Motion Analysis And Control Of Hydraulic Energy Storage Type Wave Energy Converter

In recent years, with the continuous development of wave energy technology, a variety of different styles of wave power devices are widely used. In this paper, for hydraulic energy storage type wave energy converter, especially for single oscillating buoy type and Pelamis,working principle and wave energy capture feature are both analyzed through numerical calculation analysis in frequency domain and time domain. Then the adaptive damping control algorithm is used to control the motion of the floating body to maximize the capture width of absorbing wave energy on the basis of the above-mentioned analytical results.For single oscillating buoy type device, first, frequency domain analysis is conducted based on the linear energy conversion system to establish the motion equations in frequency domain and obtain the frequency response function. The capture width of the system is derived in regular and irregular wave conditions. Studies have shown that the capture width is affected by the peak frequency, the frequency response function of the oscillating buoy and the energy conversion system. Then in the time domain simulation, state-space model substitutes the convolution item in the time domain motion equation. According to the effect of damping coefficient on the capture width, adaptive damping control algorithm is used to adjust the damping coefficient with the wave frequency to the optimal damping coefficient to maximize the capture width in specified irregular wave condition.For Pelamis, theoretical analysis and numerical simulation are used. The effect of the hinged stiffness and damping coefficient on the average power is respectively analyzed. The results show that when the hinged stiffness coefficient is less than a certain value, the average power is almost constant, whereas when it exceeds this value,the average power significantly decreases with the stiffness increasing. The average power increases first and then decreases with the hinged damping increasing to have a unimodal trend. In terms of the motion control means,adaptive damping control algorithm replaces linear control method to adjust the hinged damping according to the predicted sea state information. The time domain simulation is conducted, the motion results of the floating body and the average power of the two control methods are compared in a certain time period. The results show that the reasonable control method can significantly increase the average power of the device.