Research And Design Of Three-phaze Four-wire APF

Harmonics in power grid have risen significantly as the widely application of non-linear loads in the power supply system , and the harm is increasingly serious.The active power filter (APF) which has higher compensation precision and real-time capability becomes the important measure to compensate harmonic wave and improve the power quality, and concerned by research community widely. The three-phase four-wire system has widely applications in low-voltage distribution network,and the problems such as harmonic,zero sequence harmonic current and three-phase unbalance are becoming more and more serious, which has well practical application significance in the research of active power filter.This thesis presents the research background and meaning of the three-phase four-wire active power filter, analyzes the structure and working principle of active power filter, and carries out its mathematical modeling. Based on the mentioned earlier this thesis analyzes APF harmonic current detection method and control technology in-depth.This thesis detailed introduces the theory of traditional FBD harmonic detection algorithm, based on the original low-pass filter was improved, which improve the execution speed of former FBD detection algorithm. Based on the accurate detection of the harmonic current,the APF system with dual DSP as the controller is set up,and the design of the main control circuit, signal conditioning circuit and driving circuit is given. At the same time,combining several control strategies of current research, the proportional resonance (PR) control technique is introduced in the current loop control, which can realize the tracking of the traffic without static error and also be used to compensate specified harmonics. In order to weaken the frequency fluctuation to APF performance, the improved PR controller is used as the current tracking control strategy to improve the compensation accuracy of APF. This thesis discusses the stability and tracking performance of improved PR controller in depth. Further, the stability of the DC side voltage and balance control of capacitor voltage is realized by the double PI control strategy. And the zero sequence current is effectively processed.This thesis establishes the simulation model of active power filter system in MATLAB/Simulink based on the research of the three-phase four-wire active power filter. The improved FBD harmonic detection algorithm and the PR control algorithm is effective and feasible verified by the simulation analysis.