Power flow solution with flexible ac transmission system devices

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME
232
POWER FLOW SOLUTION WITH FLEXIBLE AC TRANSMISSION
SYSTEM DEVICES
Guguloth Ramesh1
and T. K. Sunil Kumar2
1
Guguloth Ramesh, Research Scholar is with EED, the National Institute of Technology Calicut,
Kerala-673601, and INDIA
2
Dr.T.K. Sunil Kumar.Assistant Professor is with EED, the National Institute of Technology Calicut,
Kerala-673601, and INDIA
ABSTRACT
Power flow analysis is the backbone of power system analysis and design. It is necessary for
planning, operation, economic scheduling and exchange of power between utilities. This paper
proposes load flow solution under steady state condition with flexible AC transmission system
(FACTS) devices. FACTS technology opens up new opportunity for operation and control of power
system. Out of the various FACTS devices Thyristor Controlled Series Capacitor (TCSC) and
Unified Power Flow Controller (UPFC) are the right choices for the maximization of power flow in
power system, which has been selected to control power flow in the transmission lines. TCSC is
used to minimize active power losses and UPFC is minimizing both real and reactive power losses in
the system. Test bus system is modeled and simulated using MATLAB (Power System Analysis
Toolbox).
Keywords: Load Flow Analysis, FACTS, TCSC and UPFC.
NOMENCLATURE
FACTS Flexible AC Transmission Systems
TCSC Thyristor Control Series Capacitors
UPFC Unified Power Flow Controller
ܲ௜௝ Real Power Flow from ݅௧௛
Bus to ݆௧௛
Bus
ܳ௜௝ Reactive Power Flow from ݅௧௛
to ݆௧௛
Bus
ܸ௜ , ܸ௝ Voltage Magnitudes at ݅௧௛
and ݆௧௛
Bus
ߜ௜ , ߜ௝ Angles of voltage at ݅௧௛
and ݆௧௛
Bus
‫ܤ‬௜௝ , ‫ܩ‬௜௝ Suceptance and Conductance of the lines
ܲ௝௜ Real Power Flow from ݆௧௛
to ݅௧௛
Bus
INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &
TECHNOLOGY (IJEET)
ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 4, Issue 4, July-August (2013), pp. 232-244
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233
ܳ௝௜ Reactive Power Flow from ݆௧௛
to ݅௧௛
Bus
R Total Resistance in the Transmission Line
ܺ௅, ܺ஼ Line Reactance and Capacitance
ܺ௦௘, ܺ௦௛ Series and Shunt Sides Line Reactance
‫ܫ‬௠ Transmission Line Current
ܸூ
ഥ Voltage Due to Series Compensation
ܲ௅, ܳ௅ Real and Reactive Power Losses
்ܺ஼ௌ஼ Reactance of TCSC
ܺ஼ Capacitive Reactance
I. INTRODUCTION
Load flow solution is a solution of the power system network under steady state condition
subject to certain inequality constraints under which system operates. The load flow solution gives
the nodal voltages and phase angles and hence the power injection at all the buses and power flows
through interconnecting power transmission lines [1]. Load flow solution is essential for designing a
new power system and for planning extension of the existing one for increased load demand. These
analyses require the calculation of numerous load flows under both normal and abnormal operating
conditions.
IEEE 14 bus system is modeled in deregulated environment. Conventional techniques for
solving the load flow problem are iterative method using the Newton-Raphson method [2]-[3].
An opening of unused potentials of transmission system due to environmental, right-of-way
and cost problems is a major concern of power transmission network expansion planners and policy
makers. Flexible AC Transmission Systems (FACTS) controllers can be helpful in utilizing the
maximum capacity of the transmission network to their limits without threatening the stability and
security of the network. FACTS controllers [4] provide new control facilities, both in steady state
power flow control and dynamic stability control. The possibility of controlling power flow in an
electric power system without generation rescheduling or topological changes can improve the
performance considerably [5]. The TCSC and UPFC, the most versatile devices have been selected
to minimize losses in transmission lines [6]-[7].
TCSC allows rapid and continuous changes of the transmission line impedance. Active power
flows along the compensated transmission line can be maintained at a specified value under a range
of operating conditions. In load flow studies the TCSC can be represented in several forms. For
instance, the model presented in [8]-[9] is based on the concept of a variable Series Compensator
whose changing reactance adjusts it in order to constrain the power flow across the branch to a
specified value. The reactance value is determined efficiently by means of Newton's method [10].
Among FACTS devices, the unified power flow controller (UPFC) is emerging as a promising
solution for improving power system characteristics for its high degree of controllability of many
power system variables [11]. UPFC can be used for power flow control, loop-flow control, load
sharing among parallel corridors, enhancement of transient stability, mitigation of system oscillation,
voltage regulation and reduced losses in the system [12]-[13].This analysis is based on comparison
of the results in every line before and after installation of UPFC in a test system [14]-[15]. Present
paper IEEE 14 bus ill condition system is modeled, the limit violation in the transmission lines are
predicted with power flow solution and remedial action is taken by FACTS devices.
This paper is organized as follows: Section II deals with load flow solution. Section III
presents Thyristor Controlled Series Capacitor (TCSC). Section IV describes Unified Power Flow
Controller (UPFC). Section V presents simulations results at various operating conditions. Section
VI concludes the paper.

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issu
II. LOAD FLOW SOLUTION
The power flow solution is an importan
system. Unlike traditional circuit analysis, a power flow study usually uses simplified notation such
as a one-line diagram and per-unit system, and focuses
real and apparent) rather than voltage and current. The advantage in studying power flow analysis is
in planning the future expansion of power systems as well as in determining the best operation of
existing systems.
Fig.1 shows line diagram of IEEE 14 bus system, which is modeled in MATLAB power
system analysis toolbox. Power flow analysis is being used for solving power flow problem by
Newton-Raphson method. Information obtaine
voltage at each bus, real and reactive
II.1 Newton-Raphson Method
The Newton-Raphson method is widely used for solving non
the original non-linear problem into a sequence of linear problems whose solutions approach the
solutions of the original problem.
Let G=F(x, y) be an equation where the variables
is a specified quantity. If F is non-linear in nature there may not be a direct solution to get the values
of x and y for a particular value of
iteratively solve for the real values of
calculated value of F (using the estimates of x and y) i.e
procedure is as follows: let the initial estimate of
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976
6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME
234
The power flow solution is an important tool involving numerical analysis applied to a power
unit system, and focuses on various form of AC power (i.e.
Fig.1 IEEE 14 bus system
diagram of IEEE 14 bus system, which is modeled in MATLAB power
Power flow analysis is being used for solving power flow problem by
Raphson method. Information obtained from load flow problem is magnitude and angle of
voltage at each bus, real and reactive power at each line and each bus, and losses in the system.
Raphson method is widely used for solving non-linear equations. It
linear problem into a sequence of linear problems whose solutions approach the
be an equation where the variables x and y are the arguments of
linear in nature there may not be a direct solution to get the values
for a particular value of G. In such cases, we take an initial estimate of
iteratively solve for the real values of x and y until the difference is the specified value of
(using the estimates of x and y) i.e. ∆F is less than a tolerance value. The
let the initial estimate of x and y is and respectively,
August (2013), © IAEME
tool involving numerical analysis applied to a power
various form of AC power (i.e. reactive,
diagram of IEEE 14 bus system, which is modeled in MATLAB power
Power flow analysis is being used for solving power flow problem by
d from load flow problem is magnitude and angle of
power at each line and each bus, and losses in the system.
linear equations. It transforms
linear problem into a sequence of linear problems whose solutions approach the
are the arguments of function F. G
linear in nature there may not be a direct solution to get the values
n such cases, we take an initial estimate of x and y and
is the specified value of G and the
is less than a tolerance value. The

235
Using Taylor series,
‫ܩ‬ ൌ ‫ܨ‬ሺ‫ݔ‬଴
, ‫ݕ‬଴ሻ ൅ ቚ
డி
డ௫
ቚ
௫బ,௬బ
. ∆‫ݔ‬ ൅ ቚ
డி
డ௬
ቚ
௫బ,௬బ
. ∆‫ݕ‬ (1)
where
డி
డ௫
and
డி
డ௬
are calculated at x଴
, y଴
‫ܩ‬ െ ‫ܨ‬ሺ‫ݔ‬଴
, ‫ݕ‬଴ሻ ൌ ∆‫ܨ‬ ൌ
డி
డ௫
. ∆‫ݔ‬ ൅
డி
డ௬
. ∆‫ݕ‬ (2)
In the matrix form it can be written as
∆‫ܨ‬ ൌ ቀ
డி
డ௫
డி
డ௬
ቁ ቀ∆௫
∆௬
ቁ (3)
or
ቀ∆௫
∆௬
ቁ ൌ ݅݊‫ݒ‬ ቆቀ
డி
డ௫
డி
డ௬
ቁቇ ሺ∆‫ܨ‬ሻ (4)
After the first iteration x is updated to ‫ݔ‬ଵ
= ‫ݔ‬଴
+ ∆‫ݔ‬ and y to ‫ݕ‬ଵ
= ‫ݕ‬଴
+ ∆‫ݕ‬. The procedure is
continued till after some iteration both ∆F is less than some tolerance value ε. The values of x and y
after the final update at the last iteration is considered as the solution of the function F. For the load
flow solution, the non-linear equations are given by equation (3). There will be 2n – 2 – p such
equations, with n being the total number of buses and p the number of PV and generator buses.
ቀ∆௉
∆ொ
ቁ ൌ ቆ
ങು
ങഃ
ങು
ങ|ೇ|
ങೂ
ങഃ
ങೂ
ങ|ೇ|
ቇ ቀ ∆ఋ
∆|௏|
ቁ (5)
or
ቀ ∆ఋ
∆|௏|
ቁ ൌ ݅݊‫ݒ‬ ቆ
ങು
ങഃ
ങು
ങ|ೇ|
ങೂ
ങഃ
ങೂ
ങ|ೇ|
ቇ ቀ∆௉
∆ொ
ቁ (6)
The matrix of equation (6) consisting of the partial differentials, is known as the Jacobian
matrix and is very often denoted as J.∆P is the difference between the specific value of P (ܲௌ௉
) and
the calculated value of P using the estimates of δ and |V| in a previous iteration. We calculate ∆Q
similarly.
The Newton power flow is the most robust power flow algorithm used in practice. However,
one drawback to its use is the fact that the terms in the Jacobian matrix must be recalculated each
iteration, and then the entire set of linear equations in equation (6) must also be resolved each
iteration. Since thousands of complete power flow are often run for planning or operations study,
ways to speed up this process were devised.
III. THYRISTOR CONTROLLED SERIES CAPACITORS
It is basically variable impedance, such as capacitor or inductor etc. Series controller injects
voltage in series with the line. As long as the voltage is in phase quadrature with line current, the

236
series controller only supplies or absorb variable reactive power. The value of reactance of TCSC (
்ܺ஼ௌ஼) is function of the reactance of the line,ܺ௅ where the device is located.
Fig.2 Equivalent circuit of TCSC
The real and reactive power flow from bus i to bus j can be expressed as
ܲ௜௝ ൌ ܸ௜
ଶ
‫ܩ‬௜௝ – ܸ௜ܸ௝‫ܩ‬௜௝ cos൫ߜ௜ െ ߜ௝൯ െ ܸ௜ܸ௝‫ܤ‬௜௝ sin൫ߜ௜ െ ߜ௝൯ (7)
ܳ௜௝ ൌ ܸ௜
ଶ
൫‫ܤ‬௜௝ െ ‫ܤ‬௦௛൯ െ ܸ௜ܸ௝‫ܩ‬௜௝ sin൫ߜ௜ െ ߜ௝൯ ൅ ܸ௜ܸ௝‫ܤ‬௜௝ cos ൫ߜ௜ െ ߜ௝൯ (8)
Similarly, the real and reactive power flow from bus j to bus i can be expressed as
ܲ௝௜ ൌ ܸ௝
ଶ
‫ܩ‬௜௝ – ܸ௜ܸ௝‫ܩ‬௜௝ cos൫ߜ௜ െ ߜ௝൯ ൅ ܸ௝‫ܤ‬௜௝ sin൫ߜ௜ െ ߜ௝൯ (9)
ܳ௝௜ ൌ െ ܸ௝
ଶ
൫‫ܤ‬௜௝ െ ‫ܤ‬௦௛൯ ൅ ܸ௜ܸ௝‫ܩ‬௜௝ sin൫ߜ௜ െ ߜ௝൯ ൅ ܸ௜ܸ௝‫ܤ‬௜௝ cos ൫ߜ௜ െ ߜ௝൯ (10)
The active and reactive power loss on each line k can be formulated as
ܲ௅௞ ൌ ܲ௜௝ ൅ ܲ௝௜ ൌ ܸ௝
ଶ
‫ܩ‬௜௝ ൅ ܸ௜
ଶ
‫ܩ‬௜௝ െ 2ܸ௜ܸ௝‫ܤ‬௜௝ cos ൫ߜ௜ െ ߜ௝൯ (11)
ܳ௅௞ ൌ ܳ௜௝ ൅ ܳ௝௜ ൌ െ ܸ௜
ଶ
൫‫ܤ‬௜௝ െ ‫ܤ‬௦௛൯ െ ܸ௝
ଶ
൫‫ܤ‬௜௝ െ ‫ܤ‬௦௛൯ ൅ 2ܸ௜ܸ௝ cos ൫ߜ௜ െ ߜ௝൯ (12)
Fig.2 shows a model of transmission line with TCSC connected between buses i and j. The
transmission line is represented by its lumped π-equivalent parameters connected between the two
buses. During steady state operation, the TCSC can be considered as a static reactanceെ݆ܺ஼. The
controllable reactance ܺ஼ is directly used as the control variable in the power flow equations.
IV. UNIFIED POWER FLOW CONTROLLER

237
A unified power flow controller (UPFC), which has the capabilities of voltage regulation,
series compensation, and phase shifting, is one of the most versatile FACTS controllers.
Fig.3 the UPFC model in PSAT
It can independently and very rapidly control both real and reactive power flows in a
transmission line. This paper focuses on the representation of UPFCs in power flow computations. It
gives a novel approach to include such devices in power flow studies.
The UPFC model in PSAT is shown in Figure .3, according to this figure, there are some
parameters that can be adjusted for keeping voltage level and power flow of the network. The related
formulae are described below: the real and reactive power flow from ݅௧௛
Bus to ݆௧௛
Bus
ܲ௜௝ ൌ ܲ௦௛ ൅ ܴ݁ ൛ܸ௞‫ܫ‬௠
തതതതതത‫כ‬
ൟ
(13)
ܳ௜௝ ൌ ܳ௦௛ ൅ ‫݉ܫ‬ ൛ܸ௞‫ܫ‬௠
ൟ
Similarly the real and reactive power flow from ݆௧௛
Bus to ݅௧௛
Bus
ܲ௝௜ ൌ െ ܴ݁ ൛ܸ௞‫ܫ‬௠
ൟ
(14)
ܳ௝௜ ൌ െ ‫݉ܫ‬ ൛ܸ௞‫ܫ‬௠
ൟ
The real and reactive power ܲ௦௛and ܳ௦௛absorbed by the shunt side are:
ܲ௦௛ ൌ ܸ௜‫ܩ‬௦௛ െ ݇௦௛ܸௗ௖ܸ௜‫ܩ‬௦௛ܿ‫ݏ݋‬ሺ‫ݒ‬௜െ ‫ן‬ሻ െ ݇௦௛ܸௗ௖ܸ௜‫ܤ‬௦௛ ‫݊݅ݏ‬ሺ‫ݒ‬௞െ ‫ן‬ሻ (15)
ܳ௦௛ ൌ െܸ௜
ଶ
‫ܤ‬௦௛ ൅ ݇௦௛ܸௗ௖ܸ௜‫ܤ‬௦௛ܿ‫ݏ݋‬ሺ‫ݒ‬௜െ ‫ן‬ሻ െ ݇௦௛ܸௗ௖ܸ௜‫ܩ‬௦௛ ‫݊݅ݏ‬ሺ‫ݒ‬௞െ ‫ן‬ሻ (16)
and the current ‫ܫ‬௠
തതതand the voltage ܸതdue to seriescompensations:
‫ܫ‬௠
തതത ൌ
ሺଵି௔భതതതതሻ൫௏ഢഥି௏ണഥ ൯ି௔మതതതത௏಺തതത
ோା௝௑ಽ
(17)

238
ܸത ൌ ܽଵതതത൫ܸప
ഥ െ ܸఫ
ഥ൯ ൅ ܽଶതതതܸூ
ഥ (18)
Where
ܸூ
ഥ ൌ ݇௦௘ܸௗ௖݁௝ఉ
(19)
ܽଵതതത ൌ െ
ோೞ೐ା௝௑ೞ೐
ሺோି ோೞ೐ሻାሺ௑ಽି ௑ೞ೐ሻ
(20)
ܽଶതതത ൌ െ
ோೞ೐ା௝௑ೞ೐
ሺோି ோೞ೐ሻାሺ௑ಽି ௑ೞ೐ሻ
(21)
According to above equations, this model of UPFC is applied to a transmission line in the
system to obtain the different results with and without UPFC, and the results are analyzed.
V. SIMULATION RESULTS
The load flow solution for IEEE 14 bus system has been modeled in MATLAB power system
analysis tool box. All the results are analyzed under ill condition system, and with FACTS devices.
Fig.4 IEEE 14 Bus system is modeled in MATLAB (PSAT)
Figure.4 shows the modeled IEEE 14 bus system, which contained 5 generators, 11 loads, 4
transformers, 20 transmission lines, operating at 50 Hz frequency and base is 100 MVA.
The power flow solution after the simulation is given in the Table I. The real and reactive
power generation and demand at each bus, total real and reactive power losses in the system are
obtained.

239
TABLE I
Normal case
Bus
No
P (MW)
Gen
P (MW)
Load
Q (MVAR)
Gen
Q (MVAR)
Load
1 352.16 0 -27.5115 0
2 40 30.38 96.484 17.78
3 0 131.88 60.6285 26.6
4 0 66.92 0 5.6
5 0 10.64 0 2.24
6 0 15.68 46.1577 10.5
7 0 0 0 0
8 0 0 30.0037 0
9 0 41.3 0 23.24
10 0 12.6 0 8.12
11 0 4.9 0 2.52
12 0 8.54 0 2.24
13 0 18.9 0 8.12
14 0 20.86 0 7
Total 392.16 362.60 205.76 113.98
Loss ࡼࡸ = 29.56[MW] ࡽࡸ= 91.80[MVAR]
(a) (b)
(C)
Fig.5 Voltage magnitude in p. u(a), Real power profile in MW (b), Reactive power profile in
MVAR(c)at each bus

240
The total real power demand is 362.60 (MW) against real power generation in system is
392.16 (MW) and real power loss is 29.56 (MW). The total reactive power demand is 113.98
(MVAR) against total reactive power generation in system is 205.76 (MVAR) and reactive power
loss is 91.80 (MVAR). In this system the active and reactive power limits violation in line 11
(connected between buses 1-2) and line 14 (connected between buses 1-5) are observed, which have
been selected to connect the FACTS devices in the system. To minimize limit violation as well as
losses in the system, the FACTS (TCSC, UPFC) are used, which help the transmission line to
maintain within the limits, minimize losses, and increase transmission line transfer capabilities. The
results of system without and with FACTS devices are analyzed in the subsections.
V.1 IEEE 14 system with TCSC
Table II, shows results of line flows with TCSC connected in the system.
TABLE II
Line flows
Line
Without TCSC TCSC b/w
Bus 1-2
TCSC b/w
Bus 1-5
From
Bus
To
Bus
P
Loss
MW
Q
Loss
MVA
R
P
Loss
MW
Q
Loss
MVA
R
P
Loss
MW
Q
Loss
MVA
R
0 2 05 1 1.82 2.00 2.01 2.58 1.51 1.00
06 12 2 0.17 0.35 0.17 0.35 0.16 0.35
12 13 3 0.02 0.02 0.02 0.02 0.02 0.02
06 13 4 0.55 1.09 0.55 1.09 0.55 1.08
06 11 5 0.31 0.66 0.31 0.66 0.30 0.63
11 10 6 0.14 0.33 0.14 0.33 0.13 0.30
09 10 7 0.00 0.01 0.00 0.01 0.00 0.00
09 14 8 0.13 0.28 0.13 0.28 0.13 0.28
14 13 9 0.27 0.56 0.27 0.56 0.26 0.54
07 09 10 0.00 2.61 0 2.62 0 2.61
01 02 11 10.2 25.5 0 27.7 9.31 22.5
03 02 12 4.73 15.3 4.83 15.7 4.53 14.4
03 04 13 0.97 -0.9 0.91 -1.1 0.97 -1.0
01 05 14 5.96 19.3 5.23 16.3 0 25.7
05 04 15 0.89 1.53 0.82 1.31 0.97 1.76
02 04 16 3.25 5.97 3.44 6.55 2.93 4.97
04 09 17 0 0.57 0.00 0.58 0.00 0.59
05 06 18 0 10.6 0 10.5 0 10.6
04 07 19 0 4.15 0 4.17 0 4.09
08 07 20 0 1.68 0 1.68 0 1.48
Total Losses 29.5 91.8 18.9 92.1 21.8 92.2

241
Without TCSC the losses in the system is 29.5 (MW) and 91.8 (MVAR). With TCSC
connected in the line 11 (between buses 1-2) the real power loss reduced from 29.5 to 18.9 (MW)
and the reactive power loss approximately remains same, when the TCSC connected in the line 14
(between buses 1-5) the real power loss reduced from 29.5 to 21.8 (MW) and the reactive power loss
approximately remains same. The location of TCSC as in line 11 gives more advantage than as in
line 14. TCSC can minimize only real power not reactive power losses, and limit violation in the
system.
V.2 IEEE 14 system with UPFC
Table III, shows results of line flows with UPFC connected in the system. Without UPFC the
losses in the system is 29.5 (MW) and 91.8 (MVAR). With UPFC connected in the line 11 (between
buses 1-2), the real power loss reduced from 29.5 to 18.6 (MW) and the reactive power loss from
91.8 to 87.5 (MVAR).When the UPFC connected in the line 14 (between buses 1-5) the real power
loss reduced from 29.5 to 20.0 (MW) and the reactive power loss from 91.8 to 86.9 (MVAR). The
location of UPFC as in line 11 gives more advantage than in line 14. UPFC can minimize both real
power and reactive power losses, and limit violation in the system.
TABLE III
Line flows
Line
Without UPFC UPFC b/w
Buses 1-2
UPFC b/w
Buses 1-5
From
Bus
To
Bus
P
Loss
MW
Q
Loss
MV
AR
P
Loss
MW
Q
Loss
MVA
R
P
Loss
MW
Q
Loss
MVA
R
0 2 05 1 1.82 2.00 2.17 3.08 1.19 0.02
06 12 2 0.17 0.35 0.17 0.35 0.16 0.35
12 13 3 0.02 0.02 0.02 0.02 0.02 0.02
06 13 4 0.55 1.09 0.55 1.09 0.55 1.08
06 11 5 0.31 0.66 0.31 0.65 0.30 0.63
11 10 6 0.14 0.33 0.14 0.32 0.13 0.30
09 10 7 0.00 0.01 0.00 0.01 0.00 0.00
09 14 8 0.13 0.28 0.13 0.28 0.13 0.27
14 13 9 0.27 0.56 0.27 0.56 0.26 0.54
07 09 10 0.0 2.61 0 2.62 0 2.60
01 02 11 10.2 25.5 0 24.3 8.21 19.2
03 02 12 4.73 15.3 4.92 16.1 4.32 13.6
03 04 13 0.97 -0.9 0.87 -1.2 1.06 -0.8
01 05 14 5.96 19.3 4.68 14.1 0 26.1
05 04 15 0.89 1.53 0.76 1.39 1.06 2.18
02 04 16 3.25 5.97 3.60 7.04 2.58 3.92
04 09 17 0.00 0.57 0.00 0.58 0.00 0.59
05 06 18 0 10.6 0 10.5 0 10.7
04 07 19 0 4.15 0 4.19 0 4.04
08 07 20 0 1.68 0 1.68 0 1.43
Total Losses 29.5 91.8 18.6 87.5 20.0 86.9

242
V.3 Compression between TCSC and UPFC
TABLE IV
Buses B/W 1-2
(Line 11)
Buses B/W 1-5
(Line 14)
P Loss
(MW)
Q Loss
(MVAR)
P Loss
(MW)
Q Loss
(MVAR)
TCSC 18.90 92.19 21.82 92.22
UPFC 18.66 87.50 20.07 86.98
Compare UPFC
with TCSC
0.24 4.69 1.75 5.24
Table IV shows results of comparison between TCSC and UPFC. The actual real and reactive
power losses in the system is 29.50 (MW) and 91.80 (MVAR). Case 1, if the TCSC is connected in
the line 11 the real and reactive power losses in the system are 18.90 (MW) and 92.19(MVAR), if
the UPFC is connected in the same line 11, the real and reactive power losses in the system is 18.66
(MW) and 87.50(MVAR). Comparing UPFC with TCSC, UPFC can reduce more real (0.24 MW)
and reactive (4.69 MVAR) power losses. Similarly inCase2, in which UPFC connected in line 14,
reduces more real (1.75 MW) and reactive (5.24 MVAR) power losses. In both cases UPFC gives
better performance than TCSC. In all above results, the location of UPFC in the 11th
line of the
system gives more advantage and better performance.
VI. CONCLUSION
The power flow study is steady state solution of power system, it help better operation and
performance of the systems. The IEEE 14 bus test system has been modeled in MATLAB power
system analysis tool box. The power flow solution of the system is carried by Newton -Raphson
method. The line flow limit violation is found from load flow solutions. Both real and reactive power
losses in the system are minimized with Flexible AC Transmission Systems. Thyristor-Controlled
Series Capacitors (TCSC) and Unified Power Flow Controller (UPFC) are most versatile devices in
FACTS, which have been selected for test systems and all results are analyzed. This work is useful
for optimal power flow problem and location of FACTS in the system in economical point of view.
ACKNOWLEDGEMENTS
This work has been supported by National Institute of Technology Calicut for Progress
Review of PhD Scholar in July 2013.

243
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244
AUTHORS’ INFORMATION
Guguloth Ramesh is currently Research Scholar in Electrical Engineering
Department, National Institute of Technology, Calicut, Kerala -673601, and India.
His is pursuing Ph. D in NIT Calicut. Date of Birth 23-05-1987. He completed B.
Tech. at Christu Jyothi Institute of Technology and Science (JNTU Hyderabad) in
2008, M .Tech at NIT Calicut in 2011. His areas of interest and research are Power
Systems, Restructuring Power Systems, Flexible AC Transmission System, and
Micro grid. He has published one international journal paper in International
Review on Modelling and Simulations.
Dr .T.K. Sunil Kumar, Assistant Professor, Electrical Engineering
Department, NIT Calicut, Kerala -673601, India. He has completed B. Tech at
N.S.S College of Engineering Palakkad, M .Tech. at NIT Jamshedpur, and Ph. D. at
IIT Kharagpur. His interested areas are Model Matching Controller Design Methods
with Applications in Electric Power Systems, Restructuring Power Systems,
Flexible AC Transmission System, and Micro grid.

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