Evaluating Constant DC Link Operation of Wave Energy Converter

Abstract

A wave energy converter (WEC) based on a linear generator and a pointabsorbing buoy has been developed at Uppsala University. Interconnecting an array of WECs in parallel requires a point of common coupling, such as a common dcbus. The dc voltage level seen by the generator is directly linked to the electromagnetic damping of the generator. A lower dclevel results in a higher damping factor and is important for increased absorption of the wave power. The drawback is increased losses in generator windings and cable resistance. There will be an optimal dclevel for maximum power output. This is a function of not only generator and buoy characteristics, but the current sea state. Experimental results of the fullscale system have been carried out, and used as validation of a simulation model of the system. The model is then used to evaluate how the dclevel seen by the generator influence the power output. The results indicate that higher dclevels should be used at higher sea states, and power output may vary by up to a factor five depending on which dclevel is chosen.