A wave-photovoltaic self-powered system for ocean data buoys based on multi-unit parallel built-in direct-drive wave energy converters

Ocean data buoys (ODBs) play a crucial role in marine environmental monitoring, weather forecasting, and accident early warning. However, their long-term stable operation is constrained by the energy self-sufficiency problem in the deep-sea environment. To address this challenge, this paper proposes a wave energy-photovoltaic (PV) hybrid power supply system to achieve ODB self-powering. A multi-unit parallel operation control system based on a built-in direct-drive wave energy converter (BD-WEC) is designed within the limited buoy space to enhance wave energy harvesting under buoy-induced motion. The wave energy and PV branches are integrated with a battery charging circuit through a common DC bus, enabling complementary energy collection and stable battery charging. To verify the system performance, a six-degree-of-freedom (6-DOF) experimental platform was built, and hardware tests were conducted on a hybrid generation unit composed of three BD-WECs and PV modules. The experimental results show that the average charging power increases from 15 W under wave-only operation to approximately 112 W after PV integration, corresponding to a daily energy generation potential of 0.75 kWh under the representative operating condition reproduced in the laboratory. These results demonstrate the feasibility of the proposed hybrid system for improving the energy autonomy and power-supply reliability of ODBs.