IEEE Transactions on Power Systems, Vol. 1 1 , No. 3, August 1996 1131

ENHANCING POWER ENGINEERING EDUCATION THROUGH THE USE OF DESIGN MODULES

L. Goel T.T. Lie A.I. Maswood G.B. Shrestha School of Electrical and Electronic Engineering

Nanyang Technological University Singapore 639798

Abstract:This paper describes the main features of four design modules that form part of the curriculum for the final year power engineering students at the Nanyang Technological University, Singapore. Through the use of these modules, the students gain an insight into the various aspects of power engineering - including power electronics and dnves - and this will hopefully help them in a better understanding of the practical aspects of power engineering, and therefore make them better engineers in the power industry. The four modules described are Generating Capacity Expansion Planning, Rectifier and DC Motor Control, Power Systems Operations Planning, and Security Enhancement using Optimal Power Flow.

Keywords: power system design, power engineering education, undergraduate curriculum, power system planning.

I. INTRODUCTION

One very important factor in developing or maintaining a successful power engineering program is to ensure a satisfactory level of high level undergraduate students [l]. At the Nanyang Technological University's School of Electrical and Electronic Engineering (EEE), power engineering has been gaining popularity since 1991 - this is evident from the fact that the power student population has risen steadily from I1 (less than 2% of the electrical engineering student population) in 1990/91 to 73 (more than 11%) in 1995/96. This is attributable in part to the basic emphasis on power projectddesign modules introduced in the second and third year of common electrical engineering - these modules have helped the students gain a better appreciation of power engineering, so much so that many of them now opt for power engineering in their final year of study. The basic power engineering curriculum at the School of EEE was highlighted in another paper [2], and will therefore not be repeated here. Reference 2, however, did not elaborate on the design modules offered to power option students. It is the basic objective of this paper to describe and illustrate the four design modules currently offered to the power option students in their final year-

Module 1 - generating capacity expansion planning Module 2 - rectifier and DC motor control Module 3 - power systems operations planning, and Module 4 - security enhancement using optimal power flow.

96 WM 054-7 PWRS A paper recommended and approved by the IEEE Power Engineering Education Committee of the IEEE Power Engineering Society for presentation at the 1996 IEEWPES Winter Meeting, January 21- 25, 1996, Baltimore, MD. Manuscript submitted June 20, 1995; made available for printing January 2, 1996.

Modules 1 and 2 are covered in Semester 1 - module 1 runs for the first six weeks (3 hours per week session) whereas module 2 runs for the last seven weeks (one semester has 13 teaching weeks excluding a 1-week break). Modules 3 and 4 are covered in Semester 2, with module 3 running for the first 6 weeks and module 4 for the last 7 weeks. One 3-hour session usually includes a 1-hour lecture on the basic fundamentals associated with the module, and 2 hours hands-on exercise on the PCs as per the design requirements. The students are expected to submit a detailed report on any one of the two modules in each semester, and must also appear in a written examination at the end of each semester - the exam question paper does not have any choice though, i.e., students are expected to prepare for both modules hut must answer the only question that appears

The scope and intensity of course requirements at Nanyang Technological University's School of EEE are described in some detail in Reference 2. The background courses that the students undertake in their sophomore and junior years include basic power system elements such as transformers, machines, operation of power systems, system protection, principles of power elctronics, etc. Power engineering students must complete two core courses in each of the two semesters, other than one elective and one design course. The core courses in the final year of power engineering cover a vast variety of topics such as power system digital protection, high voltage engineering, basic reliability engineering, power system operation and control, load forecasting and scheduling, load flow studies, dynamics and stability studies, electricity utilization systems, building services engineering, standby supplies, I load management, SCADA systems, power electronics and drives, etc. Since the students have sufficient background in power systems and power electronics and drives, the design modules they undertake are not too advanced for them. It should be appreciated, however, that some design modules may run in parallel with certain applicable topics (knowledge of which is necessary for a better understanding of the design module/s) whch are covered in greater depth in final year only. This difficulty is completely overcome by the fact that each design module runs for 6 or 7 weeks, and therefore the instructor can cover the background material to a reasonable depth, if necessary.

While the above-mentioned four modules have been offered for the last few years, there are other modules which may be introduced any year depending on the lecturers' interests and availabilities, etc. Some other design modules that were covered in the past include the following:

transmission system planning, distribution system planning, power system protection schemes, building services, inverters and resonant converter design, etc.

The basic objective of the design modules is to complement classroom teaching of theory concepts with hands-on design exercises through the use of simulation software - the s o h a r e tools required are generally developed by individual instructors to - .

0885-8950/96/$05.00 0 1996 IEEE

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suit their requirements, but in many cases also include acquired software such as PSpice and ESANET, etc. The detailed descriptions together with necessary illustrations of the four modules are provided in the next few sections. It is expected that these design modules will further the students' understanding of fundamantals in power system engineering, analysis and utilization, and in power electronics and drives. Based on the feedback from the past few batches of power engineering students who graduated from the Institute, it is heartening to note that the practical desigdproject-oriented curriculum has enabled them to apply the concepts learnt to their own work

II. MODULE 1 : GENERATING CAPACITY EXPANSION P L A N " G

The basic objective of this module is to familiarize the students with some aspects of generating capacity reliability evaluation. The emphasis is on reliability inhces' [3] based capacity analysis. The tools presently used by the students are provided by the instructor, who has developed significant amount of software over the years especially in the field of reliability evaluation of power systems. It is, however, possible to acquire commercially- available software such as WASP, EGEAS, etc. for this module. The objective of generation planning is to provide generatmg units for the future so that investment and operating costs are minimized while satisfying the load with specified quality and reliability and under the operating, environmental and financial constraints encountered.

Adequacy assessment of generation systems is concerned with the ability of the generation facilities to satisfy the system load requirements - the reliability of the transmission system and the ability to transport the generated energy to the consumer load points is not considered. In its simplest form, generating capacity reliability evaluation involves the creation of capacity models (in the form of capacity outage probability table, COPT [3]) and load models, and then convolving them together to obtain the system risk indices, such as the loss of load expectation (LOLE, d/yr or Wyr) and loss of energy expectation (LOEE, W y r , also known as the unserved energy or expected energy not supplied, EENS). The students are expected to conduct long term capacity eqansion studies using both these indices. In addition, energy production costs and present worth of generating unit additions are also required to be evaluated and used in making judicious additional capacity decisions. The determination of unit additions in the future is based on an acceptable level of risk (LOLE and/or LOEE) and on the rate of load growth expected for the planning horizon. The planning procedure for the expansion of generating capacity by adding new units, based on the criterion that a certain risk level should not be exceeded, is selected largely by economic considerations. This involves assessing the present values of future investments which in turn depend on interest rates, the life span of generators, etc [4].

The s o h a r e packages provided to the students can develop the COPT utilizing 2-state or multi-state representation of generating units, and calculate the LOLE and LOEE for a given load model, i.e. daily peak load variation curve (DPLVC) or load duration curve (LDC). The indices can also be calculated by including the 7-step load forecast uncertainty [3] assuming a normally- distributed probability function. In addition, the expected energy output of each unit, together with the unit operating cost can be obtained using the software. Finally, all the above can be done for a period of 20 to 30 years simulation period, in conjunction with the present worth of unit additions. Different types and sizes

of generators (including gas turbines) can be considered for capacity expansion analyses, with the basic objective of comparing alternative expansion plans in terms of power generation costs (PGC) and present worth (PW) [4]. The basic expressions utilized in the design are given below. It must be emphasized that the tools utilized in this design module are based on analytical methods [3], and not on Monte Carlo simulation techmques .

AI

LOLE = C p k f k k= 1 AI

LOEE = C p k E k k=l

M

PGC = C (EES, OC, + FC, )

where:

pk= individual probability of capacity outage o k

tk= number of time units that an outage ok results in a load loss

N= number of capacity outage states in the COPT

Ek= energy curtailed by capacity outage o k

EES'= expected energy supplied by unit j

OC= operating cost ($/MWh) of unit j

FC= fixed costs of unit j, and

M= number of units in the system.

J

J

1

The capacity expansion analyses using LOLE/LOEE is conducted as follows:

1 . The projected load growth is provided in advance. This is the predicted percentage increase in load year after year, with the basic load curve maintaining the same shape. For example, the students are asked to assume that the load growth is 5% per annum.

2. The type and size of additional units, together with reliability data, forced outage rate (FOR), fuel cost, fixed cost, capital cost, etc. are provided at the outset.

3. The acceptable risk e.g. LOLE of 0.1 d/yr or LOEE of 1200 W y r for the entire expansion period must be specified.

4. The students must perform various analyses and determine the years in which new unit(s) must be committed in order that system risk remains below or equal to the pre-specified level. The expansion plans are to be compared in terms of expected power generation costs (PGC) and present worth. The type, size and loading order of unit(s) are governed by economic considerations. In actual operation, the operator must decide which units to commit. For planning purposes, however, we have assumed the units to be committed in order of increasing operating costs, both at present and in adding future capacity.

5 . The above analysis can be conducted for about 20 to 30 years. It, however, assumes that the load is known with certainty, which is highly unlikely in actual practice. Thus future load modeling

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specifications, the students are expected to do the necessary calculations for the design parameters. These include the thysistor switch ratings (peak, rms, average current and the peak inverse voltage), rectifier delay angles to provide variable dc voltages, commutation voltage drops, the rectifier inpuVoutput filters, and the rectifier gating circuitq. Once the parameter calculations are finished and sketches of associated waveforms drawn, the students verify their calculations using the software package ‘ORCAD-PSPICE’ [7,8]. Using the ‘PEL’ (Power Electronics Library) interface, a schematic entry of the entire rectifier and DC motor model is possible as shown in Fig. 1. This enables the students to test the performance of the rectifiedmotor structure without hanng to actually build the circuit. Thyristor switch ratings can easily be obtained and checked with the calculated values. Dynamic inpuffoutput currents and voltages are monitored and designed filters are realized to keep the THD within acceptable level. The DC motor speed is controlled by varying its armature voltage while the gating signal generator is realized using function generators and comparators. This is shown in Fig.1 (A). The ‘reference signal’ level in Fig. 1 (A) will control the delay angle and hence the motor armature voltage. The armature voltage and the motor speed can be controlled from the maximum rated value to practically zero by changing the reference voltage only. In order to have a true dynamic system, a SPICE model of the motor armature circuit is built based on the suggestions of Reference 9, as shown in Fig.l(C). The dynamic model of the dc motor is not only capable of providing the variable speeds at variable armature voltages, but also shows its dynamic response under variable load torque. Additionally the motor armature and the field current waveforms can also be plotted. This enables the students to have an in-depth investigating capability. Fig. 2 shows the current and the peak inverse voltage across one of the thyristor switches From the waveform the peak, average and the rms values can easily be evaluated and checked. Fig. 3 shows the rectifier output voltage and the motor armature voltage (after filtering). It is evident that the necessary filtering makes the waveform smoother so as to meet the required THD criteria.

must incorporate the uncertainty associated with the predicted load growth. The load forecast uncertainty is described by a normal probability distribution [3] and utilized in the analyses in order to obtain more realistic results.

6. The maxlmum demand o f the test system is given on an arbitrary basis for the next 20 to 30 years, i.e. no fixed load growth is assumed, and the LDC is described by a high order polynomial, e.g.

Load(t) = A, + A,t + At2 + A3t3 + A4t4 +A5?, where t is the time of the year in per unit (0.0 to 1 .O).

The coefficients of the LDC (4 through As) are provided to the students for various projected years, e g. 1996-2005 and 2006- 2015, etc. and they are required to repeat the above capacity expansion studies for this load pattern and suggest suitable expansion plans for the given expansion period.

This module uses the IEEE Reliability Test System (RTS) [5] as the test system for the students to submit the design report. Alternatively, the Roy Billinton Test System (RBTS) [6] is used in some academic years The module enables the students to recognize the inherent uncertainties in generation, load> etc. and helps them identify the consequences of various types and sizes of unit additions on PGC, reliability indices and present worth.

111. MODULE 2: RECTIFIER AND DC MOTER CONTROL

In this module, each group of 2 students has to accomplish the design for a complete 3-phase thyristor bridge rectifier including its gating circuitry. The motor terminal voltage and the current ratings are given. Additionally, allowable total harmonic distortion (THD) of the motor terminal voltage and that of the rectifier input current are also specified. Given the design

SCR

I - - ....... - ....................................... *

Fig. 1

3-PHQSE R E C T I F I E R

+

SWITCH

- ARMATURE J K D I O D E - V O L T A G E -

w r D y n a m i c M o d e l o f

DC m o t o r A r m a t u r e C i r c u i t

Complete Schematic entry of the Rectifier Motor speed Controller

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I L, n , ( r s w ) * 5 ~ s IOms 15ms 2Ome 25mq 3Cms 35ms 1 me

Figure 2 Thyristor peak inverse voltage (top) and Its instantaneous current (bottom)

1ernperatuic 27 0 Daie/Time run. 05 /29 /95 200v - : t

The load curve data is used to obtain the load duration curve whch is transformed to the Inverted Probability Distribution Function (IPDF) lo by normallzmg the bme axis and then interchangmg the axes PDF adequately represents the probabilishc nature of load, since d d x ) = Prob (load 2 x) The load curve or the PDF is modified to reflect the effects of specific options being studied. After subsequent loading of generatmg w t s , the IPDF LL for the residual load after comt t ing the ith generator of capacity C, and outage and innage rates of q, and pi respectively can be computed usmg

Ai (XI = pi “1-1 (Ci+x) + Si Li-1P)

Each of these PDFs are represented by a fifth order polynomial and used to evaluate the expected values of energy produchon, production cost, fuel requirements and reliability indxes (e g. LOLP, the loss of load robability) etc. For quadratic heat-rate

iteratively as follows for a total operation penod T

1. The expected operatmg hours for unit i are:

filnchon H=a + j3P + yP 3? MBtu/hr, these quantities are computed

E{hi} = T Pi“i-1 (0)

2 The expected energy output of unit i is :

E { r n ) , = TP, 7 “1-1 (XI dx

3 For a fuel cost of R $/MBtu, the expected operatmg cost of umt i is:

E{$}i =RT pi CL Li-1 (O)+RT pi 7 (pi + 2 ri X) Li-1 (x) dx Figure 3 The motor armature voltage after filtering (top) and the

rectifier output voltage (bottom) 0

IV. MODULE 3: P O W R SYSTEM OPERATIONS PLANNING

In addition to satmfyng the operahonal and regulatory criteria, one common objective in power system operahons is to m i m e the cost This objective is achieved by formulating proper operating policies and practices to suit the load and the generation charactenstics of the system In this module the students are exposed to some of the practical studies conducted to assess important operating issuea The specific assignments may Lover w d e range of projects which requxes aiialyses/studies consisting of some combination of (a) load forecashng, (b) maintenance scheduling, (c) unit commitment, (d) economc dispatch (e) fuel management, (Q generation coordination, (g) interconnection transachons evaluation, and (h) load managementlsheddmg

A background system is given for which the histoncal data are provided in the most basic form, as available in practice These consist of the chronological load data, histoncal peak load data and the system umt characteristics such as the outage rates, maintenance history, heat rates and cost charactenstics The students are expected to utilize these basic data and apply their knowledge gamed from power engineering and other courses to complete the assignment MATLAB is the recommended tool to process the data and they are encouraged to use its statistical functions (e g , regression, curve fitting etc 1 and optmizabon packages (e g , Linear Programming) as requu-ed

Probabilistic Production Costmg is introduced in some detal as a general tool for operations planning [10,11] The general framework of production simulation is shown in Figure 4 where some of the specific aspects of the simulation are also indicated

4 For a heat value of V MBtUitonne, the expected quantity of fuel (qf, required by unit i is:

E {Sf)i = [1/(RV)I E {$)1

5 After all the units are simulated

* The LOLP of the system is given by ln(O) * The expected unserved energy (ENS) is given by ’

e{ENS} = T 4 An (x) dx 0

0 The total operating cost is obtained as the sum of all individual operatmg costs

The mportant feature of th~s methodology is that it takes into account the stochastic nature of both the load as well as the generatmg units, and a general heat rate or cost function can be mcorporated The computed quankties are the expected values which are very proper for planning applications In detaled designs, a more detailed production costing package PRODCOST is provided to the students This package can mcorporate many addltional features such as economic hspatch, and conduct studies spannmg number of years considenng load growth rates and interest and inflation rates, etc

The recent design module included

* 0

e

preparahon of daily operahons schedulmg, evaluation of direct load control plans, and developing optimal fuel management schemes

Operations Scheduling: This study allows the students to perfonn operations scheduling using the load and the system capacity data. The specific tasks include the load forecasting, maintenance scheduling, prioritizing the generator units, unit commitment, and spinning reserve allocation. Both deterministic approach as well as a probabilistic procedure are studied to bring out the essential difference between these methods and also to bring out the inter-relationships between the level of reliability (LOLP) and the corresponding production cost.

Direct Load Control : This sub-module formulates an optimal demand side management (DSM) scheme and involves the evaluation of the production costs corresponding to different control schemes. The students are expected to understand the subtlelities of the problem such as (i) the dependence of energy cost on system load level, (ii) energy pay back, (iii) the reduction in the production cost when a fraction of load is shifted from peak to off-peak period, (iv) the savings from and hence the capacity credit for, the reduction in peak load, and (v) other costs associated with such a scheme [12]. They conduct comparative studies of different schemes using appropriate methodologies to estimate the production costs. Probabilistic production costing package (PRODCOST) can be utilized by processing the raw available data to estimate the production cost and the reliability indices.

Fuel Management: This module addresses a simplified problem of fuel scheduling in a power station that considers the fuel rates of the generating units, their economic loading, the storage capacity constraints and costs, fuel delivery schedule etc [l 11. The students learn why linear representation of various processes (e.g., heat rate characteristics : H = A -t BP) are sought and are quite adequate when considering problems of large dimensions. The students formulate the fuel scheduling task in the form of a linear programming problem with the objective of minimizing the overall cost. A standard linear programming package, (e.g , the LP optimization tool box in MATLAB) is used to arialyze the problem and discuss and highlight the important issues in fuel management.

0 Economic Dispatch Maintenance, etc.

I

I I Generation Specific Studies I Power Exchange Characteristics DSM, etc. I I L I

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V. MODULE 4: SECURITY ENHANCEMENT USING OPTIMAL POWERFLOW

This module is designed for the students to understand the basic concepts of power system planning, steady-state security assessment, and economic and security aspects of power system operation. The emphasis is more on the analysis of power system planning and operation through the use of an energy management system (EMS) software package acquired from ESANET, Inc., USA [ 151. The EMS software package consists of

Network Analysis sub-systems which include Network Topology Processor, State EstimatorExternal Estimator, Contingency Analysis, Dispatcher/Optimal Power Flow, Penalty Factors, Security Constrained Dispatch, Voltage/Var Scheduler, Outage Scheduler and Three-phase Short Circuit; Scheduling Application sub-systems which include Unit Commitment, Interchange Evaluation and Production Costing; Database and Man-Machine sub-systems which support the proper execution of Network Analysis and Scheduling Applications sub-systems.

The main objective of using optimal power flow to enhance the security of the system is to ensure that not only the generation cost and operating cost are minimized but also that the system is secure enough from any single contingencies tested In realizmg the objective, the students will acquire some knowledge on power flow analysis, contingency analysis, and optimal power flow.

The scope of work of this design module is divided into three sub-projects, namely

1. Load flow project. 2. Single contingency analysis project 3 . Optimal power flow project.

The detailed descriptions of each sub-project are presented in the following subsections It should be noted that the JEEE 14 bus system [13] is used as the study system for all the above- mentioned projects.

Probabilistic Production Simulation

Quantities

0 Energy, Fuel, etc

l-----7 .+ Cost Evaluation

C I

Reliability Evaluation

A LOLP,

Figure 4. Probabilistic Production Simulation

1136

A. Load Flow Project

In this project, students are expected to learn the technique of load flow analysis for the purpose of utilizing properly all the system resources to meet the demand and identifying whether system upgrading or any compensation is needed The basic load flow problem is usually stated as follows:

C. Optimal Power Flow Project

Optimal power flow is a nonlinear optimization problem with the incidence of equality and inequality constraints. In mathematical terms, the problem of nonlinear constrained optimization involves fmding the values of a set of variables which optimizes the objective function without violating the constraints. This can be expressed as follows:

Given o

0

o At generator voltages Vi ,1=1,2, ,m 0 Slack bus information

Load demands PL,, QL, at buses 1=1,2,. ,n

Specified generation levels PG, at buses i=1,2, ,m

Determine: 0

e

0 Line currents and losses 0

The voltages at the remaining buses and the phase angles for all the buses Real and reactive power flows on all the transmission lines and transformers

Reactive power injections at generator buses

A scenano is designed for the students to simulate the occurrence of deficiencies in generation and transmission capacihes The students are expected to recommend and justify their recommendahon whether generabon rescheduling, system upgrading, or both are necessary in order to maintain acceptable ranges of bus voltages and frequencies Th~s has to be achieved wthout exceeding the rahngs of any of the system components, such as generators, transmssion lines, transformers, etc

B. Single Contingency Analysis Project

In this project, students are expected to screen all the possible single contingencies, compare the pre- and post- contmgency results, and rank the contingencies based on the severities m terms of the thermal overload problems in the transrmssion lines It is very important to know which contingency w l l lead to the worst operating situation. Thus, preventive measures can be taken. The students are also expected to compare thelr screerung results wth the results from the contmgency analysis ranlung technique provided in the software The objective behmd this exercise is to make the students aware of the many available techniques on contingency selection which are able to produce very similar results in a much shorter time The companson is made to ensure that the selection technique used m fms particular software does not misclasify, give a false alarm, or has a poor threshold selechon

By going through the exercises descnbed above, the students are expected to be able to make some predictions on the vulnerability of the system and eventually to make suggestions to the system operator or planner for impronng the security of the network. In other words, the students should spell out not only the preventive measures but also improve the operating security level of the system.

In summary, one can see that this project is designed for the students to understand how the screening tool is used for operations planning such as selection of critical contingencies for a transmission reliability assessment (for deciding whether additional transmission facilities are needed), indication of whether the selected level of generation for each operating unit could cause thermal overloads, maintenance scheduling, etc

m m E e . f(x,u) subject to : g(u,x) = 0

h(u,x) < 0 where,

f(x,u) - the objective funchon g(u,x) - a set of equality constraints h(u,x) - a set of mequality constrants x - state variables, and U - control variables.

The optimization algorithms and solubon methods are briefly explained to the students for them to appreciate the optimal power flow problems. The students are expected to understand how optimal power flow problem departs from the basic load flow problem. There are actually two major departures [14]. One is related to the presence of the criterion for the computation of the control vanables, expressed as the minimization of a cost function The other is related to the explicit inclusion of the inequality constraints which are the operating constraints.

The students are expected to compare the consumed or generated MW or MvAr values for each bus between the basic load flow and optmal load flow. The objective is to understand how a generating unit has been allocated for economic operation based on the generahon cost provided while not vlolating the operatmg condibons. Th~s project is also designed such that the students are able to understand that real power losses in the system can be controlled or varied by different scheduling methods for the reactive power control variables.

Fmally, the students are expected to suggest a method for getting the cost mmmuation end result which guarantees that none of the smgle contingencies tested will result m violations in operatmg limts such as thermal overloads, etc

In summary, this design module is designed for the purpose of improving or enhancing the basic concept of power system plannmg, steady-state security assessment, and economic and security aspects of power systems through hands-on design exercises This is very essenhal in helping the students to appreciate the theoretical backgrounds that they have learnt m the lectures Moreover, the students w l l be well prepared and equipped wth power system engineering knowledge which may help them in pursuing their careers

VI. CONCLUSIONS

The undergraduate power engineering cumculum at the School of EEE, Nanyang Technological University has been designed to provide a good balance between theory and practice. This paper descnbes four practical design-oriented modules that are currently offered to enhance power engineering education through a proper balance between the fundamental concepts and hands-on exercises. The four modules are generating capacity expansion planning (module I), rectifier and DC motor control (module 2), power systems operations planning (module 3), and

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security enhancement using optimal power flow (module 4). Module 1 emphasises on long-term capacity planning under uncertainties in load demand and fuel sources. Module 2 emphasises thynstor circuits for DC motor control through simulation software such as PSpice and Orcad. Module 3 emphasises on actual operations planning involving economic dispatch, unit commitment, maintenence scheduling, etc. to minimise the operating costs. Module 4 pertains to steady-state security assessment using optimal power flow through an energy management soAware ESANET.

It can be easily appreciated that there are no short cuts to increase the student population in power engineering. It is important that relevant topics (e.g., emerging applications of power electronics, and use of simulation software in power systems analysis and cqntrol, etc.) are taught to the undergraduates in a manner that would be most advantageous to them when they join the industry upon graduation. The modules described in this paper are a step forward in this direction - the students are expected to emerge as better engineers to serve the industry needs in modem times. The design-based and project-oriented courses have, in part, contributed to a steady increase in the power engineering student population in the past few years.

W. REFERENCES

[ l ] E. Lakervi, J. Partanen, "An Attractive Curriculum in Power Engineering", IEEE Trans. on Power Systems, Vol. 7, No. 1, Feb. 1992, pp. 346-350.

[2] H.B. Gooi, C.Y. Teo, "A Project-Oriented Power Engineering Curriculum", IEEE Trans. on Power Systems, Vol. 10, No. 1, Feb. 1995, pp. 27-33.

[3] R. Billinton, R.N. Allan, Reliability Assessment of Large Electric Power Systems, Kluwer, Boston, 1988.

[4] R. Billinton, L. Goel, "A Procedure for Estimating the Worth of Generating Unit Refurbishment", Canadian Journal of Electrical and Computer Engineering, Vol. 15, No. 4, Nov. 1990, pp. 140-148.

[SI IEEE Committee Report, "IEEE Reliability Test System", IEEE Trans. PAS, PAS-98, 1979, pp. 2047-2054.

[6] R. Billinton, S. Kumar, L. Goel, et ai, "A Reliability Test System for Educational Purposes - Basic Data", EE,E Trans. PAS, Vol. 4, NO. 3, 1989, pp. 1238-1244.

[7] PSPICE Manual, Microsim Corporation, Irvine, California, USA, July 199 1.

[8] ORCAD manual, "Schematic Design Tools", Orcad Systems Corporation, Oregon, USA, 1989.

[9] Rashid M. H., Spice for Power Electronics and Electric Power, Prentice Hall Inc., 1993.

[lo] X. Wang and J.R. McDonald, Modem Power System Planning, McGraw Hill, 1994.

[ l l ] A.J. Wood and B.F. Wollenberg, Power Generation, Operation and Control, John Wiley, 1984.

I121 H.G. Stoll, Least Cost Electric Utility Planning, John Wiley, 1989.

[13] L. L. Freris and A. M. Sasson, "Investigation on the Load- FlowProblem", Proc. IEE, 1968, 115, (lo), pp. 1459- 1470.

{14J A. Debs, Modem Power Systems Control and Operation, Kluwer Academic Publishers, 1988.

[ 151 ESANET Manuals, Engineering Software Associates Power Systems Inc., P. 0. Box 719, Wayzata, Minnesota, USA, 1993.

Wr. BIOGRAPHIES

L. Goel obtained his B. Tech.degree in Electrical Engineering from Regional Engineering College, Warangal, India in 1983 and M.S. and Ph.D. degrees in Electrical Engineering from the 'University of Saskatchewan, Canada in 1988 and 1991 respectively. His research interests are power system reliability costhenefit assessment of power systems. Since 1991, he is a Lecturer with the School of EEE at the Nanyang Technological University.

T.T. Lie obtained his B.S. in Electrical Engineering from Oklahoma State University, USA in 1986, and M.S. and Ph.D. degrees from Michigan State University, USA in 1988 and 1991 respectively. His research interests are power system stability and control, expert system applications and advanced control techniques' applications to power systems.

A.I. Maswood received his B.Eng. and M.Eng. degrees from Moscow Power Engineering Institute, and Ph.D. from Concordia University, Canada His research interests are in power electronics, particularly converter topologies, advanced PWM switching techniques, harmonic elimination and modeling of circuits,

G.B. Shrestha (IEEE S-88,M-90,SM-92) received B.E.(Honours) degree in Electrical Engineering from Jadavpur University (India) in 1975, MBA from University of Hawaii in 1985, M.S. in Electrical Power Engineering from RPI in 1986, and Ph.D. in Electrical Engineering from Virginia Tech in 1990. His main area of interest is power system operation and planning.

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Discussion

A. Z. Khan (EEE Dept., Sultan Qaboos University, Muscat, Oman): The authors have presented a very useful design oriented educators’ tool for the senior power engineering students. The use of software and design based curriculum in undergraduate teaching is no doubt a very useful tool for enhancing the students interest and understanding capability particularly to the complex problems of power engineering.

One important suggestion that comes to mind is to make the applications of these design modules more demanding by assigning individual students to carryout a certain task rather than giving it to a group of students. T h s experiment that I have been pursuing here in SQU, has helped the students to push themselves more and in the process learn more as well.

The other aspect of software oriented teaching is for the instnictor to provide a comprehensive explanation of how the software was developed i.e. the theoretic steps involved in the algorithm design and its related equations. Is this part of the teaching of the modules ?. I have found that this helps the student understand how coding and theory are related.

One important question related to the object-oriented laboratories is that have the authors developed similar modules for the power system protection, power system stability studies and power distribution studies w h c h are also elective courses in the senior level power curriculum ?. All core and elective courses in the undergraduate power engineering curriculum involve computations and in some schools design projects are normally given to students. The authors idea of developing software-based laboratories in parallel with the teaching will be very interesting to the students if similar exercises are involved in other courses as well. Otherwise the students interested in PCs’ use will tend to register in courses involving education through the m e o f design mcdules o d y zr?d law turnout could result in other courses. Any suggestions ?

L. Goel, T. T. Lie, G. B. Shrestha (Nanyang Technological University, Singapore): The authors would like to thank the discussor for his interest in their paper. It is indeed heartening to note from the discussor’s comments that similar designlpractice-oriented approach is used in senior years of the electrical engineering program at the SQU, Oman. We have the following comments to the discussor’s queries.

With regards to the discussor’s suggestion that individual students should be assigned specific tasks as opposed to giving two or more students to work on the design, the answer lies in the philosophy behind the education objectives. At our Institute, a cooperating learning strategy is applied to promote active learning among the students. This strategy requires students to work in small, fixed groups (usually of 2, or maximum 3 students) on a structured learning task - the group works together for a common goal and each member contributes to the final achievement. Group interaction motivates students to think and it provides opportunities for exchange of ideas. This enables them to maximize their own and each other’s learning as well as provokes higher level reasoning skills, which is one of the most important features of active learning. According to Johnson and Johnson [RI], students’ achievement is generally higher in a cooperative situation than in a competitive or individualistic one. Between groups, of course, variation in the design work is maintained, for instance in Module 3, by assigning the students the operations planning tasks for different periods of the year.

With regards to the discussor’s query on providing a comprehensive explanation of how the software was developed, yes we do provide the relevant theoretical background, algorithms, equations, etc. (including illustrative examples) in great detail during the “lecture” part of each 3- hour design class. We certainly agree with Professor Khan that this helps the student to appreciate coding vis-a-vis theoretical concepts.

Finally, as stated in the paper, other modules, e.g., power system protection schemes, distribution system planning, building services, etc., have been run as design modules in the past and may be run again depending on the demand in Singapore, the availability of resources, etc. It can be easily appreciated that all aspects of power engineering cannot be covered through the use of design modules in the senior years of the course, hence we believe that four modules is just +out the maximum that can be accommodated in the final year of the power engineering curriculum.

References

[RI] Johnson, D. W. and Johnson, Learning and Achievement”, In Cooperative Learning; Theory York, Praeger, 1990, pp 23-27.

Manuscript received April 1, 1996.

R. T., “Cooperative Sharan, Shlomo (Ed) and Research, New