Design of a Linear Electrical Machine for a Wave Generation System in the Maltese Waters

Abstract

This research concerns the design of an electrical machine that shall be implemented on a wave energy converter (WEC). Analysis of the available wave data and optimisation of the WEC were carried out so as to design the optimum system that will interact efficiently with the conditions of the selected location. The electrical model was designed for wave heights and periods that yielded the maximum power throughout the year. The initial finite element simulations were undertaken on the design of a four-pole tubular permanent magnet (PM) linear synchronous machine. The performance of the system was optimised for a wave height and period of 3 m and 6 s, respectively. The capacity of the linear generator was set at 15 kVA and the dimensions of the WEC (floating point absorber) were determined accordingly through the application of a simplified model for predicting the coupled dynamic response of the absorber and the linear generator. It was necessary for the electrical machine to yield good performance even when operating under the slower and most common waves. Thus, an 8-pole and a 16-pole tubular linear PM machine were also simulated, and their performance was compared. Through this analysis, the 16-pole design resulted in the best performance, especially at low speeds. Simulations were initially compared at fixed speed but were later simulated with variable speed conditions so as to represent more accurately the wave’s motion and monitor the power generator performance at variable loadings.