LAUSR

This paper proposes a generalized hybrid modulation strategy to extend the operation of asymmetrical cascaded multilevel converters into the overmodulation region during fault conditions on the power cells. The proposed strategy makes use of the advantages of both space vector and carrier-based geometrical modulations to allow the converter to operate with a wide range of modulation indexes and fault conditions. Also, it does not need to precalculate various trajectories for the voltage reference, which would be a very complex task, as the shape of the converter space vector diagram is different for each type of fault condition. It is shown that different kinds of overmodulation can happen during faults on the power cells, and solutions are presented for each mode of operation. Finally, simulation and experimental results are shown to demonstrate the good performance of the proposed modulation strategy.