PID


The pitch angle is commanded by a Proportional-Integral-Derivative (PID) controller. The pitch controller impemented in Ashes is a PID controller that follows the NREL 5-MW controller. See Jonkman et al. (2009k) for more information.

The parameters of the PID controllers are the following:

Pitch control

Maximum pitch

The maximum pitch of the blades.

  • Default value: 90
  • Unit: $°$
  • Range: -180 — 180

Minimum pitch

The minimum pitch of the blades.

  • Default value: 0
  • Unit: $°$
  • Range: -180 — 180

Maximum pitch rate

The maximum collective pitch rate for the blades.

  • Default value: 8
  • Unit: ${°} \over {\text{s}}$
  • Range: 0 — 1e+06

Proportional gain

The factor that the speed error will be multiplied by when computing the pitch angle. Unit: [second]. Min value: 0. Max value: 1000.


  • Default value: 0.0188268
  • Unit: $\text{s}$
  • Range: 0 — 1000

Integral gain

The factor that the integral of the speed error will be multiplied by when computing the pitch angle. Unit: no unit. Min value: 0. Max value: 1000.

  • Default value: 0.00806863
  • Unit:
  • Range: 0 — 1000

Derivative gain

The factor that the derivative of the velocity error will be multiplied by when computing the demanded collective blade pitch angle.

The default value is zero, since for the NREL 5MW reference turbine the derivative gain is set to zero. As the unit of the error is deg/s, the unit of the derivative is deg/s^2. Thus, the unit of this factor is s^2. Note that the gain factors would be the same for rotational velocity error of the generator in radians/s as in degrees/s since the gain factors themselves do not have the angle as a part of their units.

  • Default value: 0
  • Unit: $\text{s}^2$
  • Range: 0 — 1000

Gain scheduling

If enabled, the computed pitch angle is scaled by a gain correction factor that is a function of the previous pitch angle. Refer to to the documentation for more information.

  • Default value: True
  • Unit:

Pitch angle parameter

The reference pitch angle used in the expression for the gain scheduling correction. This pitch angle corresponds angle where the pitch sensitivity (the derivative of aerodynamic power with respect to pitch angle) has doubled from its value at the operating point (i.e. a pitch angle of zero). The symbol used for this parameter is theta_k. Refer to the documentation for more information.

  • Default value: 6.30234
  • Unit: $°$
  • Range: 1e-06 — 90

Advanced

Pseudo rated rotor RPM

This built-in, PID based, demanded blade pitch controller uses the rated RPM of the generator as its set-point (target value). However, if there is no generator or the generator does not have a rated RPM, then this value is used as the set-point for the RPM of the rotor.

It is named pseudo because it is NOT rated RPM in the usual sense. It is typically just relevant to use this in some academic or research settings. IRL a wind turbine always has a generator and the generator has a rated RPM.

  • Default value: 20
  • Unit: $\text{rpm}$
  • Range: 1e-06 — 10000