June-Seok Lee, Raeho Kwak, and Kyo-Beum Lee, "Novel Discontinuous PWM Method for a Single-Phase Three-Level Neutral Point Clamped Inverter with Efficiency Improvement and Harmonic Reduction," IEEE Transactions on Power Electronics, vol. 33, no. 11, pp. 92 > Paper

This paper proposes a novel discontinuous pulse-width modulation (DPWM) method to reduce the current harmonics and improve

the system efficiency for a single-phase three-level neutral-point clamped inverter. In single-phase inverters, the unipolar pulse-width

modulation (UP-PWM) method is commonly used. However, this method has the disadvantage of power losses due to numerous

switching operations. Conventional DPWM methods reduce the power losses and improve efficiency but increase the current total

harmonic distortion (THD). To overcome these weaknesses, this paper proposes a hybrid DPWM switching method combining two

PWM methods: the UP-PWM method and the conventional DPWM method called one-pole clamped PWM method. Since the

proposed DPWM method offers all the advantages of both PWM methods, the optimal performance-with regard to the power losses

and current THD-is obtained. The combination of two PWM methods is investigated by analyzing the power losses and current THD.

Based on the analysis, the process determining the optimal operating condition is introduced. The effectiveness of the proposed

DPWM method is demonstrated through simulations and experiments.