Download Modeling and Simulation of SVC for Reactive

Modeling and Simulation of SVC for Reactive Power
compensation of transmission line
M.TECH Scholar
Er. Satish kumar
Sandeep kumar
(Asst. Professor in
In RPIIT College
Electrical Engineering
Bastara, Karnal
in RPIIT College
[email protected]
Bastara, Karnal)
[email protected]
Abstract
The FACTS technology is a promising technology to achieve complete deregulation of Power
System i.e. Generation, Transmission and Distribution as complete individual units. The loading
capability of transmission system can also be enhanced nearer to the thermal limits without
affecting the stability. Complete close-loop smooth control of reactive power can be achieved
using shunt connected FACTS devices. The study of SVC, their principles of operation and
control are carried out. In this work, Static Var Compensator (SVC) shunt connected FACTS
devices, which can be utilized for the purpose of reactive power compensation. First, an
uncompensated system is considered and real and reactive powers are noted. Then the above said
facts devices are used for making and compensating the above network. Again real and reactive
powers are obtained and the results are compared.
KEYWORDS
FACTs, Matlab/Simulink, SVC Voltage control.
1. INTRODUCTION
Power transmission based on three phase systems started in the late 19th century. The supply of
electrical energy developed from separated utilities to large interconnected systems. In former
times distributed power generation supplied load centers within a limited supply area. These
smaller systems were operated at lower voltage levels. Now a day there is increased power
exchange over larger distances at highest system voltages allowing reserve sharing and
competition. Electrical energy shall be made available at most locations at minimum cost and at
highest reliability. Following problems have been observed in three-phase systems already at
early times of power transfer:
1 Voltage control at various load conditions
2 Reactive power balance (voltage, transmission losses)
3 Stability problems at energy transfer over long distances
4 Increase of short circuit power in meshed systems
5 Coupling of asynchronous systems
6 Coupling of systems with different system frequencies
The last two problems can be solved using HVDC technology and the upper ones can be solved
by proper use of reactive power compensation based on FACTS device (SVC).
The Static Var Compensator (SVC) is today considered a very mature technology. It has been
used for reactive power compensation. There are multiple applications within power systems,
e.g. to increase power transfers across limited interfaces, to dampen power oscillations and to
improve the voltage stability margins.
An SVC is a shunt connected FACTS device whose output can be adjusted to exchange either
capacitive or inductive currents to the connected system. This current is controlled to regulate
specific parameters of the electrical power system (typically bus voltage).
The thyristor has been an integral part in realizing the SVC and to enable control of its reactive
power flow. It is used either as a switch or as a continuously controlled valve by controlling the
firing angle. It should be noted that the SVC current will contain some harmonic content,
something that needs attention in the design process. The SVC can be used to control the voltage
level at a specific bus with the possibility of adding additional damping control. This can be
effectively dampened oscillations in the power system such as sub synchronous resonances
(SSR), inter-area oscillations and power oscillations. SVC is used at a large number of
installations around the world and is still considered an attractive component to improve the
performance of AC power systems.
2. Simulink model without any compensation
Simulink model without any compensation mean that there are no compensation element like
SVC are present in network system.
The system, connected in a loop configuration, consists essentially of five buses (B1 to B5)
interconnected through transmission lines (L1, L2) and two 500 kV/230 kV transformer banks
Tr1 and Tr2. Two power plants located on the 230-kV system generate a total of 2250 MW
which is transmitted to a 500-kV 15000-MVA equivalent located at B5 and to a 600-MW load
connected at bus B3. The plant models include a speed regulator, an excitation system as well as
a power system stabilizer (PSS). In normal operation, most of the 1250-MW generation capacity
of power plant is exported to the 500-kV equivalent through three 800-MVA transformers
connected between buses B4 and B5. Using the load flow option of the power block, the model
has been initialized with plants 1 and 2 generating respectively 1000 MW and 1250 MW and the
SVC not included in the circuit.
Figure2.1 Circuit model without SVC
When simulation is done on model, the voltage at buses and reactive power flows are obtained.
Bus
number
1
Reactive
power(Mvar)
- 13.85
Voltage(p.u)
2
19.23
0.978
0.9859
3
-425.2
0.9723
4
5
109.1
-463.7
0.9833
0.9723
Table2.1 Result obtain without SVC
3. Simulink model with SVC
Simulink model with compensation mean that there are compensation element like SVC are
present in network system.
A SVC is used to control the reactive power flow in a 500 kV /230 kV transmission system. The
system, connected in a loop configuration, consists essentially of five buses (B1 to B5)
interconnected through transmission lines (L1, L2) and two 500 kV/230 kV transformer banks
Tr1 and Tr2. Two power plants located on the 230kV system generate a total of 2250 MW which
is transmitted to a 500-kV 15000-MVA equivalent located at B5 and to a 600-MW load
connected at bus B3. The plant models include a speed regulator, an excitation system as well as
a power system stabilizer (PSS). In normal operation, most of the 1250-MW generation capacity
of power plant is exported to the 500kV equivalent through three 800MVA transformers
connected between buses B4 and B5. Using the load flow option of the power gui block, the
model has been initialized with plants 1 and 2 generating respectively 1000 MW and 1250 MW
and the SVC included in the circuit.
Figure3.1 Circuit model with SVC
When simulation is done on model, the voltage at buses, active power flows, and reactive power
flows are obtained.
Bus
number
1
Reactive
power(MVar)
-15.46
Voltage(p.u)
2
-37.25
0.9922
3
-104.1
0.9906
4
46.78
0.990
5
-201.5
0.9906
0.9931
Table3.1 Result obtain with SVC
4. Result
From the simulation results of SVC it is found that SVC can effectively use for voltage and
reactive power compensation. Thus the superiority of SVC over fixed capacitor compensation is
proved. In addition to this we have following observations about SVC by comparison of results
obtained with or without SVC.
Without (compensation)
With SVC
Q(MVAR)
V(pu)
Q(MVAR)
V(pu)
-13.85
0.9859
-15.46
0.9931
19.23
0.978
-37.25
0.9922
-425.2
0.9723
-104.1
0.9906
109.1
0.9833
46.78
0.990
463.7
0.9723
-201.5
0.9906
Table4.1 comparison of results obtained with or without SVC.
From the above result comparison, it can be analyzed that with the use of SVC there is
considerable improvement in the flows of reactive power through the transmission lines(decrease
in lagging reactive power flows) resulting in improvement in the voltages at the buses.
5. Conclusion
MATLAB/SIMULINK environment is used for this comparative study to model and simulate
shunt facts devices SVC connected to a transmission line. A power flow model without any
compensation and SVC are attempted and it has been analyzed that the reactive power flows
through transmission lines are much reduced with the SVC which results in reduced line current
flows and in turn resulting in increase in voltage at various buses of the system model. By
choosing the SVC at nearer to load side is the best reduction of losses, maintain good voltage
regulation. The comparison between the results obtained using SVC and without SVC
respectively in the model has been done, which concludes that the use of SVC allows flexible
operation of an AC system without stressing the system.
REFERENCES
[1] Pravin Chopade and Dr. Marwan Bikdash “Reactive Power Management and Voltage
Control of large Transmission system using SVC (Static VAR Compensator)” Computational
Science and Engineering Department, state University, Greensboro, USA.
[2] M. Biswas, “Voltage Level Improving by Using Static VAR Compensator (SVC)” in
Bangladesh University of Engineering and Technology (BUET), Bangladesh in 2011.
[3] Juan Dixon and Luis Moran, “Reactive Power Compensation Technologies” member of
Electrical Engineering Dept. vol -3 in 1987.
[4] R.T. Byerly, “Static Reactive Compensation for Power Transmission Systems” senior
member IEEE Westinghouse Electric Corporation, Pittsburgh in 1982.
[5] Alisha Banga and S.S. Kaushik, “MODELING AND SIMULATION OF SVC
CONTROLLER FOR ENHANCEMENT OF POWER SYSTEM STABILITY” International
Journal of Advances in Engineering & Technology, July 2011.
[6] D. Povh and Erlangen, “ ADVANCED SVC CONTROL FOR DAMPING POWER
SYSTEM OSCILLATIONS” senior member, IEEE Transactions on Power Systems, Vol. 6, No.
2, May 1991.
[7] Noriyuki Kitnura, “REACTIVE IWWER COMPENSATION OF HVDC CONVERTER BY
STATIC VAR COMPENSATOR USING VOLTAGE SOURCE FORCED COMMUTATION
CONVERTER” from student member Electrical Engineering Dept. Faculty of Eng. Osaka
University, Suita, Osaka, JAPAN.
[8] Y. Lee and C. J. Wu, “Reactive power compensation and load balancing for unbalanced
three-phase four wire system by a combined system of an SVC and a series active filter” from
department of Electrical Engineering, National Taiwan University of Science and Technology
Pcitow Tailxi Taiwan vol 147, no 6,2010.