PQ Forum 2011 proceedings http://www.leonardo-energy.org/power-quality-forum-2011-tue-eindhoven

1. 31/01/2011
Leonardo ENERGY Power Quality Forum 2011
Case study of harmonic
current interaction:
VSD and Lamps
Vladimir Ćuk
Eindhoven University of Technology
Electrical Energy Systems
Introduction
Problem outline:
• Current transients noticed in the factory lighting system
(peaks increasing three times)
• A Variable Speed Drive (VSD) is causing voltage
notches (voltage harmonics) on the same busbar
• Possible resonance?
/ Electrical Energy Systems 27.01.2011. PAGE 1
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Schematic diagram
/ Electrical Energy Systems 27.01.2011. PAGE 2
Measurement results (1)
Current of lamps in phase 1 during one recording
/ Electrical Energy Systems 27.01.2011. PAGE 3
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Measurement results (2)
Voltage waveform in three regimes
/ Electrical Energy Systems 27.01.2011. PAGE 4
Measurement results (3)
Current waveform in three regimes
/ Electrical Energy Systems 27.01.2011. PAGE 5
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Processed results (1)
THDs measured with a PQ analyzer
0 100 200 300 400 500 600
5 50
Voltage THD
4.5 Current THD 45
4
40
3.5
Voltage THD [%]
Current THD [%]
3 35
2.5 30
2
25
1.5
20
1
0.5 15
0 100 200 300 400 500 600
Time [s]
/ Electrical Energy Systems 27.01.2011. PAGE 6
Processed results (2)
THDs calculated over 20 ms periods
0 0.5 1 1.5 2 2.5 3
7 90
Voltage THD
6 Current THD 80
70
5
Voltage THD [%]
Current THD [%]
60
4
50
3
40
2
30
1 20
0 10
0 0.5 1 1.5 2 2.5 3
Time [s]
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Processed results (3)
Voltage harmonics in all three regimes
/ Electrical Energy Systems 27.01.2011. PAGE 8
Processed results (4)
Current harmonics in all three regimes
/ Electrical Energy Systems 27.01.2011. PAGE 9
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Sliding window recursive DFT (1)
29th voltage and current harmonic
3 25
20
2
15
10
29th current harmonic [A]
29th voltage harmonic [V]
1
5
0 0
-5
-1
-10
-15
-2
-20
-3 -25
8 8.5 9 9.5 8 8.5 9 9.5
time [s] time [s]
/ Electrical Energy Systems 27.01.2011. PAGE 10
Sliding window recursive DFT (2)
29th voltage and current harmonic
50
40
30
20
Current [A]
Current [A]
10
0
-10
-20
-30
4 -40 4
-50
13th 3
3
25th
11th 2 2
23rd
7th 1 19th 1 Time [s]
Time [s] 17th Harmonic 0 Time [s]
5th Harmonic 0
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Calculated impedance of lamps
0.5
0.45
Load impedance [Ohm] 0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0 500 1000 1500 2000 2500
frequency [Hz]
/ Electrical Energy Systems 27.01.2011. PAGE 12
Laboratory measurements on a lamp (1)
Current waveform with a clean voltage
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Laboratory measurements on a lamp (2)
Current spectrum with a clean voltage
3rd
5th
/ Electrical Energy Systems 27.01.2011. PAGE 14
Laboratory measurements on a lamp (3)
Simulated low voltage distortion
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Laboratory measurements on a lamp (4)
Simulated higher voltage distortion
/ Electrical Energy Systems 27.01.2011. PAGE 16
Laboratory measurements on a lamp (5)
Simulated highest voltage distortion
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Harmonic fingerprint of the lamp (1)
Voltage – 3rd harmonic Current – 3rd harmonic
/ Electrical Energy Systems 27.01.2011. PAGE 18
Harmonic fingerprint of the lamp (2)
Voltage – 17th harmonic Current – 17th harmonic
/ Electrical Energy Systems 27.01.2011. PAGE 19
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Calculated lamp impedance
Measured lamp impedance and a fitted function
Fitted curve – C = 47.7 μF
/ Electrical Energy Systems 27.01.2011. PAGE 20
Conclusions
• Differences in measurements – Scope and PQ analyzer
• A parallel resonance is not being excited
• Peaks are caused buy harmonic distortion - similar response
without notches
• These lamps create harmonics, but react linearly to voltage
harmonics – parallel capacitance
• Solution – electrical separation
/ Electrical Energy Systems 27.01.2011. PAGE 21
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