Control Algorithm Of Active Power Filter Based On Repetitive Control

With the widely use of power electronics devices in industry, prolusion of powersupply network has been attracted serious concern more than before. Active PowerFilter(APF) is one of the important measures in fields of compaction of harmonic currentand improving electrical quality of power supply network. The key to compaction is anaccurate detecting method and a real-time compaction technology. This paper focus onthe case of the current harmonic compensation of three-phase harmonic distortion andimbalance load. In order to achieve harmonic current suppression and reactive powercompensation, active power of parallel and related issues in-depth study. Repetitivecontrol is proposed based on the active power filter design, focusing on the detection andcompensation strategy of three-phase harmonic distortion and imbalance load.Firstly, this paper analyses the generation and harm of harmonics and reactivecurrents in power system. It also points out the significance of eliminating harmonics andcompensating reactive currents. The paper analyses the harmonic current detection andcompensation technology which are widely used in APF, especially the detectingmethods for three-phase harmonic distortion and imbalance load. At present, ip-iqapproach based on theory of instantaneous reactive power is used in most APF systems.But it will be waste a lot in the situation of imbalanced lord which only high frequencyharmonic companion is needed.In order to detecting the harmonic current accurately, the paper researches on adeveloped detecting method based on ip-ip detecting method, Fourier transformationmethod based on a sliding window recursive, and single-phase reactive method. Thepaper expounds specifically on those detecting methods using in three phase three wiresand three phase four wires and analyses the advantages and disadvantages of thosedetecting methods.This paper presents the system structure and operation principles of three-phase APF.In the control circuit, traditional PID controller, linear time-optimal controller and robustcontroller can not achieve tracking without error because the reference harmonic currentsignal usually is a periodically pulsant signal. In order to achieve better control effect, the paper proposes algorithm of repetitive control based on internal-model principle. Thenpresents the basic principle and structure of repetitive control, and introduces the designprocess of the repetitive control. The paper analyses the steadiness of the system bymeans of the frequency-domain method. The results show that the control method canimprove the accuracy of harmonic companion.At last, this paper establishes an simulation model of APF system based on thecurrent detecting method and repetitive control scheme with MATLAB/Simulinksoftware which the paper research before. The simulation results show that the APFsystem a good performance that the APF can detect and compete harmonic current inpower system accuracily and rapidly.