ISSN(Online) : 2319-8753 ISSN (Print) : 2347-6710
International Journal of Innovative Research in Science, Engineering and Technology (An ISO 3297: 2007 Certified Organization)
Vol. 5, Issue 3, March 2016
Analysis of 3-Phase AC-DC Thyristor Controlled Converter Fed to DC Motor Jyotsana Singh1, Hitesh Lade2 P.G. Student, Department of Electrical Engineering, Satyam Education & Social Welfare Society Group of Institutions, Bhopal, India1 Assistant Professor, Department of Electrical Engineering, Satyam Education & Social Welfare Society Group of Institutions, Bhopal, India2 ABSTRACT: This paper presents the discussion of multi-pulse improved power quality ac-dc converter configuration, comparative factors and selection of specific. Reliable low distortion DC supply is a prime concern for medium and high voltage applications. Multilpulse converters is one of the popular device that furnishes low ripple DC output with the benefit of direct conversion from AC supply. The three-phase multi-pulse AC to DC conversion system have a phase-shifting transformer and a three-phase source. Every such type of converter provides a 6-pulse AC to DC conversion system, that’s why in order to produce more sets of 6-pulse systems, a uniform phase-shift is required and hence with proper phase-shifting angle, 12, 18, 24, 30, 36 and higher pulse systems have been produced. This paper describes the comparative analysis and design of even group combinations namely 6, 12 and 24 pulse converters with MATLAB simulations. The performance improvement of multi-pulse converter is achieved for total harmonics distortion (THD) in supply current, DC voltage ripples and form factor. The Input A.C current waveform and the DC output waveform and harmonic analysis has been observed. KEYWORDS: Total Harmonic Distortion (THD), Three phase AC-DC Converter, Ripple Factor, Power Factor, Thyristor Bridge. I.
INTRODUCTION
A power electronic device creates harmonic distortion and cause voltage dip if not protected. Three-phase ac–dc conversion of electric power is widely employed in HVDC system, adjustable-speed drives, uninterruptible power supply and utility interfaces with non conventional energy sources such as solar photovoltaic systems (PVs), etc[1,5]. AC-DC converters, which are also known as rectifiers, are basically contained diodes and rectifiers and are very popular due to the absence of any control system for power diodes [3]. These methods use two or more converters where the harmonic generated by one converter is cancelled out by another by proper phase shift. Auto transformer based converters usually reduces the total harmonic distortion (THD) along with weight and size of transformer [4].Many methods based on the multi pulse switching have been proposed which are based on autotransformer or multi winding isolation transformer although both of them provides small size of transformer but need a complex structure also the autotransformer lacks the isolation between input and output & other also can be completely damaged by accidental overloading of one of the any phase because all primary windings are common. II.
OBJECTIVE OF PRESENT STUDY
The Present Study Is An Effort Towards Analyzing The Different Multi-Pulse AC To DC Converters In Solving The Harmonic Problem In A Three-Phase Converter System. The Effect Of Increasing The Number Of Pulses On The Performance Of AC To DC Converters Has Been Analyzed. For Performance Comparison The Major Factors Considered Are The Ripple Percentage, Form Factor And The Total Harmonic Distortion (THD)
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DOI:10.15680/IJIRSET.2016.0503112
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ISSN(Online) : 2319-8753 ISSN (Print) : 2347-6710
International Journal of Innovative Research in Science, Engineering and Technology (An ISO 3297: 2007 Certified Organization)
Vol. 5, Issue 3, March 2016
III.
MULTI-PULSE METHODS
Different rectifiers are used for conversion of AC supply into DC supply. For uncontrolled conversion, diodes have been preferred, while for the controlled conversion, thyristors have been implemented. The performance improvement of multi-pulse converter is achieved for total harmonics distortion (THD) in supply current, DC voltage ripples and form factor. All the simulations have been done for similar ratings of RL Load, for all the multi-pulse converters configurations, so as to represent a fair comparison among controlled and uncontrolled continuations of multi-pulse converters. The effect of increase in number of pulses in converter circuits for uncontrolled and controlled multipulse converter on input supply current and DC side voltage and current has been presented in this paper.There are two type of pulse converter according to controlling techniques first one uncontrolled and second one is controlled multi-pulse converter. Uncontrolled multi-pulse has fixed output and controlled multi-pulse converter has controlled output which can control by the firing angle ‘α’. There are various multi-pulse converters which classified according to number of pulse. Letussupposethatthenumberofpulseis‘m’FoisoutputfrequencyandFsissupplyfrequency Fo= mFs-----------(1) And length of pulse also depend on number of pulse pulse length= 2*pi/m(inrad)----------(2) IV.
SIMULATION MODEL OF MULTI PULSE CONVERTER
A. Six Pulse Converter The simulation block of three phase six pulse thyristor is shown in Fig 1. It consists of three phase ac source to supply .The line voltage are Vab, Vbc&Vca. A six pulse thyristor bridge is connected to the three phase supply. This is universal thyristor bridge. It consists six thyristor in a bridge manner, which converts the constant ac into the dc supply.
Discrete, Ts = 5e-005 s. pow ergui
V PQ
atan
cos
tan Inverse
cos
I
Divi de1
Acti ve & Reactive Power
Power Factor
power factor
inpu t power
outp ut powe r
3 Gain2 +
In signal THD
+ -
Total Harm oni c Di storsi on
v
Gai n3
Effi ci ency
Mean
P rodu ct -K-
Va
Di vi de2
i -
CM
effi ciency
-K-
THD
T HD Percentage
+
CM 1
L
Gai n1
Me an V alu e1
i + -
VM
v
VM 3 In
Vb
10
M ean Val ue
a3
C+
PWM
signal rms g
RM S
Scop e
C -K-
Uni versal B ri dge Di vi de
DC Machine F-
m
dc
Zi gzag P hase-S hifti ng Transform er
C
F+
c3
TL
B
BC-
S ubtract
+ A
b3
A+
A-
A-
B+
Out 1
Conn2 Conn3
A+
Vc
Mean
In1 Conn1
firin g an gle
Gain
Rippl e Percenta ge
DC V olta ge So urce Di splay
S cope3
Fig. 1.Six pulse thyristor converter B. Twelve Pulse Converter The simulation block of three phase twelve pulse thyristor is shown in Fig 2. It consists of three phase ac source to supply .The line voltage are Vab, Vbc&Vca. Two six pulse thyristor bridge is connected to the three phase supply. This is universal thyristor bridge. It consists six thyristor in a bridge manner, which converts the constant ac into the dc
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DOI:10.15680/IJIRSET.2016.0503112
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ISSN(Online) : 2319-8753 ISSN (Print) : 2347-6710
International Journal of Innovative Research in Science, Engineering and Technology (An ISO 3297: 2007 Certified Organization)
Vol. 5, Issue 3, March 2016
supply. The input of these converters is taken from the phase shifted secondary Zigzag transformer. These are two three phase transformers whose secondaries are connected in star. This configuration provides the phase shift of 30 degrees between the two converters. A synchronous six pulse generator is used to generate the pulses to the bridge circuit these pulses are used to fire the thyristors.
Dis crete, Ts = 5e-005 s. pow ergui
V PQ
ata n
cos
tan Inverse
cos
signal THD
I
Acti ve & Reactive Power
Di vi de1
Power Fa cto r
po wer factor
-KTotal Ha rm oni c Di storsi on
THD
THD P ercentage
i nput p ower
ou tpu t power
3
-K-
Gai n2
Di vi de2 In
i -
+
Gain3
Effi cie ncy
Mean
Product +
In1
CM Va
effi cie ncy
Gai n1
+ v -
Conn1
+ -
Conn3
A+
v
VM 3
a3
B+
g
PWM 1
+
C+
A
In
Mean
b3
A-
Vb
CM 1
L
Out 1
Conn2
VM
Mea n Va lue 1
i -
B
B-
c3
C-
M ean Val ue
C
signal rms
Uni versal Bri dge 1
Zig zag Phase-Sh ifti ng Transforme r 1
Su btract
I n1
RMS
Scope
Conn1
Vc
Out 1
Conn2
C
Conn3
PWM 2
A+
a3
-K -
g
B+
+
Di vi de
A
C+ b3
Ri ppl e Percentage
F+
c3
A+
TL
C
Uni versa l Bri dge 2
dc
Zigzag Ph ase-Shi fti ng T ransfo rm er2 m
DC Voltage Sourc e
DC Mac hine F-
C-
Ga in
B
B-
A-
A-
Di sp lay
10
firing an gle
Scope3
Fig. 2.Twelve pulse thyristor converter
C. Eighteen Pulse Converter The simulation blocks of three phase six pulse thyristor are shown in Fig 5.3. It consists of three ac voltage sources, Va, Vb&Vc .The line voltages are Vab, Vbc&Vca. Three six pulse thyristor bridge is connected to the phase supply. The inputs of these converters are taken from the output of three phase shifting transformers. These are three phase transformers. These three phase transformers provide the phase shift of 20 degrees between the three converters. A synchronized pulse generator is used to generate the pulses to the bridge circuit of the converters. These pulses are used to fire the thyristors. Dis crete, Ts = 5e-005 s. pow ergui
V PQ
ata n
cos
tan Inverse
cos
signal THD
I
Acti ve & Reactive Power
Di vi de1
Power Fa cto r
po wer factor
-KTotal Ha rm oni c Di storsi on
THD
THD P ercentage
i nput p ower
ou tpu t power
3
-K-
Gai n2
Di vi de2 In
+
Va
+ v -
effi cie ncy
Gai n1
i -
Gain3
Effi cie ncy
Mean
Product +
In1
CM
Conn1
a3
A-
+ -
v
+ A
In
Mean
b3 B
BC-
Mea n Va lue 1
VM 3
g
PWM 1
C+
Vb
CM 1
Conn3
A+ B+
filter L
Out 1
Conn2
VM
i -
c3
M ean Val ue
C
signal rms
Uni versal Bri dge 1
Zig zag Phase-Sh ifti ng Transforme r 1
Su btract
I n1
RMS
Scope
Conn1
Vc
Out 1
Conn2 Conn3
filter C
PWM 2
a3
-K g
B+
+
C+
Ri ppl e Percentage
Uni versal Bri dge 2
dc
Conn1
DC Machine
Out 1
Conn2
PWM 3
m
Conn3 a3
g
DC Voltage Source
F-
Zigzag Phase -Shi fti ng Tran sform er 2
F+
C
c3 I n1
A+
Ga in
B
TL
C-
Di vi de
A b3
B-
A+
A-
A-
A+
+
Di spl ay
A
B+ B
C+ A-
b3
B-
10 firing an gle
C-
C
Universal Bri dge
c3
Zigzag Ph ase-Shi fti ng T ransfo rm er1
Sco pe3
Fig. 3.Eighteen pulse thyristor converter D. Twenty Four Pulse Converter The simulation blocks of three phase six pulse thyristor are shown in Fig 4. It consists of three ac voltage sources, Va, Vb&Vc .The line voltages are Vab, Vbc&Vca. In the proposed design four six pulse thyristor bridge is connected to the
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DOI:10.15680/IJIRSET.2016.0503112
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ISSN(Online) : 2319-8753 ISSN (Print) : 2347-6710
International Journal of Innovative Research in Science, Engineering and Technology (An ISO 3297: 2007 Certified Organization)
Vol. 5, Issue 3, March 2016
phase supply. The inputs of these converters are taken from the output of four phase shifting transformers. These are three phase transformers. These three phase transformers provide the phase shift of 20 degrees between the three converters. Dis crete, Ts = 5e-005 s. pow ergui
V PQ
ata n
cos
tan Inverse
cos
signal THD
I
Acti ve & Reactive Power
Di vi de1
Power Fa cto r
po wer factor
10 Total Ha rm oni c Di storsi on
THD
THD P ercentage
i nput p ower
ou tpu t power
3
-K-
Gai n2
Di vi de2 In
+
i -
Gain3
Effi cie ncy
Mean
Product +
In1
CM Va
effi cie ncy
Gai n1
+ v -
Conn1
CM 1 Out 1
Conn2
VM B+
a3
filter L
A-
+ A
In
Mean
b3 B
BC-
v
VM 3
g
PWM 1
C+
Vb
+ -
Conn3
A+
Mea n Va lue 1
i -
c3
M ean Val ue
C
signal rms
Uni versal Bri dge 1
Zig zag Phase-Sh ifti ng Transforme r 1
Su btract
I n1
RMS
Scope
Conn1
Vc
Out 1
Conn2 Conn3
PWM 2
1
a3
g
B+
+
C+
Ri ppl e Percentage
C
Uni versal Bri dge 2
I n1
Zigzag Phase -Shi fti ng Tran sform er 2
Conn1
dc
Out 1
Conn2
DC Machine
Conn3
DC Voltage Source
A
F-
m
+
a3
A-
g
PWM 3 A+
Ga in
filter C
B c3
F+
C-
Di vi de
A b3
B-
TL
A-
A+
A+
B+ A-
-
b3
C
BC-
Di spl ay
B
C+
10 firing an gle
Universal Bri dge
c3
Zigzag Ph ase-Shi fti ng T ransfo rm er1 I n1 Conn1 Out 1
Conn2 Conn3
PWM 4 A+
g + A
a3
B+
B
C+ A-
b3
C
C-
S cope1
Uni versa l Bri dge1
Bc3
Zigzag Ph ase-Shi fti ng T ransfo rm er2
Fig. 4.Twenty-Four pulse thyristor converter V.
EXPERIMENTAL RESULTS
The results of six pulse, twelve pulse and eighteen pulse thyristor converters are compared. This can be done by comparing the waveform of input current and output voltage with different values of firing angles on the basis of ripple content and THD. It is observed by seeing the waveform of input current that the waveform of higher pulse converter is more nearer to sinusoidal. The voltage waveforms are also compared the ripple in the output voltage decreases as the number of pulses is increased. As seen from the result of of 6, 12, 18 and 24 pulse controlled converter with 10 degree firing angles that the ripple in six pulse converter is greater than twelve pulse, eighteenand twenty-four pulse converter. That means with the increase in pulse number, output voltage and input current THD is improved. When we increased the firing angles output voltage ripple and THD of input current is also increased. Comparison of result for 6, 12, 18, 24- pulse controlled converters is given in Table.1. Results of 6, 12, 18 and 24 pulse controlled converter with 10 degree firing angles Table-1 S no.
Converter / Firing Angle
1. 2 3 4
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6 Pulse 12 Pulse 18 Pulse 24 Pulse
Is THD% 25.81 8.59 9.02 0.88
10 degree VoRipple% 0.34 0.89 0.94 0.03
DOI:10.15680/IJIRSET.2016.0503112
P.F. 0.95 0.91 0.87 0.95
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ISSN(Online) : 2319-8753 ISSN (Print) : 2347-6710
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Vol. 5, Issue 3, March 2016
VI.
CONCLUSION
The various isolated multi-pulse configurations were simulated using MATLAB/SIMULINK and the results have been presented in this paper in Table1. The effect of pulse variation on different multi-pulse converters reveals that with DC Motor load because of inductance there is smoothing effect on current, therefore current THD decreases. The discussed technique can be considered to be the better alternatives for power quality improvement because of the reduced size of the converter, lower cost and higher efficiency as compared to other methods of power quality improvement. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]
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