Diode‐Clamped Multilevel Inverters

The diode‐clamped multilevel inverter employs clamping diodes and cascaded DC capacitors to produce AC voltage waveforms with multiple levels. This chapter discusses various aspects of the three‐level (3L) neutral‐point clamped (NPC) inverter, including the inverter topology, operating principle, and device commutation. It also discusses a conventional space vector modulation (SVM) scheme for the NPC inverter. The DC input voltage of the inverter is normally split by two cascaded DC capacitors, providing a floating neutral point. The chapter elaborates control of the neutral‐point voltage deviation and introduces the operation of four‐ and five‐level diode‐clamped inverters with carrier‐based modulation techniques. The neutral‐point voltage can be controlled by adjusting the time distribution between the p‐ and n‐type states of a small voltage vector. There always exists a small voltage vector in each switching sequence, whose dwell time is divided into two sub‐periods, one for its p‐type and the other for its n‐type switching state.