Thesis Defense – Ahmed Aljabi (MSEE)

Ahmed Aljabi – M.Sc. in Electrical & Electronics Engineering

Prof. H. Fatih Uğurdağ – Advisor

Dr. Hamza Makhamreh – Co-Advisor

Date: 14.05.2025

Time: 10:00

Location: AB1- 413

“POWER CONVERSION IN MULTILEVEL CONVERTERS: DESIGN, CONTROL, AND APPLICATION OF SPLIT-SOURCE PUC5 AND BI6 TOPOLOGIES”

Prof. Dr. H. Fatih Uğurdağ, Özyeğin University

Prof. Dr. Mehmet Timur Aydemir, Kadir Has University

Assist. Prof. Dr. Göktürk Poyrazoğlu, Özyeğin University

Abstract:

This thesis explores novel single-stage multilevel inverter topologies aimed at reducing system complexity while maintaining high performance. A key contribution is the development of a grid-connected single-stage inverter that integrates features from both the five-level packed U-cell (PUC5) and split-source inverter (SSI) topologies. The design achieves voltage boosting using only three additional passive components—an inductor, a capacitor, and a diode—thus eliminating the need for a separate DC-DC converter. It also preserves the sensorless voltage balancing capability for the flying capacitor from the original PUC5 topology. Another focus is the application of the boost inverter 6 (BI6) topology as a PV microinverter, enhanced by a front-end boost converter to improve voltage gain and enable maximum power point tracking (MPPT). A fixed BI6 duty cycle is employed, while the modulation index and boost converter duty cycle are regulated by current and MPPT controllers, respectively. In addition, a fixed-frequency sliding-mode controller (SMC) is developed for the BI6 topology. A control strategy is introduced to decouple voltage boosting from AC output control, and the controller combines a PI loop for DC bus regulation with an SMC for the AC output. Both simulation and experimental results validate the performance of the proposed controller.

Bio:

Ahmed Aljabi received his B.Sc. degree in Electrical and Electronics Engineering from Özyeğin University in 2022, where he is currently pursuing his M.Sc. degree. His research focuses on advanced power converter topologies and their control, particularly single-stage boost and multilevel inverter topologies, with an emphasis on their applications in renewable energy systems. He has published two conference papers at IECON 2024 and CPE-POWERENG 2025 and is currently preparing a journal manuscript.