Electronic Theses and Dissertations

Identifier

2659

Date

2016

Date of Award

4-26-2016

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

Eddie Jacobs

Committee Member

M. Shah Jahan

Abstract

Large-scale grid-connected photovoltaic (PV) plants are proliferating and power system operators are imposing strict grid code. This dissertation proposes an advanced control methodology to enhance the dynamic performance of a large-scale two-stage grid-connected PV plants. The dynamic performance augmentation is achieved in terms of enhancing the low-voltage ride-through (LVRT) capability and transient stability. Since a PV system is nonlinear in nature, a fuzzy logic controller (FLC) has been implemented for the active power insertion considering the severity of grid voltage dip. The effectiveness of the proposed methodology in improving the LVRT of the grid-connected PV system is verified by applying both balanced and unbalanced faults in the grid side. The proposed method is able to protect the DC-link overvoltage, and is capable of suppressing the transient overcurrent and inserting the reactive current. This dissertation also deals with the investigations of transient stability augmentation of a hybrid power system consisting of a PV power generation source, a doubly-fed induction generator (DFIG)-based wind energy system, and a synchronous generator (SG). A parallel-resonance bridge type fault current limiter (PRBFCL) is proposed to augment the transient stability of a hybrid power system. Simulation results obtained from the Matlab/Simulink software show that the proposed PRBFCL is effective in maintaining stable operation of the PV, wind generator, and synchronous generator during the grid fault. Moreover, the performance of the PRBFCL is better than that of the BFCL and the FRT methods.Furthermore, this dissertation proposes three nonlinear controllers such as fuzzy logic controller (FLC), static nonlinear controller (SNC), and adaptive-network-based fuzzy inference system (ANFIS)-based variable resistive type fault current limiter (VR-FCL) to augment the transient stability of the same hybrid power system. Appropriate resistance generation of the VR-FCL during a grid fault to provide better transient stability is the main contribution of the work. Simulation results show that the proposed FLC, SNC or ANFIS based VR-FCL is effective in improving the transient stability of the studied hybrid system. Moreover, all the proposed methods exhibit almost similar performance. Therefore, any of the methods can be chosen for the transient stability enhancement of the hybrid power 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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