Abstract
To realize efficient broadband wave-energy conversion, this study proposes a point-absorber wave energy converter with a novel magnetic tristable mechanism (NMT-PAWEC). The tristable mechanism consists of coaxial inner and outer magnetic rings. The outer magnetic ring features two types of sector magnets with opposite poles. The motion control equations of the NMT-PAWEC are established using the Cummins equation and the equivalent magnetic charge method. The preferred parameter region of the novel tristable mechanism was investigated, and the energy-conversion performance of the NMT-PAWEC under regular waves was analyzed. The results show that the NMT-PAWEC with shallower potential wells can easily achieve inter-well oscillation under low-amplitude waves, with higher energy harvesting efficiency, and a wider frequency and work-damping band. Through a nonlinear bifurcation dynamics analysis, the causes of fluctuations and sudden changes in the output power under low-amplitude waves were revealed. Furthermore, the capture width ratio and annual average power of the South China Sea were considered. The influence of optimized PTO parameters on the energy-conversion performance of the NMT-PAWEC in regular and irregular waves was further discussed. In general, the efficient broadband power output capabilities demonstrate the excellent applicability of NMT-PAWEC.