three phase shunt active filter with constant instantaneous power contro

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –

6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME

245

THREE PHASE SHUNT ACTIVE FILTER WITH CONSTANT

INSTANTANEOUS POWER CONTROL STRATEGY

*Mr.R.J.Motiyani

1, *

Mr.A.P.Desai2

1Department of Electrical Engineering,

S.N.Patel Intitute of Technology & Research Centre, Umrakh, Surat, India 2Department of Electrical Engineering,

S.N.Patel Intitute of Technology & Research, Centre, Umrakh, Surat, India

ABSTRACT

This paper discusses development of the matlab simulation of three-phase shunt active filter

for non-linear rectifier load with constant instantaneous power control strategy. The shunt active

filter with constant instantaneous power control strategy compensates the oscillating real and reactive

power of the nonlinear load; it guarantees that only a constant real power p (average real power of

load) is drawn from the power system. Therefore, the constant instantaneous power control strategy

provides optimal compensation from a power flow point of view even under non-sinusoidal or

unbalanced system voltages.

Keywords: Pulse Width Modulation (PWM) converter, Generalized Fryze current control strategy.

1. INTRODUCTION

The Shunt Active Filters generally consist of two distinct main Block;

The PWM converter

The active controller

The PWM converter is responsible for power processing in synthesizing the compensating

current that should be drawn from the power system. The active filter controller is responsible for

signal processing [2]. It determines the instantaneous compensating current reference in real time

which is continuously passed to the PWM converter. Fig.1 shows the basic configuration of a shunt

active filter for harmonic current compensation of a specific load.

INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &

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ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), pp. 245-254

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246

si Li

Ci

LiVL

*

Ci

Fig.1 Basic configuration of a shunt active filter

2. ACTIVE FILTER CONTROLLERS

The control algorithm implemented in the controller of the shunt filter determines the

compensation characteristics of the shunt active filter. There are many ways to design a control

algorithm for active filtering. Certainly; the p-q theory forms a very efficient basis for active filter

controllers [2].

Following are the different control strategies:

• Constant instantaneous power control

• Sinusoidal current control

• Generalized Fryze current control

3. ACTIVE FILTERS FOR CONSTANT POWER COMPENSATION

The constant power compensation control strategy for a shunt active filter was the first

development based on the p-q theory and was introduced by Akagi et al.in 1983[1].The principle of

this compensation method are described in fig.1.In terms of real and reactive power, in order to draw

a constant instantaneous power from the source, the shunt filter should be installed as close as

possible to the nonlinear load. It should compensate the oscillating real power p% of this load [3].

Hence, the shunt active filter should supply the oscillating portion of the instantaneous active current

of the load, that is,

Oscillating portion of instantaneous active current on the α axis piα % ;

( )22ppv

ivv

α

α

βα

= −+

%%

1



247

Oscillating portion of instantaneous active current on the β axis piβ % ;

( )22pp

vi

vv

β

β

βα

= −+

%%

2

The reason for adding a negative sign to the real power in the above equations is to match

them with the current directions adopted in fig.2. If the shunt active filter draws a current that

produces exactly oscillating power ( )p− % of load. The power system would supply only constant

portion of real power ( p ) of load. In order to compensate oscillating power ( p− % ), which implies an

oscillating flow of energy, the dc capacitor of the PWM converter must be made large enough to

behave as energy storage element, to avoid large voltage variations.

Following the instantaneous reactive current aqi and

qiβ on α and β axis.

Instantaneous reactive current on the α axis aqi

( )22qqv

ivv

α

α

βα

= −+

3

Instantaneous reactive current on the β axis qiβ

( )22qq

vi

vv

α

β

βα

= −+

−

4

Note that the total reactive power being compensated is q q q− = − − % . The reason for the

negative sign is the same as explain for the real oscillating power compensation. Contrarily for

compensation of oscillating power ( p− % ), compensation of the total reactive power ( q− ) does not

require any energy storage element.

If the shunt active filter compensates the oscillating real and reactive power of the load, it

guarantees that only a constant real power p (average real power of load) is drawn from the power

system. Therefore, the constant instantaneous power control strategy provides optimal compensation

from a power flow point of view, even under non-sinusoidal or unbalanced system voltages [2].

4. CONTROL BLOCK DIAGRAM

Fig.2 shows control block of constant instantaneous power strategy of three phase shunt

active filter. Three phase instantaneous voltages and currents phases of balanced or unbalanced

source in the abc-reference frame is converted into instantaneous voltages and currents on the 0αβ -

axis [7].The Clarke Transformation and its inverse transformation of three-generic voltages are given

by,



248

1 11

2 2 2

3 3 30

2 2

1 11

2 2 2

3 3 30

2 2

a

b

c

a

b

c

vv

vvv

ii

iii

α

β

α

β

− − = −

− − = −

p

q

v i v i

v i v i

α α β β

β α α β

= +

= −

a

b

c

vvv

a

b

c

iii

vv

α

β

ii

α

β

p q

lossp

q−

p

lossp p+%

refV

DCV

vv

α

β

1−

*

2 2*

1closs

c

p

q

v vi p

v vv vi

α βα

β αα ββ

− + = −+ −

%

*

*

c

c

i

i

α

β

*

*

*

ca

cb

cc

i

i

i

*

*

*

*

*

1 0

2 1 3

3 2 2

1 3

2 2

ca

c

cb

c

cc

ii

ii

i

α

β

= − − −

+ + +

−

Fig.2 Control block for the constant instantaneous power control strategy

0

1 1 1

2 2 2

2 1 11

3 2 2

3 30

2 2

a

b

c

v vv vv v

α

β

= − −

−

5



249

0

11 0

2

2 1 1 3

3 2 22

1 1 3

2 22

a

b

c

v vv vv v

α

β

= −

− −

6

Similarly,three-phase generic instaneous line currents, ai

bi and ci can be transformed on

the 0αβ axes by

0

1 1 1

2 2 2

2 1 11

3 2 2

3 30

2 2

a

b

c

i ii ii i

α

β

= − −

−

7

and its inverse transformation is

0

11 0

2

2 1 1 3

3 2 22

1 1 3

2 22

a

b

c

i ii ii i

α

β

= −

− −

8

One advantage of applying the 0αβ thransformation is to separate zero-sequence

components from the abc-phase componets.As per p-q Theory,it is defined in three-phase systems

with or without a neutral conductor.Three instantaneous powers-the instantaneous zero-sequence

power 0

p ,the instantanous real power p ,and the instantanous phase voltages and line currents on the

0αβ axies as

0 0 00 0

0

0

p

q

p v iv v i

iv v

α β α

ββ α

=

−

9

These two powers have constant values and a superposition of oscillating

compoents.Therefore,it is insteresting to separate p and q into two parts:



250

Real power: p p p= + %

Imaginary power: q q q= + %

Averege Oscillating

powers powers

A dc voltage regulator should be added to control strategying a real implementation as shown

in fig.2.In fact, a small amount of average real power(loss

p ) must be drawn contiously from the

power system to supply switching and ohmic losses in the PWM converter.Otherwise,this energy

would be supplied by dc capacitor which would dicharge contiously.The power converter of the

shunt active filter is a boot-type converter.It means that the dc voltage must be kept higher than the

peak value of the ac-bus voltage in order to guarantee the controllability of the PWM current

control.Fig.2 suggests that the real power of the nonlinear load should contiously measured and

separated into its average real power ( p ) and oscillating ( P% ) parts.This would be the fuction of the

block named “selection of the powers to be compensated” .In a real implementation,the sepation of

p and P% from p is realized through a low-pass filter. Reference currrents *

C ai , *

Cbi and *

Cci for

switching of IGBTs’PWM invetor is found from inverse Clarke Transformation.The switching

pattens of IGBT’s are found by comparing of reference currents and contionously sensed currents

from lines.

5. SIMULATION

Fig.3 Matlab simulation of shunt active filter supplying non-linear load of rectifier with constant

instantaneous power control strategy

SHUNT ACTIVE FILTER

A

B

C

+

-

rectifier

Discrete,Ts = 5e-005 s.

powerguimeasurements

v+-

Voltage Measurement1

A

B

C

a

b

c

Three-Phase Breaker

Vabc

Iabc

A

B

C

a

b

c

Three-PhaseV-I Measurement

A

B

C

A

B

C

Three-PhaseParallel RLC Branch

Subsystem2

Conn1

Conn3

Conn5

Subsystem1In1

A

C

B

GROUND

Subsystem

Scope5Scope3

Scope2

Scope1

Scope

neutral

A

B

C

SOURCE

Id

Vabc

pulses

Rectifier

Control

Ground2

Ground1

V

Goto1

I

Goto

i+ -

Current Measurement1

i+ -

Current Measurement

h



251

Fig.4 Subsystem of hysterisis block

Fig.5 Subsystem of Clarke Transformation block

6. TESTS AND RESULTS

Results of Matlab simulation shown in fig.3 of three shunt active filter supplying non-linear

load of rectifier with constant instantaneous power control strategy are shown as following figures.

Input source of this simulation is used as three phase programmable voltage source which parameters

(voltage=220 V (line to line), frequency=50Hz) with internal resistance as RCL series branch with

resistance r=0.1ohm and inductance of 0.000010H.Line between source and load as non liner load as

three phase rectifier with RL circuit is of inductance of L=0.4mH.Matab simulation has non-linear

load as three phase rectifier with RL circuit which parameters are r=20 ohm and L= 0.4mH.Fig.6

shows voltage with value of aprroximate180 volt applied to three phase rectifier from lines from

source voltages. Fig.7 shows the load current per phase of nonlinear three rectifier with RL load.

Balanced or unbalance source can supplied with three phase active filter with constant instantaneous

power control strategy to non linear load as shown Fig. 8 the constant average active power(P) and

reactive power (Q) of non linear rectifier with RL load. Fig.9 shows the load current per phase of

nonlinear three rectifiers’ circuit.Fig.10 and 11 show output voltage and current of three phase

rectifier circuit supplied to RL Load.

1

g

2

imeas

1

iref

Vabc

3

Ibeta

2

Ialpha

1

I0

-K-

Gain9

-K-

Gain8

-K-

Gain7

-K-

Gain6

-.5

Gain5

-.5

Gain4

1

Gain3

-K-

Gain2

-K-

Gain10

-K-

Gain1

-K-

Gain

1



252

Fig.6 Load 3-phase voltages or input voltages of three rectifier supplied RL Circuit

Fig. 7 Load current per phase of Non linear three rectifier with RL load

Fig. 8 Constant Active Power (P) and reactive power (Q) of Non linear three rectifier with RL load

Fig. 9 Load currents or input currents of Non linear three rectifier with RL load



253

Fig. 10 Output voltage of three phase rectifier circuit supplied to RL Load

Fig.11 Output current of three phase rectifier circuit supplied to RL Load

7. CONCLUSION

Here in, Simulation of three phase shunt active filter supplying to non linear load with

constant instantaneous power control is successfully simulated using Matlab.It has been realized that

the three phase shunt active filter with Constant instantaneous power strategy compensates the

oscillating real and reactive power of the load; it guarantees that only a constant real power p

(average real power of load) is drawn from the power system. Hence, the constant instantaneous

power control strategy provides optimal compensation from a power flow point of view even under

non-sinusoidal or unbalanced system voltages.

8. REFERENCES

1. H.Akagi,Y.Kanazawa,and A.Nabae, “Instantanous Reactive Power Compensator comprising

Switching Devices Without Energy Storage Components”, IEEE Transactions on Industrial

Applications,vol.IA-20,no-3,1984,pp.625-630.

2. S.J.Jeong and T.Endoh”Control Method for a Combined Active Filter System

Employing,”IEEE Transactions on Industrial Electronics, vol 41, no.3, 1994, pp.278-284.

3. H.Akagi,Y.Kanazawa,and A.Nabae,”Principles and Compensation Effectiveness of a

Instantaneous Reactive Power Compensator Devices, “in Meeting of the Power

Semiconductor Converters Reserchers-IEE-Japan,SPC-82-16,1982(in Japanese)

4. L.Gyugyi and E.C.Straycula,”Active ac Power Filters, “in Proceedings IEEE industrial

Applications Annual Meeting, vol.19-C, 1976, pp.529-535.

5. L.S.Czarnecki,”Power Related Phenomena in Three-Phase Unbalanced Systems,”IEEE

Trans.Power Delivery,vol.no.3, July 1985,pp.1168-1176.



254

6. M.Routimo,M,Salo,and H.Tuusa,”comparision of voltage and current source shunt active

power filters,”in conference records IEEE-PESC 2005,pp-2571-2577.

7. H.Akagi,”Trends in Active Power Filters,” in EPE’95-European Conference Power

Electronics Appl.,vol.0,Sevilla,Spain,sep.1995,pp.0.017-0.026.

8. N.G.Hingorani,”Power Electronics in Electric Utilities: Role of Power Electronics in Future

Power Systems,”Proceddings of IEEE,vol.76,no.4,April,1988

9. N.G.Hingorani,”High Power Electronics and Flexible AC Transmission System,” IEEE Power

Engineering Reviews,July 1988.

10. Dr. Leena G, Bharti Thakur, Vinod Kumar and Aasha Chauhan, “Fuzzy Controller Based

Current Harmonics Suppression using Shunt Active Filter with PWM Technique”,

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11. o. ucak, i. kocabas, a. terciyanli, design and implementation of a shunt active power filter with

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BIOGRAPHIES

R. J. Motiyani has received the M.E degree in Electrical Power

Engineering from M. S. University, Baroda, and Gujarat in 2005. Currently

he is working with S.N.Patel Institute of Technology & Research Centre as

Associate Professor in Electrical Engineering Department.

A.P. Desai has received the B.E degree in Electrical Engineering from

VNSGU, Surat; Gujarat in 2008.He has received M.E.degree in M.E.

(electrical engineering) from Shantilal shah Engineering college, Bhavnagar

in 2013. Currently he is working with S.N.Patel Institute of Technology &

Research Centre as Assistant Professor in Electrical Engineering

Department.