The Study Of Optimizing Power System Performance By Using Optimal FACTS Devices

This research stems from the fact that today’s power systems are heavy stressed due to expansion in the transmission network have not kept pace with the increasing demand for transmission services because building of new lines is difficult for environmental as well as political reasons. Hence, enhancement the transfer capability of existing power networks to satisfy the increased power demand and ensure its secure operation has become an important issue for the Independent System Operator in the new electricity markets.Power Flow Control devices such as Flexible AC Transmission Systems (FACTS) provide the technical solutions to address the new operating challenges being presented today. Especially, Thyristor-Controlled Series Compensator (TCSC), which is one of the most effective FACTS devices, can control the power flows in the network by changing transmission lines parameters. The effect of TCSC on the network can be seen as a controllable reactance inserted in the related transmission line. Series capacitive compensation works by reducing the effective series impedance of the transmission line by canceling part of the inductive reactance. Hence the power transferred is increased. In this way, the system performance can be considerably improved by controlling the power flows without generation rescheduling or topological changes. Furthermore, the thermal limits are not violated and the stability margin is increased. In order to obtain benefits from these devices, an appropriate control is necessary. Studies that investigate the deployment of FACTS are indicated that the effectiveness of the controls for different purposes mainly depends on the location of control device. Therefore, Operators are facing the problem of where FACTS should be installed in order to achieve require goal?. Many studies have been proposed for improving existing power networks via optimal location of FACTS devices, these however studies are not able to limit search space. From the viewpoint, this thesis focuses on look at the problem of how to place and use the TCSC devices optimally to enhance of power system performance. A Min-Cut algorithm is proposed in this thesis to determine proper location of TCSC. Once the locations are determined, an optimization problem of finding the best settings for the installed TCSC is formulated and solved. The proposed method can identify the weakest location of the system and therefore helps the System Operators to operate the system in a more secure and sufficient way. With this method search space and the number of branches which need to be investigated to determine the position of TCSC for optimizing of power system performance will be significantly decreased. The focus of this work is to optimize power system performance by the optimal placement of TCSC devices and their settings. Particularly, it is intended to improve the power system transfer capability by resolving congestions, and the performance of the power system considering steady state operating condition as well as the system subjected to small disturbances. The power system performance in this thesis is evaluated via solution problem concern in Security Constrained Optimal Power Flow, Enhancing Total Transfer Capability of Power System, Transmission Congestion Management and Maximum Loadability. The detailed contents of the research are clearly presented in chapter2to chapter7of the dissertation, the tenor of the dissertation are summarized as follows:1. The modeling power network using Min cut algorithm and procedure for determining the minimum cut of example power system is described in detail. The concept of bottleneck of power system and proper location of TCSC is discussed. In addition, some important issues about the transmission sector in the deregulated environment and the impact of transmission congestion and the required features of a suitable approach for resolving transmission congestion are also introduced.2. Min cut algorithm is applied to determine proper location of TCSC. The problem of security constraints in optimal power flow under normal and network contingencies via optimal location of TCSC is researched. An Optimal Power Flow problem is formulated to determine the optimal settings for TCSC with the objective to obtain economic benefit and ensure steady-state security in power system operation.3. The problem of total transfer capacity (TTC) enhancement of transmission system is described. A procedure for evaluating power transfer capability with TCSC and without TCSC is developed.4. An index called the benefit index, which is used to decide proper location of TCSC in transmission congestion management, is presented. This index is formed from the difference between the minimum generation cost with and without TCSC. It is calculated for each location of TCSC and used to evaluate the suitability of a given branch for placing a TCSC. The branch that gives a maximum benefit index is the main proper location of TCSC.5. Kirchhoffs law of current and criteria for optimal location of TCSC are presented for determining the best setting of TCSC devices with the aim to obtain maximum system loadability and optimal cost of installation of these devices. From simulation results show that, the proposed method is capable of finding the location, quantity and size of TCSC in such effective way for enhancing system loadability and minimum installation cost of TCSC devices.Simulation results throughout this research show a significant improvement of the power system performance after the TCSC devices is optimized. The main contributions of this thesis are1. A Min cut algorithm is applied in power system to determine proper location of TCSC.2. An Optimal Power Flow problem is formulated to determine the optimal settings for TCSC with the objective to obtain economic benefit and steady-state security in power system operation.3. A benefit index is used to decide proper location of TCSC in transmission congestion management.4. A formulation for determining the best setting of TCSC devices is carried out to obtain maximum system loadability and optimal cost of installation of this devices.5. An Optimal Power Flow problem is formulated in order to determine the optimal settings of TCSC in power system with the aim to ensure that the system would be transiently stable following the fault disturbances.