A maximum power point tracking control strategy of tidal energy conversion system based on fixed-time observer technology

Abstract

To achieve maximum tidal current energy capture in complex and harsh marine environments, this paper proposes a nonlinear control based on fixed-time observer (NCFTO) for tidal energy conversion system (TECS). The TECS operating in the ocean not only needs to face time-varying ocean current speed, but also needs to consider the adverse effects brought by parameter uncertainties and unknown disturbances in actual operation. Considering the high nonlinearity of TECS, conventional linear control systems may not necessarily provide satisfactory performance. Therefore, the NCFTO takes into account the TECS parameter uncertainties and unknown disturbances in its design. This mainly involves using a designed fixed-time observer to accurately estimate a concentrated disturbance term containing TECS nonlinearities, parameter uncertainties, disturbances in real time, and offsetting the adverse effects of actual disturbances on the control system. Meanwhile, a linear controller is designed based on the linearization of TECS to ensure satisfactory performance of NCFTO under time-varying ocean current speed, thus laying a solid foundation for achieving maximum tidal current energy capture. In addition, to verify the feasibility and effectiveness of NCFTO, three simulation testing scenarios have been set up, namely time-varying ocean current speed, rotor inertia uncertainty, and unknown disturbance torque.