Equalization of Losses in a Multilevel Frequency Converter in Fault Condition

The cascaded multilevel frequency converter is one of the most used topologies of medium voltage drives. One of the main advantages of the topology is the ability to decommission any failed cell without interrupting the operation of the drive. The PWM technique with walking cell adapts to a different number of cells in the phase. However, in case of cell failure, the switching losses of each cell in the phase grow with respect to other healthy phases. This paper considers the strategy for equalization of switching losses of all cells of the frequency converter in faulty conduction. The proposed strategy was verified using a model in Matlab Simulink and losses were estimated in PSIM.