A new adaptive discharge-path-protection-switch clamped multilevel inverter

Since the initial proposal of the diode clamped voltage source inverter (VSI), various inverter topologies and associated control strategies have been studied. The industrially favored topology has been the multilevel bridge, e.g. 3, 5, 7 levels. Investigations so far have concentrated on the normal operation of the multilevel inverter. It is an accepted practice that the inverter, comprising many semiconductor devices, shuts down in case of any device failure. Shutdown incidents are minimised by providing backup (redundant) devices incorporated in each inverter valve. This paper investigates the robustness of the conventional multilevel VSI topology and the inherent redundancy of the inverter to device failure. Based on this investigation, an adaptive discharge path protection scheme (DPPS) to enhance the VSI robustness is proposed. The paper describes the proposed topology and a performance recovery scheme suitable for high power applications. Experimental results illustrating continual system performance throughout normal and abnormal operating conditions are presented.