80    ELEKTROTEHNIŠKI VESTNIK 79(1-2)   
    PHD PROPOSAL 
Optimal sun-tracking of a photovoltaic system considering the 
electric drive losses 
Sebastijan Seme, mentor: Gorazd Štumberger, Jože Voršič  
Faculty of Electrical Engineering and Computer science, University of Maribor  
E-mail: sebastijan.seme@uni-mb.si 
 
Abstract. Doctoral thesis deals with optimal sun-tracking of 
a photovoltaic system considering the electric drive losses. 
The Sun tracking PV system assures that the highest possible 
share of the available solar radiation reaches the surface of the 
PV modules. The electric drive which enables tracking is 
considered as the loss of the energy produced in the PV 
system. The maximum of the energy produced in the PV 
system is achieved by the continuous tracking of the PV 
system. Since the electric drives are determined by constant 
speed and time, and angle quantization the maximum of the 
energy produced can only approximate. 
 The doctoral thesis presents a new method for determining 
such trajectories of the PV modules that change the position of 
the PV modules in such a way that the production of the 
electric energy in the given time interval of the observation 
reaches its maximum. The goal is to determine the maximum 
efficiency of the PV tracking system considering the tracking 
system energy consumption. To achieve this, exact values of 
the available solar energy are needed for a given moment. To 
do this, a new method for predicting direct and diffuse solar 
radiation on the Earth’s surface, in the form of the time 
dependent function, is developed. The method is confirmed by 
the comparison of the measured and the predicted solar 
radiation for clear days. The developed method for predicting 
the solar radiation in the form of the time dependent function 
and energy consumption of the tracking system, given as the 
functions of the azimuth and tilt angle change, are applied 
together to determine those trajectories of the PV module, 
where the PV system energy production, gives the maximum. 
To find a solution of the nonlinear and bounded optimization 
problem, a stochastic search algorithm called Differential 
Evolution is applied. The approach for determining the 
maximum of the energy produced in the PV system has not 
been researched yet. The explicitly defined objective function, 
which is minimized in the optimization procedure considering 
the optimization bounds, is used. Thus it is assured the 
maximum of the possible energy produced in the PV system, 
considering the applied model of the PV system, tracking 
system consumption, predicted solar radiation, and the 
properties of the applied optimization method. The use of the 
different and more advanced models of the PV system, the sun 
tracking system consumption or prediction of the solar 
radiation, can lead to the different optimal trajectories of the 
sun tracking system. However, this cannot reduce the 
importance of the proposed method. The proposed method 
gives the maximum of the possible energy produced in the 
discussed PV system, considering the applied models and 
data. 
  
Optimal Arrangement of Overhead Power Line Conductors 
Considering Emissions of Electromagnetic Fields and Audible 
Noise 
Klemen Deželak, mentor: Gorazd Štumberger, co-mentor: Franc Jakl 
Faculty of Electrical Engineering and Computer science, University of Maribor 
E-mail: klemen.dezelak@uni-mb.si 
 
Abstract. The legal procedures to obtain the right of way for 
the new overhead power lines in Slovenia are extremely 
difficult nowadays. Due to the large public opposition against 
the building of the new overhead lines is necessary to invest a 
lot of effort in both, the planning of overhead power lines and 
the minimization of their impacts on the environment.  
 In that sense, within the given overhead power line right of 
way, all of the impacts on the environment should be under 
prescribed limits. Therefore, most of our attentions should be 
devoted to minimize emissions of the electromagnetic fields 
and the audible noise.  
 The aforementioned emissions depend mostly on the values 
of overhead power line voltage, current and geometrical 
arrangement of conductors. Especially with the proper 
arrangement of the overhead power line conductors the 
emissions of the electromagnetic fields and the audible noise 
could be essentially reduced.  

   
 Moreover, with an appropriate software tool, the optimal 
arrangement of conductors, with respect to the given objective 
function, could be determined.  
 Such an optimal arrangement of the conductors can be 
determined with the Differential Evolution based optimization 
environment proposed in this dissertation. It contains the 
module for calculating the audible noise emissions as well as 
the module for calculation the emissions of the 
electromagnetic fields. In the calculations it is possible to 
consider the sagged conductors or their approximation with 
the straight conductors. 
 The aim of this dissertation is to find an optimal 
arrangement of the three-phase power line conductors. The 
acceptable emissions of the electromagnetic fields and audible 
noise are considered as the optimization bounds, while the 
optimization goal is the minimal height of the tower defined 
with the attachment of the overhead ground wire.  
 The developed software tool can be used for designing the 
new overhead power lines, where the restrictions as the width 
of the overhead power line right of way, the safety clearances, 
the allowable emission of electromagnetic fields and audible 
noise are considered.  
 Additionally, the proposed software tool can be applied to 
check where the overhead power line with the lower rated 
voltage level can be upgraded to the higher rated voltage level 
inside already existing right of way.