Performance of Dynamic Voltage Restorer (DVR) against Voltage Sags and Swells Using Space Vector PWM Technique

Due to increasing complexity in the power system, voltage sags are now becoming one of the most significant power quality problems. Voltage sag is a short reduction voltage from nominal voltage, occurs in a short time. Short-lived voltage sags may not cause much harm other than cause a slight flickering of lights; temporary voltage sag is bound to have a greater impact on the industrial customers. If the voltage sags exceed two to three cycles, then manufacturing systems making use of sensitive electronic equipments are likely to be affected leading to major problems. It ultimately leads to wastage of resources (both material and human) as well as financial losses. The increasing competition in the market and the declining profits has made it pertinent for the industries to realize the significance of high-power quality. This is possible only by ensuring that uninterrupted flow of power is maintained at proper voltage levels. Electric utilities are looking for solutions to ensure high quality power supply to their customers. This can solve by using custom power devices such as Dynamic Voltage Restorer (DVR), Distribution Static compensator (D-STATCOM) and Uninterruptible Power Supply (UPS). The Dynamic Voltage Restorer appears to be an especially good solution in the current scenario. Two pulse width modulation-based control techniques, viz. sinusoidal PWM and space vector PWM, are presented for controlling the electronic valves in two level Voltage Source Converter (VSC) used in the DVR system. The simulation study of space vector PWM technique for DVR is compared with sinusoidal PWM. Simulations are carried out through PSCAD/EMTDC.