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SriVidya College of Engineering and Technology
Virudhunagar
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
UNIT IV- Emerging FACTS Controllers
1. What is STATCOM?
The STATCOM (or SSC) is a shunt-connected reactive power compensation device that
is capable of generating and/or absorbing reactive power and in which the output can be
varied to control the specific parameters of an electric power system.
2. State the salient features of STATCOM features.
 Compact size
 System voltage support and stabilization by smooth control over a wide
range of operating conditions
 Dynamic response following system contingencies
 High reliability with redundant parallel converter design and modular construction
 Flexibility of future reconstruction to Back to Back(BTB) power transmission
or
UPFC(Unified Power Flow Control) and other
configuration
3. List the application of STATCOM.
 Damping of power system oscillations
 Damping of sub synchronous oscillations
 Balanced loading of individual phases
 Reactive compensation of AC-DC converters and HVDC links
 Improvement of steady state power transfer capacity
4. Compare the V-I Characteristic of STATCOM & SVC
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5. How the reactive power compensation is done using STATCOM.
A STATCOM is a controlled reactive power source. It provides the desired reactive
power generation and absorption entirely by means of electronic processing of the voltage
and current waveforms in a voltage source converter
6. List the modes of operation of STATCOM
The STATCOM can be operated in two different modes:
 Voltage regulation mode under this mode it has 3 sub divisions. There are,
 Over excited mode of operation
 Under excited mode of operation
 Normal(floating) excited mode of operation
 Var control mode
7. Draw VI characteristics of
STATCOM.
8. Compare STATCOM and SVC.
 The STATCOM has the ability to provide more capacitive reactive power
during faults, or when the system voltage drops abnormally, compared to
ordinary static var compensator. This is because the maximum capacitive
reactive power generated by a STATCOM deceases linearly with system
voltage, while that of the SVC is proportional to the square of the voltage.
 Also, the STATCOM has a faster response as it has no time delay associated
with thyristor firing. Nevertheless, these advantages come at a higher price(about
20% more)
9. What are the function of STATCOM?
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 Dynamic voltage control in transmission and distribution systems.
 Power oscillation damping in power transmission systems
 Transient stability improvement
 Ability to control not only reactive power but, if needed, also active power
(with a
DC energy source
available)
10. Define STATCOM.
 The STATCOM has been defined as per CIGRE/IEEE with following three
operating scenarios.
 First component is static: based on solid state switching devices with no
rotating components;
 Second component is Synchronous: Analogous to an ideal synchronous machine
with
3 sinusoidal phase voltages at fundamental frequency;
 Third component is compensator: rendered with reactive compensation.
11. List the advantages/benefits of STATCOM.
The STATCOM offers following advantages:






Superior voltage supporting capability
Fast response
Large reactive power generation under low system voltage condition
Less harmonics generation
Smaller filter capacity
Less space requirement
12. What is UPFC?
The UPFC is a device which can control simultaneously all three parameters of line
power flow(line impedence, voltage and phase angle).Such “new” FACTS device
combines together the features of two “old” FACTS devices” the Static Synchronous
Compensator(STATCOM) and the Static Synchronous Series Compensator (SSSC). It is
proposed by Gyugyi in 1991.
13. What is role of dc link in UPFC?
The real power is supplied from, or absorbed by, the DC energy storage device called dc
link.
14. List the application of UPFC.
 Power flow control
 Power swing damping
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

Voltage dips compensation
Fault Current Limiting
19. State the salient features of UPFC.
 The UPFC is versatile and multifunction power flow controller with
capabilities of terminal voltage regulation , series line compensation and phase
angle regulation
 Minimization of power losses with out generator rescheduling
 Regulating power flow through a transmission line
 More reliable
 Provides dynamic security
 Acts as harmonic isolator
20. What are the parameters that can be improved using STATCOM in power system?
 The dynamic voltage control in transmission and distribution system
 The power oscillation damping in power transmission system
 The transient stability
 The voltage flicker control
 The control of not only reactive power but also active power in the connected
line, requiring a Dc energy
source
21. What are the different constraints for operating UPFC?
 The series injected voltage magnitude
 The line current through series converter
 The shunt converter current
 The minimum line side voltage of the UPFC
 The maximum line side voltage of the UPFC
 The real power transfer between the series converter and the shunt converter
22. What are the operating modes of
UPFC?
 VAR Control Mode
 Automatic Voltage Control Mode
 Direct Voltage Injection Mode
 Phase Angle Shifter Emulation Mode
 Line Impedance Emulation Mode
 Automatic Power Flow Control Mode
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16 MARKS
1. With a neat sketch, explain the implementation of UPFC.
2. Explain the working of STATCOM with a neat sketch. In what way it differs from SVC?
3. Explain the operation of STATCOM with its V-I characteristics.
4. Explain the performance of VSC based STATCOM.
5. Describe the modeling of UPFC for power flow and transient stability studies.
6. Explain the basic principle and control capability of unified power flow controller.
7. Explain the power transfer capability of UPFC and compare its capabilities with other FACTS
controllers.
8. Describe the construction of UPFC with a block diagram and its characteristics with phasor
diagrams.
9. Explain the power flow control and oscillation damping in the two area system using UPFC.
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