New FACTS controllers and how to assess them

The challenge facing the power system engineer today is to use his existing transmission facilities to greater effect. Certainly he encounters great difficulty when he asks for permission to construct new transmission lines. Equally certainly, the loading required on his system is likely to increase as demand increases, but also to change as new generators are allowed on to his system and older ones disappear. But FACTS (Flexible AC Transmission Systems) has come to help. How can these new controllers be assessed? What is their justification? How do they compare with conventional solutions? This paper discusses the constraints to power transmission, and the old and new concepts for power transfer and load flow control. The following devices are then discussed: series capacitors, the GTO SVC (STATCOM), electronic tap changing, and the unified power flow controller