Comparative study of the efficiency and power density of offshore WECS with three-phase AC-link

In this paper three converter topologies are compared for the AC-AC conversion stage of an offshore wind turbine with permanent magnet synchronous generator. The WECS (Wind Energy Conversion System) is based on four stages: an input filter, an AC-AC converter, a three-phase high-frequency transformer and a full-bridge diode rectifier. The conventional back-to-back converter, the matrix converter and the indirect matrix converter are the three selected topologies. Analytical models and numerical simulations are considered in order to evaluate the WECS efficiency and power density as a function of the operational frequency of the transformer. It was found that for range of transformer frequencies from 100[Hz] to 10[KHz], the direct matrix converter topology was the most efficient topology and had the highest power density. In general, the back-to-back converter topology presents the lowest efficiency and power density in the range of frequencies considered.