A Modified DPWM With Neutral Point Voltage Balance Capability for Three-Phase Vienna Rectifiers

Compared with continuous pulsewidth modulation (PWM), discontinuous PWM (DPWM) is a preferred solution in high-frequency Vienna-type rectifiers due to its inherent characteristics of less commutation number and higher efficiency. In this article, redundant clamping modes at the same subsector with opposite effects on the neutral point (NP) voltage are presented. Then, a modified DPWM (MDPWM) scheme is proposed to regulate the NP voltage by using redundant clamping modes. Thus, the NP voltage can be controlled in each switching period to lower the NP voltage fluctuation. The implementation of the proposed MDPWM is given with variable power factors analysis. Further, the switching loss comparison of conventional space vector PWM (SVPWM), hybrid DPWM (HDPWM), and proposed MDPWM is presented as well. A simulation model was built to verify the proposed NP voltage balance with different modulation indices and variable power factors. Finally, a 10-kW prototype is built to evaluate the proposed MDPWM scheme at conversion efficiency and current total harmonic distortion (THD). Experimental results and analysis show that comparing conventional SVPWM and HDPWM, the efficiency of MDPWM is the highest. The THD of DPWM is slightly higher than that of SVPWM, and it is only 2.5% at rated output power.