Transformer-Less Dynamic Voltage Restorer Employing an Asymmetrical Seven-Level Inverter with Reduced Number of Switches for Improving Power Quality

Abstract

In modern power system, power quality is one of the major concerns. It has become important, especially with the introduction of smart grid, grid-connected renewable energy systems and sophisticated devices, whose performance is very sensitive to the quality of power supply that results in a failure of end-use equipment. One of the major power quality disturbance dealt here is the voltage sag. To solve this problem, custom power devices are used. One of those devices is the dynamic voltage restorer (DVR), which is the most efficient and effective modern custom power device used in power distribution networks. In this paper, a transformer-less DVR based on the modified asymmetrical multilevel inverter is proposed. This multilevel inverter uses reduced number of switches. As a result, the proposed DVR has lower number of switches in comparison with other multilevel-inverter-based DVR topologies. Also, it has lower loss and cost due to no need for injection transformers. Its appeal includes lower cost, smaller size, and its fast dynamic response to the disturbance. It can provide the most economical solution to mitigation voltage sag by injecting voltage as well as power into the system. The performance of the proposed model is simulated in MATLAB/Simulink environment.

Keywords: voltage sags, dynamic voltage restorer (DVR), asymmetrical multilevel inverter.