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The Application of Three-level NPC Converter to WES. By: Amir Yazdani yazdani@power.ele.utoronto.ca PhD candidate University of Toronto Feb. 20, 2004. Abbreviations. NPC N eutral- P oint diode C lamped converter WES W ind E nergy S ystem VSC V oltage- S ourced C onverter
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The Application of Three-level NPC Converter to WES By: Amir Yazdani yazdani@power.ele.utoronto.ca PhD candidate University of Toronto Feb. 20, 2004
Abbreviations • NPC Neutral-Point diode Clamped converter • WES Wind Energy System • VSCVoltage-Sourced Converter • BTB Back-To-Back (AC/DC/AC) converter system • PWMPulse Width Modulation • THD Total Harmonic Distortion
Outline • Wind turbine characteristics • Variable-Speed technology • Motivations for using the Three-Level NPC in WES • Three-Level NPC circuit and operation • Current research • Conclusions
Variable-Speed WES (General) • Adjusts the generator speed to obtain the maximum power • Optimized power capture • 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) • No Gearbox
Why Three-Level NPC? Demand for higher power WES • 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
Demerits • Higher component count • Two capacitor banks • More complicated PWM and control (e.g. C-voltage equalization issue) • Mid-point current
Current research • Mathematical modeling • Control • DC-voltage balancing • DC-link voltage regulation of the BTB system • Fault analysis
Conclusion The use of Three-Level NPC technology in WES offers: • More economical designs • Lower THD waveforms • Superior dynamic performance