Most Wave Energy Converters (WECs) produce highly distorted power due to the reciprocal motion induced by ocean waves. Some WEC systems have integrated energy storage that overcomes this limitation, but add significant expenses to an already costly system. As an alternative approach, this article investigates the direct export option that relies on aggregate smoothing among several WECs. By optimizing the positioning of the WEC devices with respect to the incoming waves, fluctuations may be mutually canceled out between the devices. This work is based on Fred. Olsen's WEC system Lifesaver, and a WEC farm consisting of 48 devices is designed in detail and simulated. The major cost driver for the electrical export system is the required oversize factor necessary for transfer of the average power output. Due to the low power quality, this number can be as high as 20 at the entry point of the electrical system, and it is thus crucial to quickly improve the power quality so that the downstream power system is efficiently utilized. The simulations undertaken in this work indicate that a high quality power output can be achieved at the farm level, but that a significant oversize factor will be required in the intermediate power system within the farm.

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Power electronics and advanced motion control has allowed for creating Wave Energy Converters (WECs) with the generator directly coupled to the sinusoidal motions of the prime mover. However, this gives large fluctuations in output power, and the resulting peak to average power ratio exceeds most other energy producers. The typical cycle time of ocean waves is 5-7 seconds with subharmonic wave train fluctuations of 30-200 sec. These slow power fluctuations may cause significant thermal cycling of the IGBT powered inverter, with reduction in lifetime as result. In this work the Fred Olsen WEC system is used as a staring point, and a detailed thermal model for the inverter is implemented and simulated. Based on the study of earlier publications on IGBT reliability the resulting lifetime of the system is estimated. This study indicate that thermal cycling may impact on the system lifetime and that some oversizing is required.

Wave Energy Converters (WECs) with direct electric Power Take Off systems have large fluctuations in output power, and have a peak to average power ratio far above most other energy producers. Moreover, the typical average power production from a WEC is lower than that of other power plants, typically less than 1 MW. Array connection of several WECs can mitigate these shortcomings by increasing both the power output and quality. The focus of this paper is to analyze Fred. Olsen designed WEC system Bolt2Wavehub and the effect of expanding to a small array. The required specifications for the array geometry, the electrical configuration and the overall system are discussed and a specific array design consisting of 7 WECs is suggested as a solution and analyzed in detail. The results show that the peak to average power ratio can be reduced by a factor of 4 if the array covers a full wave length.