Electrical Computer Engineering
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Item ASSESSMENT AND ENHANCEMENT OF THE TRANSIENT STABILITY OF DFIG BASED WIND FARM USING ANFIS (A Case Study of ADAMA II Wind Farm)(Hawassa University, 2021-12-18) TESFAYE BELAYWind power is the greatest existing and used form of renewable energy in the world. Mixing the different wind farms to the national grid introduces new challenges regarding power system stability, among power system stability concerns; transient stability is one that significantly affects the grid. The objective is to assess and enhance the transient stability of DFIG based on wind farms, to model PI control for speed and slip control generator, to improve transient stability using thyristor control series capacitor (TCSC), to conduct during pre-fault, during fault, and post fault conditions. The methods to gathering data are through review of different papers, by asking the site workers, preparing questions for the worker, and from nameplates of equipment. The result consists of four conditions, the first condition is pre-fault conditions, the systems have no disturbance, the second condition is during a fault condition, all systems are disturbed, the third condition is posted fault conditions in this systems have no disorder and the fourth is the improvement of the systems by using TCSC, TCSC is injecting reactive power to the fault area and remove the fault from the systems or back to normal operations. Generally, stability has contained three scenarios pre-fault, during the fault, and post-fault condition. In Matlab Simulink, the pre-fault and post-fault have no disturbance, but during fault conditions, the systems disturbed and the disturbed systems are solved by TCSC at the improved conditions of the systems.Item ENHANCING LOW VOLTAGE RIDE THROUGH CAPABILITY OF DFIG BASED WIND TURBINE: A CASE STUDY OF ADAMA-II WIND TURBINE(Hawassa University, 2019-08-18) FSAHA MEBRAHTUDoubly fed induction generators (DFIG) based wind turbines (WT) are major sources of energy generation around the world. One of such energy source is wind generation, which is very much popular now days. It utilizes doubly fed induction generator (DFIG) to generate electricity in generation mode. But sometimes wind turbines are disconnected from the power system in the event of grid faults. To avoid grid instability as well as to ensure the secure and reliable operation of the power systems, all wind turbines must stay connected with the grid during faults and capable to ensure the operation of the utility grid side during voltage sags in the event of a fault that is performed by analyzing the low voltage ride through (LVRT) capability of DFIG based wind turbines.. DFIG is very sensitive to any grid disturbances, if a severe voltage dip occurred due to grid fault, high currents will pass through stator and rotor windings and also a very high DC voltage would be induced in converter circuit, which may lead to damage the converter circuit and the DFIG windings. A crowbar protections system is essential to avoid the disconnection of the doubly fed induction wind generators from the network during faults and to protect the DFIG from the dangerous effects of the electrical fault. Accordingly, Ethiopia have been started to expand its energy generation by installing renewable energy source like wind farm. Presently, Ethiopia has installed wind farms like Ashegoda, Adama-I and Adama-II. The Adama-II wind farm project has 153 MW with 102 units, each of with generation capacity of 1.5 MW. This work focused on the improvement of low voltage ride through capability (LVRT) of Adama-II wind turbines. In this thesis a crowbar protection system is used to improve the power system fault ride through capability of DFIG of Adama-II. During the symmetrical fault using crowbar protection the value of crowbar current at time three 3 seconds is overshoot to 3000 A and it will reduce to the original condition after 100 ms. Also the value of stator voltage, stator flux during faulty and symmetrical conditions before the fault and after are the same, but during the voltage dip the stator flux is decreased and the stator voltage is also reduced. The dynamic behavior of DFIG under normal and various grid fault conditions are simulated and analyzed to provide the recommendations. MATLAB/Simulink software is utilized for the development of proposed systemItem TRANSIENT STABILITY IMPROVEMENT OF DOUBLY FED INDUCTION GENERATOR-BASED VARIABLE SPEED WIND ENERGY CONVERSION SYSTEM USING FLSTATCOM(Hawassa University, 2023-10-21) ELIAS EJIGUThe "doubly fed induction generator (DFIG)" is the most extensively utilized technology for wind power generation because of its adaptability to changing wind speeds and ability to capture more wind energy. However, issues like transient stability posed hurdles for the grid because wind energy has a fluctuating nature, faults, load fluctuations occur, and electronic devices are required to connect wind turbine generators to the grid. Capacitor banks are used in the research region to address the aforementioned issues and improve the variable-speed wind production system's transient stability. The investigation shows that the capacitor banks are incapable of maintaining the grid code during any kind of network fault. This demonstrates how crucial it is to use FACTS devices to increase the wind-generating system's transient stability. In this dissertation, a shunt flexible alternative current transmission system device called a static synchronous compensator (STATCOM) can offer technical solutions to enhance the overall performance of wind energy conversion systems through the creation of a suitable controller. The Thesis also presents the STATCOM control system and its effectiveness. ANFIS-controlled STATCOM is examined in this Thesis before being compared to that of STATCOM controlled by fuzzy logic. The adaptive ANFIS control approach is faster to speed control, better at responding to voltage fluctuations, and better at tracking the reactive current reference, according to simulations performed using MATLAB on grid-connected DFIG systems. Finally, the ANFIS based STATCOM is critical in assuring the stability of power systems in the case of large disruptions and break down