CN107302219B - Closed-loop control method for power grid angle of active power filter - Google Patents
Closed-loop control method for power grid angle of active power filter Download PDFInfo
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- CN107302219B CN107302219B CN201710656116.4A CN201710656116A CN107302219B CN 107302219 B CN107302219 B CN 107302219B CN 201710656116 A CN201710656116 A CN 201710656116A CN 107302219 B CN107302219 B CN 107302219B
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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
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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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
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- 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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Abstract
The invention discloses a closed-loop control method for the power grid angle of an active power filter, which is simple and easy to realize and has good dynamic and steady-state compensation effects. The method detects the current of the side of the power grid, extracts the D-axis and Q-axis direct current components of each harmonic by using an instantaneous reactive power algorithm, gives the direct current components as 0, controls each harmonic by using a PI (proportional-integral) regulator to track in a non-differential mode, and avoids the adoption of complex and difficult-to-realize intelligent algorithms such as repetitive control and proportional resonance control aiming at non-differential control of alternating current. The invention can conveniently realize the compensation of specific subharmonic, avoid the compensation of irrelevant harmonic current and well utilize the effective capacity of the filter; compared with an intelligent algorithm, the method is simple to implement and high in reliability, greatly improves the compensation performance of the filter compared with open-loop control, and has a very large application prospect.
Description
Technical Field
The invention belongs to the field of power quality control, and relates to a control method of an active power filter.
Background
With the development of power electronic technology, a large number of nonlinear loads are put into use, the pollution of power grid harmonics becomes more and more serious, and the safety of power utilization is threatened to a certain extent. With the increasing demand of the society for power quality coming in the information age, suppression of harmonics in power systems has become a major issue in the field of power electronics.
Passive power filters are being replaced by active power filters because their filtering performance is greatly affected by the frequency and impedance of the power grid. The active power filter can make up the deficiency of the passive filter, and the filtering effect of the active power filter is incomparable with that of the passive power filter. Currently, most active power filters applied to the field adopt an open-loop control mode for detecting load current to perform harmonic extraction control, and the control mode has the following disadvantages: 1) when the sampling error is large, the compensation effect is seriously influenced; 2) because the current loop instruction is the superposition of alternating current components of various frequencies, a common P regulator or PI regulator cannot realize the non-differential tracking of the alternating current quantity, even high-order components can be amplified, the system stability is threatened, intelligent algorithms such as repetitive control, proportional resonance and the like for realizing the non-differential control of the alternating current components are not mature, and the realization difficulty is quite large; 3) because the current loop can not achieve the non-differential control of the harmonic instruction, each frequency current has certain phase and amplitude errors, phase and amplitude correction needs to be carried out successively during debugging, and field debugging is complicated.
For the above problems of open loop, some scholars have proposed some effective closed loop control methods, but these methods have their limitations, or need to adopt intelligent algorithm, or have slow response speed, complex algorithm and great difficulty in implementation.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a closed-loop control method for the power grid angle of an active power filter, which is simple and easy to implement and has good dynamic and steady-state compensation effects.
The purpose of the invention is solved by the following technical scheme:
the topological structure of the active power filter is as follows: the alternating current side of the three-phase voltage type inverter is connected with a power grid in parallel through a group of three-phase reactors; the direct current side of the inverter is connected with the capacitor to form a closed loop for providing inverter voltage support;
the closed-loop control method comprises the following steps:
a. the voltage of the power grid is phase-locked by using a soft phase-locked loop, and the obtained angle is used for generating an instantaneous reactive power change matrix;
b. detecting the current on the network side, converting each subharmonic current to a DQ coordinate system by using the instantaneous reactive positive change matrix, and obtaining a direct current component through a low-pass filter
0 is given as D-axis and Q-axis, direct current component
Regulating with a PI regulator as feedback;
c. according to the specific subharmonic compensation function setting requirement, summing all subharmonic current commands needing compensation to obtain a total harmonic current command: sigma iaf、∑ibf、∑icf；
d. Detecting bus voltage UdcfIs different from the given valueControlling by using a PI regulator, outputting a voltage feedforward value added to a network side as a Q axis given value, setting a D axis as 0, and converting to a three-phase static coordinate system by using an instantaneous reactive inverse transformation matrix to obtain a voltage stabilization active instruction iaf、ibf、icf；
e. And d, summing the total harmonic current instruction and the voltage-stabilizing active instruction obtained in the step c and the step d to serve as a final control instruction, and controlling the output current of the three-phase voltage inverter bridge.
In the step e, the specific implementation method for controlling the output current of the three-phase voltage inverter bridge according to the final control instruction is as follows: and detecting the self output three-phase current of the active power filter as feedback, making a difference with the final control instruction, firstly adjusting by using a P adjuster, and then forming PWM (pulse width modulation) driving pulse by using an SPWM (sinusoidal pulse width modulation) modulation mode to drive the IGBT inverter bridge to act so as to generate output current.
The invention can convert each subharmonic into DC component of DQ axis for differential control from the angle that PI regulator can perform differential control on DC component. The control method is simple and easy to realize, has good dynamic and steady compensation effects, and can fundamentally improve the compensation performance of the device. The method has the following advantages:
1) the method comprises the steps of detecting the current on the side of a power grid, extracting D-axis and Q-axis direct current components of each subharmonic by using an instantaneous reactive power algorithm, setting the direct current components to be 0, realizing the non-differential control of each subharmonic current by using a PI (proportional-integral) regulator, and avoiding the adoption of a complex immature intelligent control algorithm.
2) The compensation of specific subharmonic can be simply realized, the inconsequential harmonic current can be avoided from being compensated, and the effective capacity of the filter is well utilized.
3) Compared with an intelligent algorithm, the method is simple and easy to implement, has high reliability, greatly improves the compensation performance of the filter compared with open-loop control, and has a very large application prospect.
Drawings
Fig. 1 is a schematic diagram of an active power filter topology related to the control method of the present invention.
Fig. 2 is a control block diagram of the control method of the present invention.
Detailed Description
The invention is explained in more detail below with reference to specific embodiments and the attached drawing:
the active power filter topology as shown in fig. 1: the three-phase voltage type inverter is connected to the power grid side in parallel through a three-phase reactor, and the direct current side of the inverter is connected with a capacitor to provide voltage support required by inversion.
The closed-loop control method of the invention is shown in fig. 2, and the specific implementation steps are as follows:
three-phase network voltage ea(ii) a Three-phase network side current is recorded as isa、isb、isc(ii) a Three-phase load current is denoted as iLa、iLb、iLcThe self-output three-phase current of the active power filter is recorded as ia、ib、ic；
Setting value U for DC bus voltagedcfThe actual sampling value of the direct current bus voltage is n, and the number of the harmonic waves is n.
a. Using typical soft phase-locking algorithm to measure the grid voltage eaAnd performing phase locking, wherein the obtained angle is used for the instantaneous reactive power change matrix.
b. Detecting the current on the network side, and transforming each subharmonic current to a DQ coordinate system by using an instantaneous reactive positive change matrix to obtain dsn、qsn，：
Wherein,
in FIG. 2, the ABC/DQ matrix is CdqC32。
Then obtaining direct current component by LPF filtering
0 is used as a D axis,Given the orientation of the Q-axis,
as feedback, using a PI regulator for regulation with an output derrn、qerrn。
Converting the result into a three-phase static coordinate system by using an instantaneous reactive inverse transformation matrix to obtain an instruction i of each subharmonic currentanf、ibnf、icnf。
Wherein,
the DQ/ABC matrix in FIG. 2 is
c. According to the specific subharmonic compensation function setting requirement, summing all subharmonic current commands needing compensation to obtain a total harmonic current command: sigma iaf、∑ibf、∑icf。
d. Detecting bus voltage UdcfAnd given
Performing difference, controlling by using a PI regulator, outputting and adding a network side voltage feedforward value as a Q axis given value, setting a D axis as 0, and converting to a three-phase static coordinate system by using an instantaneous reactive inverse transformation matrix to obtain a voltage stabilization active instruction iaf、ibf、icf。
e. And summing the obtained total harmonic current instruction and the voltage-stabilizing active instruction to serve as a final control instruction to control the output current of the three-phase voltage inverter bridge. The method comprises the following steps: the detection filter outputs three-phase current as feedback, the difference is made with the total instruction, the P regulator is used for controlling, and finally, a PWM driving pulse is formed in an SPWM modulation mode to drive the IGBT inverter bridge to act and generate output current.
The control method is verified by building a simulation model, and the correctness and the superiority of the control method are confirmed.
Claims (1)
1. A closed-loop control method for the power grid angle of an active power filter is characterized by comprising the following steps: the topological structure of the active power filter is as follows: the alternating current side of the three-phase voltage type inverter is connected with a power grid in parallel through a group of three-phase reactors; the direct current side of the inverter is connected with the capacitor to form a closed loop for providing inverter voltage support;
the closed-loop control method comprises the following steps:
a. the voltage of the power grid is phase-locked by using a soft phase-locked loop, and the obtained angle is used for generating an instantaneous reactive power change matrix;
b. detecting the current on the network side, converting each subharmonic current to a DQ coordinate system by using the instantaneous reactive change matrix, and obtaining a direct current component through a low-pass filter
0 is given as D-axis and Q-axis, direct current component
Adjusting by using a network side current closed-loop PI regulator as feedback;
c. according to the specific subharmonic compensation function setting requirement, summing all subharmonic current commands needing compensation to obtain a total harmonic current command: sigma iaf、∑ibf、∑icf；
d. Detecting bus voltage UdcfAnd performing difference with the given value, controlling by using a direct current bus closed loop PI regulator, outputting and adding a network side voltage feedforward value as a Q-axis given value, setting a D-axis to be 0, and converting to a three-phase static coordinate system by using an instantaneous reactive power change matrix to obtain a voltage stabilization active instruction iaf、ibf、icf；
e. Summing the total harmonic current instruction and the voltage-stabilizing active instruction obtained in the step c and the step d to be used as a final control instruction for controlling the output current of the three-phase voltage type inverter; the method comprises the following steps: and detecting the self output three-phase current of the active power filter as feedback, making a difference with the final control instruction, firstly adjusting by using a P adjuster, and then forming PWM (pulse width modulation) driving pulse by using an SPWM (sinusoidal pulse width modulation) modulation mode to drive the three-phase voltage type inverter to act so as to generate output current.
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| CN107863775B (en) * | 2017-11-29 | 2020-12-04 | 南京航空航天大学 | Current control algorithm suitable for selective harmonic compensation of active power filter |
| CN108134391B (en) * | 2017-12-16 | 2021-09-21 | 西安翌飞核能装备股份有限公司 | Control method of three-phase PWM rectifier for power grid voltage waveform distortion |
| CN109119991A (en) * | 2018-09-04 | 2019-01-01 | 天津百利机械装备集团有限公司中央研究院 | Compensation method and information data processing terminal based on APF Repetitive controller |
| CN109066684B (en) * | 2018-10-18 | 2021-05-25 | 东北大学 | Three-phase active power filter based on LCL filtering and control method thereof |
| CN109193658B (en) * | 2018-10-31 | 2019-07-09 | 国网江苏省电力有限公司苏州供电分公司 | A method of harmonic current compensation is carried out using Active Power Filter-APF |
| CN111200287B (en) * | 2018-11-16 | 2022-02-11 | 中国石油化工股份有限公司 | Appointed harmonic current injection device and harmonic current giving method thereof |
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