Add External Objects

The final step in creating the AC power flow model is to add external objects to the nodes of the power system. External objects in SAInt are used to inject or extract energy from the node. This tutorial will focus on creating the demand and generator externals for the flag-shaped power system. The objective is to learn different methods to create external objects and define their properties. A future tutorial will explain in detail how these properties affect the behavior of the different externals.

Each external object must be assigned to a node object within the network, and there is no limitation on the number of externals assigned to a node.

1. Add demand via the map window

Externals can be added to a network in multiple ways. We will first use the map window. Right-click on NODE2 and use the Add New External  Electric Demand option from the context menu (Figure 1). Once selected, the property editor of the electrical demand object will appear. Use the property editor to change the Name to DEMAND1, power factor (PWF) to 0.85. Moreover, select ind from the drop-down menu of the power factor type (PWFType) property.

The ind property value represents an inductive load, while res and cap represents a capacitive and resistive load, respectively.
create ext object 00
Figure 1. Add an electric demand object to NODE1.

2. Add generic generators via the model explorer

The model explorer on the left side of SAInt GUI can also be used to add external objects. Right-click on NODE1 in the model explorer and select Add New External  Generic Generator. Once selected, the property editor of the generic generator (XGEN) object will appear. Before defining the generator properties, we will add a second generic generator to NODE3 by following the same procedure.

create ext object 01
Figure 2. Add a generic generator object to NODE1.

2.1. Define generic generator properties

We can define the properties of generic generators via the property editor or an object table (accessible from Table tab  XGEN on the ribbon bar). Use Table 1 shown below to define the properties of the two generic generators. These properties model generators' operational limits and voltage magnitude set points.

Table 1. Generators properties.
Name Node name Default maximum active power Default minimum active power Default maximum reactive power Default minimum reactive power Default active power compensation factor Deafult voltage magnitude set point

Name

NodeName

PMAXDEF [MW]

PMINDEF [MW]

QMAXDEF [MVAr]

QMINDEF [MVAr]

PFSETDEF

VMSETDEF [pu]

NG_GEN1

NODE3

250

90

200

-200

80

1.03

NG_GEN2

NODE1

200

30

160

-160

20

1.01

  • The VMSETDEF is a pre-determined value for the desired voltage output of a generator. The generator uses this set point to regulate the voltage output, which helps to maintain a stable voltage level in the network.

  • The PFSETDEF property value determines the contribution to the active power unbalances between schueduled supplies and demands. In this network, the unbalances would be caused by the resistive losses in the lines.

3. Add wind generator object

Finally, add a wind generator to NODE4 using the model explorer. Select Add New External  Wind Generator from the context menu of NODE4 (Figure 3). Use the property editor to change the (Name) to WIND_GEN3, and default maximum active power (PMAXDEF) to 80 [MW]. Open the GEN object table from Table tab  GEN on the ribbon bar to ensure that the properties of the three generators have been defined correctly.

create ext object 02
Figure 3. Add a WIND generator object to NODE2.

4. Add labels for the externals

Using the map window, let’s add labels to the three generators and one demand object. Right-click on NODE1 and select Add New Object Label To  XGEN.NG_GEN2. Once the label is displayed on the map window, edit the label properties using the property editor of the label. Right-click on the label and select Open Editor. From here, we will edit the label information to display the following properties:

  • Object name (Name)

  • Default maximum active power (PMAXDEF)

  • Active power set point (PSET)

  • Voltage magnitude set point (VMSET)

  • Active power (P)

  • Reactive power (Q)

In the property editor window, change the LabelInfo property to Name: {@.Name}, PMAXDEF: {@.PMAXDEF}, PSET: {@.PSET}, VMSET: {@.VMSET}, P: {@.P}, Q: {@.Q}. The label’s look can be edited by changing the different properties under the background, font, frame, and visibility categories. Optionally, you can use Table 2 to edit the look of external labels (Figure 4). Next, follow the same procedure to add labels for NG_GEN1, DEMAND1, and WIND_GEN3. Refer to Figure 4 for the LabelInfo property values for other generators and demand objects.

Click here for more details about custom external labels.
Table 2. Custom label properties for external objects.
Background

FillColor

32,0,197
Font

LabelFont

Calibri, 8pt

LabelFontColor

245,245,245
Frame

LabelFrameVisible

TRUE

RoundedLabelFrame

TRUE

StrokeWidth

1

FrameColor

32,0,197
Visibility

LabelVisible

TRUE

LabelStartZoomLevel

25

LabelUntilZoomLevel

27

LabelOpacity

100
create ext object 03
Figure 4. Example of labels for external objects. In the figure, the label for WIND_GEN3 is selected.

5. Save network data

To save our new flag-shaped power system we will need to save the network file. Go to network tab and select Save  Save Electric Network. This will save the network file with the new topology and objects.