September 2013, Volume 13, Number 3
Summary: 
MAREK PASTOR — JAROSLAV DUDRIK — MAREK VACEK Predictive Power Control of Gridtied Multilevel Inverter [full paper] The paper presents a power control scheme for gridtied multilevel cascade inverter with L grid filter and modern predictive
current control technique. The reference current for current predictive controller is based on the required active and reactive power
supplied to the grid. The reference current is generated using instantaneous power theory (pq theory). The behaviour of the system
is simulated for different values of grid filter inductance and thus different grid current distortions. The quality of proposed control
scheme is evaluated as pq theory was originally designed for threephase active power compensators and can not be considered as
general power theory. The main advantage of proposed control scheme is its simplicity and fast response even with lower switching
frequency. Predictive controller enables the control to be designed in stationary reference frame without the need of resonant current
controller and PWM modulator.

ROMAN JAKUBČÁK — ĽUBOMÍR BEŇA — MIROSLAV KMEC Possibilities of Using Facts Devices In Power System [full paper] This article discusses about the issues of increasing loadability in power system (PS) by using FACTS (Flexible Alternating
Current Transmission System) devices, while reducing active power losses that occur in the transmission of power in the network.
For this purpose we used two types of FACTS devices. It is a TCSC (Thyristor Controlled Series Capacitor) and SVC (Static Var
Compensator). All simulations were performed in Matlab program.

MAREK PAVLÍK — IRAIDA KOLCUNOVÁ — BYSTRÍK DOLNÍK — JURAJ KURIMSKÝ — ALEXANDER MÉSZÁROS — DUŠAN MEDVEĎ — MICHAL KOLCUN — JÁN ZBOJOVSKÝ Measuring of Dependence of Shielding Effectiveness of Wet Materials on The Frequency of Electromagnetic Field in the High Frequency Range [full paper] This paper deals with measuring of shielding effectiveness of electromagnetic field. The measurements were focused on shielding
effectiveness while gradually drying out building materials in the range of high frequencies from 1 GHz to 13 GHz. The measured
object was fiber cement board facade Eterplan and exterior facade board Natura Pro. Thickness of the boards were 8 mm. The
measurement should prove that the shielding effectiveness of electromagnetic field of the wet materials is higher than the dry
materials.

JÁN BAČÍK — PAVOL FEDOR — MILAN LACKO SENSORIC SUBSYSTEM DESIGN FOR SMALL MODEL OF HELICOPTER [full paper] The paper deals with hardware design for sensoric subsystem of a small helicopter model and in real time generates data about
helicopter state variables during helicopter flight. The main unit for data processing presents an embedded computer built on a mini
ITX motherboard with processor Intel i3. As the helicopter presents a system with six degrees of freedom and in the fact, during the
flight, there is not any fixed point that would enable to calibre the sensors placed on the helicopter board, for processing of sensor
data Kalman filter is necessary.

YASSINE BELLEBNA — AMAR TILMATINE Application Of Dielectric Surface Barrier Discharge For Air Disinfection [full paper] The aim of this paper is to show that disinfection system using ozone generated by dielectric barrier discharge (DBD) is an effective alternative to be used in food industry and ensures a safe quality of air for optimum preservation of fruits and vegetables. The DBDs are specific kind of discharges because one (or sometimes both electrodes) is covered by a dielectric material, thereby preventing the discharge to move towards electrical breakdown. A succession of microdischarges occurs rapidly; their "lifetime" is in the range of a few nanoseconds. One of their most important applications is the production of ozone for air treatment, used mainly in the area of food industry, for extending the storage life of foods. After the achievement of a surface DBD reactor of cylindrical shape and its electrical characterization, it was then used as an ozone generator for air disinfection. Obtained results have shown that this reactor used as an ozone generator is effective for disinfection of air by removing viruses, bacteria and pathogens, causing the slowdown of the ripening process of fruits andvegetables.

M. RAMA PRASAD REDDY, T. BRAHMANANDA REDDY,Member, IEEE, B. BRAHMAIAH Vector Control of Induction Motor Drive by Using The Constant Switching Frequency Current Controller for Reduced Ripple [full paper] This paper presents a novel and simple vector control algorithm for induction motor drives. The classical vector control and
direct torque control algorithms give the decoupled control. But, the classical vector control algorithm uses reference frame
transformation, which increases the complexity of the algorithm for implementation. Whereas the direct torque control is simple for
the implementation by using the lookup tables approach, but, it gives large steady state ripple in torque, flux and current. Hence, to
overcome the drawbacks of both vector control and direct torque control, the proposed method combines the principles of both
vector control and direct torque control. In the proposed algorithm, the d and qaxes reference currents are generated as per the
principles of vector control algorithm and vector based hysteresis comparators integrated with lookup tables are used as per the
principle of direct torque control. Moreover, to reduce the torque ripple, a novel constant switching frequency current controller is
proposed. To validate the proposed method numerical simulations have been carried out and compared with the existing algorithms.
The simulation results show the effectiveness of the proposed technique.

MARTIN SMOČEK — ZDĚNEK HRADÍLEK Photovoltaic Power Plants, Extreme Change of Power Difference [full paper] Photovoltaic power plants are sources of electrical energy that are dependent on weather conditions. Consequences include their
stochastic change of the production power. The survey focus on assess the impact of photovoltaic power plants operation on the daily
load diagram with regard to output change difference of active power. Statistical methods have been employed to process a
methodology in order establish extreme conditions of production power for photovoltaic power plant. The already evaluated
minimum and maximum extreme conditions are applied to the daily load diagram. Evaluation is based on realtime synchronous
data measuring both onsite photovoltaic power plant operation and onsite electric power line output from the substation, where the
power plant is connected. This paper describes the methodology for determining the difference in the change of active power at the
power line output from the substation to ensure loads in this location.

DANIEL MAYER — BOHUŠ ULRYCH Evaluation of Mathematical Models Ac Magnetic Circuits [full paper] Present paper shows that even seemingly acceptable linearization of the mathematical model of harmonically excited nonlinear
magnetic circuit may lead to appreciable errors.

JAN VACULÍK — ZDĚNEK HRADÍLEK — PETR MOLDŘÍK — DANIEL MINAŘÍK Storing Solar Energy in Hydrogen [full paper] Using solar energy in photovoltaic power plants is an important method of electricity generation from renewable energy sources.
Its potential is vast and technically easy to utilise. The rapid development of photovoltaic sources is having a negative effect on the
electric power system control. One option for mitigating this effect is to store the energy generated by photovoltaic in times of excess
power in the grid and supply it to the grid when required, i.e., during peak periods of the daily load curve. Photovoltaic power plants
in connexion with a hydrogen storage system seems very promising as a sources of electric power in an island (offgrid) systems.
This paper describes our research into solar energy storage using hydrogen technologies in the case of offgrid systems. Storage in
hydrogen as an energy carrier is currently the focus of intensive research in many research centres.

M. RAJENDER REDDY, T. BRAHMANANDA REDDY, D. SUBBA RAYUDU Simple and Novel Unified Pulse Width Modulation Algorithm for Voltage Source Inverters in The Entire Modulation Range [full paper] This paper presents a simple and novel carrier based unified pulse width modulation (UPWM) algorithm for voltage source
inverter (VSI) fed AC drives. To reduce the complexity involved in the existing PWM algorithms due to angle and sector information,
the proposed UPWM algorithm uses the notion of imaginary switching times, which uses the instantaneous phase voltages only. To
validate the proposed algorithm at all modulation indices, a simple over modulation algorithm is also presented in this paper. By
varying the offset time in the proposed UPWM algorithm various continuous PWM (CPWM) algorithms like sinusoidal PWM
(SPWM) and space vector PWM (SVPWM) and discontinuous PWM (DPWM) algorithms such as DPWMMIN, DPWMMAX,
DPWM0, DPWM1, DPWM2 and DPWM3 can be generated at all modulation indices. To verify the proposed UPWM algorithm,
numerical simulation studies have been carried out and results are presented.

MARIÁN KLEŠČ — JANA PETRILLOVÁ On The Optimal Drawings Of Products Of Paths With Graphs [full paper] There are known several exact results of the crossing numbers of the Cartesian product of all graphs of order at most four with
paths, cycles and stars. Moreover, for the path P_{n} of length n, the crossing numbers of Cartesian products GP_{n} for all connected
graphs G on five vertices and for forty graphs G on six vertices are given. In the paper, we extend these results by determining the
crossing numbers for the Cartesian products of paths with two special graphs of order six.
