DESIGN AND ANALYSIS OF A BI-POLAR LOW VOLTAGE D.C SYSTEM

Abstract

This thesis presents a comprehensive study on the design, analysis, and control of bipolar DC-DC converters tailored for low-voltage DC (LVDC) bipolar distribution systems. Bipolar LVDC systems offer a flexible and efficient means of power distribution, particularly in renewable energy-integrated microgrids. A key challenge in such systems is maintaining voltage balance across the positive and negative rails, which is addressed using specialized bipolar DC-DC converters acting as voltage balancers. The thesis begins with the classification of various bipolar converter topologies, configurations, and interconnections. It then introduces and analyses two main converter designs: the Boost derived and the boost-luo interleaved (NBLI) DC- DC converters. The Boost derived converter is designed as a single-input dual-output topology by interleaving boost stages and buck-boost. Time multiplex regulation strategy presented for independently regulate both output capacitors, maintaining balanced voltages in the bipolar bus. The NBLI converter is designed for high-gain, high-efficiency operation with reduced current ripple and lower stress on switching components. Interleaving improves dynamic response and power density, making it suitable for high-current applications. Furthermore, additional converter topologies including a dual-output buck and buck-boost-based converter, and a boost-SEPIC interleaved converter are explored. These designs offer independent voltage control, minimal component stress, and reduced right-half-plane zero issues, improving overall system reliability. Also, the classification of bipolar DC system with its connection configurations and derived topologies for bipolar operations are presented. Control strategies for each topology are formulated using open-loop and voltage-mode feedback methods. Presented converters effectively enhance voltage balancing, current sharing, and load regulation in bipolar LVDC systems. Overall, the thesis delivers technically robust converter designs and control schemes that improve performance, reliability, and scalability in bipolar LVDC system and the performance of the presented DC-DC converter is verified by the MATLAB/Simulink simulation modal.