Research of megawatt level variable speed constant frequency wind power unit based on doubly fed induction generator

Based on the stator flux linkage oriented control theory of doubly fed induction generator (DFIG), the control system of the megawatt level variable speed constant frequency (VSCF) wind turbine generator system, which adopts back-to-back PWM converters, is proposed. The Dual-PWM converter is divided into two parts: grid side converter and rotor side converter. The grid side converter adopts the voltage and current dual close-loop control strategy. The rotor side converter adopts rotor current open-loop control strategy and the active and reactive current close-loop control strategy. The full-load experiment is conducted when DFIG is operating under sub-synchronization or super-synchronization condition. The control system can also respectively regulate the active and reactive power output under variable wind speed condition. The experiment results validate the feasibility of the control systems.