An Optimal Method to Design a Trap-CL Filter for a PV AC-Module Based on Flyback Inverter

The power factor and total harmonic distortion (THD) are important considerations when designing an output filter. In the case of the photovoltaic (PV) ac-module, the size and weight also have to be taken into consideration. This paper proposes an output filter to reduce size and weight, and provides the optimal design method for a PV ac-module. The proposed output filter consists mainly of a conventional CL filter with a trap filter. The trap filter is used to eliminate the harmonic at the switching frequency that contains most of the harmonics. Therefore, total inductance and the size of the filter can be reduced although the output filter components are increased. This paper presents analysis of the proposed filter characteristics in detail. Also, an optimal design method reducing the size of the output filter components including the damping resistor is proposed. The proposed methods are verified on the experimental prototype rated at 320 W with an ac-module based on the interleaved flyback inverter. The total filter inductance and volume are, respectively, reduced to 9.54% and 26.62% with the same performance.