The use of voltage feed-forward control under a weak grid will increase the negative phase shift of the output impedance of the grid-connected converter at the cross-cutting frequency,which may lead to the harmonic resonance of the grid-connected current.Aiming at the problem a resonance suppression strategy for the LCL-type grid-connected converter based on the three-frequency-band impedance remodeling is proposed.The strategy establishes a three-frequency-band equivalent model of output impedance on the basis of grid voltage feed-forward control,and uses the three-frequency band reshaping gain factor to reshape the output impedance of the grid-connected converter in different frequency bands,which reduces the negative phase shift of the output impedance in the mid-frequency band,and improves the stable operation capability of the grid-connected converter under a weak power grid.Simulation results show that the strategy retains the ability of traditional voltage feed-forward control to suppress grid background harmonics,improves the phase margin of the grid-connected system,and effectively suppresses the resonance phenomenon of the grid-connected current.
关键词
弱电网/LCL并网变流器/背景谐波电压/三频段阻抗重塑/电网电压前馈
Key words
weak grid/LCL grid-connected converter/background harmonic voltage/three-frequency-band impedance remodeling/grid voltage feed-forward
万方数据