Institute of Power Electronics 1 Comparison of Series Hybrid Active Power Filters in Medium Power...

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Comparison of Series Hybrid Active Power Filters in Medium Power Application 14.6.2004Institute of Power Electronics

Comparison of Series Hybrid Active Power Filter Control Systems in Medium Power Application

Juha Turunen, Mika Salo, Heikki Tuusa

Tampere University of Technology

Institute of Power Electronics

Tampere, Finland

Presented by Juha Turunen

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Introduction

• Current harmonics are the most common problem in the supply network

• Current harmonics can be reduced by active filter…• Parallel connected active filter, Series connected active filter

• …or by passive filter…• LC-shunt circuit, High-pass filter, etc.

• …or by hybrid filter• Combination of active and passive filters

• Active and passive filters have drawbacks• The purpose of the hybrid filters is to overcome these problems that are

characteristic of the individual filter type

• This presentation compares three series hybrid active power filters (SHAPFs)

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SHAPF Topology IMain Circuit

Ls

Cc

Lc

Cdc

C5

L5

C7

L7

Active Power Filter

Supply

Ll

Load

Cl Rl

Figure 1: SHAPF topology I

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SHAPF Topology IControl System

iks,d

iks,q

Pe2udc

udc,ref

uka,d,ref

uka,q,ref

+-

0.006231

z-0.9938

+Ra

0.006231

z-0.9938

+

++

-

-

Ra

Figure 2: Control system

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SHAPF Topology IIMain Circuit

Ls

Supply

Ll

Cl

Load

Rl

C7

L7L5

C5

Active Power Filter

Cdc

Cc

Lc

Figure 3: SHAPF topology II

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SHAPF Topology IIControl System

iks,d

iks,q

Pe2udc

udc,ref

uka,d,ref

uka,q,ref

+-

0.006231

z-0.9938

+-Ra

0.006231

z-0.9938

++

+-

-

-Ra


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SHAPF Topology IIIMain Circuit

Lc

Cdc

Active Power Filter

Supply

Lf

Cf

Ll

Load

Cl Rl

Ls

Cc

Figure 5: SHAPF topology III

aff

r2

1

LLCf

(1)

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SHAPF Topology IIIControl System

Resistance control

Σ

scsb,sa,i

dcU

1

Inductancecontrol

fcfb,fa,i

h*

aBaA,uModulator

SW+

+

res*aBaA,u

ind*aBaA,u

fcfb,fa,i Σ

1h

*B1aA,1a hhu

abc dq LPF

d1f hi

Kh1 dq AB

1h

ind*aBaA,u

LPF

d2f hi

dq AB

2h

q1f hi

q2f hi *B2aA,2a hhuKh2

+

+

fcfb,fa,i

2h

abc dq


a) Whole system

b) Inductance control block

h

h

hh i

dt

idLu f

faa j (2)

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Simulations

• The comparison of presented SHAPF topologies was done using computer simulations with Matlab program

• The comparison was made in current filtering capability while minimising power rating of active filter bridge

• Harmonics producing load was 213 kVA 3-phase voltage source diode rectifier

• The aim in simulations was to maintain supply current THD below 6% while minimising active filter current

Figure 7: A-phase load current

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Simulation Results (1/2)

Figure 8: A-phase supply current

a) Topology I

b) Topology II

c) Topology III

Table I: Supply current harmonics

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Simulation Results (2/2)

• 6% supply current THD could be achieved with two presented topologies by using different coupling transformer transformation ratio

• Topology I: transformation ratio 2:1• Topology II: 6% current THD could not be achieved• Topology III: transformation ratio 4:1

• The reason for worse filtering result using SHAPF topology II was dc-link voltage control, also resistances and stray-inductances of the transformer had their influence

• SHAPF Topology III was the most effective filter• Active filter current was smallest in SHAPF topology III

• Active filter power rating in topology I 63.6% of the load• Active filter power rating in topology III 23.6% of the load

• Control system of SHAPF topology III is rather complicated• Implementation of the control system will be time-consuming

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Conclusions

• Three different SHAPF topologies were presented • These three SHAPF topologies were compared using computer

simulations • The comparison was made in current filtering capability while

minimising power rating of active filter bridge • Topology III was found to be most effective with smallest active filter

current

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