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Knowledge Base

Creating an Equivalent System

Auxiliary File: Equivalence.aux

PowerWorld Case: B7OPF.pwb

PowerWorld Oneline: B7OPF.pwd

Output Files: none

(Right-click on the above files and select Save Target As to save them to your computer.)

In this example we will use a script to create an equivalent system for one area in a seven-bus case.

The auxiliary file contains three script sections:

  • Base solves the power flow and sets a base case for difference flows.
  • Equivalence creates the equivalent system.
  • PowerFlow solves the power flow and displays the difference flow comparing the original power flow with the equivalent system.

There are two data sections in the auxiliary file.  The first sets options for creating the equivalent circuit, while the second specifies which buses are part of the study system and which are part of the external system.

Equivalence.aux:
//Create an equivalent circuit for bus 6
Script Base
{
//This script will solve the power flow and set the base
//case for difference flows.
//To solve the power flow we have to enter powerflow mode.
Entermode(PowerFlow);
//Solve the power flow:
SolvePowerFlow;
//Set the current state as the base case for
//difference flows.
DiffFlowSetAsBase;
}
DATA (Equiv_Options, [DeleteAllExtGen])
{
//Delete all external generators when creating an //equivalent?
"YES"
}
Data (BUS, [BusNum, BusEquiv])
{
//Specify which buses are in the study system
//(stay the same) and which are in the external
//system (create an equivalent)
//Bus Number      Study or External?
//-----------------------------------
1           "Study"
2           "Study"
3           "Study"
4           "Study"
5           "Study"
6           "External"
7           "Study"
}
Script Equivalence
{
//Now we will create the equivalent system.
//To do this we must be in Case mode.
Entermode(Case);
//Create the equivalent based on the data we entered:
Equivalence;
}
Script PowerFlow
{
//Solve the power flow for the equivalent system
//First enter PowerFlow mode
Entermode(PowerFlow);
//Solve the power flow
SolvePowerFlow;
//Show the solution as a difference flow,
//comparing the power flow of the equivalent
//system to that of the original system.
DiffFlowMode("DIFFERENCE");
//Now look at the difference flow to see if the
//equivalent is a good approximation to the
//original circuit.
//A good approximation will not have many differences.
}

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June 28, 2012