Narrow body and wide body aircraft are responsible for more than 75% of aviation greenhouse gas (GHG) emission and aviation, itself, was responsible for about 2.5% of all GHG emissions in the United States in 2018. This situation becomes worse when considering a 4-5% annual growth in air travel. Electrified aircraft is clearly a promising solution to combat the GHG challenge; thus, the trend is to eliminate all but electrical forms of energy in aircraft power distribution systems. However, electrification adds tremendously to the complexity of aircraft electric power systems (EPS), which is dramatically changing in our journey from conventional aircraft to more electric aircraft (MEA) and all electric aircraft (AEA). In this paper, we provide an in-depth discussion on MEA/AEA EPS: electric propulsion, distributed propulsion systems (DPS), EPS voltage levels, power supplies, and EPS architectures are discussed. Publications on power flow (PF) analysis and management of EPS are reviewed, and an initial schematic of a potential aircraft EPS with electric propulsion is proposed. In this regard, we also briefly review the components required for MEA/AEA EPS, including power electronics (PE) converters, electric machines, electrochemical energy units, circuit breakers (CBs), and wiring harness. A comprehensive review of each of the components mentioned above or other topics except for those related to steady state power flow in MEA/AEA EPS is out of this paper’s scope and should be found somewhere else. At the close of the paper, some challenges in the path towards AEA are presented. Unless the discussed challenges are satisfactorily addressed and solved, arriving at an AEA that can properly operate over commercial missions will not be possible.

Even though achieving carbon-free and reduced NOx emission transportation is a prevailing goal, the aviation industry is in its infancy to arrive at passenger class all-electric aircraft (AEA) properly operating over commercial missions. Challenges are mainly associated with the components of the aircraft electric power system (EPS). Considering today’s technologies, power electronics components are not capable to sustain tens of megawatts of required power during the takeoff and meet the aviation limits in terms of size, weight, and cost at the same time. The state-of-the-art electrochemical energy units (EEUs), including battery, fuel cell, and supercapacitor, cannot provide the 25–30-MW thrust power needed for the takeoff, and electrical circuit breakers (CBs) are not able to clear a fault in a large AEA propulsion system, and multimegawatt electric drives/motors can barely be found being able to provide 2–3-MW thrust power, so that they can be employed in a distributed propulsion architecture. Taking mentioned challenges into account, this article aims to tackle challenges associated with protection devices, EEUs, and electric machines in passenger class AEA and present promising solutions using an envisioned medium voltage direct current ±5-kV EPS for an AEA, all-electric NASA N3-X aircraft. Based on findings and discussions made through this article, the authors conclude that although technology advancements are essential in all research areas, high-voltage wide bandgap electrical CBs, Li-air and Li-S batteries with >1000-kW/kg specific power, and multimegawatt superconducting electric machines will turn a commercialized passenger class AEA into reality within the next 20–30 years.

The occurrence of large-scale disturbances is increasing at an alarming rate throughout the world. As a consequence of this trend, a primary concern of today’s power system is to enhance its resilience against low-probability, high-impact events. In this regard, microgrids, as the smart grid’s building blocks, offer promising approaches toward achieving higher levels of distribution system resilience by accommodating and integrating various distributed energy resources. Accordingly, microgrid-based techniques have been the focus of a growing body of research seeking a more resilient power system. These methods mainly rely on the stand-alone operation of microgrids to supply loads locally in case of extreme events. The objective of this paper is to present an updated comprehensive review of the literature on two main categories of microgrid-based resilience enhancement approaches in distribution systems: 1) optimal microgrid formation and 2) optimal microgrid scheduling and energy management. Distinctive from other review papers, this article systematically surveys the research studies under multiple well-sectionalized features, such as various technologies, techniques, models, constraints, and concepts for each of the above two categories. These features include but are not limited to networked microgrids, demand response programs and electric vehicles scheduling, multi-energy microgrids, dynamic optimization schemes, control schemes, communication resilience, hybrid microgrids, and mobile energy resources. Additionally, a comprehensive introduction to resilience definitions and assessment methods, microgrid components, architectures, and control schemes, as well as, sources of uncertainty is provided.

Although the adverse effects of using power electronic conversion on the insulation systems used in different apparatuses have been investigated, they are limited to low slew rates and repetitions. These results cannot be used for next-generation wide bandgap (WBG)-based conversion systems targeted to be fast (with a dv/dt up to 100 kV/ws) and operate at a high switching frequency up to 500 kHz. Frequency and slew rate are two of the most important factors of a voltage pulse, influencing the level of degradation of the insulation systems that are exposed to such voltage pulses. The paper reviews challenges concerning insulation degradation when benefitting from WBG-based conversion systems with the mentioned dv/dt and switching frequency values and identifies technical gaps and future research needs. The paper provides a framework for future research in dielectrics and electrical insulation design for systems under fast, repetitive voltage pluses originated by WBG-based conversion systems.

In recent decades, extensive research has been conducted on the electrification of commercial aircraft to reduce the dependence on mechanical, hydraulic, and pneumatic systems and replace them with electrical systems. A primary goal of this path is to make the power density of the more-/all-electric aircraft (MEA/AEA) closer to that of conventional aircraft. While current commercial aircraft operate at voltages below 1 kV, it is widely accepted that higher operating voltage is necessary for MEA/AEA. NASA has envisaged a voltage level of at least 6 kV for MEA. In the language of electrical insulation technology, higher voltage levels translate into higher electric tension on the insulation system. A serious challenge stems from the fact that, at high altitudes, high-voltage insulation design strategies are not necessarily as efficient as at sea level due to differences in environmental conditions, including lower pressure, higher moisture level, microgravity, and plasma radiation. In this article, challenges associated with the electrical insulation design of future aircraft are reviewed. These challenges extend to almost any part of the electric power system in an aircraft, such as electric machines, power converters, cables, and printed circuit boards (PCBs). An overview of the aging factors, such as internal discharges, arc tracking, and thermal degradation, is accompanied by a discussion of the potential of novel insulating material and the ways to reinforce the current commercial dielectric materials. Finally, considerations for testing at simulated high-altitude conditions and the existing standards and their deficits are investigated.

Increased voltage blocking capability and the development of packaging technology for IGBTs can enhance the local electric field that may become large enough to increase partial discharges (PDs) within the module. The study presents a survey on (i) simulation the electric field within an IGBT module; (ii) current standards for evaluation of the insulation systems of IGBTs; (iii) PD detection and localisation methods as well as other diagnostic and quality control test methods about IGBTs; and (iv) various methods for PD control in an IGBT module. The survey shows remarkable technical gaps in all four areas. More sophisticated numerical and theoretical techniques are needed to model complicated geometries, e.g. extremely sharp edges of the copper metallisation and protrusions in the substrate, and composite non‐linear field grading materials. There is no model to take into account defects in the gel and on the ceramic substrate. IEC 61287‐1 cannot sufficiently assess the behaviour of PDs on IGBT module under the actual operating conditions exposing fast rise pulse‐width modulation‐like voltages. There is no agreement on the exact origin and location of PDs in the module with relying on measured phase‐resolved PD patterns. PD control methods using non‐linear grading materials are not mature enough.