The Study Of Design And Optimization Of Generator For Wave Energy And Its Control Strategy

With depletion of energy resources and increased pollution,renewable energy is attracting more and more attention.Wave energy has the advantages of wide distribution,large reserves and high availability with promising prospect for development and utilization.China is a large maritime country with a vast sea area and continuous coastline,which has unique advantages in development.The thesis focuses on the hydraulic energystorage,electrical generation and power conversion of the wave energy generation,the main work of the thesis is as follows:A permanent magnet synchronous generator with high efficiency and high power density is designed for hydraulic energy-storage wave energy generation system(HESWEGS).The model is built in Ansys and simulated with no-load and load condition.Aiming at the problems of high cogging torque of the designed motor,the influence of the structural parameters on the cogging torque is analyzed.The genetic algorithm is used to optimize the motor structure parameters,obtaining a better motor model in terms of power density and efficiency.The mathematical model of main components in HESWEGS is built.The control strategy of the maximum efficiency conversion applied to the hydraulic energy storage system and the implementation scheme to easure the safety and stability of the hydraulic system is analyzed.The simulation model including the hydraulic energy-storage,generation,rectifier and DC-load is built which based on the three-phase interleaving BOOST circuit.Aiming at the problems of higher harmonic content of AC-side caused by adopting uncontrolled rectifier,dual-PWM converter is used to improve power quality.The control strategy of converter and space vector pulse width modulation algorithm is analyzed,the simulation model is built and verified.The HESWEGS based on three-level dual-PWM converter is built.An improved balance factor method is proposed to solve the potential imbalance of neutral point in the three-level structure,which optimizes the sector division and inhibits the neutral-point potential offset and fluctuation effectively.In view of the numerous components and complicated modulation algorithm of the three-level dual-PWM converter,it is proposed to apply the Vienna recifier to generator-side converter,the simplified two-level SVPWM algorithm implementation method applied to the Vienna rectifier is analyzed.The wave-to-wire model is built based on Matlab/Simulink,the intermittent and continuous power generation modes of the system under different wave conditions are simulated.The results indicate stable operation of the system,which verifies the system structure,modulation method and control strategy that select and design for the wave energy system in this thesis are effective and feasible.