This document provides a comprehensive overview of the role and functions of Flexible AC Transmission System (FACTS) devices in enhancing power system stability and performance. It details various types of compensation devices, their functionalities, and the mechanisms through which they operate, such as voltage and power flow control. Conclusively, the document emphasizes the significance of FACTS in ensuring reliable and efficient power transmission by mitigating oscillations and improving system stability.

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ETHIOPIAN DEFENCE UNIVERSITY
COLLEGE OF ENGINEERING
DEPARTEMENT OF ELECTRICAL ENGINEERING
POWER SYSTEM AND AUTOMATION STREAM
POWER SYSTEM DYNAMICS AND STABILITY
COURSE CODE: EP-6061
Seminar presentation
ON
ROLE OR FUNCTIONS OF FACTS DEVICES AND DIFFERENT COMPENSATION DEVICES FOR STABLE POWER SYSTEM OPERATION
GROUP MEMBERS
No NAME ID No
Ediris Abrahim Umer RPG/0077/16
Kefale Atinafu RPG/0087/16
Shibeshi welderufael RPG/0033/16
Khader Ahimed Farah RPG/0071/16
BISHOFTU, ETHIOPIA
OCTOBER, 2024

2. Outline
 Compensation Devices
 What IS FACTS
 Types of FACTS Controllers
 Role or functions of FACTS
 FACTS devices and It’s compensation mechanisms
 Conclusion
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3.  Compensation devices
Compensation devices are a broad category of devices used in power systems to improve
system performance, stability, and power quality.
It's important to note that the specific type of compensation device used will depend on the
application and the nature of the compensation required.
They are designed to compensate for various electrical parameters such as reactive power,
voltage, and line impedance.
These devices can be deployed in different parts of the power system, such as distribution
networks or transmission lines, to regulate voltage levels, control power flow, and enhance
system reliability.
 Compensation devices include capacitors, reactors, and other devices that are specifically used
for reactive power compensation or voltage control.
And also, FACTS devices are a specific subset of compensation devices that utilize power
electronics and advanced control techniques to provide dynamic and real-time control of power
flow, voltage stability, and other parameters in power transmission and distribution networks.
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4.  Compensation device and it’s Types
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Fig 1 block diagram of compensation devices

5.  What is FACTS
Flexible AC Transmission System (FACTS) is an integrated concept based on power
electronic switching converters and dynamic controllers to enhance the system utilization
and power transfer capacity as well as the stability, security, reliability and power quality
of AC system interconnections.
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Fig 2 diagram of FACTS device connected on transmission line

6.  Types of FACTS Controller
Series Controllers
The series controller could be a variable impedance or a variable source both are power
electronics based. In principle, all series controllers inject voltage in series with the line.
The main purpose of series compensation in power systems is to decrease the reactive impedance
of the transmission line to reduce voltage drop over long distances and to reduce the Ferranti
effect. These series controllers includes, TCSC, SSSC, TSSC, TCSC, and TCSR.
Shunt Controllers
The shunt controllers may be variable impedance connected to the line voltage causes a variable
current flow hence represents injection of current into the line.
These shunt controllers includes, STATCOM, STAT VAR(SVC) and TCR.
Combined Series-series Controllers
 The combination could be separate series controllers or unified series-series controller-Interline
Power Flow Controller. E.g inter line power flow controller (IPFC).
Combined Series-shunt Controllers
The combination could be separated series and shunt controllers or a unified power flow
controller. E.g Unified power flow controller (UPFC).
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7. 6/19/2024 7
Fig 3 block diagram of Types FACTS

8.  Role or Functions of FACTS Devices
The role or function of FACTs devices is to provide precise and rapid control over the transmission
system, allowing operators to manage and mitigate various power system issues.
 Some of the key functions of FACTs devices include:
 Increase loading capacity of transmission lines.
 Prevent blackouts.
 Improve generation productivity
 Voltage Control: FACTs devices can regulate voltage levels within desired limits by injecting or
absorbing reactive power. This helps maintain voltage stability and improve power transfer capability.
 Power Flow Control: FACTs devices enable control over active power flow in transmission lines. By
adjusting the line impedance, they can redirect power flow to relieve congestion and optimize power
transfer.
 Damping of Power System Oscillations: FACTs devices can provide supplementary damping to
power system oscillations, improving the transient stability of the system. They achieve this by
injecting or absorbing reactive power in a controlled manner.
 Enhancing Grid Stability: FACTs devices help mitigate voltage fluctuations and grid instability caused
by sudden changes in load or system disturbances. By regulating voltage and power flow, they
contribute to stable grid operation.
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9.  FACTS DEVICES and IT’S COMPENSATION MECHANISMS
There are various types of FACTs devices, each with its own compensation mechanism and characteristics.
As we early mentioned FACTS are of two generations:
1) First generation FACTS(Thyristor-controlled):
 Static Var Compensator (SVC)
 Static Condenser (STATCON) and
 Thyristor series compensator (TSC)
2) Second generation FACTS(VSC-Controlled):
 Static Synchronous Compensator (STATCOM)
 Static Synchronous Series Compensator (SSSC):
 Unified Power Flow Controller (UPFC)
 Inter-line power flow control (IPFC)
The 1st Generation FACTS principle of working:
 The thyristor-controlled group employs capacitor and reactor banks with fast solid-state switches in traditional
shunt or series circuit arrangements. The thyristor switches control the on and off periods of the fixed capacitor
and reactor banks and thereby realize a variable reactive impedance. Except for losses, they cannot exchange
real power with the system
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10.  The working principle of the 2nd generation
 The voltage source converter (VSC) type FACTS controller group employs self-
commutated DC to AC converters, using GTO thyristors, which can internally
generate capacitive and inductive reactive power for transmission line
compensation, without the use of capacitor or reactor banks.
The converter with energy storage device can also exchange real power with the
system, in addition to the independently controllable reactive power.
The VSC can be used uniformly to control transmission line voltage, impedance,
and angle by providing reactive shunt compensation, series compensation, and
phase shifting, or to control directly the real and reactive power flow in the line.
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11.  Static Var (Volt-amper reactive) Compensator (SVC)
SVC is a shunt-connected device that injects or absorbs reactive power to regulate
voltage and improve system stability.
The crucial equipment which is included in this device is TCC and TCR which are
a thyristor-controlled capacitor and thyristor-controlled reactor.
Fig 4 static var compensator
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12.  Static condensers (STATCON)
 STATCON is currently the best solution in reactive power control filed.
Compared with the traditional SVC represented by TSC, the regulation speed of STATCON is
faster (the response speed is within 5ms).
 Its compensation precision is high (the power factor after compensation is over 0.99).
 the compensation method is flexible (STATCON can compensate both inductive reactive
power and capacitive reactive power), and STACTON also has the function of active filtration
of harmonic current.
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Fig 5 Static Synchronous Condenser STATCON

13.  Thyristor controlled series compensation (TCSC
Series Compensation with Thyristor Control (TCSC) enables rapid dynamic modulation of
the inserted reactance.
 At interconnection points between transmission grids, this modulation will provide strong
damping torque on inter-area electromechanical oscillations.
Often the TCSC is combined with fixed series compensation to increase transient stability in
the most cost effective way.
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Fig 6 Thyristor series controlled capacitor (TSCC

14.  Static Synchronous compensator(StatCOM)
 It is a shunt device of the Flexible AC Transmission Systems (FACTS) family using power
electronics to control power flow and improve transient stability on power grids.
 The STATCOM regulates voltage at its terminal by controlling the amount of reactive
power injected into or absorbed from the power system.
 When system voltage is low, the STATCOM generates reactive power (STATCOM
capacitive).
 When system voltage is high, it absorbs reactive power (STATCOM inductive).Similarly to
the SVC the STATCOM can provide instantaneous and continuously variable reactive
power in response to grid voltage transients enhancing the grid voltage stability.
 STATCOM is GTO or IGBT based.
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Fig 7 StatCOM based on voltage sourced and current sourced converter

15.  Static Synchronous Series Compensator (SSSC)
 It is a series-connected device that uses VSC technology to regulate transmission line
parameters.
 It can control the line impedance and improve power flow control and transient stability.
 It can be considered as a FACTS controller acting like a controlled series capacitor.
 It compensates the inductive voltage drop in the line by inserting capacitive voltage in order to
reduce the effective inductive reactance of the transmission line.
 In contrast to series capacitor, the SSSC is able to maintain a constant compensating voltage in
case of variable line current or controls the amplitude of the injected compensating voltage
independent of amplitude of line current.
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Fig 8 Static Synchronous Series Compensator(SSSC)

16. Unified Power Flow Controller (UPFC)
It is an electrical device for providing fast-acting reactive power compensation on high
voltage transmission networks.
 It uses a pair of three-phase controllable bridges to produce current that is injected
into a transmission line using a series transformer.
 The controller can control active and reactive power flows in a transmission line.
 The UPFC uses solid state devices, which provide functional flexibility, generally not
attainable by conventional Thyristor controlled systems.
 The UPFC is a combination of a static synchronous compensator (STATCOM) and a
static synchronous series compensator (SSSC) coupled via a common DC voltage
link.
 The UPFC is a combination of a static synchronous compensator (STATCOM) and a static
synchronous series compensator (SSSC) coupled via a common DC voltage link.
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17. Con’t
The main advantage of the UPFC is to control the active and reactive power flows in the
transmission line.
If there are any disturbances or faults in the source side, the UPFC will not work.
 The UPFC operates only under balanced sine wave source.
The controllable parameters of the UPFC are reactance in the line, phase angle and voltage.
Fig 9 Unified Power flow controller(UPFC)
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18.  Inter-line power flow control (IPFC)
The Interline Power Flow Controller (IPFC) is designed to control and optimize power flow in
multi-line transmission systems.
It consists of several voltage source converters (VSCs) connected in series with transmission
lines. VSCs inject controllable voltage into the lines, which allows for the real and reactive
power flow to be controlled independently.
Here are some key facts about IPFC devices:
Power Flow Control: The IPFC device can independently control the active power (real power)
and reactive power flow on multiple transmission lines.
By manipulating the injected voltage, it can change the impedance of the transmission lines,
thereby influencing the power flow.
 Voltage Regulation: IPFC devices can regulate the voltage levels in transmission lines by
injecting or absorbing reactive power. This helps in maintaining a stable voltage profile
throughout the network.
 Series Compensation: IPFC provides series compensation by injecting voltage in series with
the transmission lines. This compensates for the line impedance and helps in reducing
transmission line losses and increasing the transfer capacity of the line.
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19. Con’t
 Dynamic Control: IPFC devices can respond rapidly to changing system conditions and
adjust the injected voltage accordingly.
This enables them to mitigate congestion, improve system stability, and enhance overall
system performance.
enhanced system controllability and
Installation Location: IPFC devices are typically installed at substations or along transmission
lines, strategically placed to optimize power flow and voltage regulation in the network.
 Benefits: IPFC devices offer several benefits, including increased transmission capacity,
improved voltage stability, reduced transmission losses, and flexibility.
Fig 10 schematic diagram of IPFC
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20. 6/19/2024 20
 FACTS is an application of power electronics in power transmission system.
 FACTS has an important role in real and reactive power control.
 FACTS makes a system stable.
 All the above aspects show the effectiveness of these devices to suppress
oscillations and stabilizing the power system.
 Power system is always required normal and stable operation at rated operating
condition & it’s also required improvement of stability .
 Stability of power system is improved by using shunt & series capacitors, governing
system and FACTS controllers.
CONCLUSION