Optimal controlling power flow in Transmission System by using UPFC
Controlling power flow in modern power systems can be made more flexible by the use of recent developments in power electronic and computing control technology. The Unified Power Flow Controller (UPFC) is a Flexible AC transmission system (FACTS) device that can control all the three system variables namely line reactance, magnitude and phase angle difference of voltage across the line. The UPFC provides a promising means to control power flow in modern power systems. Essentially the performance depends on proper control setting achievable through a power flow analysis program. The paper presents a reliable method to meet the requirements by developing a Newton-Raphson based load flow calculation through which control settings of UPFC can be determined for the pre-specified power flow between the lines. The proposed method keeps Newton-Raphson Load Flow (NRLF) algorithm intact and needs (little modification in the Jacobian matrix). A MATLAB program has been developed to calculate the control settings of UPFC and the power flow between the lines after the load flow is converged. Case studies have been performed on IEEE 5-bus system to show that the proposed method is effective. These studies indicate that the method maintains the basic NRLF properties such as fast computational speed, high degree of accuracy and good convergence rate.
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