Steady-state optimization in power systems with series FACTS devices

This paper presents an optimization-based methodology to identify key locations in the AC network where placement of a series-connected FACTS device increases the maximum megawatt power transfer the most. The models used for the thyristor-controlled series capacitor (TCSC) and unified power-flow controller (UPFC) include the nonlinear constraints of voltage limitation, zero megawatt active-power exchange, voltage control, and reactive-power exchange. This article describes briefly the steady-state flexible AC transmission systems (FACTS) models and their integration in an existing optimal power-flow (OPF) software package designed and implemented by the authors. A reduced real-life network is used for the case studies. The optimization results help in evaluating the effectiveness of the series FACTS devices in maximizing the network transfer capability and deliver a measure of the FACTS ratings.