Pooja Kulkarni- MSEE
Student- University of St. Thomas,
Electric power is undoubtedly the fundamental
component of modern society’s existence. The rising power demands for electricity
have created a huge impact on climate and environmental conditions globally. The
Smart Grid integrates conventional power system infrastructure with the
non-conventional energy sources (wind, solar etc.). However, the use of
renewable energy sources such as wind and solar energy makes the power systems
more complex and consequently changes the grid structure and brings a
significant change in the way that transmission and distribution system is
designed and operates.
to the US Department of Energy 1:
smart grid uses digital technology to improve reliability, security, and
efficiency (both economic and energy) of the electric system from large
generation, through the delivery systems to electricity consumers and a growing
number of distributed-generation and storage resources.” The smart
grid allows the incorporation of renewable energy sources as well as power
transmission system such as FACTS (flexible ac transmission systems)
controllers and HVDC (High Voltage Direct Current) systems. The challenge for
any electric power industry is to provide a network capable of delivering
contracted power from power supply station to consumer over long distance.
FACTS controllers can be effectively used to overcome the stability limits.
This paper discusses how FACTS controllers are used to control the power flow
in a transmission system.
Power system in earlier days:
three major categories of conventional electric grid system are Generation,
Transmissionism and distribution on broader level. At the power stations, the
power is generated using conventional sources of energy such as water, coal,
oil and natural gas etc. This power is produced at relatively low voltage from
2.3kV to 30kV depending upon the size of power station unit. This generator
voltage is stepped up by power station transformers to a higher voltage such as
115kV or above depending upon the transmission system for the transmission over
long distances. Transmission losses depend on I2R losses. Electric
power is usually transmitted through overhead transmission lines. This power is
stepped down at the distribution substation and then distributed to every
consumer. A lack of storage facilities in transmission system is the key
limitation. A sophisticated control system is needed to ensure matching of
power generation and power demands of consumers. If the demand of power supply
exceeds the power generated can cause generation plants and transmission lines
to shut down or disconnect to protect from damages.
Smart grid is the convergence of three major industries Electrical Power,
Telecommunication and Information Technology. Expertise from Electrical
industry is needed to provide high level layers of complete and end to end
transmission and distribution system.
Smart grid provides increased connectivity, automation and coordination between
utilities, consumers and networks that perform long distance distribution or
local distribution. The
smart grid is combination of conventional power system with non-conventional
energy sources. In the current scenario, the power transmission system is
overused because of increased industrial demands and need to provide open
access to generating companies and consumers. This creates a necessity of developing a new technology to ensure maximum
power transfer of existing transmission facility at the same time maintaining a
good quality of supply and enhanced security. The FACTS technology is
introduced to mitigate these difficulties by enabling utilities to get the most
service from their transmission facilities and enhance grid reliability. FACTS
controller is a power electronic-based system and other static equipment that
provide control of one or more AC transmission system parameters. 2 FACTS controllers are used in
regulating power flows, transmission voltages, and reduce the dynamic
Generally, FACTS controllers are
divided into four categories:
1. Series FACTS Controllers
2. Shunt FACTS controllers
3. Combined series-series Controllers
4. Combined Series-shunt Controllers
Series FACTS Controllers
Department of Energy, U.S.
(2009) Smart grid system report. Available via Online.
http://www.doe.energy.gov/. Cited 30 Jan 2013 (DOE/OEDER 2008a)
N.G Hingorani, L. Gyugyi,
‘Understanding FACTS. Concepts and Technology of Flexible AC Transmission
Systems’, IEEE Press, New York, 2000.