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ACSL/Graphic Modeller Component Models for Electric Power Education

Steven Pekarek, Member, IEEE and Timothy Skvarenina, Senior Member, IEEE


Abstract - This paper describes the use of detailed models of power system components for undergraduate and graduate education.  The models were developed in a commercial graphically oriented package (ACSL/Graphic Modeller).  At the undergraduate level the models are provided to the student to use as a tool to reinforce lecture and laboratory concepts.   At the graduate level, the models can be used to introduce the student to more advanced topics such as reference frame theory and provide a beginning point for the student to develop more complex models.  Included in the paper is a short tutorial on the use of ACSL/Graphic Modeller and a description of several models including a synchronous machine, induction motor, pulse-width-modulated inverter, and a six-pulse bridge rectifier. Sample studies using each model are shown with suggestions for additional uses by students.  Since the models are detailed, transient as well as steady-state phenomena can be demonstrated with the models. For example, the free acceleration of an induction motor and a three-phase fault on the synchronous generator are among the applications shown in the paper.  The models are provided on the CDROM and can be viewed and executed with a free viewer version of ACSL.


I. Introduction

It is well known that the behavior and operation of electric machines and drives are often difficult topics for students to comprehend and instructors to teach.  Classical methods of teaching machines often focus on steady-state machine performance or reduced-order models, such as the classical voltage-behind-reactance models of synchronous machines, for describing dynamic performance.  Power electronic circuits, such as rectifiers/inverters are usually taught from a textbook based approach, where concepts such as commutation are described in terms of closed form functions of the phase angle delay, output current, and commutating inductance.  Although these methods are effective, several educators have noted the utility of using computer simulation and object-oriented graphical tools to illustrate machine and drive system performance [1-6].  Using these tools, concepts can be made more visual to students.  For example, the commutating inductance or phase-angle delay of a rectifier can be adjusted by the student and repeated simulations performed to determine the effects.  The simulated results can then be used to support corresponding theories.  Simulation of machines can be used to observe steady-state and transient performance, as well as observe the errors of the various approximations used to obtain closed form solutions of the transient behavior.

Recently, the authors have begun to develop a library of machine and drive models for power engineering education using the Advanced Continuous Simulation Langauge-Graphic Modeller (ACSL-GM).  ACSL-GM is a commercial, general-purpose, differential-equation-based, simulation language that provides a graphical front-end for building models in block-diagram format.  ACSL-GM was chosen as a basis for the library for several reasons.  First, models developed within ACSL-GM can be used on either Unix-based or Windows (3.1, 95, NT)-based operating systems, and are cross-platform compatible.  Second, anyone can obtain a free ACSL-Viewer that allows the use of models developed and compiled in the full version of ACSL-GM (navigate, change model parameters, run simulations, print and plot results), without having to purchase software.  This means the models  can be incorporated into homeworks, prelabs, and lectures, without any compatibility issues or financial burden on the students.  Third, the graphical interface provides a means to imbed model complexities within several block layers.  For example,  the block-diagram implementation of a machine model may be placed under a bitmap image of the cross-sectional view of the machine.  The user initially sees the cross-sectional view of the machine and can click-down through the block layers to obtain more model information.  This provides a means to create models that can be used by a wide-range of students (undergraduates and graduates).  Fourth, ACSL-GM is a compiled language, therefore simulations are very time-efficient.  Because of the efficiency, simulations of very large-scale systems, including power electronic-based shipboard and aircraft generation  systems have been developed as part of the authors' research [7-9].  Thus models developed as part of research are easily transferrable to the classroom with little effort, providing an excellent means of integrating research into the curriculum.

This paper includes ACSL/GM models of an induction machine, synchronous machine, controlled 6-pulse rectifier (ideal switching), uncontrolled 6-pulse rectifier (commutation included), and a sine-triangle PWM inverter that the reader can run on either the full version of ACSL or on the ACSL-Viewer.  Mathematical descriptions of the components and simulation structure are included for completeness.  However, the models have been developed for flexibility in terms of student prerequisite knowledge. Bitmap images of the components are used as the first block level, so students do not need backgrounds in reference frame theory, differential-equations, or simulation theories to use the models.  Underlying the bitmap images are block levels that provide the mathematical foundation for more advanced undergraduate or graduate students.  Included with each model are examples of possible uses in lectures, homeworks, or laboratories.  It is shown that a variety of analysis tools can be applied, including eigensystem analysis, model linearization, and FFTs, to support understanding of both fundamental and advanced machines and drives concepts.

In addition to the models, an introduction to ACSL/GM is provided.  This includes instructions on Opening Graphic Modeller, Obtaining Information About a Block, Viewing and Changing Constants, Port Assignments, Plotting and Displaying Variables, and Starting and Running the Simulation.  These instructions are intended to supplement the library of models and provide sufficient detail such that one can download and use the models with very little effort, regardless of previous experience with ACSL/GM. In addition, links are provided to the ACSL homepage, which contains a complete help file and additional tutorial information on using the ACSL-Viewer.  Links to the authors' email addresses are provided if additional support is required.

The models included are a small sample of those needed for power engineering education.  Additional models, including a current-controlled inverter, square-wave inverter, synchronous machine-converter, and an indirect field-oriented vector controlled induction machine, have been developed and can be obtained by contacting the authors.  New models of various drive system components will be developed in an ongoing effort.
 



 

II.  Introduction to Graphic Modeller

III.  Models Developed

A.  Induction motor
B.  Synchronous machine
C.  PWM inverter
D.  Six-pulse bridge rectifier
 


IV.  Conclusions

In this paper ACSL/GM models of an induction machine, synchronous machine, controlled 6-pulse rectifier (ideal switching), uncontrolled 6-pulse rectifier (commutation included), and a sine-triangle PWM inverter are provided for use in power engineering education.  These models  can be used to support lectures, homework, and laboratory education of a wide range of students (both undergraduate and graduate).  In addition, they can be downloaded along with the ACSL-Viewer, at no cost, and run on either Windows or Unix-based operating systems.  Examples of the possible uses of the models are provided which demonstrate the utility of ACSL/GM for performing a wide range of system analysis (linearization, eigensystem analysis, FFTs).  Basic instructions of ACSL/GM are also provided so that the models can be used regardless of previous experience using ACSL/GM.  Interested users can download these models by clicking here. Additional models are currently being developed and can be obtained by contacting the authors.


References

[1] J.B.Patton and P. Jayanetti, "The Making of Multimedia Power Systems Control and Simulation Labware," IEEE Transactions on Education. vol 39, pp 314-319, Aug. 1996

[2] M. Hashem Nehrir, F. Fatehi, and V. Gerez, "Computer Modeling for Enhancing Instruction of Electric Machinery," IEEE Transactions on Education. vol 38, pp 166-170, May 1995

[3] C. Gross, "EMAO: An Aid to Understanding Energy Conversion Device Performance,"  IEEE Transactions on Power Systems, Vol. 11, pp 607-611, May 1996

[4] S. Williams, D. Kline, and R. Ashton, "A New Approach for Teaching Electric Machinery: Object Oriented Electric Machinery Simulation," 1994 ASEE Annual Conference Proceedings, pp 2273-2277, June 1994

[5] B. Fardanesh, "Computer Aided Instruction of Rotating Electric Machines Via Animated Graphics,"  IEEE Transactions on Power Systems, Vol. 7, pp 1579-1583, Nov. 1992

[6] W. Cheung, "Enhanced Learning of Electrical Systems Using PSPICE-A Low Cost Solution," International Journal of Electrical Engineering Education, Vol. 33, pp 39-51, 1996

[7] O. Wasynczuk, E. Walters, S. Pekarek, and H. Hegner, "State Model Generation Algorithm for Simulation/Analysis of Shipboard Power Systems," Proceedings Naval Symposium on Electric Machines, pp 189-195, July 1997

[8] T. Skvarenina, S. Pekarek, O. Wasynczuk, P. Krause, R.  Thibodeaux, and J. Weimer, "Simulation of a More-electric Aircraft Power System Using an Automated State Model Approach," Proceedings of the 31st Intersociety Energy Conversion Engineering Conference, Vol. 1, Washington D.C., August 1996

[9] T. Skvarenina, S. Pekarek, O. Wasynczuk, P. Krause, R. Thibodeaux, and J. Weimer, "Simulation of a Switched Reluctance, More Electric Aircraft Power System Using a Graphical User Interface," Proceedings of the 32nd Intersociety Energy Conversion Engineering Conference, Vol. 1, Honolulu, HI, August 1997

[10] P. Krause, O. Wasynczuk, and S. Sudhoff, "Analysis of Electric Machinery," IEEE Press, Piscataway, NJ, 1995


Author Contact Information

Steven D. Pekarek
Department of Electrical and Computer Engineering
1870 Miners Circle
University of Missouri-Rolla
Rolla, MO 65409-0040
Phone: 573-341-4884
Fax: 573-341-6671
E-mail: pekarek@ee.umr.edu

Timothy L. Skvarenina
1415 Knoy Hall
Purdue University
West Lafayette, IN 47907-1415
Phone: 765-494-7493
Fax: 765-496-1354
E-mail: tskvaren@purdue.edu


Author Biographies

Steven D. Pekarek was born in Oak Park, Illinois on December 22, 1968.  He received the BSEE, MSEE, and PhD degrees from Purdue University in 1991, 1993, and 1996, respectively.  He is currently an Assistant Professor of Electrical Engineering at the University of Missouri-Rolla.  His interests include analysis and modeling of electric machines and finite inertia power systems.

Timothy L. Skvarenina was born in Chicago, Illinois and received the BSEE and MSEE degrees from the Illinois Institute of Technology in 1969 and 1970.  He also received the PhD degree from Purdue University in 1979.  Following a 21 year career in the United States Air Force, he joined the faculty of the School of Technology, Purdue University where he is currently an Associate Professor of Electrical Engineering Technology.  His interests include educational methods and the modeling of electric power system devices and systems.