Static Synchronous Compensator

A static synchronous compensator, or STATCOM, is a shunt-connected reactive compensation device used on electricity transmission networks, built from power electronics that form a voltage-source converter able to act as either a source or a sink of reactive AC power. It belongs to the flexible AC transmission system, or FACTS, family, and unlike passive reactive power devices such as capacitors and inductors, its reactive power output is variable and can change within milliseconds, letting it supply or consume both capacitive and inductive reactive power; this speed suits it to dynamic situations such as supporting the grid through a fault or contingency event, in addition to ordinary voltage support and power factor correction. Wide adoption followed the arrival of gate turn-off thyristors in the 1990s, which enabled the first commercially available STATCOMs using three-level topologies and pulse-width modulation; modern designs use insulated-gate bipolar transistors for faster high-power switching, and multi-modular converter topologies have begun replacing three-level designs to reduce harmonics and improve performance.