CN110086173B - Parallel APF harmonic amplification effect suppression method and system - Google Patents
Parallel APF harmonic amplification effect suppression method and system Download PDFInfo
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- H—ELECTRICITY
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- H—ELECTRICITY
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- Y02E40/20—Active power filtering [APF]
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
Technical Field
The disclosure relates to the field of power electronics, in particular to a parallel APF harmonic amplification effect suppression method and system.
Background
An Active Power Filter (APF) is one of effective methods for suppressing Power grid harmonics, and has been widely studied in recent years. Because the loads put into the power grid have different characteristics, the treatment effect after the APF is put into the power grid is different, the parallel APF is suitable for compensating the current source type nonlinear load, and the series APF is suitable for compensating the voltage source type nonlinear load. Due to large loss and complex control mechanism, the series APF cannot be applied in a large scale; in contrast, the parallel APF has a more mature theory and technical research, and thus is applied to an industrial site on a large scale and is used to compensate a voltage source type nonlinear load. When the parallel APF compensates the voltage source type nonlinear load, the system has the characteristics of resonance and peak current overcurrent, namely, harmonic amplification effect, and the prior art generally adopts the following countermeasures: 1) a reactor with a certain inductance value is connected in series with the load alternating current side; 2) the harmonic compensation rate is reduced.
With the prior art 1), although the system resonance can be effectively reduced, the reactive power caused by the reactance is still compensated by the APF; for prior art 2), if the load varies, the originally set compensation rate may no longer be suitable.
From the foregoing, it would be desirable to provide one or more solutions that at least address the above-mentioned problems.
It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.
Disclosure of Invention
An object of the present disclosure is to provide a method and system for suppressing a harmonic amplification effect of a parallel-type APF, thereby overcoming, at least to some extent, one or more of the problems due to the limitations and disadvantages of the related art.
According to one aspect of the disclosure, a parallel-type APF harmonic amplification effect suppression method is provided, which includes:
a control system establishing step, namely generating a transfer function from the output voltage of the inverter to the current of the network side 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; wherein determining a system control loop according to the transfer function comprises: according to a vector proportional-integral controller based on a two-phase static coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and realizing output current oscillation suppression by adopting a harmonic current compensation rate determined based on a fuzzy controller;
and an amplification effect suppression step, controlling the parallel APF according to the control system model, and suppressing 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 stationary coordinate system is obtained by adding a delay compensation harmonic current controller in a harmonic current compensation strategy based on a multi-synchronous rotating coordinate system, and the open-loop transfer function of the harmonic current control is as follows:
and after obtaining the harmonic current amplitude and the change rate of the harmonic current amplitude, looking up a table in a preset harmonic current compensation rate fuzzy rule table to obtain the harmonic current compensation rate.
In an exemplary embodiment of the present disclosure, the control system modeling step further includes:
the two-level parallel APF main circuit topological structure alternating current filter is an LCLCLCLC filter, the damping strategy is a network side inductor parallel damping resistor, and the transfer function from the inverter output voltage to the network side current is
Wherein the content of the first and second substances,
Lg、Lo、Cfis a main filter, RdAs damping resistors, as main output filters, Lx、CxForming LC notch filter for filtering out switching frequency sub-ripple, C of APF outputdSupporting capacitors for DC bus lines, ea、eb、ecThree-phase supply voltage, i, being a point of common couplingga、igb、igcFor grid current, ila、ilb、ilcIs the load current ifa、ifb、ifcCompensation current, u, output for APFdcIs a dc bus voltage;
the system control loop comprises fundamental wave positive sequence current control based on a fundamental wave positive sequence synchronous rotating coordinate system, vector proportional integral control based on a two-phase static coordinate system and harmonic compensation rate control based on a fuzzy controller.
In an exemplary embodiment of the present disclosure, the control system modeling step further includes:
delay compensation angle theta in frequency division harmonic control strategynThe delay angle theta being controlled digitallynDAnd the analog sampling angle thetanFThe method comprises the following two parts, and the calculation formula is as follows:
θnD＝nωgTs
θnF＝arctan(nωsRC)
θn＝θnFliter+θnD
wherein, TsIs a digital sampling period, n is the harmonic frequency, R and C are respectively the resistance-capacitance of an analog low-pass filter, omegasIs the cut-off frequency of the low-pass filter;
the transfer function of the harmonic current compensation strategy of the multi-synchronous rotating coordinate system of the harmonic current controller added with the delay compensation is as follows:
wherein k isp、kiThe proportional coefficient and the integral coefficient of the n-th harmonic current PI controller under the MSRF strategy are respectively.
In an exemplary embodiment of the present disclosure, the harmonic current amplitude is calculated by the following formula:
and calculating and determining the change rate of the harmonic current amplitude according to the current calculated harmonic current amplitude divided by the harmonic current amplitudes before the preset number of sampling periods.
In an exemplary embodiment of the present disclosure, the control system modeling step further includes:
the harmonic current amplitude is divided into a plurality of fuzzy subsets of different levels by specifying inflection points of 0.15 and 0.35 of subharmonic current amplitude;
and dividing a plurality of fuzzy subsets of different levels by 5% step value inflection points according to the harmonic current amplitude change rate.
In an exemplary embodiment of the present disclosure, the control system modeling step further includes:
and the harmonic current amplitude fuzzy subset and the harmonic current amplitude change rate fuzzy subset are defuzzified by selecting an area gravity center method through a mamdani fuzzy model to generate a harmonic current compensation rate fuzzy rule table of the harmonic current amplitude fuzzy subset and the harmonic current amplitude change rate and harmonic current compensation rate corresponding relation.
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 establishing module is used for generating a transfer function from the output voltage of the inverter to the current on the network side based on the topological structure of the two-level parallel APF main circuit, determining a system control loop according to the transfer function and establishing a control system model; wherein determining a system control loop according to the transfer function comprises: according to a vector proportional-integral controller based on a two-phase static coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and realizing output current oscillation suppression by adopting a harmonic current compensation rate determined based on a fuzzy controller;
and the amplification effect suppression module is used for controlling the parallel APF according to the control system model and suppressing the harmonic amplification effect of the parallel APF.
The parallel APF harmonic amplification effect suppression method provided by the disclosure is characterized in that based on a two-level parallel APF main circuit topological structure, a transfer function from an inverter output voltage to a network side current is generated, a system control loop is determined according to the transfer function, and a control system model is established; and controlling the parallel APF according to the control system model to inhibit the harmonic amplification effect of the parallel APF. On one hand, the present disclosure provides a parallel APF composite current control strategy, which dynamically adjusts each subharmonic compensation rate through a fuzzy controller to balance system efficiency and system stability; on the other hand, the harmonic amplification effect is effectively inhibited by extracting and compensating each subharmonic through a VPI control strategy based on a static coordinate system.
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 disclosure.
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The above and other features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.
Fig. 1 shows a flow chart of a parallel-type APF harmonic amplification effect suppression method according to an exemplary embodiment of the present disclosure;
fig. 2 illustrates a diagram of a parallel-type APF main circuit topology according to an exemplary embodiment of the present disclosure;
FIG. 3 schematically illustrates a block diagram of an overall control of a parallel APF according to an exemplary embodiment of the present disclosure;
FIG. 4 schematically illustrates an improved MSRF harmonic compensation strategy control block diagram according to an exemplary embodiment of the present disclosure;
fig. 5 schematically illustrates a single-phase equivalent circuit diagram of a parallel-type APF compensated voltage source-type nonlinear load according to an exemplary embodiment of the present disclosure;
FIG. 6 schematically illustrates a harmonic compensation rate fuzzy subset distribution and its membership function graph according to an exemplary embodiment of the present disclosure;
fig. 7 illustrates a diagram of a parallel-type APF harmonic amplification effect suppression system according to an exemplary embodiment of the present disclosure.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different 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, a repetitive description thereof 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 to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the embodiments of the disclosure can be practiced without one or more of the specific details, or with other methods, components, materials, devices, steps, and so forth. 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 disclosure.
The block diagrams shown in the figures are functional entities only and do not necessarily correspond to physically separate entities. That is, these functional entities may be implemented in the form of software, or in one or more software-hardened modules, or in different networks and/or processor devices and/or microcontroller devices.
In the present exemplary embodiment, there is first provided a parallel-type APF harmonic amplification effect suppression method, which may include, as shown in fig. 1, the steps of:
a control system establishing step S110, based on a two-level parallel APF main circuit topological structure, generating a transfer function from the output voltage of the inverter to the network side current, determining a system control loop according to the transfer function, and establishing a control system model; wherein determining a system control loop according to the transfer function comprises: according to a vector proportional-integral controller based on a two-phase static coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and realizing output current oscillation suppression by adopting a harmonic current compensation rate determined based on a fuzzy controller;
and an amplification effect suppression step S120, controlling the parallel APF according to the control system model, and suppressing the harmonic amplification effect of the parallel APF.
According to the parallel APF harmonic amplification effect suppression method provided by the disclosure, on one hand, the disclosure provides a parallel APF composite current control strategy, and the harmonic compensation rate of each time is dynamically adjusted through a fuzzy controller so as to balance the system efficiency and the system stability; on the other hand, the harmonic amplification effect is effectively inhibited by extracting and compensating each subharmonic through a VPI control strategy based on a static coordinate system.
In the control system establishing step S110, a transfer function from the inverter output voltage to the grid-side current may be generated based on the two-level parallel APF main circuit topology, a system control loop is determined according to the transfer function, and a control system model is established; wherein determining a system control loop according to the transfer function comprises: and according to a vector proportional-integral controller based on a two-phase static coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and realizing output current oscillation suppression by adopting a harmonic current compensation rate determined based on a fuzzy controller.
In an exemplary embodiment of the invention, the control system modeling step further includes:
the vector proportional integral controller of the two-phase stationary coordinate system is obtained by adding a delay compensation harmonic current controller in a harmonic current compensation strategy based on a multi-synchronous rotating coordinate system, and the open-loop transfer function of the harmonic current control is as follows:
and after obtaining the harmonic current amplitude and the change rate of the harmonic current amplitude, looking up a table in a preset harmonic current compensation rate fuzzy rule table to obtain the harmonic current compensation rate.
In an exemplary embodiment of the invention, the control system modeling step further includes:
as shown in fig. 2, the structure diagram of the parallel-type APF main circuit topology is shown, the ac filter of the two-level parallel-type APF main circuit topology is an lclclclc filter, the damping strategy is a network-side inductor parallel damping resistor, and the transfer function from the inverter output voltage to the network-side current is
Wherein the content of the first and second substances,
Lg、Lo、Cfis a main filter, RdAs damping resistors, as main output filters, Lx、CxForming LC notch filter for filtering out switching frequency sub-ripple, C of APF outputdSupporting capacitors for DC bus lines, ea、eb、ecThree-phase supply voltage, i, being a point of common couplingga、igb、igcFor grid current, ila、ilb、ilcIs the load current ifa、ifb、ifcCompensation current, u, output for APFdcIs a dc bus voltage;
as shown in FIG. 3, the APF overall control block diagram is shown, ω g is the grid frequency, ed、eqFor the grid voltage in the fundamental positive sequence synchronous rotating coordinate system, ilα、ilβIs the load current in a two-phase stationary frame, ifα、ifβIs the output current u in a two-phase stationary coordinate systemHα_ref、uHβ_refIs a harmonic current command in a two-phase stationary coordinate system, ild、ilqIs a fundamental wave positive sequence synchronous rotationLoad current i in the frame of revolutionfd、ifqIs the output current u in the fundamental wave positive sequence synchronous rotating coordinate systemHd_ref、uHq_refIs a harmonic current instruction u under a fundamental wave positive sequence synchronous rotating coordinate systemdc_refFor given value of DC bus voltage iFd_refGiven value u of fundamental positive-sequence active current loopFd_ref、uFq_refOutputting the instruction u for the fundamental positive sequence current loopd_ref、uq_refFor integrated current command, λn(n-2, 3, …) is the compensation rate for a given subharmonic current, uHnα_ref、uHnβ_refFor a given subharmonic current command in a two-phase stationary coordinate system, i+ hnd、i+ hnqFor specifying the load current i in the sub-harmonic positive-sequence synchronous rotating coordinate system- hnd、i- hnqFor specifying the load current in the subharmonic negative-sequence synchronous rotating coordinate system, ihnmTo specify the subharmonic current amplitude, dihnmFor specifying the harmonic current amplitude conversion rate, the LPF is a digital Low Pass Filter (LPF); t isP αβ-dq1、TP dq1-αβIs a transformation matrix from a two-phase static coordinate system to a fundamental wave positive sequence synchronous rotating coordinate system and an inverse transformation matrix thereof, TP αβ-dqn、TN αβ-dqnIs a transformation matrix from a two-phase static coordinate system to a harmonic positive sequence and harmonic negative sequence synchronous rotating coordinate system, Tabc-αβIs a transformation matrix from a three-phase stationary coordinate system to a two-phase stationary coordinate system. In order to improve the phase-locking precision of the system, a double Second-order Generalized Integrator software phase-locked loop (DSPGI-PLL) is adopted; the PWM strategy is third harmonic injected SPWM.
The system control loop comprises fundamental wave positive sequence current control based on a fundamental wave positive sequence synchronous rotating coordinate system, vector proportional integral control based on a two-phase static coordinate system and harmonic compensation rate control based on a fuzzy controller.
In an exemplary embodiment of the invention, the control system modeling step further includes:
by using two phasesA Vector Proportional Integral (VPI) controller of a stationary Frame (TPSF) is used as the frequency-division harmonic control strategy. The strategy is based on an improved Multi-Synchronization rotation Reference Frame (MSRF) harmonic current compensation strategy equivalent simplification. Compared with the traditional MSRF strategy, the improved MSRF strategy has the advantages that the positive sequence component and the negative sequence component of each harmonic current are extracted and controlled, the compensation performance is improved, and the control block diagram is shown in FIG. 4, wherein TP dqn-αβ、TN dqn-αβThe transformation matrix is a transformation matrix from a harmonic positive sequence synchronous rotating coordinate system and a harmonic negative sequence synchronous rotating coordinate system to a two-phase static coordinate system.
Delay compensation angle theta in frequency division harmonic control strategynThe delay angle theta being controlled digitallynDAnd the analog sampling angle thetanFThe method comprises the following two parts, and the calculation formula is as follows:
θnD＝nωgTs
θnF＝arctan(nωsRC)
θn＝θnFliter+θnD
wherein, TsIs a digital sampling period, n is the harmonic frequency, R and C are respectively the resistance-capacitance of an analog low-pass filter, omegasIs the cut-off frequency of the low-pass filter;
transfer function by VPI controller
It can be known that k is takenpωh＝kisinθnThe controller is equivalent to a VPI controller, so the TPSF-based VPI control strategy is equivalent to a MSRF time delay compensation PI control strategy, and as can be seen from the harmonic current control loop in fig. 3, the amount of digital resources required by the improved TPSF-based harmonic control strategy is greatly reduced when the same control target is achieved. In fact, the VPI controller can be regarded as a PR controller with the addition of a first order differential element, improving the phase of the systemThe bit margin improves the stability of the system and is more beneficial to the compensation of higher harmonics. The transfer function of the harmonic current compensation strategy of the multi-synchronous rotating coordinate system of the harmonic current controller added with the delay compensation is as follows:
wherein k isp、kiThe proportional coefficient and the integral coefficient of the n-th harmonic current PI controller under the MSRF strategy are respectively.
In an exemplary embodiment of the present invention, fig. 5 is a single-phase equivalent circuit diagram of a parallel-type APF compensation voltage source-type nonlinear load, wherein eshFor the mains voltage, ZshAs impedance of the grid, ZLhIs the load side AC impedance, ZLohIs the equivalent input impedance, V, of a voltage source type nonlinear loadLohIs a voltage source type non-linear load equivalent power supply, and lambda is the harmonic current compensation rate, IcTo compensate for the current. Then the load current I before and after compensationLhThe change relationship is as follows:
in the formula, μ is a voltage source type nonlinear load alternating current voltage change rate. According to the change relation, assuming that each impedance value of the system is constant and mu is not changed, the current on the load side is increased when lambda is increased; when lambda and mu are not changed, the impedance Z of the load AC side is improvedLhThe increase of the harmonic current can be suppressed.
If the harmonic compensation rate is set to 100%, the amplitude of the designated subharmonic and the amplitude of the neighborhood harmonic in the load are increased, and the amplitude of the designated subharmonic in the load is increased due to the increase of the neighborhood load harmonic, and the designated subharmonic and the neighborhood load harmonic are coupled with each other, so that the waveform of the designated subharmonic in the load presents low-frequency fluctuation.
The strategy adopted by the disclosure is that when the control instruction value of the specified subharmonic exceeds a certain threshold value, the amplitude i of the subload harmonic current is calculatedhnmAnd rate of change thereof dihnmAnd calculating the current harmonic current compensation rate by specifying the amplitude of the subharmonic current and the change rate of the subharmonic current. And the specified harmonic current amplitude and the change rate thereof and the specified subharmonic current compensation rate are difficult to establish a definite mathematical relationship on a model for description, so that the harmonic compensation rate calculation method based on the fuzzy controller is disclosed. The harmonic current amplitude is calculated by the following formula:
and calculating and determining the change rate of the harmonic current amplitude according to the current calculated harmonic current amplitude divided by the harmonic current amplitudes before the preset number of sampling periods.
In order to avoid errors caused by links such as sampling, the obtained harmonic current amplitude is processed by a digital low-pass filter, the harmonic current change rate is obtained by dividing the currently calculated harmonic current amplitude by the harmonic current amplitude before 20 sampling periods, the calculated harmonic current amplitude and the calculated change rate are input into a fuzzy controller, and the specified subharmonic current compensation rate can be obtained after the harmonic current change rate is processed by the fuzzy controller.
In an exemplary embodiment of the present invention, as shown in fig. 6, which is a graph illustrating the distribution of the fuzzy subsets of the harmonic compensation rate and their membership functions, the step of modeling the control system further includes:
the harmonic current amplitude is divided into three fuzzy subsets with different levels by specifying inflection points of 0.15 and 0.35 of subharmonic current amplitude; amplitude of harmonic current ihnmThree fuzzy subsets are selected: harmonic current amplitude is low (S), harmonic current amplitude is medium (M), and harmonic current amplitude is high (L). Considering that the harmonic current compensation adopted herein is frequency division compensation, when designing the fuzzy subset membership function, it is considered that the current amplitude input value reaches maximum saturation when the specified subharmonic current amplitude is higher than 0.35 (per unit value); and when the specified subharmonic current magnitude is below 0.15, the current magnitude input value is deemed to be at minimum saturation.
The harmonic current amplitudeThe rate of change divides multiple fuzzy subsets at different levels by a 5% step value inflection point. Rate of change of harmonic current amplitude dihnmFive fuzzy subsets are selected: the load harmonic current amplitude falls down very fast (DNL), and load harmonic current amplitude falls down generally (DNS), and load harmonic current amplitude is unchangeable basically (ZERO), and load harmonic current amplitude increases generally (UPS), and load harmonic current amplitude increases very fast (UPL). Each inflection point of the membership function is stepped by 5% (the drop is the reciprocal).
In an exemplary embodiment of the 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 by selecting an area center of gravity method through a mamdani fuzzy model, and a harmonic current compensation rate fuzzy rule table of the harmonic current amplitude fuzzy subset and the harmonic current amplitude change rate and harmonic current compensation rate corresponding relation is generated, please refer to table 1.
TABLE 1 fuzzy rule table of harmonic current compensation rate
In an exemplary embodiment of the present invention, as shown in fig. 5, a harmonic current compensation rate λnFive fuzzy subsets are selected: 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 high (ML), and the harmonic current compensation rate is high (L). In order not to reduce the harmonic compensation performance too much, the harmonic compensation rate may be set to 80% at the lowest.
In an exemplary embodiment of the present invention, when the harmonic current amplitude is maintained substantially constant (ZERO), the harmonic current compensation rate output is made higher; when the amplitude of the harmonic current is small, the integral output of the harmonic current compensation rate is higher; when the amplitude of the harmonic current is large, the whole harmonic current compensation output is low, and the harmonic current oscillation easily causes the output overcurrent of the system when the amplitude of the harmonic current is large, so that the system is stopped.
A Fuzzy controller can be conveniently designed by means of a Fuzzy Logic Designer tool box of MATLAB, and a mamdani Fuzzy model is adopted to select an area gravity center method for defuzzification. In order to reduce the difficulty of system development and save data processing resources, a systemtest system test tool (supported below MATLAB 2015 b) carried by MATLAB is adopted to perform offline input and output tests on the fuzzy controller so as to establish an offline table look-up design. The finally designed fuzzy data table is a two-dimensional array of 30 multiplied by 25, and the harmonic current compensation rate is obtained by inquiring the fuzzy table.
In the amplification effect suppressing 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 invention, in order to verify the specific phenomenon of the harmonic amplification effect theory, the simulation model is set up in the disclosure. The load is three-phase symmetrical RC type six-pulse uncontrolled rectifying current (voltage source type nonlinear load). In order to fully verify the harmonic amplification effect and not ignore the power grid impedance actually existing in the actual power grid, the power grid side inductance set in the simulation model disclosed by the disclosure is 100 muH, the load alternating current side has no inductance, and the rest parameters can be referred to table 2.
TABLE 2 Main Circuit Electrical parameters
According to the data analysis of the simulation result, the grid voltage, the load current and the grid current content of 5, 7 and 11 times of the A phase before and after compensation are shown in table 3.
TABLE 3 content of harmonics
For simple calculation, the equivalent input impedance Z of the voltage source type nonlinear loadLohIs 0, the load current I before and after compensationLhThe variation relationship of (a) can be simplified as follows:
the theoretical and actual amplification ratios of the harmonic currents obtained by combining the above formula with table 3 are shown in table 4:
TABLE 4 harmonic compensation rate calculation table
According to the harmonic compensation rate calculation table shown in table 4, it can be known that the amplification rates of the harmonics of each order calculated theoretically are almost the same as the amplification rates of the simulated actual harmonics, and the correctness of the harmonic amplification effect theory is further verified.
It should be noted that although the various steps of the methods of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that these steps must be performed in this particular order, or that all of the depicted steps must be performed, to achieve desirable results. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions, etc.
In addition, in the present exemplary embodiment, a parallel-type APF harmonic amplification effect suppression system is also provided. Referring to fig. 7, the parallel APF harmonic suppression system 700 may include a control system establishing module 710 and an amplification effect suppression module 720, wherein:
the control system establishing module 710 is used for generating a transfer function from the output voltage of the inverter to the current on the network side based on the two-level parallel APF main circuit topological structure, determining a system control loop according to the transfer function, and establishing a control system model; wherein determining a system control loop according to the transfer function comprises: according to a vector proportional-integral controller based on a two-phase static coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and realizing output current oscillation suppression by adopting a harmonic current compensation rate determined based on a fuzzy controller;
and the amplification effect suppression module 720 is configured to control the parallel APF according to the control system model, and perform suppression of the harmonic amplification effect of the parallel APF.
The specific details of the control device module of each FPGA-based power electronic converter have been described in detail in the corresponding parallel APF harmonic amplification effect suppression method, and therefore are not described herein again.
It should be noted that although several modules or units of the parallel-type APF harmonic amplification effect suppression system are mentioned in the above detailed description, such division is not mandatory. Indeed, the features and functionality of two or more modules or units described above may be embodied in one module or unit, according to embodiments of the present disclosure. Conversely, the features and functions of one module or unit described above may be further divided into embodiments 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.
As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or program product. Thus, various aspects of the invention may be embodied in the form of: an entirely hardware embodiment, an entirely software embodiment (including firmware, microcode, etc.) or an embodiment combining hardware and software aspects that may all generally be referred to herein as a "circuit," module "or" system.
Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein may be implemented by software, or by software in combination with necessary hardware. Therefore, the technical solution according to the embodiments of the present disclosure may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, a usb disk, a removable hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which may be a personal computer, a server, a terminal device, or a network device, etc.) to execute the method according to the embodiments of the present disclosure.
Furthermore, the above-described figures are merely schematic illustrations of processes involved in methods according to exemplary embodiments of the invention, and are not intended to be limiting. It will be readily understood that the processes shown in the above figures are not intended to indicate or limit the chronological order of the processes. In addition, it is also readily understood that these processes may be performed synchronously or asynchronously, e.g., in multiple modules.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
It will be understood that the present disclosure is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is to be limited only by the terms of the appended claims.
Claims (8)
1. A method for suppressing APF harmonic amplification effect of a parallel active power filter is characterized by comprising the following steps:
a control system establishing step, namely generating a transfer function from the output voltage of the inverter to the current of the network side based on the main circuit topological structure of the two-level parallel active power filter, determining a system control loop according to the transfer function, and establishing a control system model; wherein determining a system control loop according to the transfer function comprises: according to a vector proportional-integral controller based on a two-phase static coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and realizing output current oscillation suppression by adopting a harmonic current compensation rate determined based on a fuzzy controller; the two-level parallel active power filter main circuit topological structure alternating current filter is an LCLCLCL filter, the damping strategy is a network side inductor parallel damping resistor, and the transfer function from the inverter output voltage to the network side current is
Wherein the content of the first and second substances,
Lg、Lo、Cfis a main filter, RdAs damping resistors, as main output filters, Lx、CxForming an LC notch filter for filtering the switching frequency sub-ripple output by the APF;
the system control loop comprises fundamental wave positive sequence current control based on a fundamental wave positive sequence synchronous rotating coordinate system, vector proportional integral control based on a two-phase static coordinate system and harmonic compensation rate control based on a fuzzy controller;
and an amplification effect suppression step, wherein the parallel active power filter is controlled according to the control system model to suppress the harmonic amplification effect of the parallel active power filter.
2. The method of claim 1, wherein the control system modeling step further comprises:
the vector proportional integral controller of the two-phase stationary coordinate system is obtained by adding a delay compensation harmonic current controller in a harmonic current compensation strategy based on a multi-synchronous rotating coordinate system, and the open-loop transfer function of the harmonic current control is as follows:
and after obtaining the harmonic current amplitude and the change rate of the harmonic current amplitude, looking up a table in a preset harmonic current compensation rate fuzzy rule table to obtain the harmonic current compensation rate.
3. The method of claim 1, wherein the control system modeling step further comprises:
delay compensation angle theta in frequency division harmonic control strategynThe delay angle theta being controlled digitallynDAnd the analog sampling angle thetanFThe method comprises the following two parts, and the calculation formula is as follows:
θnD＝nωgTs
θnF＝arc tan(nωsRC)
θn＝θnF+θnD
wherein, TsIs a digital sampling period, n is the harmonic frequency, R and C are respectively the resistance-capacitance of an analog low-pass filter, omegasIs the cut-off frequency of the low-pass filter;
the transfer function of the harmonic current compensation strategy of the multi-synchronous rotating coordinate system of the harmonic current controller added with the delay compensation is as follows:
wherein k isp、kiThe proportional coefficient and the integral coefficient of the n-th harmonic current PI controller under the MSRF strategy are respectively.
4. The method of claim 2, wherein the harmonic current magnitude is calculated by the formula:
wherein i+ hnd、i+ hnqPositive sequence for a given subharmonicLoad current in a synchronous rotating coordinate system, i- hnd、i- hnqLoad current under a specified subharmonic negative sequence synchronous rotation coordinate system;
and calculating and determining the change rate of the harmonic current amplitude according to the current calculated harmonic current amplitude divided by the harmonic current amplitudes before the preset number of sampling periods.
5. The method of claim 2 or 4, wherein the control system modeling step further comprises:
the harmonic current amplitude is divided into three fuzzy subsets with different levels by specifying inflection points of 0.15 and 0.35 of subharmonic current amplitude;
and dividing a plurality of fuzzy subsets of different levels by 5% step value inflection points according to the harmonic current amplitude change rate.
6. The method of claim 1, wherein the control system modeling step further comprises:
and the harmonic current amplitude fuzzy subset and the harmonic current amplitude change rate fuzzy subset are defuzzified by selecting an area gravity center method through a mamdani fuzzy model to generate a harmonic current compensation rate fuzzy rule table of the harmonic current amplitude fuzzy subset and the harmonic current amplitude change rate and harmonic current compensation rate corresponding relation.
7. The method of claim 6, wherein the control system modeling step further comprises:
the harmonic current compensation rate is not less than 80%.
8. A parallel active power filter APF harmonic amplification effect suppression system, the system comprising:
the control system establishing module is used for generating a transfer function from the output voltage of the inverter to the current on the network side based on the main circuit topological structure of the two-level parallel active power filter, determining a system control loop according to the transfer function and establishing a control system model; wherein determining a system control loop according to the transfer function comprises: according to a vector proportional-integral controller based on a two-phase static coordinate system, performing harmonic current control as a frequency division harmonic control strategy, and realizing output current oscillation suppression by adopting a harmonic current compensation rate determined based on a fuzzy controller; the two-level parallel active power filter main circuit topological structure alternating current filter is an LCLCLCL filter, the damping strategy is a network side inductor parallel damping resistor, and the transfer function from the inverter output voltage to the network side current is
Wherein the content of the first and second substances,
Lg、Lo、Cfis a main filter, RdAs damping resistors, as main output filters, Lx、CxForming an LC notch filter for filtering the switching frequency sub-ripple output by the APF;
the system control loop comprises fundamental wave positive sequence current control based on a fundamental wave positive sequence synchronous rotating coordinate system, vector proportional integral control based on a two-phase static coordinate system and harmonic compensation rate control based on a fuzzy controller;
and the amplification effect suppression module is used for controlling the parallel active power filter according to the control system model and suppressing the harmonic amplification effect of the parallel active power filter.
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| CN113013873A (en) * | 2021-02-26 | 2021-06-22 | 云南电网有限责任公司保山供电局 | Novel power grid phase-locked loop self-adaptive compensation method and compensation system |
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