A Study on Passive Control Strategies for Specific Sub-Harmonic Suppression in Grid-Connected LCL Inverters

In the process of grid-connected operation of microgrid, the current of grid-connected inverter is prone to distortion phenomenon due to the influence of grid voltage harmonics and switching characteristics, while the existence of nonlinear loads also affects the grid-connected current, which affects the system stability and the quality of grid-connected current. For this reason, a specific subharmonic current suppression method based on passive control is proposed for the three-phase grid-connected inverter in this paper. Firstly, the PCHD mathematical model of the three-phase grid-connected inverter is established and the current loop passive controller is designed; then the compensation loop is introduced with the multiple reference fame (MRF) method to control the harmonic currents independently; Finally, a system simulation model is built to verify the effectiveness of the adopted control strategy. The simulation results show that the proposed control method can effectively improve the power quality of the grid-connected current with the advantages of passive control.