Optimal Control of Wave Energy Devices with Nonlinear Reactive Power Constraints

Abstract

This paper proposes an optimal control strategy for wave energy devices subject to physical and nonlinear reactive power constraints. Using a pseudospectral Legendre method, optimization is carried out with energy maximization as a target. Physical limitations are applied to the WEC position, velocity, and controller, while a reactive power constraint is added to reduce the negative peaks in the system output power. The optimized velocity of the WEC is used as a reference input to a velocity-following control loop, which tracks it. Since wave energy converters are subjected to parametric uncertainties in stiffness, radiation force coefficients, and physical disturbances, robust backstepping control is employed in the lower-loop to handle these. The proposed control scheme is validated numerically on a cylindrical buoy wave energy converter system.