Major Report

B.Tech (Electrical-2013) Name:NANDINI JANGPANGI, NISHA PARVEEN, OWAIS QAZI

REACTIVE POWER COMPENSATION USING FACTS DEVICES MAJOR PROJECT REPORT SUBMITTED IN FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE OF

BACHELOR OF TECHNOLOGY IN ELECTRICAL ENGINEERING Submitted by:

NANDINI JANGPANGI (09EES-38) NISHA PARVEEN (09EES-40) OWAIS AHMED QAZI (09EES-41) Under the supervision of

DR. ANWAR SHAHZAD SIDDIQUI

DEPARTMENT OF ELECTRICAL ENGINEERING FACULTY OF ENGINEERING & TECHNOLOGY JAMIA MILLIA ISLAMIA NEW DELHI-110025 INDIA

2013 1

DEPARTMENT OF ELECTRICAL ENGINEERING FACULTY OF ENGINEERING AND TECHNOLOGY JAMIA MILLIA ISLAMIA

CERTIFICATE This is to certify that the Project titled “REACTIVE POWER COMPENSATION USING FACTS DEVICES” submitted in fulfillment of the requirements for the award of the degree of Bachelor of Technology in Electrical Engineering by NANDINI JANGPANGI (09EES-38), NISHA PARVEEN (09EES-40), OWAIS AHMED QAZI (09EES-41)is a bonafide record of the candidate’s own work carried out by them under my supervision and guidance. This work has not been submitted earlier in any university or institute for the award of any degree to the best of my knowledge.

Dr. A. S. SIDDIQUI Professor Department of Electrical engineering Jamia Millia Islamia

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ACKNOWLEDGEMENT We feel profound pleasure in bringing out this project report for which we have to go from pillar to post to make it a reality. This project works reflects contribution of many people with whom we had long discussion and without which it would not have been possible. We must first of all express our heartiest gratitude to respected Dr. A. S. Siddiqui of Department of Electrical Engineering for providing us all required guidance to complete project, for providing us the components required for the project and providing us the laboratory where we completed our project. We are also thankful to Prof. Zaheeruddin, HOD, Department of Electrical Engineering for his work and cooperation to facilitate smooth progress of the project. It would be unfair if we would not mention the invaluable contribution and timely cooperation extended to us by staff members and laboratory assistance of our Department. A special thanks to our parents and friends whose inspiration made the whole project a great success. Last but not the least we express our sincere thanks to the Institute JamiaMilliaIslamia for providing us such a platform for implementing the ideas in our minds.

NANDINI JANGPANGI (09EES-38)

NISHA PARVEEN (09EES-40)

OWAIS AHMED QAZI (09EES-41)

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ABSTRACT The Power electronic based FACTS devices can be added to power transmission and distribution systems at strategic locations to improve system performance.

Modelling and simulation of Fixed Capacitor Thyristor Controlled Reactor (FC-TCR) and Thyristor controlled Series Capacitor (TCSC) for power system stability enhancement and improvement of power transfer capability have been presented in this project. First, power flow results are obtained and then power (real and reactive power) profiles have been studied for an uncompensated system and then compared with the results obtained after compensating the system using the above-mentioned FACTS devices. The simulation results demonstrate the performance of the system for each of the FACTS devices in improving the power profile and thereby voltage stability of the same. All simulations have been carried out in MATLAB/SIMULINK environment.

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TABLE OF CONTENTS Topics

Page No.

1. Introduction

6-7

2. Theoretical background

10

2.1. Introduction

11

2.2. Basic principle of power compensation

11-14

2.3. FACTS

14-16

2.4. Basic description of FACTS devices

16-19

3.Simulation

20

3.1. Introduction

21

3.2. Performance analysis

21

3.2.1. Uncompensated system model

21

3.2.2. Compensated system

22-23

4.Results and discussion

24

4.1. Results of uncompensated system

25

4.2. FC-TCR compensated system

25-26

4.3. TCSC compensated system

27

4.4. Discussion

28-29

5.Conclusion

30-31

References

32

5

CHAPTER 1

INTRODUCTION

6

INTRODUCTION: Rising energy costs and greater sensitivity to environmental impact of new transmission lines necessitated new controllers to minimize losses and maximize the stable powertransmission capacity of existing lines. FACTS technology opens up new opportunities for controlling power and enhancing usable capacity of the existing lines. FACTS technology is one that incorporates power-electronics based and other static controllers to enhance controllability and increase power transfer capability. The increasing complexity and interconnectedness of existing power systems present new challenges for their secure operation. Therefore, they call new and efficient forms of power control. In most of the AC systems the load sharing while transmitting power is entirely governed by the line impedance. In this context, the high power switching devices applied at the transmission level is bringing utilities new opportunities as well as new challenges for controlling the main parameters related to power flow and voltage control. In the evolving utility environment, financial and market forces are, and will continue to, demand a more optimal and profitable operation of the power system with respect to generation, transmission, and distribution. Now, more than ever, advanced technologies are paramount for the reliable and secure operation of power systems. To achieve both operational reliability and financial profitability, it has become clear that more efficient utilization and control of the existing transmission system infrastructure is required. Improved utilization of the existing power system is provided through the application of advanced control technologies. Power electronics based equipment, or Flexible AC Transmission Systems (FACTS), provide proven technical solutions to address these new operating challenges being presented today. FACTS technologies allow for improved transmission system operation with minimal infrastructure investment, environmental impact, and implementation time compared to the construction of new transmission lines. When discussing the creation, movement, and utilization of electrical power, it can be separated into three areas, which traditionally determined the way in which electric utility companies had been organized. These are illustrated in Fig.1.1.

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Fig.1.1 Illustration of the creation, movement and utilization of electrical power

Although power electronic based equipment is prevalent in each of these three areas, such as with static excitation systems for generators and Custom Power equipment in distribution systems, the focus of the project and accompanying presentation is on transmission that is, moving the power from where it is generated to where it is utilized. Modern power system is complex and it is essential to fulfill the demand with better power quality. Advanced technologies are nowadays being used for improving power system reliability, security and profitability and due to this power quality is improved. Voltage stability, voltage security and power profile improvement are essential for power quality improvement. To achieve optimum performance of power system it is required to control reactive power flow in the network. Construction of new transmission lines and power stations increase the problem of system operation as well as the overall cost. Regulatory limitation on the expansion of system network has resulted in reduction in stability margin thereby increasing the risk of voltage collapse. Voltage collapse occurs in power system when system is faulted, heavily loaded and there is a sudden increase in the demand of reactive power. Voltage instability in power system occurs when the system is unable to meet the reactive power demand. Reactive power imbalance occur when system is faulted, heavily loaded and voltage fluctuation is there. Reactive power balance can be regained by connecting a device with the transmission line which can inject or absorb reactive power based on system requirement. One of the most important reactive power sources is FACTS (Flexible A.C transmission system) device. FACTS may be defined as a power electronic based semiconductor device which can inject or absorb reactive power in a systemas per requirement. This device allows “Flexible” operation of an AC system without stressing the system, which helps in controlling the power flow. Shunt type FACTS device are used for controlling and damping voltage oscillations in a power system. The benefits of employing FACTS are many: improvement of the dynamic and transient stability, voltage 8

stability and security improvement, less active and reactive power loss, voltage and power profileimprovement, power quality improvement, increasing power flow capability through the transmission line, voltage regulation and efficiency of power system operation improvement, steady state power flow improvement, voltage margin improvement, loss minimization, line capacity and load ability of the system improvement.

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CHAPTER 2

THEORETICAL BACKGROUND

10

2.1. INTRODUCTION: Research works are going on in finding newer concept for minimizing the reason of voltage collapse by increasing voltage stability (Dynamic, Transient and Steady-state stability), voltage margin and voltage security in the system. Voltage collapse is a major problem of power system and it occurs due to voltage instability. There are many analysis methods for determining voltage stability based on power flow. Steady- state stability is the ability of power system to control after small disturbances e.g.:- change in load. FACTS (Flexible alternating current transmission system) are mainly used for solving instability problems. Recently it has been noted that FACTS controllers can also be used for power flow control and stability enhancement control. Power electronic controllers were first introduced in HVDC transmission for improving power flow and system stability. There are four types of controllers in FACTS device family. Series controllers are used to inject voltage in series with the line and directly control voltage and current. In this paper modeling and simulation of various FACTS (Flexible alternating current transmission system) devices have been done using MATLAB/SIMULINK software. These FACTS devices are controlled by controlling their source and line impedance value. First we determined the impedance value for better system performance. By varying the value of capacitor of FACTS device models real and reactive power flow through the system is tabulated to find the FACTS device which gives better performance for a particular capacitor value.

2.2. BASIC PRINCIPLE OF POWER COMPENSATION IN TRANSMISSION SYSTEM: Figure 2.1 shows the simplified model of a power transmission system. Two power grids are connected by a transmission line which is assumed lossless and represented by the reactance X . V 1  1 andV 2  2 represent the voltage phasors of the two power grid L buses with angle  =  1 -  2 between the two. 11

Fig. 2.1Simplified model of power transmission system

The magnitude of the current in the transmission line is given by: I 

V X

L



V

1

  V 2 

L

X

L

The active power and reactive power at bus 1 are given by:

VV P1  1 2 X

sin 

  Q V V V X 1

1

2

cos 

1

L

L

The active power and reactive power at bus 2 are given by:

P

2



V V sin  , Q  V 2 V 2  V 1 cos  2 XL X 1

2

L

Power equations indicate that the active and reactive power flow can be regulated by controlling the voltages, phase angles and line impedance of the transmission system. The active power flow will reach the maximum when the phase angle δ is 90º. Generally, the compensation of transmission systems can be divided into two main groups: shunt and series compensation.

2.2.1.Series compensation Series compensation aims to directly control the overall series line impedance of the transmission line. The AC power transmission is primarily limited by the series reactive impedance of the transmission line. A series-connected can add a voltage in opposition to the transmission line voltage drop, therefore reducing the series line impedance.

12

2.2.2.Shunt compensation Shunt compensation, especially shunt reactive compensation has been widely used in transmission system to regulate the voltage magnitude, improve the voltage quality, and enhance the system stability. Shunt-connected reactors are used to reduce the line over-voltages by consuming the reactive power, while shunt-connected capacitors are used to maintain the voltage levels by compensating the reactive power to transmission line. A simplified model of a transmission system with shunt compensation is shown in Figure 2.2.

Fig. 2.2 Transmission system with shunt compensation

The voltage magnitudes of the two buses are assumed equal as V, and the phase angle between them is δ. The transmission line is assumed lossless and represented by the reactance X . At the midpoint of the transmission line, a L

controlled capacitor C is shunt-connected. The voltage magnitude at the connection point is maintained as V.

Fig. 2.3 Power Angle Curve

13

As discussed previously, the active powers at bus 1 and bus 2 are equal.

P P  2 V X 1

2

sin

2

L

 2

The injected reactive power by the capacitor to regulate the voltage at the midpoint of the transmission line is calculated as:

Q

C

4V

X

  1  cos  2 L 

2

From the power angle curve shown in Figure 3, the transmitted power can be significantly increased, and the peak point shifts from δ=90º to δ=180º. The operation margin and the system stability are increased by the shunt compensation. The voltage support function of the midpoint compensation can easily be extended to the voltage support at the end of the radial transmission, which will be proven by the system simplification analysis in a later section. The reactive power compensation at the end of the radial line is especially effective in enhancing voltage stability.

2.3. FLEXIBLE AC TRANSMISSION SYSTEM (FACTS): The history of FACTS controllers can be traced back to 1970s when Hingorani presented the idea of power electronic applications in power system compensation. From then on, various researches were conducted on the application of high power semiconductors in transmission systems. Nowadays, FACTS technology has shown strong potential. Many examples of FACTS devices and controllers are in operation. FACTS and FACTS controllers are defined in IEEE Terms and Definitions as: • Flexible AC Transmission System (FACTS): Alternating current transmission systems incorporating power electronic-based and other static controllers to enhance controllability and increase power transfer capability. • FACTS Controller: A power electronic-based system and other static equipment that provide control of one or more AC transmission system parameters. 14

As new technology for power transmission system, FACTS and FACTS controllers not only provide the same benefits as conventional compensators with mechanicallycontrolled switches in steady state but also improve the dynamic and transient performance of the power system. The power electronics-based switches in the functional Blocks of FACTS can usually be operated repeatedly and the switching time is a portion of a periodic cycle, which is much shorter than the conventional mechanical switches. The advance of semiconductors increases the switching frequency and voltage-ampere ratings of the solid switches and facilitates the applications. FACTS controllers have many configurations. In general, they can be categorized into shunt-connected controllers, series-connected controllers and their combinations.

1. Shunt-connected controllers: FACTS controllers can be impedance type, based on thyristors without gate turn-off capability, which are called Static Var Compensator (SVC) for shuntconnected application. Another type of FACTS controllers is converter-based which is usually in the form of a Static Synchronous Compensator (STATCOM). Static Var Compensator is “a shunt-connected static Var generator or absorber whose output is adjusted to exchange capacitive or inductive current so as to maintain or control specific parameters of the electrical power system. SVC is based on thyristors without gate turn-off capability. SVC includes two main components and their combination: (1) Thyristor-controlled and Thyristorswitched Reactor (TCR and TSR); and (2) Thyristor- switched capacitor (TSC). Figure 2.4 shows the diagram of SVC.

Fig. 2.4Static VAR Compensators (SVC): TCR/TSR, TSC, FC and Mechanically Switched Resistor

15

TCR and TSR are both composed of a shunt-connected reactor controlled by two parallel, reverse-connected thyristors. TCR is controlled with proper firing angle input to operate in a continuous manner, while TSR is controlled without firing angle control which results in a step change in reactance. TSC shares similar composition and same operational mode as TSR, but the reactor is replaced by a capacitor.

2. Series-connected controllers: As shunt-connected controllers, series-connected FACTS controllers can also be divided into either impedance type or converter type. The former includes Thyristor-Switched Series Capacitor (TSSC), Thyristor-Controlled Series Capacitor (TCSC), Thyristor-Switched Series Reactor, and Thyristor-Controlled Series Reactor. The latter, based on VSI.

2.4. BASIC DESCRIPTION OF FACTS DEVICES: 2.4.1. Fixed capacitor thyristor controlled reactor (FCTCR):

Fig. 2.5 Fixed Capacitor Thyristor Controlled Reactor

Static VAR compensated FACTS device are the most important device and have been used for a number of years to improve voltage and power flowthrough the transmission line by resolving dynamic voltage problems. SVC is shunt connected static generator/absorber. Utilities of SVC controller in transmission line are 16

many: a) provides high performance in steady-state and transient voltage stability control, b) dampen power swing, c) reduce system loss, d) Control real and reactive power flow. In FC-TCR,a capacitor is placed in parallel with a thyristor controlled reactor. Is, Ir and Ic are system current, reactor current and capacitor current respectively which flows through the FC-TCR circuit. Fixed capacitor- Thyristor controlled reactor (FC-TCR) can provide continuous lagging and leading VARS to the system. Circulating current through the reactor (Ir) is controlled by controlling the firing angle of back-back thyristor valves connected in series with the reactor. Leading var to the system is supplied by the capacitor. The current in the reactor is varied by the method of firing delay angle control method. The constant capacitive var generation (Qc) of the fixed capacitor is opposed by the variable var absorption (QL) of the thyristor controlled reactor, to yield the total var output (Q) required. At the maximum capacitive var output, the thyristor-controlled reactor is off. To decrease the capacitive output, the current in the reactor is increased by decreasing delay angle α. At zero var output, the capacitive and inductive currents become equal and thus both the vars cancels out. With further decrease of angle α, the inductive current becomes larger than the capacitive current, resulting in a net inductive output.

2.4.2. Thyristor controlled series capacitor (TCSC):

Fig. 2.6Thyristor Controlled Series Capacitor

17

Thyristor controlled series capacitor (TCSC) is very important series compensator like SSSC. Specially in this FACTS (Flexible alternating transmission system) device, thyristor with gate turn-off capability is not required. Figure 6 shows schematic diagram of a TCSC controller. In TCSC, capacitor is inserted directly into the transmission line and TCR are mounted in parallel with the capacitor. As the capacitor is inserted in series with the line, there is no need of using high voltage transformer and thus it gives better economy. Firing angle of back to back thyristorsare controlled to control the reactor. At 180° firing angle TCR, is nonconducting and at 90° firing angle TCR is in full conduction. It is a one-port circuit in series with transmission line; it uses natural commutation; its switching frequency is low; it contains insignificant energy storage and has no DC-port. Insertion of a capacitive reactance in series with the line’s inherent inductive reactance lowers the total, effective impedance of the line and thus virtually reduces its length. As a result, both angular and voltage stability gets improved. Furthermore, in contrast to capacitors switched by circuit breakers, TCSC will be more effective because thyristorscan offer flexible adjustment, and more advanced control theories can be easily applied.

Operation of TCSC: TCSC operates in different modes depending on when the thyristors for the inductive branch are triggered. The modes of operation are as listed: 

Blocking mode: Thyristor valve is always off, opening inductive branch, and effectively causing the TCSC to operate as Fixed series compensation (FSC)



Bypass mode: Thyristor valve is always on, causing TCSC to operate as capacitor and inductor in parallel, reducing current through TCSC



Capacitive boost mode: Forward voltage thyristor valve is triggered slightly before capacitor voltage crosses zero to allow current to flow through inductive branch, adding to capacitive current. This effectively increases the observed capacitance of the TCSC without requiring a larger capacitor within the TCSC

Because of TCSC allowing different operating modes depending on system requirements, TCSC is desired for several reasons. In addition to all of the benefits of 18

FSC, TCSC allows for increased compensation simply by using a different mode of operation, as well as limitation of line current in the event of a fault. The benefits of TCSC are seen in its ability to control the amount of compensation of a transmission line, and in its ability to operate in different modes. These traits are very desirable since loads are constantly changing and cannot always be predicted.

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CHAPTER 3

SIMULATION

20

3.1. INTRODUCTION: MATLAB/SIMULINK environment is used for this comparative study to model and simulate FC-TCR type SVC and TCSCconnected to a simple transmission line. First, power flow results are obtained and then power (real and reactive power) profiles have been studied for an uncompensated system and then compared with the results obtained after compensating the system using the above-mentioned FACTS devices. The simulation results demonstrate the performance of the system for each of the FACTS devices in improving the power profile and thereby voltage stability of the same.

3.2. PERFORMANCE ANALYSIS OF FACTS DEVICES: 3.2.1. Uncompensated system model Figure 3.1 shows the basic transmission (11kV) model of an uncompensated system. This model consists of current measurement block, voltage measurement block, real and reactive power block and scopes.

Scope2

Scope3

C ur1

+ v -

C ur

i + -

+ -i

+v -

Series RLC Branch1 Vol1

Scope4

Vol V

Scope PQ

I

Series RLC Branch

Active & Reactive Power Series RLC Load

AC Voltage Source Scope5

C o ntinuo us p o we rg ui

Fig. 3.1 Uncompensated system model

21

<> <>

Scope1

11kv voltage is supplied from the AC voltage source to the system. Source impedance (0.01+0.001) Ω, Line impedance (5+0.023) Ωand load is kept constant for

the

above

transmission

line

model.

Simulation

is

done

using

MATLAB/SIMULINK. Current measurement block is used to measure the instantaneous source and load current flowing through the transmission line, Voltage measurement block is used to measure the source and load voltage. Real and reactive power in load side is measured using active and reactive power measurement block. Scopes display results after simulation. Above model provides three scopes: one displays the source voltage (V) and source current (I), second one displays real (P) and reactive (Q) power and third one displays load voltage (V1) and load current (I1) after simulation.

3.2.2. Compensated system: 3.2.2.1. FC-TCR Compensated The SIMULINK model of FC-TCR (SVC) with line voltage of 11KV is shown below: Itcr

i2

Series RLC Branch

i1

i + -

+ -i

z

+ - v

V1

rl2

V

P PQ

I

Active & Reactive Power1

Pulse1

Q g

a k

k

m

AC Voltage Source

m

C1 S

a

g

Th1Th2

Pulse 2 Continuous Ith,Vth

powergui

Fig. 3.2 FC-TCR Compensated system

Line impedance is kept at (0.01+0.001) Ω and load is fixed. Current measurement block is used to measure the instantaneous source and load current flowing through the transmission line, Voltage measurement block is used to measure the source and load voltage. Real and reactive power in load side is measured using active and reactive power measurement block. Scopes display results after simulation. 22

3.2.2.2. TCSC Compensated system The model shows a Thyristor Controlled Series Capacitor connected to the system. In TCSC simulation model, inductor is fixed at 100mH and results are obtained for different capacitor values.

Fig. 3.3TCSC compensated system

Current measurement block is used to measure the instantaneous source and load current flowing through the transmission line, Voltage measurement block is used to measure the source and load voltage. Real and reactive power in load side is measured using active and reactive power measurement block.

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CHAPTER 4

RESULTS AND DISCUSSION

24

4.1. SIMULATION RESULTS OF UNCOMPENSATED SYSTEM: The Real power and the Reactive Powers measured in the load are 0.39MW and 0.81MVAR as shown in Figure 4.1 (a & b). This power flow is obtained without any compensation. By introducing FACTS Controllers in the transmission line, the power flow can be increased.

Fig. 4.1 (a) Real power flow

Fig. 4.1 (b) Reactive power flow

4.2. FC-TCR COMPENSATED SYSTEM: 25

Results obtained after simulation of FC-TCR model at capacitor value of 300uF is shown below:

Fig. 4.2 (a) Real power flow

Fig. 4.2 (b) Reactive power flow

Real and reactive powers have been obtained for a fixed value of TCR inductance (100mH) and for different values of the capacitor. Improvement obtained in real and reactive power with changes in capacitor values are tabulated below:

S. No.

Capacitor (uF)

P (MW)

Q (MVAR)

1.

50

0.488

0.72

2.

300

0.68

0.96

3.

500

0.91

1.27

Table 4.1: variation of power flow with change in capacitance

26

Thus from the above table we see that power flow through the system increases proportionally with increase in capacitance. Real power varies from 0.488MW to 0.91MW and reactive power varies from 0.72MVAR to 1.27MVAR with variation in capacitance value. In this system results have been obtained by varying the capacitor value from 50 μF to 500μF.

4.3. TCSC COMPENSATED SYSTEM: Results obtained after simulation is shown below:

Fig. 4.3 (a) Real power flow at C=300uF

Fig. 4.3 (a) Reactive power flow at C=300uF

27

For TCSC too, increasing the value of capacitance results in continuous compensation of real and reactive power without deterioration.

4.4. DISCUSSION: Comparison between the devices: Table 4.2: Comparison of power flow between above FACTS devices

FACTS device

P (MW)

Q (MVAR)

Without any device

0.39

0.81

FC-TCR

0.68

0.96

TCSC

0.63

0.89

From the table, it is seen that reactive power improvement will vary with change in capacitance. Increased rating of capacitor means increase the cost of equipment. From the table, we conclude that FC-TCR will give optimum performance at capacitor rating of 300µF.

Fig. 4.4Variation of power flow withchange in capacitance

The above graph shows the variation of reactive power profile with change in capacitance for an FC-TCRtype SVC connected to the system. Reactive power flows improves proportionally with increase in capacitance value. In this case, optimum performanceis obtained for capacitor value of 500µF.

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Fig. 4.5Variation of power flow withchange in capacitance

Above graph shows compensation of the system for varying capacitor values when a TCSC is connected toit. We can see that increase in the value of capacitanceresults in improvement of reactive power. This project presents performance analysis of all the above FACTS devices and an elaborate comparison between their performances. Power flow and voltage profile are seen to improve with all the compensating devices.Results show that in case of FC-TCR compensation, reactive power flow improves proportionally with increasing capacitance and is maximum at maximum value of capacitance.TCSC behaves in a similar way a FC-TCR and gives best performance at high value of capacitor. Power flow is seen to improve with all the compensating devices.

29

CHAPTER 5

CONCLUSION

30

MATLAB/SIMULINK environment is used for this comparative study to model and simulate FC-TCR type SVC and TCSCconnected to a simple transmission line. This project presents performance analysis of all the above FACTS devices and an elaborate comparison between their performances. The project describes the control strategy for Real and Reactive powers of the transmission line using FC-TCR and TCSC. In case of FC-TCR, the control is achieved by controlling the current through the thyristor controlled reactor by varying the phase of the thyristor switch. Power flow and voltage profile are seen to improve with all the compensating devices.Results show that in case of FC-TCR compensation, reactive power flow improves proportionally with increasing capacitance and is maximum at maximum value of capacitance.TCSC behaves in a similar way as FC-TCR and gives best performance at high value of capacitor. Power flow is seen to improve with all the compensating devices.

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REFERENCES: [1] SamimaAkter, AnulekhaSaha, Prof. Priyanath Das, “ Modelling, Simulation And Comparison Of Various FACTS Devices In Power System”, International Journal of Engineering Research & Technology (IJERT), Vol. 1 Issue 8, October – 2012. [2] N.G Hingorani& Laszlo Gyugyi, “Understanding FACTS: concepts and technology of flexible AC transmission System”, IEEE Press, New York, 2000. [3] D. Murali, Dr. M. Rajaram& N. Reka, “Comparison of FACTS Devices for Power System Stability Enhancement”, International Journal of Computer Applications, Volume8-No.4, October 2010.

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