Inductive interconnecting solutions for airworthiness standards and power-quality requirements compliance for more-electric aircraft/engine power networks

Driven by efficiency benefits, performance optimization and reduced fuel-burn, the aviation industry has witnessed a technological shift towards the broader electrification of on-board systems, known as the More-Electric Aircraft (MEA) concept. Electrical systems are now responsible for functions that previously required mechanical, hydraulic or pneumatic power sources, with a subset of these functions being critical or essential to the continuity and safety of the flight.;This trend of incremental electrification has brought along benefits such as reductions in weight and volume, performance optimization and reduced life-cycle costs for the aircraft operator. It has however also increased the necessary engine power offtake and has made the electrical networks of modern MEA larger and more complex. In pursuit of new, more efficient electrical architectures, paralleled or interconnected generation is thought to be one platform towards improved performance and fuel savings.;However, the paralleling of multiple generation sources across the aircraft can breach current design and certification rules under fault conditions. This thesis proposes and evaluates candidate interconnecting solutions to minimize the propagation of transients across the interconnected network and demonstrates their effectiveness with reference to current airworthiness standards and MIL-STD-704F power quality requirements.;It demonstrates that inductive interconnections may achieve compliance with these requirements and quantifies the estimated mass penalty incurred on the electrical architecture, highlighting how architectural and operating strategies can influence design options at a systems level. By examining the impact of protection operation speed on the electrical network, it determines that fast fault protection is a key enabling technology towards implementing lightweight and compliant interconnected architectures.;Lastly, this thesis addresses potential implications arising from alternate standards interpretations within the framework of interconnected networks and demonstrates the impact of regulatory changes on the electrical architecture and interconnecting solutions.Driven by efficiency benefits, performance optimization and reduced fuel-burn, the aviation industry has witnessed a technological shift towards the broader electrification of on-board systems, known as the More-Electric Aircraft (MEA) concept. Electrical systems are now responsible for functions that previously required mechanical, hydraulic or pneumatic power sources, with a subset of these functions being critical or essential to the continuity and safety of the flight.;This trend of incremental electrification has brought along benefits such as reductions in weight and volume, performance optimization and reduced life-cycle costs for the aircraft operator. It has however also increased the necessary engine power offtake and has made the electrical networks of modern MEA larger and more complex. In pursuit of new, more efficient electrical architectures, paralleled or interconnected generation is thought to be one platform towards improved performance and fuel savings.;However, the paralleling of multiple generation sources across the aircraft can breach current design and certification rules under fault conditions. This thesis proposes and evaluates candidate interconnecting solutions to minimize the propagation of transients across the interconnected network and demonstrates their effectiveness with reference to current airworthiness standards and MIL-STD-704F power quality requirements.;It demonstrates that inductive interconnections may achieve compliance with these requirements and quantifies the estimated mass penalty incurred on the electrical architecture, highlighting how architectural and operating strategies can influence design options at a systems level. By examining the impact of protection operation speed on the electrical network, it determines that fast fault protection is a key enabling technology towards implementing lightweight and compliant interconnected architectures.;Lastly, this thesis addresses potential implications arising from alternate standards interpretations within the framework of interconnected networks and demonstrates the impact of regulatory changes on the electrical architecture and interconnecting solutions

Development of a current limiting solid-state circuit breaker based on wide-band gap power semiconductor devices for 400V DC microgrid protection

Popularity of DC distribution systems is increasing for many residential and industrial applications such as data centres, commercial and residential buildings, telecommunication systems, and transport power networks etc. Compared to AC systems, they have demonstrated higher power efficiency, less complexity, and more readiness of integrating with various local power sources and DC electronic loads. However, one of the major technical issues hindering this trend is the lack of effective DC fault protection devices/circuits. Although conventional electromechanical circuit breakers work well in AC systems, they are not suitable for DC systems due to their long response time (ranging from tens of milliseconds to hundreds of milliseconds). Such a long response time is far beyond the withstand time (typically tens of microseconds) of most power electronic devices in short-circuit operating conditions. In contrast, Solid-State Circuit Breakers (SSCBs) are able to offer ultrafast switching speed thanks to the modern power semiconductor devices which can turn off in microseconds or even in tens of nanoseconds. Furthermore, the ever-increasing fault current level in DC systems poses a significant mechanical and thermal stress on the whole DC system. Therefore, the desire for the protection devices with the feature of fast switching speed along with the current-limiting capability has prompted intensive research in this area over the last decade in both academia and industry. However, the relatively high conduction losses and limited short-circuit capability are two of the major drawbacks of SSCBs. With the growing maturity and increasingly commercial availability of Wide-Bandgap (WBG) semiconductor devices, a SSCB based-on WBG devices is a promising solution to alleviate the issues since WBG semiconductors have demonstrated superior material properties over the conventional silicon material such as lower specific on-resistance, higher junction temperatures and higher breakdown voltage. This research aims to design and develop a WBG-based solid-state circuit breaker for a 400V DC microgrid application. To accomplish this task, this work starts with a comprehensive review of DC microgrid technology followed by an extensive review of the state-of-the-art DC circuit breakers. Then, to develop a circuit topology for the proposed SSCB, a practical current limiter is analysed, simulated, and evaluated. Based on this topology, the proposed SSCB is configured with a high-voltage normally-on Silicon Carbide Junction Field Effect Transistors (SiC-JFETs) cascading a low-voltage normally-off power MOSFET. This solution offers several advantages. For example, it does not require any additional sensing and tripping circuitry for short-circuit protection and therefore has a fast response speed. Meanwhile, the use of power SiC JFETs tends to reduce the conduction losses and enhance the short-circuit robustness of SSCBs. In addition, it offers the feature of current limiting which could ease the thermal and mechanical stresses on the whole DC system. The operating process of the proposed SSCB is analysed and the analytical results are compared with the simulated results; In the end, a prototype SSCB has been built and evaluated for short-circuit protection in a 400V DC system. In addition, to effectively suppress the overvoltage at the turn-off of SSCBs, a novel hybrid snubber circuit has been proposed by taking into account the advantages offered by both conventional Resistor-Capacitor-Diode (RCD) snubbers and Metal-Oxide Varistors (MOVs). Finally, other functions of the proposed SSCBs including overload protection, over temperature protection and protection coordination have been investigated and some operating issues such as false tripping and SSCB reset have been addressed