Controller Research And Design Of Unified Power Flow Controller

Grid structure in China is relatively weak and the layout is unreasonable, especially in rural areas, so large-scale reform is unrealistic. FACTS technology in China has broad application prospects. Because Unified Power Flow Controller (UPFC) is one of the most powerful FACTS and it can adjust the line parameters、 bus bar node voltage and line power flow and so on, the research on UPFC is of great significance. This paper includes the power flow Calculation of UPFC、 control strategies of UPFC and its applications.This paper first introduces basic structure of UPFC and working principle, summes up all the works of UPFC, establishes UPFC’s steady-state and dynamic-state mathematical modes, etc, and derivatives the power flow calculation method on the system which includes UPFC on the basis of the previous.Two new UPFC controllers are designed by the internal model control, whose decoupling methods are diffident. One applies state feedback to decouple parallel and series sides of UPFC, which first applies the state feedback and internal mode control to decouple current loop of parallel side、current loop and voltage loop of series side. The other applies inverse system to decouple parallel and series sides of UPFC. Then With the help of Matlab/Simulink simulation platform, establishes the UPFC experimental simulation models and analyzes the simulation results under different operating modes of UPFC, and simulation results show that UPFC controllers designed in this paper are better than PI controller, and the controller designed by inverse system decoupling control is the best.Finally, this paper studies suppression system low frequency oscillation in Double-loop lines with eigenvalue analysis method in different situations. The situations are follows:the first additional damping controller’s input signal is the system oscillation frequency, the second additional damping controller’s input signal is active power of the other line, the third is the combination of the above two additional damping controllers. Additional damping system oscillation damping controller is designed with the principles of PSS.Then with the help of Matlab/Simulink, system without UPFC, system with UPFC which has no additional damping controller, system with UPFC which has additional damping controller are simulated. The simulation results show that, UPFC itself has the ability to oscillation suppression system, but its capacity is limited. Additional damping controller can improve the system damping and the combination of damping controllers is the most strongest.