Modeling And Simulation Of Unified Power Flow Controllers

As a typical Flexible AC Transmission System(FACTS) device, a Unified Power Flow Controller can provide many function. It can control transmission line impedance, voltage magnitude and phase angle either selectively or simultaneously in appropriate combinations and can also control independently the real and reactive power flow in transmission circuit. It is the most creative and flexible controller of FACTS family.This paper analyses basic principle of UPFC and its controlling function, and complete its mathematical modeling by considering the dynamic effect of capacitor. The model of UPFC in this paper uses a PID controller and its control system adopts a decoupled strategy. Using MATLAB, this paper realizes the power flow analyses and power system transient stability computation. The simulation results of power flow indicate that UPFC has strong control capability of power flow and voltage. And the computation of the latter proves that UPFC can improve the system stability. Through a large number of simulations this paper gets the power flow changing-chart of the shunt transmission line when changing the control target of UPFC. By optimizing the parameter of PID controller with Genetic Algorithms, UPFC can improve the system stability more effectively.The research work is financially supported by doctor-point financially supported by the Education Ministry of China under the grant No. 20020359004 and the Natural Science Foundation of Anhui Province under the grant No.00104421.