Design Of Multi-Degree-of-Freedom Wave Energy Converter And Its Array Optimization

Environmental degradation and energy crisis are two major problems that restrict the development of society,economics and science.Thus,researchers at home and abroad focus their researches on the development and utilization of new energy.The new alternative energy sources must be found in the future to resolve these questions.Wave energy,rich and renewable,is one of the research hotspots.In this thesis,the basic content and research history of wave energy converter(WEC)is outlined,and the equivalent circuit model of point absorber double-degreeof-freedom wave energy converter(DDOF-WEC)was simplified by the electrical analogue method.Then,the sufficient condition of system stability was analyzed by Routh-Hurwitz criterion based on transfer functions.Further,the effects of wave parameters on the output power and stability of WEC were analyzed.Finally,the improved differential evolution algorithm(DE)is used to optimize the array of singledegree-of-freedom wave energy converter(SDOF-WEC)and DDOF-WEC.The main research covers the following four parts:(1)System modeling.Compared with the numerical analysis method,the electrical analogue method is introduced to establish the WEC model.Then,the equivalent circuit model of DDOF-WEC,including heave and surge,is established by the similarity principle between mechanical engineering and electrical engineering.And the decoupling of heave and surge makes the model satisfy the circuit principle to simplify the analysis.(2)Stability analysis.Based on the equivalent circuit model and transfer functions,the system stability of SDOF-WEC and DDOF-WEC are analyzed by Routh-Hurwitz criterion.Finally,the sufficient conditions of system stability are obtained.(3)Analysis on output power.The influence factors of output power of WEC under resonance conditions are analyzed in this thesis.Then,the output power of SDOF-WEC and DDOF-WEC are simulated and compared in Simulink.The results show that the DDOF-WEC has better wave energy capture capability than SDOF-WEC.(4)Array optimization.The DE is improved by introducing the adaptive mutation operator to optimize the layout of WEC array.The convergence accuracy and convergence speed of the improved DE have been increased and the DDOF-WEC array can absorb more wave energy.Besides,the array optimization law of WEC is analyzed,and the effectiveness of improved DE for optimizing the WEC array is verified by simulation.