Static synchronous compensator

A static synchronous compensator (STATCOM), originally known as a static synchronous condenser (STATCON),[1] is a regulating device shunt-connected[2] to alternating current electricity transmission network. It is based on a power electronics voltage-source converter and can act as either a source or sink of reactive AC power to an electricity network. If connected to a source of power it can also provide active AC power. It is a member of the FACTS family of devices, that became possible in 1990s due to availability of powerful gate turn-off thyristors (GTO).[1] STATCOM is inherently modular and electable.

These compensators can also be used to reduce voltage fluctuations.[3]

History and uses

A prototype 1 MVAr STATCON was described in a report by Empire State Electric Energy Research Corporation in 1987.[4] The first production 100 MVAr STATCON made by Westinghouse Electric was installed at the Tennessee Valley Authority Sullivan substation in 1995 and was quickly retired due to obsolescence of its components.[5]

Usually a STATCOM is installed to support electricity networks that have a poor power factor and often poor voltage regulation.[6] There are however, other uses, the most common being to improve voltage stability.

Construction and operation
STATCOM as a voltage source (in red) connected to a transmission line

A STATCOM is a voltage source converter (VSC)-based device, with the voltage source behind a reactor (STATCOM is connected to the utility grid via a transformer).[7] The voltage source is created from a DC capacitor and therefore a STATCOM has very little active power capability. However, its active power capability can be increased if a suitable energy storage device is connected across the DC capacitor. The reactive power at the terminals of the STATCOM depends on the amplitude of the voltage source. For example, if the terminal voltage of the VSC is higher than the AC voltage at the point of connection, the STATCOM generates reactive current (appears as a capacitor); conversely, when the amplitude of the voltage source is lower than the AC voltage, it absorbs reactive power (appears as an inductor).[7][8]

A voltage droop of 1-10% (usually 3%) is built into STATCOMs.[7]

STATCOM vs. SVC

A static VAR compensator (SVC) can also be used to maintain the voltage stability. STATCOM is costlier than an SVC (in part due to higher cost of the GTO thyristors) and exhibits higher losses, but it has a few technical advantages. As a result, the two technologies coexist.

The response time of a STATCOM is shorter than that of a SVC,[9] mainly due to the fast switching times provided by the IGBTs of the voltage source converter (thyristors cannot be switched off in a controlled fashion). As a result, the reaction time of a STATCOM is one to two cycles vs. two to three cycles for an SVC.[10]

The STATCOM also provides better reactive power support at low AC voltages than an SVC, since the reactive power from a STATCOM decreases linearly with the AC voltage (the current can be maintained at the rated value even down to low AC voltage), as opposed to power being a function of a square of voltage for SVC.[11] The SVC is not used in a severe undervoltage conditions (less than 0.6 pu), since leaving the capacitors on can worsen the transient overvoltage once the fault is cleared, while STATCOM can operate until 0.2-0.3 pu (this limit is due to possible loss of synchronicity and cooling).[12]

The footprint of a STATCOM is smaller, as it does not need external inductors and large capacitors used by an SVC.[13]

See also

References
  1. Sen & Sen 2021, p. 14.
  2. Varma 2021, p. 186.
  3. Larsson, T.; Poumarede, C. (2017-12-18). "STATCOM, an efficient means for flicker mitigation". IEEE Power Engineering Society. 1999 Winter Meeting (Cat. No.99CH36233). Vol. 2. pp. 1208–1213. doi:10.1109/PESW.1999.747380. ISBN 978-0-7803-4893-6. S2CID 43908178.
  4. Sen & Sen 2021, p. 15.
  5. Sen & Sen 2021, pp. 14–15.
  6. Azharuddin, Mohd.; Gaigowal, S.R. (2017-12-18). "Voltage regulation by grid connected PV-STATCOM". 2017 International Conference on Power and Embedded Drive Control (ICPEDC). pp. 472–477. doi:10.1109/ICPEDC.2017.8081136. ISBN 978-1-5090-4679-9. S2CID 26402757.
  7. Varma 2021, p. 113.
  8. Al-Nimma, Dhiya A.; Al-Hafid, Majed S. M.; Mohamed, Saad Enad (2017-12-18). "Voltage profile improvements of Mosul city ring system by STATCOM reactive power control". International Aegean Conference on Electrical Machines and Power Electronics and Electromotion, Joint Conference. pp. 525–530. doi:10.1109/ACEMP.2011.6490654. ISBN 978-1-4673-5003-7. S2CID 29522033.
  9. Hingorani, Narain G.; Gyugyi, Laszlo (2017-12-18). "Static Shunt Compensators: SVC and STATCOM". Understanding FACTS. Wiley-IEEE Press Books. doi:10.1109/9780470546802. ISBN 9780470546802.
  10. Varma 2021, pp. 114–115.
  11. Singh, S. N. (23 June 2008). Electric power generation: transmission and distribution (2 ed.). PHI Learning Pvt. Ltd. p. 332. ISBN 9788120335608. OCLC 1223330325.
  12. Varma 2021, p. 114.
  13. Varma 2021, p. 115.

Sources
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.