WindClass1, WindClass2, WindClass3, WindClass4, WindBasic

Weather Related Models were added in Version 23

There are several Power Flow Weather Models that use the wind speed to calculate a weather-dependent MWMax for the generator. The wind speed in meters per second is obtained from generator field WS_WindSpeedMsec as described in the help topic Generator assignments to WeatherStation and XYCurve. If the generator can not obtain a valid wind speed there is a model parameter called DefaultWindMS which will be used instead . Either the WS_WindSpeedMsec or the DefaultWindMS is then multiplied by a model parameter called HubScalar. The HubScalar represents the conversion from the measured wind speed, which may be on the ground, to the wind speed at the height at which the wind turbine sits (this is often called the "hub height"). The wind turbines can be very tall, so multiplying the measured wind speed by a factor between 1.0 and 2.0 is typically done and this factor is called the HubScalar. The value UsedSpeed is then run through a Normalized Power Curve which is different for each of these models. The Normalized Power Curve output is a value between 0.0 and 1.0. This normalized value is then multiplied by the model parameter MWMax to create the output of the Wind Model which represents the weather-dependent MWMax value that should be used by the generator. Finally depending on the input parameters AllowTurnOff and AllowTurnOn the model may also either open or close the generator described in the logic below.

Parameters common to all Wind-based power flow weather models.

Parameter	Description
AllowTurnOff	Set to 1 to indicate that if the wind speed results in a curve output = 0, then the generator can be turned off (status set to OPEN). For any value other than 1, then the generator will not be opened automatically by this model.
AllowTurnOn	Set to 1 to indicate that if the windspeed results in a curve output > 0, then the generator can be turned on (status set to CLOSED). For any value other than 1, then the generator will not be closed automatically by this model.
MWMax	The largest MWMax allowed for this generator. The Output of this model will be equal to the result of the normalized curve multiplied by this value.
HubScalar	The WindSpeed (in meters per second) at the location of the generator is mulltiplied by this number to represent the scalar in the wind speed being measured and the wind at the height of the wind turbine. This is often called the "Hub Height Scalar". Typical values are 1.0 - 2.0
DefaultWindMS	If a generator does not have access to a WeatherStation to determine the Wind Speed in meters per second, then this wind speed will be used instead.

With this general setup, the difference between the models is in how the Normalized Power Curve is defined. The International Electrotechnical Commission (IEC) defines a standard IEC 61400. This standard defines 4 different wind turbine classes which represent 4 different wind speed environments for High, Medium, Low, and Very Low wind speeds. PowerWorld has defined 4 models with hard-coded Normalized Output Curves with one for each class of wind defined in IEC 61400 with guidance to defines these curves obtained from the paper: C. Draxl, A. Clifton, B. Hodge, J. McCaa, “The Wind Integration National Dataset (WIND) Toolkit,” Applied Energy, vol. 151, pp. 355-366, 2015. There is also a simple generic model we call WindBasic. The Normalized Output Curves are documented below.

WindClass1 Normalized Output Curve (High Wind)

Class 1 are for High Winds defined as an annual average wind speed at the hub height of 10 m/s (36 km/h; 22 mph) with 70 m/s extreme gusts (250 km/h; 160 mph).

A hard-coded piece-wise linear curve as described next is used for the WindClass1 curve.

If      UsedSpeed >  26 Then Output = 0.000
Else If UsedSpeed >= 17 Then Output = 1.000
Else If UsedSpeed >= 16 Then Output = 0.999 + (UsedSpeed - 16) * 0.001
Else If UsedSpeed >= 15 Then Output = 0.999 + (UsedSpeed - 15) * 0.000
Else If UsedSpeed >= 14 Then Output = 0.995 + (UsedSpeed - 14) * 0.004
Else If UsedSpeed >= 13 Then Output = 0.977 + (UsedSpeed - 13) * 0.018
Else If UsedSpeed >= 12 Then Output = 0.926 + (UsedSpeed - 12) * 0.051
Else If UsedSpeed >= 11 Then Output = 0.829 + (UsedSpeed - 11) * 0.097
Else If UsedSpeed >= 10 Then Output = 0.673 + (UsedSpeed - 10) * 0.156
Else If UsedSpeed >=  9 Then Output = 0.502 + (UsedSpeed -  9) * 0.171
Else If UsedSpeed >=  8 Then Output = 0.353 + (UsedSpeed -  8) * 0.149
Else If UsedSpeed >=  7 Then Output = 0.233 + (UsedSpeed -  7) * 0.120
Else If UsedSpeed >=  6 Then Output = 0.143 + (UsedSpeed -  6) * 0.090
Else If UsedSpeed >=  5 Then Output = 0.077 + (UsedSpeed -  5) * 0.066
Else If UsedSpeed >=  4 Then Output = 0.032 + (UsedSpeed -  4) * 0.045
Else If UsedSpeed >=  3 Then Output = 0.004 + (UsedSpeed -  3) * 0.028
Else If UsedSpeed >=  2 Then Output = 0.000 + (UsedSpeed -  2) * 0.004
Else                         Output = 0.000

WindClass2 Normalized Output Curve (Medium Wind)

Class 2 are for Medium Winds defined as an annual average wind speed at the hub height of 8.5 m/s (31 km/h; 19 mph) with 59.5 m/s extreme gusts (214 km/h; 133 mph).

A hard-coded piece-wise linear curve as described next is used for the WindClass2 curve.

If      UsedSpeed >  26 Then Output = 0.000
Else If UsedSpeed >= 14 Then Output = 1.000
Else If UsedSpeed >= 13 Then Output = 0.999 + (UsedSpeed - 13) * 0.001
Else If UsedSpeed >= 12 Then Output = 0.994 + (UsedSpeed - 12) * 0.005
Else If UsedSpeed >= 11 Then Output = 0.964 + (UsedSpeed - 11) * 0.030
Else If UsedSpeed >= 10 Then Output = 0.855 + (UsedSpeed - 10) * 0.109
Else If UsedSpeed >=  9 Then Output = 0.669 + (UsedSpeed -  9) * 0.186
Else If UsedSpeed >=  8 Then Output = 0.473 + (UsedSpeed -  8) * 0.196
Else If UsedSpeed >=  7 Then Output = 0.313 + (UsedSpeed -  7) * 0.160
Else If UsedSpeed >=  6 Then Output = 0.190 + (UsedSpeed -  6) * 0.123
Else If UsedSpeed >=  5 Then Output = 0.103 + (UsedSpeed -  5) * 0.087
Else If UsedSpeed >=  4 Then Output = 0.042 + (UsedSpeed -  4) * 0.061
Else If UsedSpeed >=  3 Then Output = 0.005 + (UsedSpeed -  3) * 0.037
Else If UsedSpeed >=  2 Then Output = 0.000 + (UsedSpeed -  2) * 0.005
Else                         Output = 0.000

WindClass3 Normalized Output Curve (Low Wind)

Class 3 are for Low Winds defined as an annual average wind speed at the hub height of 7.5 m/s (27 km/h; 17 mph) with 52.5 m/s extreme gusts (189 km/h; 117 mph).

A hard-coded piece-wise linear curve as described next is used for the WindClass3 curve.

If      UsedSpeed >  23 Then Output = 0.000
Else If UsedSpeed >= 12 Then Output = 1.000
Else If UsedSpeed >= 11 Then Output = 0.980 + (UsedSpeed - 11) * 0.020
Else If UsedSpeed >= 10 Then Output = 0.918 + (UsedSpeed - 10) * 0.062
Else If UsedSpeed >=  9 Then Output = 0.785 + (UsedSpeed -  9) * 0.133
Else If UsedSpeed >=  8 Then Output = 0.595 + (UsedSpeed -  8) * 0.190
Else If UsedSpeed >=  7 Then Output = 0.403 + (UsedSpeed -  7) * 0.192
Else If UsedSpeed >=  6 Then Output = 0.251 + (UsedSpeed -  6) * 0.152
Else If UsedSpeed >=  5 Then Output = 0.135 + (UsedSpeed -  5) * 0.116
Else If UsedSpeed >=  4 Then Output = 0.053 + (UsedSpeed -  4) * 0.082
Else If UsedSpeed >=  3 Then Output = 0.005 + (UsedSpeed -  3) * 0.048
Else If UsedSpeed >=  2 Then Output = 0.000 + (UsedSpeed -  2) * 0.005
Else                         Output = 0.000

WindClass4 Normalized Output Curve (Very Low Wind)

Class 4 are for Very Low Winds defined as an annual average wind speed at the hub height of 6.0 m/s (22 km/h; 13 mph) with 42 m/s extreme gusts (150 km/h; 94 mph).

A hard-coded piece-wise linear curve as described next is used for the WindClass4 curve.

If      UsedSpeed >  20 Then Output = 0.000
Else If UsedSpeed >= 11 Then Output = 1.000
Else If UsedSpeed >= 10 Then Output = 0.980 + (UsedSpeed - 11) * 0.020
Else If UsedSpeed >=  9 Then Output = 0.918 + (UsedSpeed - 10) * 0.062
Else If UsedSpeed >=  8 Then Output = 0.785 + (UsedSpeed -  9) * 0.133
Else If UsedSpeed >=  7 Then Output = 0.595 + (UsedSpeed -  8) * 0.190
Else If UsedSpeed >=  6 Then Output = 0.403 + (UsedSpeed -  7) * 0.192
Else If UsedSpeed >=  5 Then Output = 0.251 + (UsedSpeed -  6) * 0.152
Else If UsedSpeed >=  4 Then Output = 0.135 + (UsedSpeed -  5) * 0.116
Else If UsedSpeed >=  3 Then Output = 0.053 + (UsedSpeed -  4) * 0.082
Else If UsedSpeed >=  2 Then Output = 0.000 + (UsedSpeed -  3) * 0.053
Else                         Output = 0.000

WindBasic

The WindBasic model is a simple model providing linear segments where the Normalized Output Curve transitions from 0.0 up to 1.0 and then from 1.0 back to 0.0. There are 4 input parameters to describe this as follows.

Parameter

Description

CutInMS

Between CutInMS and RatedMS the normalized output will vary linearly between 0.0 and 1.0.

RatedMS

Lowest wind speed in Meters per Second at which the normalized output reaches a value of 1.0.

CutOut1MS

Higher wind speed at which the normalized output starts decreasing. Between CutOut1MS and CutOut2MS, the normalized output will vary linearly between 1.0 and 0.0.

CutOut2MS

Highest wind speed in Meters per Second at which the normalized output still has a value and thus above this value the normalized output is 1.0.

This gives a the following pseudo code.

If      (UsedSpeed >= RatedMS  ) AND (UsedSpeed <= CutOut1MS) Then 
   Output = 1.000
Else If (UsedSpeed <  RatedMS  )     Then 
   Output = (UsedSpeed - CutInMS  )/(RatedMS - CutInMS)
Else If (CutOut2MS >  CutOut1MS) AND (UsedSpeed >  CutoutMS ) Then 
   Output = (CutOut2MS - UsedSpeed)/(CustOut2MS - CutOut1MS)
Else
   Output = 0.000

Parameter	Description
CutInMS	Between CutInMS and RatedMS the normalized output will vary linearly between 0.0 and 1.0.
RatedMS	Lowest wind speed in Meters per Second at which the normalized output reaches a value of 1.0.
CutOut1MS	Higher wind speed at which the normalized output starts decreasing. Between CutOut1MS and CutOut2MS, the normalized output will vary linearly between 1.0 and 0.0.
CutOut2MS	Highest wind speed in Meters per Second at which the normalized output still has a value and thus above this value the normalized output is 1.0.