Oscillation Mode Identification of Self-Synchronized Voltage Source Doubly-Fed Wind Turbine Based on Continuous Wavelet Transform

The oscillation problem caused by high proportion of renewable energy and power electronic equipment in power grid is becoming more and more significant. Aiming at the problem of medium-high frequency frequency stability in a weak grid connected with self-synchronized voltage source doubly-fed wind turbine, a dynamic state-space model considering both the rotor-side converter (RSC) and the grid-side converter (GSC) was first established. The oscillation mode of the system was studied by eigenvalue-based analysis. For the defect that the eigenvalue-based method is lack of time-frequency resolution capability, the continuous wavelet transform (CWT) is adopted to reveal the oscillation mode of the doubly-fed wind generation system in the time-frequency domain. The dominant oscillation mode is identified online through the relative energy of the wavelet, which is mutually verified by the FFT-based analysis results. Finally, a simulation model of a 2MW doubly-fed wind turbine is built in PSCAD/EMTDC, and the simulation results verified the correctness of the theoretical analysis. The research results provide a reference for fault diagnosis of doubly-fed wind generation systems.