Research on Stabilization Control of Wave Energy Hydraulic Conversion System Based on Fuzzy-PI

Fuzzy-PI control of an oscillating body wave energy hydraulic conversion system is investigated under irregular waves. Non-linear dynamic model of the oscillating floating body and non-linear hydraulic power take off models are established. Hydraulic motor displacement fuzzy-PI controller based on motor speed error feedback is established. Numerical simulation of the system under different sea states are performed. The motor steady output characteristics of the wave energy conversion system under fuzzy PI control are studied. The influences of significant wave height and energy period on the stable output of the system are investigated. The annual captured energy and the motor output energy of the wave energy capture system at different observation points in the nearshore waters of the East China Sea are simulated. The results show that the irregular transients of motor output power, speed and torque can be controlled by using fuzzy PI controller, the motor speed is basically stable, and the power output is stable. The motor speed and output power increase with the increase of significant wave height, and the adjustment range of motor displacement increases. As the energy period increases, the motor speed and output power increase, the amplitude of increase reduces gradually, and the adjustment range of motor displacement decreases gradually. Based on the sea states data of the East China Sea, the energy capture and output of the system at nine observation points near the East China Sea are simulated. Numerical results show that the annual capture energy and motor output energy of the wave energy capture system increase with the increase of offshore distance. The annual capture energy and motor output energy of the system are higher in the south and southeast region of Zhoushan Island. © 2021 Journal of Mechanical Engineering.