Rotor current control for a doubly-fed induction generator using a novel nonlinear robust control approach based on extended state observer-backstepping

The doubly-fed induction generator (DFIG) has been widely applied in wind power generation systems. However, the applications of DFIG are limited by the failure of power system and inefficient fault ride-through (FRT) strategy, which lead to overcurrent in rotor windings. The overcurrent that results from continuous operation of DFIG may cause a serious tripping accident in wind turbine generators. The occurrence of overcurrent at the rotor side of DFIG must be prevented to ensure safe operation of the rotor-side converter. Preventing overcurrent can enhance the control ability of rotor current and the FRT capacity of DFIG. A novel rotor current controller for DFIG is designed to overcome its strong nonlinearity. The controller combines extended state observer (ESO) with backstepping theory. ESO is used to dynamically estimate and eliminate the model error and the uncertain external disturbance of the rotor current of DFIG. The controller is designed on the backstepping method, and then the feedback of ESO is used to eliminate the nonlinear factor. As a result, computation complexity is reduced. The controller has both superior static, dynamic performance, and strong robustness. The effectiveness of the proposed control approach is verified.