Adaptive Phase-Shifted PWM Strategy With Common-Mode Voltage Reduction for T-Type Three-Level Inverters

The T-type three-level inverters have enormous promise in medium-voltage drives for aircraft electric-propulsion applications. The phase-shifted carrier-based pulsewidth modulation (CBPWM) is a viable solution to reduce the damage caused by the common-mode voltage (CMV) of such inverters. However, the beneficial effect of triangular carrier phase shifting on CMV suppression has not been well explored, and it is still unknown what range of phase shift angles may guarantee CMV suppression for arbitrary modulation index. Therefore, aiming at the T-type three-level inverter, this study offers a thorough examination of the relationship between CMV reduction and the phase-shifted CBPWM approach. The characterization of the maximum CMV is revealed within the full modulation index range based on the sector segmentation and regular sampling. Then, an adaptive phase shift pulsewidth modulation (APS-PWM) strategy is developed to achieve consistent CMV reduction. The maximum CMV of the inverter may be efficiently eliminated under the proposed strategy by dynamic carrier phase shifting. Finally, experiments verify the correctness of the analysis and the feasibility of the proposed strategy.