Maximum Power Point Tracking Control via Time‐Varying Vector Equivalent Damping Modulation for Stroke‐Constrained Direct‐Drive Wave Energy Converters

ABSTRACT

Maximum power point tracking (MPPT) is an important approach for improving energy capture efficiency in wave energy conversion systems. To address the problem of limited energy capture caused by stroke constraints in direct‐drive wave energy converters, this paper proposes a stroke‐constrained MPPT control strategy based on time‐varying vector equivalent damping modulation. First, a hydrodynamic and electromechanical model of the direct‐drive wave energy conversion system is established, and the baseline control quantities under constraints are determined through constrained optimisation. The vector equivalent damping combines the dissipative component , which directly governs active energy extraction, and the quadrature component , which regulates the mechanical‐impedance phase and resonance matching. On this basis, a time‐varying damping modulation method is developed by combining a zonal triggering mechanism, a short‐term forward‐prediction‐based peak‐gain solver and a smooth damping envelope, so that the equivalent damping can be adaptively adjusted according to the instantaneous motion state of the device. Furthermore, to extend the control framework from regular‐wave conditions to irregular‐wave conditions, a short‐term equivalent sea‐state representation and platform‐based parameter updating scheme are introduced. Simulation results under representative operating conditions demonstrate that the proposed strategy can effectively satisfy the stroke constraint whilst achieving higher average captured power than conventional fixed‐damping constrained MPPT. Meanwhile, it maintains good adaptability. Therefore, the proposed method provides a feasible solution for safe and efficient MPPT control of direct‐drive wave energy converters.