A Novel Carrier-based PWM Method for 3-Level NPC Inverter Utilizing Control Freedom Degree

In this paper, a novel carrier-based PWM method for 3-level NPC inverter utilizing control freedom degree (CFD) is proposed. The method takes advantage of the CFD of carrier amplitude, vertical offsets between carriers and injecting zero sequence voltage. This is achieved in real-time by using the information of dc-link voltages and output currents. Compared with the traditional PWM method, the proposed novel carrier-base PWM method shows better harmonic characteristics, higher dc-link voltage utilization ratio and better neutral-point balance capability. Simulation and experimental results verify the effectiveness of the proposed method.

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