Adaptive phase-shifted PWM for multilevel cascaded H-bridge converters for balanced or unbalanced operation

Among multilevel converters, the cascaded H-bridge topology is one of the most industrially accepted solution for multiple applications, mostly for motor drives and flexible AC transmissions systems. Besides, other applications are being considered taking advantage of its modularity. The conventional phase-shifted PWM is the common method to generate the power devices switching of the converter. However, the performance is poor when an unbalanced operation is present. In this paper, an adaptive modulation method is presented where the angle to be applied to the phase-shifted PWM modulator is not fixed, but it is variable and calculated in real time depending on the operational conditions. Some simulation results are presented in order to demonstrate the good performance of the system.