Curtailment strategies
The impact of curtailment strategies, such as noise curtailment or wind sector management, where a turbine switches operation mode may be estimated using a power time series calculation.
The high-level modelling process for time series curtailments is:
- Define multi-mode turbine type specifications
- Define and prioritise curtailment types
- Define curtailment rules that cause turbines to switch turbine type mode
- Run the frequency domain energy calculation to define the gross yield, wake, and hysteresis efficiencies
- Setup and run the power time series calculation a. For quick checks of results see the Efficiency results task where overall curtailment efficiencies are shown by turbine and wind farm
- Run the Monte Carlo Net Energy simulation to predict net energy including the calculated efficiencies
- Export and review results looking at: a. Curtailment efficiencies by turbine in the turbine results TSV report b. The efficiency break-down table 5.1 in the word report or efficiencies TSV report
Curtailment rule definition
In the curtailment strategies task you can define the curtailment.
Curtailment rules specification can be imported from (an xml file) and WindFarmer: Analyst includes a Curtailment importer spreadsheet tool to support the definition of this xml file.
The workflow for defining or editing curtailment rules is as follows:
- Define and prioritise curtailment types in WindFarmer: Analyst
- Launch the “curtailment importer spreadsheet” You may have to import a curtailments xml file saved next to your workbook if the tool is not automatically populated with the curtailments already defined in your workbook.
- Define your curtailment rules in the spreadsheet, note that any rules already within the workbook will be shown in the spreadsheet so you can edit them.
- Export the xml file from the spreadsheet
- Import the curtailments xml file in to WFA.
- Review the curtailments defined in the WFA UI.
Note
• Wind sector management rules are upgraded to curtailment rules when you open a workbook with a version older than WFA 1.3.
• The only curtailment type supported in Classic AEP is sector management (where only speed and direction fields are populated) and the active mode must be 'shutdown'. Any deviation from this will cause the rule to be bypassed.
Curtailment rule conditions
Curtailment rules are specified by a set of conditions. All conditions must evaluate to be true for the curtailment rule to apply. Conditions apply over a range, from and to a value.
| Condition type | units and valid data | data type | Inclusivity of range |
|---|---|---|---|
| Wind speed range | m/s, >=0 | double | [From, To) |
| Wind direction range | degrees, 0 to 360 | double | [From, To) |
| Temperature range | °C, -50 to 100 | double | [From, To) |
| Day of year range | day of year, 1 to 365, For leap years it is impossible to have a day range that ends on 29th February: day 60 is always 1st March and in a leap year, the 29th of February is not counted. | integer | [From, To] |
| Time range: Time from, time to | HH:mm:ss as either an offset from sunrise / sunset or an absolute time, depending on the type. | There can be one "time from" and one "time to" condition from the 3 types of time range condition | [From, To) |
| Time range condition type | units and valid data | data type | Inclusivity of range |
|---|---|---|---|
| Time of day | HH:mm:ss, e.g. 18:30:00 | absolute time of day | [From, To) |
| Sunrise offset | HH:mm:ss, e.g. -00:30:00 | -ve is hours before sunrise, +ve is hours after sunrise | [From, To) |
| Sunset offset | HH:mm:ss, e.g. +04:30:00 | -ve is hours before sunset, +ve is hours after sunset | [From, To) |
Note
• Only one time-from and one time-to condition should be applied per curtailment rule, otherwise they contradict.
• If your conditions are both sunset offsets, or both sunrise offsets,the time range should fall on one day.
• The “From” boundary value is always included in the range: [From.
• The To boundary value is defines the end of the range but it is not included in the range: To), except for day of year ranges so you could select a single day: To].
• Curtailment rules based on time, or a variable other than wind speed and direction, may only be used with the power time series calculation, not the frequency domain energy calculation
Definition of curtailment types
Curtailment types map one to one with efficiencies that feed into the net energy calculation. A standard set of curtailment types are provided, but you can extend or re-prioritise these and add your own.
Any unused curtailment types are not included in the calculated efficiencies that input in to the net energy calculation, so don’t worry that you can’t delete the default categories: if you don’t want to use them define your own curtailment types and use those.
Note
The choice of curtailment types applies to all scenarios in the workbook, though the specific curtailment rules may be varied scenario by scenario.