DESIGN AND ANALYSIS OF A CASCADED HIGH-GAIN BOOST-BUCK CONVERTER FOR BATTERY CHARGING APPLICATIONS

Abstract

This project presents detailed analysis on the design, analysis and regulation of two stage dc-dc conversion system intended for application in energy harvesting and high power battery charging system. The developed system utilizes High-Gain Boost converter and subsequently the Buck converter that efficiently converts the low voltage dc power generated from sources like PV or fuel cells and produces regulated dc outputs that can be utilized for charging applications. The primary objective of the proposed work is to achieve high voltage gain, maintain a constant and stable DC-Link voltage, and utilize this DC-Link output as the input to a cascaded buck converter for efficient battery charging applications. The thesis commences with the execution of a non isolated, non-coupled inductor-based high-gain DC-DC boost converter topology intended to increase variable low-input DC voltage to a stable 300 V DC-link. The novel boost converter employs two switches controlled by a single Pulse Width Modulator (PWM), this configuration makes the converter a compact economical and lightweight design with an uncomplicated control architecture. The converter is engineered to deliver a significant voltage gain at reduced duty cycles while ensuring minimal voltage stress across each switch during switching. Its operation facilitates significant voltage amplification, making it highly suitable for the use in renewable energy systems where efficient low-to-high voltage conversion is required. The novel boost converter exhibits an enhanced gain characteristics and also improved efficiency compared to the conventional boost converter, thus improving overall system reliability and performance. Following the boost conversion process, the regulated 300V DC-link works as the input to the Buck converter which will buck the DC-link voltage to a regulated 48V level suitable for the 1kW battery charger output ensuring accuracy of voltage and current at the output. The objective of this step is to provide safe and consistent charging operation for varied loads and varying sources. The boost buck topology provides the most effective conversion and regulation process for modern day charging facilities, DC microgrids and renewable energy storage systems. Controller designs for both converters have been developed by employing PI controller based feedback approach to stabilize the DC-Link voltage in case of Boost converter and to provide a regulated output voltage and current in case of the Buck converter. The control design provides a very good dynamic performance, high efficiency operation, high voltage gain, minimum switch stresses and resilience under input and load variation. By cascading these two stages the system would attain high power conversion and energy transfer capabilities. The current research work focuses on developing technically advanced converter topology by combining a high voltage gain process and a high efficiency conversion technique for renewable energy applications,with the efficacy of the given converter system validated through comprehensive MATLAB/Simulink simulation study.