ijirae:: parallel active filter modelling and control strategy for harmonic elimination

International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163 Issue 2, Volume 2 (February 2015) www.ijirae.com

_________________________________________________________________________________________________ 2015, IJIRAE- All Rights Reserved Page -170

Parallel Active Filter Modelling and control strategy for harmonic elimination

Hamza Nawar Abdulateef Alobidi * Marouani Ismail Electrical department, College Of Technology. Electrical department, College Of Technology. Jeddah. KINDGOM OF SAUDI ARABIA Jeddah. KINDGOM OF SAUDI ARABIA AbstractIn an electrical network, unbalanced and harmonic currents generated by nonlinear and unbalanced loads can cause harmonics and unbalanced voltage. These voltage perturbations along with voltage sag can strongly degrade customer power quality. Nowadays, the active filters such as shunt, is studied as a flexible solution to compensate all current and voltage perturbations. Therefore, in order to improve power system quality, eliminate the harmonics and improve the power factor, we have also brought to address the different structures of the parallel active filter (PAF) with a detailed study which affects both its modeling, its size and its control strategy. The FAP is simulated on Matlab-Simulink software. A low voltage network supplying non-linear loads, is considered as an application in this paper. The simulation results show the effectiveness, robustness and good adaptability to network disruption forthis PAF. The results of simulation study presented in this paper are found quite satisfactory to eliminate harmonics components from utility current. The shunt active filter is found effective to meet IEEE 519 standard recommendations on harmonics levels.

Keywords parallel active filter , power supply, , total harmonic distorsion, reactive power , power factor ,Pulse Width Modulation.

I. INTRODUCTION

The increased severity of the harmonic pollution in power systems over the last couple of decades has lead the power electronics engineers to develop high performance solutions to power quality problems created by power electronic circuits. This technological development for power quality problems involves parallel active filters. With various successful some circuit topologies and control strategy, parallel active filters are capable of not only harmonic current compensation, but also negative sequence current, reactive power, and neutral wire current (zero sequence current) compensation[1]. Parallel Active filters are also utilized to suppress voltage harmonics and voltage flickering, regulate load terminal voltages, balance voltages in a power system, and damp resonances. The active filters can be parallel (shunt) type, series type, and combination of both depending on the type of nonlinear loads and the required functionality [2], [3].

The Parallel Active Filter (PAF), shown in Figure 1[4], is the earliest and most recognized active filter configuration in the technical literature and it has been utilized in practical applications. Due to the parallel connection to the load, it is also termed as parallel filter. Parallel active filter is controlled as a current source and it is utilized to inject a compensating current into the system (to the load), so that its current cancels the harmonic current, the reactive power current and the unbalanced current components on the AC side of a nonlinear load. When it is employed to three-phase four-wire systems, The Parallel Active Filter also has the capability of compensating the neutral current (zero sequence current) component.

Fig 1. PAF implemented as a harmonic compensating current source.



Therefore, with the application of Parallel Active Filter, the current drawn form utility grid becomes harmonic free,

balanced, and in phase with utility voltage, and zero-sequence free in three-phase four-wire systems. The nonlinear load in the Parallel Active Filter application shown in Figure 1 is presented as a general purpose thyristor rectifier with DC link inductor for illustration. In fact, PAF is suitable and generally employed for diode/thyristor rectifiers with AC and/or DC side inductors. Such rectifier loads generally constitute the front-end circuits of systems such as ASDs and UPSs, which behave as harmonic current generator/source nonlinear loads (inductive loads) [5], [6]. PAF also has the capacity of damping harmonic resonance between an existing passive filter and the supply impedance[7]. The parallel active filtering technology is well matured and the Parallel Active Filter performance attributes are attractive such that many leading power electronic companies manufacture Parallel Active Filters. ABB [8], manufacture PAFs complying with the harmonic standards of IEEE 519 and EN61000-3-4 for the industrial and domestic applications.

II. PARALLEL ACTIVE FILTER A. Parallel active filter connection

The active filter can be connected in parallel or in series with the network, we are interested in what follows the

parallel active filter (shunt). In the general case, the current absorbed by the load has an active component ( Lai ), a reactive component ( Lri ), and a harmonic component ( Lhi ) as:

L La Lr Lhi i i i (1) With : s Lai i .

The Parallel active filter provides reactive and distorting power:

f Lr Lhi i i (2) To define the harmonic content of a waveform (or distortion level of a waveform), the term Total Harmonic

Distortion (THD) is used and can be applied to either voltage or current. The THD of current is defined as:

THDi= (3)

where the Ih is the rms value of the current harmonic components and I1 is the rms value of the fundamental current component.

The phasor diagram illustrated by the Figure 2 shown the Distorting power D and the power factor PF, that are respectively given by the equation x and y:

(4)

(5)

Fig 2. Phasor diagram of powers

B. three-phase voltage inverter An inverter is a converter for supplying an AC load from a DC source. If the source is a continuous voltage source

inverter is called voltage inverter. Fig 3. illustrate the topology of a three-phase voltage inverter.



Fig 3.Three-phase voltage inverter The commutation of the power switches (IGBT:S1,S2, S3) is reflected by the following equations:

dc

Mc

Mc

Mc

VSSS

VVV

.

3

2

1

3

2

1

(6)

(7)

III. INSTANTANEOUS REACTIVE POWER THEORY

To generate the Harmonic Current Reference, the harmonic current extraction methods utilized in the PAF application

is the Instantaneous Reactive Power Theory. Instantaneous reactive power theory (IRPT) known as Akagi-Nabae Theory defines the instantaneous real power and instantaneous reactive power in a 3-phase 3-wire system where no zero-sequence voltage is included. IRPT is utilized to derive the fundamental and harmonic components of load current via measured line voltages and currents.

This method exploits the transformation ( , ) to get the real and imaginary powers. Denote by ( sVsV , ) and

orthogonal components of the landmark ()( , ss II ) associated respectively with voltages (Vs123) for connecting the

parallel active filter and current absorbed by the pollutant loads. The transformation ( , ) can be write the following relationship of voltage and current:

1 11 11

2 2 232 2 23 3 303 32 2

V Vs sVs V VT s sVs V Vs s

(8)

Z Z

ic1 ic2 ic3

M

Vc3

VcVc1

i

ik1 ik2 ik3

ik2

ik3

k1 k2 k3

k2 k3

Vd

k1

N

1 2

3

ik1

Load

Z

dc

c

c

c

VSSS

VVV

.211121112

3/1

3

2

1

3

2

1



1 1

2 2

33

1 112 2 2

32 3 3 302 2

L L

L L

LL

i iI si iTIs ii

( 9)

Where (iL1 , iL2, iL3 ) are the current load and T32 is the transformation 3 phase-2 phase [9]. The instantaneous active power P and imaginary Q are defined by the following relationships

Fig 4. Transformation Model (T32 :3phase to 2 phase) Current voltage for parallel active filter.

1 2 31 2 3s s sL L LV V Vi i iP (10)

2 33 2 11

1 2 3 13 S SL L LV V V V V VQ i i is s s s

(11)

In the landmark ( , ) we can build the following matrix equation:

32

V IV sP ssIQ V sV ss

(12)

The active power P and reactive power Q respectively consist of active and reactive fundamental component p , q of most these powers respectively include an active harmonic component p

~ and a reactive harmonic component q

~:

qqQppP~~

(13)

The current harmonics are calculated in the landmark ( , ) by the following matrix:



(14)

22 SS VV (15)

We can separate the current in the ( , ) we get:

03 1 3 1 3 1

2 2 20s S S S S S S

s S S S S s S

I V V V V V V ppI V V V V V V qq

(16)

The transition to the phase marker is carried out by the following matrix:

1

2

3

1 0

2 1 33 2 2

1 32 2

re fre f

re fr e f

re f

ii

ii

i

(17)

With iref and iref perturbation currents calculated in the () from reactive currents and harmonic currents of the relation (14)

IV. SIMULATION RESULTS

The active power filter was implemented with matlab simulink . the supply grid line-to-neutral voltage VS was 230 V (RMS) and the filter capacitor voltage VC was controlled to 980v V, tested on a non linear load model. the inverter output filter Lf= 2mH and CF = 10 F. the pulse width modulation technique (PWM) used with switching frequency fd = 12 KHz and coefficient setting rmax = 0.8.

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-6

-4

-2

0

2

4

6

Time (s)

Load

cur

rent

(iL1

, iL2

, iL3

) [A

]

Fig 5. Non linear Load current

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-40

-30

-20

-10

0

10

20

30

40

50

Time (s)

Sou

rce

curre

nt (i

s1, i

s2, i

s3) [

A]

is1is2is3

Fig 6. Source current

3 12

S Sh

h s s

V pVqV V

ii



0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-40

-30

-20

-10

0

10

20

30

40

Times (s)

Filte

r cur

rent

(iF1

,iF2,

iF3)

[A]

iF1iF2iF3

Fig 7. Current generated by the parallel active filter

Fig 8, Fig 9 and Fig 10 chown that the parallel active filter with inverter three phase gave results within acceptable limits standards the harmonic distortion that does not exceed 5% and reactive power is almost nil after compensation, three network current are sinusoidal and balanced.the power factor is improved .

0 2 4 6 8 10 12 14 16 180

1

2

3

4

5

Order of Harmonic

Mag

nitu

de h

arm

onic

Peak Magnitude Spectrum of load current

Fig 8. Peak magnitude spectrum of the load current with Total harmonic distortion THDi=16.42%

0 2 4 6 8 10 12 14 16 180

1

2

3

4

5

Order of Harmonic

Mag

nitu

de h

arm

onic

Peak Magnitude Spectrum of source current

Fig 9. Peak magnitude spectrum of the source current with Total harmonic distortion THDi=1.38%



0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2-400

-300

-200

-100

0

100

200

300

400

Time (s)

is1(

A),v

s1 (V

)

vs1is1

Fig 10. Current and source voltage

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-400

-200

0

200

400

600

800

1000

1200

Time (s)

DC

bus

vol

tage

Fig 11. Voltage across capacitor

The fig 11 shows the robustness of the control loop of the regulation system included in this parallel active filter.

V. CONCLUSIONS In this paper, the connection of a parallel active filter, its modeling and its control strategy and the harmonic

identification portion are well developed. the characteristics of the harmonics producing nonlinear loads and the application consideration of the PAF to these loads are analyzed . Actually, Parallel active filters are presented as a modern solution; they provide the answer to all the disadvantages of passive filters and have the advantage of being in combination with other active filter and / or hybrid passive again with a more efficient manner. The different simulation results also show that the parallel active filter is able to decrease the harmonic levels within acceptable limits for a non-linear load and therefore improving the power factor and compensation of reactive power which allows clean up the grid by improving the quality of electrical energy which is always requested.

REFERENCES

[1] Amol S.Fegade and Prabodh Khampariya, Compensation of Harmonics Power by using Shunt Active Filter, nternational Journal of Innovative Research in Advanced Engineering (IJIRAE) Volume 1 Issue 9 (October 2014) p:30-36.

[2] H. Akagi, Active harmonic filters, Proceedings of the IEEE, Vol. 93, Issue 12, pp 2128 2141, December 2005. [3] B. Singh, K. Al-Haddad, A. Chandra, A review of active filters for power quality improvement, IEEE

Transactions on Industrial Electronics, vol.46, No. 5, pp. 960-971, October 1999. [4] HASAN. ZKAYA.Prallel active filter design, control and implementation.Thsis.June-2007. [5] F. Z. Peng, Application issues of active power filters, IEEE Industrial Application Magazine, pp. 21-30,

September/October 2001. [6] S. Bhattacharya, High power active filter systems, Ph. D. Dissertation, University of Wisconsin-Madison, 2003. [7] H. Fujita, H. Akagi, The unified power quality conditioner: The integration of series- and shunt-active filters, IEEE Transactions on Industrial Electronics, Vol. 13, No. 2, pp. 315-322, March 1998. [8] David Nedeljkovi, Mitja Nemec, Vanja Ambroi. Application of Direct Current Control in a Three-phase Parallel Active Power Filter. Elektrotehniki vestnik 76(3):85-91, 2009. [9] Mansour.S,Etude dun filtre shunt en rgime dsiquilibr-ESST-Janvier 2008.