Rae-Ho Kwak, “단상 NPC 3레벨 인버터의 효율 개선과 고조파 저감을 위한 새로운 불연속 전압 변조 방식,” 아주대학교 공학석사 학위 논문, 2017. > Paper

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.