LCL filters are widely used in microgrid converters because of their high level of harmonic attenuation introduced by series inductors. The main challenge of the LCL filters is to damp the associated resonance peak in order to improve the quality of grid injection current. To address this challenge, this paper presents an improved weighted average current control (WACC) method. It applies grid-voltage-feedforward in an inner loop to solve the resonance peak of the filters and reduce the impacts of the grid voltage harmonics on the grid injection current. A PI controller is designed in an outer loop to keep the DC voltage stable. The improved strategy not only simplifies the design process, but also makes the LCL filter system more robust. Simulation and experimental results verify the feasibility of the proposed strategies applied to a dual-buck bidirectional converter with a LCL filter.
Keywords weighted average current control, dual-buck bidirectional converter, LCL filters, PI controller