nature of the design projects. These design projects include 'Integrated Optimal Power Flow and Dynamic. Security Design', 'Hybrid Transit Electric Vehicle', and.
Optimizing a Design Based Undergraduate Power Engineering Education Program James A. Momoh , Peter Bofah, and Arunsi Chuku Department of Electrical Engineering Howard University, Washington DC 20059 Abstract Howard University is continually renewing its engineering program for fast integration of new and developing technologies. The continuing effort is to further incorporate design in the curriculum up-date of undergraduate engineering programs. The objective is to make our products more competitive in the new world and labor environment. This philosophy has been applied to a traditional electrical engineering option, the electric power engineering program, which had been experiencing decreasing intake. This paper presents a success story at optimizing a design based undergraduate power engineering education program at Howard University. The basic philosophy, methodology and results obtained are discussed. Sample projects carried out by students are briefly presented and these demonstrate the broad base and multi-disciplinary nature of the design projects. These design projects include ‘Integrated Optimal Power Flow and Dynamic Security Design’, ‘Hybrid Transit Electric Vehicle’, and ‘Medicine Bottle Opener’. The overall effect has been to improve professionalism and problem solving skills and increase self esteem of students, and thereby, their productivity. It has heightened interest and awareness of the electric power program, increased both the number of students graduating in the electrical power program and the retention ratio. The lessons learnt will be of value to other engineering schools. I.
INTRODUCTION
Traditionally, there exists a gap between the academic and the working environments, and industry usually tackles this by training young engineers in their environment for months before expecting productivity. The objective of including more design in the curricula is to bridge or reduce this gap significantly. The constant pressure of competition the world over, requires this to be an on-going process. At Howard, as an example, the program is designed to address: * Faster integration of new technologies in the industry. * Role of inter-disciplinary courses in the engineering curriculum. * Strategies for solving industry real-time problems.
To meet these general demands, a top down approach has been taken by Howard University Electrical Engineering Department to enhance the curriculum with the following characteristics: * Effecting good problem solving skills * Promoting students’ abilities to deal effectively with technical ambiguities * Developing good inter-personal skills and keen awareness of human elements * Cultivating the good team player attitude * Teaching broad awareness of industry practices and expectations of newhirees. * Incorporating cost-benefit analysis in problem solutions. The expected technical and economic growth for the year 2000 may require additional manpower. However the number of women, African Americans and Asian Americans, applying to engineering schools has steadily been on the decline. This group is vital to providing the additional skill base for coping with the US industry labor short-fall by the year 2000 and beyond. The short-fall if not timely addressed, could affect the U.S.A.’s competitiveness in years ahead. II.
A.
PROGRAM DEVELOPMENT
Catalysts for Change Several forces have promoted changes in the Electrical Engineering curriculum in recent years. The IEEE and other associations have been inspirational for the new educational philosophy of including more design courses in the curriculum. Several workshops, sponsored to improve awareness of design issues have also acted as catalysts. Through a generous grant from the NSF, several coalitions of schools have been founded to study the issue of curriculum renewal. Howard was one of the first universities, along with Massachusetts Institute of Technology, Penn State, University of Maryland, City College of New York, Morgan State University, and Washington University to form a coalition called “Engineering Coalition for Scholarship and Excellence in Education” (ECSEL). Other coalitions since then have also been formed. At Howard University, through ECSEL, the Electrical Engineering Department has been involved in developing new design contents in courses across the
curriculum. In effecting these curriculum changes, ABET accreditation reports have acted as guide. The need to include design issues in Electrical Engineering courses has also been the main concern. In order to carry out this task successfully, it is necessary to ask the following questions: 1. What will the typical US industry/factory look like in the year 2000 and beyond? 2. In what areas are US industries lacking in competitiveness? 3. How do we as engineers plan to meet the challenges of international competition? 4. How will future electrical engineers meet these challenges? Based on the above challenges, general broad guidelines have been laid down for curriculum development. The guidelines recognize the need for indepth awareness in both business and leadership issues in the new curriculum development. Some of the general guiding principles are: 1. New courses should be developed with emphasis on attracting students to engineering disciplines. 2. The core electrical engineering curriculum should be highly structured, integrated, and enriched with new design tasks and exercises which involve computer use and experimental techniques.[1] The role of the computer is to be important in all courses. While the implementation of the above guidelines may improve engineering enrollment, retention and US competitiveness, it may not solve adequately the power industry manpower problem. One has only to pickup the national daily papers and look at the employment section to glimpse at the areas where the attractions are in the electrical engineering field. There is need for an added effort in attracting students for careers in the electric power industry. The rest of the paper discusses a program which is a success story in optimizing a design based undergraduate engineering education program. B.
The Electric Power Engineering Program The objectives of this program, simply stated, are: * To produce high quality first degree engineers for the electric power industry. These engineers will require minimum additional training by the industry to become productive. * To attract, at least, the top ten percent of graduating engineers to pursue advance degrees in the electric power system field. * To attract a greater percentage of students admitted into the electrical engineering program to pursue careers in the electric power industry. To accomplish this, power systems, electric machines and power electronics courses have been
remodeled to increase their design contents, computer usage and the application of modern analytical tools. Added to these improvements is the remodeled senior design project course which has generated this success story. The design projects chosen must be comprehensive, possessing technical, economic and ethical components. The criteria for the choice of design projects are: 1. It must apply fundamental concepts learned from two or more courses. 2. It must be a current problem that industry and society are thinking of. 3. It must encourage group work and the sharing of responsibilities. On the execution of their projects the students also learn how to utilize modern tools and packages in their analysis. These include expert system, neural network, and fuzzy logic packages to help them arrive at a final decision where alternative solutions do exist. It should be noted that before this stage, the students are already well grounded in fundamental courses such as electrical machines, circuit theory, electromagnetic theory, and signal processing. Their understanding of these courses have already been adequately tested in laboratories and mini-projects. The senior design projects involve advanced thinking, creativity and the synthesis of fundamentals learnt in several courses. III.
IMPLEMENTATION DESIGN PROJECTS
OF
SENIOR
Effort is made to spread the design topics throughout the areas of power system, electric machines, controls and power electronics applications. Two faculty members are cardinal to the success of a design project. These are: 1. The course coordinator who coordinates all the design projects. He delivers the weekly general design lectures, and conducts presentations for both the preliminary and final designs. 2. The faculty technical advisor on a design project who works closely with the student in the choice of a design topic, the execution of the project, and the preparation of preliminary and final design reports. The organization and execution of the design projects follows the steps below: a) Design Proposal or Formulation. This involves the student and a faculty technical advisor working closely to identify a viable design topic. The proposal is then submitted to the course coordinator for approval. The student defends his design proposal in class for peer review before final approval is given.
b) Course Coordination Strategy. On weekly basis the course coordinator meets with the entire class to teach design issues related to project management, quality control, simulation methodologies, ethics, safety, patents, copyrights and project evaluation criteria.[2, 3] Good writing skills and good presentation styles are reinforced. c) Project Advisor. The faculty advisor who was involved in the choice of the design topic serves as the consultant to the student. He also serves as a resource person to the student in terms of problem formulation, methodology and analysis. A minimum of one hour of consultation per week is required. d) Progress Report/Preliminary Design. Both the course coordinator and the faculty technical advisor are involved in monitoring the students’ progress. While the technical advisor is involved in the technical details of the project the course coordinator works at the professional content. It is the course advisor who also organizes the presentation of the preliminary design to the entire class. e) Final Design and Report. From the comments received on the preliminary design, the student in consultation with the technical advisor, makes the modifications necessary to produce the final design. [4] Improvement in writing skills is one of the cardinal objectives of the senior design project. Using guidelines provided by the department, the student, in consultation with the technical advisor produces a final report of his design project.[8] f) Electrical Engineering(EE) Day Presentation. This is the day on which the students present their design projects before a public audience. On this occasion, they have the opportunity to invite their parents, friends and juniors to witness the presentation. It is a special day not only for the students, but for the department since special guests usually from government and industry, are invited to this event. IV.
SAMPLE STUDENTS’ PROJECTS
In this section of the paper the summaries of design projects performed by two seniors are presented. a Senior Student - Dominic L.Williams Integrated Optimal Power Flow and Dynamic Security Design. Objective of the Project The objective of the project is to design a method of Integrating Power Flow and Dynamic Security Assessment programs. The new program which combines optimization and security assessment procedures is tested
on a simple 4-bus system. The results from the integrated design are compared to a more conventional method of determining system stability by using an in house package, Howard University Transient Stability Program (HUTSP). Theoretical Formulation The optimization problem is stated as: N 2 Min F Pg = ∑ i + i Pgi + i Pgi − (1) subject i =1 to min max min max and V gi ≤ Vgi ≤ V gi Pgi ≤ Pgi ≤ Pgi where Pgi is the real power generated and Vgi is the terminal voltage of the generator The stability constraint is checked by utilizing the direct solution method employing energy functions to compute the Transient Energy Margin (TEM) as an index for angle cr cl stability. Defining w as the critical energy, and w as cr cl the clearing energy, if TEM ³ 0, then w > w , the system is stable. cr cl For TEM < 0, then w < w , the system is unstable. The detail formulation and analysis is shown in the students report and text books on stability [5, 6].
( )
(
)
Design Implementation The design implementation algorithm follows the steps outlined below:
a) System Data Preparation Data in terms of generation parameters, transmission line parameters, system load requirement and switching parameters are prepared for the study. b) Objective Function Selection The objective function for the optimization is selected. Possible choices include minimization of production costs, system losses or voltage deviations. c). Optimal Power Flow The optimization problem is solved utilizing an in-house package called Robust Interior Point Power Flow (RIOPF) Program. d) Transient Stability Check Employing a transient stability package utilizing transient energy functions, the transient stability is checked. If the stability constraint is not satisfied, the fault clearing time is adjusted for the contingency being studied. If the system is stable, another contingency is chosen and the study repeated for steps (c) and (d) until all contingencies have been studied. Design criteria involving economics, sensitivity, ethics and alternate designs were included in the analytical procedure.
Results and Conclusion The program was tested on the 4-bus system for several contingencies and different objective functions. Figure 1 shows the production cost per hour for different system contingencies. Li is the contingency with line # 1 faulted and out of service. Comparison of the results with conventional methods show that accuracy is maintained but much savings is achieved in time needed to obtain these solutions. The student also learnt that the software packages for optimal load flow and transient energy margin index are licensed and cannot be modified or copied for profit purposes.
Due to technological advances in the aviation jet engine, gas turbines have been developed for several applications including helicopters, boats, trains and stationary ground power. The gas turbine has several advantages over reciprocating engines. These include low emissions, multiple fuel capability, no cooling system, compact size and low weight, and high reliability. Recent years have also seen revolutionary advances in power electronics technology and has aided the development of modern passenger trains. Electric motors utilizing efficient solid state power devices offer infinitely variable power and speed control. These motors can also be controlled to act as generators. Market Survey and Research A survey was done on available vehicle sizes and corresponding motors. Table 1 gives the typical values of these vehicles, motors and other parameters. Also surveyed are manufacturers’ data on motors, various batteries and permanent magnet motors. These form basis for comparison with theoretical calculations. [7] Mathematical Formulation The force, torque, and horse power equations were developed for the motor. These calculations were simulated in a computer program. The force required to propel the vehicle is given by
Figure 1: Plot of Fuel Cost for Different Contingency Cases
F( , T( ,
) = R + W sin
Π + ma + 180
− − − (2 )
The required torque is given by
) = F(
, ).r − − − − − − − − − − − − (3)
b Senior Student - Johnestal L. Norvell Hybrid Transit Electric Vehicle Design Objective The individual objectives of the project, which is a part of a larger project team, are: • Induction motor studies in terms of size, power density and cost. • Electric traction motor studies to ensure efficient vehicle performance. • Application of advanced control algorithms to strategically turn on the larger power loads on the bus including air conditioning and air compressors.
where R = Rolling force inlbs. W = Weight of vehicle inlbs. m = Mass of vehicle in Slugs a = Acceleration in ft/sec2 = Angle of iclination in degrees = Air resistance force in lbs. r = Effective radius of the wheel in ft.
Background of the Hybrid Electric Vehicle Recently, the concern of the public has heightened on the need to minimize pollutants into the atmosphere from automobile exhausts. Government agencies such as the Department of Energy (DOE), and NASA have intensified research and development of alternate automobile technologies to help minimize emissions.
Results and Discussion Given the following design parameters: R = 525 lbs W = 30,000 lbs M = 931.67 Slugs a = 2.93 ft/sec2 = 0, 5, 10, ..., 45 = 0, 10, ..., 50 r = 1.725 ft
Implementation A computer program is developed to compute the force, torque, energy and horsepower for various design parameters.
Tables of force, torque and are developed for various values of angle of inclination and air resistance. For example, considering the velocities of interest as 30-50 mph and for an acceleration of 2.2 ft/s2, the requirement will be between 230-290 hp. Using the computed torque, horse power and available motor characteristics, a suitable motor can be chosen. From the ac-induction motor size studies and corresponding horse power calculations, it was found that the Westinghouse motor was a very good representation of the operating conditions needed to propel the electric vehicle.
Cost Analysis An important economic consideration is to select motors which can result in substantial savings in energy. Improvement in power electronics will further contribute to this. The survey revealed that the cost of electric vehicles are still on the high side. However, with improvement in efficiencies and weights of batteries, motors and advanced
control techniques, the cost can be considerably reduced in the near future. Safety and Ethics One of the objectives of the electric vehicle project is that it will minimize emmissions to the atmosphere, leading to a safe environment. Safety tests also conducted on these vehicles, such as the Electricore’s Solectria E-10, have shown that they met standards set by the Transportation Resource Center (TRC). Ethical considerations involve the development of electric cars and transit vehicles which are affordable to the general public. The technology developed should also be shared for the advancement of science and technology. Initial work was done on the power management algorithm. However, this sector of the research is being pursued more in detail by researchers in the Center for Energy Systems and Controls. Other students, have also done more directed work on different batteries available and their characteristics.
Table 1 : Typical Electric Vehicle Sizes and Motor Parameters Type of Weight Bus (30,000) Van (7,000) Car (2,500)
Max. Velocity 55 56 100
c Student Name: Andrea Oates Medicine Bottle Opener Design Objectives The medicine bottle opener is intended for use by the physically disabled people who are unable to utilize either or both hands. It is to be provided at a low cost with minimal operation. Safety and ethical issues are considered. It must be portable and operate at low power consumption for efficiency. Background The physically disabled endure many stresses of everyday living. There is loss of independence. The medicine bottle opener will provide a means of giving back a vital portion of such person’s life by enabling the individual to perform the not-so-simple task of opening a prescription medicine bottle which may need frequent opening for use of prescription. The opener is to be pushbutton operated. Design Steps The opener must be compact, portable, low power, push-button operated and low cost. The motor
Motor hp 180 66 94
Motor kW 135 49 70
Power Density 36 12 94
should allow for fast removal and replacement of the bottle cap. Table 1: Bottle Dimensions (in inches) Parameter Bottle A Bottle B Height of bottle and 2.560 2.560 cap Top radius 0.750 0.375 Bottom outer radius 0.650 0.450 Bottom inner radius 0.590 0.390 Linear Depression 0.200 0.125 Displacement of cap To remove or replace the cap, the operator will press and release a control button. In the design two typical bottles are considered with characteristics shown in Table 1. The opening of the bottle involves depression of the cap (top) and twisting of either cap or base in any direction.
Table 2: Load Requirements Load Requirements Linear Depression of Cap Force for Depressing Cap Rotation angle-range of Cap Force of Rotation
Bottle A 0.2 “
Bottle B 0.125 “
11 lbs
8.1 lbs
20.5º -36º
20º - 45º
8.8 lbs
6.5 lbs
excitation sequence generator (flip-flop states), a timing system and phase signal amplifier to drive the stepper motors. The cost of the opener is about $72. With mass production, it could come down to $50. The device is safe and lightweight constructed from plastic housing. V.
The above information is necessary in the design especially for motor selection and cam design, since the cap depression requires motor-cam combination operation. For limitation of space, partial design of the opener is shown in Fig. 2.
Other excellent design projects have been performed but which space do not permit us to report. These include: • Fault diagnosis in power distribution systems using artificial neural networks. • Preventive/corrective control for voltage stability assessment using artificial neural networks. • Control systems for hybrid turbine electric vehicle. • Framework of unbundling power systems services and costing. VI.
Figure2: Medicine Bottle Opener Design
Motor selection and Control Two stepper motors are selected to complete the design, one for depression of the cap and the other for rotation of the base. Control Depress the cap by 0.2” and rotate base by 27º in 30 sec. operation. The control circuit consists of
OTHER DESIGN PROJECTS
ENHANCING ATTRACTION AND RETENTION OF STUDENTS
Two positive actions have been taken towards enhancing and retention of students in the electric power program. A power plus club for power students and run by students has been formed. The club meets biweekly to discuss projects and issues in power system engineering. Four power professors act as advisors but only to attend special events and meetings. This forum for the exchange of ideas also develops professionalism among the students. A mentor system has also been put in place to encourage students’ participation in providing tutorials to juniors. The students have also acted as mentors to precollege/high school students in summer outreach programs organized by the Energy Expert System Institute of the Department. This program has tended to enhance the students self esteem of themselves in the electric power system profession. The result of both the power plus club and the mentor program has been to attract more students and increased retention. The students response has been very encouraging. They assert that the program has improved their study habits and problem solving skills, and increased their awareness and interest in the Electrical Engineering profession. The percentage of graduating students majoring in electric power has also increased. VII. FUTURE
IMPROVEMENTS
We plan to increase the involvement of industry in the choice and guidance of some of the projects. Effort
will also be made to increase the multidisciplinary contents of the design projects. The project on electric vehicle exposed the students to many useful and practical knowledge in mechanical engineering. A companion paper involving other areas such as power electronics and control is in progress. [8] VIII.
CONCLUSION
The Senior Design course was first offered in the fall of 1992. Not only does this course meet ABET’s requirements, it exposes the would-be-engineer to real life problems in the profession, encompassing theory, design, computer simulations, construction of a prototype and experimental verification. Optimization and alternative designs are also investigated, while taking into account general engineering principles of safety, quality, economics and ethics in the project evaluation. The overall effect has been to improve professionalism and problem solving skills and increase self esteem of students, and thereby, their productivity. It has heightened interest and awareness of the electric power program, increased both the number of students graduating in the electrical power program and the retention ratio.
ACKNOWLEDGMENTS We would like to thank the Director of ECSEL, Howard, for financial support in incorporating more design contents in our curriculum. We would also like to thank students Dominic L. Williams, Johnestal L. Norvell, Andrea Oates, Hewis Johnson and others who have participated in this program. Finally, our appreciation goes to research fellows and graduate students at the center for the many times they have taken off their own projects to provide guidance to the students.
REFERENCES [1]
[2] [3]
[4]
197.
R. L McConnell, W. L. Cooley, and N. T. Middleton, Electrical Engineering Design Compendium, Addison-Wesley Pub.Co, 1993. R. J. Baum, “Ethics and Engineering Curricula” the Hastings Center, 1980 G.N. Vanderplaats, “Teaching Design Through Computation”, IEEE Transactions on Education, Vol 36, No 1, Feb 1993, pp. 110 -114. S.R.H. Hoole, “Engineering Education, Design, and Senior Projects”, IEEE Transactions on Education, Vol 34, No 2, May 1991, pp. 193
[5]
A.A. Fouad and V. Vittal, “Power System Transient Stability Analysis using Transient Energy Function Method”, Prentice Hall, 1992 [6] “Howard University Transient Stability Program, User’s Manual, Version 2.0”, Howard University, 1990 [7] H.E. Jordan, “Energy Efficient Motors: Selection and Applications”, Van Nostrand Reinhold Co., New York, NY, 1983 [8] J.A. Momoh , “Electrical Engineering Department Design Manual Handbook”, Howard University, May 1995
