IEEE Paper Template in A4 (V1)

DOI 10.4010/2016.569 ISSN 2321 3361 © 2016 IJESC

Research Article

Volume 6 Issue No. 3

A Study to Improve the Power Quality of Transmission Line Using TCSC Uma Rathore1, Dr. Dharmendra Kumar Singh2 M.Tech Scholar1, Assistant Professor (Member of IEI) 2 Power System Engineering1, Electrical & Electronics Engineering2 Dr.C.V.Raman University, Bilaspur, India [email protected], [email protected] Abstract: The paper defines how to improve the quality of power quality, power quality is one of the most important aspects in power system. The distortion parameters such as Voltage sage, voltage swell, flickers, and harmonics causes the power quality problems. Thyristor control series capacitor is the facts device which is used to compensate all these problems. The use of electronic devices causes the power quality problem ,equipment such as large industrial drive ,automatic voltage regulator generate significantly voltage and current harmonics and create excessive voltage fluctuations in power . The application of custom power devices gives the solution of such problem i.e. TCSC. TCSC is power electronics device used to enhance the power transfer capability near thermal limit without affecting the stability. Keywords: Facts, Power quality, TCSC, voltage stability. Voltage swell, Voltage Sags & Harmonics. 1. INTRODUCTION The most important aspect of using Flexible AC Transmission system (FACTS) controllers for enhancing power system stability is well known. The uses of these FACT devices give grid planners and operators a greater flexibility regarding the type of control actions that can be taken at any given time. Thyristor Controlled Series Capacitors (TCSC) is one which have been widely studied and reported in the technical literature, and have been shown and used in practice to significantly enhance system stability. Moreover In dynamic applications of TCSCs, various control techniques and designs have been proposed for damping power oscillations to improve system dynamic response, whereas for steady state control, the main interest of users and researchers has been the use of the this controller for power flow control in transmission lines, usually considering optimal scheduling strategiesThe high pass filter will work on high-frequency components of images. Image enhancement techniques emphasize specific image features to improve the visual perception of an image [2].Filtering technique can not remove more than one noise at the same time. Most of the available technical literature in TCSC usually deals with steady state and, dynamic control and applications independently. However, to fully understand and properly utilize these types of controllers, a number of control tasks for both dynamic and steady state system improvement must be jointly considered. Since the time frames of the different control actions comprise a wide range of system responses, a hierarchical control scheme should be preferably considered For the controller. In the case of a TCSC, such a scheme should consider the different control levels acting on the same control variable, which in this paper is assumed to be the fundamental frequency equivalent impedance, as this is the control variable most commonly studied in the literature. In this kind of hierarchical control design, adverse interactions between the different control levels may be expected when not

International Journal of Engineering Science and Computing, March 2016

properly coordinated the main aim is to analyses the design of a hierarchical TCSC controller for stability enhancement, taking into account interactions among the different control levels. A linear dynamic compensator with various input signals for damping power oscillations is proposed and studied based on a typical stability model of the TCSC. Since large-disturbance stability improvement is of major concern here, tuning of the control parameters is mainly carried out via simulations of severe fault conditions. 1.1 Voltage Swells A voltage swell is an increase in the RMS voltage above the nominal voltage or a sliding reference voltage. The increase lasts from half a cycle to several seconds. Switching off large loads, capacitor banks. 1.2 Voltage sag Voltage sags are related to power quality problems is usually leads to the fault in the power system and switching actions including open and close interval to isolate the faulted sections. They are characterized by RMS voltage variations outside the normal operating range of voltages. Voltage sag is a short-duration reduction in RMS voltage caused by faults on the power system and the starting of large loads, such as motors. Voltage sag causes a complete loss of voltage and a common result of the actions taken by utilities to clear transient faults on their systems [11]. 1.3 Harmonics Harmonic distortion is an interrupt caused by nonlinear devices in the power system. A nonlinear device is one in which the current is not proportional to the applied voltage. Illustrates this concept by the case of a sinusoidal voltage applied to a simple nonlinear resistor in which the voltage and current vary according. While the applied voltage is perfectly

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sinusoidal, the resulting current is distorted. Increasing the voltage by a few percent may cause the current to double and take on a different wave shape. This is the source of most harmonic distortion in a power system. [12]. 2. THYRISTOR CONTROLLEO SERIES CAPACLTOR TCSC consists a capacitor in parallel with a thyristor controlled reactor (TCR) as shown in Fig.1, [3]. An actual TCSC system usually comprises a cascaded combination of many. TCSC modules together with a fixed-series capacitor. TCSC vary the electrical length of the transmission line which enables it to be used to provide fast active power flow regulation. It also increases the stability margin of the system and has proved very effective in damping Sub Synchronous Resonance (SSR) and power oscillations [3]. The simpler TCSC model exploits the concept of a variable series reactance. The series reactance is adjusted automatically, within limits, to satisfy a specified amount of active power Reactance curve of TCSC can be obtained by using following equations.

2.1 FACT DEVICE FACT device offered to enhance the capacity of transmission lines without having to construct any new transmission lines. The major drawback in using thyristor switches is that the control for turn-off capability is not possible. Hence in a cycle, switching more than once is not possible. FACT DEVICES

THYRISTOR VALVO

VOLTAGE SOURCE CONVERTOR

THYRISTOR CONTROLLED SERIES COMPENSATOR

STATIC SYNCHRONOUS SERIES COMPENSATOR

STATIC VAR COMPENSATOR

STATIC SYNCHRONOUS COMPENSATOR

Fig 3. Overview of Major FACTS Devices

FACTS devices are more suitable for Power flow control, Increase of transmission capability, Voltage control, Reactive power compensation, Stability improvement, Power quality improvement, Flicker mitigation and Interconnection of renewable and distributed generation and storages. The use of FACTS devices is achieved through switched or controlled shunt compensation, series compensation or phase shift control. The devices work electrically as fast current, voltage or impedance controllers. The reaction time allowed by power electronic is very short and goes down to far below one second. A structured overview on FACTS devices is given below. [7] Fig 1. Thyristor Controlled Series Compensator

3. Proposed Methodology

2

XTCSC = -Xc+ C1(2(-)+sin(2(-)))-C2 cos (-) ( tan( (-))-tan(-) (1) Where C1= (Xc + XLC)/  XLC= XCXL/XC-XL

C2=4 (X2LC/XL) = XC/XL

System design starts with 3 phases 11kv, 100 km long transmission system is considered as a case study for improving the power flow moreover under 33kv and 66kv system will be tested using MATLAB software. Data required for developing the SIMULINK model shown in fig 4 which analysis the voltage swell and harmonic of certain time pride which are shown in fig 5 FFT analyses. In fig 5 the harmonics are presented which are reduced using TCSC. Model -1 shown in Fig. 4 is a traditional transmission power system which comprised of three phase generator, load and circuit breaker for switching purpose. The transmission line has three different voltage levels i.e. 11 kV, 33 kV and 66 kV with different load and length. If the switching operation arise voltage sag, swell and harmonics will be generated in the transmission line. Model- 2 shown in Fig. 6 has the same configuration with model-1. In addition to the discrete pulse width modulation triggered thyristor controlled switch capacitor (TCSC) is connected in series with transmission line to compensate the voltage sag, swell and harmonic. Fig 7 represent that the harmonics are reduced using TCSC.

Fig 2. Characteristic curve of TCSC


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Fig 4. MAT-LAB Model of 11kV transmission system

Fig 7. MAT LAB analysis of swell and harmonics The flowchart of the proposed model is shown below it is consist of different voltage source i. e. 11kv, 3kv and 66kv with different load and length. The generated voltage swell, sag and harmonics are tested under model1 and model2. A comparative study is done under model1 and model it seems that model2 is more effective for transmission line. Start

Source Voltage 11kv, 33kv & 66kv

Model1 Without TCSC

Model2 With TCSC

Voltage swell, Sag and Harmonics

Voltage Swell, Sag and Harmonics

Fig 5. MAT LAB analysis of swell and harmonics

Comparative Study

Output Fig 8. Flow Chart of Proposed Methodology

Fig 6. Model of 11kV transmission system using TCSC


Simulation of Without TCSC and with TCSC is based on different conditions. The circuit breakers are suddenly opened during abnormal, power switching and fault conditions.

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The voltage sag is produced at the receiving end for very short duration in the three phase transmission lines. Voltage sags and interruptions are related to power quality problems. Both are usually the result of faults in the power system and switching actions to isolate the faulted sections. The circuit breakers are suddenly closed during power switching and fault conditions. The voltage swell is produced at very short duration in the three phase transmission lines. Swell is defined as an increase to between 1.1 and 1.8 pu in RMS voltage or current at the power frequency for durations from 0.5 cycle to 1 min. as with swells are usually associated with system fault conditions. The proposed simulation table is given below.

S.N o

Frequen cy (Hz)

Sending End Voltage (kV)

Voltage SagSwell Time (sec)

Length Of Transmissio n Line ( km )

Load In MW

11

0.6

100

30

33

0.6

110

300

66

0.6

120

1000

[3] C. Gama and R. Tenorio, “Improvements for Power System Performance: Modeling, Analysis and Benefits of TCSCs,” Proc. IEEE/PES Winter Meeting, Singapore, January 2000. [4] N. Martins, H. Pinto, and J. Paserba, “Using a TCSC for Power Scheduling and System Oscillation Damping–Small Signal and Transient Stability Studies,” Proc. IEEE/PES Winter Meeting, Singapore, January 2000. [5] “Impact of Interactions Among System Controllers,” CIGRE Task Force 38.02.16, November 1999. [6] G. Hingorani and L. Gyugyi, Understanding FACTS: Concepts and Technology of Flexible AC Transmission Systems, IEEE Press, 1999. [7] S.Sreejith, Sishaj P Simon, M P Selvan. "Power Flow Analysis Incorporating Firing Angle Model Based TCSC".

50 1 50 2 50 3

Table1. Proposed Simulation of Model-1 & Model-2 4. CONCLUSION System is developed in Simulink. In order to reduce the system voltage drop in the line and to improve the power flow. A TCSC are implemented on considered test system for variable loads. The constant power control circuit is developed to tune the TCSC for power flow improvement. The transmission system transfers the required power demanded by the load by implementing TCSC compensator. Though control circuit is not designed for transient stability and power oscillation damping, some transients and oscillations are observed. Further work may carry out to suppress the oscillations and transients in the system. For all varying loads, load voltage is maintained within the limit by reducing the net voltage drop in the transmission system.

[8] S. D. Wadhai ,Dr. N. D. Ghawghawe , "Power Flow Control by Using TCSC Controller in Power System", Electronics&Communicauou CenferenceProceeding I 3-15 , Jan-2011. [9] R. Mohan Mathur and Rajiv.K.Verma.: "Thyristor-based FACTS controllers/or e/ectrica/ transmission systems", John Wiley and Sons, 2002. [10] S. Meikandasivam, Rajesh Kumar Nema, Shailendra Kumar Jain,"Behavioural Study of TCSC Device - A MATLAB/Simulink Implementation", World Academy of Science, Engineering and Technology 45,Jan-2008. [11] GABRIEL OLGUIN “Voltage Dip (Sag) Estimation in Power Systems based on Stochastic Assessment and Optimal Monitoring” 2005 ISBN 91 7291-594-3 Doctor Savhandlingar vid Chalmers Tekniska Högskola Ny serie nr 2276 ISSN 0346-718. [12] Alexis Polycarpou “Power Quality and Voltage Sag Indices in Electrical Power Systems” in Frederick University Cyprus ,Unit 405, Office Block, Hotel Equatorial Shanghai No.65, Yan An Road (West), Shanghai, 200040, China.

REFERENCES [1] “Load Flow Control in High Voltage Power Systems Using FACTS Controllers,” CIGRE Task Force 30.01.06, January 1996. [2] “Thyristor Controlled Series Compensation,'' CIGRE Working Group 14.18, December 1997.


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