Author : Peetla Koteshewarrao 1
Date of Publication :12th December 2018
Abstract: Flexible AC Transmission Systems (FACTS) technology is the most advanced tool for power flow control in electric network. Unified Power Flow Controller (UPFC) is the most versatile FACTS device for optimization and control of power flow in transmission system. It is a voltage source converter based FACTS controller for series and shunt compensation of the line which controls the real and reactive power independently. In this paper an attempt has been made to investigate the transient stability enhancement of system using UPFC controller. UPFC modeling has been done by measuring the parameters locally at the bus. The proposed controller is found to be suitable for operating in both voltage regulation and PQ mode. To mitigate the power oscillations in the system, the required amount of series voltage injected by UPFC controller has also been computed. It is also found that the proposed controller works effectively under low as well as high range of power rating of generator. The objective of this paper is to answer to the following question: How the unified power flow controller (UPFC) parameters should be controlled in order to achieve the maximal desired effect in solving first swing stability problem. This problem appears for bulky power systems with long transmission lines. Various methods of reference identification of the series part, in order to improve the transient stability of the system based on: optimal parameters, state variables and also injection models were studied. Finally, a new identification method based on state variables and using the local measurement was proposed. The controller have been designed and tested for controlling the real and reactive power flow of UPFC. Computer simulation by MATLAB/SIMULINK has been used to verify proposed control strategies.
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