An Optimized DPWM With Reduced Leakage Current for Three-Phase Three-Level Inverters With Unbalanced Neutral-Point Voltage

Leakage current causes alternating output current distortion and severe electromagnetic interference in photovoltaic generation systems. This article proposes an optimized discontinuous pulsewidth modulation (O-DPWM) method to reduce leakage current in three-phase three-level inverters under various neutral point (NP) voltage conditions. First, the relationship between common-mode voltage (CMV) and leakage current is revealed. Then, the CMV characteristics of space vectors under different NP conditions are analyzed, and the switching-state sequence is optimized to minimize CMV magnitude, thereby reducing leakage current. Furthermore, by clamping the switching state of one phase in each switching cycle, switching losses are also reduced. Finally, a 3-kW grid-tied inverter prototype is built, and experimental results demonstrate that the proposed O-DPWM scheme achieves lower leakage current and higher efficiency compared to existing reduction schemes across different NP voltage conditions.