Sequence Impedance Modeling and Characteristic Analysis of Island Inverter with Dual Sequence Control

The island inverter under dual-sequence control method controls the negative sequence voltage by introducing a negative sequence branch to ensure the symmetry of the output voltage. In this paper, the small-signal wide-band sequence impedance model of the island inverter under dual-sequence control is established by harmonic linearization method. Then, the wide-band frequency-sweeping simulation of this control method is carried out in MATLAB. The sweep result is consistent with the established sequence impedance model, which proves the correctness of the established sequence impedance. The analysis of the sequence impedance model shows: the fundamental cause the double-sequence control method can suppress the negative sequence voltage is that the dual-sequence control greatly reduces the negative sequence impedance of the island inverter at the fundamental frequency (50Hz), thereby suppressing the negative sequence voltage drop generated by the negative sequence current of the load on the negative sequence impedance of the inverter. This impedance model can be applied later to the stability analysis of the AC microgrid.