Effects of wave excitation force prediction deviations on the discrete control performance of an oscillating wave energy converter

Abstract

Oscillating-body converters are widely used in offshore engineering, to capture wave energies. In such a case, discrete control including both latching and declutching controls is adopted to improve the power capture performance of oscillating wave energy converters (WECs). A reliable prediction of wave excitation forces on the WEC is essential for the discrete control strategy. In this study, a time domain model is developed to calculate the hydrodynamic responses of a hemispherical oscillating WEC with discrete control in regular waves. A state space model is used to deal with the convolution term in the time domain equation, taking into account the memory effects of wave surface. Based on the developed numerical model, the effects of prediction deviations, such as the amplitude and phase of wave excitation force, have been studied. It is observed that the amplitude prediction deviation exhibits very few effects on the control performance. However, the phase prediction deviation performances significantly influence on the control performance. In some conditions, the phase prediction deviation will reduce the efficiency of the discrete control.

Keywords:

• WEC
• discrete control
• prediction deviations
• hydrodynamics

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China [grant number 51239007] and the Independent Research Project of State Key Laboratory of Ocean Engineering in Shanghai Jiao Tong University [grant number GKZD010023]. These supports are gratefully acknowledged by the authors. The first author is also supported by the IPRS, APA and Shell-UWA offshore engineering PhD research top-up scholarships in the University of Western Australia. The third author is supported by the Shell EMI offshore engineering initiative at the University of Western Australia. These sources of support are gratefully acknowledged.