Multi‐Domain Linear Hybrid Semi‐Mechanism Modeling and Two‐Level Coordinated Control for a Cascade Dual‐Rotor Wind Turbine

For a newly emerging kind of cascade dual‐rotor wind turbine (CDR‐WT), the coordinated control of its front and rear rotor faces significant challenges. To solve this problem, a novel modeling and control design approach is presented in this paper. Firstly,the operating principle of the CDR‐WT is introduced in detail, including its main structure and subsystem models, and ideal division of operating regions. Secondly, a multi‐domain linear hybrid semi‐mechanism (MD‐LHSM) modeling method is presented. Due to the complex nonlinear aerodynamic interference characteristics between the front and rear wind turbine rotors, non‐mechanism model with the piecewise affine regressive exogenous (PWARX)structure is adopted. It can be integrated with the models of the linear mechanism of other parts to obtain the total model of a CDR‐WT, yielding the MD‐LHSM model. Based on the dual‐rotor operation characteristics, a two‐level coordinated control strategy is proposed to optimize the complementary output characteristics between the front and rear rotors. Furthermore, based on the MD‐LHSM model, a satisfactory PID parameter tuning method for the PID controllers used in the two‐level coordinated control strategy is proposed, converting the PID parameter optimization into an output feedback problem. Finally, the modeling and control performance is validated on the hardware‐in‐the‐loop simulation platform. The results show that the developed controller can effectively track the optimal output curve of a 2.7 MW CDR‐WT by coordinating the operation of its front and rear rotors.