Comparison of wind energy conversion systems based on high frequency AC-Link: Three-phase Vs. single-phase

In this paper is presented a comparison of three converter topologies based on high-frequency link for offshore wind turbines with permanent magnet synchronous generator. The scheme of the wind energy conversion system considered is based on three stages: an AC-AC converter, a high-frequency transformer and a full-bridge diode rectifier. The incidence of the number of phases in the AC link of the power converter is investigated in terms of the efficiency and the power density. The conventional Back-to-Back converter with three-phase (sinusoidal and square wave output) and single-phase square wave output are the chosen topologies for comparative study. It has been found that AC-Link with three-phase square wave will lead the best solution with the more convenient tradeoff between efficiency and power density in the range of frequencies considered (100 Hz-50 kHz). A convenient increase in the power density can be obtained if the number of modules in the modular power converter is optimized.