Mitigation of noneliminated harmonics of SHEPWM three-level multipulse three-phase active front end converters with low switching frequency for meeting standard IEEE-519-92

Abstract

Three-level NPC active-front-end three-phase (3LAFE) converters can be applied to high-power medium voltage applications, with 4-quadrant unity-power-factor operation, allowing a broad range for power conversion systems, such as decentralized energy distribution and utilization. Switching losses and network interaction limit the operation of 3LAFE high-power converters, especially when GTO-converters are used. That is why, low switching frequency and reduced harmonic distortion are the main goals when using optimum pattern PWM where selective harmonic elimination modulation method (SHEPWM) is used. This paper introduces a simple method to choose a good operating point for two 3LAFE converters in a 12-pulse configuration based on the behavior of noneliminated harmonics by SHE method. A complete characterization is given as a base of SHE and the optimization criteria is fully explained.