The active NPC converter for medium-voltage applications

The three-level neutral point clamped voltage source converter (NPC VSC) is widely used in high-power, medium-voltage applications. To overcome its major drawback - the unequal loss distribution among the semiconductors - the use of active NPC switches (ANPC) was proposed previously. In this paper, a simple feedforward loss-control scheme for the ANPC converter is presented. The principle of operation of the ANPC VSC is verified experimentally 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. Finally, the authors demonstrate the superior performance of the ANPC converter in various medium-voltage applications.