2016 Biennial International Conference on Power and Energy Systems:Towards Sustainable Energy (PESTS E)
Enhancement of Voltage Profile for IEEE 14 Bus
System with Inter line Power Flow Controller
IM.Venkateswara Reddy, 2 S ishnu Prasad Muni, 3 A.V.R.S.Sarma,
Research Scholar, EE, Dept., GM, P.E.S Dept., Professor (retd),
U.C.E, Osmania University, BHEL, (R&D), EE Dept., U.C.E, Osmania Uniersity,
Hyderabad, Telangana, India
e-mail:venkimallireddy@gmail.com, e-mail:bpmuni@bhelrnd.co.in, e-mail:avrs2000@yahoo.com
Abstract-- This paper deals with the design and simulation of
standard IEEE 14 bus system with IPFC. As a suggested
solution to effective load sharing between the transmission
lines, The interline power flow controller will transfers the
power demand from above
loaded line to less loaded
transmission line. The proposed IPFC was connected between
2, 3 and3, 4 buses of standard IEEE 14 bus system. In this
paper, two five level inverter based IPFC connected to the
main IEEE system was presented. The system was designed in
mat lab/Simulink and explained the effectiveness of power
transmission with and without presence of IPFC.
Key Words: IEEE 14 bus system, IPFC, VSC, Multi level
Inverter, FACTS, SSSC, TCSC, STATCOM
I.
[NTRODUCTION
FACTS Technology is related to real and reactive power.
It's used improve in the performance of power system. The
expertise deals with networks and consumers troubles
principally associated to power transmission quality issues.
Where a lot of power quality problems can be reduces with
an sufficient control of the power flow. The concept of
power flow control is concerned load support and voltage
compensation. Depending upon the power demand, the
tasks are to rise for the system power factor, to improve the
actual power from the generating source, to increase voltage
profile and to decrease harmonics. The principle of FACTS
is mainly depending upon the advanced technologies of
power electronic control and design procedure of the power
flow system, to control it by electronics devices. The
transmission can capitalize on the many thoughts taking
place in the area of high-current and high-voltage power
electronics, to get better be in command of power flows in
system during both normal and abnormal conditions.
The present reality of improving the power system
automatically controllable has initiated A change in the way
the design of power plant equipment and built as well as the
knowledge that goes into the planning and operation of
transmission and distribution networks. These type of
improvements may also increase the technique of energy
transmission are done, as increase in speed control of the
corridor of the energy flow is now practical Reactive power
support in transmitting the power in different power flows
increases the strength of the power system by transfer it at
maximum level. Series compensators change the parameters
of the transmission grids or distribution levels, where the
978-1-4673-6658-8116/$3l.00 ©20 16 IEEE
shunt compensators change the impedance at the connected
terminals. [n both cases, the reactive power through the
system can significantly transfers and improves the
performance of the entire power system. The use of PWM
converters by a control action allows the achievement of
static series compensators for generating or consuming
reactive power faster than the fundamental system period.
FACTS are more efficient for the operation of power flow
networks. From above concepts, static Power flow was
controlled by the control actions of FACTS devices, which
include the following
•
•
•
•
•
•
Fixed VAR Compensators
TCSC
STATCOM
Static Series Synchronous Compensators (SSSC)
UPFC
[PFC
[I.
[EEE
Bus SYSTEM
A. Bus Classification
In general, a bus in an electrical power system is fed
from the generating units which inject the active and
reactive power into it and loads real and reactive power s
from it. [n load flow studies, the generator and load
(complex) powers are lumped into a net power. This net
power is called bus injected power.
The net power injected in the bus is given by
(I)
l)Load Bus
Generators are not linked to this bus. At this bus the
active and reactive power are specified. Its desired to
determine the magnitude and phase angle of voltage through
load flow study. The P D demand and QD should specify at
such a bus and this bus voltage can be allowed to differ
within the allowable values. i.e,5%. Also bus voltage phase
angle is not very important for the load.
2) Generator Bus or Voltage Controlled Bus
The generator bus voltage bus is one at which the
voltage magnitude corresponding to the generation voltage
and active power (P G) specified. It's required to calculate
the QG and voltage phase angle.
3) Slack (Swing) Bus
This type of bus differs from other buses by the fact
active and reactive powers at this bus were not specified but
voltage and phase angle are mentioned. Mainly only one bus
is present in a given system.
Initially the real and reactive powers are not specified at
all buses, so complex power flow in the system is not
known .the power loss also unknown up to completion of
flow solution. So it's necessary having one bus at which the
complex power is unspecified, so that it will supplies the
difference in the total system load and losses. By this reason
it must be a generator bus.
equipment life time will be shorted, and if the supplied
voltage below the rated value the equipment will not
function properly.
@GENERATORS
@SYNCHRONOUS
12
COMPENSATORS
TABLE 1. DIFFERENT Bus SYSTEM QUANTITIES
S.No
Bus
Type
Specified
Quantities
Can be
Determined
Quantities
I
Load
bus
P,Q
IVI,6
2
Genera
tor bus
P, IVI
Q,6
3
Slack
bus
IVI,6
P,Q
F ig.l. IEEE 14 bus system
B. Standard IEEE i4 Bus System
The fig. 1 shows the standard IEEE 14 bus system. The
generators are connected at 1 and2 buses and synchronous
compensators are connected at 3, 6 buses and i h bus acts as
slack bus
The moving reactive powers in transmission line are
one of the major factor in loss of energy. From voltage
standard that made by IEC the voltage range that be allow to
provide to customer are ±6% from the rated voltage value.
C. Necessity ofImproving Voltage Profile
E. Methods for improvement of Voltage Profile
Voltage collapses mainly occur in power system sudden
increase in system load or by different faults or shortage in
supply of reactive power. Voltage fall down causes more
problems in the entire system, mainly system instability. In
fact, sudden change in system voltage involves change in a
whole power system. Voltage fall down is typically related
with reactive power demand of load not being met due to
shortage in production in reactive power and its
transmission. Mainly,discussed on the effects of the IPFC
on voltage profile, active and Reactive powers. The IPFC
mainly consists of two series connected voltage controlled
converters for exchange of powers between more no of
power lines when ever is the load changes in the lines.
In bus system the voltage profile can be improved as
follows
D. Voltage Control
In power system, control the system voltage play
important role to ensure the voltage interruption like swell,
sag and harmonic can be minimize and further more
increase the power quality, reliability and availability. The
importance of voltage control as follows
Both customers and power system equipment is design
to operate within the specific voltage range value. If the
equipments are supplied by voltage above their range then
1) By injecting the reactive power (static shunt capacitors
and reactor or by static series capacitors and or synchronous
compensators.
2) By using tap changing transformer.
3) By using FACTS devices.
4) By exchange of powers between the lines (IPFC)
F. Applications ofiPFC
The major objective in applying IPFC is to exchange
power demand from excess loaded line to below loaded line
by series compensation (by exchanging of powers between
the lines). The devices will works as controllable voltage
source devices which are connected in series with the
system in for increase series compensation.
G. Advantages o{Series Compensation
1) Decreases the voltage drops at loads
2) Influences power flow in parallel lines
3) Capability of power transmission increases
4) Transmission angle is less
5) Stability increases
6) Line voltage drops will be low
III.
V1s
V1 self
VX1
V1r
INTER LINE POWER FLOW CONTROLLER
In general, the IPFC is a grouping of two or more
separately controllable SSSCS which are solid-state VSCS.
Vi
Vj
r-----------------~
v~Vl iJ::':"1f "-:
V2r
~--~~~-+-------~------~­
X2
V2pq
Fig.3. Basic two inverter power f10w controller
SSSC I
Fig.2. Simple schematic of IPFe
These are mainly injecting sinusoidal voltage at
changeable level and connect via a general DC link as
shown in fig.2. Usually SSSC is used to increase the
transmittable real power over a specified line and to
equilibrium the loading of a normally encountered multiline system. They are mainly to provide ability for direct
transfer of real power between compensated lines while
maintaining the preferred division of reactive flow among
the lines. In general form, the IPFC having a number of dc
to. ac converters, each providing series compensation for a
different line. The converters are linked together at their
Capacitor terminals and connected to the AC systems
through their series coupled transformers. With this scheme
in addition to provided that series reactive compensation,
any converter capacitors can For an IPFC with n series
converters, the control degree n-l of series converters is
two, apart from that one series converter has control degree
is one be controlled to supply of active power to the general
dc link from its own line.
The exchange of real power at any time among the n
series converters should be balanced. For the sake of
effortlessness, consider basic model of IPFC. In following
fig.3. Each converters are connected together at their dc
terminals with this method series reactive compensation
taken place, in addition to this any of the VSC can be
controlled to supply real power to the dc link connected at
common position from its own line. Due to this process an
overall extra power can be transferred from the lower
demanded lines which can be used by other lines for real
power requirement. Obviously this process maintains the
overall power balance at the capacitor terminals by proper
control action. A simple IPFC scheme consisting of two
VSCS is used as a main control device to add the required
power to over loaded transmission line by series voltage
addition. Two VSCS, with voltage phasors VII" and V2 rx" in
series with transmission linesl and 2 respectively are in
below Fig.3.
A. Working Principle and Voltage Phasor for IPFC
DC link voltage can be maintained with controllable
voltage magnitude and phase angle at the fundamental
frequency at a required level. The dc link is represented by a
bidirectional link for real power exchanging between VSCS.
Fig.4. Phasor diagram of system 1
The representation of line as follows, line one represented
by resistance R reactance Xl Sending end bus voltage Vb
and a receiving end voltage VIC' For second line sending end
represented by resistance, reactance R2 X2 • Sending end
voltage V2S and the receiving-end voltage is V 2,. at normal
operating conditions the sending-end and receiving-end
voltages of two lines assumed to be equal with fixed
magnitudes in per units and with fixed angles ensuing in
same transmission angle for the two lines.
j
The line impedances and voltages are assumed to be
identical. Although in practice two systems could be
somewhat different in all line parameters. For simplicity
purpose line1 is randomly chosen to be the prime system for
which free controllability of both line powers flow is fixed
to derive the line constraints. Due to easy control of line one
forces on power flow control of line 2. The following figure
is more useful to explain the working principle and voltage
compensation of line I
B. Voltage Source Converter
A five level voltage source converter was connected to
the each transmission line. Depending upon the power
demand transfer VSC I and vsc2 will works as converter or
inverter vice versa. VSC I works as main controller and vsc2
will work as slave controller. The capacitors will act as dc
bus. The dc bus voltage controlled by vsc2. The harmonic
content was reduced by high level inverter. The proposed
[PFC was connected between bus 3 and bus 4 of [EEE 14
bus system.
[v.
@ GENERATORS
(£) Sl'NCHRONOUS
12
"L~
COMPENSATORS
7
PROPOSED SYSTEM SIMULATION
This section briefly describes about the test system that
is used to analyze the work in purpose of analyze the effect
ofIPFC in increasing the voltage stability of the system and
power demand exchange and its control. IEEE 14 bus
system was taken and it is designed by using Power System
Analysis Toolbox (PSAT).The [PFC was connected
between second, third and fourth busses of the system .Then
compared the results with and without [PFC and tabulated
the bus voltage, bus voltage angle, real and reactive Power
at all busses.
Fig.5. IEEE 14 bus system with IPFC
Table II. IEEE 14 bus system with IPFC, Table III.
IEEE 14 bus system without IPFC, Table IV. IEEE 14 bus
system line parameters, FigA shows the IEEE 14 bus
system with IPFC.
TABLE II.IEEE 14 Bus SYSTEM WITH IPFC
TABLE III. IEEE 14 Bus SYSTEM WITHOUT IPFC
S.no
Bus
no
Bus
voltage
(pu)
Volta
ge
angle
Real
power
Reactive
power
I
I
1.06
0
2.32e8
-1.523e 7
2
2
1.045
-4.989
1.83e7
3
3
1.01
-12.75
-9.42e7
4
4
1.013
-10.24
-4.78e7
5
5
1.017
-8.76
-7.6e6
0
Bus
no
Bus
voltage
(pu)
Voltage
angle
Real
power
Reactive
power
1
1
1.075
0
2.507e"
-1.21e7
2
2
1.052
-3.166
2.015e 7
2.986e 7
3
3
1.021
-10.06
-1.001 e"
6.446e6
4
4
1.023
-8.57
-5.16e"
2.6e"
6
6
1.07
-14.45
-1.l2e7
5
5
1.02
-6.457
-9.26e"
-1.02e"
7
7
1.046
-13.24
0
0
6
6
1.085
-12.99
-1.365e 7
1.298e7
8
8
1.08
-13.24
2.387e7
2.l03e 7
S.n
7
7
1.052
-11.28
0
0
8
8
1.085
-11.28
2.096e·7
1.965e7
9
9
1.03
-14.82
-2.95e7
9
9
1.045
-12.25
-3.125e7
-l.396e7
10
10
1.03
-15.04
-ge6
10
10
1.04
-13.9
-1.005e 7
-4.5e6
11
11
1.046
-14.86
-3.5e6
II
II
1.052
-12.65
-4.2e
-1.1 e
12
12
1.053
-15.3
-6.1e6
12
12
1.061
-13.28
-7.285e"
-Lie"
13
13
1.051
-13.66
-1.506e7
-4.985e"
13
13
1.047
-15.33
-l.35e7
14
14
1.024
-14.1
-1.526e 7
-3.5e6
14
14
1.019
-16.09
-1.4ge7
6
3.523e7
8.758e 6
3.ge6
-1.6e 6
1.553e7
-1.66e 7
-5.8e 6
-1.8e 6
6
-1.6e 6
-5.8e 6
_5e 6
8
TABLE IV. IEEE 14 Bus SYSTEM LINE PARAMETERS
S.
NO
FROM
BUS
TO
BUS
R(PU)
x (PU)
B/2
(PU)
I
I
2
0.01938
0.05917
0.0264
2
I
5
0.05403
0.22304
0.0246
3
2
3
0.04699
0.l9797
0.0219
4
2
4
0.05811
0.17632
0.0170
5
2
5
0.05695
0.17388
0.0173
assist in the transmISSIOn system. The behavior of the
system under various transient and load changes at the
receiving-end of the transmission system are presented and
analyzed. The design of an IEEE 14 bus system with and
without IPFC has demonstrated. The system was designed
in the mat lab/simlink.The flexible control of active/reactive
power to assist in the transmission system behavior with
FACTS devices. The voltage, voltage angle, real and
reactive powers at 14 buses tabulated and compared at each
level. By the series compensation by IPFC The power
handling capacity and voltage profile increased in all buses
of the system.
6
3
4
0.06701
0.17103
0.0064
REFERENCES
7
4
5
0.01335
0.04211
0.0
8
4
7
0
0.20912
0.0
9
4
9
0
0.55618
0.0
10
5
6
0
0.25202
0.0
II
6
II
0.09498
0.19890
0.0
12
6
12
0.12291
0.25581
0.0
13
6
13
0.06615
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7
8
0
0.17615
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[6]
[7]
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[9]
The IPFC was Connected between the 2, 3 4 buses. The
tie line between 3, 4 buses will act as transmission line 1
and tie line between 2, 4 buses will act as transmission line
2 for IPFC. Two different loads are connected to the
transmission lines (1 and 2) of the IPFC. Load 1 will
continuously acts on the two lines. Load 2 variation will
take place at different times for the two transmission lines.
For line one extra load added at 0.1 s to 0.2 sec. this power
was supplied by the line 2. For line 2 extra load added at
O.2Ss to 0.3 sec., this power was supplied by the line 1.
V. CONCLUSION
The study of an IPFC system with two parallel lines has
demonstrated the flexible control of active/reactive power to
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