| dc.description.abstract | High-power medium voltage converters face the issues of the network interaction, reliability and efficiency. In addition, 4-quadrant operation is needed for FACTS, distributed generation and regenerative drive systems. This work presents a 24-pulse active-front-end rectifier (AFE) with low switching frequency. The system has four units, each one configured with a three-phase three-level NPC AFE rectifier (3LAFE). The 24-pulse behavior is built by the transformers' connection with ±7.5°-degree displacement at the primary side. For achieving low switching frequency, a modulation pattern based on a selective harmonic elimination PWM technique (SHEPWM) is employed. With only 3 switching angles, the lowest injected harmonic orders are the 47 th and 49th. Simulated and experimental results show the good performance at the mains side with unity power factor and low harmonic distortion. Further reduction of remaining 47th and 49th harmonic orders is discussed. This solution may be applied in high-power regenerative systems like downhill conveyors, mill drives and windmills, allowing the improvement of the overall system efficiency and the reduction of size and cost of large power harmonic filters. | |
