Analysis of low frequency interactions of DFIG wind turbine systems in series compensated grids

Recent field events and subsequent studies have indicated that doubly-fed induction generator (DFIG) based wind farms might be susceptible to adverse interactions with series compensated systems. This paper focuses on the analysis of the interaction phenomenon. A new benchmark network is proposed to address the investigation of low frequency oscillations between wind generation and series compensated systems based on realistic system parameters. Nonlinear components and detailed representation of wind turbines are taken into account. An analytical model for a generic DFIG based wind farm is developed considering all inner and outer loops as well as its mechanical parts. Participation factor analysis is applied to the model to identify states most contributing to the critical modes and to address suitable mitigation. Sensitivity analysis is used to support redesign of control parameters. Investigations indicate that resonance can be avoided with proper control tuning. Finally, the capabilities of a screening technique for SSR risk assessment suitable for early project stages are also investigated and its results compared to the modal analysis. All conclusions are verified with detailed electromagnetic transient (EMT) simulations.