Design and Control of Marine Current System with Counter-Rotating Horizontal-Axis Twin-Rotor Turbine

A novel marine current system integrated with counter-rotating horizontal-axis twin-rotor turbines and mechanical–hydraulic transmission (MCHTMS) is proposed to improve energy capture efficiency. An impeller is incorporated into the front of the rear impeller to capture the energy near the impeller root. Based on computational fluid dynamics (CFD) and blade element momentum (BEM) theory, the power formula of the MCHTMS is developed to optimize the dimensions of the front impeller for power efficiency. A coupled adaptive sliding-mode control (CASMC) strategy is proposed to achieve higher maximum-power-point-tracking efficiency and enhance the system stability of the MCHTMS. The adaptive iteration parameters of the impellers in the CASMC are adjusted by using the coupled power error and the torque error, effectively accommodating the short-term fluctuations and long-term stability of marine currents. Simulation results demonstrate that the optimized counter-rotating twin-rotor structure can improve energy capture efficiency, and the proposed CASMC strategy effectively enables the impeller to track the optimal rotational speed. These results prove that MCHTMS with CASMC is an effective marine current system for generating high and steady electrical energy.