An On-Line Measurement Method of Grid Impedance Based on Three-Phase LCL Grid-Connected Inverter

In the new power system, the grid impedance presents complexity and time-varying, and accurate measurement of grid impedance is the basis for ensuring the steady operation of an inverter grid-connected system. In consideration of the poor accuracy of the traditional measurement method in the mid-high frequency band, this paper improves the traditional measurement method to ensure that the grid impedance can still be accurately measured in the middle and high frequency. This method can obtain a signal with rich spectrum by superimposing high-frequency sine wave on the basis of traditional single-pulse disturbance signal, which makes up for the vacancy of middle and high frequency spectrum. In this paper, measurement results of the two methods are compared by MATLAB/Simulink, which verifies the effectiveness of the method and has reference significance for the on-line measurement of grid impedance in practice.