Flexible control of DC-link voltage for doubly fed induction generator during grid voltage swell

This paper studies the impacts of grid voltage swell on the dc-link voltage for doubly fed induction generator (DFIG). A flexible algorithm of the dc-link voltage is proposed to meet the requirements of wide variation in grid voltage. The dc-link voltage reference is regulated with the variation of grid voltage. Thus, the dc-link voltage is maintained to a constant during normal operation but a relatively high value during grid voltage swell. The power losses are evaluated with the conventional control strategy and the proposed control strategy. The results show that the flexible control method will reduce power losses of the back-to-back converter. A laboratory platform is developed to verify the analysis and the control strategy.