Nonlinear Vector Current Source for theControl of Permanent Magnet SynchronousGenerators in Wave Energy Applications

Abstract

A current source with a space-vector hysteresis band and a constant switching frequency has been designed to be used with surface-mounted permanent magnet synchronous generators. Its fast response makes it very suitable to carry out the precise control necessary in wave energy converters (WEC). These systems are characterised by large variations of speed, torque (or force) and frequency which means that the control has to cope with large variations of voltage and current and also with persistent periods where these variables present low values. The control system takes into account both rotation direction (or displacement direction, when a linear generator is considered) and electrical sequences, something necessary in WEC such as point absorbers. The algorithm was successfully tested in the laboratory using an ad hoc built emulator, that reproduces the behaviour of an oscillating water-column-based WEC. The emulator was built using a similar hardware to those used in equivalent real systems.