Comparison four topologies for three-phase dynamic voltage restorer

Dynamic voltage restorer (DVR) is a custom power device suitable for solving voltage related power quality (PQ) problems including voltage sags and voltage swells. This paper compares four topologies for three-phase DVRs. Also, a three-phase DVR using push-pull inverters is proposed. The inverter of each phase in the proposed DVR operates and is controlled independently so that the unbalanced voltage sags and swells can be compensated as well as the balanced ones. In comparison with the three-phase six-switch inverter based DVR, the proposed DVR offers improved operation under unbalanced conditions while keeping the equal number of the switching devices to that of a six-switch pulse width modulated (PWM) inverter. On the other hand, the proposed DVR uses reduced number of switching devices in comparison with the three-phase DVR based on the three H-bridge inverters. In comparison with the split-capacitor three-phase inverter based DVR, the proposed topology offers extended compensation range. Simulation results carried out by the PSCAD/EMTDC are presented to compare the mentioned three-phase DVR topologies.