Power Systems & Energy Engineering

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/72

Browse

Search Results

Now showing 1 - 6 of 6
  • No Thumbnail Available
    Item
    IDENTIFICATION, CLASSIFICATION AND MITIGATION OF POWER QUALITY ISSUES IN DISTRIBUTION NETWORK USING STOCKWELL TRANSFORM AND DISTRIBUTION STATIC COMPENSATOR
    (Hawassa University, 2022-10-16) EPAPHROS MENGISTU
    Power quality has become a crucial concern recently due to the increase of the consumption of electrical load and the increment in the use of sensitive devices connected to power systems. In spite of that, complexity in modern daily life and the increased usage of semiconductors make non linear load a real threat to power quality level. In order that maintain power quality and to ensure its reliability, power quality disturbances must be identified and classified correctly and precisely. Thus, identification algorithms support decision makers to identified and mitigate the disturbance, and protect the power network from a high level of financial loss. In this thesis study identification, classification and mitigation of power quality issues in Awada industry zone. The measured voltage and current harmonic distortion levels are compared with the IEEE 519-2014 and IEC 61000-2-2 / -3-4 standards. The harmonic voltage distortion level in the factory has found to be well under the limits set by these standards while the current harmonic distortion levels on one of the transformer among four transform exceeds the limits with a maximum percentage total harmonic distortion current value of up to 23.09%. First, an identification process covering the most important and common power quality issues for further analyzed and discussed. Then after, most of the powerful processing algorithms in addition to support vector machine technique was investigated and their results are discussed. SVM then classify complex data and enhancing the evaluation process. This method achieved a sufficient detection algorithm, which overcame the Wavelet, Fourier and Hilbert limitations and resulted in an overall accuracy of 91.08%, 88.91% and 86.8% respectively. This resulted in a substantial improvement in terms of overall accuracy, with more than 97.1% when using Stockwell transform. In addition to the average classification accuracy, other common performance measures computed from the confusion matrix also presented and highest average accuracy of SVM is 98.3%. For mitigating, the current harmonic distortion level in the industry a D-STATCOM in current control mode is designed. The performance of the D-STATCOM is evaluated by simulating the distribution network with and without D-STATCOM. The simulation results show that the source current becomes pure sinusoidal and in-phase with the source voltage within 0.02 second and THDI reduced to 4.36% after the enabled of the D-STATCOM in the system.
  • No Thumbnail Available
    Item
    REACTIVE POWER COMPENSATION AND LOAD FREQUENCY CONTROL OF GRID CONNECTED MICRO GRID SYSTEM USING STATIC VAR COMPENSATOR (CASE STUDY: DILLA SUBSTATION
    (Hawassa University, 2021-03-15) Kumilachew chane
    n the modern power system, reactive power compensation and load frequency control are two of the main issues. The aim of this thesis is to study reactive power compensation and load frequency control of the grid-connected micro grid system (GCMG) under variable load .In this work, an Artificial Neural Network based Static VAR compensator (ANN-SVC) and Load Frequency Controller (LFC) will be proposed for reactive power compensation and load frequency control of the grid-connected micro grid system, The artificial neural network (ANN) is used to control the the SVC gete signal for proper controlling of the thyristor valve in the circulated system current management. Power system Planning and management provide the strategy for reactive power compensation and load frequency disturbance control. The ANN-controlled SVC is used for managing and compensating of reactive power in the system and LFCis control the system load frequency disturbance and the LFC controlling loop component is control and managed by ANN signal for proper controlling of the load frequency error. The real and reactive powers before applying the SVC at the peak load conditions are 40.56MW and 27.16MVAr, respectively, before reactive power compensation. During contingency conditions, the real and reactive powers are 36.03MW and 30.42MVAr, respectively, and the frequency is highly disturbed for a fraction of a second, but after compensation, the real power is improved to 50.54MW, while the reactive power is reduced to 17.34MVAr. Therefore, real power is improved by 52.18% while reactive power is compensated by 87.02%. The steady-state load frequency error is reduced by 95%, while the system power factor is improved by 94%. A detailed comparative analysis of the proposed ANN-based SVC with the fuzzy-based and multi-objective fire fly (MOFA) algorithm SVC is presented, which shows that the ANN-based SVC has better performance, fast and accuracy, in case of the above justification ANN is more prifereble than MOFA and FUZZY algorithem. The general GCMG structure with the compensation and controlling process was designed by ETAP and MATLAB/Simulin
  • No Thumbnail Available
    Item
    IMPACT OF DISTRIBUTED GENERATION ON DISTRIBUTION NETWORK PROTECTION SCHEME AND ADAPTIVE PROTECTION COORDINATION USING HARRIS’ HAWKS OPTIMIZATION
    (Hawassa University, 2022-07-26) ABENEZER KASSA USAMO
    The Modern Power System which has grown both in size and complexity, that means requires fast, accurate and reliable Protective schemes for protecting major equipment’s and to maintain system stability and reliability. Distribution networks are evolving into active meshed networks with bidirectional power flow as the penetration of distributed generation (DG) sources is increasing. Interconnecting DG to an existing distribution system provides various benefits to several entities as for example the owner, utility, and the final user. DG provides an enhanced power quality, higher reliability of the distribution system and can peak shaves and fill valleys. Penetration of a DG into an existing distribution system has many impacts on the system, with the power system protection being one of the major issues. This necessitates the use of directional relaying schemes in these emerging active distribution networks. However, conventional directional overcurrent (OC) protection will not be adequate to protect these networks against the stochastic nature of DGs and the changing network architectures. Hence, this study proposes an adaptive directional overcurrent relay algorithm that determines optimal protection settings according to varying fault currents and paths induced by the DGs in active meshed distribution networks. Location and technology of the DG sources are changed to study the effect that these changes may have on the coordination of protective directional over-current relays (DOCR). Results are compared to that of the normal case to investigate the impact of the DG on the short circuit currents flowing through different branches of the network to deduce the effect on protective devices. This study presents an adaptive protection coordination scheme for optimal coordination of DOCRs in interconnected power networks with the impact of DG. The used coordination technique is the Harris Hawks Optimization (HHO), selected due to adaptive & time-varying parameters allows HHO to handle difficulties of search including local optimal solution, multi modality & deceptive optima. Adaptive relaying describes protection schemes that adjust settings and/or logic of operations based on the prevailing conditions of the system. These adjustments can help to avoid relay miss-operation. Adjustments could include, but are not limited to, the logging of data for post-mortem analysis, communication throughout the system, as well changing relay parameters. Several concepts will be discussed, one of which will be implemented to prove the value of the new tools available. The optimal coordination of DOCR is find by with MATLAB code using HHO technique and the adaptive protection scheme model will develop in DIgSILENT/Power Factory. The results validate the ability of the proposed protection scheme to capture the uncertainties of the DGs and determine optimal protection settings, while ensuring minimal operating time
  • No Thumbnail Available
    Item
    Assessment & Allocation of Transmission Losses & Costs under N-1 Contingency Condition
    (Hawassa University, 2016-10-12) Rahel Dawit
    Traditionally electricity supply industry (ESI) was monopolistic in nature with generation; transmission and distribution owned by government. Now in all over the world electricity market is restructured. All the three major areas i.e. generation, transmission and distribution are now working as separate companies namely Generating Companies (GENCO), Transmission Companies (TRANSCO) and Distribution Companies (DISCOMs). Under this environment the question of loss allocation is also very much important because no one want to bear this loss. Contingency conditions are normal practices in real power system and this brings transmission reliability margin into the picture. Further under contingency the value of losses in certain lines is increased due to extra flows in these lines. Hence transmission loss assessments, allocation and pricing with consideration of contingency are significant issues in restructured electricity market. Due to this reason a methodology for transmission loss assessment, allocation and pricing with consideration of N-1 contingent maximum flow condition has been developed. For finding contingent loss novel reliability factors is introduced. By using this factor optimal losses are calculated. After calculating these losses by using Bialek’s tracing these losses are allocated to generators and loads. After that by using MW-cost methodology transmission loss cost is allocated to the generators and demands. Sample 6 bus and IEEE 14 bus system are used for showing the feasibility of this method
  • No Thumbnail Available
    Item
    CUSTOMIZED INTERLINE POWER FLOW CONTROLLER FOR VOLTAGE PROFILE IMPROVEMENT AND POWER LOSS MINIMIZATION OF TRANSMISSION LINE (CASE STUDY: SOUTHERN REGION FROM SHASHEMENE TO BUKULUGUMA TRANSMISSION SYSTEM)
    (Hawassa University, 2024-10-03) ASRAT LEMMA
    An electrical system is a collection of components that are used to supply, transmit, and consume electricity. Transmission lines effectively transfer the electricity produced by different power plants. Nevertheless, the generated electricity is not entirely supplied to customers because of voltage drop and power loss. Uncontrolled bus voltage profile caused problems for industries that were developing quickly. Interline power flow controller (IPFC) is a type of flexible AC transmission system (FACTs) devices applicable to reduce power loss and enhance voltage profiles of the transmission networks from Shashemene to Bukuluguma transmission system. Load flow analysis on nine buses were performed by Newton Raphson load flow analysis technique using MATLAB R2016a. The analysis showed that out of nine buses four buses are out of voltage limit. On the system as a whole, there has been a loss of 8% real power and 10.42% MVAr reactive power, or 7.322MW and 4.530 MVAr, respectively. To minimize the loss problems, grey wolf optimization (GWO) techniques were proposed to search optimal place and size of interline power flow controller (IPFC), placed on bus 5, and sized 27MVAr. GWO techniques are compared with Antlion optimization, but GWO gives a good performance. After analysis data 4 buses bus number 4, 7, 8, and 9 are out of permissible values, the remaining buses are within acceptable limits. GWO techniques suggest implementing the lowest voltage stability index bus. After installing IPFC in optimal power flow place the network problem is improved by GWO 6.1% and ALO 3.9%, the lowest case voltage profile improved from 0.937pu to 0.978pu and 59.7% of active power and 40% of reactive power are saved. Finally, the reduction result suggest that the recommended approach is operative to regulate all buses voltage magnitudes within the NEC and IEEE permissible boundary and to minimize power loss considerably
  • No Thumbnail Available
    Item
    ENHANCING THE RELIABILITY OF DISTRIBUTION SYSTEM THROUGH RENEWABLE ENERGY RESOURCES
    (Hawassa University, 2024-04-12) FIRAOL KASAHUN MENGESHA
    The distribution system connects high-voltage transmission networks with end-users. Most of the time, power plants are situated distant from the consumer's location, resulting in large power losses in both the distribution and transmission systems, However, distribution system losses are typically greater than transmission line side losses. The main objective of this study is to reduce power losses and enhance system reliability using Distributed Generation (DG) in the case of the Guder Substation. The Guder Substation has three feeder lines that provide energy for different customers. From these feeders, the Guder town feeder has been chosen since it is frequently interrupted. The chosen feeder has been modeled in ETAP software, and simulation results have been obtained with both ETAP and MATLAB software. The results show that the feeder has a power loss of 611.9843 KW and 323.8237 kVar active and reactive, respectively. Additionally, the study investigates the existing reliability indices of SAIFI, SAIDI, and EENS, which have values of 303.7458 f/cust.yr, 306.4240 hr/cust.yr, and 2368.307 MWhr/yr, respectively. Particle Swarm Optimization algorithm has been suggested to decide the best size and position of DG. After renewable Distributed Generation penetrated the network, the real and reactive power loss reduced from 611.9843 KW and 323.8237 kVar to 302.75 KW and 132.34 kVar, respectively. Additionally, the SAIFI, SAIDI, and EENS system reliability indices were enhanced from 303.7458 f/cust.yr, 306.4240 hr/cust.yr, and 2368.307 MWhr/yr to 27.4968 f/cust.yr, 13.650 hr/cust.yr, and 111.758 MWh/yr, respectively. Finally, reliability indices and line losses before and after Distributed Generations penetrated the network are compared. In general, the simulation results indicate that the suggested method is efficient in maintaining system reliability and minimizing power losses