Dynamic modelling of a unified power flow controller

A method to regulate the unified power flow controller (UPFC) to improve the dynamic performance of power systems is proposed in the paper. The series voltage responds to the power variations of the transmission line, while the shunt compensation is controlled to maintain the power system bus voltage and to stabilise the DC link of the UPFC. Decoupled control algorithms for active and reactive power are developed. A nonlinear dynamic model of the power network is established for transient studies. The small-signal model is derived using linearisation and network reduction. An integrated formulation can be achieved which represents the dynamics of the generators, loads and the UPFC. The effectiveness of the UPFC and the accuracy of the analytical models are examined using numerical examples