Simulator 16 User Guide - PowerWorld

Make-Up Power Sources
Generator, load, injection group, and switched shunt contingencies may cause imbalances between
generated power and demand. The default way to handle these imbalances is to assign them to the
system slack. However, this is probably unrealistic and, depending on the size of the unit or load
involved, convergence problems may result.
To implement more local compensation for generation, load, injection group, and switched shunt
changes, use the Make-Up Power Sources Dialog. This dialog can be accessed by from the
Contingency Element Dialog by clicking the button labeled Make-Up Power Sources. Most of the
dialog is occupied by a grid that lists bus numbers and relative contributions. This grid is a Case
Information Display, so its behavior should be familiar. For example, right-click on the grid to display
its local menu.
We shall call those buses that must compensate for the changes caused by a generator, load, injection
group, or switched shunt contingency "compensators". To insert a new compensator, select Insert
from the grid’s local menu. This opens another dialog, where you should specify the bus number of the
compensator and its contribution. Specify the contribution of the compensator either as a percentage
or as a fixed number of MW. If a particular contingency has multiple compensators, then the choice of
basis for the contribution (either MW or percent) should be consistent for each. After identifying the
compensator, click OK. The grid should update with your newly added compensator.
To delete an existing compensator, select it from the grid and select Delete from the local menu.
To determine how much each compensator contributes to the imbalance, each contribution value is
normalized to the total sum of all contribution values. This allows the values to be entered in either
percent or MW. Keep in mind that when entering the values in percent that the sum of all contribution
values should equal 100 or the actual contribution amounts will not occur in the expected percentages.
Compensators account for the changes caused by a generator, load, injection group, or switched shunt
contingency by changing either generation or load to satisfy its defined contribution. For example,
suppose compensator contributions are specified as percentages, and Simulator needs to compensate
for 100 MW lost in a particular generation contingency. Suppose the contingency has 4 compensators
defined as follows:
Bus Number Contribution
1 20
2 30
3 10
4 40
Suppose buses 1 and 2 are load buses, and buses 3 and 4 are generators. Then bus 1’s load will
decrease by 20 MW, bus 2’s load will decrease by 30 MW, bus 3’s generation will increase by 10 MW,
and bus 4’s generation will increase by 40 MW. These changes will be instituted regardless of the
compensators’ operating limits or AGC status. In fact, any compensating units will be set off AGC to
ensure that the prevailing AGC control does not distort the dictates of the contingency. Furthermore,
maximum MW limits on generators will not be checked.
If a compensator has both generators and loads attached to it, the generator will take precedence.
The generator will function as the compensating device, and the load will be left unchanged.
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