Optimization Design Of Shunt APF Based On Current Decoupling Control

In the three-phase four-wire power supply system,the use of a large number of power electronic devices and non-linear loads causes power quality problems such as harmonic pollution,low power factor,and mid-line overcurrent.These problems seriously affect the quality of power supply system.Compared with passive filters composed of passive devices such as capacitive and inductor,active power filter(APF)as a new type of compensation device can solve power quality problems more efficiently and flexibly.Current control strategy is the key of APF.Various current control strategies,such as hysteresis control and PI control have been introduced into APF to improve compensation accuracy and dynamic response speed.An improved current decoupling control algorithm using repetitive-PI control has been proposed to ensures the accuracy of the compensation and improve the dynamic response speed.Then,the improved current decoupling control algorithm is compared with the traditional current decoupling control algorithm through simulation and experiment.The results verify the correctness of the proposed control algorithm.The paper first analyzes the working principle and basic structure of APF.It focuses on the three-phase four-leg shunt APF,analyzes the compensation principle and builds a mathematical model.Then it introduces two methods used to extract harmonic,reactive,and midline currents in the load current.The principle of the two strategies and the selection of the controller parameters also have been analyzed.These works provide a theoretical basis for the following simulations and experiments.The MATLAB/SIMULINK is used as the simulation tool to build the APF simulation model.It compares and analyzes the simulation results of the two strategies.In order to further verify the superiority and inferiority of these two control strategies,a three-phase four-leg shunt APF experimental prototype based on DSP28335 chip control has been designed.It introduces the design process of the prototype software and hardware in detail.It uses Code Composer Studio(CCS)software to control the hardware platform.Finally,based on the experimental results,it compares the harmonic current distortion ratio(THD)and neutral current compensation before and after compensation.It also testes the dynamic response performance of the improved current algorithm.The above facts confirm the effectiveness of the algorithm.