Carrier PWM algorithm for multileg multilevel inverter

This paper presents a universal carrier based PWM method for multileg multilevel inverter on consideration of unbalanced dc voltage sources. Switching time diagram of PWM control in multilevel inverter can be transformed into a nominal switching two-level diagram. It will be shown the correlation between space vector PWM and carrier based PWM methods. As a result, space vector PWM and carrier based PWM methods are only two approaches for implementing defined switching state sequences in multileg multilevel inverters. The described generalized PWM approach for multileg multilevel inverters can be properly applied to different inverter topologies without difficulties. The proposed method is based on modifying of the modulating signals, depending on the dc-source variation. The additional common mode voltage can be designed for obtaining required PWM performance.