A new neutral point current control for a 3-level converter/inverter pair system

This paper describes the analysis of the neutral point (mid-point) potential variation in the 3-level SVPWM converter and inverter, and proposes a mid-point current controller (MPCC). The variation of the mid-point potential is analyzed in detail with the focus on the current flowing out of or into the mid-point with the proposed SVPWM method. The authors show that the 3-level converter and inverter could be controlled to have no mid-point potential fluctuation by the MPCC. But, both the 3-level converter and inverter have the control limitation. In the converter/inverter pair system, however, the limitation could be overcome with the MPCC. The validity of the proposed method is demonstrated by the simulation results using Mablab/Simulink.