Browsing by Author "Tamene Adugna"

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    Comparative Studies of FACTS Devices for Power Loss Reduction and Voltage Profile Improvement in Radial Distribution Systems (Case Study: Sebbata-I Substation Outgoing Feeder)
    (Addis Ababa University, 2023-07) Tamene Adugna; Singh N.P. (Prof.)
    The power quality of any radial distribution system is determined in terms of voltage profile and power loss level of the system. The FACTS controllers can improve the performance of power transfer capability through controlling of the parameters of the distribution system. This thesis carries out comparative studies and performance analysis of DSTATCOM, SVC and UPQC devices in improving the performance of a radial distribution system. Sabbata-I substation 15 kV outgoing feeder-12 radial distribution network is considered to be a test system to evaluate the effectiveness of these devices. The location for placement of DSTATCOM, SVC and UPQC devices is determined by selecting the buses with higher values of loss sensitivity index which is calculated using MATLAB software. The size of these FACTS devices for each of the candidate buses are decided by using Particle Swarm Optimization (PSO) method. The effectiveness of each of these devices in improving the voltage profile and reducing the power loss under 75%, 100% and 125% of full load condition is evaluated through simulation studies. From the load flow analysis under normal operating conditions bus numbers 83, 36, 33, 81 and 54 are identified as weak buses for the integration of FACTS controllers. The simulation output reveal with installation of DSTATCOM device, the distribution system voltage profile enhanced by 1.86%, 2.97% and 4.18% under the respective loading conditions as compared to those of the system without installation of these devices. It is further observed that installation of SVC device improves the voltage profile by 1.65%, 1.75% and 1.86% while installation of UPQC device results in voltage profile improvement by 2.86%, 4.15% and 5.54% under the same loading conditions. It is also found that with installation of DSTATCOM device, reduction of the real power loss is 48.06%, 49.49% & 50.92% while installation of SVC device results in active power loss reduction by 34.45%, 33.51% and 31.02% under respective loading conditions. It is further observed that with installation of UPQC device, the real line loss is reduced by 64.85%, 65.72% and 66.61% under the same loading conditions. It is also found that with installation of DSTACOM device, the reactive power loss is reduced by 46.22%, 47.70% and 49.19% respective loading conditions. The simulation results further reveal that installation of SVC device results in reduction of reactive power loss by 35.91%, 34.45% and 31.70% while by using UPQC device the corresponding reactive power loss reduction is 64.13%, 65.02% and 65.93% under the respective loading conditions. The cost-benefit analysis reveals that installation of DSTATCOM, SVC and UPQC devices result in saving of 4,349,766.76 ETB, 2,945,561.84 ETB and 5,776,106.31 ETB respectively per annum under full load condition on account of power loss reduction. It is also found that the investment cost on account of installation of DSTATCOM, SVC and UPQC devices requires 8,780,813.64 ETB, 15,074,587.21 ETB and 11,728,658.22 ETB respectively under full load condition. It is concluded that effectiveness of UPQC device is better than those of DSTATCOM and SVC devices in regard to reducing the loss and enhancing the voltage profile of outgoing feeders under reduced, normal as well as overloaded operating conditions. Moreover, UPQC device is cost effective as compared to DSTATCOM and SVC devices. Therefore, use of UPQC device is recommended for power loss reduction and voltage profile improvement of distribution systems rather than using DSTATCOM and SVC devices.
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    Optimization of Small Hydropower in The Abbay Basin
    (Addis Ababa University, 2004-09) Tamene Adugna; Zelalem Hailu (PhD)
    Although Ethiopia possesses a huge hydropower potential, the energy problem in the country is enormous. A great majority of the population in Ethiopia are dependent on traditional resources to fulfill their energy needs. Due to the poor energy supply, the people not only have to put up with an unattractive living environment but also suffer the consequences of climatic change caused by the associated environmental impacts. Numerous villages do not get electricity supply due to the scattered nature of the settlements. Therefore, the energy policy should give enough attention to decentralized systems in which small hydropower potential plays a significant role. This study considers some of the small hydropower sites in the Abbay basin and that the selection of optimum sites or the optimum level of development at the sites can be undertaken with the application of non-linear optimization techniques. The optimization has been conducted on the basis of four theoretical small hydropower systems established in the Abbay basin. Among these four, the two systems consisted of two hydropower alternatives each and the other two consisted of three hydropower alternatives each. In this thesis, Microsoft Excel 2000 solver, which uses the Generalized Reduced Gradient(GRG2) algorithm for optimizing nonlinear problems has been used. Using this optimization technique, the level of development of each of the hydropower sites has been determined. The method can also be used to select the optimum small hydropower site(s) from a number of alternatives. Further study for optimization can be conducted on renewable hybrid systems combining a decentralized energy sources for rural electrification.