Research Of Fuzzy PI Control For APF DC Voltage

Today’s power system, due to the widespread use of power electronic devices andnonlinear loads, resulting in an increasing number of grid reactive power and harmoniccontent, the power system environment has caused a great deal of pollution, a seriousimpact on the quality of electrical energy. Therefore, the comprehensive management ofthe grid pollution is imminent. Conventional passive power filter can only compensate fora particular harmonic, has its limitations. Active power filter (APF) appears to make upfor the deficiencies of the passive power filter, it can not only dynamically governharmonic, but also compensate for reactive power, therefore we have paid close attentionto the study of active power filter.In this paper, we choose the shunt active power filter. First, the theory and thestructure of the main circuit are introduced. We use more sophisticated algorithms-basedon instantaneous reactive power theory algorithm to detect harmonic current, and couplethe output of the voltage loop to the active loop of the current loop to control the DCvoltage to reduce the fluctuations within a certain range and improve compensation effect;PWM triangular wave comparison method is taken to track and control the commandcurrent and compensation current, then six IGBT drive signals generated before arecarried to drive the device to produce the compensation current into the grid.This article focuses on the active power filter DC voltage control method. Usuallyactive power filter DC voltage uses a simple PI control, but PI control rely on accuratemathematical model of the system, it has poor robustness, easily lead to the controlledsystem presents a serious non-linear, a large super-adjust and static error, the responsespeed is relatively slow. Fuzzy control does not require very precise mathematical model,it is an effective way to resolve the uncertainty controlled system. Combining fuzzycontrol with PI control can greatly improve the system dynamic response and steady stateaccuracy, it also has better robustness. This article will introduce two fuzzy controlstrategies combined with PI, fuzzy PI switch control method and adaptive fuzzy PI controlmethod.This article uses Matlab2009b to simulate the active power filter model dynamically,and analyses the simulation results detailed. Finally, the hardware and software in theAPF system are introduced, the control board includes DSP and FPGA chips, to improvethe efficiency of master chips, using DSP28335to write the algorithm of harmonic currentdetection and current tracking programs, and the program of the Modbus communicationprotocol, using FPGA to write external mold/digital conversion chip AD7656controlprocedures.This paper completed the simulation of active power filter (APF) control system，andfocuses on the combination of fuzzy control and PI control, to control the APF DC side voltage. The simulation results show that this control strategy is effective than PI control,and it is improved significantly. Finally, write the master program and peripheralprogram.