THE USE OF POWERWORLD TO CONDUCT LOAD FLOW ANALYSIS AND POWER FACTOR CORRECTION ON STEVENSON’S 5 BUS SYSTEM Cesar Carbajal Andrew Gast Michael Fleck Sara Page Podolsky Dr.. Clifford Gr
Trang 1THE USE OF POWERWORLD TO CONDUCT LOAD FLOW ANALYSIS AND POWER FACTOR CORRECTION ON STEVENSON’S
5 BUS SYSTEM
Cesar Carbajal Andrew Gast Michael Fleck Sara Page Podolsky Dr Fredrick Berry Jared Dinkelaker Kevin Patel Aalap Jha Dr Clifford Grigg
Department of Electrical Engineering Rose-Hulman Institute of Technology
Terre Haute, IN 47803
Abstract
Load flow analysis is important for
Electrical Engineering students to
understand, but the analysis can often be
long and tedious One way to either check
answers or solve large cases would be to use
a software package such as PowerWorld
PowerWorld utilizes a highly visual
easy-to-use graphical interface A student version of
this program is available at
www.Powerworld.com Since many power
companies use such programs, the software
also helps students prepare for the real
world
Introduction
Load-flow analysis can be better
understood using computer software
packages One of the many load-flow
software packages that can be used is
PowerWorld This package allows for the
easy simulation of bus systems that would
take a significant amount of time if done by
hand One such system is Stevenson’s 5 bus
model This is a relatively small and simple
power system Understanding how this
system works will assist students in
understanding load flow analysis The
results of changes to the system can be seen
quickly in PowerWorld, further aiding
students’ learning process
Description of Powerworld
PowerWorld Simulator is a software package designed to simulate high voltage power systems up to 100,000 busses This package was originally designed for educational purposes; now it is being used in industry as well PowerWorld can be used to give students a comprehensive look at electrical power flow in a transmission grid because it is user-friendly and highly visual
PowerWorld is capable of a wide variety
of functions including detailed modeling of phase-shifting transformers, switched shunts, generator reactive capability curves, generator cost curves, load schedules, transaction schedules, dc lines, multi-section lines, and remote bus voltage control The one-line diagrams are animated for the benefit of the users The integrated drawing tools give an easy and fast approach to creating one-line diagrams, circuit diagrams where a single line is shown to represent three phases of a power system
PowerWorld uses the Newton-Raphson iteration method, which provides an efficient and accurate solution It also computes the Jacobian (Admittance Matrix), so that the one-line diagram characteristics can be ported to other analysis programs
Trang 2Jacobian Matrices
In the manual method of solving multi bus
systems, a Jacobian Matrix is created The
matrix contains values that depend on the
resistances and reactances within the system
This matrix is used in combination with
voltage and current matrices to iterate to a
solution
In PowerWorld, students can place busses,
generators, transmission lines, etc on a
one-line and the program comes up with the
Jacobian for the case It then iterates to the
solution If, for example, a data value needs
to be changed, instead of manually changing
the affected values of the Jacobian and then
recompleting the long iteration process a
student can simply change the data value on
the one-line and PowerWorld will find the
new solution quickly
Application
A one-line diagram of Stevenson’s 5 bus
system modeled in PowerWorld is shown in
Figure 1 Tables 1 and 2 are the data that
corresponds to the system
Figure 1- Stevenson’s 5 Bus System
Table 1- Transmission Line Data
From To Resistance (R) Reactance (X) Charging (B)
Line
The students should open a new project file and create a one-line The help tutorial shows how to place busses, generators, lines and loads Students can build a one-line of the 5 bus system using the input data in Tables 1 and 2, and a picture of the one-line
in Figure 1 The model they have created can be used to conduct a load flow analysis Table 2- Generator and Load Data
Bus Number Bus Name Voltage Load MW Load VAR Gen MW Gen VAR
1 Birch 1.04 65 30 N/A N/A
2 Elm 1 115 60 N/A N/A
3 Maple 1.02 70 40 180 0
4 Oak 1 70 30 N/A N/A
5 Pine 1 85 40 N/A N/A
When students solve the case, the one-line becomes animated, giving a graphical representation of the “flowing” load Also,
a Power Flow List is available for viewing the complete numerical solution The solutions to the case are in Appendix A
Capacitor Study
At times it is necessary to have a certain minimum per unit voltage level at a particular bus If the Power Flow List shows that a bus is too low, one way of fixing this is to increase the power factor This is achieved by adding a shunt capacitance at that bus Finding the particular value of the capacitor can be difficult by applying the trial and error method, so the easiest and most effective way to determine the capacitance that is needed is by adding a temporary generator
at that bus In this case the generator should
be added at bus 4
Trang 3This generator should have a 0 MW
output, like a capacitor would have The
SetPoint Voltage should be set to the desired
per unit voltage at the bus When the load
flow analysis is run again, the reactive
power of the temporary generator is the
value of the capacitor needed to raise the
voltage to the desired value The temporary
generator can now be deleted and replaced
with a capacitor of the value found above, as
shown in Figure 2
Figure 2- One-line with Capacitor
Hand analysis techniques will be very
cumbersome and time-consuming
PowerWorld produces a fast and accurate
solution without requiring iteration by hand
Conclusion
Students can solve practical power flow
systems using PowerWorld’s easy-to-use
graphical interface After building the
one-line diagram students can conduct load flow
analysis Then, they can easily see the
results of making changes to the one-line,
without going through tedious by-hand
calculations The author would be pleased
to provide more detail to interested readers
and can be conveniently contacted via
e-mail at fleckmc@rose-hulman.edu
References
1 William D Stevenson, Jr 1982 Elements
of Power Systems Analysis New York:
McGraw-Hill
2 PowerWorld Corporation 2004 PowerWorld Corporation Internet
<www.Powerworld.com> Date Accessed 12/12/2004
Biographical Information
Cesar Carbajal, Jared Dinkelaker, Andrew Gast, Kevin Patel, Michael Fleck, Aalap Jha, and Sara Page Podolsky, are Electrical Engineering students at Rose-Hulman Institute of Technology who are writing a User’s Manual for PowerWorld as their senior design project Dr Berry, and Dr
Grigg are professors at Rose-Hulman who provided guidance throughout the writing process
Trang 4APPENDIX A
Solution to Stevenson’s 5 Bus System