A New Strategy for Determination of Dc Voltage Levels in Asymmetrical Cascaded Multilevel Converters for Utility Applications

This paper presents a new algorithm for the determination of DC voltage source levels of asymmetric multilevel converters. This technique provides more flexibility to the designer and can generate a large number of levels (odd and even), with minimum number of single-phase full-bridge inverters. This point results in the reduction of switches number, losses, cost of the converter, installation area and the complexity of the control system. Also, modularized circuit layout and packaging is possible. The number of output voltage levels can be adjusted by adding or removing the fullbridge cell. The operation and performance of the proposed multilevel converter has been verified by a single-phase 189 level multilevel converter prototype. This converter has been used in a DVR as an application of this converter in utility. This DVR has been modeled and the simulation results show that it can solve power quality problems such as: voltage sag, voltage swell, unbalanced and distorted voltages, without using any coupling transformer.