First results from wave tank testing of different control strategies for a point absorber wave energy converter

In recent years many advanced control strategies have been proposed for wave energy converters, which significantly increase the energy conversion rate of the devices. So far most of these control schemes have only been investigated theoretically using simulations, which to a great extend are based on idealized assumptions. On the contrast, far less information regarding the testing of these control schemes in real life environments can be found. Under such circumstances, the control performance might be compromised by many factors such as model uncertainties, measurement noise or -delay. This paper compares the performance of a state-of-the-art control and an advanced control strategy for a point absorber wave energy converter in wave tank experiments. For two different irregular sea states, the energy conversion of the advanced control, which uses an observer to estimate the wave excitation force, is compared to the performance of a spring damper control. The results show that with the advanced controller around 13-14% more energy could be converted when compared to the spring damper control. Additionally, the observing process was found to be critical in the advanced control, since an increase in the observer accuracy also improves the energy conversion rate.