Wave basin testing of hydrodynamic interactions in centralized controlled wave energy converter arrays for irregular short- and long-crested waves

Abstract

To increase the total installed capacity, multiple wave energy converters (WECs) will be installed in an array configuration. Within these WEC arrays, hydrodynamic interactions occur and the sea state is modified accordingly. These WECs are equipped with a Power Take-Off (PTO) which converts the kinetic energy of the waves to mechanical energy. An optimal PTO can be obtained by setting the PTO control impedance equal to the complex conjugate of the intrinsic impedance of the WEC. Within a WEC array constituting of n closely spaced WECs, where hydrodynamic interactions between the WECs occur through radiation and diffraction of waves, the n x n PTO control impedance matrix should be equal to the complex conjugate of the n x n intrinsic impedance matrix. This paper discusses the incremental experimental modelling of five ‘WECfarm’ WECs: Modelling of the five isolated WECs, a two-WEC array, a three-WEC array, a four-WEC array, and a five-WEC array. System identification (SID) tests are performed to obtain an accurate dynamic model of the isolated WECs and the WEC arrays. Based on this model, causal impedance matching Proportional (P) controllers are designed, and tested for a selection of irregular long- and short-crested waves. This paper presents the dataset and results of the experimental campaign performed at the Coastal & Ocean Basin Ostend (COB), Belgium. With high measurement accuracy and repeatability, the presented dataset is reliable, while by considering controlled WECs, and operational and extreme wave conditions, it is realistic.