Type-2 Wind Turbine with Additional Sub-synchronous Resonance Damping

Wind turbines (WTs) employing a wound rotor induction generator with adjustable external resistors are known as Type-2 WTs. This WT topology is available in USA since 2001. This WT is regulated by controlling its pitch angle and its external rotor resistor to operate as a variable slip WT. The slip range can reach up to 10% above synchronous speed. This paper demonstrates that with a proper control, Type-2 WTs are capable to damp out subsynchronous resonance (SSR) oscillations commonly found in series-compensated transmission lines. The size of wind power plant (WPP) has increased over the years and some WPP exceeds 500 MW. They can be treated as energy sources which can regulate the power delivered to the grid. In order to analyze the capability of Type-2 WPPs to damp power system oscillations, the IEEE first benchmark model for SSR studies is modified with an aggregated Type-2 WPP model connected to the system. An additional control loop is implemented to modulate the effective rotor resistance so that SSR oscillations can be damped. The models are implemented and simulated using PSCAD/EMTDC software platform.