A Wind-Wave Farm System With Self-Energy Storage and Smoothed Power Output

This paper proposes a wind-wave farm system with a self-energy storage capability and a smoothed total power output. The fluctuating electrical power from wave is smoothed by utilizing the rotor inertias of the wind turbines as short-term energy storage devices, thus without extra energy storage hardware the investment and maintenance cost of the wave energy conversion is reduced. This is achieved based on the fact that the wind power can be viewed as constant during a typical wave period (5~12 s). The proposed integral compensation control of the wind turbines can optimize two conflicting objectives: maximizing wind energy capture at different wind speeds and regulating the rotor speeds of wind turbines as kinetic energy storage devices. It enables the turbine speed to swing around its optimum points at different wind speeds. Consequently, the total power output of the wind-wave farm is well smoothed at a marginal cost of the power take-off efficiency loss. RTDS simulations and quantitative analysis are presented to demonstrate the proposed system. To demonstrate its superiority, the proposed control method is compared with the direct compensation of the wave power based on the existing maximum power point tracking method.