Hybrid Space Vector PWM Control to Reduce Common-Mode Voltage for Three-Level T-NPC Inverter under Switch-Open-Circuit Fault

Abstract

This paper proposes a hybrid space vector PWM technique (HSVPWM) that combines conventional SVPWM with virtual SVPWM to reduce common-mode voltage in a three-level T-NPC inverter operating under a switch-open-circuit fault in the neutral-point-connected switch of phase A. First, the concept of virtual space vector is introduced. Subsequently, the space vector diagram is re-divided into regions, and the nearest three vectors for each region are reselected. The proposed method is analytically investigated and then validated through both simulation and experimental implementations. Furthermore, the measured voltage waveforms are evaluated in terms of total harmonic distortion (THD) and weighted-total harmonic distortion (WTHD) to verify the effectiveness of the proposed algorithm. Simulation results demonstrate that the proposed HSVPWM strategy can reduce the THD and WTHD of $\mathrm{v}_{\mathrm{AB}}$ and $\mathrm{v}_{\mathrm{CA}}$ by up to $15 \%$ compared with the previous study SVPWM2 method, within the modulation index range of 0.4 to 0.8.