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.