Abstract: In order to solve the problem of maximum energy capture in the dynamic change of current, the research of maximum power point tracking(MPPT) control strategy of an extensible vertical-axis blade current power generation system is carried out. Based on the analysis of the current equation of motion of power generation system, an optimal torque control strategy is proposed based on second-order sliding mode using the output torque as the feedback signals to solve the existing problems of MPPT, like the precise measurement of current velocity and the complicated design of control system. The simulation results show that the power control device and control system can dynamically track the maximum power point, and have good dynamic characteristics and control effect. The stability and effectiveness of the control strategy are verified.

Key words: primary energy, marine current energy conversion system, maximum power point tracking, second-order sliding mode, optimum torque