- Flexible AC Transmission Systems (FACTS) refers to a group of resources used to overcome certain limitations in the static and dynamic transmission capacity of AC electrical networks. Some are associated with standard or ideal AC grid networks that comprise constant voltage and frequency, sinusoidal voltage and current waveform, and a power factor. Most of the existing power transmission networks are AC networks and in general, FACTS are defined as or refer to alternating current transmission systems which incorporate power electronic-based and other static controllers to enhance both the AC grid controllability and the power transfer capability.
- Sometimes ac power networks face power quality issues such as spikes harmonic, notches, noise, voltage sags, or swelling among others. These problems may be caused by rush low switching lighting, short circuits among other causes and they lead to disturbances of one of the features of the ac grid but these flexible transmission systems can be very beneficial considering that they increase the reliability of AC grids reduce power transmission outages and delivery costs and improve the power transmissions quality and efficiency by reducing losses the supply inductive or capacitive reactive power of the AC network allows the improvement of the transmission quality and the efficiency of the power transmission system.
- FACTS devices can be connected in parallel, series, or by a phase-shifting connection to the grid lines. Their first-generation devices were based on mechanical switching either in parallel or in series or by a phase shift in connection. These were followed by a transmission system based on a partially controlled power semiconductor device.
- Thyristors semiconductors are characterized by an active turn on but a passive turn off and are faster and more robust when compared to first-generation FACTS.
- The latest generation FACTS devices are base on fully controlled power semiconductor devices IGBTSs. These are characterized by both an active turn on and turn off and considering that they can also work and fasts switching. They provide much better performance. STATCOM, SSSC, and UPFC are the representatives of the latest technology effects.
