Prediction of Sequence Impedance for Grid-Connected VSC Based on Interpolation Method

Renewable energy sources make extensive use of voltage source converters (VSC) for power transfer, and impedance-based schemes provide technical support for their stability analysis. However, due to the difficulty of obtaining the internal parameters of converters in industrial applications, impedance measurements can only be realized by scanning frequency schemes. The implementation of this method is complicated and further hinders by the limited availability of measurement data. Meanwhile, the sequential impedance has a clearer physical interpretation than dq impedance, and it avoids phase coupling. In this paper, a cubic spline interpolation-based sequential impedance identification scheme is proposed for grid-connected VSCs, which can predict the sequence impedance model of the converter at different operating points based on a small amount of frequency scanning data. The proposed scheme does not require training and the prediction is fast. The effectiveness of the proposed scheme is verified by simulation.