Tallinn University of Technology

Recently, a PhD student at the Department of Electrical Power Engineering and Mechatronics of TTÜ, Jaan Niitsoo, defended his doctoral thesis "Residential Grids Power Quality Analyses Concerning Nonlinear Consumer Loads and PV Panels".

The world is heading rapidly towards more intensive employment of renewable energy sources, which will increasingly affect conventional electricity grids. This change will in turn affect, among other indicators, the power quality.

So far, power plants have produced electricity with a sinusoidal voltage (by means of a conventional rotating generator) and thus all appliances are designed to work with a sinusoidal voltage. Presently we have reached a situation in which an increasing number of generating units are based on power electronic components, which are causing new types of abnormalities. These converters do not always produce a perfect sinusoid waveform and higher frequency components occur in addition to the desired 50 Hz frequency.

In addition to electricity production, the electricity consumers are increasingly using electronic devices, which in turn distort the voltage in the grid.

The supervisor of the doctoral thesis, Ivo Palu, Professor at the School of Engineering says, "An increasing number of generation units and consumer loads operating on new principles are connected into the existing grid built in accordance with the old principles, which leads to various challenges in this field. More and more problems arise with regard to the existing conventional devices and various grid components. Power quality deterioration can cause failures in the existing electrical devices or decrease the lifespan of the devices and increase power losses."

The electronic devices that are presently being used have very different technical characteristics and comprehensive research should be carried out before widely implementing them into the electrical grid. All characteristics of the devices, the possibility of integration, and the level of compatibility have to be clarified.

"The defended thesis lays the foundations for further more extensive research and proves that more comprehensive measurements have to be carried out. Precise electrical models for grid and grid connected devices have to be composed to investigate their compliance with the grid," Professor Palu explains.

The supervisors of the doctoral thesis were Professor Ivo Palu and Senior Research Scientist Paul Taklaja (TTÜ).
The opponents were Professor Saulius Gudžius (Kaunas University of Technology) and Professor Andres Annuk (Estonian University of Life Sciences).

The doctoral thesis has been published in the digital collection of TTÜ library: https://digi.lib.ttu.ee/i/?6995

Kersti Vähi, Research Administration Office