flexible ac transmission devices PPT.pdf

What Are FACTS Devices?
FACTS refers to a family of power‑electronic-based systems designed to enhance the performance and controllability of AC transmission networks—without the need for building new lines or substations
Wikipedia
betaengineering.com
.
They achieve this by dynamically regulating three key transmission parameters:
Voltage magnitude
Line impedance
Phase angle difference
Operating on sub-cycle timescales (far faster than traditional mechanical methods), these devices enable smarter, more flexible power flow control
Wikipedia
.
Classification of FACTS Devices
FACTS controllers are categorized by how they connect within the transmission system:
1. Shunt Compensation Devices
Static VAR Compensator (SVC): Adjusts voltage by rapidly switching capacitor/reactor banks to generate or absorb reactive power
Wikipedia
EEP - Electrical Engineering Portal
ELECTRICAL TECHNOLOGY
Engineering Notes India
.
Static Synchronous Compensator (STATCOM): A VSC-based device offering much faster and smoother reactive power control than SVCs; suitable even under low-voltage or fault conditions
Wikipedia
+1
TutorialsPoint
PubMed Central
.
2. Series Compensation Devices
Thyristor-Controlled Series Capacitor (TCSC): Employs thyristors to vary series capacitance smoothly, fine-tuning line impedance
ELECTRICAL TECHNOLOGY
TutorialsPoint
ElectronicsHub
Number Analytics
.
Thyristor Switched Series Capacitor (TSSC): Offers stepwise capacitance control via thyristors, lowering cost and complexity
ELECTRICAL TECHNOLOGY
TutorialsPoint
ElectronicsHub
.
Static Synchronous Series Compensator (SSSC): A VSC-based device that injects a controllable voltage in series with the line, effectively emulating capacitive or inductive reactance
ELECTRICAL TECHNOLOGY
TutorialsPoint
Wikipedia
Number Analytics
.
3. Combined Devices
Interline Power Flow Controller (IPFC): Multiple series converters sharing a DC link to manage flow across several transmission lines
ELECTRICAL TECHNOLOGY
ElectronicsHub
Engineering Articles
.
Unified Power Flow Controller (UPFC): A premier FACTS device that combines STATCOM and SSSC functionalities via a common DC link, controlling voltage, impedance, and phase angle simultaneously
ELECTRICAL TECHNOLOGY
Wikipedia
TutorialsPoint
Number Analytics
.
Origins & Historical Evolution
Developed over decades, FACTS technology burgeoned from EPRI’s research and early thyristor-based systems, eventually gaining traction in the 1990s
WIRED
betaengineering.com
Wikipedia
.
By 2010, IEEE recognized FACTS as one of the decade's most significant technological achievements
betaengineering.com
.
FACTS devices have become essential for integrating variable renewables (like wind), optimizing long-distance power transfer, and enhancing grid reliability

1. FACTS
(Flexible AC Transmission
System)
1

2. Contents:
Introduction
Need of FACTS
Types of FACTS Controllers
Series Connected Controller
Shunt Connected Controller
Combined Shunt-Series Controller
Combined Series-Series Controller
Advantages
Disadvantages
Applications



2

3. •Introduction
•FACTS, or Flexible AC Transmission System, refers to power electronics-based
devices used to improve the performance of AC transmission systems.
•These devices enhance power transfer capability, controllability, and stability of
power networks.
•They can be connected in series or shunt with transmission lines, and they help
manage reactive power, voltage, and impedance to optimize power flow.
•The significance of FACTS technology lies in its ability to enable real-time
control and flexibility in power transmission, allowing grid operators to respond
to changing conditions and optimize grid performance.


3

4. •Need of FACTS
•In a power system, coordination between the generation and demand is necessary.
The demand for electrical energy increases day by day. To meet this demand, it is
necessary to operate all components at their maximum efficiency.
•The FACTS devices are nothing but the device used to increase the efficiency of
the transmission system.
•There are three types of power; Active power, Reactive power and Apparent
power. Active power is the useful power or true power that we want to transmit.
But load consists of various energy stored elements, that causes the reactive
power.
•There are two types of reactive power; inductive type and capacitive type.
Reactive power is necessary to remain a balance between inductive reactive
power and capacitive reactive power.



4

5. •Otherwise, the reactive power will flow through the transmission network. And
reactive power reduces the capacity of transferring active power.
•So, the techniques used to make a balance between inductive and capacitive reactive
power are known as compensation techniques.
•The inductive and capacitive reactive power supply or absorbs by these techniques. In
this way, it improves the quality of power and efficiency of the transmission network.
•Before the invention of power electronics switches, these problems were solved by
connecting capacitor, reactor, or synchronous generator with the help of mechanical
switches.
•But there is a lot of problems to use the mechanical switches. It has a very slow
response and there is a problem of wear and tear of mechanical switches.
•So, these are not reliable ways to increase the controllability and stability of the
transmission line.
•After the invention of power electronics switch like thyristor that can be used for the
high voltage applications, power electronics bases FACTS controllers are developed.




5

6. •Types of FACTS Controllers
•According to the type of connection FACTS Controller with the power system, it
is classified as;
1.Series Connected Controller
2.Shunt Connected Controller
3.Combined Shunt-Series Controller
4.Combined Series-Series Controller




6

7. 1) Series Connected Controller
•The series controllers are used to introduced voltage in series with the line voltage. It
consists of a capacitor or reactor (impedance devices). This type of controllers is used to
supply or consume variable reactive power.
•When the load of the transmission line is more, it needs extra reactive power. In this
condition, it is used to supply reactive power with the help of a capacitor.
•When the transmission line operates on very light load, the receiving end voltage increase
than the sending end voltage due to less demand for reactive power. In this condition, it is
used to consumes reactive power with the help of an inductor.




7
•In most of the case, the capacitors are installed at
the end of the line to compensate demand for
reactive power. The below figure shows the
basic diagram of series connected Controller.
Example:- Thyristor controlled series capacitor
(TCSC), Static synchronous series capacitor
(SSSC) etc.

8. 2) Shunt Connected Controller
•This type of device is used to inject current to the power system at the point of
connection. Similar to the series-connected controllers, it also consists of variable
impedance like capacitor and inductor.
•When a capacitor is used to connect parallel with the power system, the method
is known as shunt capacitive compensation.
•When the transmission line consists of a more inductive load, it operates on
a lagging power factor. This method is used to draws current leading to the
source voltage to compensate for the lagging load with the help of a shunt
connected capacitor.




8
•When an inductor is used to connect in shunt
with the power system, the method is known
as shunt inductive compensation.

9. •Generally, this method is not more useful with the transmission network.
•But in case of a very large transmission line, the load is disconnected or it
operates on no-load or less load condition, due to the Ferranti effect, the receiving
end voltage increase then the sending end voltage. to avoid this condition, the
shunt inductive compensator is used.
•Example:- STATCOM, Static VAR compensator (SVC),




9

10. 3) Combined Shunt-Series Controller
•This type of controller is used to introduce voltage in parallel using the shunt
controller and along with it used to introduce the current is series using the series
controller.
•But both controllers must operate with coordination. The example of this type of
controller is the Unified Power Flow Controller (UPFC).





10
•A hybrid type that combines both series
and shunt components.
•They can inject current (shunt) and inject
voltage (series), allowing control over
both active and reactive power, often
through a shared power link.

11. 4) Combined Series-Series Controller
•In multilane transmission lines, a combination of separate series controllers is
used in a coordinated manner to provide independent series reactive
compensation for each line.
•But it can transfer real power with lines via power link. Or it can be connected
with unified controllers that the DC terminals of converters are interlinked
together.



11
•This will help to transfer the real power to
the transmission line. An example of this
type of system is the Interlink Power Flow
Controller (IPFC).

12. •Types of FACTS Devices
•Various FACTS devices are introduced to fulfill their application. The most used
FACTS devices or controller as listed below.
1) Series Compensator:
•Controlled Impedance/Reactance based Compensator
 Thyristor Switched Series Capacitor (TSSC)
 Thyristor Controlled Series Capacitor (TCSC)
 GTO-switched Series Capacitor (GSSC)
 Gate Controlled Series Capacitor (GCSC)
•Converter based Compensators
 Static Synchronous Series Compensator (SSSC)


12

13. 2) Shunt Compensator:
•Controlled Susceptance based Compensator
 Static VAR Compensator (SVC)
•Thyristor Controlled Reactor (TCR)
•Thyristor Switched Capacitor (TSC)
•Fixed Capacitor (FC) - Thyristor Controlled Reactor (TCR)
•Mechanical Switched Capacitor (MSC)-Thyristor Controlled Reactor (TCR)
•Thyristor Switched Capacitor (TSC) - Thyristor Controlled Reactor (TCR)
•Converter based Compensators
Static Synchronous Compensator (STATCOM)
3) Series-shunt Compensator:
• Unified Power Flow Controller (UPFC)
4) Series-series Compensator:
• Interline Power Flow Controller (IPFC)



13

14. •Advantages
1.The FACTS devices are used to increase the power transfer capability of the transmission line.
Hence, it saves costs to develop an entirely new transmission line.
2.It increases the loading capability of the transmission line of their thermal capability.
3.It reduces the amount of reactive power in the transmission line. In this way, the transmission
line can transfer more amount of active power to the load.
4.The FACTS devices are used to control the amount of flow of power through the transmission
line. So, it helps to follow the guideline and contract of utility and ensure the optimum flow of
power.
5.It reduces the cost of power as it reduces the transmission cost.
6.It increases the quality of power, voltage stability, thermal stability, and transient stability of
the system.
7.FACTS devices are not containing any environmentally hazardous waste material. Hence, this
technology of environmentally friendly.
8.It improves the power factor of the power system network.
9.It increases the reliability and flexibility of the transmission network.



14

15. •Disadvantages
1.The FACTS devices are used power electronics switches to control supply or
absorb the power. The major disadvantage of the use of power electronics switch
is that it induces harmonics in the output signals. These harmonics enter into the
power system network. So, the active filters are used to remove the harmonics.
2.The initial cost of FACTS devices is very high.
3.It transmits a limited amount of power.
4.It needs continuous maintenance and the repair cost of these devices are very
high.
5.It uses converters. Hence, the amount of power loss occurs in the switches.
6.If the current from the FACTS devices is increased due to any reason, there may
be a chance to damage the power electronics switches used in the converter. And
the cost of these switches is very high.



15

16. •Applications
1) Enhancing Power Transmission Efficiency and Reliability
•FACTS devices can be used to enhance power transmission efficiency and reliability by
controlling power flow, regulating voltage, and reducing power losses. For example,
TCSCs can be used to control power flow and reduce congestion on transmission lines,
while SVCs and STATCOMs can be used to regulate voltage and improve voltage
stability.
2) Improving Grid Stability and Voltage Regulation
•FACTS devices can be used to improve grid stability and voltage regulation by providing
reactive power compensation and regulating voltage. For example, SVCs and STATCOMs
can be used to regulate voltage and improve voltage stability, while TCSCs can be used to
enhance grid stability by controlling power flow.
3) Mitigating Power Quality Issues and Reducing Losses
•FACTS devices can be used to mitigate power quality issues and reduce losses by
regulating voltage, controlling power flow, and providing reactive power compensation.
For example, SVCs and STATCOMs can be used to regulate voltage and improve power
quality, while TCSCs can be used to control power flow and reduce losses.


16

17. 17