New Modulation Strategy to Balance the Neutral-Point Voltage for Three-Level Neutral-Clamped Inverter Systems

• Published in: IEEE transactions on energy conversion Vol. 29; no. 1; pp. 91 - 100
• Main Authors: Choi, Ui-Min, Lee, June-Seok, Lee, Kyo-Beum
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.03.2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Carrier-based PWM (CB-PWM); Electric potential; Harmonic distortion; Inverters; Logic gates; Modulation; Multilevel; neutral-point clamped (NPC) inverter; neutral-point voltage balancing; Passive optical networks; Pulse duration modulation; Reactive power; space vector modulation; Strategy; Switches; Switching; T-type inverter; Vectors; Voltage
• ISSN: 0885-8969; 1558-0059
• DOI: 10.1109/TEC.2013.2293502

This paper proposes a new modulation strategy that balances the neutral-point voltage for three-level neutral-clamped inverter systems. The proposed modulation replaces the P-type or N-type small switching states with other switching states that do not affect the neutral-point voltage. The zero and medium switching states are employed to help the neutral-point voltage balancing. This method little bit increases the switching events and output total harmonic distortion. However, this method has a strong balancing ability at all regions. Further, it is very simple to implement in both space vector modulation and carrier-based PWM methods. Simulation and experimental results verify the validity and feasibility of the proposed new modulation strategy.