Electrical Computer Engineering

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    ARTIFICIAL NEURAL NETWORK BASED FAULT CURRENT MINIMIZATION IN DISTRIBUTION SYSTEM USING SUPERCONDUCTING FAULT CURRENT LIMITER. (CASE STUDY: HOSANNA SUBSTATION-DISTRIBUTION SYSTEM)
    (Hawassa University, 2021-08-17) ZENABU DUGUNO WAKERO
    High magnitude of short circuit fault current takes place in electric power distribution system. This unexpected high magnitude of short circuit fault current can cause the failure of Hossana substation switchgear equipment’s and even if due to this problem most of industries sharing power from Hossana substation and end users of Hossana substation cannot get power properly. So, fault current minimization in distribution system is a critical issue and to minimize the maximum short circuit fault current in distribution system, superconducting fault current limiter (SFCL) device is applicable in this thesis work. By installing superconducting fault current limiter (SFCL) device to the Hossana substation distribution feeder especially for Gimbichu feeder maximum short circuit fault current to be minimized for different types of short circuit faults like, Line to Ground (L-G) fault, Line to Line (L-L) fault, Double line to Ground (LL-G) fault and balanced three phase faults in distribution feeder. Under this thesis work the case study area focus on Hossana Substation - Distribution system feeders especially from the nine of feeders Gimbichu 15KV feeder. The reason why this feeder is selected is because of this feeder covers long distance approximately 150KM and high system interruption take place frequently. In this thesis work ANN controller is used to control the SFCL device and both ANN controller and SFCL device are modeled in MATLAB/Simulink. After developing SFCL in MATLAB and connect this device to the distribution feeder it is possible check the fault current magnitudes before and after installing SFCL device to the system. Before installing SFCL device to the system the magnitude of short circuit fault current is 20KA to 40KA for L-G fault, L-L fault, LL-G fault and balanced three phase faults in Gimbichu 15 KV feeder. But, after installing SFCL device to the case study area maximum short circuit fault current magnitude become minimized 140A up to 150A for all types of short circuit faults. Finally, the payback period is calculated after installing SFCL device to the 15KV Gimbichu feeder. Therefore, the calculated payback period is 1.14 years i.e., the year of back payment of this thesis work is 1 year,1 month and 21 days
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    EVALUATING CRYPTOGRAPHIC ALGORITHMS OF AUDIO AND VIDEO DATA FOR SYSTEM RESOURCE CONSTRAINED OF IoT DEVICES
    (Hawassa University, 2019-10-27) WAGARI BERHANU
    We are living in an internet period in which digital data exchange in electronic way has progressed tremendously and securing information has become a challenge. Unless a creative means of securing information has been developed, the problem will be vast and limitless. In a bid to keep the pace of the era, cryptography plays an important role in information security systems. Cryptography is a process of creating information indecipherable to an unauthorized person. It is quite a well-known fact that IoT (Internet of Things) is a system of interrelated computing devices or digital machines is the ability to transfer data over a network. the devices that used in IoT is low power devices for this reason, the system resource is one sever issues. To do so various cryptographic algorithms used in IoT devices. Meanwhile, these algorithms consume a significant amount of computing resources such as CPU time, memory and computation time. This thesis provides evaluating AES, Blowfish, RSA, Trivium and Elliptic Curve Cryptosystems based on system resource usage to securing IoT device communications on the basis of encryption time, decryption time, throughput, CPU time, power efficiency and memory usage in audio and video data using Java as the programming language to develop algorithms. The result obtained shows that AES has better performance with encryption time, decryption time, throughput rate, CPU time, power efficiency and memory usage with audio and video files in various format
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    PERFORMANCE COMPARISON OF CHANNEL MODELS FOR UFMC SYSTEM
    (Hawassa University, 2019-08-29) TILAHUN BELAYNEH MAMO
    This paper presents the bit error rate (BER) vs. signal-to-noise (SNR) ratio performance of channel models under UFMC system with 32- FSK, PAM, DPSK, 4-QAM, 16-QAM, 32-QAM, 64-QAM and 128-QAM modulation. In future it is believed to be more challenging and complicated with the evolution of different types of fading model. These types of fading models determined in urban and rural areas. Rayleigh fading model is considered to be most common fading model, found in urban environment for non-line of sight. Rician fading consists of line of sight communication and found to be more applicable for satellite communication. Nakagami fading model is mostly suited for urban multipath propagation and it is sought to be most practical model, specially used in mobile communication. In order to achieve error free signal at the receiver the choice of modulation scheme should be done wisely. The combination of best efficient modulation scheme along with the block coding helps in getting the signal error free at the receiver. The condition of signal is decided by SNR v/s BER (bit error rate) simulation. Our main objective is to get error free result at the receiver, so for this different data transmission techniques are used to transmit the data from transmitter to receiver in various fading channels under different modulation schemes. Effect of shape factor on Nakagami fading is also covered in this thesis to get efficient results. The BER performance was to compared with Additive White Gaussian Noise (AWGN), Rayleigh-faded, Nakagami-m faded and Rician-faded channels. It has been further concluded that the BER vs. SNR performance graph in AWGN channel environment is better than that in Rayleigh, Nakagami-m and Rician-faded channel. It is also observed that by varying the standard-deviation of the channel, the BER vs. SNR performance graph is not going to be affected if the channel is considered Rayleigh-faded. In this paper we address a new aspect of UFMC system performance by investigating its capability to overcome the channel fading channels’ effects and to provide good and reliable performance levels overcome these channel effects.
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    Design of Wavelength Division Multiplexing based Passive Optical Network Transmission System using Heterodyne Receiver for 5G Transport
    (Hawassa University, 2022-12-11) Wondmagegn Wana
    Fifth Generation network standard has put higher peak data rate (10x) and very low latency requirements (1/10) as compared to its predecessor 4G network. In any mobile network implementation, the transport network is critical component for delivering the intended services. The demand for high data rate in 5G requires massive capacity upgrade in the transport network. On the other hand, latency in 4G and older technologies is too much as compared to 5G requirements. Hence Building low-latency and high-capacity transport networks is vital for new high-speed cellular technologies. Optical fiber-based technologies are essential to meet the high bandwidth demands of 5G transport Network. The two contending optical technologies for 5G transport are point-to-point (P2P) fiber access and point-to-multipoint (P2MP). P2P fiber access has low fiber efficiency and requires infrastructure installation for new deployment. Point-to multipoint fiber has high fiber efficiency as compared to P2P. Among the P2MP fiber options, TDM-PON uses dynamic bandwidth allocation (DBA) to multiplex services which introduces 1ms delay. On the other hand, WDM-PON doesn't require DBA, thus is a good candidate for low latency services. Studies on WDM-PON are using homodyne receiver. The proposed network was simulated in Opti Wave Optisystem simulation software. In this thesis, a new 2.4 Tbps WDM-PON based network using heterodyne receivers was built as solution for 5G transport network requirements. The performance of the new system was compared with back to-back model using BER and OSNR. An OSNR of 15.4 is required to obtain a BER of 10−3 dB for Heterodyne System while an OSNR of 14.8 dB is required for Back-to-Back System which is 0.6 dB higher. The results obtained from the Heterodyne system simulation are very close to the result found in case of back-to-back system. Hence, the WDM Dual Polarization 8-PSK PON system with heterodyne receiver can be used in 5G transmission
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    Integrated energy optimization of smart home appliances with cost-effective energy management system (Case Study: Mid-Size Residential Home at Hawassa City
    (Hawassa University, 2019-10-27) Tesfahun Molla
    With the development of smart grid technology, residents have the opportunity to schedule their power consumption pattern in their home by themselves for the purpose of minimizing electricity expense, reducing the peak-to-average ratio (PAR) and peak load demand. The two way flow of information between electric utilities and consumers in smart grid opened new areas of applications. In this thesis, a general architecture of home energy management system (HEMS) would be introduced in a home area network (HAN) based on the smart grid scenario and then an efficient scheduling method for home power usage would be proposed. The energy management controller (EMC) receives the demand response (DR) information indicating the Time-of use electricity price (TOUP) through the home gateway (HG). With the DR signal, the EMC achieves an optimal power scheduling scheme that can be delivered to each electric appliance by the HG. The rooftop photovoltaic system used as local generation micro grid in the home and can be integrated to the national grid. These results in reduction of electricity bill and when solar energy production is more than the demand of the home, the excess energy could be exported to the national grid. Accordingly, all appliances in the home operate automatically in the most cost-effective way. Detail explanation and discussion of four scheduling techniques would be designed under TOUP. To calculate the fitness function; two powerful swarm intelligence based Meta-heuristic algorithms i.e. Grey wolf optimizer (GWO) and Particle swarm optimization (PSO) algorithms had been used. Finally, detail comparison and analysis between proposed methods and algorithms could be carried out. To display the result, MAT LAB 16(a) software environment would be used
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    DISTRIBUTION SYSTEM RELIABILITY IMPROVEMENT USING DISTRIBUTED GENERATION AND NETWORK RECONFIGURATION
    (Hawassa University, 2021-10-28) MEKLIT GIRMA
    Power supply reliability is the basic issue for economic and technology development of the country. The sufficient or adequate and secure supply of power will assure the reliability of the system. Unreliability of the system occur due to high outage frequency and duration, system overload and unsecure system or protection system. When the distribution system is reliable, it has capacity to meet the demand of customer and operate under adverse condition. Arbaminch distribution system has encountered frequent power interruption and power quality problem. The interruptions are mainly caused by system overload and short circuit fault. The reliability of the distribution system is assessed based on the data from Ethiopian Electric Power Corporation. Arbaminich substation of feeder -05 is selected as case study, which has high rate of interruption. Feeder -05 has SAIDI value of 236.8386 Hr./cust. /yr. and SAIFI of 221.6338 f/cust. /yr. The reliability indexes values of feeder -05 are not within the ranges of bench marks of reliability requirement. This thesis focused on reliability improvement of distribution system with better placement of distributed generation and network reconfiguration. Particle swarm optimization algorithm is used for placement of DG, size and network reconfiguration. The algorithm is done using MATLAB 2016 software. Based on the availability in the area, efficiency, cost and emission level, Solar and Microturbine sources are used as distributed generation. The suitable site and size of DG are found at bus 10 with suitable size 4.5 MW. For network reconfiguration sectionalizing switch is used. Before reconfiguration the switch was placed at bus 20, 21, 22,23 and 24. During network reconfiguration switch changed to bus 3, 4,12,24 and 31. The reliability indices SAFI, SAIDI and EENS value improved by 82.81%,78.89% and 78.10% respectively after DG with reconfiguration used. Expected interruption cost before applying the proposed method is 9,758,852$ /year. After the proposed method used expected interruption cost reduced to 2,995,270$ /year. This indicates that, 6,763,582 $/year is saved after using the proposed techniques
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    Reliability Enhancement and Power Loss Reduction in Distribution System by Optimal Reconfiguration (A case study of Kombolcha Distribution Network)
    (Hawassa University, 2020-10-26) DEGAREGE ANTENEH YALEW
    The purpose of power system is to provide an adequate and secured electrical supply to its customers as economical as possible with reasonable level of reliability. In distribution system, reliability and power loss are the major issues for the consumers and utility. This thesis presents a research work on the reliability assessment and optimal reconfiguration of Kombolcha radial distribution network to minimize the overall distribution losses, to enhance reliability and improve the voltage profile by using a proposed MSSO algorithm and ETAP. In the power flow analysis, the effectiveness of the proposed MSSO algorithm is conducted and compared in two cases (before reconfiguration and after reconfiguration) of Kombolcha distribution at line-3, which is severe. A modeling of electrical system elements were first developed to have a complete single line diagram of the existing network using ETAP. The reliability enhancement is measured and analysis by different reliability indices that include SAIFI, SAIDI and EENS. Reliability index values have been compared with standard benchmark values and comparison clearly indicates that Kombolcha feeder-3 distribution system is extremely unreliable. Generally, after optimal reconfiguration of the network, power loss of the system is minimized by 60%, SAIFI has been reduced by 85% as compared with the average reliability index value of the system in the base years. Similarly, SAIDI and EENS have been reduced by 86% and 70% respectively.
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    PERFORMANCE ANALYSIS OF HYBRID OPTICAL FIBER/FSO COMMUNICATION SYSTEM USING ADVANCED MODULATIONS
    (Hawassa University, 2021-04-21) FISEHA ZELALEM
    Due to its lower attenuation and high bandwidth, current telecommunication infrastructure uses optical fibers for high data long haul transmission. Free space optics (FSO) technology is a good option for short-distance multi-gigabits per second or beyond data transmission. Nowadays, it has different application areas such as indoor, outdoor, underwater, and deep-space communications. A key area within this new generation is the combination of optical fiber and FSO network to provide high bandwidth for both long and short-distance services. The hybrid link uses coherent optical advanced modulation and dispersion compensation techniques to achieve the best performance with the existence of atmospheric turbulence effect and fiber limitations. Orthogonal frequency division multiplexing (OFDM) and dual-polarization quadrature phase-shift keying (DP-QPSK) are considered promising technologies to satisfy the demand for bandwidth expansion in broadband services. OFDM can overwhelm optical fiber limitations such as polarization mode dispersion (PMD) and chromatic dispersion (CD), whereas DP-QPSK provides good noise immunity. This thesis concentrates on designing, simulation, and performance analysis of 100Gbits/s data rate hybrid optical fiber/FSO systems using coherent optical OFDM and DP-QPSK modulation techniques. MATLAB software and OptiSystem simulation tool are used to design and simulate the hybrid system. To study the performance of the systems and the quality of the signals the bit error rate and the Q-factor are considered. As a result, for 100Gbits/s per channel with DP-QPSK based system, the link coverage is up to 468m in FSO and 202km by fiber cable; and up to 510m FSO link and 220km by fiber optics for CO-OFDM system. It is observed that the CO-OFDM system has high tolerance against linear signal distortion effects and sensitive to nonlinear effects which affects the system performance
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    RESOURCE POTENTIAL ASSESSMENT AND OPTIMAL DESIGN OF PV/WIND/BATTERY/ DEISEL GENERATOR BACK-UP HYBRID ENERGY SYSTEM FOR REMOTE AREAS
    (Hawassa University, 2016-10-22) MESFIN JARISO
    Off grid hybrid systems have been attracting to supply electricity to rural areas in all aspects like, reliability, sustainability and environmental protections, especially for communities living far in areas where grid extension is not appropriate. Hybrid renewable set-up indicates that combinations based on the renewable sources could be applied simultaneously to supply energy in the form employed in an off-gird supporting with battery storage and diesel generator as backup systems. In this thesis photovoltaic-wind turbine-battery bank and diesel generator have been optimally sized, simulated and optimized for the rural community of Addis Boder village in the southern regional State, Ethiopia. Primary load demand of 142KWh/day, peak load of 26kW, deferrable energy is about 27kWh/day, and deferrable peak load of 3.6kW was involved during optimization of the power system. Well known HOMER modeling tool have been used to design the off-grid system. Solar and Wind energy are considered as primary sources to supply electricity directly to the load and to charge battery bank when excess generation is happened however in peak demand times diesel generator could also be engaged. Regarding solar energy potential there is no accurately recorded solar radiation database in the country, instead only sunshine hour data was available. Empirical formulas are used to estimate the solar radiation from available sunshine duration data. This result is compared with the data collected from NASA and it is found to be nearly the same. Consequently, for this study the calculated solar radiation is used for modeling the hybrid system. During the design of this power system set-up, the simulation and optimization was done based on the electricity load, climatic data sources, economics of the power components and other parameters in which the NPC has to be minimized to select an economic feasible power system. The results obtained from the software give numerous alternatives feasible hybrid systems with different levels of renewable resources penetration which their choice is restricted by changing the net present cost of each set up Power schemes with less NPC, less COE, higher renewable fraction, less capacity shortage, smaller excess electricity and minimum fuel consumption would be suggested as optimum system. It is concluded that besides electricity provisions, the role of a standalone hybrid system in protecting the environment from degradation, the improvement of life of people living in rural area, development of clean energy, and the future situation regarding fossil fuel sources should be taken in to account. Taking these issues into account the free solar and wind energy of the country should be utilized to improve the quality of life of the communities living in rural areas
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    Performance Analysis of High Speed Fiber Optic Communication Systems with Optical OFDM and Dispersion Compensation Technique
    (Hawassa University, 2022-04-20) GIRMA HASENA HINSENE
    Several designers are employing fiber optics instead of copper wire to transport information between data ports to fulfill the high-speed requirements of today's communication systems since it offers several advantages such as high transmission capacity and low losses. Limitations and flaws such as chromatic dispersion hamper the performance of optical fiber communication systems. Tolerating the effects of chromatic dispersion in optical communication systems, various classic dispersion compensation techniques such as Dispersion Compensation Fiber (DCF) and Fiber Bragg Grating (FBG) have been used. Advanced modulation schemes, such as orthogonal frequency division multiplexing (OFDM), are excellent candidates for improving spectrum efficiency in communication systems by reducing chromatic dispersion effects. That is FBG uses the principle of recompression of light signals with different wavelengths to reduce the effect of chromatic dispersion. And OFDM uses the orthogonality principle between subcarriers with the insertion of cyclic prefix and guard bands to reduce the effect of chromatic dispersion. The performance of a high-speed optical fiber communication system was investigated using coherent optical OFDM (Co-O-OFDM) and Fiber Bragg grating (FBG) as dispersion compensation techniques in this thesis study. The system models were simulated using Optisystem simulation software, and the output was plotted using MATLAB. Performance measuring metrics such as optical signal to noise ratio (OSNR), bit error rate (BER) and Quality-factor were used to thoroughly examine the results. RF spectrum, optical spectrum, and constellation diagram of the signal were examined at different distances to see the effect of chromatic dispersion. The performance of both DP-16QAM Co-O-OFDM and FBG integrated DP-16QAM Co-O-OFDM systems declined as the signal propagated long distances of fiber optic for four different rates due effect of chromatic dispersion, and FBG integrated DP-16QAM Co-O-OFDM system performed better for the same rate and distance due to integration of FBG.