STABILTY OF POWER
OF HVDC SYSTEM USING
Under the guidance
of Ms. Saritha DEVI
MOHD FAISAL MADANI 09RT1A0217
MOHD VEQAR UDDIN
Types of Facts controllers
Unified power flow controller
• Modern power systems are highly complex and are expected to fulfil
the growing demands of power wherever required, with acceptable
quality and costs.
• The necessity to deliver cost effective energy in the power market has
become a major concern in this emerging technology era. Therefore,
a desired power condition at the given points are best
achieved using power controllers such as the well known High Voltage
Direct Current (HVDC) and Flexible Alternating Current Transmission
System (FACTS) devices.
High Voltage Direct Current (HVDC) is used to transmit large amounts of
power over long distances. The factors to be considered are Cost, Technical
Performance and Reliability.
The voltage stability may be defined as the
ability of a power system to maintain steady
acceptable voltage at all busses in the system
at normal operating conditions and after being
subjected to disturbances.
The main factor causing voltage instability is the
inability of the power system to meet the
demands for reactive power in the heavily
stressed system keeping desired voltages.
There is a need to ensure stability and reliability
of the power system due to economic reasons.
• A large majority of power transmission lines
are AC lines operating at different voltages (10
kV to 800 kV). The distribution networks
generally op-erate below 100 kV.
• For bulk power upto 1000 MW and for long
distances >800 km we use HVDC transmission
of rating generally of ± 600 kV DC
• Power factor (PF) is the name
given to the ratio of the active
or usable power measured in
kilowatts (KW), to the total
power (active and reactive)
measured in kilovolt amperes
(KVA).ie: Power Factor = KW /
• Cosϕ = active power /
• DC systems often require a
smoothening of the direct current
wave shape to reduce losses and
improve system performance.
• Series reactors inserted in DC
systems offer this response and
additionally operate as current
limiting devices in the event of a
fault. Smoothing reactors are
widely used in industrial
applications and HVDC links.
Why HVDC ?
ADVANTAGES OVER AC :
It requires only 2 conductors as 3 in a.c tr
There is no skin effect
It has less corona
Voltage drop is less than ac
There are no stability problems
It has less losses
It is used in underwater(submarine) transmission
Basic HVDC circuit
TYPES OF HVDC LINKS:
BACK TO BACK
• Power electronic based systems and other static equipment that provide
controllability of power flow and voltage are termed as FACTS
• A flexible alternating current transmission system (FACTS) is a system
composed of static equipment used for the AC transmission of electrical
• It is meant to enhance controllability and increase power transfer
capability of the network. It is generally a power electronics-based
TYPES OF FACTS
Unified Power flow Controller
• The Unified Power Flow Controller (UPFC) is the most
versatile FACTS controller for the regulation of voltage and
power flow in a transmission line.
• It consists of two voltage source converters (VSC) one shunt
connected and the other series connected.
• The UPFC scheme consists of two basic switching power
converter namely shunt and series converters connected to
each other through a dc link capacitor.
• The controller can control active and reactive power flows in
a transmission line.
• MATLAB (matrix laboratory) is a numerical computing environment
and fourth-generation programming language. Developed byMathWorks,
MATLAB allows matrix manipulations, plotting of functions and data,
implementation of algorithms, creation of user interfaces, and interfacing
with programs written in other languages, including C, C++, Java,
• SIMULINK developed by MathWorks, is a data flow graphical programming
language tool for modeling, simulating and analyzing
multidomain dynamic systems. Its primary interface is a graphical block
diagramming tool and a customizable set of block libraries.
• Simulation is the imitation of the operation of a realworld process or system over time.
• The act of simulating something first requires that a
model be developed; this model represents the key
characteristics or behaviors of the selected physical or
abstract system or process.
• Simulation is also used when the real system
cannot be engaged, because it may not be
accessible, or it may be dangerous or unacceptable
to engage, or it is being designed but not yet built, or
it may simply not exist.
It controls the power flow in the transmission line, effectively.
Reduces the total harmonic distortion (THD) as well.
.Thus by using HVDC and The flexible ac
transmission system (FACTS) concepts stability
can be improved to the existing ac transmission
system, and unified power is maintained
• 1. E.M. Yap, Student Member, IEEE School of Electrical and
Computer Engineering, RMIT University, Melbourne, AU
• 2. Hideaki Fujita, Member, IEEE, Yasuhiro Watanabe, and Hirofumi
Akagi, Fellow, IEEE, “Control and Analysis of a Unified Power Flow
Controller” IEEE TRANSACTIONS
VOL. 14, NO. 6, NOVEMBER 1999
ON POWER ELECTRONICS,