DESIGN AND ANALYSIS OF SYNCHRONIZATION TECHNIQUES FOR CONTROL OF POWER ELECTRONIC CONVERTERS

Abstract

The increasing integration of renewable energy sources into electrical power systems has necessitated advanced synchronization techniques for power electronics converters. This thesis investigates synchronization methods, with particular emphasis on Phase-Locked Loop (PLL) technologies, to address challenges in grid-integrated systems under various disturbances. The primary objective is to develop and validate enhanced synchronization algorithms that overcome limitations of conventional PLLs in applications including photovoltaic systems, doubly fed induction generator (DFIG) wind energy converters, and electric vehicles. A comprehensive methodology combining mathematical modelling, stability analysis, extensive MATLAB Simulink simulations, and experimental validation using OPAL- RT real-time simulator was employed. Multiple PLL architectures were evaluated under abnormal grid conditions including voltage sags/swells, frequency jumps, DC offsets, and harmonic distortions. The research examined single-phase and three-phase PLLs, including Synchronous Reference Frame (SRF), Second-Order Generalized Integrator (SOGI), Least Mean Square (LMS), Least Mean Fourth (LMF), Modified Synchronous Reference Frame (MSRF), and fractional-order PLLs. Key findings demonstrate that the LMF PLL outperforms SRF PLL under phase shift and frequency change disturbances, while Type III Enhanced PLL exhibits superior frequency response with polluted grid voltage and DC offset. The proposed fractional- order FO-LPFO-PI MSRF-PLL with optimized parameters shows enhanced stability during grid abnormalities. Additionally, the novel H-LMS-SOGI PLL architecture provides exceptional dynamic responses, surpassing conventional structures under all adverse grid conditions tested. Experimental validation of DFIG systems with LMF- PLL confirms satisfactory performance under variable wind speeds and grid disturbances. This research significantly contributes to grid stability and renewable energy integration by providing validated solutions for maintaining reliable power system operation with high penetration of distributed energy resources. The dual validation approach ensures practical applicability, offering a comprehensive framework for xxi designing robust power electronics-based systems capable of handling complex grid disturbances in modern power networks.