UPFC power flow control strategy based on exact linearization via feedback

The performance of the traditional linear controller applied to unified power flow controller (UPFC) may be deteriorated due to a large-range change of the operating condition. In order to solve this problem, a new nonlinear power flow control strategy for UPFC based on exact linearization via feedback was presented. A 5th-order UPFC nonlinear model was firstly linearized via selection of a Lyapunov-like output function, an appropriate nonlinear coordinate transformation and state variable feedback. Then pole placement was applied to the transformed linear system to design the UPFC internal controller. The simulation results on IEEE 118-bus system demonstrated that the proposed control overcomes the inherent drawback of traditional PI control, adapts to a wider range of operating conditions, and provides better performance on power system transient stability improvement than PI control. Furthermore, the design method of control strategy presented in this paper can be applied to other voltage source converter (VSC)-based FACTS devices. ©2012 Chin. Soc. for Elec. Eng.