A coordinated control method to smooth short-term power fluctuations of hybrid offshore renewable energy conversion system (HORECS)

The hybrid offshore renewable energy conversion system (HORECS) consists of offshore wind, wave and tidal power generations. Its output power fluctuates, which may cause power quality problems. A coordinated control method is presented in this paper to smooth the short-term power fluctuations. The tidal generation system is used to compensate the wind and wave power fluctuations. According to the variations of the tidal speed, the proposed method is divided into two stages. When the tidal speed is larger than the cut-in speed, the output fluctuations are smoothed by the coordinated rotational speed control and pitch control of the tidal generator. When the tidal speed is smaller than the cut-in speed, the tidal generator can be operated as a fly-wheel energy storage, and the kinetic energy of the tidal generator is used to compensate the power fluctuations. Simulations are performed to illustrate the control performance.