Feedforward Loss Control of Three-Level Active NPC Converters

The three-level neutral-point-clamped voltage-source converter (NPC VSC) is widely used in high-power medium-voltage (MV) applications. To overcome its major drawback - the unequal loss distribution among the semiconductors - the use of active NPC (ANPC) switches was previously proposed. In this paper, a simple feedforward loss-control scheme for the ANPC converter is presented. The principle of operation of the ANPC VSC is experimentally verified for the first time. Electrical measurements on a low-voltage test bench prove the proper function of the ANPC converter. Infrared junction temperature measurements confirm the improved loss distribution using the new loss-control scheme. Finally, the authors demonstrate the superior performance of the loss-controlled ANPC converter in various MV applications.