fundamentals of harmonics
DESCRIPTION
Fundamentals of Harmonics. Overviews. Definitions and Nonlinear Loads Harmonics Power Quantities Harmonic Sequences Triplen Harmonics Harmonics Indices Harmonic Sources Classical Sources and Power Electronics Locating Harmonic Sources Impacts of Harmonics Interharmonics. - PowerPoint PPT PresentationTRANSCRIPT
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Fundamentals of Harmonics
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Overviews
• Definitions and Nonlinear Loads• Harmonics Power Quantities• Harmonic Sequences• Triplen Harmonics• Harmonics Indices• Harmonic Sources
– Classical Sources and Power Electronics
• Locating Harmonic Sources• Impacts of Harmonics• Interharmonics
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1.1 Nonlinear Loads• Fundamentals of
Nonlinear Loads• Fourier representation
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1.2 Harmonic Phenomena
• Harmonics in voltage and current– CAUSE: Current– Effect: Voltage
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Examples of Harmonics I
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Examples of Harmonics II
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Examples of Harmonics III
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Harmonics versus Transients
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Power Factor
• Consider first a sinusoidal voltage and current
1rms1rms1
rms1rms1
rms1rms1
T
011
1rms1
coscosIVcosIV
pf
IV
dttcosItcosVT1
SP
pf
2/VV
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RMS
In case of harmonics,
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Harmonic Phase Sequences
• In a balanced three-phase circuit:– the fundamental defines the positive phase
sequence (or rotation) such as ABC or xyz or 321, and the 4th, 7th, 10th, …, are also positive sequence
– the 2nd, 5th, 8th, 11th ,…, are negative sequence (eg CBA)
– the 3rd, 6th, 9th, …, are zero seq (all in phase)
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1 +
2 -
3 0
4 +
5 -
6 0
7 +
8 -
9 0
10 +
1 +
3 0
5 -
7 +
9 0
11 -
13 +
15 0
17 -
19 +
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Triplen harmonics• Harmonic order h values that are multiples
of 3 are called triplen harmonics• If the three phase circuit is balanced, the
triplen harmonics are all in phase (zero sequence)– triplen harmonic line currents will be additive
at the neutral of a wye circuit by KCL (zero triplens if three-wire ungrounded wye or if delta)
– triplen harmonic line-line voltages will be zero by KVL
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Transformer
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Harmonic Indices
• Total harmonic distortion = THD
1
h
2h
2h
M
MTHD
max
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221
21
h
1h
2h
THD1MRMS
THDMMMRMS
:Note
max
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Harmonic Indices
• Total demand distortion = TDD
L
h
2h
2h
I
MTDD
max
PCC coupling common ofpoint at frequency
lfundamentaat demandcurrent rmsmax I
:Note
L
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Harmonics Sources• Conventional Sources
– Single-phase power supplies– Fluorescent lighting– ASD for HVAC and elevators
• Industrial Sources– Power converters– DC and AC drives– Saturable devices
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4.1.1 SMPS
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4.1.2 Fluorescent lighting
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Power Converter