This document summarizes a seminar presentation on HVDC and FACTS technologies for improving power transmission through long lines. It introduces HVDC and its applications for long distance transmission. FACTS devices are discussed as providing advantages over HVDC, including flexible control of voltage, current and power flow. The Unified Power Flow Controller (UPFC) is examined as a combined series-shunt FACTS device. The Power System Analysis Toolbox (PSAT) is introduced for modeling and simulating HVDC and FACTS devices on transmission lines, allowing analysis of faults and power flow control.

1. A
Seminar on
HVDC and FACTS for Improved
Power Delivery Through Long
Transmission Lines
Presented to: Presented By:
Prof. S.C.MITTAL RAJARAM CHANDRAMEENA
Prof. D.K.YADAV Roll no.-13/939
DEPARTMENT OF ELECTRICAL ENGINEERING, RTU, KOTA

2. CONTENTS
• Introduction of HVDC, and it’s Applications
• HVDC use in Long transmission lines
• Introduction of FACTS and it’s Advantages
• FACTS use in Long transmission lines
• Study of UPFC
• Power system analysis toolbox (PSAT)
• PSAT used in HVDC or UPFC line
• Conclusion
• References

3. Introduction of HVDC
• For long distance high power transmission by
overhead line & underground line.
• Requires converter stations at each end of the
line.
• It can interconnect different power systems.
• Frequency conversion-
(60 Hz to 50 Hz, 50Hz to 25 Hz).

4. COMPONENTS OF HVDC
TRANSMISSION SYSTEMS
Following component are used in DC system-
• Converters
• Smoothing reactors
• Reactive power supplies
• Harmonic filters
• Electrodes
• DC lines
• Circuit breaker

5. CONVERTERS
• Perform AC/DC (rectifier) and DC/AC
(inverter) conversion.
• They consist of bridges and transformers.
• The transformers are ungrounded such that
the DC system will be able to establish its
own reference to ground.

6. Multiple Bridge Converters
• Two or more bridges are
connected in series to obtain as
a high a direct voltage as
required.
• These bridges are series on the
DC side, parallel on the AC
side.
• The ratio of the transformers are
adjustable under load.
• Multiple bridge converters are
used in even numbers and
arranged in pairs for 12-pulse
arrangement .

7. SMOOTHING
REACTORS….
•They decrease harmonics in
voltages and currents in DC
lines.
•The availability of the
Smoothing inductors is to
control the pulses of
constant current flows into
the transformer’s secondary
windings.
•Prevent current from being
discontinuous for light
loads.

8. REACTIVE POWER SUPPLIES
Reactive power (VAR) compensation is defined as the
management of reactive power to improve the
performance of ac systems. There are two aspects:-
1. Load Compensation – The main objectives are to:-
• Increase the power factor of the system.
• To balance the real power drawn from the system.
• Compensate voltage regulation.
• To eliminate current harmonics.
2.Voltage Support – The main purpose is to decrease the
voltage fluctuation at a given terminal of transmission
line.
Therefore the VAR compensation improves the
stability of ac system by increasing the maximum
active power that can be transmitted.

9. Continue…
Power is referred as the product of voltage and current
i.e. power = V x I
The portion of electricity that establishes and sustains
the electric and magnetic fields of alternating-current
equipment. Reactive power must be supplied to most
types of magnetic equipment, such as motors and
transformers.
In an ac transmission, when the voltage and
current go up and down at the same time, only real
power is transmitted and when there is a time shift
between voltage and current both active and reactive
power are transmitted.

10. AC HARMONIC FILTERS
• In the presence of system impendence of this
causes a non-sinusoidal voltage drop causing
voltage distortion at the load terminals known
as Harmonic Distortion.
• AC harmonic filters used to reduce
harmonics caused by converters which
generate harmonics in voltages and currents.
• These harmonics may cause overheating of
capacitors and nearby generators and
interference with telecommunication systems.

11. ELECTRODES
• Used to provide connection to the earth for neutral.
DC LINES
• They may be overhead lines or cables.
• DC lines are very similar to AC lines.
CIRCUIT BREAKERS
• They used to clear faults in the transformer and for
taking the DC link out of service.
• They are not used for clearing DC faults.
• DC faults are cleared by converter control more
rapidly(quickly).

12. ADVANTAGES OF HVDC
• Control of dc quantities (voltage, Current and Power).
• Loss is very less as no frequency reversals taken into
account.
• Improve line loading capacity & also increases the
efficiency of transmission.
• Requires less numbers of conductors for same power
transfer.
• Reduced in tower size (less clearance).

13. Continue...
• More power can be transmitted more efficiently over
long distances by applying hvdc.
• Interconnection of two AC systems, where AC lines
would not be possible due to stability problems or
both systems having different nominal frequencies.
• Control of Reactive Power and control of AC
Voltages.
• HVDC transmission is necessary for underwater
power transfer if the cables are longer than 50km.

15. Introduction of FACTS
• FACTS as they are generally known, are new
devices that improve transmission systems.
• FACTS is a static equipment used for the AC
transmission of electrical energy.
• It is generally a power electronics based device.
• To enhance controllability and increase power
transfer capability.

16. Continue…
• Flexible AC Transmission System (Facts) is a
new 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.

17. Benefits of FACTS
• Reduces the need for construction of new transmission
lines, capacitors and reactors.
• Provides greater ability to transfer power between
controlled areas.
• Improves the transient stability of the system.
• Controls real and reactive power flow in the line
independently.
• Increase quality of supply for sensitive industries.
• Increase transmission system reliability and availability.

18. Types of FACTS
• (a) Series controller
• (b) Shunt controller
• (c) Combined series-series controller
• (d) Combined series-shunt controller

19. •Series controller
It is designed to vary the impedance of the line
by presenting to the line circuit series
equivalents of capacitor, reactor or a variable
source. Voltage is injected in series from this
controller to vary the reactive power
compensation.
• Shunt controller .
 It varies the shunt impedance connected to the
line by current injection. It can supply or
absorb variable reactive power.

20. Combined series-series controller
• It is use in multi-line transmission system. It
provides series reactive power compensation
for each line (3-phase) for real power to be
transferred via the interconnection. Another
term used for this controller is Interline Power
Flow Controller (IPFC), which is able to
balance both the real and reactive power flow.
It also contains a DC link like capacitor or
“battery” that provides energy storage.

21. •Combined series-shunt controller
It in which contains series and shunt elements
via a DC link for power exchange.

22. 22
Efficient Installations: Easily installed in transmission lines.
Increased System Capacity: Maximum operational efficiency of
existing transmission lines and other equipment.
System Reliability: Provide greater voltage stability and power
flow control, which improves system reliability and security.
Improved System Controllability: Intelligence built into the
grid, ability to instantaneously respond to disturbances & redirect
power flows.
Investment: Less expensive than new transmission lines.
Greater flexibility as compare to hvdc line.
Improving real power transfer capability.
Advantage of FACTS Devices

23. STUTY OF UPFC
• The UPFC is a device which can control simultaneously
all three parameters of line power flow(voltage,current
power).
• Such "new" FACTS device combines together the
features of two "old" FACTS devices:
1. STATCOM
2. SSSC
• These two devices are two Voltage Source controller’s
(VSC’s) connected respectively in shunt with the
transmission line through a shunt transformer and in
series with the transmission line through a series
transformer, connected to each other by a common dc
link including a storage capacitor.

24. Continue…
• The shunt converter (STATCOM) is used for
voltage regulation at the point of connection
injecting an opportune reactive power flow into
the line and to balance the real power flow
exchanged between the series inverter and the
transmission line.
• The series converter (SSSC) can be used to control
the real and reactive line power flow inserting an
opportune voltage with controllable magnitude
and phase in series with the transmission line.
• It’s also known as “unified” controller and
require small amount of power for DC circuit
exchange occurring between the shunt-series
converters.

25. CIRCUIT DESCRIPTION
• The basic configuration of a UPFC, which is installed
between the sending-end Vs and the receiving-end VR.
the dc terminals of which are connected to a common
dc link capacitor.
Fig1: Basic configuration of UPFC

26. Power System Analysis Toolbox (PSAT)
• PSAT is a Matlab toolbox for static and dynamic
analysis and control of electric power systems.
• All operations can be assessed by means of graphical
user interfaces (GUIs) and a Simulink based library
provides an user friendly tool for network design.
• In order to perform accurate power system analysis,
PSAT supports a variety of static and dynamic
component models.
• A HVDC system is implemented in PSAT,
representing two AC/DC converters connected by a
DC line.

27. VSC HVDC in a DC line circuit with fault and
load and its back- to-back converter
(rectifier and inverter)

28. PSAT used in HVDC or UPFC line
a. The fundamental values of using lesser
command lines for power simulation can be
investigated and differences of power
enhancement by applying HVDC or UPFC in a
line can be reviewed critically.
b. Three phase generator is connected with a fault
at the remote end bus (receiving end bus), which
is the inverter. Normal power flow simulation is
conducted using toolbox with discrete time in
Matlab .
c. Fault is introduced at the inverter end or rectifier
end, then clearing time is very low.

29. Results…
d. PSAT in general is more suitable for
fundamental power flow and is more
graphical user interface based simulation.
e. There are adequate types of FACTS model and
as well with latest power devices for
continuous or optimal power flow studies in
for a given network.
e. PSAT is found to be more user friendly toolset.

30. CONCLUSION
• The advantages of HVDC in promoting damping of lines
power oscillation were shown in the case study to be
more efficient than UPFC.
• HVDC can be very useful for long transmission lines.
• It is more recommended in networks or interconnected
lines that have high variation of power demands and
complicated network connections with different power
frequencies.
• the cost for installing HVDC is 85 percent greater than
FACTS devices.
• UPFC in general is good for promoting line load-ability
and pool through interconnected network buses more
effectively.

31. REFERENCES
• IEEE guide for commissioning High-Voltage Direct-
Current (HVDC) converter stations and associated
transmission systems.
• N.G. Hingorani & L. Gyugyi, "Understanding FACTS,"
New York.
• A. Edris, “Technology Developments Applications of
power electronics-Based controller on transmission grid”.
• E.M. Yap, M. Al-Dabbagh, “Applications of FACTS
Controller for Improving Power Transmission
Capability”.
• F. Milano, “Power System Analysis Toolbox
documentation (PSAT)”.

32. Thank you!