Study On The Optimal Design And Control Of A Double-Buoy Floating Type Wave Power System

Double-buoy floating type wave power system is an energy conversion system by converting the wave energy into power directly, which has a bright development future and market benefit in the ocean wave energy exploitation with the advantages of higher stability, higher efficiency and lower manufacturing costs, etc. According to the experimental results of single-buoy wave power system, the theoretical analysis and experimental issues about double-buoy floating type wave power system are deeply studied in this thesis, including the operation principle, system model, optimal design, system construction, ocean experiment, and optimal control, etc. The thesis provides a foundation for the future research and practical application of double-buoy floating type wave power system.The main research fruits of this thesis are as follows:1. The operation principle of wave tank laboratory is analyzed, and the vertical wave force, vertical added masses and damping coefficient of buoy are calculated by frequency domain method.2. The vertical speed and position of buoy are analyzed by frequency domain method, and the mass of buoy is optimized. Thus, the buoy is resonance with wave in the direction of vertical motion. Based on that, a single-buoy wave power system is modeled and verified by experimental results.3. According to the analysis results of single-buoy wave power system, the permanent magnet linear generator is analyzed and optimized. Firstly, the air-gap leakage flux coefficient of permanent magnet linear generator is analytical calculated by magnetic circuit method and Kirchhoff s law, and the accuracy of analytical calculation method is verified by finite element analysis (FEA). Then, a cogging force minimization method is deduced from the end air-gap flux distribution parameters of permanent magnet linear generator.4. Besides, an improved analytical calculation method based on Schwarz-Christoffel mapping is proposed to calculate the air-gap magnetic field distribution of permanent magnet linear machine, and verified by FEA.5. The vertical motion process of buoy is analytical calculated by Green’s function and Froude-Krylov force, and the basic operation principle of double-buoy floating type wave power system is deduced from the vertical motion process of buoy.6. The mass design of outer buoy and inner buoy is optimized, both the outer buoy and inner buoy are made from ultra-high molecular weight polyethylene with high corrosion resistance, a halbach magnetization type of tubular permanent magnet linear generator is adopted to convert ocean wave energy into power directly, a data communication system based on GPRS and Internet network is adopted to achieve the monitor and management of double-buoy floating type wave power system, the single point mooring method is adopted to ensure the stable operation of double-buoy floating type wave power system.7. The construction process of double-buoy floating type wave power system is stated, and the ocean experiment of double-buoy floating type wave power system is completed by still water testing and power testing.8. The auto-regressive moving average (ARMA) model is established to forecast the vertical speed of ocean wave over a certain period of time. The internal model PID (proportion integration differentiation) method is proposed to optimize the load operation of double-buoy floating type wave power system, and the energy conversion from ocean wave to power can be maximized.