Date of Graduation

8-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Mantooth, H. Alan

Committee Member

Zhao, Yue

Second Committee Member

Chen, Zhong

Third Committee Member

Huitink, David

Keywords

Magnetic current sensor; Power electronics; Rogowski coil current sensor; Switching current measurement; Wide bandgap devices

Abstract

Accurate switching current measurement plays a pivotal role in characterization of power devices, overcurrent protection, and real-time control of system-level operations in power electronics applications. However, the ongoing revolution in power electronics, driven by the emergence of wide bandgap power devices operating at megahertz (MHz) switching frequencies, introduces challenges for current sensor design. The urgent issue now is the need to increase current sensor bandwidth significantly to adeptly capture the rapid switching speed current. Additionally, the trend towards high power density and compact power converters in various applications demands current sensors that are not only compact and nonintrusive but can also be seamlessly integrated into existing power systems. Currently, all the commercial current sensors fall short of incorporating all these essential features. This dissertation presents a high-bandwidth Ω-shaped current sensor, consisting of an Ω-shaped copper tube, Rogowski coil and an external integrator, to achieve precise switching current measurement. The designed structure allows easy integration into various current paths. And a multi-objective optimization based on a genetic algorithm and a finite element method is developed for the comprehensive design of the Rogowski coil. Subsequently, three optimized solutions of coil geometry with bandwidth and sensitivity as optimization objectives are selected for comparison. Moreover, an external differential integrator and its associated design guide are introduced. Finally, comprehensive double pulse tests (DPT) and multi-pulse test are performed under 800 V/70 A, 400V/170A conditions. The test results of the three distinct coils validate the effectiveness of the proposed automated optimization methodology and external integrator design. The Ω-shaped current sensor consistently exhibits a faster response and maintains over 10 mV/A sensitivity compared with a 30 MHz commercial Rogowski coil.

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