A Simple Control Strategy for Balancing the DC-link Voltage of Neutral-Point-Clamped Inverter at Low Modulation Index

C. S. Ma; T. J. Kim; D. W. Kang; D. S. Hyun

A Simple Control Strategy for Balancing the DC-link Voltage of Neutral-Point-Clamped Inverter at Low Modulation Index

Vol. 3, No. 4, pp. 205-214, Oct. 2003

10.6113/JPE.2003.3.4.205

Neutral-Point-Clamped (NPC) inverter

DC-link voltage balancing

the neutral point current

discontinuous PWM (DPWM)

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Abstract

This paper proposes a simple control strategy based on the discontinuous PWM (DPWM) to balance the DC-link voltage of three-level neutral-point-clamped (NPC) inverter at low modulation index. It introduces new DPWM methods in multi-level inverter and one of them is used for balancing the DC-link voltage. The current flowing in the neutral point of the DC-link causes the fluctuation of the DC-link voltage of the NPC inverter. The proposed DPWM method changes the path and duration time of the neutral point current, which makes the overall fluctuation of the DC-link voltage zero during a sampling time of the reference voltage vector. Therefore, by using the proposed strategy, the voltage of the DC-link can be balanced fairly well and the voltage ripple of the DC-link is also reduced significantly. Moreover, comparing with conventional methods which have to perform the complicated calculation, the proposed strategy is very simple. The validity of the proposed DPWM method is verified by the experiment.

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Cite this article

[IEEE Style]

C. S. Ma, T. J. Kim, D. W. Kang, D. S. Hyun, "A Simple Control Strategy for Balancing the DC-link Voltage of Neutral-Point-Clamped Inverter at Low Modulation Index," Journal of Power Electronics, vol. 3, no. 4, pp. 205-214, 2003. DOI: 10.6113/JPE.2003.3.4.205.

[ACM Style]

C. S. Ma, T. J. Kim, D. W. Kang, and D. S. Hyun. 2003. A Simple Control Strategy for Balancing the DC-link Voltage of Neutral-Point-Clamped Inverter at Low Modulation Index. Journal of Power Electronics, 3, 4, (2003), 205-214. DOI: 10.6113/JPE.2003.3.4.205.