Power Management of an Oscillating Water Column Wave Energy Converter with Battery/Supercapacitor Hybrid Energy Storage

—This paper focuses on developing a power management system (PMS) for a grid connected oscillating water column (OWC) wave energy converter with a battery/supercapacitor hybrid energy storage system. The main objective of the PMS is to transfer large power pulses present in the input to the energy storage elements and thereby maintain smooth power delivery to the grid. In addition, maintaining state of charge (SOC) of the battery and supercapacitor within safe limits and ensuring sufficient reserves are other objectives of the PMS. In the proposed PMS, power sharing between energy storage elements is determined based on the deviation of the supercapacitor SOC from the mid-point and its rate of change. Moreover, the power commitment to the grid is adjusted based on the deviation of battery SOC from the mid-point and its rate of change. Successful operation of the proposed PMS is verified using MATLAB/Simulink simulations. Apart from that, the variable speed operation of the turbine is also simulated to observe its effect on the supercapacitor sizing. Simulation results show that the variable speed operation help reduce required capacity of the supercapacitor.