Real-time simulation of subsynchronous resonance in Type-III wind turbines

Subsynchronous resonance (SSR) with series-compensated transmission lines has been reported for Type-III wind turbines employing doubly-fed induction generators (DFIG). Existing theories about such SSR behavior either ignored the effects of power electronics and control, or didn´t model such effects properly to allow the development of cost-effective solutions through modification of control. This paper first presents real-time simulation models for a Type-III wind turbine with typical turbine and converter-level control functions. Numerical experiments are then conducted using real-time simulation to quantify the effects of various parameters on the SSR behavior. Positive and negative sequence impedance responses of the DFIG are also obtained by real-time simulation and used in conjunction with an impedance-based system stability criterion to explain the simulated SSR behavior as well as to develop new methods for rotor-side converter control to avoid such SSR.