Hydrodynamic Characteristics of New Floating Wind-Wave Energy Combined Power Generation Devices Under Typhoon-Wave-Current Coupling

The South China Sea is rich in wind and wave energy resources,and the wind-wave combined power generation device is currently in the concept research and development stage.In recent years,extreme sea conditions such as super typhoons have frequently occurred,which poses a serious challenge to the safety of offshore floating platforms.In view of the lack of safety analysis of wind-wave combined power generation devices in extreme sea conditions at present,this paper takes the OC4-WEC combined with semi-submersible wind turbine(Semi-OC4)and the oscillating buoy wave energy converter as the research object,and establishes a mesoscale WRF-SWANFVCOM(W-S-F)real-time coupling platform based on the model coupling Toolkit(MCT)to analyze the spatial and temporal evolution of wind-wave-current in offshore wind farms during the whole process of super typhoon“Rammasun”transit.Combined with the medium/small scale nested method,the flow field characteristics of OC4-WEC platform are analyzed.The results show that the simulation accuracy of the established W-S-F platform for typhoon track is 42.51%higher than that of the single WRF model.Under the action of typhoon-wave-current,the heave motion amplitude of OC4-WEC platform is reduced by 38.1%,the surge motion amplitude is reduced by 26.7%,and the pitch motion amplitude is reduced by 23.4%.

Electrical control strategy for an ocean energy conversion system

Globally abundant wave energy for power generation attracts ever increasing attention. Because of non-linear dynamics and potential uncertainties in ocean energy conversion systems, generation productivity needs to be increased by applying robust control algorithms. This paper focuses on control strategies for a small ocean energy conversion system based on a direct driven permanent magnet synchronous generator (PMSG). It evaluates the performance of two kinds of control strategies, i.e., traditional field-oriented control (FOC) and robust adaptive control. The proposed adaptive control successfully achieves maximum velocity and stable power production, with reduced speed tracking error and system response time. The adaptive control also guarantees global system stability and its superiority over FOC by using a non-linear back-stepping control technique offering a better optimization solution. The robustness of the ocean energy conversion system is further enhanced by investigating the Lyapunov method and the use of a DC-DC boost converter. To overcome system complexity, turbine-generator based power take-off (PTO) is considered. A Matlab/Simulink study verifies the advantages of a non-linear control strategy for an Oscillating Water Column (OWC) based power generation system.