The application of a global control based on the combination of the voltage, active and reactive power to investigate and fully understand the control capabilities and the impact of the UPFC in power flow regulation is presented. The models are presented and analysed in details in this paper. The effectiveness and convergence of the method proposed is tested on the 30 bus IEEE system. The results prove that the application of UPFC in electric power system is intended for the control of power flow, improvement of stability, voltage profile management, power factor correction, and loss minimisation.