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 Total Downloads : 1606
 Authors : Ashok Singroly
 Paper ID : IJERTV1IS6224
 Volume & Issue : Volume 01, Issue 06 (August 2012)
 Published (First Online): 30082012
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Stabilized Power ACDCAC Converter using Different Type of Passive Filters
ISSN: 22780181
Ashok Singroly with the Electrical & Electronics Engineering Department, IES College of Technology Bhopal
Vol. 1 Issue 6, August – 2012
Abstract Passive filters are used to filter the specific harmonics from AC voltage/current waveform and to reduce the ripple contents in DC voltage/current. Different filter topologies in converter fed loads may be C, LC, LCL or a combination of these. The basic criteria to design of such filters are based on analysis of the harmonic frequencies generated by the conversion system. In this paper, design methods for AC and DC side filters in ACDCAC converters are presented to optimize the size of filter components to optimize the filter cost and system performance. The performance of the filter designed are verified by simulation in terms of voltage/current THD, ripple content in DC voltage, fundamental value of voltage/current and RMS value of output voltage/current. LCL filters given the better performance.
Keywords Passive filters, LC filter LCLfilter, L + LC filter.
I

INTRODUCTION
ncreased use of the nonlinear and time varying devices has led to distortion of voltage and current waveforms. As a consequence, recently the issue of power quality has become important. Both electric utility and end users of electric power are becoming increasingly concerned about the quality of electric power. The term power quality has been used to describe the variation of the voltage, current
and frequency on the power system beyond a limit .
Most recent problems involve electronic equipment that is very sensitive to pollution of power line. In the presence of harmonics, equipments such as computers, telephone systems, and controllers may respond incorrectly to normal inputs, not respond at all, or give false outputs. Following are the detrimental effects of harmonic injection into the utility

Excessive losses and heating in motors, capacitors and transformers connected to the system,

Insulation failure due to the overheating and over voltages,

Overloading and overheating of the neutral conductors with loss of conductor life and possible risk of fire.

Malfunctioning of sophisticated electronic equipments,

Interference with the communication network.
Restrictions on current and voltage total harmonic distortions are being maintained in many countries according to IEEE 5191992, IEC 6100032/IEC 610003
4 standards. Various standards are set to limit the harmonics generated by nonlinear loads. The 5% voltage distortion
limit was recommended below 69 kV, while the limit on current distortion is fixed in the range of 2.5% to 20%
depending upon the size of the customer and the system voltage. The available harmonic reduction techniques are based on passive components, mixing single and three phase diode rectifiers and PWM techniques such as active filters, multipulse rectifiers and PWM rectifiers.
In this paper, design methods for AC and DC side filters in ACDCAC converters are presented to optimize the size of filter components to optimize the filter cost and system performance. The performance of the filter designed are verified by simulation in terms of voltage/current THD, ripple content in DC voltage, fundamental value of voltage/current and RMS value of output voltage/current.
The effect in output current, output voltage, and supply current and ripple in dc component with different values of capacitor and inductor have been presented.


CLASSIFICATION OF PASSIVE FILTERS
A different type of passive filters is used in acdcac converter they may be classified as:

D.C. Passive Filters
Capacitive D.C. Filter Inductive D.C. Filter
Inductive & Capacitive D.C. Filter

A.C. Source Side Passive Filters
A.C. Shunt Filter
Single Tuned &High Pass Filter
A.C Series Inductive & Capacitive Filters

A.C. Inverter Side / lode side Filters
LC filter LCL filter L+LCfilter.


DESIGN CRITERIA OF PASSIVE FILTERS
(a.) Capacitive D.C. Filters
A DC choke and an electrolytic capacitor bank on the DC bus filter the voltage and the current ripples and improve the input power factor. Capacitor and choke values are derived to optimize overall filter performance [1].
The design sequence for the filter consists of the following steps:
Steps 1 – Calculate the capacitance needed to manage a certain level of ripple voltage: for a depiction of the rectifier output waveform. The peak ripple voltage (V max) is first calculated
V max = Vrms x. 2
If the maximum acceptable ripple voltage is 80 volts, then Vmin = Vmax – Vripple
A calculation is made assuming all the energy is taken
Cr=
1 (6f)2Lr
from the capacitor. The energy in a capacitor is typically defined as 1/2 x C xVmax. Based on this formula the following calculation can be made
The passive elements of series harmonic filter selected on the basis of resonating frequency Compensating capacitor is selected such that the input power factor at the
min
P load = (1/2 x Cdc x V2 max 1/2 x Cdc x V2
) /t watts
rated output reaches its maximum value
D3
D1
A capacitor load bank can be made up several ways. We have chosen to use a capacitor value of 500uf to 10000uf for 500 V.
Step 2 – Calculate the ripple factor of DC voltage from the AC Line and from load
Lr
Lr
A Cr
B
Lr
C
Cr
Ldc
D5
Cdc
R
VO L
D6
D4
D2
Ripple factor RF=Vac / Vdc
Step 3 calculate the ripple voltage .
(b.)A.C. Shunt source side Filter
Threephase harmonic filters are shunt elements that are used in power system for decreasing voltage distortion and for power factor correction. In order to achieve an acceptable distortion, several banks of filters of different types are usually connected in parallel. consists of tuned LC filters and/or high pass filters are used to suppress the harmonics. The shunt passive filters are tuned most of the time on a particular harmonic frequency to be eliminated. So that it exhibits low impedance at the tuned frequency
.
Fig 2. ACseries InductiveCapacitive Filter
(c.) A.C. Inverter Side / lode side Filter:
(i) LC filters design:
The simplest filter is the single section LC filter .The series elements an inductance and the shunt element a capacitance. In the series inductance, harmonics voltages are developed and harmonics current flow through the shunt capacitance.. The load power factor should be considered in selecting the individual values of L and C
Resonance frequency
than the source impedance, to reduce the harmonic current flowing into the source.i.e. The filtering characteristics are determined by the impedance ratio of the source and passive filter. The most commonly used A.C. shunt filters are:

Single tuned shunt LC:
D1
These are used to filter lowest order harmonics such as
3phase 440v
50 hz a.c. supply
Ldc
D3
D5
D6
Cdc
fres=
Q1 Q3
Vdc
1
2LC
Q5
L1
L1 RL
a.c.
L1 load
5th, 7
th, 11
th, 13
th, etc. Bandpass filters can be tuned at a
D2 Q4
Q6 Q2
C1 C1 C1
singe frequency (singletuned filter) or at two frequencies (doubletuned filter) as shown in Fig.(1)
D4
Fig 3 A.C. Inverter side filter
single tuned filter Lac
Cac
High
pass filter
Lac
R
Cac
Cac Cac
R R

LCLfilter design:
A topology of an LCLfilter used is seen in fig 4. The LCLfilter is currently probably the most widely used topology. The reason for the popularity of the LCL filter is that good attenuation is achieved with a relatively small component values .i.e, good power quality is achieved with a reasonable filter costs. To find the desired resonance frequency, the filter parameters must be optimized.
D1
Ldc
D4
Fig 1 single tuned & high pass Shunt LC Filter
3phase 440v
50 hz a.c. supply
D5
D6
D3
Cdc
Q1 Q3 Q5
L1 L2
RL
load
L1 L2
L1 L2
Vdc

Highpass filters:
D2 Q4
Q6 Q2
C1 C1 C1
Which are used to filter highorder harmonics and cover a wide range of frequencies. A special type of highpass filter, the Ctype highpass filter, is used to provide reactive power and avoid parallel resonances as shown in Fig (1).

ACseries InductiveCapacitive Filter:
Fig 4. A.C. Inverter Side LCL filter
By taking the resonance frequency fres to be the primary design parameter, we are able to set the resonance frequency without having to iterate it. The resonance frequency of the LCLfilter is defined as
Inductive element (Lr) of series filter is chosen so that
fres
1 .. L1
L2 ……….. ………. ………(1)
the inductive element should not be bulky capacitive element (Cr) of series filter can be selected as:
2 L1L2C
No. of harmoni c
without filter
5th
arm filter
7th
arm filter
high pass filter
5th&7t
h filter
sourc e side filter
5th
16.49
0.02
15.5
4
13.24
0.02
0.01
7th
9.78
6.51
0.01
8.61
0.01
0.01
11th
6.56
4.51
5.61
4.86
3.32
2.31
13th
5.08
3.5
4.38
2.81
2.6
1.37
Total
22.23
10.2
18.5
17.50
5.99
3.65
THD%
If the capacitor value is fixed and the antiresonance frequency is known, then the inductance L2 can be calculated as
L2 1 ..
2
1 ..
2 resC
L1………. ……….
Eq(5)
fres
1 .. 1
r ……….. ………. ………. . (2)
If the value of the inductor L2 is chosen instead, then the value of the capacitor could be calculated using Eq.(5) first, by solving C.
Method using resonance frequency as design parameter :
2 rL1C
res 1
Then by selecting the desired capacitor values, fres as a function of the inductor ratio r = L2/L1 can be obtained. The resonance frequency in Eq. (2) can be presented as 2 L C
= 1+ r and the capacitor value C=1+r/Wres 2L1 .
(iii) L+LCfilter design:
The difference between the LCLfilter and the L+LC filter is that the L+LCfilter has two resonance frequencies while the LCLfilter has only one. Actually, the LCLfilter has three resonance frequencies, but the one defined by.(2) is the essential from the practical viewpoint. The two resonance frequencies of the L+LCfilter are called the antiresonance frequency fares and the resonance frequency fres due to the nature of resonances. At the antiresonance frequency the frequency components of the line current are attenuated whereas at the resonance frequency they are amplified.
Ldc
The first step, again, is to choose the value for the capacitance. Then by assuming the parallel connected inductance L1L2 to be equal to inductance L1, the inductance L2 can be solved from Eq.(4). When L2 is solved and substituted in Eq. (5), the value for inductance L1 is obtained. When all parameters are solved, the resonance frequencies could still be inappropriate. To get the frequencies match with the frequencies specified, some iteration has to be done.
Type of filter
Capacitive filter
Inductive filter
Ldc & Cdc filter
Ripple voltage
(volt)
60
(10%)
80
(13%)
3.2
(0.5%)


COMPARATIVE EVALUATION OF PASSIVE FILTERS

D.C Filter:
Table 1 show the comparison of D.C. filter capacitive filter is used ripple free dc voltage ,inductive filter is used
3phase 440v
a.c.
Q1 Q3 Q5
D3
D1
D5
D6
D4
Vdc
L1
L1 RL
a.c.
for smooth the supply current ,Ldc& Cdc filter are used for compensating of voltage as well as current & ripple voltage is also reduce 3.2 volt. Main object of dc obtain ripple free
50 hz
supply
Cdc
D2
L1
L2
Q4 Q6 Q2
C1
load
constant DC output voltage & continuous output current.
Table 1 comparison of different type of D.C.filter
Fig 5. A.C. Inverter Side L+LC filter
The antiresonance frequency is placed on the switching frequency. When placing the resonance frequency of the L+LCfilter, a couple of things should be considered. a considerable loss of attenuation occurs when the ratio between the antiresonance fares and the resonance

A.C. Source Side Filter :
In shunt source side filter the THD of the supply current is reduced to well below 5% (22% to 3.65%) & the fundamental value of supply current will be increase further by eliminating the ac inductor and increasing dc capacitance of the rectifier, the rectifier current would increase larger,
fares
1 ..
2
1 ………. ………. ……….
L1 L2 C
frequency fres
kL+LC=ares/res is diminished.
which may result in over current to the rectifier.
Table 2 Comparing of Different Type of A.C. Source Side Filter with Specified nth Order of Harmonic
In other words, the higher the resonance frequency is
compared to the antiresonance frequency; the lower is the attenuation on the higher frequencies.
When only the L+LCfilter is considered, the resonance frequencies could be characterized as the serial and the parallel resonance of the filter. That is, the antiresonance frequency could be calculated as and the resonance frequency as

Inverter Side Ac Filter:
Filter parameters of LC, LCL and L+LCfilters using the component values fulfill the requirement for the line voltage distortion (THD < 5 %) at constant switching frequency.
Eq(3)
fres 1 ..
2
1
L2C
………. ………. ……….Eq (4)
vof o/p voltage
Types of filter
Vo output voltage(volt)
Io output current(amp)
Vo without
filter
Vof with
filter
Io withou
t filter
Iof with
filter
LC
filter
Fund. value
573.8
567.4
21.29
22.95
R.M.S.value
405.7
401.2
15.02
16.23
THD (%)
44.63
4.71
30.69
0.59
LCL
filter
Fund. value
575
565.9
21.04
22.89
R.M.S.value
406.7
400.2
14.88
16.19
THD (%)
44.63
3.63
30.21
0.45
L+LC
filter
Fund. value
575.2
565.5
22.23
22.88
R.M.S.value
406.7
400
15.72
16.18
THD (%)
44.63
4.7
25.19
0.63
500
0
500
vof o/p voltage with filter
vof o/p voltage
500
0
500
vof o/p voltage with filter
Table 3. Comparison of different types of inverter side A.C. filters
0.4 0.405 0.41 0.415 0.42 0.425 0.43 0.435
Time (s)
Fundamental (50Hz) = 565.9 , THD= 3.63%
Mag (% of Fundamental)
100
80
60
40
20
0
0 10 20 30 40 50
Harmonic order
0.4 0.405 0.41 0.415 0.42 0.425 0.43 0.435
Time (s)
Fundamental (50Hz) = 565.5 , THD= 4.73%
Mag (% of Fundamental)
100
80
60
40
20
0
0 10 20 30 40 50
Harmonic order


CONCLUSION
Filter design methods presented, revealed some important issues that should be noticed while designing a filter for PWM voltage source converter. In particular, it was shown that the simulation result when an LCL filter is used for the PWM inverter has a major impact on the performance of the filter.
The performance comparison between LC,LCL ,L+LC filter in the term of component size ,shower very clearly the superior performance of the LCL filter over the other filter .
120
100 o/p volt thd before filter
o/p volt.THD(%)
LC filter
(c)With LCL filter (d) With L+LC filter
APPENDIX
Simulation Parameter Of Shunt & Series Filter. A.C. Source Side Shunt Filter.
5th arm 
L5 =1.2 mH ,C5=337 uf 
7th arm 
L7 =1.2 mH , C7=170uf 
High pass 
Lh= .26mH ,Ch= 300uf,Rh=3 
Lr ll Cr series 
Lr=1.2 mH ,Cr=35uf 
Simulation t Parameter of Inverter Side A.C .Filter
Type of filter 
Resonance frequency . fres 
Filter parameter 

L1 
L2 
C 

LC filter 
530 
2m H 
– 
45uf 
LCL filter 
1047 
2m H 
0.6mH 
50uf 
L+LC filter 
1677 
2m H 
0.6mH 
15uf 
80 LCL FILTER
L+LC FILTER
60
40
20
0
0 10 20 30 40 50 60
capicantance inuf
Fig 6.Effect of capacitor value of output voltage THD (%) For different type A.C inverter filter
Simulation result of inverter side A.C. filter:
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