Abstract
Electrical faults can lead to transient and dynamic excitations of the electromagnetic generator torque in wind turbines. The fast changes in the generator torque lead to load oscillations and rapid changes in the speed of rotation. The combination of dynamic load reversals and changing rotational speeds can be detrimental to gearbox components. This paper shows, via simulation, that the smearing risk increases due to the electrical faults for cylindrical roller bearings on the high speed shaft of a wind turbine research nacelle. A grid fault was examined for the research nacelle with a doubly fed induction generator concept. Furthermore, a converter fault was analyzed for the full size converter concept. Both wind turbine grid connection concepts used the same mechanical drive train. Thus, the mechanical component loading was comparable. During the grid fault, the risk of smearing increased momentarily by a maximum of around 1.8 times. During the converter fault, the risk of smearing increased by around 4.9 times. Subsequently, electrical faults increased the risk of damage to the wind turbine gearbox bearings, especially on the high speed stage.
Highlights
An investigation of electrical faults and their influence on an increase in the risk of damages to the wind turbines (WTs) gearbox components is conducted at the CWD in the project DynaGET
The speed of rotation of the high speed stage (HSS) increased because of the slower decrease in drive torque than in the electromagnetic generator torque, which was a result of the drive s high inertia
The mechanical HSS torque oscillated shortly after the fault was triggered. It reached 1.12 times nominal value before it decreased to a minimum of around 68 per cent over a period of 97 ms
Summary
An investigation of electrical faults and their influence on an increase in the risk of damages to the WT gearbox components is conducted at the CWD in the project DynaGET. A detailed model is implemented for the rotor side cylindrical roller bearing [14] (see Figure 5) in order to calculate the Hertzian contact pressure and the kinematics of each roller for the evaluation of a smearing criterion.
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