6. Basic Framework and Operating Principle of Wide-Area Damping Control

With the technical development and cost reduction of power electronics, more and more FACTS devices are being applied into power system especially into modern power system toward smart grid [1‐3]. FACTS devices can conveniently adjust network parameters (e.g., reactance) flexibly and benefit power flow optimization, transmitted power increase, bus voltage stability enhancement, and so on. At the same time, with more and more application of synchronized phasor measurement (PMU) technology, WAMS technology are being applied into power system, which is also one obvious technical feature of the coming smart grid [4‐6]. Therefore, it would be wonderful to construct WAMS-based FACTS supplementary wide-area damping control strategy, that combines the quick and flexible control ability of FACTS devices and the global monitoring ability of WAMS, to prevent the low-frequency oscillation (especial the inter-area oscillation) and enhance the global stability of power system.