Flexible AC Transmission Systems (FACTS) and power system security — A valuation framework

Considering aging power system infrastructures in conjunction with increased electricity trading activities, there is a strong need for future investments in electricity grids. Technological progress has made available a number of different investment alternatives, ranging e.g. from “standard” reinforcements of existing transmission capacities to the installation of Flexible AC Transmission Systems (FACTS). This paper proposes a framework for comparing different investment alternatives. The approach relies on an optimal power flow (OPF), where system security is explicitly considered by means of a novel formulation for a security constrained optimal power flow (SC-OPF). For evaluation purposes several indicators are proposed, such as the loading of transmission lines, the total generation costs and the overall dispatch depending on different consumption levels. In a first case study the installation of shunt and in-series FACTS devices are compared. The paper is concluded with a sample valuation assessing whether to invest in a Thyristor-Controlled Series Capacitor (TCSC) or in a line reinforcement, i.e. additional line capacity.