International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 11, November 2012)
Control of Active and Reactive Power Flow in Multiple Lines
through Interline Power Flow Controller (IPFC)
Indra Prakash Mishra1, Sanjiv Kumar2
1
2
Research Scholar, Assistant Professor, Department of EE, Harcourt Butler Technological Institute, Kanpur
Abstract — In this paper a circuit model for IPFC is
developed using series coupling transformers and comparison
of active and reactive power of Transmission Lines with and
without IPFC is presented using the proposed circuit model.
Comparison is also done with individual Static Synchronous
Series Compensators (SSSCs), one on each line of a two line
system and the results are compared with the previous one.
MATLAB with Simulink and SIM POWER SYSTEMS tools
are used for simulation of Transmission lines and IPFC in
open loop and closed loop configurations. A common DC link
within the IPFC is able to facilitate real power transfer among
the lines of the transmission system. Also each inverter can
provide reactive power compensation independently.
IPFC is developed with the objective of balancing real
and reactive power flow among multi-lines and to transfer
power from overloaded to under loaded lines. Second
objective of IPFC is to compensate against reactive voltage
drops and the corresponding reactive line power, thereby
increasing the effectiveness of the compensating system
against dynamic disturbances. An attempt is made in the
present work to develop circuit model for four-bus system
with IPFC and two series coupling transformers.
A. Basic Interline Power Flow Controller
Index Terms-- Interline Power Flow Controller (IPFC),
FACTS devices, Reactive Power Compensation, Simulation of
IPFC, Transmission line sag mitigation.
I. INTRODUCTION
The involvement of a new family of FACTS devices
which is based on Voltage Source Converters (VSC) added
the features like flexible power flow control, transient
stability and power system oscillation damping
enhancement. Static Synchronous (shunt) Compensator
(STATCOM), the Static Synchronous Series Compensator
(SSSC) the Unified Power Flow Controller (UPFC) and the
Interline Power Flow Controller (IPFC) are the members of
family of compensators and power flow controllers based
on VSC.
The UPFC provide independent control both for the real
and reactive power flow of individual transmission lines
thereby providing the cost effective utilization. While the
Interline Power Flow Controller (IPFC) concept provides
compensation in a number of transmission lines. [3], [4],
[8], [14]. The interline power flow controller (IPFC) is one
of the latest FACTS controller used to control power flows
of multiple transmission lines. Interline Power Flow
Controller (IPFC) is an extension of static synchronous
series compensator (SSSC). Any converters within the
IPFC can transfer real power to any other and hence real
power transfer among the lines may be carried out, together
with
independently
controllable
reactive
series
compensation of each individual line.
Fig 1: Basic Interline Power Flow Controller
The IPFC consists of two voltage sourced converters,
connected back-to-back and are operated from a common
dc link provided by a storage capacitor as shown in the
fig.1
The arrangement shown in the fig.1 functions as an ideal
ac-to-ac power converter in which the real power can freely
flow in either direction between the ac terminals of the two
converters, and each converter can independently generate
(or absorb) reactive power at its own ac output terminal.
B. Generalized Interline Power Flow Controller
There can be compensation requirements for particular
multi-line transmission systems which would not be
compatible with the basic constraint of the IPFC,
stipulating that the sum of real power exchanged with all
the lines must be zero. This constraint can be circumvented
by a generalized IPFC arrangement, in which a shunt
connected inverter, is added to the number of inverters
providing series compensation as illustrated in fig 4.6.
86
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 11, November 2012)
With this scheme the net power difference at the ac
terminal is supplied or absorbed by the shunt inverter, and
ultimately exchanged with the ac system at the shunt bus.
This arrangement can be economically attractive, because
the shunt inverter has to be rated only for the maximum
real power difference anticipated for the whole system. It
can also facilitate relatively inexpensive shunt reactive
compensation, if this is needed at the particular substation
bus.
A. Simulation of Two Transmission Lines without IPFC
The simulation of two Transmission Lines without IPFC
is done and active and reactive powers of primary and
secondary loads are observed. MATLAB Simulation model
of Primary and Secondary lines without IPFC is presented
in Fig 3
Fig 2: A Generalized Interline Power Flow Controller for Power
Transmission Management
Fig 3: MATLAB Simulation Model of Primary and Secondary Lines
without IPFC
II. SIMULATION OF IPFC
B. Simulation of Two Transmission Lines with Two
individual SSSCs s
As IPFC is extension of SSSCs in multiple lines. The
model is presented here for the above mentioned two-line,
four-bus system with individual SSSCs in each line. There
is no interconnection between these SSSCs. The active and
reactive powers are measured and it is observed that the
results are improved as compared with the system without
IPFC or SSSC. The MATLAB circuit model with
individual SSSCs is presented in Fig 4.
A single phase system is considered for the purpose of
simulation. Two lines are modeled, one as primary line and
another as secondary line. The load of lines is selected in
such a way to model one line as overloaded as compared to
the primary. The primary and secondary lines are
connected with identical voltage sources of 110kV.
Primary voltage is at phase angle 150 and secondary
voltage is at phase angle 300
87
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 11, November 2012)
Fig 6: SSSC Subsystem for Secondary Line with Individual SSSC
2) Pulse generation Module
The pulse generation module has been developed for
switching of converters used throughout in this work.
Sinusoidal signal is compared with the reference to produce
rectangular pulses whose width is controllable through the
reference. The MATLAB circuit for this module is shown
below in Fig 7
Fig 4: MATLAB Simulation Model of Primary and Secondary Lines
with Individual SSSCs
1) SSSC Subsystem
Figure 5 and 6 present the SSSC subsystem for the
primary line and secondary line. High speed switches are
taken for the fabrication of converter. A capacitor is
connected to act as DC link.
Fig 7: Matlab Circuit model for Pulse Generation Module
C. IPFC in Open Loop
The single phase model of two line-four bus system with
IPFC is shown in Fig. 8 and 9.
Fig 5: SSSC Subsystem for Primary Line with Individual SSSC
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 11, November 2012)
In the present paper series coupling transformers are
used at primary line side as well as at secondary line side.
The MATLAB Simulink circuit model of the two-lines
with IPFC connected in open loop is shown in figure 8.
Fig 9: Matlab Circuit Model of Closed Loop IPFC System
1) IPFC Subsystem
The IPFC subsystem consisting of two back to back
connected Voltage source converters system used in the
IPFC model is shown in Fig. 10. Capacitor is used to create
common DC link for both the converters.
Fig 8: Matlab Circuit Model of Open Loop IPFC System
D. IPFC in Closed Loop
The MATLAB Simulink circuit model of the IPFC
connected in closed loop is shown in figure 9. Scopes are
connected to the primary load and secondary load. Real and
reactive powers in the loads are measured. Voltages across
primary load and secondary load are sensed and compared.
The output is given to a PI controller; the error produced
will drive the PI controller, which produces the signal to be
sent to input 1 of IPFC subsystem and controls the duty
cycle of converters. Instead of comparing the load voltages
of two lines the voltage of the secondary may also be
compared with a fixed reference value suiting to our
requirement. IPFC is connected at the mid point of
transmission line. The primary source voltage is 110kV 
150 and the secondary source voltage is 110kV  300.
Linear transformers are connected at the primary line and at
the secondary line in series with the respective lines.
Fig 10: IPFC Subsystem
89
International Journal of Emerging Technology and Advanced Engineering
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B. Simulation Results of Two Transmission Lines with
individual SSSCs
III. DATA ANALYSIS AND RESULTS
A. Simulation Results of Two Transmission Lines without
IPFC
At the beginning the simulation of model was done
without IPFC. Simulation was done with equal voltages
[110kV] on the input sides and different phase angles
[Primary source voltage with phase angle 15o and
secondary source voltage with 30o. Due to the difference in
phase angle, there is an increase in the real power of the
secondary load when compared to the primary load. The
snap shots of scope showing the real and reactive power of
secondary circuit are shown in figure 11.
TABLE 2
REAL AND REACTIVE POWERS OF PRIMARY AND SECONDARY
CIRCUITS WITH INDIVIDUAL SSSCS
Constant
referred to
Duty Cycle
Primary Load
Secondary
Load
Value
%
Active
Power
(MW)
Reactive
Power
(MVAR)
Active
Power
(MW)
Reactive
Power
(MVAR)
0.8
66.67
8.78
1
6.578
9.467
7.092
Real and Reactive powers of primary and secondary
circuits with individual SSSCs are observed. The variations
in real and reactive powers of primary and secondary loads
with respect to the duty cycle constant are recorded and
presented in Table 2 and the corresponding snapshots of
scopes are presented in Fig 12 and Fig 13.
Fig 11: Active and Reactive Power in Secondary Load without IPFC
The real powers in primary and secondary loads are
shown in Table 1
TABLE 1
REAL AND REACTIVE POWERS OF PRIMARY AND SECONDARY
CIRCUITS WITHOUT IPFC
Lines
without
IPFC
Primary Load
Active
Reactive
Power
Power
(MW)
(MVAR)
Secondary Load
Active
Reactive
Power
Power
(MW)
(MVAR)
8.767
9.417
6.589
Fig 12: Active and Reactive Power in Primary Load with Individual
SSSC
7.1
90
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 11, November 2012)
Fig 14: Active and Reactive Power in Primary Load with IPFC in
Open Loop
Fig 13: Active and Reactive Power in Secondary Load with Individual
SSSC
C. Simulation Results of Two Transmission Lines with
IPFC
1) Simulation in Open Loop Mode
The simulation was done with IPFC in open loop.
Variation in Real and Reactive powers of primary and
secondary circuits with respect to duty cycle of converter,
are observed and tabulated in Table 3. Snap shots are
shown in figure 14 and 15.
TABLE 3
VARIATION IN REAL AND REACTIVE POWERS OF PRIMARY AND
SECONDARY CIRCUITS, WITH RESPECT TO DUTY CYCLE OF
CONVERTER
Constant
referred to
Duty Cycle
Primary Load
Secondary
Load
Value
%
Active
Power
(MW)
Reactive
Power
(MVAR)
Active
Power
(MW)
Reactive
Power
(MVAR)
0.8
66.6
7
8.813
6.601
9.492
7.110
Fig 15: Active and Reactive Power in Secondary Load with IPFC in
Open Loop
2) Simulation in Closed Loop mode
The simulation was done with IPFC in closed loop. In
the closed loop the voltage of primary and secondary are
sensed and are compared. Whenever there is a difference in
voltage, the PI controller gives the corresponding output to
make the error zero. The improvement in results is
observed by using transformer at both sides and converters
at both sides. The real and reactive power in closed loop is
shown in fig 16 and 17.
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TABLE 4
ACTIVE AND REACTIVE POWERS WITHOUT IPFC, WITH INDIVIDUAL
SSSC AND WITH IPFC
Condition
Lines
without
IPFC
Lines with
Individual
SSSC
Lines with
IPFC
Fig 16: Active and Reactive Power of Primary Load with IPFC in
Closed Loop
Primary Load
Active
Power
(MW)
Reactiv
e
Power
(MVA
R)
8.780
6.570
Secondary
Load
Activ Reactiv
e
e
Powe Power
r
(MVA
(MW
R)
)
9.464
7.088
8.781
6.578
9.467
7.092
8.813
6.601
9.492
7.110
IV. CONCLUSIONS
IPFC is capable of balancing the power through the
lines. The power quality is improved since IPFC permits
additional power. The circuit models for IPFC system are
simulated using MATLAB. These models are used for
simulating a two line-four bus system. Improved model
with transformer on both lines and back to back converters
is presented which improves the reactive power of the
secondary line from 7.088 to 7.110 MVAR. The active
power of the secondary is also increased from to 9.492 MW
as compared to the value that of without IPFC. In other
words the proposed model of IPFC increases the real power
transfer and improves the voltage profile.
Fig 17: Active and Reactive Power of Secondary Load with IPFC in
Closed Loop
The comparison of active and reactive powers with and
without IPFC and with individual SSSC is presented in
Table 4. The SSSC is capable of increasing the reactive
power of secondary load from 7.088 MVAR in without
IPFC system, to 7.092, with equal voltages (110 kV) at the
source bus of both the lines, with phase angle of 150 for
primary and 300 for secondary line. Further the IPFC
increases the reactive power of secondary from 7.092 to
7.110 MVAR. In other words the proposed model improves
the reactive power of the secondary line from 7.088 to
7.110 MVAR. The active power of the secondary is also
increased from to 9.492 MW as compared to the value that
of without IPFC. The consolidated simulation results are
finally presented in Table 6.4.
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