[IEEE 2010 5th International Conference on Industrial and Information Systems (ICIIS) - Mangalore,...

Abstract STATCOM with active power (energy) source

provides an effective impact on transmission system. Although both the traditional STATCOM output voltage magnitude and phase angle can be controlled, they cannot be independently adjusted in steady state since the STATCOM has no significant active power capability. In this paper a study is carried out to compare the performance of STATCOM and Battery Energy Storage System (BESS) to show the effectiveness of BESS controller. A controller is designed which is serving the purpose of voltage control and damping of power oscillations. The results are verified in MATLAB on a 10 bus benchmark system.

Index Terms BESS, Dynamic stability of Power system,

Power System Damping, STATCOM, Control Techniques.

I. INTRODUCTION VER the last two decades, advancements in static reactive compensator (STATCOM) technology based

on voltage source converter (VSC) concepts have produced significant benefits [1]-[3]. STATCOM systems offer rapid response to system events, improves voltage and power system stabilization, enhances reliability, control real and reactive power flow and increases power transfer limits. Although the STATCOM improves the performance of power system efficiently but the introduction of energy storage system with STATCOM as shown in Fig.1, increases the flexibility of the control to such an extent that it can control different aspects of the system at the same time. The traditional STATCOM (with no energy storage) has only two possible steady-state operating modes: inductive (lagging) and capacitive (leading). A traditional power system can be seen as the interconnection of generating sources and customer loads through a network of transmission lines, transformers, and ancillary equipment. Based on their structure, power system can be broadly classified into meshed and longitudinal systems. Independent of the structure of the power system, power flows throughout the network is largely distributed as a function of transmission line impedance; a transmission line with low impedance enables larger power flows through it than does a transmission line with high

impedance. However transmission systems do not behave in an ideal manner. The systems react dynamically to changes in active and reactive power, influencing the magnitude and profile of the power systems voltage. Quite often it gives rise to a myriad of operational problems and the system operator has to intervene to achieve power flow redistribution, but with limited success. The new technology known as FACTS [4] opens up new opportunities for controlling and enhancing the usable capacity of present, as well as new and upgraded lines. The opportunities arise through the ability of FACTS controllers to control the interrelated parameters that govern the operation of transmission systems including series impendence, shunt impendence, voltage, phase angle and the damping of power system oscillations. These constraints cannot be overcome while maintaining the required system reliability by mechanical means without lowering the usable transmission capacity. By providing FACTS controllers, a line can be made to carry power closer to its thermal rating. Thus the FACTS devices in a power system can potentially overcome limitations of mechanically controlled transmission systems. By facilitating bulk power transfer, these FACTS devices help in minimizing the need to build more transmission lines and power plants. The ability of the transmission system to transmit power becomes impaired by one or more of the following steady-state and dynamic-state limitations: (i)Voltage profile Control: Maintaining desired transmission voltage profile, Prevention of voltage collapse, Limitation of over-voltages. (ii)Power transmission control: Increased power transmission, minimization of loop flows, Voltage and frequency control. (iii)Stabilization of system dynamics: Transient, dynamic and steady-state stability. In fact, the limitations on power transfer can always be relieved by the addition of the new transmission and generation facilities. Alternatively, FACTS controllers [5] can enable the same objectives to be met with no major alterations to the system layout. The main concentration of the research work presented in this paper is to show the advantages of interfacing battery with STATCOM and this combination is hereafter called Battery Energy Storage System (BESS), in addition modeling of STATCOM, BESS, and design of controllers for improving and controlling the voltage profile of the system and damping

Application of Battery Energy Storage System (BESS) in Voltage Control and Damping of

Power Oscillations Bhim Singh, Fellow, IEEE and Zakir Hussain

O

978-1-4244-6653-5/10/$26.00 2010 IEEE

2010 5th International Conference on Industrial and Information Systems, ICIIS 2010, Jul 29 - Aug 01, 2010, India

514

of oscillations to improve the stability is also studied in brief. Shunt compensation has the ability to automatically support the voltage level in a specific area of the power system.

. Fig.1 Functional representation of BESS The voltage level is an immediate image of the reactive power balance too high a voltage means a surplus of reactive power and vice versa. A dynamic shunt compensator automatically and instantaneously adjusts the reactive power output smoothly as desired and thus improving the system stability.

II. MODELING OF 10 BUS BENCHMARK TEST SYSTEM The network under consideration is a 10 bus benchmark

two area system as shown in Fig 2. This benchmark system is taken from[6]. Area1 supplies the power to Area2 (load side) across transmission system of five parallel transmission lines. Area1 consists of two generating units one of them acting as slack generator having very large inertia. Area2 consists of one generating unit and two load buses. The STATCOM and BESS are connected at bus6 connecting Area1 and Area2. The electrical characteristics of all the three generators are similar. The generators are coal fired thermal generators. Generator1 is of 5000MVA capacity representing equivalent for a large remote system. Gen2 and Gen3 are having inertia constant H as 2.32 MW-s/MVA. The data for all the generators is taken from [7]. This benchmark system has been developed in MATLAB SIMULINK environment.

Fig.2 10 Bus test system

III. CONTROL ALGORITHM Fig.3 shows the equivalent circuit of STATCOM, which

is connected to power system [8] by a transformer. av , bv and cv represent the three phase line-to-neutral system

voltages at the connection point. ae , be and ce represent the fundamental components of the three phase line-to-neutral output voltage of the STATCOM's converter. L and R represent the resistance and reactance of the transformer. Rp accounts for losses in converter devices.

, ,a b ci i i represents line currents and C is equivalent capacitance on DC side of the converter.

Fig.3 Equivalent circuit of STATCOM

The main objective of the controller is to meet the desired performance of the system as per the preset requirement. A decoupled control scheme [9] is considered here. From Fig.3 KVL equations after rearrangement can be written as follows

0 0

1 0 0

0 0

RL

i i V ea a a aR

i i V eb b b bLLV ei i c cc cR

L

p

= +

(1)

where /p d dt= A per-unit system has been adopted according to the definitions:

' bbase

w LZL = ;

' 1b basew Cz

C = ; 'base

RZR = ; ' pbase

Rp ZR = ;

' xbase

ix ii = ; ' xbase

vx vv = ;

' xbase

ex ee = ; basebase

vx iz =

Thus in pu system the above equations can be written as

' 0 0'

' ' ' ''' 0 0 ' ' ' ''

' '' '' 0 0 -

R wbL

i i V ea a a awR w bbp i i V eb b b bLL V ei i c cc cR wb

L

= +

(2)

Converting abc to dq quantities using Parks transformation eqn. (4) one may have

'' '' ''

'' ' ' ''

'

R wb w V ei i w d dd dL bpLi i V eR wq qb q qw

L

= +

(3)

where /w d dt=


515

Transformation matrix is as

[ ]

12

0 02 1( 120 ) ( 120 ) 3 20 0 1( 240 ) ( 240 )

2

Cos Sin

C Cos Sin

Cos Sin

=

(4)

Equation (3) may be written in the following form:

'' ' '' 0 1 + ' ' '' 0 2

'

R wb wi i i xwd d dLp

xwi i iR wq q qbwL

= +

(5)

where ' '1 ( )bw

dLx v e= (6)

''

2 ( )bw

qLx e= (7)

Assuming d-axis coincides with the voltage vector, 'qv becomes zero. Neglecting the voltage harmonics produced by the inverter, one can write the pair of equation for 'de and 'qe

' cosd dce kv = (8)

' sinq dce kv = (9)

where k is a factor for the Voltage Source Converter(VSC) which relates the DC-side voltage to the amplitude (peak) of the phaseto-neutral voltage at the VSC AC-side terminals, and is the angle by which the VSC voltage leads the line voltage vector. Fig.4 shows the vector diagram of phase and dq voltages. In d-q frame of reference the dynamic Battery Energy Storage System (BESS) can be modeled as given below [3].

' w 0' ws'w 0'ws

' '1 0 0 ( )' ' '

R

Li id dd Ri w iq qsdt LV Vdc dc

R Rb dcC R Rb dc

= +

coscos( )' '

sinsin( ) ' '

cos( ) sin( )' ' ' '

V Vdc skL LV Vdc sw k ws sL L

i i Vdc dc bk kC C R Cb

+ + + + +

(10)

where

di & qi are the injected per unit dq STATCOM currents

dcV is the per unit voltage across 'C

'R and 'L represent the transformer STATCOM losses k and are PWM modulation gain and angle respectively

bV is the per unit battery voltage 'bR represents battery losses 'dcR represents switching losses

sV per unit system side voltage angle of system side voltage Under steady state conditions the first two equations from above matrix can be written in linearized form as

' 0 ' 1 0 ' 2

0 '

Ri i xd dLp wi i xq qR

L

= +

(11)

where

0 00 0' '1

2 0 0 0'

k Vdcw i V kq dcx L Lx V kdc w idL

+ + =

(12)

where [ ]1 2 Tx x is the control variable vector. In the BESS system, the dc voltage is held nearly constant by the battery, therefore the incremental change dcV is negligible. Fig.5 shows the block diagram of decoupled controller. The decoupled proportional-integral (PI) type of controller is considered, KP1, KI1, KP2 and KI2 are the proportional and integral gain settings of DC and AC voltage regulators respectively.

Fig. 4 STATCOM vector in synchronous frame of reference

d-axis

q-axis

v

e| | dce kv=

| |dv v=

i

de

qe

qi

di

a-axis

b-axis

Vc


516

Fig.5 Block diagram of Decoupled controller

IV. SIMULATION RESULTS The effectiveness of controller has been verified on 10

bus benchmark system discussed in section-II. A model of the benchmark system along with STATCOM and BESS with the controller has been developed in MATLAB/SIMULINK.

A. Voltage Control One of the five transmission lines connecting bus5 and bus6 is taken out at t=5 sec. With the result of this contingency there is overall system voltage drop accompanied by oscillations. As all the generators are provided with Power System Stabilizer (PSS) and excitation system the voltage of the system settles down at some other lower steady state value in uncontrolled case. Fig.6 shows the dynamic response following the contingency at bus6. As there is overall system voltage drop and the load provided in area2 is voltage and frequency dependent the power flow from area1 to area2 also goes down as shown in Fig.6.

However in controlled case when STATCOM or BESS is connected at bus6 the controller is designed in such a way that whenever there is voltage drop at bus6 STATCOM or BESS starts supplying reactive power to bring the voltage up and vice versa in over voltage case so that the preset value of voltage is achieved. Both the controlled and uncontrolled cases are compared in Fig.7 showing the voltage at bus6.

A comparison of all three cases uncontrolled, controlled with STATCOM and controlled with BESS is shown in Fig.7. It is clear that although in both the controlled cases

STATCOM and BESS, the post-outage voltage is brought back to the pre-outage voltage but the response of BESS is faster as compared to that of STATCOM. The oscillations are also effectively damped in BESS as shown in Fig.7.

4000

5000

6000

Pow

er(M

W)

1

1.05

1.1

Volta

ge(pu

)

1

1.05

1.1

Volta

ge(pu

)4.99 5 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08

1

1.05

1.1

Time(s)

Volta

ge(pu

)

Power Transmitted from area1 to area2

Voltage at bus6

Voltage at bus3

Voltage at bus5

Fig.6 Line outage at t=5sec (i)Power flow from area1 toarea2 (ii)Voltage at bus 6(iii) Voltage at bus3 (iv)Voltage at bus5

5 5.01 5.02 5.03 5.04 5.05 5.06 5.071.01

1.02

1.03

1.04

1.05

1.06

1.07

1.08

1.09

Time(s)

Volta

ge a

t bus

6(pu

)

Uncontrolled Case

WithBESS

With STATCOM

Fig .7 line outage at t=5sec.Voltage at bus6

Because of the energy source provided with STATCOM the flexibility of control increases as it can operate in all the four quadrants. Thus by providing battery energy source the BESS is more effective in damping the oscillations. The DC voltage is also compared in both the controlled cases (STATCOM and BESS) as shown in Fig.8. It is clear that DC voltage in case of BESS is almost constant which is not the case with STATCOM. During the transient period BESS is able to supply and absorb active


517

power as shown in Fig.8. This ability of active power exchange between BESS and the bus to which it is connected is expected to make it more demanding in various power system control applications.

B. Damping of Power System Oscillations Fig. 7 and Fig.8 show the results with the controller mainly designed for voltage control. As a result of voltage control the oscillations are also in turn controlled to some extent especially with BESS. The controller discussed in section-III has been modified to damp-out power system oscillations. An additional feedback signal is fed to the controller for the purpose of damping the oscillations. A change in transmitted power has been taken as the additional feedback signal. The block diagram of this modified controller is shown in Fig.9. A comparison of all the three cases (STATCOM, BESS and Uncontrolled case) is shown in Fig.10 and Fig.11 considering the same contingency i.e. line outage. It is clear from these simulation results that the modified controller is effectively damping the power oscillations especially in case of BESS. In this modified controller whenever there is any oscillation in the transmitted power the damping

4.8 4.9 5 5.1 5.2 5.3 5.4 5.5 5.6

0.98

0.99

1

1.01

1.02

DC Vo

ltage

(V)

4.8 4.9 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

Stat

Com

Re

activ

e Po

wer

Q(pu

)

4.95 5 5.05 5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45-0.5

0

0.5

Time(s)

Stat

Com

ac

tive

Pow

er P(

pu)

STATCOM BESS

STATCOM

STATCOM

BESS

BESS

Fig.8 Line outage at t=5sec (i) DC voltage (ii) Reactive power exchange (iii) Active power exchange

Fig.9 Modified Damping Controller of STATCOM

signal which is change in transmitted power has some nonzero value and is fed back to the controller to change the pulses supplied to voltage source converter (VSC). The voltage controller is always into action whenever there is any deviation in the voltage from the preset value. The results also show the comparison of STATCOM and BESS which shows that BESS is almost completely damping the oscillations with new modified controller. Because of the active power availability BESS is also able to avoid the sudden dip in voltage at the very first instant of contingency which is not the case with STATCOM. DC bus voltage is also showing that BESS is able to control DC voltage very strongly during and after the contingency, which is because of the energy source interfaced with capacitor on DC side of the converter as shown in Fig.11. The reactive power exchange comes into action when the voltage deviates from the reference value and it settles at some steady state value to compensate the voltage drop created by line outage.

4.99 5 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.081.02

1.03

1.04

1.05

1.06

1.07

1.08

1.09

1.1

Volta

ge at

Bu

s6(pu

)

Time(s)

BESS

STATCOM

Uncontrolled Case

Fig.10 Line outage at t=5sec Voltage at bus6


518

4.99 5 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08

0.6

0.8

1

1.2

DC Vo

ltage

(V)

4.8 5 5.2 5.4 5.6 5.8 6-0.8

-0.6

-0.4

-0.2

0

Stat

Com

Re

activ

e Po

wer

Q(pu

)

4.8 4.9 5 5.1 5.2 5.3 5.4 5.5 5.6-0.5

0

0.5

Time(s)

Stat

Com

ac

tive

Pow

er

P(pu

)

STATCOM

BESS

STATCOM

STATCOM

BESS

BESS

Fig.11 Line outage at t=5sec (i) DC voltage (ii) Reactive power exchange (iii) Active power exchange

V. CONCLUSION The simulation results have shown that the STATCOM

and BESS with single controller can be used to enhance the performance of the power system. The results have shown viability of STATCOM and BESS to control the voltage, damp out PS oscillations. A new modified controller has been proposed to control both voltage and damp-out power oscillations. The overall results presented have shown the effectiveness of BESS in enhancing the power system performance. It is important to mention here that the cost of FACTS devices will predominate in BESS as the energy storage device required will be of small capacity in these applications because of the obvious reasons.

REFERENCES [1] A. H. Norouzi and A. M. Sharaf, Two control schemes to enhance

the dynamic performance of the STATCOM and SSSC, IEEE Trans. on Power Dleivery., vol.20,no.1, pp. 435-442, Jan. 2005.

[2] P. G. Gonzalez and A.G. Cerrada., Control system for a PWM-based STATCOM, IEEE Trans. on Power Delivery, vol.15, no. 4, pp. 1140-1145, Oct. 2000.

[3] Z. Yang,, C. Shen, L. Zhang, M. L. Crow and S. Atcitty, Integration of a StatCom and Battery Energy Storage, IEEE Trans. on Power Systems, vol. 16, no. 2, pp. 254-260, May 2001

[4] G. Hingorani and L. Gyugyi, Understanding FACTS: Concepts and topology of Flexible transmission systems, IEEE press, New York, 2000.

[5] P. Rao, M. L. Crow and Z. Yang, STATCOM control for power system voltage control application, IEEE Trans. on Power Delivery, vol. 15, no. 4, pp. 1252-1257, Oct .2000.

[6] C. W. Taylor, Power System Voltage Stability. New York: McGraw-Hill, 1994.

[7] PM. Anderson and A.A.Fouad, Power system control and stability. The Lowa state university Press,Ames,Lowa 1977.

[8] L. Cong and Y. Wang, Co-ordinated control of generator excitation and STATCOM for rotor angle stability and voltage regulation enhancement of power systems, IEE Proc.-Gener. Transm. and Distrib. vol 149, no. 6. November 2002.

[9] C.Schauder and H. Mehta, Vector analysis and control of Advanced Static VAR Compensator, IEE proc, vol. 140, no.4, July 1993, pp 299-306.

[10] Z. M. Salameh, M. A. Casacca and W.A. Lynch, A mathematical model for lead-acid Batteries, IEEE Trans. on Energy Conversion, vol. 7, no.1, pp. 93-98, March 1992.

Bhim Singh (SM99) was born in Rahamapur, India, in 1956. He received the B.E (Electrical) degree from the University of Roorkee, Roorkee, India, in 1977 and the M.Tech and Ph.D. degree from the Indian Institute of Technology (IIT) Delhi, New Delhi, India, In 1979 and 1983, respectively. In 1983, he joined the Department of Electrical Engineering,

University of Roorkee, as a lecturer, and in 1988 became a Reader. In December 1990, he joined the Department of Electrical Engineering, IIT Delhi, as an Assistant Professor. He became an Associate Professor in 1994 and Professor in 1997. His area of interest includes power electronics, electrical machines and drives, active filters, FACTS, HVDC and power quality. Dr. Singh is Fellow, Institute of Electrical and Electronics Engineers (IEEE), a fellow of Indian National Academy of Engineering (INAE), the Institution of Engineers (India) (IE (I)), and the Institution of Electronics and Telecommunication Engineers (IETE), a life member of the Indian Society for Technical Education (ISTE), the System Society of India (SSI), and the National Institution of Quality and Reliability (NIQR) and Senior Member of Institute of Electrical and Electronics Engineers (IEEE).

Zakir Hussain received M.Tech degree in Power Systems from IIT Delhi, India in 2008 and B.E degree in Electrical Engineering from Model Institute of Engineering and Technology, Jammu, India in 2006. His areas of interest include FACTS controller and their applications in Power System, Power System Stability and Renewable Energy.


519

/ColorImageDict > /JPEG2000ColorACSImageDict > /JPEG2000ColorImageDict > /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 200 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 2.00333 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict > /GrayImageDict > /JPEG2000GrayACSImageDict > /JPEG2000GrayImageDict > /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 400 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 600 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.00167 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict > /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile (None) /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False

/CreateJDFFile false /Description > /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ > /FormElements false /GenerateStructure false /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles true /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /NA /PreserveEditing false /UntaggedCMYKHandling /UseDocumentProfile /UntaggedRGBHandling /UseDocumentProfile /UseDocumentBleed false >> ]>> setdistillerparams> setpagedevice





























































/ColorImageDict > /JPEG2000ColorACSImageDict > /JPEG2000ColorImageDict > /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 200 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 2.00333 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayI

[IEEE 2010 5th International Conference on Industrial and Information Systems (ICIIS) - Mangalore,...

Documents

Transcript of [IEEE 2010 5th International Conference on Industrial and Information Systems (ICIIS) - Mangalore,...