International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved

International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved

240 ABSTRACT

Transmission networks of modern power systems are becoming increasingly stressed because of growing demand and restrictions on building new lines. One of the consequences of such a stressed system is the threat of losing stability following a disturbance. Flexible ac transmission system (FACTS) devices are found to be very effective in a transmission network for better utilization of its existing facilities without sacrificing the desired stability margin. Flexible AC Transmission System (FACTS) such as Static Synchronous Compensator (STATCOM) and Static VAR Compensator (SVC), employ the latest technology of power electronic switching devices in electric power transmission systems to control voltage and power flow. A static synchronous compensator (STATCOM) is a shunt device of the flexible AC transmission systems (FACTS) family . The STATCOM regulates voltage at its terminal by controlling the amount of reactive power injected into or absorbed from power system. When system voltage is low, STATCOM generates reactive power and when system voltage is high it absorbs reactive power.

The power system stabilizer (PSS) is a control device provides a maximum power transfer and optimal power system stability.

PSS has been widely used to damp electromechanical oscillations

that occur in power systems due to disturbances. If no adequate damping is available, the oscillation will increase result in instability case. Shunt static var compensator (SVC) and Static Synchronous Compensator (STATCOM) is also used to improve system stability. This paper focus on the significance of SVC- PSS and STATCOM_PSS to improve the transient stability of power system in abnormal condition. This paper shows the simulation result of model for fault condition with PSS and without PSS, with SVC and with Statcom.

Keyword:-Facts, Statcom, Svc

1 INTRODUCTION

Modern electric power system is facing many challenges due to day by day increasing complexity in their operation and structure. In the recent past, one of the problems that got wide attention is the power system instability. With the lack of new generation and transmission facilities and over exploitation of the existing facilities geared by increase in load demand make these types of problems more imminent in modern power systems.

Demand of electrical power is continuously rising at a very high rate due to rapid industrial development [1]. To meet this demand, it is essential to raise the transmitted power along with the existing transmission facilities. The need for the power flow control in electrical power systems is thus evident. With the increased loading of transmission lines, the problem of transient stability after a major fault can become a transmission power limiting factor. The power system should adapt to momentary system conditions, in other words, power system should be flexible. In an ac power system, the electrical generation and load must balance at all times up to some

COMPARIVE STUDY OF TRANSIENT

IMPROVEMENT OF TWO MACHINE SYSTEM USING PSS BASED STATCOM AND SVC

CONTROLERS.

Arindam Sikdar

¹

, Basudeb Mondal

²

1

Student , M-tech, Dr B C Roy Engineering College.

2

Assistant Professor, Dept of EE, Dr B C Roy Engineering College

International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved

241

extent, the power system is self regulating .If generation is less than load ,the voltage and frequency drop, and thereby the load goes down to equal the generation minus transmission losses. But there are only a few percent margins for such a self regulation. Hence there is chance of system collapse. Generator excitation controller with only excitation control can improve transient stability for minor faults but it is not sufficient to maintain stability of system for large faults occur near to generator terminals. Thus, this requires a review of traditional methods and the creation of new concepts that emphasize a more efficient use of already existing power system resources without reduction in system stability and security.

SYSTEM MODEL:-

This paper simulation of a common system model consists of two synchronous generators:

A. Generator

Fig.1 show the two-area system used in the study. The system consists of two different areas. Each area includes two generating units equipped with fast static exciters. All two generating units are represented by the same dynamic model.

Generation G1: Nominal power 1000MW, line-to-line voltage 13,8kV, frequency 60Hz.

Generation G2: Nominal power 5000MW, line-to-line voltage 13,8kV, frequency 60Hz.

SIMULINK MODEL:-

Graphs:-

Fig3.1 :-Plot showing rotor angle and load angle w.r.t time showing of Statcom And SVC for Multiband mode PSS.

C. Load

Load1: Three-Phase Parallel RLC Load P=10 MW, Q L =.2kVAr, QC = 4kVAr.

Load2: Three-Phase Series RLC Load P= 500 MW, Q L =5kVAr, Q

C = 1kVAr.

B. Transformer

Three-phase transformer T1:1000MVA, 13.8 kV/500 Kv.

Three-phase transformer T2: 5000MVA ,13.8 kV/500 Kv

Load3: Three-Phase Parallel RLC Load P= 4500 MW, Q L = 3kVAr, Q C = 1kVAr.

Fault Breaker block:-

A Fault Breaker block is connected at bus B1. we will use it to program different types of faults on the 500 kV system and observe the impact of the PSS and SVC, STATCOM on system stability.

Power System Stabilizers (PSS):-

The power system stabilizer is a control device use to damp out low frequency oscillations [11]. Such modes are known as interarea or local modes. The parameters of the PSS are tuned on-line to suppress these modes. The design of the PSS is still made on the basis of a single machine infinite bus system (SMIB) system.

International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved

242

Fig 3.2 :-Plot showing voltage and reactive power w.r.t time for

Statcom And SVC for Multiband mode PSS.

Fig3.3 :-Plot showing rotor angle and load angle w.r.t time for Statcom And SVC for Generic mode PSS.

Fig 3.5 :-Plot showing rotor angle and load angle w.r.t time for Statcom And SVC for NO mode PSS.

Observation Table

1:-Generic PSS mode based Statcom And SVC

2:-Multiband PSS mode based Statcom And SVC

D_theta Delta_1 Delta_2 Stability Time(s)

Statcom ^{31.04 24.66 23.36 5.6}

SVC ^{31.51 24.77 23.53 6.2}

International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved

243

Fig3.4 :-Plot showing Voltage and reactive power showing of

Statcom And SVC for Generic mode PSS

Fig 3.6:-Plot showing Voltage and reactive power showing of Statcom And SVC for NO mode PSS.

3.No PSS mode based Statcom and SVC controllers.

Conclusion:-

In this study, the power system stability enhancement via PSS and SVC, STATCOM stabilizer when applied independently and also through coordinated application was discussed and investigated. PSS_SVC, PSS_STATCOM stabilizer provides great damping characteristics and enhance significantly the system stability compared to individual design of these stabilizers.

From The above graphs and observation table we can easily conclude that statcom has a lower stability values as compared to SVC i.e it becomes stable more quickly as compared to SVC. So we can conclude that Satacom is a better facts device to be used for transient stability.

Taking all measurements at 10 s intervals.

References

[1] Hingorani and N.G.Gyungi – “Understanding Facts Devices”- IEEE Press, 2000

D_theta Delta_1 Delta_2 Stability Time(s)

Statcom ^{31.05 24.71 23.39 4.8}

SVC ^{31.47 24.81 23.57 5.4}

D_theta Delta_1 Delta_2 Stability Time(s)

Statcom 907.5 -3.03 22.68 Can’t be determined

SVC ^{-33.9 5.381 27.46} Can’t be

determined

International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2015 All rights reserved

244 [2] Kundur. Prabha, “ Power system stability and control ,”, McGraw-Hill, 1994.

[3] Tran Thi Ngoat and Le Ngoc Giang, “Assessment of the Effectiveness of Two Coordinated

Systems: SVC-PSS and STATCOM-PSS for Improving Transient Stability of Power System”, August 2013 [4] M. Srinivasa Rao , L. Murali Mohan , “Transient Stability Performance Analysis of Power System Using Facts Devices ”, February 2014.

[5] K. R. Padiyar, “FACTS CONTROLLERS IN

POWER TRANSMISSION AND DISTRIBUTION”,

New age International Publishers,2007.