A new link potential control scheme for four-level inverter with passive rectifier

Multi-level inverters have been attracting increasing attention in recent years and have been selected in several high voltage and high power applications. Especially, for high power variable speed applications, the diode clamped configuration multi-level inverter has been widely used. However, the diode clamped configuration inverter has the inherent problem that the potential of the link capacitor fluctuates. This paper describes a carrier-based SVM (space vector modulation) method to effectively suppress the DC link potential fluctuation for the diode clamped four-level inverter. The current to flow from/into each link capacitor is analyzed and the operation limit is obtained when a conventional carrier-based SVM method is used. To overcome the operation limit, a modified carrier-based SVM method is proposed. Various simulation results by means of Matlab/Simulink are presented to verify the proposed carrier-based SVM method.