Sliding mode extremum seeking control for maximum power extraction in wave energy converters

Renewable energy is a revolution in the field of power generation to ensure environment friendly alternatives to fossil fuels. Wave power is a huge source of renewable energy found in the ocean's waves. In this research, the main objective is to extract maximum wave power from the near-shore waves in multiple degrees-of-freedom (DOF). In order to achieve this goal, a combination of design, control, and energy transfer parameters are considered to extract energy from buoy motions that are applied to a multi DOF robotic wave energy converter (WEC). The specific design of a buoy and dynamic modeling of a 2 DOF WEC are used in a case study as a robotic arm acting in a reverse mode, i.e., conversion of mechanical energy into electric power acting in pitch and heave direction of motion. The power extraction algorithm is controlled by a sliding mode extremum seeking (SM-ES) method that ensures the same phase trajectory in the face of multiple frequency regular wave patterns. Simulation analyses are introduced to exhibit the execution of the power extraction scheme and its productiveness. Furthermore, the performance of the proposed controller is compared with a latching control method. According to the results, the proposed controller offers superior performance in terms of power absorbed.