Analysis and mitigation of SSR problems in large-scale wind farms with doubly-fed wind turbines

The existing operation experiences indicate that subsynchronous resonance (SSR) may occur in wind farms which are connected to series compensated systems. Hence, it is necessary to analyze the mechanism of SSR in wind farms, which will contribute to the solutions. Firstly, an equivalent system model for the analysis of SSR is established based on the real parameters of a wind farm in China. The SSR phenomenon of this model is presented by time domain simulation. The impacts on SSR from the factors such as wind speed, number of generators, and control parameters of doubly-fed induction generators (DFIGs) are checked using eigenvalue analysis. An equivalent circuit is deduced for the mechanism analysis of SSR. Based on this circuit, the mechanism of SSR impacts from aforementioned factors are analyzed in details. Considering all the analysis, it is pointed out that the SSR phenomenon of wind farms is a special electrical resonance, and nothing to do with the generator shaft. Solutions of SSR in wind farm are also proposed and are verified by simulations and eigenvalue analysis.