All-electric wave energy Power Take Off system with improved power quality at the grid connection point

Wave Energy Converters (WEC) with all electric Power Take Off (PTO) systems have large fluctuations in output power, and have a peak to average power ratio way beyond most other energy producers. Special care must therefore be taken when designing such systems for power export to grid. This paper focuses on the electrical design of the PTO and how to optimize towards an optimum peak to average ratio for export. The optimization method is based on the possibility to design the electrical machine with a high ratio between nominal speed and maximum speed, termed the overspeed ratio. The design method is implemented into Fred Olsen's point absorber simulation model and run for various overspeed ratios. A full year of production based on a given scatter diagram is simulated and the resulting annual production and load hours is presented. The simulations show that a high overspeed ratio can be beneficial for most direct driven systems.