This paper proposes a discontinuous pulse width modulation (DPWM) method to improve current total harmonic distortion (THD) and achieve high efficiency for a single-phase neutral-point clamped (NPC) three-level inverter. In the most of the single phase systems, the bipolar or unipolar PWM (UPPWM) method is commonly used. However, these PWM methods have the disadvantages in an aspect of the power losses because of many switching operations. The DPWM methods can improve efficiency but increase current THD as well. To reduce these weaknesses, the proposed DPWM method combines two PWM methods, which are the UPPWM and conventional DPWM. Since the proposed DPWM method has all the advantages of both methods, the optimal performance about the power losses and current THD can be obtained. The process to divide optimally operation range of two PWM methods is introduced based on the analysis of the power loss and current THD. The effectiveness of the proposed DPWM method is shown through the simulation and experiments.
