Abstract
The development of wave energy is crucial for achieving carbon neutrality. Existing power take-off (PTO) systems of wave energy converters (WECs) and maximum power point tracking (MPPT) algorithms still have deficiencies in improving power capture and energy conversion efficiency. This study proposes a novel multi-stage hybrid energy storage WEC system that innovatively integrates hydraulic and mechanical energy storage via accumulators and a flywheel, markedly enhancing power generation stability. The numerical relationship between motor displacement and wave frequency is derived, revealing that an optimal displacement exists to maximize the captured power by achieving system resonance. A hysteresis comparison-based MPPT algorithm is proposed, which adjusts the motor displacement using a variable step-size rule to achieve autonomous tracking of the maximum power point (MPP). Simulation and experimental results show that, under regular wave conditions with a wave period of 7 s and a wave height of 1.75 m, the proposed MPPT control increased the captured power by 33.5%. Under regular wave experiments with a wave period of 3 s and a wave height of 0.2 m, the captured power improved by 31.8%. This study provides theoretical and technical support for the efficient utilization of wave energy and the engineering application of large-scale WEC.