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amir symp

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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:

Abbreviations NPC N eutral- P oint diode C lamped converter WES W ind E nergy S ystem VSC V oltage- S ourced C onverter BTB B ack-To- B ack (AC/DC/AC) converter system PWM P ulse W idth M odulation THD T otal H armonic D istortion

Outline:

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

Wind Turbine Characteristics:

Wind Turbine Characteristics

Variable-Speed WES (General):

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):

Variable-Speed WES (Induction machine and Two-Level BTB) Gearbox Wear

Variable-Speed WES (Synch. machine and Two-Level BTB):

Variable-Speed WES (Synch. machine and Two-Level BTB) No Gearbox

Why Three-Level NPC?:

Why Three-Level NPC? 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 Demand for higher power WES

Three-Level NPC vs. Two-Level VSC:

Three-Level NPC vs. Two-Level VSC Two-Level VSC Three-Level NPC

PWM Spectra:

PWM Spectra Three-Level NPC Two-Level VSC

Waveforms of Three-Level NPC:

Waveforms of Three-Level NPC

Variable-Speed WES (Synch. machine and Three-Level NPC BTB):

Variable-Speed WES (Synch. machine and Three-Level NPC BTB)

Demerits:

Demerits Higher component count Two capacitor banks More complicated PWM and control (e.g. C-voltage equalization issue) Mid-point current

Current research:

Current research Mathematical modeling Control DC-voltage balancing DC-link voltage regulation of the BTB system Fault analysis

Conclusion:

Conclusion The use of Three-Level NPC technology in WES offers: More economical designs Lower THD waveforms Superior dynamic performance

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