Defining the Generator Model
A wind turbine electric generator is driven by the drive shaft and turns a set of copper windings through a magnetic field generating electricity and applying a counter air-gap torque to the drive shaft. Bladed supports a series of electric generator models including fixed speed and variable speed options. Fixed speed options are useful for cases where the wind turbine generates electricity that matches exactly with the grid frequency. Variable speed options are generally used in more modern wind turbine concepts to enable constant tip speed tracking for optimal rotor performance during the torque control power production mode of operation.
Generator Models
The generator characteristics must be provided if either the dynamic drive train or direct drive transmission options are selected. Three types of generator model are available:
A directly connected induction generator model for constant speed turbines.
A variable speed generator model for variable speed turbines.
A variable slip generator model providing limited range variable speed above rated.
In each case the generator torque response is represented by a first order lag. Using these standard options the user can also simulate fault cases such as grid loss and generator short circuit events.
The user can also define electrical losses to represent the efficiency of electrical power conversion within the generator.
Drive Train Damping Feedback
The generator torque control may also include a built-in feedback term derived from the generator speed by means of a transfer function. This is superimposed on the torque demand from the controller and may be used to help damp out drive train torsional vibrations. Specify the transfer function in terms of the Laplace variable \(s\) by specifying the numerator and denominator polynomials.
Note
Do not include the drive train damping feedback here if it is already included in the torque demand from the external controller.
User-defined Generator Model
The external DLL option allows a user-defined model for calculating the air-gap torque and electrical power output. This offers the user flexibility to define anything from a simple mechanical model to a comprehensive electrical dynamic model including the generator and, if appropriate, the power converter and electrical network. An external electrical dynamic model could be used to calculate electrical flicker coefficients and to model the effect of network voltage and frequency variations.
Last updated 30-08-2024