Power Conversion With a Magnetically-Geared Permanent Magnet Generator for Low-Speed Wave Energy Converter

This article presents power conversion and control of a novel low-speed radial-flux magnetically-geared permanent magnet generator (MGPMG) for wave energy conversion. The generator designed and developed by ABB Corporate Research has a magnetic-gear integrated into the structure, which amplifies the low speed of a wave energy converter (WEC) to a high speed of a rotor facing the stator windings. The generator is designed with a large number of magnet poles and concentrated windings for a simpler and cost-effective design. However, due to the concentrated windings, the induced voltage contains a significant percentage of the harmonic component, which leads to the generation of harmonic power. The impact of the harmonic power on power conversion circuit design and ways to mitigate the effect is discussed. The power conversion system and controls are designed to experimentally verify the operation of a prototype 10-kW 30-r/min MGPMG, which is driven by an induction motor emulating the dynamics of an oscillating rotary WEC. Experimental results of power conversion including harmonic power, efficiency analysis, and energy storage integration are reported.