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X-WR-CALDESC:Events for EE
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TZID:Asia/Kolkata
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TZOFFSETFROM:+0530
TZOFFSETTO:+0530
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DTSTART:20230101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20230309T143000
DTEND;TZID=Asia/Kolkata:20230310T043000
DTSTAMP:20260529T022904
CREATED:20230308T225946Z
LAST-MODIFIED:20230309T000550Z
UID:240527-1678372200-1678422600@ee.iisc.ac.in
SUMMARY:Thesis Defense of Shubham Rawat
DESCRIPTION:Title: A Novel Passive Regenerative Snubber for the Phase-Shifted Full-Bridge Converter:  Analysis\, Design and Experimental Verification. \nResearch  Supervisor: Prof. Kaushik Basu \nMeeting Link \n\nAbstract: \nThe development of Wide Bandgap (WBG) devices has enabled power electronic converters to operate at much higher frequencies\, voltages and power. Working at a higher switching frequency minimises the size of magnetics but results in significant switching losses and electromagnetic interference (EMI) noise. Thus\, it necessitates the use of soft-switching techniques to reduce these losses. Phase-Shifted Full-Bridge (PSFB) Converter is the most widely used soft-switching topology in the high-voltage and high-power\, unidirectional DC-DC conversion. The phase shift PWM control utilises the converter parasitic to achieve zero voltage switching (ZVS) turn ON. The gating technique allows the magnetic energy stored in the leakage inductance of the isolation transformer to charge and discharge the output capacitances of the inverter leg. \n\nHowever\, the converter suffers from severe voltage overshoots across the rectifier bridge during the zero to the active state transition. The resonant circuit formed between the transformer leakage inductance and the parasitic diode capacitance of the rectifier is responsible for the high-voltage ringing.  Many passive and active snubbers are presented in the literature to mitigate the high voltage overshoots across the diode bridge. While passive snubbers are relatively simple to implement than active snubbers\, they are lossy. On the other hand\, the active snubbers require additional gate driver circuitry and complex control. \nThe first part of the thesis proposes a novel passive regenerative snubber to overcome the mentioned drawbacks of the existing snubbers. The proposed snubber is ideally lossless with no control complexity. The work covers a detailed analysis of the PSFB operation with the proposed snubber while obtaining closed-form expressions for the converter state variables at the end of each topological stage. The study considers all the major converter parasitic\, such as transformer leakage and magnetising inductances\, and parasitic capacitances of the converter. Given the new snubber\, the thesis also lays out a step-by-step PSFB design procedure utilising the analysis carried out in the first part of the work. The design aimed to develop a 100 kHz PSFB for an input voltage of 360-400 V and the output power range of 0.5-1.5 kW at a fixed output voltage of 48 V. The design approach focuses on the two design objectives. All inverter switches must achieve ZVS turn ON\, and the converter gain must achieve the necessary gain to maintain desired constant output voltage for all possible operating conditions. \nA hardware prototype is built and tested as per the given specification. The experimental results validate the effectiveness of the snubber in reducing the voltage overshoot. Further\, the analysis and design accuracy is verified using the measured state variables. Finally\, the work presents the overall efficiency and the loss distribution among the converter components.
URL:https://ee.iisc.ac.in/event/thesis-defense-of-shubham-rawat/
LOCATION:Online\, India
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20230310T163000
DTEND;TZID=Asia/Kolkata:20230313T183000
DTSTAMP:20260529T022904
CREATED:20230309T234144Z
LAST-MODIFIED:20230309T234240Z
UID:240537-1678465800-1678732200@ee.iisc.ac.in
SUMMARY:MTech (Research) Colloquium of Vishwabandhu Uttam
DESCRIPTION:Title: A Unified Modeling Approach for Design and Performance Improvement of Triple Active Bridge Converter\n\nResearch Supervisor: Vishnu Mahadeva Iyer\n\n Meeting link\n\nAbstract:Triple Active Bridge (TAB) converter is a multi-port DC-DC converter. This converter is an extension of the popular Dual Active Bridge converter. It features desirable traits of the DAB converter\, such as high power density\, galvanic isolation\, and bi-directional power flow between any of the ports. As in other multi-port converters\, redundant power conversion is minimized through component sharing among the ports in a TAB converter. All the switches in a TAB converter can undergo soft-switching over a wide range of operating points\, reducing switching losses and the size of auxiliary components. The multiple degrees of freedom in modulating a TAB converter offer several design and operational flexibilities.However\, this converter has yet to come into the limelight despite these advantages. One of the reasons is the lack of a unified analytical framework for the design and operation of this converter. The existing models for the TAB converter are limited in scope and cannot be easily used for the design and operational optimization of the converter. This work focuses on developing simple\, unified models for analyzing the TAB converter.Firstly\, the popular Fundamental Harmonic Approximated (FHA) large-signal and small-signal models are evaluated to understand their limitations. Improved large-signal and small-signal Generalised Harmonic Models (GHM) are developed by incorporating the impact of higher-order harmonics. While the GHM is shown to be superior for small-signal analysis of the converter\, it is not suitable to analyze the soft-switching bounds of the TAB converter. To overcome the limitations of GHM\, a Unified Model that incorporates the impact of the magnetising inductance of the three-winding transformer is proposed. The Unified Model can accurately predict the AC port currents at the switching instants and is used to study the soft-switching bounds of the TAB converter. The GHM and Unified Model are validated through extensive switching circuit simulations and experimental results from a 1 kW hardware prototype developed in the laboratory.Further\, a new design algorithm for the TAB converter is proposed. The proposed algorithm leverages the FHA model’s simplicity and the Unified Model’s accuracy. Finally\, a new modulation scheme based on Penta Phase Shift with five degrees of freedom is proposed to achieve soft-switching across the operational range of the TAB converter.\nWe request your presence at the colloquium.\nAll are welcome.
URL:https://ee.iisc.ac.in/event/mtech-research-colloquium-of-vishwabandhu-uttam/
LOCATION:EE\, MMCR
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