The regulation scheme of a double-rotor wind turbine during operation based on the transmission modes of rotors

Current research on double-rotor wind turbines (DRWT) primarily focuses on aerodynamic performance and wake characteristics. Addressing the specific control challenges during operation, this study first establishes a geometric model of the Counter-rotating Double-Rotor Wind Turbine (C-DRWT) and an integrated drivetrain model from the dual rotors to the gearbox. Subsequently, based on the structural characteristics of C-DRWT and its operational wind speed range, three gearbox operating modes and three transmission configurations for the dual rotors are defined under necessary assumptions (e.g., assuming power/torque/speed parameters of both rotors remain below rated values). Finally, utilizing parameters from the NREL 5 MW reference wind turbine, torque-speed characteristic curves for three operational phases of C-DRWT are calculated and established. With power optimization as the control objective, the control strategies and detailed implementation schemes for each operational phase are elucidated through specific wind speed examples. The analysis demonstrates that C-DRWT can extend the effective operational wind speed range, thereby reducing downtime and lowering energy costs. This theoretical framework provides strategic guidance and operational protocols for practical implementation of C-DRWT systems.