Invited Speakers

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- Assoc. Prof. Dr. Jožef Ritonja

- Prof. Dr. Jūras Banys

Prof. Dr. Bogdan Miedzinski


Assoc. Prof. Dr. Jožef Ritonja (University of Maribor/ Maribor, Slovenia)

Electromechanical Oscillations in Power Systems: Analysis and Damping

Monday, 13th June, 10:15–11:00, Room A

Jožef Ritonja received his B.S., M.S. and Ph.D. degrees in Electrical Engineering from University of Maribor, Faculty of Electrical Engineering and Computer Science in years 1986, 1989 and 1996, respectively. Since 1987 he has been working at University of Maribor, Faculty of Electrical Engineering and Computer Science in a field of Control Theory and Control Applications. He is an Associate Professor and a Head of the Laboratory for Control and Electrical Machines.

New energy sources, storage facilities, power electronics devices, advanced and complex control concepts, economic operating doctrines, and cost-optimized construction and production of machines and equipment adversely affect oscillations and associated stability of power systems. The problem of electromechanical oscillations in power systems was considered. It was addressed in two stages. First, a more detailed analysis of electromechanical oscillations was accomplished. Secondly, the use of advanced control approaches to damp these oscillations was shown.

To develop a control system for damping oscillations, it is necessary to analyze local mode oscillations and the causes that affect them. There are no recognized analyses of the oscillations of modern operating synchronous generators exposed to new conditions in power systems. A numerical analysis of local oscillations of a large number of synchronous generators in the power system was performed. Analyzed were 74 synchronous generators of the Slovenian power system, plus many additional synchronous generators for which data were accessible in references. The mathematical models convenient for the study of local oscillations were discussed. The influences of transmission lines, size of the synchronous generators, operating conditions, and control systems were investigated. The applicable rules have been defined to help power plant operators to avoid stability-problematic situations. The boundaries were estimated of the eigenvalues of local modes. The obtained results enable the prediction of local oscillations’ frequencies and dampings and will be useful in PSS planning.

Within the oscillation analysis, it was seen that the currently used power system stabilizers are not up to the needs of modern power systems. Based on the results of the analysis of the advanced control approaches it was found out that the most appropriate solutions are adaptive control and robust control. Advanced approaches were analyzed and compared with the conventional linear power system stabilizer.


Prof. Dr. Habil. Jūras Banys (Vilnius University / Vilnius, Lithuania)

Microwave Spectroscopy of Ferroelectrics and Related Materials 

Monday, 13th June, 11:45–12:30, Room A

Jūras Banys is a Pro­fessor at Vilnius University. In 1985, graduated with honours from Vilnius University Faculty of Physics. In 1990 defended his doctoral dissertation in that same Vilnius University and in 2000 received his habilitated doctor degree and docent’s academic rank. In 2003, again in Vilnius University, he was awarded a professor’s title. He produced over 400 scientific papers with most of them being published in international scientific magazines. Participated in international scientific conferences in Germany, Great Britain, Italy, Latvia, Czech Republic, Poland, France, USA, and elsewhere (over 300 presentations, 26 of which being given upon special invitations). He is a real member of the Lithuanian Academy of Sciences, board member of the Research Council of Lithuania, foreign Member of the Latvian Academy of Sciences, corresponding member of the Saxon Academy of Sciences (Germany), board member of the Lithuanian Physical Society, editorial committee member of the Lithuanian Journal of Physics, member of: the European Polar Dielectrics Application Committee, the European Ferroelectricity Committee, the European Electroceramics Committee, Global Ferroelectricity Committee, the AMPERO Group Committee, the IEEE FerroCom.

The dielectric response of materials provides information about the orientational adjustment of dipoles and the translational adjustment of mobile charges present in a dielectric medium in response to an applied electric field. Microwave and terahertz dielectric spectroscopy of ferroelectrics and related materials enables the independent determination of the dielectric permittivity and loss in the dispersion region, as well as the parameters of the soft modes related to phase transitions. Besides scientific purposes, microwave dielectric measurements are of increasing importance in telecommunications related applications and the design of microwave circuit components. The magnetic properties are also of crucial importance. Dielectric and magnetic parameters fully characterize the manner in which electromagnetic waves propagate within the medium. The difficulties of making measurements on a wide range of materials over a wide frequency (and temperature) range have led to the development of various direct and indirect methods. Computers allow the computation of electromagnetic fields in entirely new measurement geometries and the use of numerical analysis in the direct measurement process. Each investigator employs the method adequate for the size and shape of a sample. The most important problem now is the rigorous mathematical solution of the microwave interaction with the samples in various geometries. Although there is now complete overlap and coverage of the radio frequency to the infrared band, the different experimental methods based on coaxial, waveguide, resonator and free – space technique is still divided and will be presented.




Prof. Dr. Habil. Bogdan Miedzinski (KOMAG Institute of Mining Technology / Gliwice, Poland)

Selected Problems and Prospects of Effective  BPL PLC Application in Wired Medium of Electric Grids

Tuesday, 14th June, 9:45–10:30, Room A

Bogdan Miedzinski is currently a professor at the Karkonosze Academy of Applied Sciences in Jelenia Góra . However,he is still active at the Wrocław University of Technology, cooperating also with such scientific organizations like  the Tele and Radio Research Institute in Warsaw and the KOMAG Mining Technology Institute in Gliwice Poland . He still keeps and developes  extensive foreign contacts.

In the PLC (Power Line Communications) technology, power networks are simultaneously used, regardless of the main purpose, which is the transmission and distribution of electricity , as a transmission medium for communication.. Commonly, is used Narrow Band PLC, which provides the transmission of signals at a maximum speed of 100-200 kb / s (kilobits per second). Here,the frequency of the carrier signal (in the power line) is from a few to several hundreds kHz (2 kHz - 150 kHz). However,the BPL (Broadband PLC) is a broadband PLC transmission, that allows  the signals to be transmitted at a much higher speed, up to 200 Mb / s (Megabits per second). It is  around 1000 times faster than in narrowband communication. The carrier signal is then  in the band 2 to 30 MHz. It should be noted here that the practical use of BPL faces limitations due to tendency to interfere with the work of others important users like military or civil systems using selected bands in the BPL frequency range. Currently, fortunately the BPL solutions offered on the market (by reputable companies) enable blocking the PLC  transmission within selected frequency bands. It should also be mentioned that the expansion of the use of BPL technology is not favored by strong competition from wireless technology operators. The main task of power grids is the delivery of electricity from the producer to the user. Therefore, all other uses of these networks, including, inter alia, PLC communication, should meet all existing technical conditions and limitations of power grids.  However, the structure and physical characteristics of this wired medium  differ quite significantly from traditional communication channels (twisted pair, Ethernet, coaxial cable or optical fiber). A significant threat here are all kinds of disturbances during the operation of the power grid (short-circuits, interruptions in operation, topology change, etc.). One of the areas of effective use of BPL technology seems to be mining networks due to the possibility, above all, of increasing the safety of the mine's operation.

It should be noted that all kinds of transient states due to  switching operations can be  the source of both transmitted and induced disturbances. Any disturbances appearing cyclically in specific time intervals are treated as the main disturbances - the so-called "Background noise". The other types of disturbances are random in nature and are generally treated as random impulse disturbances. The main implementation task of the BPL-PLC system is the modeling of the communication channel in the power line  and asynchronous impulse disturbances, it is also possible to map power line branches, the presence of which affects the deterioration of transmission efficiency.. In order to determine the usefulness of the BPL-PLC transmission in practice, appropriate tests of its effectiveness were carried out in the selected medium voltage mining networks. The existing  6 kV cable network supplying the converter transformers was selected for the tests due to the significant level of the content of higher current harmonics, and thus the potential high risk of interference.

On the basis of the obtained research results, the practical possibilities of using the BPL-PLC transmission in mining conditions were determined.