Parametric Identification of DQ Impedance Model for Three-Phase Voltage-Source Converters

The impedance-based approach has been widely used to predict the system stability at each point of connection of the individual voltage-source converter (VSC). However, the analytical impedance model is difficult to obtain because the system operators usually have no access to the detailed data of the control system of power converters due to confidentiality of manufacturers. Therefore, impedance measurement is necessary. In this paper, a broadband signal, pseudo-random binary sequence (PRBS) is selected as injected perturbations to excite the voltage and current response of VSC. Moreover, a parametric identification method for impedance measurement of VSC in the dq-frame is proposed based on recursive least squares algorithm. According to the nonlinear time-domain simulation data and the experimental data, the identified model of the converter is obtained. The accuracy of this impedance measurement method based on the parametric identification is verified in both the time-domain and frequency-domain.