Structure evolving and comparative analysis of grid-connected converter output filter.

The filtering characteristics of the output filter directly determine the grid-connected performance and cost and volume of the grid-connected converter. Based on a deep analysis of harmonic attenuation characteristics of LCL-type and LLCL-type filters, a unified circuit model of the output filter was proposed in this paper. According to this model, the possible structures of filters below the fifth order are deduced, summarized, and compared, and two new filters, LLCLC_A type and LLCLC_B type, are proposed. A comparative study of these filters in terms of filter characteristics, impedance characteristics, parameter design, and resonant spike damping was carried out. The results show that the LLCLC_A-type filter has advantages over the other three filters. The LLCLC_A-type filter is named the LLCLC-type filter. Finally, both simulation and experimental results verify the correctness and effectiveness of the proposed LLCLC-type filter. The research in this paper is a guide to the design of a grid-connected converter output filter. [ABSTRACT FROM AUTHOR]