SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 16, No. 3, October 2019
CONTENTS
Design and Analysis of a Three Phase Transformerless Hybrid Series Active Power Filter based on Sliding Mode Control Using PQ-theory And Stationary Reference Frames
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DOI: https://doi.org/10.2298/SJEE1903289N
Abstract: In this work, a Three phase Transformerless Hybrid Series Active Power Filter (THSeAF) based on Sliding Mode Control (SMC) is proposed to mitigate the voltage and current distortions present in an electrical distribution systems (EDS). A Sliding Mode Controller is designed by controlling the parameters present on the load side as well as source side of the system. Three separate voltage source converters (VSC) are used. The mod1elling of the system is derived by considering a single-phase system by using state space analysis. The frequency response characteristics have been derived for the single-phase system and the stability of the system is studied. It is observed that the system has good stability margins when the SMC is applied at the source side compared to load side. Simulation results obtained in PSCAD/EMTDC v4.6 have been observed for power quality issues like voltage sags, voltage swells, voltage distortions, voltage unbalances and their concurrent occurrence. The approach of stationary reference frame was used for source side control and PQ theory is used for load side control. It is observed that the proposed controller works well in obtaining a stable and constant load voltage during these power quality issues. The difference in settling time observed is around 4 ms for the load side and source side control. The THD present in the load voltage is near about 1%. The SMC is found to be robust in obtaining a constant load voltage with low THD and an improved power factor.
Keywords: Electrical Distribution System (EDS), Sliding Mode Control (SMC), Transformerless Hybrid series Active power Filter (THSeAF), Voltage Source Converter (VSC).
Experimental Study of the Behaviour of the Crosstalk of Shielded or Untwisted-Pair Cables in High Frequency
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DOI: https://doi.org/10.2298/SJEE1903311B
Abstract: Electromagnetic disturbances from natural phenomena such as lightning, or those generated from industrial activity, can cause harmful interference in on-board electronic systems. The disturbances are generally transformed into radiated and conducted disturbances, using wired connections to spread their effects in electrical and electronic systems. In order to identify the paths of propagation and coupling of these HF currents into a complete system and propose solutions to reduce EMC interference, it is necessary and important to carry out experimental case studies on the coupling between shielded as well as unarmoured cables, in order to identify the importance of differential and common-mode currents. Measurements were made using a 4-way vector network analyser giving the results of the crosstalk between victim and culprit cables as well as for module and phase.
Keywords: EMC shielded cable, crosstalk, electromagnetic interference, common mode, differential mode.
Adaptive Quantum-Inspired Evolutionary Algorithm for Optimizing Power Losses by Dynamic Load Allocation on Distributed Generators
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DOI: https://doi.org/10.2298/SJEE1903325M
Abstract: In this paper, an Adaptive Quantum-inspired Evolutionary Algorithm (AQiEA) has been applied for minimizing the power losses in the distribution network by suitable placement, sizing and subsequent allocation of load on Distributed Generators (DG) for a varying load with a time horizon of twenty-four hours. Many efforts have been reported in the literature to minimize power losses. However, they have mostly used a fixed load, i.e., nonvarying load, whereas it is well known that load in distribution network varies during the day. An investigation was undertaken to find the reduction in power losses on a time-varying load. It has been found that the average power losses for dynamic load allocation on DGs for every hour have a maximum reduction in power loss as compared with other well-known cases in the literature. Optimal location and size of DG is a difficult nonlinear, non-differentiable combinatorial optimization problem. AQiEA is used to find the appropriate location and capacity of DG for a varying load with a time horizon of twenty-four hours to minimize the power losses. AQiEA doesn’t require additional operators like local search and mutation to improve the convergence rate and avoid the premature convergence. A Quantum Rotation inspired Adaptive Crossover operator is used as a variation operator, which is parameter free. The effectiveness of AQiEA is demonstrated on two test bus systems viz., 33 bus system and 69 bus system, which are used as benchmark problems for validating the proposed methodology as well as for comparative testing amongst existing techniques. Wilcoxon signed rank test is also used to demonstrate the effectiveness of AQiEA. The experimental results show that AQiEA has better performance as compared to some existing ‘state of art’ techniques.
Keywords: Distributed Generators; Twenty-four-hour load; Power losses; Dynamic load allocation; Entanglement & Measurement Operator; IEEE 33 & 69 bus system.
State Estimation of the Voltage Conversion Process in a Solar Power System with Kalman Filter
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DOI: https://doi.org/10.2298/SJEE1903359G
Abstract: The state estimation of the voltage conversion process (with Kalman filtering) in a solar power system is shown in this paper. Theoretical principles of solar power systems are presented, along with the position and working principles of a DC-DC boost converter in a solar power system. Different modes of state estimation of the voltage conversion process are shown, along with a detailed explanation of the Kalman filter appliance. This approach can be applied to one of the maximum power point tracking systems (MPPT). In the practical section of this paper, the implementation of noise filtering concepts in a solar power system is shown, by using the National Instruments LabVIEW programming suite. Processes that occur in this type of system are simulated, and the basic principles of noise cancellation are explained, in order to achieve optimal working conditions.
Keywords: Boost Converter, Kalman Filter, Maximum Power Point Tracking System, Solar Power System, State Estimation.
Design of a Novel Chiral Fractal Resonator
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DOI: https://doi.org/10.2298/SJEE1903377M
Abstract: In this paper, we presented a compact resonator using a planar chiral fractal tree structure, where the chirality and the fractal form can combine several features at once. The chiral properties of this resonator, which are discussed based on their optical activity, circular dichroism, and the effect of the number of the iteration. Our chiral fractal structure is of major interest in scientific research, their characteristics have given rise to interesting new applications. Numerical results are given and discussed to confirm.
Keywords: Chiral media, Fractal form, Finite element method simulation.
Optimal HOG Cell to Image Ratio for Robust Multi-Sensor Face Recognition Systems
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DOI: https://doi.org/10.2298/SJEE1903387P
Abstract: The main problem for modern visible light face recognition has been accurate identification under variable environmental conditions. Thermal infrared facial images utilization in face recognition systems can provide a solution for problems related to uncontrolled environmental conditions, especially to those caused by illumination limitations. This paper compares the results of the use of visible light and thermal infrared imagery for face recognition based on the HOG feature descriptor. In particular, the paper suggests an optimal HOG cell to image size ratio in order to improve recognition accuracy and reduce computational complexity. Performance statistics are presented on facial images with different facial expressions. The obtained results support the conclusion that recognition with thermal infrared images is more robust and that fusion of sensors should be included for improving recognition accuracy.
Keywords: Face recognition, Visible light imagery, Thermal imagery, Image scaling, Facial expression, HOG.
Model for Speech Signal Quality Estimation in Packet Network of Electricity Supply Industry
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DOI: https://doi.org/10.2298/SJEE1903405L
Abstract: In this paper we present the dilemma dealing with the choice of speech segment duration and the calculation of speech signal quality in the packet telephone network of Electricity supply industry (ESI). The analyzed signal is packetized by one packet. The characteristic of this network is that disturbances of long duration in power system produce burst packet loss. The longer speech segments increase the packet delay, but decrease the number of lost packets in one burst, and vice versa. Here we present why it is better to choose speech segments of short duration. Also, we suggest the corrected method for the calculation of speech signal quality in packet network under the influence of long duration disturbances.
Keywords: Delay effects, Electricity supply industry, Internet telephony, Power system transients, Quality of service.
The Concept and Application of Simplified Robotic Models
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DOI: https://doi.org/10.2298/SJEE1903419D
Abstract: The use of robotic models with the main functionalities of real objects together with the implementation of innovative technologies, augmented reality (AR) in this case, is the focus of the paper. Therefore, the concept of a simplified robotic model (SRM) is presented. This concept is important because it is useful for achieving the goals of engineering projects, which is especially justified prior to the construction of the real objects. It improves presentation, development, and education capabilities that are unavoidable segments of the project strategy. Additionally, it is possible to transfer developed solutions to the final objects after certain modifications. Multidisciplinary building of the unique SRM of the 3-axis centrifuge for pilot training is described, where multi-attribute decision-making is used to conduct some experiments. The application includes the use of a physical model, built from LEGO elements, software for controlling and monitoring the physical model, and an AR mobile app.
Keywords: Simplified robotic models (SRM), Centrifuge for pilot training, LEGO, Augmented reality (AR), Multi-attribute decision-making (MADM).
Time Domain Analysis of Excess Loss in Electrical Steel
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DOI: https://doi.org/10.2298/SJEE1903439K
Abstract: The aim of this paper is to present a comprehensive approach to analyse and interpret power loss in ferromagnetic materials with particular attention devoted to excess power loss. Experimental results obtained with an Epstein frame and toroidal core made of electrical steel are presented in the paper, including quasistatic and dynamic hysteresis loops. According to the time waveforms of the measured magnetic field and magnetic flux density, an instantaneous power loss is calculated for the quasistatic and dynamic case. Moreover, the instantaneous power loss due to eddy current is calculated, as well as the instantaneous excess power loss and excess magnetic field. This excess magnetic field is compared to the excess magnetic field calculated by Bertotti’s model. Analysis and discussion of the results obtained is given in the paper.
Keywords: Time Domain, Power Loss, Excess Power Loss, Electrical Steel.