A soft-switching three-phase five-arm dynamic voltage restorer

Abstract

This paper presents a soft-switching three-phase five-arm dynamic voltage restorer (DVR). It can solve the unusual voltage situations such as under-voltage, overvoltage, voltage sag, voltage swell and three-phase unbalanced source and load. No matter in any unusual voltage situations, the proposed DVR can maintain a stable output voltage. The voltage regulation principle of the proposed soft-switching DVR is using a transformer to couple the output of the three-phase ac/ac converter between the source and load. Besides using simple resonant units, all main switches are operated at zero-voltage-switching (ZVS) turn-on. Also, all auxiliary switches are operated at zero-current-switching (ZCS) turn-off. Rather than the conventional six-arm DVR, the proposed five-arm DVR can reduce the number of main switches. Moreover, the reduction in the number of main switches not only can simplify the control circuit but also can increase the system reliability. After all, some experimental results are presented to verify the feasibility of the proposed soft-switching three-phase five-arm DVR.