A coordinated control approach for DC link and rotor crowbars to improve fault ride-through of DFIG based wind turbines
The penetration levels of wind turbines (WTs) in power grid have significantly increased in the last decade. These renewable energy resources integrated with doubly fed induction generators (DFIGs) are able to provide reactive power to support power grid during steady-state and transient state conditions. However, the DFIGs suffer from high sensitivity to system disturbance and thus, they cannot be kept connected with the utility under severe faults. Nowadays, most machines are equipped with rotor crowbar protection to prevent the damage on the converters caused by system disturbances. In this paper, two types of crowbar protections: one in the rotor winding and the second in the DC link are used to protect the rotor side converter and minimize the rotor crowbar switching time. The combined crowbars are coordinated using a novel control strategy to limit the rotor current and smoothing the DC voltage fluctuation to enhance the DFIG reactive power control for fault ride-through capability. The behavior of the DFIG is investigated when the combined crowbars are operating with the proposed coordinated control approach and results are presented.