CN114256846A - Adaptive impedance coupling series injection type active power filter and control method - Google Patents

Adaptive impedance coupling series injection type active power filter and control method Download PDF

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CN114256846A
CN114256846A CN202111516844.8A CN202111516844A CN114256846A CN 114256846 A CN114256846 A CN 114256846A CN 202111516844 A CN202111516844 A CN 202111516844A CN 114256846 A CN114256846 A CN 114256846A
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adaptive impedance
branch
inverter
load
active
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CN114256846B (en
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王雷
张凯
吕源
何志兴
徐千鸣
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Hunan University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/20—Active power filtering [APF]

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  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Control Of Electrical Variables (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a self-adaptive impedance coupling series injection type active power filter and a control method, wherein the self-adaptive impedance coupling series injection type active power filter comprises the following components: the active inverter is connected with the self-adaptive impedance branch and the fundamental frequency resonance branch; one end of the self-adaptive impedance branch is connected with a power grid, and the other end of the self-adaptive impedance branch is connected with the active inverter and the fundamental wave resonance branch; one end of the fundamental frequency resonance branch is in three-phase star connection, and the other end of the fundamental frequency resonance branch is connected with the active inverter and the adaptive impedance branch. The invention realizes the compensation of the load wide-range reactive power by controlling the trigger angle of the anti-parallel thyristor of the adaptive impedance branch; the voltage at the alternating current side of the inverter is reduced through the fundamental frequency resonance circuit, and the capacity requirement of the inverter is reduced; the suppression of the load harmonic current is realized through an active inverter. The invention can realize the consideration of wide reactive compensation range and low inverter capacity.

Description

Adaptive impedance coupling series injection type active power filter and control method
Technical Field
The invention relates to the technical field of current transformation in electrical engineering, in particular to a self-adaptive impedance coupling series injection type active power filter and a control method.
Background
With the development and popularity of power electronics and motors, such as: frequency converters, servo drives, large air conditioning systems, compressors, etc., the problem of power quality in the power grid becomes more and more serious, especially with low power factor and harmonic pollution. The power quality problem not only increases the transmission loss in the power grid, but also reduces the reliability and safety of the electronic equipment, and influences the service life.
The active filter (APF), the static synchronous regulation and control system (DSTATCOM) and the unified power quality regulator (UPQC) have the functions of eliminating power grid harmonic waves, compensating load reactive power and the like, and have excellent performance. Although the compensation range is wider, the inverter needs to bear fundamental wave voltage, so that the voltage-resistant grade requirement of the device is high, the capacity requirement of the inverter is high, the reliability of equipment is reduced, and the product cost is increased. The hybrid regulation and control system is composed of a passive capacitive impedance and an active inverter, the capacity and the voltage-resistant grade of devices of the inverter are effectively reduced by using the low-cost capacitive impedance, and the operation cost is reduced. However, the capacitive impedance greatly limits the application range of the hybrid regulation and control system, and produces a contradiction that the capacity of the inverter and the wide-range reactive power regulation cannot be considered at the same time. Therefore, the research on the low-cost and wide-compensation-range power quality adjusting device has important practical significance.
In recent years, the patent applications of the invention in the field of power quality governance are compared as follows: "a method for improving the quality of electric energy by using an active power filter" (publication No. CN112769137A, publication No. 2021, 05, month, and 07), "an APF and TSF hybrid compensation device for an electric drilling machine" (publication No. CN102593848A, publication No. 2012, month, and 18), which can reduce the requirement for inverter capacity, but can only compensate for the reactive power of fixed capacity, and cannot compensate for the reactive power in a wide range. The harmonic and reactive dynamic comprehensive compensation system based on the APF and the SVC and the frequency division split-phase current control method thereof (publication number: CN101202448A, published: 2008, 06, 18) can realize the reduction of the capacity requirement of the inverter and the wide-range reactive compensation, but need the active inverter to restrain the harmonic generated by the Thyristor Controlled Reactor (TCR).
Disclosure of Invention
The invention aims to solve the technical problem that aiming at the defects of the prior art, the invention provides the adaptive impedance coupling series injection type active power filter and the control method thereof, which solve the problem that the low-capacity and wide-range reactive power regulation of the inverter can not be considered simultaneously on the premise of not needing the active inverter to suppress the harmonic waves generated by the TCR, and realize the harmonic suppression and wide-range reactive power compensation functions of the low-capacity inverter.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a self-adaptive impedance coupling series injection type active power filter comprises an active inverter, three self-adaptive impedance branches and three fundamental frequency resonance branches; the adaptive impedance branch comprises a capacitor, an inductor and an anti-parallel thyristor; the inductor is connected with the anti-parallel thyristor in series, and the series branch is connected with the capacitor in parallel; the input end of each self-adaptive impedance branch is connected between a power grid and a load in parallel, and the output end of each self-adaptive impedance branch is correspondingly connected with an active inverter and a fundamental wave resonance branch; one end of each of the three fundamental resonance branches is in three-phase star connection;
the trigger angle alpha of the anti-parallel thyristorxAnd the adaptive impedance branch circuit compensates the reactive power QcxThe relationship of (1) is:
Figure BDA0003407150300000021
wherein, VxIs the root mean square value of the phase voltage, XCAIB、XLAIBAre respectively CAIB、LAIBFundamental wave reactance, CAIB、LAIBRespectively a capacitance value and an inductance value of the adaptive impedance branch; x is a,b. c, a, b and c are three phases of the active power filter;
the fundamental frequency resonance branch comprises a resonance capacitor and a resonance inductor which are connected in series.
The invention is provided with an adaptive impedance branch, the main function of which is to control the trigger angle alphaxThe reactive power of the load is compensated, the harmonic generated by the adaptive impedance branch is not required to be inhibited by the active inverter in the process, and the wide-range reactive power compensation of the load is realized by controlling the trigger angle of the anti-parallel thyristor of the adaptive impedance branch; the voltage at the alternating current side of the inverter is reduced through the fundamental frequency resonance circuit, and the capacity requirement of the inverter is reduced, namely the harmonic suppression and the wide-range reactive compensation of the low-capacity inverter are realized, and the problem that the low-capacity and wide-range reactive regulation of the inverter cannot be considered at the same time is solved.
In the invention, the active inverter comprises a three-phase full-bridge inverter, and the midpoint of each bridge arm of the three-phase full-bridge inverter is connected with a filter inductor; each filter inductor is connected with the output end of the corresponding adaptive impedance branch circuit. The active inverter can realize the suppression of the load harmonic current.
The capacitance value C of the adaptive impedance branchAIBAnd inductance value LAIBThe calculation formula of (a) is as follows:
Figure BDA0003407150300000022
Figure BDA0003407150300000023
wherein, ω is0At the fundamental angular frequency, QLx_maxFor maximum reactive power, Q, of the loadLx_minIs the load reactive power minimum. The capacitance value and the inductance value of the self-adaptive impedance branch obtained by calculation through the formula can realize the pair [ Q ]Lx_min,QLx_max]Compensation of reactive power over a wide range.
The fundamental frequency resonance branch comprises resonance capacitors connected in seriesAnd a resonant inductance; the resonant capacitor C1And a resonant inductor L1Satisfies the following conditions:
Figure BDA0003407150300000031
the active inverter does not bear fundamental voltage through the fundamental frequency resonance branch circuit, and the capacity requirement of the inverter is effectively reduced.
The adaptive impedance branch control process comprises: according to the trigger angle alpha of the anti-parallel thyristorxCompensating reactive power Q with adaptive impedance branchcxEstablishing a corresponding lookup table; based on the lookup table, triggering the angle alpha by controlling the antiparallel thyristors according to the load reactive powerxAnd compensating the reactive power of the load. Thyristor trigger angle alpha is conveniently obtained by looking up tablexRealizing the self-adaptive impedance branch compensation reactive power Qcx。
In the invention, the control process of the anti-parallel thyristor comprises the following steps: comparing phase voltage phase angles thetaxAnd alphaxWhen theta isx>αxFirst thyristor T in time output anti-parallel thyristor1xThe trigger signal of (1); when theta isx>180°+αxTime output anti-parallel thyristor type second thyristor T2xThe trigger signal of (1). According to phase voltage phase angle thetaxWith a triggering angle alphaxThe trigger signal of the anti-parallel thyristor is obtained, and the control process is simple.
The relation between the compensation reactive power of the self-adaptive impedance branch and the load reactive power is as follows:
Figure BDA0003407150300000032
Figure BDA0003407150300000033
is the load reactive power. According to load reactive power
Figure BDA0003407150300000034
Obtaining adaptive impedance branch compensation power QcxSo as to realize effective compensation of the reactive power of the load.
As an inventive concept, the present invention also provides a control method of the active power filter, which includes the steps of:
s1, extracting load harmonic current
Figure BDA0003407150300000035
Make the active inverter output a current reference value
Figure BDA0003407150300000036
S2, outputting a current reference value i by the active invertercx_refAnd the output current i of the active invertercxAfter comparison, the difference value is connected with the PR controllers in parallel for 5 times, 7 times, 11 times and 13 times to obtain a modulation wave signal of the active power inverter;
s3, obtaining an active inverter switching device trigger signal through pulse width modulation;
wherein the parallel PR controller transfer function is:
Figure BDA0003407150300000037
kpis a proportionality coefficient, krIs the resonance coefficient, omegacIs the cut-off frequency.
By the control method, 5 th, 7 th, 11 th and 13 th effective suppression of the main components of the load harmonic current is realized.
In step S1, the load harmonic current is extracted
Figure BDA0003407150300000038
The specific implementation process comprises the following steps: will load current iLxAnd a component i in the fundamental frequency rotation coordinate system obtained by park transformationLd、iLqExtracting the DC component by a low-pass filter
Figure BDA0003407150300000039
Further obtaining AC component
Figure BDA0003407150300000041
Load harmonic current is obtained through park inverse transformation
Figure BDA0003407150300000042
The load harmonic current can be effectively obtained by extracting the alternating current component under the fundamental frequency rotating coordinate system, so that the effective suppression of the load harmonic current is realized.
As an inventive concept, the present invention also provides a computer arrangement comprising a memory, a processor and a computer program stored on the memory; characterized in that the processor executes the computer program to realize the steps of the control method of the present invention.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention realizes the wide-range reactive power compensation of the load by controlling the triggering angle of the anti-parallel thyristor of the adaptive impedance branch;
2. the voltage on the alternating current side of the inverter is reduced through the fundamental frequency resonance circuit, and the capacity requirement of the inverter is reduced. Compared with the existing electric energy quality control device, the invention can give consideration to both wide reactive compensation range and low inverter capacity, does not need an active inverter to inhibit harmonic waves generated by the adaptive impedance branch, and has simple realization process and reliable control.
Drawings
Fig. 1 is a diagram of an adaptive impedance-coupled series injection active power filter according to the present invention;
fig. 2 is a control block diagram of an adaptive impedance-coupled series injection active power filter according to the present invention;
FIG. 3 shows the voltage and grid current at the Point of Common Coupling (PCC), the voltage and load current at the PCC, the reactive power at the grid side and the reactive power at the load side after the present invention is utilized to perform power quality control;
fig. 4 shows the internal current of the adaptive impedance branch and the current of the injection branch when the reactive power compensation is performed by using the present invention.
Detailed Description
As shown in fig. 1 and fig. 2, the adaptive impedance-coupled series injection active power filter according to the embodiment of the present invention includes an active inverter, an adaptive impedance branch, a first injection circuit, a second injection circuit, a third injection circuit, a fourth injection circuit, a fifth injection circuit, a sixth injection circuit, a fourth injection circuit, a fifth injection circuit, a sixth injection circuit, a fourth injection circuit, a sixth injection circuit, a fourth injection circuit, a fifth, a sixth injection circuit, a fourth circuit, a fifth circuit, a sixth circuit, a fifth circuit, a sixth circuit, a fifth circuit, a fourth circuit, a sixth circuit, a fifth circuit, a sixth circuit, a fifth circuit,a fundamental frequency resonance branch and a control system. The active inverter comprises a three-phase full bridge and a filter inductor. The inverter part comprises a fully-controlled power electronic device Txu，Txl(IGBT or MOSFET). The adaptive impedance branch comprises a capacitor CAIBInductor LAIBAnd anti-parallel thyristor T1x、T2xInductance LAIBWith anti-parallel thyristors T1x、T2xIn series with a capacitor CAIBAnd (4) connecting in parallel. The anti-parallel thyristors are alternately turned on by changing the firing angle alphaxSo as to change the time length of the on and off of the reactive compensation device, thereby changing the input reactance value and carrying out wide-range reactive compensation. The fundamental resonance branch comprises a capacitor C1And an inductance L1Capacitor C1And an inductance L1The fundamental frequency resonance branch enables the inverter part not to bear the fundamental frequency voltage of the power grid, thereby effectively reducing the capacity of the inverter, the voltage-resistant grade of devices and the operation cost.
The active inverter comprises a three-phase full bridge and a filter inductor LfThe three-phase full bridge comprises three parallel bridge arms, and each bridge arm comprises two power devices connected in series. The power device is a fully-controlled power electronic device. Filter inductance LfOne end of the three-phase full bridge is connected with the three-phase full bridge, and the other end of the three-phase full bridge is connected with the self-adaptive impedance branch and the fundamental frequency resonance branch.
In the invention, the three adaptive impedance branches have the same structure, and the first adaptive impedance branch comprises a capacitor CAIBInductor LAIBAnd anti-parallel thyristor T1x(x＝a、b、c)、T2xInductance LAIBWith anti-parallel thyristors T1x、T2xIn series with a capacitor CAIBThe self-adaptive impedance branch is formed by connecting in parallel, one end of the self-adaptive impedance branch is connected with a power grid, and the other end of the self-adaptive impedance branch is connected with a filter inductor L of the active inverterfAnd a fundamental resonant branch.
In the invention, the three fundamental frequency resonance branches have the same structure, and the first fundamental frequency resonance branch is provided with a capacitor C1And an inductance L1Are connected in series to form1And L1Satisfy the requirement of
Figure BDA0003407150300000051
One end of the fundamental wave resonance branch is connected with a three-phase star type, and the other end is connected with a filter inductor L of the active inverterSAnd an adaptive impedance branch. The capacitance and the inductance of the second fundamental frequency resonance branch and the third fundamental frequency resonance branch both satisfy the relational expression.
(1) Adaptive impedance branch circuit element parameter design
When a pair of thyristors T of each phase1x、T2xWhen turned off simultaneously (alpha) over the entire fundamental frequency periodx180 degree, the adaptive impedance branch is equivalent to a capacitor CAIB. In this case, the adaptive impedance branch compensates the power Qcx(180 °) the maximum reactive power of the load can be compensated. On the other hand, when a pair of thyristors T of each phase1x、T2xAlternately closed (alpha) in one fundamental frequency period with the length of each half periodx90 deg., the adaptive impedance branch is equivalent to an inductor LAIBAnd a capacitor CAIBIn a parallel combination of (a). In this case, the adaptive impedance branch compensates the power Qcx(90 °) may compensate for the minimum load reactive power. Qcx(180 ℃) and Qcx(90 °) may be expressed as:
Figure BDA0003407150300000052
Figure BDA0003407150300000053
the relation between the maximum and minimum reactive power of the load and the compensation power of the adaptive impedance branch circuit is QLx_max＝-Qcx(180°)、QLx_min＝-Qcx(90°)From the compensated reactive power range, C can be obtainedAIBAnd LAIB：
Figure BDA0003407150300000054
Figure BDA0003407150300000055
(2) Adaptive impedance branch control method
As shown in fig. 2, the main function of the adaptive impedance branch is based on controlling the trigger angle αxAnd compensating the reactive power of the load. Capacitance C according to designAIBAnd an inductance LAIBTo obtain a trigger angle alphaxCompensating reactive power Q with adaptive impedance branchcxThe relationship of (1):
Figure BDA0003407150300000061
according to the trigger angle alpha of the anti-parallel thyristorxCompensating reactive power Q with adaptive impedance branchcxThe corresponding look-up table is built up as shown in table 1. Based on the lookup table, according to the calculated load reactive power, triggering the angle alpha by controlling the antiparallel thyristorsxAnd compensating the reactive power of the load. Comparing phase voltage phase angles thetaxAnd alphaxWhen theta isx>αxTime-output thyristor T therein1xThe trigger signal of (1); when theta isx>180°+αxTime-output thyristor T therein2xThe trigger signal of (1).
TABLE 1 trigger Angle αxLookup table
Qcx αx
Qcx0≤Qcx<Qcx1 αx＝α1＝90°
Qcx1≤Qcx<Qcx2 αx＝α2
…… ……
Qcxn-2≤Qcx<Qcxn-1 αx＝αn-1
Qcxn-1≤Qcx<Qcxn αx＝αn＝180°
Trigger angle alphaxThe value of the interval and the corresponding reactive power range is set according to the actual situation, for example, when CAIB＝200μF、LAIBWhen 25mH, Q can be selectedcx0＝9.313kVar、Qcx1＝9.272kVar、Qcx2＝9.231kVar、Qcxn-2＝-9.032kVar、Qcxn-1＝-9.068kVar、Qcxn＝-9.073kVar，α2＝90.1°、αn-1＝175°。
Adaptive impedance branch compensation reactive power QcxThe relationship with the load reactive power is:
Figure BDA0003407150300000062
wherein the content of the first and second substances,
Figure BDA0003407150300000063
for instantaneous reactive power q of the loadLxA direct current component obtained by a low-pass filter. q. q.sLxComprises the following steps:
Figure BDA0003407150300000064
vxis the PCC point voltage, iLxIn order to be the load current,
Figure BDA0003407150300000065
are each vx、iLxThe phase shift is 90 degrees.
(3) Active inverter control method
Control of the active inverter, as shown in fig. 2:
first, the harmonic component of the load current is extracted
Figure BDA0003407150300000066
Will load current iLxObtaining a component i under a fundamental frequency rotation coordinate system through park transformationLd、iLqExtracting the DC component by a low-pass filter
Figure BDA0003407150300000067
Further obtaining AC component
Figure BDA0003407150300000068
Figure BDA0003407150300000069
Load harmonic current is obtained through park inverse transformation
Figure BDA00034071503000000610
Further obtaining the output current reference value of the active inverter
Figure BDA00034071503000000611
And then the compensation of the load harmonic current is realized through the control of the output current of the active inverter. Outputting a current reference value i by an active invertercx_refAnd the inverter output current icxAfter comparison, the difference value passes through the parallel PR controllers for 5 times, 7 times, 11 times and 13 times to obtain a modulation wave signal of the active inverter.
The parallel PR controller transfer function is:
Figure BDA0003407150300000071
and finally obtaining a trigger signal of the switching device of the active inverter through Pulse Width Modulation (PWM).
The following is to verify that the invention can effectively realize the harmonic suppression and wide-range reactive compensation functions of the low-capacity inverter.
System parameters:
system line voltage US380V, 50Hz of system frequency f and L of power grid impedanceS＝0.2mH；
Adaptive impedance branch parameters:
capacitor CAIB200 muF, inductance LAIB＝25mH；
Active inverter parameters:
DC voltage Udc100V, filter inductance Lf＝2mH；
Fundamental frequency resonance branch parameters:
capacitor C1350 muF, inductance L1＝28.95mH；
Nonlinear load parameters:
resistance R nL60 Ω, inductance LnL＝35mH；
Linear load 1 parameters:
resistance R L112 Ω, capacitance CL1＝338μF；
Linear load 2 parameters:
resistance R L212 Ω, inductance LL2＝30mH。
The simulation results for the above parameters are as follows:
fig. 3 is a simulation result after power quality control is performed by using the present invention, where the linear load before 0.1s is linear load 1, and the linear load after 0.1s is linear load 2. Fig. 3 shows PCC point voltage and grid current, PCC point voltage and load current, grid-side reactive power, and load-side reactive power, respectively. As can be seen from the waveforms of the PCC point voltage and the load current, the load current leads the voltage due to the existence of capacitive reactive power at the front load side of 0.1 s; the load current lags behind the voltage due to the presence of inductive reactive power on the load side after 0.1 s. The reactive power of the load side contains a large amount of reactive power, and the reactive power of the load side is-5.7 kVar before 0.1 s; the reactive power at the load side after 0.1s is 6 kVar. Due to the existence of the nonlinear load, the ABC three-phase load current harmonic distortion rates before 0.1s are respectively 10.16%, 10.14% and 10.16%; after 0.1s, the harmonic distortion rates of the ABC three-phase load current are respectively 9.92%, 9.91% and 9.93%. After the adaptive impedance coupling series injection type active power filter is put into operation, the voltage of a PCC point and the current of a power grid are adjusted to the same phase, the reactive power on the power grid side is close to 0, and the harmonic distortion rates of the ABC three-phase power grid current before 0.1s are respectively 2.89%, 2.91% and 2.98%; after 0.1s, the ABC three-phase power grid current harmonic distortion rates are respectively 2.69%, 2.75% and 2.78%.
To verify that the active inverter does not need to suppress the harmonics generated by the adaptive impedance branch, fig. 4 shows the internal current i of the adaptive impedance branch when only reactive compensation is performedLAIBxAnd injecting a branch current iix. The linear load before 0.1s is linear load 1, and the linear load after 0.1s is linear load 2. Before 0.1s, the internal current harmonic distortion rates of the ABC three-phase adaptive impedance branch circuit are respectively 12.01%, 12% and 12.01%; after 0.1s, the harmonic distortion rates of the internal current of the ABC three-phase adaptive impedance branch are 65.83%, 65.84% and 65.81% respectively. Before 0.1s, the harmonic distortion rates of the ABC three-phase injection branch circuit current are 1.14%, 1.14% and 1.14% respectively; after 0.1s, the harmonic distortion rates of the ABC three-phase injection branch circuit currents are 1.56%, 0.91% and 1.47% respectively. It can be seen that in the present invention, the harmonic current of the adaptive impedance branch does not flow into the injection branch, and the active inverter is not required to suppress the harmonic current.
The simulation results verify that the adaptive impedance coupling series injection type active power filter and the control method thereof can give consideration to both wide-range reactive compensation and low inverter capacity.

Claims (10)

1. A self-adaptive impedance coupling series injection type active power filter is characterized by comprising an active inverter, three self-adaptive impedance branches and three fundamental frequency resonance branches; the adaptive impedance branch comprises a capacitor, an inductor and an anti-parallel thyristor; the inductor is connected with the anti-parallel thyristor in series, and the series branch is connected with the capacitor in parallel; the input end of each self-adaptive impedance branch is connected between a power grid and a load in parallel, and the output end of each self-adaptive impedance branch is correspondingly connected with an active inverter and a fundamental wave resonance branch; one end of each of the three fundamental resonance branches is in three-phase star connection;
the trigger angle alpha of the anti-parallel thyristorxAnd the adaptive impedance branch circuit compensates the reactive power QcxThe relationship of (1) is:
Figure FDA0003407150290000011
wherein, VxIs the root mean square value of the phase voltage, XCAIB、XLAIBAre respectively CAIB、LAIBFundamental wave reactance, CAIB、LAIBRespectively a capacitance value and an inductance value of the adaptive impedance branch; x is a, b and c, and a, b and c are three phases of the active power filter;
the fundamental frequency resonance branch comprises a resonance capacitor and a resonance inductor which are connected in series.
2. The adaptive impedance-coupled series injection active power filter of claim 1, wherein the active inverter comprises a three-phase full-bridge inverter, wherein a filter inductor is connected to a midpoint of each leg of the three-phase full-bridge inverter; each filter inductor is connected with the output end of the corresponding adaptive impedance branch circuit.
3. The adaptive impedance-coupled series injection active power filter of claim 1, wherein the adaptive impedance branch capacitance value CAIBAnd inductance value LAIBThe calculation formula of (a) is as follows:
Figure FDA0003407150290000012
Figure FDA0003407150290000013
wherein, ω is0At the fundamental angular frequency, QLx_maxFor maximum reactive power, Q, of the loadLx_minIs the load reactive power minimum.
4. The adaptive impedance-coupled series injection active power filter of claim 1, wherein a resonant capacitance C in the fundamental resonant branch1And a resonant inductor L1Satisfies the following conditions:
Figure FDA0003407150290000014
5. the adaptive impedance-coupled series injection active power filter of claim 1, wherein the adaptive impedance branch control process comprises: according to the trigger angle alpha of the anti-parallel thyristorxCompensating reactive power Q with adaptive impedance branchcxEstablishing a corresponding lookup table; based on the lookup table, triggering the angle alpha by controlling the antiparallel thyristors according to the load reactive powerxAnd compensating the reactive power of the load.
6. The adaptive impedance-coupled series injection active power filter of claim 1, wherein the control process for the anti-parallel thyristors comprises: comparing phase voltage phase angles thetaxAnd alphaxWhen theta isx>αxFirst thyristor T in time output anti-parallel thyristor1xThe trigger signal of (1); when theta isx>180°+αxTime output anti-parallel thyristor in second thyristor T2xThe trigger signal of (1).
7. The adaptation of claim 1The reactive impedance coupling series injection type active power filter is characterized in that the relation between the compensation reactive power of the self-adaptive impedance branch circuit and the load reactive power is as follows:
Figure FDA0003407150290000021
Figure FDA0003407150290000022
is the load reactive power.
8. A method for controlling an active power filter according to any one of claims 1 to 7, comprising the steps of:
s1, extracting load harmonic current
Figure FDA0003407150290000023
Make the active inverter output a current reference value
Figure FDA0003407150290000024
S2, outputting a current reference value i by the active invertercx_refAnd the output current i of the active invertercxAfter comparison, the difference value is connected with the PR controllers in parallel for 5 times, 7 times, 11 times and 13 times to obtain a modulation wave signal of the active inverter;
s3, obtaining an active inverter switching device trigger signal through pulse width modulation;
wherein the parallel PR controller transfer function is:
Figure FDA0003407150290000025
kpis a proportionality coefficient, krIs the resonance coefficient, omegacIs the cut-off frequency.
9. The control method according to claim 8, wherein in step S1, the load harmonic current is extracted
Figure FDA0003407150290000026
The specific implementation process comprises the following steps: will load current iLxAnd a component i in the fundamental frequency rotation coordinate system obtained by park transformationLd、iLqExtracting the DC component by a low-pass filter
Figure FDA0003407150290000027
Further obtaining AC component
Figure FDA0003407150290000028
Load harmonic current is obtained through park inverse transformation
Figure FDA0003407150290000029
10. A computer apparatus comprising a memory, a processor and a computer program stored on the memory; characterized in that the processor executes the computer program to carry out the steps of the method of claim 8 or 9.
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