Construction and control of an air-cored permanent magnet linear generator for direct drive wave energy converters

Direct drive wave energy converters using linear generators are attractive due to their high efficiency and reliability. Air-cored generators in particular are receiving increasing attention due to the elimination of attraction forces between the stator and translator and the resulting reduction in structural mass. In this paper, details of the construction of a novel air-cored linear generator are presented. A custom test rig is constructed for testing the generator, particularly with zero overlap between its stator and translator at the stroke ends. Predictive control for maximum power transfer from the generator is first proposed and tested as an alternative to methods employing linear position feedback and EMF estimation with sense coils. The control strategy is demonstrated to work correctly and it is shown that zero overlap at the stroke ends improves power generated per translator mass compared to complete stator-translator overlap during the entire stroke.