Coordinated control strategy for doubly-fed induction generator with DC connection topology

With the development of wind power generation system and requirement of large-scale and long-distance power transmission, it is greatly important for wind farm to achieve the high effective DC grid connection technology. This study presents a novel grid connection topology for doubly-fed induction generator (DFIG) connected to a DC-link, in which a stator side converter and rotor side converter fed by a common DC bus are employed. Coordinated control method for the converters is proposed to regulate the electromagnetic torque directly based on the air-gap flux orientation technique. Compared with the traditional grid connection system, the proposed system has a lot of advantages such as simpler structure, lower requirement for the converter capacity and higher power transmission efficiency. The power distribution between stator side converter and rotor side converter is analysed based on the proposed grid connection topology. Finally, DFIG-based experimental system is developed to validate the correctness and availability of the proposed DC grid connection topology and control strategy.