Janos Hamar

Multimedia based e-learning tools for dynamic modeling of DC-DC converters

Exploiting the recent achievements of the information and communication technologies, a new e-learning initiation entitled Yoto project was launched in 2004. On longer run its most important objective is to build up and maintain an electrical engineering knowledge base, on shorter run it helps giving more and more publicity to some relevant fields, especially power electronics, drives and motion control. The multimedia rich content can be utilized in the high level academic education, in the industrial vocational trainings and also in supporting the circuit and system design specialists by fast interactive tools. This paper presents a new e-module attached to the Yoto project about the dynamic operation and modeling of dc-dc converters.

New e-learning tools for DC-DC converters

The paper gives an overview of the Yoto project, a novel e-learning initiative to build up an electrical engineering knowledge base. It also presents a new e-module of the project relating to the steady-state operation of DC-DC converters. The multimedia rich module contains numerous interactive tools promoting the high level education in the academy sector and the vocational trainings in the industry. The interactive tools also highly support the circuit design process by enabling fast calculation and access to relevant circuit quantities and waveforms (voltages and currents) in steady-state without long simulations

Investigating stability of power configuration including virtual negative inductance

Since power circuits are significantly influenced by inductances, a variable active-passive reactance (VAPAR) has previously been introduced in order to generate a virtual negative inductance, which has found applications in the rapid power flow control of power systems. It is used to cancel an existing undesired inductance, since the power flow through a simple power system of two voltage buses connected by an inductive power line is essentially restricted by the line inductance. These studies also indicated that the stability of the system could be compromised by the presence of stray capacitances. The present paper aims to offer a more accurate stability assessment of this RLC configuration, estimated so far by linear approximation, by essentially ignoring the switching process within VAPAR. The normal periodic steady-state regime leads to a fixed point in the stroboscopic map used to model the variable-structure piecewise-linear nonlinear system. The stability is indicated by the eigenvalues of the Jacobian matrix of the stroboscopic map, evaluated at this fixed point. The analysis reveals bifurcation behaviour and allows accurate and convenient prediction of the stability boundary in the parameter space of the virtual negative inductance required by the application and the stray capacitance present in the power circuit.

Multimedia course for power electronics, nonlinear dynamics and motion control

In Power Electronics, in Nonlinear Dynamics and in Motion Control the real advantages of the multimedia elearning approach can well be utilized. Explaining the sophisticated processes of power conversions and their control methods, regarding the limited time available in the courses, is a real challenge by the traditional methods. The static figures shown by the overhead projector or the computer projector with power point are not well suited for this purpose. On the other hand the possibilities by the modern multimedia methods can optimally be adapted in this area. Utilizing the opportunities of the technique, the sequence of topologies and transient processes of the system can well be shown by animated figures and understood easier. The basics of the method in most cases is the application of simulation techniques to obtain the results representing the complex processes. The advantages of animated representation are obvious in the study of both simple and complex units such as DC-DC converters, three phase inverter-fed induction motor drives, three phase UPS systems, etc. Within the framework of the Leonardo da Vinci program of the European Union (EU), a project called INETELE incorporating eight Universities from eight member countries is aimed at developing multimedia software for teaching the subject of Electrical Engineering (EE). The present paper is concerned only with a small fraction of the program developed by the team at the Budapest University of Technology and Economics in cooperation with a University in Japan and at the Delft University of Technology. There are basically two kinds of screens: S1; Screens for teaching in class. S2; Screens containing Supporting Text. S1 is designed for projection in classroom. Large letters, figures, tables are used. The information content is limited. S2 is designed for using it out of class-room for individual study. It applies smaller letters, figures, tables and contains substantial amount of information. It makes possible to study and learn the material of screens S1 at home for students without teacher. The Problems/Questions and Interactive Study are presented in the form of screen S2. There are two kinds of screen S1.: S1A contains animation, S1B has no animation at all. The second one is used to introduce or explain, support the screen S1A.

Virtual Laboratory for DC-DC Converters

Abstract The objective of the current paper is to present recent results on e-learning, including a virtual laboratory, designed for education of power electronics. The e-learning curriculum is suitable for both academic and industrial education in the frame of vocational training. It contains multimedia-rich presentation screens to teach the principles of the respective phenomena; furthermore, the interactive parts strongly support the deepening of the fresh knowledge. The interactive calculation tools facilitate the fast and simple model-development in web browsers for several often-used power electronic circuits (eg. static and dynamic models of DC-DC converters). Providing access to real circuits via online laboratory experiments is the next step for the trainees, allowing the change of several circuit parameters and the continuous monitoring of the system, even from long distances. It can have an important role in distance education too.