Drive Train Transmission Type
Bladed provides two options for simulating a wind turbine drive train. One options is to use a Locked Speed Drive Train. This option is useful for running tests as it fixes the rotor speed simplifying the analysis of the rotor aeroelastic calculation during power production. Another option is to select the Dynamic Drive Train Model where the drive train speed may vary.
This is the most common analysis option that enables simulation of either geared or direct drive systems. In the geared arrangement the aerodynamic torque is transmitted through the low-speed shaft to a gearbox that then transforms the speed and torque to a high-speed shaft that can then connect to a generator. In this case electricity generation is done with a high rate of speed and low torque values. A direct drive transmission instead transmits the aerodynamic torque and rotor speed directly to the generator rotor.
An overview of the different options can be obtain by reviewing the Multibody Diagrams. Select the Power Train > Transmission tab to view and edit the drive train transmission options.
Locked Speed Model
This model is available for simple calculations where the turbine rotor is assumed to rotate at a constant speed. The rotor speed is specified along with the gearbox ratio, but no other characteristics of the drive train nor the generator may be specified. Flexible mountings cannot be modelled either. This model is useful for initial aerodynamic design of fixed speed rotors, but for detailed performance and loading calculations the dynamic model is more appropriate.
The following options are not available when selecting the locked speed model:
Dynamic Model
This model includes the rotational degree of freedom of the rotor such that a variable speed turbine can be simulated. Torsional flexibility of the drive train may be included as an option.
By default the dynamic drive train model is assumed to be a geared transmission. Unless Direct Drive has been selected on the Rotor screen, the gearbox ratio must be specified, along with the moment of inertia of the generator rotor known as the generator inertia.
The mass of the shafts and the gearbox should be included in the nacelle mass definition.
If the low-speed and high-speed shafts rotate in opposite directions the user can specify the Generator rotation to be opposite to the rotor. By default the shafts will assume to rotate in the same direction.
The additional inertia of the high-speed shaft may also be specified along with the inertia of the gearbox which is referred to the high-speed shaft. If there is a brake on the high-speed shaft, its inertia should be included as shown; depending on the location of the brake, it may be more appropriate to include it in the gearbox inertia.
The rotor speed will be governed by the characteristics of the generator, which must be defined in this case. For a variable speed turbine it is also necessary to define an appropriate controller to define the speed schedule.
Direct Drive
The Direct Drive transmission type can be activated by setting Transmission to Direct Drive in the Rotor screen. Note that Bladed models this type of power train by setting the gearbox ratio to 1.
The HSS flexibility and slipping clutch options are not available. Besides that the description for locked speed model and dynamic model hold.
When using a direct drive transmission the user should input the mass and inertia properties of generator stator in the Hub screen. Note that these values will be combined with the mass and inertia properties of the Nacelle.
Last updated 28-08-2024