Performance Analysis of Some FACTS Devices Using Newton Raphson Load Flow Algorithm
Performance Analysis of Some FACTS Devices Using Newton Raphson Load Flow Algorithm
Performance Analysis of Some FACTS Devices Using Newton Raphson Load Flow Algorithm
Abstract—A comparative study and performance analysis is used to maintain power transmission capability and to
done for a number of FACTS devices in this paper. The models maintain the supply voltage within the specified limits.
used are incorporated in an existing Newton Raphson Load Flow Control of line impedance of the transmission line is known as
(NRLF) algorithm using standard IEEE 5 bus and 30 bus system. series compensation. When the line impedance changes it
Problem of initialization for proper convergence of load flow is
means that either capacitive or inductive compensation can be
studied and findings are presented. Results are presented for
comparison of performance analysis and evaluation of degree of obtained which in turn enables to control active power. TCSC
suitability of selected FACTS devices. (Thyristor Controlled Series Capacitor) connected in series
with the transmission line provides means to change the
Keywords— Newton-Raphson load flow, FACTS, TCSC, impedance of the line thus providing an option to enhance the
STATCOM, UPFC, Jacobian, MATLAB. power transfer capability. Shunt connected compensators are
used to increase steady state transmittable power and to
I. INTRODUCTION control voltage profile. One such shunt connected
FLEXIBLE AC transmission system is “A power electronic compensator is the STATCOM (Static Compensator) that
based system and other static equipment that provide control comes under FACTS device category. The Synchronous
of one or more AC transmission system parameters to enhance voltage source UPFC model [7] injects into the system a
controllability and increase power transfer capability”. Its first voltage of variable magnitude and angle in series with the line.
concept was introduced by N.G Hingorani, in 1988 [1]. Now- a- These parameters adjust automatically so as to control the
days multiple and multi-type FACTS devices are becoming active and the reactive powers exchanged between the UPFC
interesting areas for the researchers [2]. Flexible AC and the AC system.
transmission systems, so-called FACTS devices, can help In this paper FACTS device models are incorporated in Newton
reduce power flow on overloaded lines, which would result in Raphson Load Flow (NRLF) algorithm in order to investigate the
control of power flow and improvement of voltage. All the
an increased load ability of the power system, fewer
equations are then combined in to one set of non-linear algebraic
transmission line losses, improved stability and security and,
equations. A jacobian matrix is then formed which is non
ultimately, a more energy-efficient transmission system symmetric in nature.
[3].The transmission facilities are being overused owing to the
higher industrial demands and deregulation of the power II. MODEL OF FACTS DEVICES
supply industry. Thus there is a need for exploring new ways
for maximizing the power transfer capability of existing A. Thyristor Controlled Series Compensator
transmission facilities while, at the same time, maintaining A TCSC can be defined as a capacitive reactance compensator
acceptable levels of network reliability and stability [4]. This which consists of a series capacitor bank shunted by a
scenario makes necessary the development of power electronic thyristor-controlled reactor in order to provide a smoothly
based devices for high performance control of the power variable series capacitive reactance [8]. In a practical TCSC
network. The FACTS controllers provide the most useful implementation, several such basic compensators may be
means and thus are used in regulating the power flows, connected in series to obtain the desired voltage rating and
maintaining transmission voltages within limits and mitigate operating characteristics. However, the basic idea behind the
the dynamic disturbance. UPFC and STATCOM are effective TCSC scheme is to provide a continuously variable capacitor
and robust devices for power system stability [5]. by means of partially canceling the effective compensating
Static models of three FACTS devices consisting of SVS capacitance. A TCSC is a series-controlled capacitive
model of Unified Power Flow Controller (UPFC), Thyristor reactance that can provide continuous control of power on the
Controlled Series Capacitor (TCSC) and STATCOM have ac line over a wide range. A simple understanding of TCSC
been selected for the steady-state analysis [6]. functioning can be obtained by analyzing the behavior of a
To minimize the power transmission loss, reactive power variable inductor connected in parallel with a Fixed Capacitor.
compensation is used. Reactive power compensation is also The maximum voltage and current limits are design values for
which the thyristor valve, the reactor and capacitor banks are III. IMPLEMENTATION
rated to meet specific application requirements. The basic power flow equations are given by
(1)
(2)
(9)
Generated power
Bus Uncompensate With
With TCSC With SVS
d system STATCOM
P Q P Q P Q P Q
131. 131.
North 131.1 90.8 90.9 85.3 130.9 94.9
1 1
-61. -61. -77.
South 40 40 40 40 -66.7
6 8 1
Fig.7 IEEE 30 bus system
TABLE IV. BUS POWERS FOR 30 BUS SYSTEM
The TCSC is connected between lake bus and main bus for Bus Generated power
IEEE 5 bus system to control real power flow at 21MW and num Uncompensate
With TCSC
With
With SVS
between bus number 6 and 7 for IEEE 30 bus system to ber d system STATCOM
P Q P Q P Q P Q
control real power flow at 42MW. The STATCOM is -
connected at lake bus in case of 5 bus systems and for 30 bus 1 2.61 -0.164 2.61 -0.164 2.61 -0.165 2.61
0.160
system it is connected to bus 30. The SVS is connected 2 0.40 0.498 0.40 0.488 0.40 0.496 0.4 0.511
between lake bus and main bus for 5 bus system to control real
5 0.00 0.371 0.00 0.385 0.00 0.370 0.0 0.378
power flow at 40MW and reactive power at 2MVAR whereas
for 30 bus system the SVS is connected between bus number 6 8 0.00 0.379 0.00 0.369 0.00 0.372 0.00 0.343
and 8 to control the real power flow at 33MW and reactive
11 0.00 0.169 0.00 0.168 0.00 0.167 0.00 0.173
power at 6MVAR from bus 8 to bus 6. The results as shown in
tabular form have been obtained and are compared with the 13 0.00 0.109 0.00 0.108 0.00 0.107 0.00 0.113
uncompensated system. P in MW
Q in MVAR
TABLE I. BUS VOLTAGE MAGNITUDE AND ANGLE COMPARISON FOR 5 Generation remain unaffected with the inclusion of TCSC.
BUS SYSTEM With the inclusion of STATCOM the slack generator reduces
Uncompensated Compensated system its reactive power generation by almost 6% compared to the
system Voltage base case for 5 bus system, whereas for 30 bus system all the
Voltage With TCSC With STATCOM With SVS generator reduces reactive power generation by a small
Magnit Angle Magnit Angle Magnit Angle Magnit Angle amount. Inclusion of SVS results in generation of 4.5% more
ude (degre ude (degre ude (degre ude (degre
(PU) es) (PU) es) (PU) es) (PU) es)
reactive power by slack bus for 5 bus systems and for 30 bus
0.9872 system reactive power generation increases in all the generator
-4.637 0.9870 -4.727 1.0000 -4.840 0.9790 -5.724
(Lake) buses except for bus number 8.
0.9841
-4.957 0.9844 -4.811 0.9944 -5.109 0.9948 -3.181 A. Power flow comparison of TCSC
(Main)
Bus voltage almost remains unaffected with inclusion of The TCSC upholds the target value, which is achieved with
TCSC in both the system. Inclusion of STATCOM maintains 72% series capacitive compensation for Lake–Main line of 5
bus system and 61.34% series capacitive compensation of the
line 6-7 for 30 bus system. From the load flow results it is TABLE X. POWER FLOW COMPARISON OF SVS WITH BASE CASE FOR 5 BUS
SYSTEM
evident that TCSC controls only the real power flow through a
line and reactive power is almost unaffected. Thus TCSC has Power Flows
From To
its application only when there is a need to control real power Without SVS With SVS
flow and also to change power flow routes. bus Bus P(MW) Q(MVAR) P(MW) Q(MVAR)
Initial value of
Number of iterations
STATCOM
The STATCOM generates -1.20MVAR and parameter parameters
required
associated with this amount of reactive power generation are Voltage
Angle 5 bus 30 bus
Vsh=1.0012 p.u. and δsh = -17.75 degrees. The reactive power Magnitude
(radian) systems systems
transmitted from bus 27 to 30 and from 29 to 30 reduces to ( PU)
almost 50% 1 0 5 5
1.3 0 5 5
TABLE IX. POWER FLOW COMPARISON OF SVS WITH BASE CASE FOR 5 BUS
SYSTEM 1 -1 7 7
Power Flows 1 1 7 7
From To
Without SVS With SVS 1 -2 10 10
bus bus P(MW) Q(MVAR) P(MW) Q(MVAR)
1 2 10 10
Lake Main 19.4 2.9 40.0 2.0