A cross connected submodule topology for hybrid multilevel converters

The fault tolerant multilevel converters are being used in HVDC systems due to their ability to suppress the fault current during DC side faults. However most of these topologies uses full bridge submodules which will increase the number of semiconductor switches required in the converter. This paper describes the possibility of using a cross connected submodule structure instead of full bridge submodules. A generalised structure of the cross connected submodule is presented in this paper and the number of switches required in various topologies is compared. The proposed extended configuration of cross connected submodule reduces the number of semiconductor switches used in the converter, and hence reduces the switching loss. The performance of the fault tolerant hybrid multilevel converter topologies with the cross connected submodules is studied and their fault tolerant capability is tested with the simulations done in PSCAD/EMTDC.