Over voltage protection devices are essential for safeguarding Solid-State Circuit Breakers (SSCBs) against transient overvoltages in applications such as cryogenically - cooled all electric aircraft (AEA) power systems. Despite their significance, their performance under cryogenic conditions remains inadequately characterized. This study experimentally evaluates the behaviour of these devices at ambient (298 K) and cryogenic (77 K) temperatures, focusing on breakdown voltage (VBR), nonlinearity coefficient (α), temperature coefficient (β), and leakage current (Ileak). Using a Keithley 4200A-SCS parameter analyser with I–V sweep configuration, four devices were tested: MOV Metal, MOV Znr, a Schottky diode, and a TVS diode. Results indicate that MOVs exhibit a negative β, with VBRincreasing at 77 K, (e.g., MOV Metal: +9.7%), and a significant rise in leakage current, attributed to carrier freeze-out and defect induced tunnelling. In contrast, Schottky and TVS diodes display a positive β, with VBRdecreasing (Schottky: –17.5%, TVS: –13.2%) and reduced leakage currents, due to enhanced carrier mobility, resulting in improved reliability and device clamping performance. Among the devices investigated, the Schottky diode exhibits the highest sensitivity to temperature variations, yet its performance improves under cryogenic conditions. These findings highlight trade-offs in cryogenic performance, MOVs are faced reliability challenges due to increased leakage, while diodes risk sudden failures due to elevated nonlinearity coefficient. Future work will involve integrating these devices into SSCBs for low-voltage cryogenic applications, ensuring robust overvoltage protection in extreme low-temperature environments.

Switched reluctance motors (SRMs) are highly regarded for their robustness and simplicity; however, they frequently encounter challenges associated with high torque ripple, significantly impacting their overall performance and efficiency. This paper presents a novel power converter specifically engineered to mitigate this issue by substantially reducing torque ripple in SRMs. The proposed converter incorporates a strategically positioned capacitor to enhance negative voltage discharge during the demagnetisation phase, effectively curtailing negative torque generation. Comparative analysis with the Asymmetric Half-Bridge Converter (AHBC) under lower voltage conditions revealed a slightly elevated torque ripple in the proposed converter’s performance. However, at 250V, it demonstrated a notable 10% reduction in torque ripple, with further enhancements of up to 79% observed at 400V. The results of the experiments mirror the results of the simulations, indicating the performance of the converter in enhancing SRM performance and efficiency. This development represents a significant advancement over traditional converter designs, presenting a compelling solution for the wider adoption of SRM technology.

This paper introduces a novel, compact, and adaptable power converter topology tailored for three-phase Switched Reluctance Motors (SRMs). The proposed converter utilizes five switches, five diodes, and two capacitors, the latter specifically incorporated to alleviate voltage spikes and lessen stress imposed on the lower leg switch. This topology can be categorized as a q+2 configuration, where ‘q’ represents the phase count of the SRM. Engineered with automotive applications in mind, the converter offers salient advantages over the conventional Asymmetric Half Bridge Converter (AHBC), including reduced torque ripple, enhanced demagnetization rates, and improved torque to current ratio. The converter is crafted using Silicon Carbide (SiC) MOSFET power transistors and SiC diodes, and its performance is validated using PLECS simulation software. The inherent flexibility and scalability of the proposed converter make it a viable and efficient solution for a broad spectrum of SRM applications.

An emerging network enhancement, Soft Open Points (SOPs), has been investigated to bring flexibility to the overall Low-Voltage (LV) network. The utilization of Power Electronics Devices (PEDs) in the form of SOP accommodates the increases in load and connected distributed generation (DG), meanwhile supporting grid operations with supplementary functionalities. However, owing to its designated operation and unique topology, there are challenging issues in its practical implementation. This paper investigates the ever-challenging Electro-magnetic Compatibility (EMC) issues resulted from the unbalanced operation of SOP. Two novel approaches have been proposed to tackle the issue. The feasibility and performance of the proposed solutions are verified through mathematical derivations and extensive simulation studies.