MMC-BASED TRANSFORMER-FREE WIND POWER GRID-CONNECTED TOPOLOGICAL STRUCTURE

摘要

A MMC-based transformer-free wind power grid-connected topological structure comprising a wind-powered electric generator, a rectifier module, and an inverter module. The generator generates a low-voltage alternating current (AC) to be rectified by the rectifier module into a direct current (DC); the DC in turn is used as a DC side voltage power supply for an inverter module power unit. An AC inverted from the DC and connected in series by the power unit is outputted by the inverter module from an AC side through a buffer inductor (L) and integrated into a power grid. An advantage of this being, by connecting in series the power units to produce a high voltage current output, the elimination of a boosting transformer commonly employed in a wind power grid-connection, thereby greatly reducing costs. In addition, by using multiple power units connected in series for the high voltage output, a modulation algorithm can be used for a multilevel waveform output, thus reducing output harmonics content and wind power contamination to the power grid.