Title:  Soft-Switching Solid-State Transformer for Traction Applications

Committee:

Dr. Maryam Saeedifard, ECE, Chair , Advisor

Dr. Deepak Divan, ECE, Co-Advisor

Dr. Sakis Meliopoulos, ECE

Dr. Lukas Graber, ECE

Dr. Daniel Molzahn, ECE

Dr. Jiangchao Qin, Arizona State

Abstract: In the next-generation traction converters, instead of using a low-frequency transformer to interface with medium voltage AC grid, medium frequency transformer-based converters are used. The proposed research is to design and control a modular soft-switching solid-state transformer (M-S4T), which is a promising candidate for the next-generation traction converters. In the proposed research, a 3.3 kV reverse-blocking (RB) device, one of the key components in the M-S4T, is fully characterized. A unique voltage sharing phenomenon within the RB device is analyzed. The use of RB device for current-sourced converters (CSCs) under zero-voltage-switching (ZVS) condition is provided.  In addition, a decoupled quasi-real-time (QRT) model of the M-S4T is proposed for hardware-in-loop (HIL) simulation and the accuracy of the QRT model is verified experimentally. To control the M-S4T, a control architecture for synchronization and communication between each modules is proposed and the proposed control architecture is verified by HIL simulation and experiment. In addition, the design considerations of system level parameters of the M-S4T are investigated.