IEEE Transactions on Energy Conversion. Vol. 9, No. 2, June 1994 263

A Graphical User Interface for Design, Simulation and Analysis of Power Plant Electrical Auxiliary Systems

David C. Yu Nizar Jamal Wenbiao Wang Xi-Guang Zang James R. Brandt University of Wisconsin, Milwaukee

Abstract - An interactive Graphical User Interface (GUI) package for the design, simulation and analysis of a power plant electrical auxiliary system is presented in this paper. The purpose of this package is to assist the engineer in performing non real-time, what-if, analysis in an inter- active and intuitive environment. The package, AUXSYS, is capable of performing load flow and motor starting sim- ulations. It provides a graphical interface for designing the one-line diagram of the plant and analyzing the output of the simulations. It is currently used for modelling Wiscon- sin Electric Power Company’s (WEPCO) power plant electrical auxiliary systems and is implemented for use on PC’S.

Keywords: GUI. PC, Power plant auxiliary system. load flow, motor starting, simulation and analysis package.

INTRODUCTION Graphical user interfaces are the current, widely

accepted, state-of-the-art in human computer interfaces. When properly used, they empower the user by providing interactive and intuitive interfaces to application pro- grams. Power systems analysis applications have benefit- ted from this development and many packages with GUI’s. suitable for analyzing power distribution systems, have been de /.,loped [2,3,4].

A : ovm plant electrical auxiliary system is similar to a large power system and can be analyzed via load flow, fault study etc. WEPC0 accomplished these analysis by linking the plant auxiliary systems with the transmission systems, and executing the load flow programs on its mainframe computers. The programs were run in batch mode and hence the turn-around time was slow. Moreover, appending the auxiliary system to the transmission system presented analysis limitations in the auxiliary system.

In an earlier paper [ 11, we presented a prototype pack- age for simulation and analysis of plant auxiliary systems that was deployed at WEPCO to provide a solution for the

93 SM 460-6 EC by the IEEE Energy Development and Power Generation Committee of the IEEE Power Engineering Society for presentation at the IEEE/PES 1993 Summer Meeting, Vancouver, B.C., Canada, July 18-22, 1993. Manu- script submitted August 31, 1992; made available for printing May 18, 1993.

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A paper recommended and approved

Wisconsin Electric Power Company

above situation. Though it was very graphical, the user interface of the package was inconsistent and confusing. The users underwent a considerable learning curve and the package was not very robust. Based on our experience with the prototype, we designed AUXSYS to considerably enhance the ergonomics of the prototype. The analytical capability of AUXSYS has also been enhanced to model machine transients and sub-transients in the motor starting simulation. In this paper, we present the design and the capabilities of AUXSYS.

DESCRIPTION The purpose of AUXSYS is to provide an easy and

intuitive interface for engineers to study the electrical sys- tems of power plants. It provides a user interface for the analysis of a power plant where the engineer can interact with a graphical model of the plant and analyze the plant through direct manipulation of the model. The graphical model of the system is an extension to the conventional one-line diagram representation of the system. Conven- tional one-line diagrams provide a static view of the sys- tem. In AUXSYS, the one-line diagram is the means of communication between the engineer and the package. To enable this, the one-line diagram representation of the plant is modelled as a dynamic entity, that reflects the cur- rent configuration of the plant. The configuration of the plant is altered by the changing the state of its devices (i.e., a motor may be on-line or off-line, a switch may be open or closed) and data associated with the components of the system.

We model the steps taken by an engineer in studying the plant as (a). design (b). simulation and (c). analysis. In the design part, the visual representation of the devices and the configuration of the plant are created or modified. The simulation part approximates the behavior of the plant for the given configuration. In the analysis part, the results of the simulations are viewed. Iterating through the above steps enables the engineer to perform “what if“ studies on the plant.

To accurately simulate and analyze the electrical behavior of the auxiliary system, the effects of the main network needs to be considered. The power plant electrical auxiliary system can be viewed as an isolated system with boundary lines connecting the plant to the main network. To this end, we separated the plant one-line diagram and the boundary one-line diagram. The boundary system can

0885-8969/94/$04.00 Q 1993 IEEE

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be configured similarly to the plant and can be used to simulate different loading patterns on the plant.

AUXSYS consists of six modules. These are: symbol builder, design, load jlow simulation, motor starting simu- lation, loadjlow analysis and motor starting analysis. The user interacts with the design and the analysis modules using familiar GUI components such as pull-down menus, push buttons, radio buttons, check boxes, editable fields, scroll bars and dialog boxes. The simulation modules are invoked transparent to the user, although the progress of the simulation programs is reported on the screen and the simulation can be interrupted by the user. No sequence of actions is enforced on the user. Pop-up messages inform the user to take any actions that are required for the correct behaviour of the desired operation. The user interface of AUXSYS is presented in figure 1.

In the rest of this paper, the functionality provided by AUXSYS to design and analyze the plant is presented.

Figure 1. The user interface of AUXSYS. The design and analysis modules can be invoked by selecting the correspond- ing button with the sprite. The simulation modules are trans- parent to the user.

DESIGN The underlying motivation of the design stage is to

provide the user with the ability to create one-line dia- grams that maximize visual comprehension of the plant and boundary systems through the use of icons and colors. The user creates the visual representation of the devices and the one-line diagram in the design stage.

Symbols The symbol builder module is used to design the

visual representation(s) (icons) of a device and maintain the catalog of the devices used in designing the one-line diagram. Typically, the representation of the devices will be designed once and reused in multiple one-line dia- grams. Informally, the symbol builder can be described as an icon editor with semantics built into it to represent

these icons as devices. The user interface of the symbol builder includes a

canvas for editing the icons and a scrollable symbol table to catalog symbols that have been designed. The com- mands available to the user are accessible through menus and buttons. The buttons are grouped into two categories; those that pertain to the symbol table and those that pertain to the canvas. This interface is presented in figure 2.

Creating symbols consists of editing the icon for the device on the canvas and associating a device type and state with the icon. The user can draw and erase points, lines and rectangles, move and rotate icons, set the color, define the device type and state. The manner in which the icon connects to the bus or line is specified by selecting one or two special points (hotspots) on the icon. Figures 2, 3 and 4 illustrate a sample session with the symbol builder.

The symbols representing devices are cataloged in the symbol table. The user can delete and modify existing symbols or create new symbols based on existing ones. Two state devices are created by pairing icons. The icon representing the active state of the device (on-line, closed) is displayed in the left column and the inactive state of the device (off-line, open) is displayed in the right column. All symbols representing a particular type of device are dis- played as a contiguous group in the symbol table.

One-line diagram The design module is used to edit the configuration of

the plant and boundary systems and interface to the simu- lation programs. The configuration of a system is defined by the schematic of the one-line diagrams, the data associ- ated with the components and the state of the devices.

The user interface of this module includes a scrollable canvas and a scrollable symbol table. The one-line dia- gram is edited on the canvas and one or more symbol tables, designed with the symbol builder, can be loaded in the symbol table. All commands available to the user are accessible through the menu. The interface of the design module is presented in figure 5.

The one-line diagram is created by installing buses, lines and devices on the canvas. Buses, lines and boundary lines are provided as drawing primitives. They can be color-coded to represent different voltage levels. The one- line diagram can be arbitrarily large and the scroll bars can be used to position the diagram on the canvas. Devices are installed by selecting the icon from the symbol table and choosing the location of the connection on the bus or line. The semantics of this installation are automatically cap- tured by the design module. Thus, installing an open cir- cuit-breaker on a bus. automatically splits it into two buses. The state of the device and its location on the bus or line can be modified interactively. These features make it easy to change the configuration of the system for analy- sis. For example, a motor can be moved across a breaker

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and the breaker can be toggled open to analyze the effect of this configuration. The parameters associated with the individual bus, line or device can be entered by means of the forms based interface provided. Sample forms for entering the bus and motor parameters are shown in fig- ures 6 and 7.

Utility functions are provided in this module to allow the user to obtain hardapy printouts of the one-line dia- gram(~) and search the plant and boundary one-line dia- gram for a bus by name. The print dialog is shown in figure 8.

ANALYSIS The simulation modules are invoked on the plant and

ing the appropriate menu item. The parameters required to run the simulation are prompted for, with dialog boxes, in

boundary configuration from the design module by chaos- Figure 2. The user interface of the symbol builder module. figwe shows a generator icon being designed. The sprite

point^ to the hot spot of the icon. the design module. The dialogs through which these parameters can be entered, for the load flow, static and dynamic motor starting simulations, are presented in fig- ures 9,13 and 15, respectively. The data required for run- ning the simulation is generated automatically from the current configuration of the plant and boundary systems. The parameters of the on-line devices located at the bus and line are included in the bus and line data respectively. Consistency checks are made to ensure that the plant and boundary one-line diagrams are connected and all relevant data, for on-line devices, have been input. Figure 16 illus- trates the message displayed when the one-line diagram is disconnected and there are isolated buses in the system.

Load flow The simulation of the plant is achieved using the fast

decoupled load flow. The user is presented with a graphi- cal output of the real and reactive convergence of the bus power mismatch during the simulation and has the option of interrupting the simulation. This is helpful when the system is unstable and the simulation does not converge to a solution. The simulation program also automatically detects non-convergence. The interface of the Zoud~70w simulation module is shown in figure 10.

On successful completion of the simulation, the load flow analysis module is invoked automatically with the one-line diagram of the system and the results of the simu- lation. The user interface of this module includes a scrolla- ble canvas on which the one-line diagram of the plant or boundary system can be viewed. The interface of this module is shown in figure 11. The user can view the results, such as bus voltages, generation, mismatch, line flows etc., by choosing the appmpriate item from the menu. The real and reactive components of the result are displayed on the one-line diagram beside the correspond- ing bus, line or device. The scroll bars can be used to view the output on any portion of the one-line diagram.

Figure 3. state. The setting in the dialog speclfy the icon as the represen- tation of an on-line motor.

The dialog for specifying the device type and

Figure 4. The dialog for specifying the color of the icon. This figure shows the color being changed for an icon repre- senting a transformer.

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Figure 5. ure shows a part of WEPCO’ Oak creek power plant. The mode menu displays other actions available to the user.

The user interface of the design module. This fig- Figure 8. Hard copy output of the one-line diagram can be obtained through the print dialog. A similar dialog is provided in the loadflow analysis module for printing results.

Figure 6. The form for entering the bus parameters. The type of the bus is specified through radio buttons. The grid shown on the canvas helps in drawing the one-line diagram.

Figure 9. Clicking on the Ok button creates the input data for the simula- tion and invokes the loadflow simulation module.

The form for entering the load flow parameters.

F i n 7. the motor will not be used in the motor starting simulation then only the full load real and reactive power are required.

The bnn for entering the motor parameters. If Figure 10. The user inter€ace of the lwdflav simulation module. A continuous graph of bus power mismatch to the number of iteration is plotted. The axes are auto-scaled.

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The user can switch between the plant and the bound- ary one-line diagrams to view the load flow results for the c-ding system. Figures 11 and 12 show sample load flow results for the plant and boundary system respec- tively.

Motor starting AUXSYS provides for two methods of motor starting.

These are the static and dynamic motor starting. A maxi- mum of four mom can be started per simulation.

In static motor starting, a load flow simulation is per- formed on the system, in which each motor load is multi- plied by a CoIlstant factor. This factor can be specified on a per motor basis. Figure 13 ill- this interface. The output of the simulation is analyzed by the loadpow anal-

Figure 1,. The user interface of the wfIow analysis ySis module. Figure l4 presents a analysis.

d o n of *' de. his figure shows line loss in the plant. The output menu shows alternate results that can be displayed.

In dynamic motor starting, the machine transients and sub-transients can be studied. The motors can be started either simultaneously or sequentially. The motor starting simulation is perfcmned by a variation of the method described in [5].

During the simulation, the user is presented with the graphical output showing the convergence of the real and reactive bus power mismatch. In sequential motor starting, the user is given feedback on the current status of each motor, and is informed as each motor is brought on-line during the simulation. The interface of the motor starting Simulation module is presented in figure 17. The motor starting analysis module is automatically brought up on completion of the dynamic motor starting simulation.

The user interha provided by the motor starting module a simulation panel and a canvas

axis) against time (X-axis) is plotted on the canvas. The simulation panel contains four sub-panels and allows for up to four different motor starting simulations to be com- pared at one time. Each simulation result is presented in a separate sub-panel and each motor started in the simula- tion is presented as a button in the panel. The button con- tains the icon used to represent the motor in the oneline diagram, the name of the bus at which the motor is located and the color of the curve used to plot the parameter of that motor. Clicking on the button eithex plots or erases the curve for the represented motor h m the plotting canvas. This interfax is presented in figm 18.

The parameters that can be viewed include slip, speed, torque, current angle and magnitude, voltage angle and magnitude. These are displayed on the canvas by choosing the appropriate menu item. The Y-axis is auto- matically and labelled to the Of the Flgure 13. The form for entering the static motor starting data to be presented' The Obtain a hardcopy printout of the plots through the print dialog shown in fig- ure 19.

Figure 12. The bus load in the boundary system is shown

component for for plotring The Of motor meters v- here. red is displayed bp of the reactive

parameters. The motors on buses 15 and 17 are being started.

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Figure 14. ing simulation of figure 13. This can be compared with figure 11. simultaneously.

The line loss resulting from the static motor start- Figure 17. tion module. Here, motors on buses 15 and 23 were started

The user interface for the motor starting simula-

Figure 15. Clicking on the Ok button invokes the motor starting simula- tion module on the current configuration of the system.

The dynamic motor starting parameter dialog. Figure 18. module. The results of starting motors on buses 15 and 23 sequentially and simultaneously are compared here.

The user interface of the motor starting anulysis

Figure 16. The message is displayed, when the one-line dia- gram of the system is disconnected and there are isolated buses in the system, is shown here.

Figure IQ. The print dialog for the motor starting analysis module. Each parameter plot or all of them can be printed.

INSTALLATION REQUIREMENTS AUXSYS was implemented on a PC using C and a

graphics library for display. The requirements for running the system are:

IBM PC compatible system VGA card, with a minimum screen resolution of 640 x 480 and 16 colors 1MB of Expanded memory mouse; the keyboard can be used in the absence of a mouse.

CONCLUSION An interactive GUI package to assist in the analysis of

power plant electrical auxiliary system was presented in this paper. The features of the package that help engineers in the visual dissemination of information during the design, simulation and analysis of the auxiliary system was described.

This package is currently used to model WEPCO’s power pIants with wider deployment planned in the near future. This package is also being used as an instructional aid in Power systems courses at the University of Wiscon- sin-Milwaukee.

ACKNOWLEDGEMENTS This project is funded in part by a grant from the Wis-

consin Electric Power Company. We would like to thank Qiu Xiaole and Naveen Jamal of University of Wisconsin- Milwaukee for their comments and technical assistance. The engineers at WEPCO provided valuable feedback on the prototype and the various versions of AUXSYS, their assistance is gratefully acknowledged. The authors would also like to thank Unify Corporation for providing the facilities to prepare this paper.

REFERENCES D. C. Yu, S. Chen, and R. Kalscheur, “A PC- Based Interactive Graphical Simulation and Analysis Package for A Power Plant Electrical Auxiliary System”, IEEE Transaction on Power Systems, Vol5. No. 2, May 1990. D. C. Yu, S . Chen, and R. F. Bischke, “A PC Ori- ented Interactive and Graphical Simulation Pack- age for Power System Study”, IEEE PES Winter meeting, Paper 88 WM 057-2, Feb 1988. N. Pahalawaththa, C.P. Arnold, M. Shurety, “A Power System CAD Package for the Workstation and Personal Computer Environment”, IEEE PES Winter meeting, Paper 90 WM 070-3, Feb 1990. M. Foley et al., “An Object Based Graphical User Inkrface for Power Systems”, IEEE PES Winter meeting, Paper 92 WM 1834, Feb 1992.

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BIOGRAPHIES David C. Yu (S’ 78-M’84) was bom in Kaohsiung, Tai- wan, R. 0. C on December 12,1955. He received the B. S. degree in Electrical engineering from the Chung-Yuan University, Taiwan, and M. S. and Ph. D. degrees in Elec- trical engineering from University of Oklahoma in 1977, 1979 and 1983 respectively. Currently he is an associate professor in the Department of Electrical Engineering and Computer Science at the University of Wisconsin-Mil- waukee.

5 .

Nizar Jamal was born in Syracuse, NY, USA on May 23, 1967. He received his B. E. in Electrical and Electronics engineering from Annamalai University, India and M. S . in Computer Science from University of Wisconsin-Mil- waukee in 1987 and 1991 respectively. Currently, he is a software engineer at Unify Corporation, Sacramento.

Wenbiao Wane was bom in China, on April 12, 1963. He received the B. S. from Tsinghua University, China in 1986, and M. S . from University of Wisconsin-Milwaukee in 1992, both in Electrical engineering. He is currently with Stratagem Inc., Milwaukee.

Xi-Guanv Zar?g was born in Beijing, China on April 17, 1959. He received his B. S. in Mathematics from Beijing University, China and M. S . in Mathematics and M. S . in Computer Science from University of Wisconsin-Milwau- kee in 1982, 1988 and 1990 respectively. Currently he is a software engineer at CAP Gemini America, Milwaukee.

James R. Brandf received his Associate degree in Com- puter Engineering Technology and B. S. in Electrical Engineering Technology from Milwaukee School of Engi- neering in 1974 and 1986 respectively. He has been with WEFT0 since 1974 and is involved in technical software programming, power plant data acquisition and miscella- neous computer application support. Currently he is a con- trol equipment engineer at WEPCO.