Single-Phase L-Type Bridge Inverter With Parallel Active Power Filter

The integration of Distributed Energy Resources (DERs) is increasing, but inverters face challenges like harmonic currents. Traditional solutions like passive filters are bulky and costly. This paper introduces a parallel active power filter (PAPF) designed for single-phase L-type bridge inverter, incorporating an H-bridge circuit and a small LC series branch. The PAPF emulates the behavior of L-type filter by modifying LLCL passive filter. The proposed PAPF maintains the advantage of LLCL filter for eliminating harmonics at the switching frequency and mitigate the harmonics at resonance frequency, by using a pseudo connection instead of a real connection at LLCL structure. The operating principle and parameter design of the proposed circuit have been discussed and analyzed. Comparison results have been made between the proposed active filter and LLCL filter and L-type filter to show the advantages of the proposed active filter. Simulation results in MATLAB/SIMULINK verified the effectiveness of the parallel active filter.