A fast switching strategy for DVR based on current control algorithm

Abstract

Dynamic voltage restorer (DVR) needs to turn off the anti-parallel bypass thyristor (SCR) at the output terminal when dealing with voltage sag phenomenon. When applying traditional methods to force the thyristor off, it is essential to determine the direction of thyristor current according to the sensor sampling information, which has the risk of misjudgment under actual conditions. A novel fast switching strategy (FSS) for DVR is proposed in this paper. DVR-FSS uses the current control algorithm to force off the bypass SCR, which can realize the smooth transition from bypass state to compensation state. Firstly, the basic working principle of the DVR-FSS is introduced based on which the FSS operating modes are analyzed in detail. And the mathematical model of DVR-FSS in key modes is established to analyze the influence of FSS control algorithm parameters on the dynamic or steady performance of DVR. Secondly, the modeling and quantitative analysis of the fundamental voltage drop introduced by DVR in the steady-state mode are used to explain that the impact of FSS on the primary side load supply voltage is within the acceptable range. Finally, the correctness and feasibility of the proposed FSS are fully verified by experiments, which indicate that FSS has strong robustness at the same time.

Keywords

• Dynamic voltage restorer (DVR)
• Switching strategy
• Current control algorithm
• Mode analysis
• System performance