Abstract-- Novel interinstitutional activities in power electronics education and specialists training are proposed. Some valuable results concerning methods, research, and experimental work carried out by Tallinn University of Technology and St. Petersburg Electrotechnical University are presented. The paper is focused on the inter-disciplinary curriculum, the virtual e-learning electronic laboratory, the versatile approach to the course and diploma design, and the first experience in team design organization. An open access to the developed educational resources is provided via the Internet. Index Terms-- interinstitutional activity, interdisciplinary curriculum, virtual e-learning electronic laboratory, power electronics.

I. INTRODUCTION In power electronics most beneficial technological

innovations have been introduced into processes and energy distribution. In numerous industrial and vehicular applications, the assemblies of mechanically and electrically coupled devices are joined in electronic units of high complexity. Such systems provide control, management, and monitoring that cover a broad range of tasks. This is the reason of increased attention shown towards specialists teaching and professional training in the area, mainly in the most recent developments in component technologies, converter topologies, system decoupling, and dynamic performance with invariance to disturbances and robustness against the parameter variation.

St. Petersburg Electrotechnical University (ETU), Russia, and Tallinn University of Technology (TUT), Estonia, have built an effective tandem, the mission of which is to find a solution to some primary educational problems in this sphere. In the joint project, TUT as a host institution has provided its classes and laboratories for the experiment, whereas a visiting professor from ETU has delivered lectures, exercises, tests, and examinations in accordance with the program agreed.

The spectrum of the key directions of power electronics studies is determined by the curricula that bear sufficient similarities in the universities of both countries, Russia and Estonia, covering four traditional levels. To obtain the first Bachelor’s degree (BSc), knowledge of basic electronics must be acquired. This BSc study is oriented on the common understanding of today’s engineering in the “physical sense”. A higher

This work was supported by Estonian Foundation for Lifelong Learning Development INNOVE (Project IN7061).

Master’s degree (MSc) is awarded after deeper study, commonly involving some course oriented toward design and research in power electronics applications with prospective work on a doctoral thesis or a graduation project. Close attention in this study is paid to understanding the performance of components and subsystems, mathematical simulation, and laboratory experiments. Next, PhD training is oriented on in-depth research in new directions of science. Post-graduate courses (PG) are aimed toward knowledge improvement in the field. To assemble the disciplines most relevant to power electronics education, a list of interinstitutional activities has been proposed. Focus is on:

• development of methods in the field; • course design and sufficient curricular

arrangement; • experimental teaching and learning involving the

analysis and updating procedures.

II. THEORY AND SIMULATION IN TEACHING POWER ELECTRONICS

TABLE I THE AREAS OF THE INTERINSTITUTIONAL COLLABORATION

Simulation toolboxes Level Discipline ETU TUT

Fundamentals of Electrical Engineering MatLab MathCAD

Microprocessors MultiSim Control Theory LabView MatLab Information Technologies C++ C++

Electrical Machines and Motor Drives eDrive MatLab

Fundamentals of Electronics

BSc

Fundamentals of Power Electronics Power Electronic Converters of Motor Drives

Area of collaboration

Control Automatic LabView System Modeling and Simulation Simulink

Adjustable Motor Drives eDrive Simulink

MSc

Electronic Controllers Omron toolbox

Simatec toolbox

PhD Research and development in the field

PG Knowledge Improvement Area of collaboration

Interinstitutional Activity in Professional Training in Power Electronics

V. Vodovozov, D. Vinnikov, J. Laugis, and T. Lehtla Tallinn University of Technology, Department of Electrical Drives and Power Electronics

Ehitajate tee 5, 19086 Tallinn, Estonia

SPEEDAM 2008International Symposium on Power Electronics,Electrical Drives, Automation and Motion

492978-1-4244-1664-6/08/$25.00 ©2008 IEEE

The list of topics hereunder holds the headlines of the typical environment of the power electronics disciplines, proposed as the result of the joint curriculum [1]. The areas of the institutional collaboration are particularly picked out in Table 1.

III. PRACTICE IN MULTISIM Simulation in Multisim enables a clear analysis of all

electronic circuits, simple parameters variation in a broad range, and favorable possibilities in result evaluation with virtual measurements. Computer simulators provide reading of results, their processing, and comparison. Multisim libraries are well suited for electronics needs, providing different complexity levels of passive components, amplifiers, and switches, from ideal to precision dynamic models. Its built-in tools enable data processing, magnetic design, frequency analysis, and what is really important, interfacing with other simulation instruments, such as Spice, Simulink, and LabView.

The first section of the developed virtual e-learning laboratory is meant for the course “Fundamentals of Electronics” in the BSc study. Practice includes a set of exercises in electronics, the tasks of which is to introduce electronic circuits research and calculation, selection of electronic components, virtual schematic building, virtual voltage and current measurements and waveform analysis, results explanation, and documentation.

For circuit assembling, the learners use the models of dc and ac voltage sources, a current-controlled voltage source, resistors and potentiometers, capacitors and inductors, diodes, transistors, 3-terminal opamps, comparators, oscilloscopes, function generators, Bode plotters, and multimeters. The list of experiments developed for the course includes:

• linear circuits (RL, RC, RLC, series, and parallel resonant circuits);

• passive filters (RC and LC LPF and HPF, band-pass, and band-stop filters);

• diode circuits (plotting the output diagrams of single diodes, series and parallel clippers, limiters, and different Zener circuits);

• amplifiers (plotting input and output characteristics of CE, CB, and CC amplifiers);

• opamps (non-inverting and inverting voltage amplifiers, detectors built on comparators, and Schmitt trigger);

• math converters (summer, subtracter, integrator, differentiator, and PID-regulator);

• oscillators (astable multivibrators and Wien bridge oscillators with unipolar and balanced supply).

At the end of each exercise, students compare the calculated data and the outputs of virtual experiments and generate a report with an experimental circuit diagram, resulting and comparative data tables, voltage and current traces, dependency diagrams, and conclusions with explanations.

The second section of the developed e-learning library is oriented to the course “Power Electronics” of the BSc study. Practice involves a set of experiments in power electronics, the tasks of which cover the development of

power electronics circuits, calculation and selection of power electronic components, topological schematic design and circuit diagrams building, efficiency evaluation and measuring with waveform analysis, explanation, and documentation of the obtained results.

They are arranged on the models of dc and ac voltage and current sources; voltage-controlled, current-controlled, pulse and clock sources; resistors, potentiometers, capacitors, inductors; different switches; diodes, full-wave bridge rectifiers, silicon-controlled rectifiers; BJTs and 3-terminal enhancement n-MOSFETs; opamps; virtual measuring devices; buck, boost and buck-boost converters; oscilloscopes and function generators. The list of experiments developed for the course includes:

• single-phase half-wave rectifiers (M1-rectifier with resistive and inductive loads and LC filters built on a diode and a thyristor);

• single-phase full-wave rectifiers (mid-point M2-rectifiers and bridge B2-rectifiers with resistive and inductive loads and LC filters built on diodes and thyristors);

• three-phase rectifiers (mid-point M3-rectifiers and bridge B6-rectifiers built on diodes and thyristors);

• ac converters (single-phase voltage regulator and bridge inverter, voltage source and current source inverters as well as the different frequency converters);

• choppers (step-down choppers, closed-loop buck converter, step-up choppers, closed-loop boost converter, step-down and step-up choppers, closed-loop buck-boost converters, and Cuk regulators).

As a result, students compare the calculated and experimental data and prepare reports with experimental circuit diagrams, resulting and comparative data tables, voltage and current traces, dependency diagrams, and conclusions with explanations.

The scope of experimental works seems more comprehensive, complex, and different from that described in literature [5][6][7]. It takes advantage of covering the whole spectrum of problems in power electronics studied in electrical engineering and electronics departments of technical universities [8]. Moreover, the listed works distributed between the disciplines are united by the common idea and a uniform methodical approach.

IV. RESEARCH AND DESIGN WITH eDRIVE

The integrated toolbox eDrive has been chosen as the educational design core of the industrial units with electronic components. The package contains instruments for the development and investigation of electric drives with electronic converters. Thanks to its strong orientation to the driving applications, this software offers some advantages to power users and students over other programs.

For equipment computation, the leading companies have developed their specific technologies. Examples are the guides and software of “Siemens”, “Omron”, “Sew Eurodrive”, “Maxon Motors”, “Mitsubishi”, etc. In these packages, the automatic checking of the preliminary worked-out databases accomplishes the search of the

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decision. With the help of the corporative databases, some combinations of parameters may be chosen and optimized from a particular criteria point of view. A scope of allowable environment condition is displayed in a certain data area. System tuning is executed in accordance with the corporative methods also.

Such an approach is conventional for the majority of firms that carry out project designs and have rich experience in the acceptance of the decisions on the basis of extensive computer databases, coming up to numerous catalogue archives and “absorbing” their contents and structures. However, the main drawback is the technological restriction and limitation of data that deprive a designer of an optimum way in the project. It is especially important in the first design stage, when the most responsible decisions are taken.

In distinct from the companies, which promote and propagate their products, the eDrive approach is addressed to the full equipment selection, tuning, and optimization independently on the firm interests. The program eDrive is available for:

• simulation of power electronics systems and components of driving industrial applications;

• selection of converters, motors, and gears in the process of system design;

• analysis of steady-state and transient modes of applications with open-end and closed-loop control systems supplied from the mains and power converters;

• research of options, disturbances, and input signals impact on the system performance;

• system tuning; • generation of reports about the system

arrangement and operation. The eDrive software is a real example of the object-

oriented technology implementation [9][10]. It supports the uniform and versatile approach to the objects of different nature: mechanical, electrical, and informational, undoubtedly required by a power electronic system. Its generalized objects description gives an effective tool for the model base classes design, which applies an inheritance of new modules without any deconstruction of the main model structure. The developed class library comes up to ANSI standards and contains the components, fully described in the scientific and educational literature [11] as well as in the toolbox documentation. The software demonstrates a clear and user-friendly performance for those who have decided to learn about the applications with electronic converters and get an experience in project development in a cost- and time-effective manner.

The package includes numerous simulation tools: • a set of adjustable controller schemes; • models of industrial converters, gears, and

regulators; • the equipment databases of the world leading

companies; • the graphic package for representation of steady-

state and dynamic simulated processes with automatic and manual scaling, system analyzer, and preview facilities;

• the signal generator for supplying the test reference and loading signals as well as non-linear curves, noses, and filters imitation;

• the report generator with powerful graphic multi-format support.

A classification of the supplies processed by the software and stored in eDrive database is given in Fig. 1. A generalized discrete converter description is proposed on the basis of the power converter models of different types. Transistor and thyristor converters of different kinds are considered as the particular cases and the inheritors of the selected model. Such approach helps to develop a system in accordance with the technique renovations. Besides the data sheets, a user may work with queries written in the standard SQL language, which serves as another source of the model information.

POWER

SOURCES

SUPPLY FROM THE MAINS

SUPPLY FROM ELECTRONIC CONVERTERS

Transistorbased converters

Thyristor based converters

ac/dc (rectifiers)

dc/ac (inverters)

ac/ac (dc link and

matrix converters)

dc/dc (choppers)

ac/ac (cycloconverters)

ac/dc (rectifiers)

Fig. 1. Classes of supplies processed by eDrive

In the design process, a learner generates numerous test signals destined to:

• enter various references and disturbances to the simulated applications;

• examine the influence of distortions and disturbances upon the behavior of the components;

• select filters and correcting circuits for designed systems, which improve their performance.

For the last purpose eDrive includes: • the group Signal that represents numerous sources

of references and disturbances; • the group Distorsion that brings distortions of any

kind to the transmission path of a signal selected in previous group;

• the group Filter/Corrector that simulates a digital conversion of a signal selected in a previous group in accordance with the proposed transfer function;

• the chart of output signals of all mentioned groups.

Moreover, a designer may utilize the simulation result

as a new signal. The program receives an output trace for

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its further processing and analysis. All these units are available as variants of a common transfer function, which simulates the same amplifiers, filters, and circuits that were studied earlier with Multisim. Such interconnection of the toolboxes is a significant advantage of the described approach. Another benefit presents the most complete and comprehensive drive educational range of topics as compared with earlier published results, particularly [12].

V. PERSONAL AND TEAM DESIGN Conclusions are one the most important parts of a

paper. Please give careful consideration to this section. As with any engineering discipline, power electronics is based on the integration of multiple fields of knowledge. Insofar as a certain number of systems with the components of different nature are merged, a conflict between technological complexity, cost, and simplicity of maintenance naturally occurs. The corresponding educational aim is to teach specialists working at the intersection of electronics, mechanics, and control. Course works and diploma projects are the suitable tools for this kind of training.

One of the typical course projects is devoted to the design of a control system for a robot (Fig. 2). A team of four students from different departments is assigned the project. The work includes two stages: the stage of individual creativity and that of collective work, particularly via the Internet.

Carriage mechanism (motor, coupling, gear, wheels)

Arm mechanisms (motor, drum, rope, polyspast, arm)

Lever mechanisms (lever, gear, motor)

Capture mechanisms (motor, coupling, gear, bearings, capture, pneumatic cylinder)

Fig. 2. Schematic plan of the transportation robot.

In the first part, each student designs a drive of one of the mechanisms: the carriage, the arm, the lever, or the capture. For the forces, torques, and power calculation, the data of the inner mechanisms are required, thus co-operation is needed to obtain a successful result. In the second part, the intercommunications of the robot sub-systems are organized. Programming of motion, efficiency, and economic evaluation depends on the joint efforts and personal solutions. The same concerns the overall estimation and grading of the project.

VI. CONCLUSIONS The joint curriculum developed by TUT and ETU was

successfully tested as a complete experimental and methodical work. It covers a comprehensive power electronics range of educational topics. An expert from ETU has taught lectures and exercises in TUT during four terms. Presently, all the courses are supported by the electronic e-learning materials written in English with free access to viewing and downloading via

http://www.edrive.narod.ru. From the same site, links are supplied to the databases of the leading world electronic and drive companies. The first printed materials appeared in the University libraries in 2006 .

REFERENCES [1] Laugis, J.; Lehtla T.: Comparison of university level study

methods and laboratory equipment for teaching of electrical drives. 11th European Conference on Power Electronics and Applications EPE 2005, p. 331, Dresden, Germany, 2005.

[2] Drofenik, U.; Kolar, J. W.: Survey of modern approaches of education in power electronics. Annual IEEE Applied Power Electronics Conference and Exposition APEC 2002, pp. 749-755, Dallas, USA, 2005.

[3] Huselstein, J.-J.; Enrici, P.; Martire, T.: Interactive Simulations of Power Electronics Converters. 11th Int. Power Electronics and Motion Control Conference EPE-PEMC 2006, pp. 1721-1726, Portoroz, Slovenia, 2006.

[4] Vodovozov, V. M.: The Educational Resources of Mechatronics. Mechatronics, vol. 5, no. 1, pp. 15-24, 1995.

[5] Bencic, Z.; Sunde, V.; Jakopovis, Z.: Virtual laboratory for power electronics. 10th European Conference on Power Electronics and Applications EPE 2003, p. 723, Toulouse, France, 2003.

[6] Cheng, K. W. E.; Chan, C. L.; Cheung, N. C.; Sutanto, D.: Virtual laboratory development for teaching power electronics. 10th Int. Power Electronics and Motion Control Conference 2004, p. 325, Riga, Latvia, 2004.

[7] Widlok, H.; Widlok, M.: Computer-Aided Teaching of Power Electronics. 11th Int. Power Electronics and Motion Control Conference 2006, pp. 1733-1736, Portoroz, Slovenia, 2006.

[8] Bauer, P.; Kolar, J.: Teaching power electronics in 21st century. 9th European Conference on Power Electronics and Applications EPE 2001, p. 00325, Graz, Austria, 2001.

[9] Vodovozov, V.; Tsvetikov, E. A.; Vodovozova, E.V.: Object-Oriented Models of Electromechanical Systems. 8th European Simulation Symposium “Simulation in Industry”, Short Papers, Genoa, Italy. 1996.

[10] Vodovozov, V.; Loparev A.: Simulation Tools for Design and Testing of Electric Drives. 10th Int. Power Electronics and Motion Control Conference 2004, DS 7-16, Riga, Latvia, 2004.

[11] Usher, J. M.: A tutorial and review of object-oriented design of manufacturing software systems. Computers and Industrial Engineering, vol. 30, no. 4, 1996, pp. 781-798.

[12] Fedak, V.; Repiscak, M.; Zboray, L.: Design and Implementation of e-learning tool for courses on electrical drives. Int. Conference on Electrical Drives and Power Electronics EDPE 2005, E 05-115, Dubrovnik, Croatia, 2005.

[13] Williams, J. M.; Cale, J. L.; Benavides, N. D.; Wooldridge, J. D.; Koenig, A. C.; Tichenor, J. L.; Pekarek, J. D.: Versatile hardware and software tools for educating students in power electronics. IEEE Transactions on Education, vol. 47, no. 4, 2004, pp. 436-445.

[14] Vodovozov, V.; Jansikene, R.: Power Electronic Converters. TUT: Tallinn, 2006, 120 p.

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