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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 3, March 2012)

223

Modelling and Analysis of TCSC Controller For

Enhancement of Transmission Network

J. V. Kadia

1

, J. G. Jamnani

2

1, 2 Department of Electrical Engineering

Institute of Technology, Nirma University Ahmedabad, Gujarat

1

jiksh111@gmail.com 2jg.jamnani@nirmauni.ac.in

Abstract— The method of series compensation is used since

long back for improvement of power transfer capability of transmission line with the development of power electronics devices and control engineering TCSC becomes a multitasking controller to improve overall characteristic of an electrical power network in normal as well as faulty condition. In this paper, TCSC controller has been modeled and its performance has been analyzed for various events such as fault on long transmission line, sub synchronous resonance. The behavior of TCSC is analyzed for open and close loop modes. The results are verified by different power system parameter values using software package PSCAD 4.2.

Keywords- FACTS, Thyristor Controlled Series Capacitor (TCSC), Real Power, Sending End Current, Receiving End Voltage.

I. INTRODUCTION

The concept of FACTS (Flexible Alternating Current Transmission Systems) was proposed by EPRI (Electric Power Research Institute) in the mid of 1980s. The main problem with mechanical devices is that control cannot be initiated frequently, at that time the FACTS technology gives new opportunities for controlling power. FACTS controllers are used to control the interrelated parameters that govern the operation of transmission system such as series impedance, shunt impedance, current, voltage, phase angle. Further the damping of small signal oscillations can also be achieved. The compensation is done using FACTS technology, viz. Thyristor Controlled Series Capacitor (TCSC). TCSC provides a wide range of compensation by changing the angle and also limits the fault current in case of faults. In inductive mode TCSC provide protection against various kinds of faults.

Also TCSC helps increasing the power transfer and maintain the power system stability by improving the load angle. In this paper, EHV transmission line with TCSC has been modeled in the software package PSCADV4.2 various parameters of transmission lines like power transfer capability, sending end voltage, receiving end voltage have been analyzed.

In this paper, the concept of series FACTS controller like TCSC is discussed. In section II, the typical data of transmission line parameters are given. In section III, the conceptual and mathematical model of TCSC is described. In section IV, the transmission line using series compensation is model in PSCAD software package. Also the results of TCSC in open loop and close loop conditions are discussed. In section V, the comparison results of different conditions like open loop and close loop for TCSC are discussed.

II. SYSTEM DESCRIPTION

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 3, March 2012)

[image:2.612.46.562.102.291.2]

224 Figure 1. Model of Uncompensated Transmission Line in PSCAD.

Figure 2(a). Active Power.

Figure 2(b). Receiving End Voltage.

Figure 2(c). Sending End Current

Figure 2. Uncompensated Transmission Line Parameters During LLLG Fault at 1 Sec.

The real power, sending end voltage, receiving end current of uncompensated transmission line during LLLG fault occurs at 1 sec shown in fig2. At the fault point the real power of uncompensated line decreases and after the fault cleared power increases to maintain the value before faults. After the faults the real power oscillated some time that indicated the stability of system not maintain. The magnitude of receiving end voltage decreases that indicates the voltage drop on transmission line and the current of transmission line are increases 1.5 to 2 times of fundamental current.

III. MODELLING OF TCSC

Thyristor controlled series compensator (TCSC) device is a series compensator to govern the power flow by compensating the reactance of transmission line. Both capacitive and inductive reactance compensation are possible by proper selection of capacitor and inductor values of the TCSC device which can be realized through reactance equation. A TCSC which consist of a series compensating capacitor(C) shunted by a Thyristor controlled reactor (TCR). TCR is a variable inductive reactor (XL ()) tuned at

firing angle. The variation of XLwith respect to  can be given as (1, 2) [3]-

 

L L

X

X

2

sin2

 

 

(1)

1

2 fC

C

X

(2)

[image:2.612.46.290.324.690.2] [image:2.612.336.556.575.699.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 3, March 2012)

225 Figure 4. Equivalent circuit of TCR

For the variation of  from 0 to 90°, XL () varies from

actual reactance (XL) to infinity. This controlled reactor is

connected across the series capacitor, so that the variable capacitive reactance, as fig. 3 is possible across the TCSC which modify the transmission line impedance. Effective TCSC reactance Xtcsc with respect to alpha () can be given

as (3-7)-

))

tan(

))

(

tan(

)(

(

cos

)))

(

2

sin(

)

(

2

(

)

(

2 2 1

C

C

X

X

TCSC C

  1 C LC

X

X

C

   2

2

4

LC

L

X

C

X

   C L LC C L

X X

X

X

X

 C L

X

X

  

Figure 5. Equivalent circuit of TCSC.

The effective reactance (XTCSC ()) of TCSC operates in

three region, inductive region, capacitive region and resonance region. Inductive region starts increasing from TCR reactance XL||XC value to infinity and decreasing from

infinity to capacitive reactance XC for capacitive region.

Between the two regions, resonance occurs. [3]

Range of firing angle () Region 90º Llim Inductive region

Llim Clim Resonance region

[image:3.612.74.262.159.242.2]

Clim  180º capacitive region

Figure 6. Resonance condition of TCSC.

IV. RESULTS AND DISCUSSION

[image:3.612.289.550.228.532.2] [image:3.612.51.285.375.695.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 3, March 2012)

226 Figure 7. Model of Compensated Transmission Line Using PSCAD.

A. OPEN LOOP 1) Inductive Region

In this region, The TCSC operated in the bypassed Thyristor mode. The TCSC normally connected at that region. The gate pulses are applied as soon the voltage across the Thyristor reaches zero and become positive. However the net current through the module is inductive.

Figure 8(a). Real Power

Figure 8(b). Receiving End Voltage

Figure 8(c). Sending End Current

[image:4.612.40.588.148.713.2] [image:4.612.51.573.161.365.2] [image:4.612.294.567.166.681.2] [image:4.612.48.291.548.657.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 3, March 2012)

227

Faults occur on transmission line when TCSC operated in inductive region then the TCSC inductor come in to the picture and the function of TCSC inductor is limit the fault current. Fig. 7(c) Shows the current wave form it is indicating that during the fault the short circuit current limited by the inductor of TCSC.

2) Sub synchronous resonance region

In this region, the alpha varies from 130° to 140°. This is called the sub synchronous resonance (SSR) region. In this region the net reactance and capacitance of the TCSC nearly equals. So it is act as a resistive circuit at that region the power factor reach nearly to unity.

Figure 9(a). Real Power

Figure 9(b). Receiving End Voltage

Figure 9(c). Sending End Current

Figure 9. Parameters of Transmission Line in Resonance Region During LLLG Fault at 1 Sec.

3) Capacitive Region

In this region, The TCSC is fully conducted. The value of net capacitive reactance of TCSC is increases and the net reactance of transmission line further reduces compare to inductive region. So that the power transfers capacity and the voltage stability increases in that region.

Figure 10(a). Real Power

Figure 10(b). Receiving End Voltage.

Figure 10(c). Sending End Current.

Figure 10. Parameters of transmission line in capacitive region during LLLG fault at 1 sec.

[image:5.612.322.564.202.595.2] [image:5.612.47.288.294.659.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 3, March 2012)

228 B. CLOSE LOOP

In this control scheme three controls are available current control, voltage control, impedance control. Here impedance control of close loop scheme used.

Figure 11. Reactance Control Method of TCSC for Close Loop Control.

The transmission line voltage and current are used for a measurement of reactance in transmission line. The reference value of reactance of transmission line is choosing from the standard. The measure value of reactance compare against the reference value of reactance to obtain the error signal. This error signal fed to the pi controller for the filtering the gain of pi controller is 2 and the time constant of 0.5sec. This value gives the alpha for firing circuit of Thyristor gate.

Figure 12(a). Real Power.

Figure 12(b). Receiving End Voltage.

Figure 12(c). Sending End Current.

Figure 12. Parameters of Transmission Line During LLLG Fault at 1 Sec for Close Loop Control.

[image:6.612.322.564.119.508.2] [image:6.612.51.291.216.486.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 3, March 2012)

229

V. COMPARISON ANALYSIS

Parameter Un

Comp. line

Compensated line Open loop

Close loop

Alpha 90° 135° 180°

Real power per phase(MW)

164 210 178 215 175

Receiving end voltage per

phase

(kV)

220 226 227 229 225

Sending end current per phase(kA)

705 590 650 570 680

Table 1: parameters of transmission line in different condition for LLLG fault at 1 sec.

The simulation results of uncompensated lines and compensated lines gives idea about the transmission line parameters are shown in the table1. Compensated transmission line system the power transfer capacity increases compare to the uncompensated transmission lines. The voltage drop decreases in compensated transmission lines to give the receiving end voltage nearly same to the sending end voltage and improve the stability of the system.

References

[1] N .G .Hingorani, Laszlo Gyugyi, "Understanding FACTS", IEEE Press, 2001, pp 223-238

[2] R. M. Mathur, R. k. Verma, "Thyristor based FACTS controllers for electrical transmission systems", IEEE Press, 2002, pp 277-288. [3] S. Meikandasivam, Rajesh Kumar Nema, Shailendra Kumar Jain,

"selection of TCSC parameters: capacitor and inductor", IEEE 2011. [4] Xiaobo Tan, Luyuan Tong, Zhongdong Yin, Dongxia Zhang,

Zhonghong Wang, "characteristic and firing control of thyristor controlled series compensation installations", IEEE 1998.

[5] Milad Dowlatshahi, Mehdi Moallem, Hadi Khani, "A new approach for voltage profile enhancement in distribution power system using fixed and thyristor controlled series capacitor",IEEE 2010.

[6] Zhao Xueqiang, “study of TCSC model and prospective application in the power systems of china” IEEE international conference on power electronics and drive systems, hong kong, july 1999. [7] J. R. S. S. Kumara, A.M.T.K. Bandara, A. Atputharajah, J. B.

Ekanayake, "design and testing of an TCSC for distribution network application", ICIIS first international conference on industrial and information systems, srilanka, august 2006.

VI. CONCLUSION

[image:7.612.48.300.177.382.2]

Figure

Figure 2(a).
Figure 4.    Equivalent circuit of TCR
Figure 7.    Model of  Compensated Transmission Line Using PSCAD.
Figure 9(a).
+3

References

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