Transcript The Application of Three-level NPC Converter to WES

The Application of Three-level
NPC Converter to WES
By: Amir Yazdani
[email protected]
PhD candidate
University of Toronto
Feb. 20, 2004
Abbreviations
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NPC
WES
VSC
BTB
Neutral-Point diode Clamped converter
Wind Energy System
Voltage-Sourced Converter
Back-To-Back (AC/DC/AC) converter
system
PWM Pulse Width Modulation
THD Total Harmonic Distortion
Outline
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Wind turbine characteristics
Variable-Speed technology
Motivations for using the Three-Level NPC in
WES
Three-Level NPC circuit and operation
Current research
Conclusions
Wind Turbine Characteristics
Variable-Speed WES
(General)
1. Adjusts the generator speed to obtain the
maximum power
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Optimized power capture
2. Connects the generator to the grid via a
two-level VSC BTB
 Decoupling of the grid and turbine
 Reactive-power/AC-voltage control
 Good power quality
Variable-Speed WES
(Induction machine and Two-Level BTB)
 Gearbox Wear
Variable-Speed WES
(Synch. machine and Two-Level BTB)
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No Gearbox
Why Three-Level NPC?
Demand for higher power WES
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Higher DC voltage by use of ordinary
switches (lower current, higher efficiency)
Faster dynamic response
Superior power quality
(lower THD, lower torque pulsations)
Comparable switching losses with respect to
Two-Level BTB
Three-Level NPC vs. Two-Level
VSC
Two-Level VSC
Three-Level NPC
PWM Spectra
Two-Level VSC
Three-Level NPC
Waveforms of Three-Level
NPC
Variable-Speed WES
(Synch. machine and Three-Level NPC BTB)
Demerits
Higher component count
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Two capacitor banks
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More complicated PWM and control
(e.g. C-voltage equalization issue)
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Mid-point current
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Current research
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Mathematical modeling
Control
DC-voltage balancing
DC-link voltage regulation of the BTB system
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Fault analysis
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Conclusion
The use of Three-Level NPC technology in WES
offers:
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More economical designs
Lower THD waveforms
Superior dynamic performance