High Bandwidth Rogowski Coils, Commutation Loop Stray Inductance, and the Si IGBT and the SiC MOSFET Based Hybrid Concept

Wide bandgap (WBG) semiconductor power devices are attracting increasing attention due to their superior performance across various applications. For accurate measurement of these devices, a current sensor with a minimum bandwidth of 70 MHz is required. This thesis thoroughly explores the design and analysis of both toroidal and solenoidal printed circuit board (PCB) Rogowski coils. The associated parameters of these Rogowski coils are meticulously extracted using ANSYS Q3D Extractor and subsequently measured with the Tektronix TTR500 vector network analyser (VNA). Following this, the thesis presents the design of an op-amp-based integrator, with parameters imported into LTspice for simulation. The bandwidths of the Rogowski coil-integrator assemblies are measured using the VNA, which reveals that the bandwidth of a 10-turn solenoidal PCB Rogowski coil impressively exceeds 300 MHz. Moreover, a comparative analysis of handmade coils and PCB coils is conducted. A relay-based edge generator, designed to facilitate time-domain testing of Rogowski coils, is capable of producing a voltage rise from 10% to 90% in just approximately 6 ns. The Rogowski coil measurement closely correlates with the onboard current measurement, thus confirming the validity and effectiveness of the design approaches presented within this thesis. This thesis also provides a comprehensive introduction to the fundamental aspects of the metal-oxide-semiconductor field-effect transistor (MOSFET) and the insulated-gate bipolar transistor (IGBT), deepening the reader’s understanding of these essential components in power electronics. It then focuses on the current commutation loop inductance, underscoring the importance of minimising this parameter to optimise the design and efficiency of converters and modules, especially when employing WBG power devices in high-speed applications. The thesis introduces various strategies to mitigate loop stray inductance, emphasising the use of compact PCB layouts and laminated bus bars. Additionally, it presents an experimental methodology for extracting loop inductance values, illustrated with a practical example that demonstrates the extraction process. To fully capitalise on the advantages of the Si IGBT’s low conduction loss and the silicon carbide (SiC) MOSFET’s low switching loss, a hybrid parallel connection of a Si IGBT and a SiC MOSFET is proposed. Six gate signal control strategies are introduced and evaluated. The total power loss and device junction temperatures across various load currents and switching frequencies are simulated, investigated and analysed using LTspice and PLECS. For light loads, the SiC MOSFET operates independently. In the case of heavy loads, the Si IGBT takes charge of conduction, while the SiC MOSFET serves as a current bypass to assist in IGBT switching. Simulation results indicate that the hybrid parallel connection can significantly reduce both the total loss and thermal requirements. Moreover, the hybrid parallel connection can also minimise the impact of the freewheeling diode’s (FWD) reverse recovery during the IGBT’s turn-on phase.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2021

Author dc:creator

• Zhang, Tianqi

Advisor dc:contributor.advisor

• Long, Teng

• Commutation loop stray inductance
• Hybrid parallel connection of a Si IGBT and a SiC MOSFET
• IGBT
• Rogowski coil
• SiC MOSFET

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/a08d0d3b-dbe6-4831-be47-6433f1550c44/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.107401

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/366522