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010 Inteatinal Cnference n Advances Ener Enineerin

Prformnc mprovmnt of Hrmonic Dtction using SynchronousRfrnc Frm Mthod

KL khool of Electrical Engineering, Surnaree Universi of Technolo (SUT)

Nakhon Ratchasima, ThailandE-mail: ngpol@sut.ac.th

Ab

This paper presents the peormance improvementof harmonic detection using a synchronous reference

frame method (SR). This method is used with shuntactive power lter to eliminate the harmonic in threephase power system. The cuto frequency tuning oflow pass and high pass lters is included in theprocess of SR method. The shunt active power ltermodel can be represented by the ideal current source.This model is used for testing the peormance ofharmonic elimination. In this paper, the three-phasediode recter behaves as the nonlinear load to

generate the harmonic of the system. The simulation

results and discussion are described in this paper.

I

Nowadays, nonlinear loads are widely used inindustries. These loads mainly generate the harmonicinto the power system. These harmonics cause a lot ofdisadvantages such as the erroneous measurement ofelectric meters [1]-[], protective device failures [3],loss in transmission lines and electric devices, andshor-life electronic equipments [4]. Therefore, it isseriously to mitigate or eliminate the harmonic in thesystem. The one of harmonic elimination methods is

the shunt active power lter (SF) as shown in Figure1. The SF provides hiher eciency and moreexible compared with a shunt passive power lter(SF). Moreover, the use of SF can avoid theresonance condition in the system. In Figure 1, thethree-phase bridge rectier with the resistive load(1 behaves as a nonlinear load in the powersystem. The synchronous reference ame (SRF)method [5] is used for a harmonic detection to calculate

the reference currents i; v , for the SAPF. Theideal current source is used to represent the SAPF to

978-1-444-7830-9/10/$6.00 010 IEEE

perfectly inject the compensating currents

i , iv , i into the power system. The compensatingcurrents are equal to the reference currents because ofusing the ideal current source model for SAPF. Themain objective in this paper is the performanceimprovement of the S method to perfectly detect theharmonic in the system. The cuto equency tuning of

the lter in the SRF harmonic detection process is themain approach to improve the performance. Theperformance index of this approach is %T aercompensated.

The paper is structured as follows. The review ofthe S harmonic detection method is addressed insection . The performance improvement of the SRF

method and the simulation results are lly presented insection 3 and section 4, respectively. Finally, section 5is the conclusion of this paper.

L,

s8V Hz

.

w

;*v ynnfn mmtAPF

n tn

nln ld

f kOtf

g The power system with a three-phase dioderectifier representing a nonlinear load

vw m m

The harmonic detection using the synchronousreference ame (SRF) method is used to calculate the

reference currents i; i , for the SPF. Theprocedure of SRF calculation is showed in Figure .

ICAEE 010

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The Figure . shows that there are four steps tocalculate the reference currents for SRF method. Therst step, three phases harmonic currents

(iLu , iLv' iLw) are transformed to the space vectorcurrents on the aO ame by using equation in block

number 1. Aer that in the second step, only thecurrents on a and axes are transformed to thesynchronously rotating dq ame (id , iq)by usingequation in block number where is thendamental equency of the system. The current

vectors on dq ame are rotated with angular speed.The i d and iq om the second step are separated intotwo parts as shown in equation (1) and (),respectively.

u v w

%=H iL" 2 2 L Lw

['dJ = COSc (

Sncf ]COS P

=COS(I) -Sin()[J l COS(V) Iq

2

3

.'(

. * [' ]

. =3 - Phi

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The circuit and transfer function of HPF

The ype of HPF

First order

Scond ordr

Third order

Circuit and Transfer function

-

1

N

(s)=(1

+

.)-

I

1 .+Re

:' , .

.

3 s' ;

s

7c

R

C

'

c c C

I

H(S)=('+i)

I

l.r+ _(R \C s RC I

There are three pes of F The rst, second, andthird order F circuits and transfer nctions are

shown in Table 1 The cuto equency (Ie) of these

lters are tuned om 1 Hto 100 Hz and the Ievaluecan be calculated by:

Ie1

2;RC(4)

The Ie tuning in the S procedure is used for testingby simulation The system for simulation is shown inFigure 1 The simulation results of the system in Figure

1 with the tuning Ie of F are depicted in Figure 4.

From Figure 4, the second order F with Ie equal to3 Hz can provide the minimum %T (06663%) Imeans that this cuto equency value obtains the bestperformance for F Similarly, there are three typesof LPF The rst, second, and third order LPF circuitsand transfer nctions are depicted in Table 2.

The cuto equency tuning value and the equationfor calculated this value is the same as the case of FThe simulation results of the system in Figure 1 usingLPF are shown in Figure 5 It can be seen that the thirdorder LPF with 56 H cuto equency can provide the

best performance (%T = 01630%)

25

oI 15 .666%:

--- 3,d

r 0 c eque ()g The performance improvement results

using HPF

3'dre

r 0 1c qu )g The performance improvement results

using LPF

2 The circuit and transfer function of LPF

hete

ofLPF

First order

Second order

Third order

Crct ad aser cton

,

.

.

r

' .

. ' r

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4 ml l

The simulation results of the system in Figure 1.

using the second order F with xed the cutoequency value to 3 Hz is shown in Figure 6. TheFigure 7. shows the simulation results of the systemusing the third order LPF with the cuto equencyequal to 56 H From Figure 6. and Figure 7, thecompensating current om SAF (icu) injects into thesystem at t=0.04 s. Aer that the source currents are

nearly sinusoidal waveform. The %T of thesecurrents are equal to 0.6663% (using F) and0.1630% (using LPF), while %T beforecompensation is 24.8%. These results are shown inTable 3.

%THD of the source currents before andaer compensation

%D of the source currents

phase%T aer compensation

%THDbefore HPF LPFcompensation

u 24.8

v 24.8

w 24.8

%D 24.8

v,:

(2d orer,f=3Hz

0.6674

0.6616

0.6699

0.6663

(3d orer,f=56 )

0.1453

0.1746

0.1676

0.1630

5

00

.

o

2

-

o

.

o

O

o

:

:

.

1

2

5

L"[ V

U

0

.

5

O

-

.

= O

.

=

O

0

6:

0

:

-'0

.

0

.

1

2