In this paper, the nearly instantaneous response of the series-connected VSC-based FACTS controllers when used to limit possible fault currents in a compensated line, will be presented. The effectiveness of both FACTS controllers (SSSC and UPFC) towards this system condition was investigated exploring the series voltage effect upon the line. Moreover, it will be shown that the UPFC shunt converter can also contribute to the reduction of such fault currents. The short-circuit current limitation strategy presented herein showed that aside of the power flow control and voltage support commonly carried out by the SSSC and the UPFC, they could also perform this additional functionality, thus offering a useful tool for the protection of the line in which these devices are installed.

In this paper, the operational analysis and the main limitations of the VSI-based multi-line FACTS controllers, namely: the GIPFC (Generalized Interline Power Flow Controller) and the IPFC (Interline Power Flow Controller), are analyzed. The GIPFC & IPFC are amongst the newest devices within the FACTS technology. By utilizing these devices an enhanced and nearly instantaneous controllability over independent transmission systems, can be obtained. The steady-state analysis of a GIPFC & IPFC controlling two balanced independent AC systems, is initially modeled. The use of the instantaneous power theory along with the d-q orthogonal co-ordinates showed to be appropriate tools for assessing the GIPFC response towards the operation of both controlled systems. Yet, to observe its dynamic behavior and simultaneously validate the previous steady-state analysis, a phase-shift VSI-based GIPFC was implemented in the ATP program. Where applicable, a comparative evaluation between the GIPFC and the IPFC, is also presented.