Four-level neutral point clamped converter with reduced switch count

This paper presents a new topology of four-level neutral point clamped (NPC) converter that is primarily targeted for high-power applications. The proposed topology is favorably compared to the conventional four-level NPC converter topology due to the desired feature of reduced switch count. Furthermore, in relation to the active NPC topology that generates three-level output voltages, the proposed topology features increased number of output voltage levels. For the high-power medium-voltage applications, for which the NPC topology has been consistently chosen as the workhorse, either reduced switch count or increased number of voltage levels bears substantial practical importance in light of the reduced cost, improved reliability, superior waveform quality and minimized filtering requirement. The operating principle of the proposed topology is analyzed in detail. The effectiveness of the modulation and control of the proposed topology is verified by high-fidelity numerical simulation conducted via Sabertrade.