| PhD Viva

Name of the Speaker: Mr. Surja Sekhar Chakraborty (EE16D203)
Guide: Dr. Kamalesh Hatua
Online meeting link: https://meet.google.com/kew-sybj-vps
Date/Time: 8th December 2023 (Friday), 2:00 PM
Title: Design and Control of Multi-port Isolated DC-DC Series Resonant Converter

Abstract

Isolated bidirectional DC-DC converters are found to be very beneficial for the applications, such as Battery Energy Storage System (BESS), Solid State Transformer (SST), Intelligent Uninterrupted Power Supply (IUPS), and MV drives, due to their high power density and high efficiency. Among the existing eight-switched topologies, Dual Active Bridge Series Resonant Converter (DABSRC) is an attractive choice due to its high efficiency and simple analysis. However, its high frequency (HF) link dynamics are neglected in the existing literature, which increases the RMS and the peak VA rating of the electrical components used in the HF link. In this thesis, an accurate small signal model of the DABSRC is proposed, which predicts the HF link dynamics and helps in control system design. Two different multivariable controllers, such as (1) hierarchical control and (2) state feedback control, are also proposed in order to attain high efficiency over a wide range of loads. In addition to the modeling and control of DABSRC, the design of a high frequency transformer (HFT) is also proposed in this thesis for a Three Port Series Resonant Converter (TPSRC) for on-board charging applications. The proposed transformer achieves zero terminal leakage inductance and naturally decouples the active power flow between the two high frequency links of a TPSRC.

Apart from the two-port and three-port DC-DC power converter, a passive filter design is also proposed in this thesis for a DABSRC based Solid State Transformer (SST). The proposed filter eliminates the double line frequency oscillations present in the HF link current of the DABSRC stage and improves the efficiency of SST.

The proposed modeling and control of DABSRC is verified in a 300V/150V, 2.25kW hardware prototype. On the other hand, a 700V/500V/48V, 2.3kW hardware prototype of TPSRC is developed to verify the design of the proposed three-winding transformer. The proposed passive filter for SST is verified in a 1.65kV/300V, 8kVA hardware prototype.