Maximizing Energy Extraction from Direct Grid Coupled PMSG For Wind Energy Conversion Systems

Abstract

Direct grid coupling of permanent magnet synchronous generators (PMSG) for wind energy conversion systems (WECS) provides certain advantages with the penalties of maximum power point tracking (MPPT) and reactive power control. This paper proposes a novel PMSG design philosophy such that optimizing PMSG design at the initial stage would compensate for the drawbacks arising from the lack of an MPPT algorithm. Also, the ability to maintain a high power factor across a wide range of operating power levels is investigated by considering reactive power in the design process. In this study, optimization of slot/pole combination is described for direct grid coupled PMSGs to extract as much energy as possible according to wind data. A new benchmark, adequacy factor, is presented to determine the slot/pole combination. Variation of the reactive power is theoretically analyzed. A relationship is established between induced electromotive force (EMF), synchronous inductance values of machines, and the power factor. Fixed and variable speed operations of PMSGs are compared in terms of annual energy yield. Finally, theoretical analyses are validated through laboratory testing of prototype generators.