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.

In this article, turboelectric NASA N3-X aircraft is fully electrified for the first time; engines are removed and the all-electric NASA N3-X aircraft electric power system (EPS) is introduced, supplied by four electrochemical energy units (EEUs), including batteries, fuel cells, and supercapacitors. In this regard, three medium-voltage direct current (MVdc), ±5 kVdc, bipolar EPS architectures are proposed for the aircraft and discussed and analyzed in detail by a performing power flow (PF) analysis. The proposed architectures are also considered as three-phase ac, 10 kVac, EPSs and discussed and analyzed in detail for comparison. To perform the PF analysis for the proposed MVdc EPSs, two PF solvers for dc networks under constant power generations and loads are also modified and developed. Potential cable conductors are selected and hints are provided to choose final conductors; to assess the performance of selected conductors, dimensions of the aircraft are estimated and cable parameters are calculated based on the presented dimensions. The proposed EPS architectures meet power system planning criteria under normal condition as well as all n −1 contingencies. This article aims to assess newly designed EPSs and, therefore, assumptions are made about EEUs and propulsion motors to the extent whereby PF analysis is affected.

The increasing interest in employing wide-bandgap (WBG) drive systems has brought about very high power, high-frequency inverters enjoying switching frequencies up to hundreds of kilohertz. However, voltage surges with steep fronts, caused by turning semiconductor switches on/off in inverters, travel through the cable and are reflected at interfaces due to impedance mismatches, giving rise to overvoltages at motor terminals and in motor windings. The phenomena typically associated with these repetitive overvoltages are partial discharges and heating in the insulation system, both of which contribute to insulation system degradation and may lead to premature failures. In this article, taking the mentioned challenges into account, the repetitive transient overvoltage phenomenon in WBG drive systems is evaluated at motor terminals and in motor windings by implementing a precise multiconductor transmission line (MCTL) model in the time domain considering skin and proximity effects. In this regard, first, a finite element method (FEM) analysis is conducted in COMSOL Multiphysics to calculate parasitic elements of the motor; next, the vector fitting approach is employed to properly account for the frequency dependency of calculated elements, and, finally, the model is developed in EMTP-RV to assess the transient overvoltages at motor terminals and in motor windings. As shown, the harshest situation occurs in turns closer to motor terminals and/or turns closer to the neutral point depending on whether the neutral point is grounded or floating, how different phases are connected, and how motor phases are excited by pulse width modulation (PWM) voltages.

Resonant converters are hard nonlinear systems which are comprised of both continuous and discontinuous nonlinearities. Many nonlinear modeling approaches lead to a very awkward, unsystematic stability analysis and controller design. Hence, stability analysis and stabilizing controller design of the popular LLC resonant converter still remain challenging as direct consequences of the absence of a “systematic modeling”. In this paper, the LLC resonant converter is modeled in the form of Piece-Wise Affine (PWA) systems and a Direct Piece-Wise Affine (DPWA) model of the DC-DC LLC resonant converter is proposed. No dynamic is omitted in the modeling approach, and accordingly, the proposed “systematic model” is exact and can be utilized in a precise, systematic stability analysis and controler design. In addition, using the method, no voltage controlled oscillator is needed to control the resonant converter.