PhD Thesis Defence

PhD Defence by Ms. @Little Pradhan 

November 5, 2025, from 12:00 p.m. to 1:00 p.m.

in online mode via GMeet [Meet.Google.com/qek-yjmj-ehm]

Thesis Title: Module Power and Loss Balancing through Carrier-reassignment PWM for a Cascaded H-Bridge Grid-tied Inverter

Abstract: Access to clean, reliable, and affordable energy is vital for global sustainability, yet grid connectivity remains limited in some regions due to geographical and economic barriers.  Renewable energy sources, such as solar and wind, are critical for combating climate change and enabling sustainable transportation, but they are inherently unpredictable. Power electronic systems, particularly multilevel inverters (MLIs) such as the Cascaded H-Bridge (CHB) topology, are crucial for integrating renewables into the grid due to their modularity, scalability, and high-quality waveforms. Conventional level-shifted PWM (LSPWM) causes significant power imbalances in CHB inverters, leading to device stress and premature failure. To address this, three novel carrier-reassignment PWM schemes—Type A, Type B, and Type C—are proposed to enhance power and loss balancing in single-phase grid-connected CHB inverters. These schemes achieve improved power distribution across various power factor conditions, validated through a 9-level and 17-level CHB prototype using closed-loop dq-control in MATLAB/Simulink, Hardware-in-the-Loop (HIL) testing, and PLECS/SPICE thermal models. The results are further verified with a hardware prototype operating in a grid-connected mode. The proposed schemes significantly reduce loss disparities, enhance reliability, and improve power quality compared to conventional methods.