Cascaded U-Cell multilevel converter for STATCOM applications

Cascaded H-bridge (CHB) converter is one of the popular solution for medium voltage transformerless static synchronous compensator (STATCOM) applications. The semiconductor devices of this converter are switched at low frequency. Therefore, conduction losses contribute to major part of the losses in this converter. To reduce the conduction losses, a cascaded U-cell (CUC) multilevel converter is derived from CHB converter. The proposed converter has less number of switches compared to CHB converter and therefore reduces the overall losses of the converter. Converter circuit topology, control strategy and simulation results for static var compensation are presented. The losses are estimated and compared with that of CHB converter to verify the reduction of overall losses in proposed converter.