The Study Of Shunt APF With LCL Filter

In recent years, Power Electronics Technology has been developed rapidly, and has made the life of human beings more convenient. However, harmonic pollution will be produced by power electronic devices, which will influence the power grid quality. Active power filter (APF) has been widely used in power system harmonic control because of its high control precision and good dynamic compensation effect. In this paper, the three-phase three-wire active power filter will be studied.The development history, fundamental theory and classification of APF are included in the paper. The key technology, main circuit design, control system design of three-phase three-wire APF are analyzed emphatically. In order to make APF apply in high power applications, the paper describes the multiple APF parallel technology, and emphatically studies capacity-proportion distribution scheme and carrier phase-shifted multiple scheme. Considering the cost of system and the size of current ripple, LCL filter is adopted. Then the design and control of LCL filter are analyzed in detail. The proportional control and repetitive control are combined in the design of system control algorithm, and a double loop repetitive controller is obtained. On the basis of the above, the half-period repetitive control is proposed to enhance the dynamic performance and the steady performance of the system. In order to reduce the influence of DC voltage fluctuation on harmonic compensation, the traditional voltage loop is improved in the paper.Adopting the above methods, the simulation model of the system is set up in MATLAB/Simulink, and the experimental prototype is made.Using single APF system and double APF parallel system compensates resistance-inductance load and resistance-capacitance load, the simulation and experimental results obtained all verify the feasibility of methods proposed in the paper.