An Optimal PWM Selection Strategy for Three-Level NPC Converter in a Wide Operating Range

In Three-Level Neutral-Point Clamped (NPC) converters, selected PWM will affect the following performance aspects of the system: system losses, power quality and Neutral Point (NP) voltage fluctuations. The existing PWM methods offer significant advantages in specific performance aspects but cannot ensure optimal performance across a wide range of operating conditions (modulation index and power factor). In this paper, an optimal PWM selection strategy is proposed, which selects the optimal PWM based on key performance metrics. The results indicate that no single PWM method can achieve optimal performance under all operating conditions. Under the trade-off among these performance metrics, NTV2 is the optimal choice under lower power factors, while NTV is the optimal PWM method at higher power factors.