Research On Power Capture Control Technology Of Direct-drive Wave Power Generation System

Wave energy has broad application prospects due to its high energy flow density and abundant global reserves.After a century of development,the utilization of wave energy through different wave energy conversion devices has been realized,but there are still many problems that need to be solved optimally.In this paper,combining the advantages and disadvantages of different wave power generation technologies,a new type of fully enclosed direct-drive wave power generation system is studied.In this system,a permanent magnet linear synchronous generator is used as the direct power take-off device,and the float swings under the action of waves,so that the relative motion between the stator and the translator of the linear generator generates electric energy.The key technologies studied in this paper include device modeling and simulation,controller design,and new power capture optimization methods.The details are as follows:1.Based on the method of the hybrid frequency-time domain,the hydrodynamic analysis and simulation software ANSYS AQWA is used to calculate the frequency response of hydrodynamic parameters in the kinetic model.By considering the hydrodynamic parameters at different wave frequencies,the mathematical model of the fully enclosed direct-drive wave power generation device is determined.At the same time,the JONSWAP wave spectrum and Longuet-Higgins wave model are considered to conduct the numerical simulation of random waves,so as to improve the simulation platform of the wave power generation system.2.In order to ensure that the system can quickly track the desired equilibrium state during the wave change process,the system model is reconstructed by the Hamiltonian framework.According to the structural characteristics of the reconstructed port-controlled Hamiltonian with dissipation model,the passivity-based controller is designed using modifying the interconnect matrix and injecting damping to improve the dynamic performance and stability of the system in the process of tracking the desired equilibrium state.3.Based on the characteristic that the speed of the linear generator in the direct-drive wave power generation system in the no-load state is higher than that in the power generation state,a new power capture optimization method is proposed,that is,the state switching control method.The linear generator is controlled to switch between the no-load state and the power generation state,eventually,the captured power is further improved.4.The passivity-based controller and state switching control method proposed in this paper are verified in the simulation platform of the wave power generation system based on MATLAB/Simulink.For the passivity-based controller,the parameters of the controller are discussed in order to find the best parameters applicable to the device.The state switching control method is compared with other power capture optimization methods to verify its performance and prospect.