New control technique applied in dynamic voltage restorer for voltage sag mitigation

This paper deals with a new control technique for the modeling of a dynamic voltage restorer (DVR). The DVR is a power electronics device that is able to compensate voltage sags on critical loads dynamically. By injecting an appropriate voltage, the DVR restores a voltage waveform and ensures constant load voltage. The compensating signals are determined dynamically based on the difference between desired and measured values. The DVR consists of voltage source converter (VSC), injection transformers, passive filters and energy storage (lead acid battery). The efficiency of the DVR depends on the efficiency of the control technique involved in switching the inverter. In this paper a novel structure for voltage sags mitigation and for power quality improvement are proposed. There is an increasing trend of using space vector PWM (SVPWM) because of their easier digital realization and better dc bus utilization. This paper also discussed a new control algorithm based on space vector pulse width modulation (SVPWM) technique to generate the pulses. The proposed control algorithm is investigated through computer simulation by using PSCAD/EMTDC software. From simulation the results show a very good compensation for compensating voltage sags.