Dissertation Defense Announcement

The Herff College of Engineering announces the final dissertation defense of 

Md Kamal Hossain

for the degree of Doctor of Philosophy

March 29, 2016 at 9:30 am in 218, Engineering Science Building 

Major Advisor: Mohd. Hasan Ali, PhD

Dynamic Performance Improvement of Grid-Connected Photovoltaic (Pv) System By Nonlinear Controlled Devices

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. Both active and reactive power control schemes are incorporated according to the recent grid code. 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. The PRBFCL is designed in such a way that it can provide sufficient damping characteristics to the studied power system during the grid fault. 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 same hybrid power system. Appropriate resistance generation of the VR-FCL during a grid fault to provide better transient stability is the major contribution of the work. Simulation results show that the proposed FLC, SNC or ANFIS based VR-FCL are 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.