Elimination of low order harmonics in nine-level cascaded H-bridge converter

Abstract

MULTILEVEL converters compare with the conventional two-level converters provide noticeable advantages such as lower harmonic distortion, lower switching frequency, lower switching losses, and lower stress across the semiconductor switches. To improve the output quality of multilevel converters, different modulation techniques have been suggested in the literature. The most suitable modulation technique for high-power high-voltage applications is selective harmonic elimination (SHE) due to having fundamental switching frequency. In this paper, a simple method for elimination of low order harmonics in nine-level CHB converter is proposed. Using this technique, there is no need to solve complex trigonometric equations and therefore, this technique can be implemented in real time using a simple processor. Furthermore, all CHB modules operate at the fundamental switching frequency and power consumption is shared identically among them. To demonstrate the validity of the proposed method, simulation for a three phase nine-level CHB inverter is presented.