A Carrier-Based Discontinuous PWM Method to Suppress Leakage Current and Reduce Switching Loss for T-Type Three-Level Inverters

In non-isolated three-level inverter applications, the leakage current caused by common-mode voltage (CMV) leads to personal safety hazards. In non-isolated three-level inverters, there are leakage current loops, which can lead to equipment efficiency degradation and pose personal safety hazards. The common-mode voltage (CMV), as the primary excitation source for generating leakage currents, can be suppressed to mitigate these effects. Targeting the limitation that current research cannot further suppress CMV while also considering switching loss, this paper proposes a carrier-based discontinuous pulse width modulation (CB-DPWM) method applicable to all three-level inverters, using the T-type three-level inverter (T²LI) as a case study. Compared to existing leakage current suppression methods, the CB-DPWM method enhances leakage current suppression by further reducing the overall variation range of CMV within a single switching cycle. Additionally, switching loss is effectively minimized through a five-segment sequence that avoids any redundant switching actions. Furthermore, the modulation method, being based on carrier modulation, is easier to implement and offers greater flexibility. Finally, the feasibility and superiority of the proposed method are verified by simulation and experiment.