An MVPWM based method for three-level T-type inverter with neutral point voltage balancing capability in the full range of power factor

Abstract

The conventional MVPWM method generates the reference voltage with medium and V0[OOO] zero vectors to remove the common-mode voltage (CMV) which, in turn, mitigates motor bearings damage, electromagnetic interference, and etc. However, it cannot balance the neutral point (NP) voltage that is effective in power quality and inverter lifetime. In this paper, a novel MVPWM based method for the three-level T-type inverters is proposed to simultaneously remove the CMV and keep the NP voltage balanced for the full range of the power factor. The proposed method applies MVPWM switching patterns to control the three-level T-type inverter operation in the balanced condition of NP voltage. Moreover, it employs novel switching patterns in the case of NP voltage unbalancing that can modify the duration of O state connection of inverter phases to change the direction of average NP current and balance the NP voltage. Noteworthy, that the proposed method applies these novel switching patterns with concurrent consideration of the capacitor voltages and phase currents condition (positive or negative) to extend the NP voltage balancing capability to the full range of the power factor. The simulation study has been accomplished and its results demonstrate the effectiveness of the proposed method.