STATCOM

A STATCOM or Static Compensator is a member of the FACTS family of devices used on alternating current electricity transmission networks. A STATCOM is a power electronics voltage-source converter based device that can act as either a source or sink of reactive AC power to an electricity network and if connected to a source of power can also provide active AC power.

A STATCOM works by rebuilding the incoming voltage waveform by switching back and forth from reactive to capacitive load. If it is reactive, it will supply reactive AC power. If it is capacitive, it will absorb reactive AC power. This is how it acts as a source/sink.

Usually a STATCOM is installed to support electricity networks that have a poor power factor and often poor voltage regulation. There are a number of other uses for STATCOM devices including, wind energy voltage stabilisation, and harmonic filtering. However, the most common use is for voltage stability.

A Static VAR compensator (SVC) can also be used for voltage stability. However, a STATCOM has better characteristics than a SVC. When the system voltage drops sufficiently to force the STATCOM output to its ceiling, its maximum reactive power output will not be affected by the voltage magnitude. Therefore, it exhibits constant current characteristics when the voltage is low under the limit. In contrast the SVC's reactive output is proportional to the square of the voltage magnitude. This makes the provided reactive power decrease rapidly when voltage decreases, thus reducing its stability.

References

* [http://www.risoe.dk/rispubl/VEA/veapdf/ris-r-1205.pdf Conceptual survey of Generators and Power Electronics for Wind Turbines]