Multi-carrier interleaved PWM strategies for a new five-level NPC inverter using a 3-phase coupled inductor

Multi-carrier interleaved PWM techniques are presented for a new five-level Neutral Point Clamped (NPC) inverter using a 3-phase coupled inductor. The operation of the proposed topology relies on the dual requirements of balancing the DC bus capacitor voltages and the inductor common mode currents together. The inverter performance is dependent on the PWM strategies minimizing the inductor current ripple and associated inductor losses. The inverter operation is verified by a simple multi-carrier interleaved PWM algorithm. An improved multilevel interleaved PWM technique is developed based on interchangeable switching states in each phase. The proposed method exploits the use of switching states with a high-effective inductance to minimize the inductor current ripple. The new approach is easier to implement compared to multi-level space vector PWM techniques. The drive operation with the proposed PWM schemes is demonstrated using simulation and experimental results. The inverter performance has been significantly improved by lowering the inductor losses.