Seungjong Yoo, “중성점 전압 리플 저감이 가능한 3-레벨 NPC 인버터의 새로운 DPWM 방법,” 아주대학교 공학석사 학위 논문, 2016. > Paper

A new pulse width modulation (PWM) strategy which is an alternative approach of the discontinuous PWM (DPWM) for a three-level

neutral-point-clamped (NPC) inverter is proposed in this paper. A three-level NPC inverter is completely mature and very well

established topology in high-power applications. However, the three-level NPC inverter has the inherent problem of neutral-point

voltage unbalancing due to the split dc-link capacitors. This structure can cause the large neutral-point voltage ripple. Furthermore,

output currents of the three-level NPC inverter can be distorted by the neutral-point voltage ripple. Since the influence of the

neutral-point voltage ripple to output, it must be controlled. In this paper, a new DPWM method using two different offsets for the

neutral-point ripple reduction is proposed and the effectiveness of the proposed DPWM method is verified by using the simulation

and the experimental results.