Multicarrier Interleaved PWM Strategies for a Five-Level NPC Inverter Using a Three-Phase Coupled Inductor

Multicarrier interleaved pulsewidth modulation (PWM) techniques are presented for a five-level neutral point clamped inverter using a three-phase coupled inductor. The inverter operation is demonstrated using a simple multicarrier interleaved PWM algorithm. Since both the inverter and inductor power losses are closely linked to the magnitude of the inductor current ripple, improved multilevel interleaved PWM techniques are presented based upon the concept of interchangeability of switching states in each phase. The proposed PWM techniques, which are easier to implement when compared to multilevel space-vector PWM techniques, also exploit the use of switching states with a high-effective winding inductance to minimize the inductor current ripple. Simulation results are presented to illustrate the improvements obtained in the inverter waveforms and their harmonic spectrum. Experimental results demonstrate how the inductor current ripple and the related power losses are significantly reduced using the proposed PWM scheme.