Real-Time Optimization Strategy to Minimize Switching Losses for Three-Level NPC Inverter

This paper proposes a real-time optimization strategy, aimed at minimizing switching losses in a three-level neutral-point-clamped (3L-NPC) inverter. The proposed strategy consists of optimized clamping strategy and unified triangular carrier based discontinuous pulse width modulation (DPWM) strategy. In each control period, the optimized clamping strategy determines optimal clamped phases and voltage levels to clamp the phase with absolute current as big as possible. Based on obtained optimal results, unified triangular carrier based DPWM strategy calculates the injected common mode voltage (CMV) and generates driving signals for semiconductor switching devices by comparing final modulation signals and two phase-deposited carriers. Analysis and experiment results show the proposed strategy not only can reduce switching losses up to 49.8% compared with conventional space vector PWM (SVPWM) but also has features of low computation burden and easy implementation.