A new scheme for multilevel inverter based dynamic voltage restorer

In this paper, a new scheme for the multilevel inverter based dynamic voltage restorer (DVR) is proposed. The proposed DVR uses multilevel inverter and a dc/dc converter. The dc/dc converter adjusts the dc link voltage according to the amount of voltage sag so that the output voltage of the multilevel inverter has always its maximum possible number of levels. This results in the better quality of output voltage in both deep and shallow voltage sags. It is important to emphasize that the existing multilevel inverter based DVR topologies have not this capability. The mathematical analysis of operation range of the proposed DVR is given by details. The simulation results using PSCAD/EMTDC as well as the experimental results from a laboratory prototype verify the proposed DVR scheme.