Performing_Calculations
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F.3 Performing Calculations Perform a load flow with the option Consider Reactive Power Limits enabled (see Figure F.5). Correct the system in case of errors.
Fig. F.5:
Consider Reactive Power Limits in the Load Flow Calculation
The secondary controller function for the power system (frequency control demand and power production) is performed by the top generator alone. fixed to a certain PQ setpoint (active and reactive power). Due to these generator is heavily overloaded. However, it is not possible to simply set mode, because this would create three reference busbars which would all degrees.
=> equilibrium between power The other two generators are control settings, the upper all generators to the "SL'' (slack) have a voltage angle of 0.0
The solution is to select one reference busbar, for which the voltage angle will be 0.0 degrees, and to create a frequency controller object which will regulate the power output of the generators. Edit all three generators: -
Reference Machine = disabled
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Local Voltage Controller = Voltage
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Active Power = 100.0 MW
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Voltage = 1.0 p.u.
This gives all generators a "PV'' characteristic. Define the power frequency controller: -
Select the upper terminal "B110_1a" of "Station 1" and the three generators (by clicking on them while holding the Ctrl key pressed).
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Right click the selection and choose the Define --> Power-Frequency Controller option. The edit dialogue of a power frequency controller will appear.
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Performing_Calculations
Fig. F.6:
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Defining a Power-Frequency Controller
The power-frequency controller already has the "Bus Bar of Frequency Measurement'' field set. The selected generators are in the machine list. -
Enable the option According to Nom. Power. In the 'Basic Data' page, set the name of the controller: Name = ''Secondary Control''
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Close the controller dialogue with OK.
The new element ''Secondary Control'' has been created in the database. It is also possible to add generators to an existing frequency controller. This is done from the single line diagram: -
Multi select the generators, right click the selection.
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Select the Add to --> Power-Frequency Controller. A list of existing frequency controllers is shown from which the one must be selected for addition to the generators.
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The frequency controller dialogue appears. The generators are now added to the machine list unless they are already contained in it.
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Close the frequency controller dialogue.
The load flow will be different now: Open the load flow command. At the 'Active Power Control' page, enable According to secondary control. Perform a load flow. Observe the changes: all generators are now producing equal real power. The power contribution is not fixed but can be changed in the frequency controller by setting it to Individual active power and editing the percentages in the list. The frequency controller can be reached by opening the dialogue of a participating generator. The controller object is mentioned on the 'Load Flow' page as External Secondary Controller. The button beside it can be clicked to jump to the controller. This concludes the fourth exercise of the tutorial.
DIgSILENT GmbH www.digsilent.de Tel: +49 (0)7072 9168-50 Fax: +49 (0)7072 9168-88
[email protected]
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