New Adaptive Scheme for Dynamic Voltage Restorer to Voltage Sag Compensation and Flexible Self-recovery

In this paper, a systematic adaptive control scheme to improve the voltage quality of sensitive loads using dynamic voltage restorer is proposed. The existing control strategies either emphasis on the optimal control during steady operation stage of compensation, or corrects the phase jump in the initial stage of compensation. Considering the few attention to the voltage phase jump on the load side after voltage fluctuation removal and the draw-back of existing energy self-recovery strategy, based on the main objective that improving the overall sag compensation time while corrects the phase jump, and accelerating the self-recovery of dc side voltage, in this paper, 1) The minimum active power of voltage compensation, and maximum active power of energy absorption strategies are adopted to the voltage compensation and self-recovery stages, respectively. 2) The proposed approach aims at completing the smooth transition of the transient process during the both stage, which ensuring the flexible switching from former to the latter.