Optimal Design Method of Passive LCL Filters for Grid-Connected Inverters

Imprudent selection of passive LCL filters parameters may result in worse filtering and excessive power losses. Existing designs methods are only able to provide a range for filters parameters, and therefore are not able to guarantee performance, without an extensive trial and adjustments process. To overcome this problem, a novel optimal design method of LCL filters, with several passive damping techniques, is proposed in this paper. The method is based on solving a constraint multi-objective optimisation problem, using genetic algorithm to obtain optimal passive LCL filters parameters. The goal of the optimisation method is to achieve high harmonic attenuation performance, reduce switching frequency ripples and minimise power loss. The design method is verified through simulation studies carried out on a three-phase grid-connected voltage source inverter (VSI) in a distributed generation (DG) system. The simulation results show that the new method can achieve higher ripple reduction and greater harmonic attenuation than existing methods. The paper also evaluates the performance of different passive LCL filter topologies.