Investigation On Dynamic Voltage Restorers With Two Dc Links And Series Converters For Three-Phase Four-Wire Systems

Abstract

This paper investigates a dynamic voltage restorer (DVR) composed of two conventional three-phase inverters series cascaded through an open-end winding (OEW) transformer, denominated here DVR-OEW. The DVR-OEW operating with either equal or different dc-link voltages are examined. The proposed topology aims to regulate the voltage at the load side in the case of voltage sags/swells, distortion, or unbalance at the grid voltage. A suitable control strategy is developed, including space-vector analysis, level-shifted PWM (LSPWM) and its equivalent optimized single-carrier PWM (SCPWM), as well as the operating principles and characteristics of the DVR. Comparisons among the DVR-OEW and conventional configurations, including a neutral-point clamped (NPC) converter based DVR, are furnished.