Static Synchronous Compensator (STATCOM), sometimes denoted as an 'Advanced Static VAr Compensator', is a Flexible Alternating Current Transmission System (FACTS) device connected in parallel with a power system that is capable to exchange reactive power with the system in both directions. The terms 'compensator' and 'synchronous' indicate that the device is equivalent to an ideal synchronous generator, which produces a set of three‐phase fundamental frequency sinusoidal voltages. The STATCOM device is mainly used for dynamic compensation in power systems, it can provide fast (dynamic) voltage support and might also be used for transient stability margin enhancement or oscillation damping improvement. The STATCOM consists of a voltage‐sourced converter (VSC), a magnetic circuit (MC), a shunt coupling transformer, a shunt breaker, and a control and protection unit. In a VSC, a number of square wave voltages are generated at fundamental frequency by operating the controllable semiconductor switches once per cycle of the fundamental frequency.

STATCOM (Static Synchronous Compensator, also known as SVG). It is an important device for Flexible AC Transmission System (FACTS), which is the third generation of dynamic VAR compensation device after FC, MCR, and TCR type of SVC (Static VAR Compensator). Its appearance represents the application of most advanced technology for dynamic VAR compensation. It is also known as DSTATCOM when apply in power distribution. STATCOM is connected parallel in power grid and works as reactive current source. Its reactive current can be flexibly controlled and compensate reactive power for system automatically. It solves problem of harmonics interfere switching parallel capacitor banks. In another hand, it can restrain harmonics and improve power quality according to customers’ needs. STATCOM has superior performance in lots of aspect such as responding speed, stabilize voltage of power grid, reduce system power loss and harmonics, increase both transmission capacity and limit for transient voltage. It also has advantage of smaller in dimension.