Rotational Speed Optimization in Oscillating Water Column Wave Power Plants Based on Maximum Power Point Tracking

After the 2015 United Nations Climate Change Conference (COP21) the interest for clean and renewable energy is high priority in global energy policy. In this sense, the ocean offers a great potential for energy harnessing. However, in the path to commercialization, conversion systems still lack maturity. Oscillating water column (OWC) power plants are among the most promising cost-effective and ecologically compatible technologies. The NEREIDA MOWC wave power plant, located on the Basque coast of Mutriku, is a clear example of this principle. In addition, the maximum power point tracking (MPPT) strategy, which has already been used successfully in other renewable energy systems, stands out as one of the most useful schemes. In this context, this paper focuses on the implementation of a novel MPPT control approach for the OWC systems in order to optimize the power delivered to the grid. For this purpose, a full wave-to-wire plant model is introduced, and a new MPPT-based control scheme is presented. The controller continuously adjusts the energy conversion of the doubly fed induction generator according to an established MPPT curve so as to optimize the power generated. In order to demonstrate the goodness and feasibility of the proposed control scheme, its behavior is tested and compared in two representative case studies of both uncontrolled and controlled plants. In the first case, an air valve control is employed, and in the second case, an MPPT-based control strategy has been implemented. Results show that the proposed MPPT-based control successfully matches the optimum rotational speed, allowing maximum active power generation.