Project partners - Universities
University of Maribor (Slovenia)
The general description of FERI The Faculty of Electrical Engineering, Computer Science and Informatics (FERI) at the University of Maribor
is a scientific institute with explicitly regional, national and international significance. Its regional significance is reflected in its close co-operation
with industry, while its international significance is reflected in the faculty's participation in international research activities with
numerous projects, exchange of students and professors, publications in respected scientific magazines, participation at international conferences
and the organization of the same. Being a part of the University of Maribor, FERI is responsible for education in the fields of electrical
engineering, telecommunications, computer science, informatics, mechatronics and media-communication sciences. Since the scientific knowledge is
the foundation for its operation, faculty activities are mainly organized as:
A) Pedagogical, where the educational process is implemented in post graduate, university and professional programmes, andB) scientific-research,
where the fields of electrical engineering, telecommunications, computer science and informatics are researched.
Description of activity of the Laboratory for power electronics
The Laboratory for power electronics is incorporated in Institute of robotics, which belongs with Faculty of electrical engineering and
computer sciences (FERI) at the University of Maribor, Slovenia. As a part of the Institute of robotics we cover the wide subjects
in power electronics area. These activities are indicated below:
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Digitally controlled DC-DC converters.
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Electromagnetic compatibility of power electronics converter.
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Matrix AC-AC converters.
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Cascade structured AC-AC converters.
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Resonant link converters.
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AC-DC converters for utility application
Ad 1: Digitally controlled DC-DC converters
The digitally controlled step down converter using fuzzy state space control law algorithms is studied. The state controller is designed
to eliminate the start-up overshoot and reduce maximal dynamic error of load change response. The improvement in steady state controller
has been done by using fuzzy state space controller. The algorithms developed for the step down converters can be implemented in custom
designed FPGA which is leading towards the application with single chip solution.
Ad 2: Electromagnetic compatibility of power electronics converter.
Randomized pulse width modulation algorithms applied in step down and step up DC-DC converters have been studied. These algorithms are capable
to improve the converters electromagnetic compatibility.
Ad 3: Matrix AC-AC converters
For a matrix structured direct AC-AC converter the different modulation strategies are studied. In principle, for a given set of input three
phase voltages, any desired set of output voltages can be synthesized by suitable toggling matrix switches. A mathematical proof that the
direct AC-AC matrix converter can operate with the unity power factor was provided by the analysis which is coming from switching matrix approach.
Symmetric and anti-symmetric switching strategies were developed for synthesizing an output voltage vector from appropriate combination
of input voltage vectors. The unity power factor operation can be achieved by using the combined symmetric and anti-symmetric modulation strategies.
These combined algorithms enable unity power factor operation without current sensing and current control.
Ad 4: Cascade structured AC-AC converters.
The three-phase cascade-structured AC-AC converter with improved input to output voltage ratio has been studied. This converter is capable
of generating at an output three-phase voltage with variable frequency and arbitrary magnitude. At the moment there is considerable interest
in power electronic converters designed with AC -AC conversion having adjustable magnitude and output voltage frequency. The general AC-AC
matrix converter with 18-unidirectional switches has a limited input to output gain (g = 0.5 and improvement of 0.866) and the possibility
of adjusting input displacement factor (IDF) and/or unity power factor (PF) by using an appropriate modulation strategy.
The modulation algorithm for a cascade-structured ac to ac converter can improve the voltage gain over 0.866. Furthermore, with the twelve-unidirectional
switches it is able to perform IDF correction and all aspects of magnitude and frequency changes on the converter output terminals. This algorithm
was investigated theoretically and verified by simulation.
Ad 5: Resonant link converters
The term HF-AC Resonant Link Converters usually denotes a circuit, whose main part is a resonant tank circuit. The main goal of designer
of such circuits is to reach a constant magnitude of output voltage with constant frequency and independence of load conditions. The maintenance
of the constant HF-AC voltage on parallel resonant circuits (frequency 25 kHz) from main supply has been studied and verified by experiment.
Ad 6:
Modulation strategy for a matrix structured AC-DC converter is studied and developed. This modulation strategy enables the input displacement
factor correction without current sensing. Mathematical proof that AC-DC converter can operate with unity input displacement factor is
provided by analysis based on the switching matrix approach. Computer simulation and experimental results supporting this ability are reported.
This algorithm enables the unity power factor operation without current sensing and current control.
We have concluded with the statement that all above described activities are appropriate for HySYS project (WP 4200).
