Autorotation modes of double-rotor darrieus wind turbine

— The movement of a small wind power plant with a vertical axis of rotation in a stationary air flow is considered. The plant consists of two coaxial Darrieus rotors rotating in opposite directions. On the shaft of one of them, the rotor of the generator is rigidly fixed, on the shaft of the other, the stator is placed. A closed few parametric mathematical model of a wind turbine is constructed by taking into account the aerodynamic effect on the rotors and the electrical load in the local circuit of the generator. The corresponding dynamic system is dual frequency. The system is averaged over two angles under the assumption that the value of each of the frequencies is non-zero. Attracting fixed points of the averaged system are considered as a first approximation to describe the operating modes of a wind turbine. Bifurcation diagrams that describe the evolution of fixed points of the averaged system when changing the model parameter, which characterizes the value of external resistance in the local circuit of the generator of the plant, are constructed. A parametric analysis of stability conditions for fixed points is carried out. By numerically integrating equations with different initial conditions and parameter values, estimates for the deviation of the solutions of the averaged system from the slow variables of the complete system are obtained. The conditions for maintaining the resonance frequency ratio in the system are considered separately.