From the perspective of the dynamic characteristics of voltage source converter(VSC)control of unified power flow controller(UPFC)

the dynamic effects of grid-connected UPFC on the system electromechanical oscillation modes are studied. Grid-connected UPFC changes the power system load flow and introduces dynamic interactions with the generators. Thus

there are two main aspects of the UPFC affecting power system electromechanical oscillation modes(EOMs). Firstly

UPFC regulates power distribution and affects the EOMs. Secondly

dynamic interactions introduced from UPFC to generators can affect the EOMs. A “closed-loop control system” type of state space model for the power system is established

where the UPFC is treated as a “power-voltage” type of multi-input and multi-output feedback controller. Based on the proposed state space model

damping torque analysis(DTA)theory is applied to the dynamic interactions introduced from UPFC to EOMs of power system. New England 10-machine example system is used to analyze the effect of flow regulation and control system dynamic characteristics of the UPFC on EOMs. Nonlinear simulation verifies the correctness of the obtained conclusions.