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A Neutral-Point Voltage Balance Controller for the Equivalent SVPWM Strategy of NPC Three-Level Inverters

  • Lyu, Jianguo (School of Automation, Nanjing University of Science and Technology) ;
  • Hu, Wenbin (School of Automation, Nanjing University of Science and Technology) ;
  • Wu, Fuyun (College of Mechanical and Electrical Engineering, Sanjiang University) ;
  • Yao, Kai (School of Automation, Nanjing University of Science and Technology) ;
  • Wu, Junji (School of Energy and Power Engineering, Nanjing University of Science and Technology)
  • Received : 2015.08.10
  • Accepted : 2016.07.20
  • Published : 2016.11.20

Abstract

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

Acknowledgement

Supported by : Jiangsu Natural Science Foundation, National Natural Science Foundation of China

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