Improved common-mode voltage elimination modulation with dead-time compensation for three-level neutral-point-clamped three-phase inverters

This paper presents a detailed analysis of the impact of “dead time” (DT) on the EMI performance of three-level neutral-point-clamped (3L-NPC) converters using common-mode voltage elimination (CME) modulation, proposing an improved CME modulation method to compensate for this. The implementation method of CME modulation is presented and the benefits and drawbacks are discussed, showing that the benefit of CME modulation is highly related to the DT added to the system, which makes it less practical. The effect of DT on CM voltage generation is then quantified by analyzing the switching states of one phase-leg. This knowledge is used to develop an improved CME modulation method, which has as main feature the proper selection of space vector sequences taking into consideration the current direction of the three phases. This analysis is verified using simulation results and validated using experimental tests conducted with a 2.5 kW 3L-NPC inverter prototype.