The Transactions of the Korean Institute of Power Electronics (전력전자학회논문지)

The Korean Institute of Power Electronics (전력전자학회)
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A Small Signal Modeling of Three-level Neutral-Point-Clamped Inverter and Neutral-Point Voltage Oscillation Reduction

3레벨 NPC인버터의 소신호 모델링과 중성점 전압 진동 저감

  • Cho, Ja-Hwi (Dept. of Adavnced Power Conversion System Eng., Hanyang University) ;
  • Ku, Nam-Joon (Dept. of Electrical Eng., Hanyang University) ;
  • Joung, Seok-Eon (Dept. of Electrical Eng., Hanyang University) ;
  • Hyun, Dong-Seok (Dept. of Electrical Eng., Hanyang University)
  • Received : 2014.05.07
  • Accepted : 2014.07.13
  • Published : 2014.10.20
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Abstract

This study proposes a control design for the grid output current and for reducing the neutral-point voltage oscillation through the small-signal modeling of the three-phase grid connected with a three-level neutral-point-clamped (NPC) inverter with LCL filter. The three-level NPC inverter presents an inherent problem: the neutral-point voltage fluctuation caused by the neutral-point current flowing in or out from the neutral point. The small signal modeling consists of averaging, dq0 transformation, perturbing, and linearizing steps performed on a three-phase grid connected to a three-level NPC inverter with LCL filter. The proposed method controls both the grid output and neutral-point currents at every switching period and reduces the neutral-point voltage oscillation. The validity of the proposed method is verified through simulation and experiment.

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References

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