## 1 Introduction
These dynamic models offer high accuracy of the dynamic response regarding the simulations of the energy system and a reduction in the simulation time compared to the detailed model of the actual wind farm. A dynamic model of a fixed-pitch angle wind turbine simulator is presented in [14], which includes different wind turbine profiles for which the mechanical power characteristics of the wind turbine are assigned. The model allows defining the mechanical power and torque as functions of the wind speed. A similar concept is presented in [15], where the Blade Element Method is used to determine the power coefficient of a turbine consisting of a wind rotor, a speed increase, and a conventional electric generator. The model considers the hydrodynamic data for the rotor, the inertia characteristics of the whole system, frictional losses, and the electromagnetic torque of the generator. [PERSON] et al. propose in [16] a method to improve the dynamic response of a wind turbine by a torque error feed-forward control and the blade-pitch angle servo control. The mechanical system model is based on the FAST code, the results being validated on a five megawatt wind turbine. The dynamic behaviour of wind turbines under stormy wind conditions is presented in [17]. The authors use the beam theory to couple the wind turbine dynamic model to the unsteady aerodynamic model to generate the dynamic response of the system. The results are simulated on two wind turbines of two and six megawatts. The dynamic model of a wind turbine without a gearbox is presented in [18], the simulation performed in MATLAB-Simulink considering load flow, fluctuations in wind speed, and transient and output power. The researchers in the field have paid particular attention to the dynamics of the gearbox, the literature proving that the dynamic behaviour of speed increases is closely related to the dynamic behaviour of the wind systems. A gear transmission of Ravigneaux type is used in [19] to propose a dynamic analysis method based on a general algorithm for determining the transmission ratio, transmission torques, and efficiency. Another method for dynamic modelling uses numerical integration of Runge-Kutta type [20], and considers nonlinear dynamic characteristics of a speed increase with one input and one output. Another nonlinear dynamic model is presented in [21], which considers a planetary speed increase with an input and an output for which the load distribution on the gears is studied, the algorithm being based on the lumped parameters method. To improve the load-sharing capacity on the component gear pairs, [PERSON] et al. present in [22] a dynamic model of a planetary speed increase with flexible pins. The dynamic behaviour of the wind system is also studied using the lumped parameter model, in which the stiffness of the bodies is predicted using the finite element method. Another approach is proposed by [PERSON] et al. in [23] that discusses the dynamics of a speed increase depending on the power vs. speed curve; the dynamic effect due to different input powers on the mechanical characteristics of the speed increase is also investigated. A dynamic analysis of a planetary speed increase is developed in [24] using the torsional multibody model, used to investigate the transient response of the transmission. Different planetary speed increasers for wind and hydro applications are proposed and dynamically analysed in [25; 26] as transmissions with one input and one output. A new planetary speed increase with two inputs and one output is proposed by [PERSON] et al. [27] and its dynamic responses are simulated using the fourth order Runge-Kutta method. The time-domain dynamic response of heavy-duty planetary speed increasers is studied in [28] by using the lateral-torsional coupling modelling method; the method is validated on a two megawatt wind turbine gearbox. [PERSON] et al.