Improved design of LCL-filter based active power filters using NPC converter

YU Nian-chang, YANG Jia-qiang*

(School of Electrical Engineering, Zhejiang University, Hangzhou 310027, China)

Abstract: Aiming at achieving low switching frequency current for active power filters (APF), the design of LCLfilter for APF using neutral point clamed converter was studied. Affections of different parameters were analyzed. Then, constraints and principles on LCL-filter design were concluded. A simple and practical design procedure of LCL-filter was proposed subsequently. Firstly, the resonant frequency of LCL-filter was set according to the highest harmonic order and switch frequency. Then, the parameters of the LCL-filter were optimized based on the design principles and constraints with smaller volume and lower cost. Finally, the theory was verified by experiment in a 5 kVA shunt APF systems. The results indicate that, the proposed design can effectively eliminate the switching current without reducing the bandwidth of APF.