2. 6-18 pulse - exp 2
DESCRIPTION
2. 6-18 pulse - Exp 2TRANSCRIPT
Experiment II
6/18 PULSE AC TO DC CONVERTER
Group III
1. Adlan Bagus Pradana
2. SVSS Chandrasekhar
DEPARTMENT OF ELECTRICAL ENGINEERING
M. Tech Power Electronics, Electrical Machines & Drives (PEEMD)
EEP842 POWER ELECTRONICS LABORATORY - 1.5 Credits
6/18 PULSE AC TO DC CONVERTER
EXPERIMENT NO. 2
I. Motivation:
DC supply is gaining very much importance than AC in recent years with the improvement in
electronic equipment. But rectification circuits introduce more harmonics into the AC system. Hence
the quality of the supply reduces. So rectifier should be designed such that the quality of AC supply
should be maintained. As per the IEEE standards current THD should be less than 5%. To attain this
there are two ways. One is to design filters to reduce harmonics and other to go for multilevel or
multipulse converters. This experiment introduces some of the multipulse AC to DC converters. With
the input three phase supply the output pulses can be multiple of six. In this experiment 6 and 18
converter performance are observed. A different autotransformer is used to obtain 3-phase outputs
with 20 degrees for 18 pulse configuration.
II. Objective:
1. Study characteristics of a 6-pulse, and 18-pulse uncontrolled three-phase bridge rectifiers with
filtered output.
(a) Record the AC supply voltage and current waveform, harmonic spectrum, THD, crest factor, rms
value, distortion factor, displacement factor and power factor, output DC voltage average value,
peak-peak ripple and ripple factor in 6-pulse and 18-pulse uncontrolled rectifiers with (i) resistive
load (ii) dc series inductor filter, (iii) dc shunt capacitor filter, and (iv) dc series inductor and shunt
capacitor (LC) filter at two loads.
(b) Simulate in MATLAB with SPS toolbox, the AC supply voltage and current waveform, Harmonic
spectrum, THD, crest factor, rms value, distortion factor, displacement factor and power factor,
output DC voltage average value, peak-peak ripple and ripple factor in 6-pulse and 18-pulse
uncontrolled rectifiers with (i) resistive load (ii) dc series inductor filter, (iii) dc shunt capacitor filter,
and (iv) dc series inductor and shunt capacitor (LC) filter at two loads using same parameters as in
part 1(a).
With this transformer arrangement the dc link voltage obtained is slightly higher than that of a 6-
pulse diode bridge rectifier output voltage, due to 18-pulse rectification. To make the proposed ac-
dc converter suitable for retrofit applications, the transformer design is modified to make the dc link
voltage same as that of 6-pulse diode bridge rectifier.
Fig.5 shows the schematic diagram of an 18-pulse ac-dc converter suitable for retrofit applications. It
also shows the winding connection diagram for achieving different voltage ratios from the
autotransformer by simply varying the tapping positions on the windings. This ensures that both the
output voltages are still having the required phase shift of ±200 (for achieving the eighteen-pulse
operation).
III. Theory:
To achieve the 6-pulse rectifier operation, the following connections are been done, To achieve the
18-pulse rectifier operation, the following conditions have to be satisfied:
a) Three sets of balanced 3-phase line voltages are to be produced, which are either 200 or 400 out
of phase with respect to each other. Here, ± 200 phase shift is used to reduce the size of magnetics.
b) The magnitude of these line voltages should be equal to each other to result in symmetrical pulses
and reduced ripple in output dc voltage. Fig.1 (a) shows the winding connection diagram of the
proposed autotransformer for achieving an 18-pulse rectification and Fig.1 (b) represents the
relationship among various phase voltages. From the supply voltages, two sets of 3-phase voltages
(phase shifted through +200 and -200) are produced. The number of turns required for +200 and -
200 phase shift are calculated as follows. Consider phase ‘a’ voltages as shown in Fig. 1a:
Figure 1 (a)
Figure 1(c) shows the 18 pulse configuration for AC to DC converter with differential transformer
configuration. The interface transformer connections at the output of the bridges avoid the
circulating currents to flow between the bridges and give 18 pulse output. The simulink diagram of
the interface transformer is shown at right side. The operation is as follows. When a circulating
current tries to flow from bridge1 to bridge-2 then EMF’s will induce in the windings such that it
opposes current flow through them. Thus circulating current can be made zero and the current from
the bridges flows out to load.
Figure 1 (b)
IV. Pre-experimental questions:
1. What is the advantage of configuration used in this experiment?
2. What is the phase shift required at the output for 18 pulse output?
3. What is meant by pulse multiplication and how it can be obtained?
V. Equipment and components:
1. 18 pulse AC-DC converter setup.
2. DC and AC voltmeters.
3. DC and AC ammeters.
4. 3-phase auto transformer.
5. Power analyzer.
6. Multimeter.
18-PULSE CONFIGURATION
Figure 1 (c)
VI. Procedure:
18-pulse converter:
1. Connect the circuit diagram as per the circuit diagram.
2. Apply the three phase input voltage.
3. Vary the load and obtain the input voltage, input current, pf, DPF, DF, THD, and ripple factor at
two different loads.
VII. Experiment Observations:
A. Tabulation Table
No Vi Ii CF-V CF-I THD-I DPF Vo Vo (p-p) Filter Pulse1 51.8 1.128 1.4 1.7 28.9 1 69.3 3.6 No filter 62 52.1 3.279 1.4 1.3 28.4 1 67.5 3.6 No filter 6
3 50 1.089 1.4 1.7 28.9 1 66 3.3 L filter 64 49.6 3.117 1.4 1.3 28.4 1 65.05 3.1 L filter 65 50.28 2.02 4.3 1.4 87.5 0.89 68.92 0.09 C filter 66 50 4.78 3.2 1.4 79.2 0.94 67.56 0.37 C filter 67 50.89 1.247 2.2 1.4 60.4 0.96 67.46 0.21 L-C filter 68 50.52 3.205 1.6 1.4 36.7 0.99 66.53 0.2 L-C filter 69 50.45 3.398 1.4 1.4 6.9 0.98 100.2 1.6 No filter 18
10 51.35 8.04 1.4 1.4 7.3 0.99 100.6 1.8 No filter 1811 50.81 1.249 1.4 1.4 7.6 1 96.4 1.7 L filter 1812 48.9 2.672 1.3 1.4 6.5 1 92.4 1.3 L filter 1813 50.17 1.603 1.4 1.7 22.7 0.98 96.9 0.3 C filter 1814 48.7 2.887 1.4 1.8 16 0.98 92.8 0.4 C filter 1815 49.99 3 1.4 1.4 8.1 1 94.2 0 L-C filter 1816 98.8 3.324 1.4 1.4 8.3 1 193 0 L-C filter 18
B. Graph
1. 6 Pulse, No Filter
No Remark Graph
1 V & I
2 Power
3 THD-I
4 Vo (p-p)
2. 6 Pulse, L Filter
No Remark Graph
1 V & I
2 Power
3 THD-I
4 Vo (p-p)
3. 6 Pulse, C Filter
No Remark Graph
1 V & I
2 Power
3 THD-I
4 Vo (p-p)
4. 6 Pulse, L-C Filter
No Remark Graph
1 V & I
2 Power
3 THD-I
4 Vo (p-p)
5. 12 Pulse, No Filter
No Remark Graph
1 V & I
2 Power
3 THD-I
4 Vo (p-p)
6. 12 Pulse, L Filter
No Remark Graph
1 V & I
2 Power
3 THD-I
4 Vo (p-p)
7. 12 Pulse, C Filter
No Remark Graph
1 V & I
2 Power
3 THD-I
4 Vo (p-p)
8. 12 Pulse, L-C Filter
No Remark Graph
1 V & I
2 Power
3 THD-I
4 Vo (p-p)
C. Result
Input Current THD
0
20
40
60
80
100
1 2
Load
% T
HD
6P-No filter"
6P-L Filter
6P-C Filter
6P-LC Filter
12P-No Filter
12P-L Filter
12P-C Filter
12P-LC Filter
Output Voltage Peak-Peak
00.5
11.5
22.5
33.5
4
1 2
Load
V p
-p
6P-No filter"
6P-L Filter
6P-C Filter
6P-LC Filter
12P-No Filter
12P-L Filter
12P-C Filter
12P-LC Filter
D. Conclusion
From experiment we can conclude as follow :
1. Current input THD and output voltage peak to peak are relatively independent from load change
2. Effect of pulse increasing from 6 to 18 pulse is decreasing input current THD and output voltage
peak to peak (ripple)
VIII. Simulation Observation
Continuous
powergui
V4
v+-
V3
V2
66.57
V1
Vabc
I abcA
B
C
a
b
c
V-I
v+-
V
A
B
C
Three-Phase Source
0.6614
0.7177THD1
signal THD
THD
RMS
RMS1
RMS
RMS
PQ1
V
I
PQ
PQ
Load
L
I3
27.22
I2
0.02263
I1
i+ -
I
C
A
B
C
+
-
Bridge
6-Pulse Model
Continuous
powergui
V4
v +-
V3
V2
64.94
V1
Vabc
I abcA
B
C
a
b
c
V-I
v+-
V
A+
B+
C+
A-
B-
C-
a3
b3
c3
Transformer2
A+
B+
C+
A-
B-
C-
a3
b3
c3
Transformer1
A+
B+
C+
A-
B-
C-
a3
b3
c3
Transformer
A
B
C
Three-Phase Source
0.04264
0.05529THD1
signal THD
THD
RMS
RMS1
RMS
RMS
PQ1
V
I
PQ
PQ
Load
L
I3
28.75
I2
0.05478
I1
i+ -
I
A
B
C
N
GroundingTransformer 1
A
B
C
N
GroundingTransformer
C
A
B
C
+
-
Bridge2
A
B
C
+
-
Bridge1
A
B
C
+
-
Bridge
18-Pulse Model
A. Tabulation Table
No Vi Ii THD-I Vo Vo (p-p) Filter Pulse1 49.1 0.2849 25.55% 69.44 10 No filter 62 46.31 0.4292 23.74% 65.5 12 No filter 63 49.08 0.2847 25.49% 69.39 12 L filter 64 46.31 0.4284 23.71% 65.39 15 L filter 65 50.35 0.2987 25.74% 71.2 12 C filter 66 45.51 0.4406 24.15% 64.37 12 C filter 67 50.25 0.2985 25.73% 71.08 10 L-C filter 68 45.51 0.4394 24.22% 64.22 13 L-C filter 69 49.16 0.2582 4.035% 62.36 1.5 No filter 1810 48.95 0.3919 1.305% 61.91 0.8 No filter 1811 49.16 0.2582 3.766% 62.32 1.5 L filter 1812 48.95 0.3919 1.415% 61.9 0.8 L filter 1813 49.14 0.258 3.729% 62.31 1 C filter 1814 48.94 0.3924 1.282% 61.89 0.7 C filter 1815 49.27 0.2592 4.028% 62.54 2 L-C filter 1816 48.93 0.3924 1.251% 61.88 0.8 L-C filter 18
B. Graph
1. 6-Pulse, No Filter
No Remar
k
1 Vin
2 I
3 Vout
2. 6-Pulse, L Filter
No Remar
k
1 Vin
2 I
3 Vout
3. 6-Pulse, C Filter
No Remar
k
1 Vin
2 I
3 Vout
4. 6-Pulse, L-C Filter
No Remar
k
1 Vin
2 I
3 Vout
5. 6-Pulse, No Filter
No Remar
k
1 Vin
2 I
3 Vout
6. 12-Pulse, L Filter
No Remar
k
1 Vin
2 I
3 Vout
7. 12-Pulse, C Filter
No Remar
k
1 Vin
2 I
3 Vout
8. 12-Pulse, L-C Filter
No Remar
k
1 Vin
2 I
3 Vout
C. Result
Input Current THD
0.00%
5.00%
10.00%
15.00%
20.00%
25.00%
30.00%
1 2
Load
% T
HD
6P-No filter"
6P-L Filter
6P-C Filter
6P-LC Filter
12P-No Filter
12P-L Filter
12P-C Filter
12P-LC Filter
Output Voltage Peak to Peak
02468
10121416
1 2
Load
Vp
p
6P-No filter"
6P-L Filter
6P-C Filter
6P-LC Filter
12P-No Filter
12P-L Filter
12P-C Filter
12P-LC Filter
D. Conclusion
From experiment we can conclude as follow :
1. Current input THD and output voltage peak to peak are relatively independent from load change
2. Effect of pulse increasing from 6 to 18 pulse is decreasing input current THD and output voltage
peak to peak (ripple)
3. Filter usage is not quite effective for decreasing input current THD
4. Decreasing of output voltage peak to peak by usage of filter is more effective for 6 pulse
converter, but not so effective for 18 pulse converter
IX. Precautions:
1. Connections must be tight.
2. Capacitor must be discharged before disconnecting and conducting another experiment.
X. REFERENCES:
1. Bhim Singh, G.Bhuvaneswari and Vipin garg, “A Novel Polygon Based 18-Pulse AC– DC Converter
for Vector Controlled Induction Motor Drives.”, IEEE transactions on power electronics, vol-22, No-2,
pg-488-496 March-2007.
XI. INFERENCE:
From both of experiment and simulation we can conclude as follow :
1. Current input THD and output voltage peak to peak are relatively independent from load change
2. Effect of pulse increasing from 6 to 18 pulse is decreasing input current THD and output voltage
peak to peak (ripple)
3. Decreasing of input current THD and decreasing of voltage peak to peak by increasing pulse is
clearer in simulation than inexperiment. It is caused by factor below :
a. Experiment carefullness
b. Measurement equipment carefullness
c. Experiment apparatus