic amplification effect suppression system is characterized in that the system comprises: The control system building module is used to generate a transfer function from the inverter output voltage to the grid side current based on the two-level parallel APF main circuit topology, determine the system control loop according to the transfer function, and establish a control system model; Wherein, determining the system control loop according to the transfer function includes: according to the vector proportional integral controller based on the two-phase stationary coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and using the harmonic current control determined based on the fuzzy controller The current compensation rate realizes the suppression of output current oscillation; The amplification effect suppression module is used to control the parallel APF according to the control system model, and suppress the harmonic amplification effect of the parallel APF.