Asymmetric injection and grid impedance switching-based impedance measurement method of grid-connected converters

As the interaction between the GCC (grid-connected converter) and the power grid gradually deepens, the stability analysis of the new-energy system becomes more and more important. Impedance analysis method is often used to analyze the small signal stability of the new-energy system. The black box model of the converter can be obtained by impedance measurement technology, which has engineering significance. The traditional measurement method needs to inject disturbance into the main circuit, which has the disadvantage of high cost. In this paper, a positive and negative sequence impedance measurement method of converter based on asymmetric virtual disturbance injection and grid impedance switching is proposed. The positive and negative sequence impedance of converter can be obtained at the same time by injecting disturbance into two phases of current sampling signal. The specific operation steps are divided into five steps. According to th ese steps, the simulation results show that the proposed method is correct.