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Fault Ride Through Techniques of DFIG-based Wind Energy Systems

Presenter: Lingling Fan, Co-authors: Chanxia Zhu, Minqiang Hu (Southeast University, Nanjing China)

Assistant ProfessorElectrical Engineering

University of South FloridaTampa, FL 33620

USA

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Outline

• Objectives• Analysis of DFIG behavior during faults• Single phase fault ride through• Three-phase fault ride through• Simulation results• Conclusion

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Objective

• Design control schemes to help DFIG ride through faults

• Faults: Balanced (symmetrical) or unbalanced (unsymmetrical)

• In literature, ride through balanced faults and unbalanced faults are treated separately

• A control scheme for all

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Doubly Fed Induction Generator

fm

RSCAC/DC

Pr = sPs

Ps

GSCDC/AC

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DFIG converter control loops

GSCDC/AC

RSCDC/AC

Analysis of DFIG behavior during unbalanced faults

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Unbalanced stator currents

Positive sequence(fe)

Negative sequence(-fe)

Zero sequence

Ir: fe-fm=sfe

Rotor currents

Ir: -fe-fm=-(2-s)fe

s: slip = 1-fm/fe

fm: electric frequency corresponding to rotating speed.

fe: nominal frequency

60 Hz (stator) – 50 Hz (rotating

speed) = 10 Hz

-60 Hz (stator) – 50 Hz (rotating

speed) = -110 Hz

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Analysis of DFIG behavior during balanced faults

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Reference frames

Pos. Neg. Sequences and DC can be separated by a dc filter!

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Extraction scheme

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Fault ride through schemes- modify RSC current control loops

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An alternative- PR controller

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Simulation Results – unbalanced fault

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Simulation Results – unbalanced fault

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Simulation Results – unbalanced fault

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Simulation results – balanced fault

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Simulation results – balanced fault

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Conclusion

• Proportional Resonant control is proposed for RSC to mitigate rotor current high frequency components and surge.

• Simulation results demonstrate the effectiveness.

• A major contribution: both unbalanced and balanced faults are considered.