Dynamic voltage restorer with an improved strategy to voltage sag compensation and energy self-recovery

In this paper, an improved control scheme is proposed to improve the voltage quality of sensitive loads using dynamic voltage restorer. The existing control strategies either put emphasis on the optimal control during steady operation stage of compensation or correct the phase angle jump in the initial stage of compensation. In current researches, the impact of phase jump characteristic of voltage sag on the load side after voltage sag recoveries is widely ignored, further, there are still drawbacks in existing energy self-recovery strategies of DVR. Therefore, to improve the overall voltage compensation time while correcting the phase jump and accelerate the energy recovery of dc link side, this paper aims to 1) Propose the strategies to minimum active power consumption during voltage compensation stage and maximum active power absorption during energy self-recovery stage. 2) Deliver smooth transition in dynamic process to ensure the flexible switching between two stages. Theoretical analysis of proposed strategy is been validated through simulation and experimental results.