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European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online:https://ejbss.org/ P a g e | 1450
TRANSIENT STABILITY IMPROVEMENT OF POWER
SYSTEMS USING UNIFIED POWER FLOW
CONTROLLER
ANTONY SARON DASS .D
PG Student,
PRIST Deemed to be University, Thanjavur
Abstract-. UPFC is one of the most widely used
FACTS device. To control (Kw) and (Kvar) in power
system FACTS devices are commonly used. In this
paper case study of 9 bus system is studied under the
symmetrical fault i.e. three phase fault in MATLAB
Simulink. Active power, reactive power and rotor
angle, angular speed during the fault is studied. Also
compared power in nine bus system using PI and
Fuzzy controller. Using Fuzzy controller power
oscillations damp out.
Keywords- MATLAB-Simulink, UPFC.
I. INTRODUCTION
In recent year the technology is advances so that
transmission network reliable and easy to design.
There are many technologies in interconnected power
system such as, HVDC and EHVAC. On other side as
power system network grow, the interconnected
network become increasingly more composite to
operate and system can be less protected for riding
through the major outages. The power system
interconnected network of today is large and
complex. There is widely use of microelectronic,
computers and high speed communication for control
and protection of present interconnected system.
The main purpose of FACTS is to improve system
controllability and to increase power system bound by
using power automated devices. Generally, FACTS
devices are more expensive than HVDC devices.
In case study consist of 3 generator nine bus
system having three load and three transformer. The
single line diagram of nine bus system as shown in
fig. 1.It is simple diagram of power system to
analyzed dynamic behavior and also power
oscillation damping. In this system three phase fault
is occurs at bus 8.Duration of fault time is 4 to 4.1
sec. After 4.1 sec. the fault is remove system try to
maintained stability, also active power, reactive
power and bus voltage of different buses is
calculated.
IV. ASSUMPTION IN TRANSIENT
STABILITY
I) Mechanical input is given to the synchronous
generator will be constant.
II) Effect of damper winding can be neglected.
III) The voltage at generator and at the bus are
assumed to be constant.
IV) Angular velocity of synchronous machine will
be assumed as constant.
Fig.1 Single Line Diagram of 9 Bus System
Single line diagram consist of 9 bus power system
having generator, load, transformer and transmission
line having length 50km. UPFC is connected between
buses 7 and 5. Duration of fault is 0.1 sec. After 4.1 sec.
the fault is removed.
The main constraint in a power system i.e. line
impedance (XL), terminal voltage (Vt) and rotor angle
(δ). The performance of system is studied and damping
of the oscillation in rotor angle (δ) and angular speed
(dw) is investigated in the three machine of nine bus
system.
Page 2 of 5
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online:https://ejbss.org/ P a g e | 1451
UPFC
The UPFC consist of two converter one is series converter
i.e. SSSC which inserts a voltage in series through a
transformer also the series branch of the UPFC can inject a
voltage with adjustable magnitude and phase angle it can
interchange kw power through the transmission line and
further shunt converter i.e. STATCOM , it is the most
adaptable of the device. It is to control the flow of Kw
and Kvar by inoculation of a voltage in series with
the transmission line. Magnitude of voltage and the
phase angle of the voltage can be diverse
independently.
Fig.2 Schematic diagram of UPFC
Static power electronics device consist of
capacitor and inductor etc. are used for compensation.
So after introduction of FACT devices give a control
on the compensation. FACT devices like STATCOM,
SVC,SSSC etc.
II. CONTROL OF THE SERIES CONVERTER
I) Direct voltage injection mode:-The converter
basically produces a voltage phasor in comeback to
the orientation input.
II) Phase Angle Shifter Emulation mode:- The
injected voltage is phase shifted comparative to the
voltage V by an angle definite by the reference input.
III) Line impedance emulation mode:- The series
injected voltage is measured in ratio to the line
current.
IV) Automatic power flow control mode:-The
reference inputs regulate the required real power (P )
and the reactive power (Q) on a definite place in the
line.
III. CONTROL OF THE SHUNT CONVERTER
I) VAR control mode:-The reactive current reference
is calculated by the inductive or capacitive VAR
command.
II) Automatic voltage control mode :-The reactive
current reference is calculated by the output of the
feedback voltage controller.
The 9 bus system contains 3 generator and 3 load
The Matlab simulation of 9 bus system is shown in
the Fig.3.
V. SIMULINK MODEL
Fig.3 Simulation Diagram of 9 Bus with UPFC System
VI. FUZZY LOGIC
The main components of a fuzzy logic controller.
The three main actions performed by a fuzzy logic
controller are:
• Fuzzification
• Fuzzy processing
• Defuzzification
Fig.4 Fuzzy logic control system
Page 3 of 5
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online:https://ejbss.org/ P a g e | 1452
Fig.5 Fuzzy Logic Controller
Fig. 6 FIS Fuzzy editor with 2 inputs & In fuzzy logic controller
there is one two input and one output having triangular membership
function .
Fig.7 Fuzzy rules used in the development of the fuzzy logic
coordination scheme
VII. SIMULATION RESULT
The MATLAB simulation result of the power system is shown in
the figure given below. The fault takes in between 4 to 4.1 sec.
After 4.1 sec the line is removed. Also Active Power, Reactive
Power and Bus Voltage is analyzed.
1.015
M/C 3
) 1. 0 1 M/C 2 ( p u
M/C 1
3 1.005
w 2 w w 1
1
0.995
0 2 4 6 8 1 0 12 14 16 18 20
1.5
) u
1
( p t 3 V t 2
10.5
V t V
0
0 2 4 6 8 1 0 12 14 16 18 20
4 0
M/C 3
g )
3 0 M/C 2
e ( d
2 0 12 t a e h
1 0 dt
0
0 2 4 6 8 1 0 12 14 16 18 20
Time
Fig.8 Angular Speed, Generator voltage and Rotor Angle without
UPFC.
1 8 0 0
Bus 4
1 6 0 0
Bus 5
Bus 6
Bus 7
1 4 0 0
Bus 8
Bus 9
1 2 0 0
W
1 0 0 0 ) (M o w e r
8 0 0
P A c t iv e
6 0 0
4 0 0
2 0 0
0
-2 0 0
0 2 4 6 8 10 12 14 16 18 20
