Electronic Theses and Dissertations

Identifier

2593

Date

2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Electrical and Computer Engr

Concentration

Electrical Engineering

Committee Chair

Mohd. Hasan Ali

Committee Member

Russell Deaton

Committee Member

M. Shah Jahan

Committee Member

John Hochstein

Abstract

Presently, the doubly fed induction generator (DFIG) is the most popular technology to harness the wind power due to its ability to adapt to variable wind speed and to capture more wind energy. However, the DFIG based variable speed wind generator is vulnerable to faults, as the stator of the DFIG is directly connected to the grid. Both symmetrical and asymmetrical faults may cause the DFIG face high mechanical stress, which may lead to mechanical damage. According to the grid code, the transient stability enhancement of the DFIG system is very important. Though the DFIG has a salient feature of the fault ride through capability, this is not sufficient to preserve the regulations of the grid code at all situations. In this dissertation, in order to enhance the transient stability of the DFIG based variable speed wind generation system, first the performance of the different types of internal controlled devices such as, crowbar, DC chopper and parallel capacitor with the DC link of DFIG system has been investigated. From the analysis, it is established that the internal controlled devices cannot maintain the grid code during all types of network faults. This testifies the importance of the application of the auxiliary devices to enhance the transient stability of the DFIG based wind generator system.An investigation has been made to explore a device which could provide the best performance in terms of transient stability enhancement for a grid-connected DFIG system during faults. Ultimately, a DC resistive superconducting fault current limiter (SFCL) is proposed because of its best performance. The DC resistive SFCL reduces the system power losses during stable operation of the network with improved system efficiency, in comparison with the conventional SFCL. One of the salient features of using the SFCL is that it does not require any controller, and immune to any sort of cyber threat or vulnerability. To verify the transient stability performance of the DFIG based wind generator system with the proposed DC resistive SFCL, both the symmetrical and asymmetrical faults are considered. The performance of the DC resistive SFCL is compared to that of the series dynamic braking resistor (SDBR) and the conventional SFCL. Simulations are carried out by using the Matlab/Simulink software. Simulation results clearly indicate that the proposed DC resistive SFCL shows the best performance to enhance the transient stability of the DFIG based wind generator system.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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