Power electronic grid-interface for renewable ocean wave energy

This paper presents information on ocean wave energy converters and power electronics grid-interface. In the introduction a basic terms and methods of ocean wave energy capture are discussed. Further several most important ocean wave energy conversion prototypes are briefly described. The generators and power electronics solutions for Power Take Off (PTO) system are presented on the example of Wave Dragon MW ocean wave energy converter. The Wave Dragon MW captures power from the ocean waves by means of low-head Kaplan turbines and converts it into rotating mechanical power. Problems which can appear in mechanical power to electrical power conversion in Wave Dragon MW can be expected to be similar as in wind turbine. However, subject of the mechanical energy conversion from ocean waves to electrical energy is not well identified and further research should be carried out. Additionally, specific problems of AC-DC-AC grid-interfacing converters under grid voltage distortions — including grid impedance estimation, higher harmonics and voltage dips compensation — are discussed. Some simulated and experimental oscillograms that illustrate properties of the presented systems are shown.