Cross-coupling control design of a flexible dual rotor wind turbine with enhanced wind energy capture capacity

In order to improve the reliability of wind turbine grid connection and reduce the cost of wind power generation, this paper studies a counter-rotating dual rotor wind turbine (DRWT) which consists of decoupled driven-train subsystems, a triple-terminal converter and a dual rotor generator. For this new-type wind energy conversion system, its modeling and control strategy need to be studied. Firstly, mechanism model of the DRWT with a new structure is constructed. By investigating the effects of pitch angles and rotor speeds on output power, respectively, the maximum power output condition of the DRWT is obtained. Considering the overall energy conversion efficiency and mechanical load constraints, the optimal regime of the DRWT is established. Based on the optimal torque algorithm and cross-coupling control strategy, this paper presents a novel cross-coupling control strategy for the DRWT to track maximum power. The proposed strategy can regulate the rotor speed of the front and rear rotors, enabling DRWT to operate on the optimal speed combination curve. Finally, the hardware-in-the-loop experiment is built to test the performance of the proposed strategy under various wind conditions. The simulation results verify that the proposed strategy can improve power generation, and analysis shows that the proposed strategy fundamentally alters the energy capture ratio between the front and rear wind turbines to optimize total output power.