Optimal Current Ripple PWM for Three-Level Inverter With Common Mode Voltage Reduction
Xi Liu, Xiangyang Xing, Jie Chen, Changwei Qin, Xiaoyan Li, Chenghui Zhang, Alian Chen
Abstract
Three-level inverter has been widely used in electric drives and renewable power generation system. However, the common mode voltage (CMV) and output current ripple reduction of a three-level inverter should be carefully regulated for the appropriate operation. As these two targets are mutually interrelated, the conventional space vector modulation (SVM) scheme cannot cope with them decently. To overcome this drawback, this article proposes a novel modified SVM scheme to realize CMV and current ripple reduction simultaneously. The generating mechanism of output current ripple is analyzed, and the relationship between current ripple and utilized vectors is quantitatively described. Based on the analyses, the proposed optimal current ripple and CMV reduction pulsewidth modulation (OCR-CMVRPWM) method adopts four voltage vectors (large, medium, small, and zero vectors) to reduce the root mean square value of current ripple by allocating the sequence and dwell times of utilized vectors. Compared to the existing PWM methods, the proposed OCR-CMVRPWM scheme can reduce the peak of CMV to half of the value using the conventional SVM, and obtain a significant reduction of output current total harmonic distortion. The effectiveness of the proposed method is validated by both simulation and experimental results.