An Overall Minimized Switching Loss Discontinuous PWM Strategy for Neutral Point Clamped Three Level Inverters

Abstract

Aim at reducing switching loss (SL) of neutral-point clamped three-level inverter (NPC TLI) as much as possible, a novel SL minimized discontinuous pulse width modulation (SLMDPWM) strategy is proposed in this paper. The core of SLMDPWM is that the specific maximum or middle phase current is clamped to positive bus, NP or negative bus according to modulation index and power factor angle. The realization of SLMDPWM based on carrier-based PWM (CBPWM) is revealed to simplify the calculation process. The performance characteristics of SLMDPWM and DPWM I-IV in term of the output voltage, SL and NP voltage ripple are compared by simulation and experimental results, and conclusion can be acquired that the SL of SLMDPWM is reduced significantly.

Keywords

• Discontinuous modulation strategy
• neutral-point clamped three-level inverter
• neutral-point voltage
• switching loss