Global transportation has shifted toward electromobility to achieve net-zero emission, and in the next few decades, commercial electric aircraft is likely to become a reality. This transition has embarked on through the existing more electric aircraft (MEA), and the ultimate goal will be potentially achieved by hybrid-electric and all-electric airliners, along with green fuels, such as green hydrogen or supercritical CO2 (sCO2) and its potential Gg CO2 equivalent elimination—with or without combustion. Electric propulsion replaces conventional jet propulsors with electric fans powered by electric generators rotated by an engine, a combination of generators and energy storage, or just energy storage. An appealing idea is to distribute the electric fans along the aircraft wings or tails to improve aerodynamics, boost energy efficiency, and reduce carbon emissions and acoustic noise. Focusing on distributed electric propulsion (DEP) systems, this article reviews the state-of-the-art advancements in aircraft electrification. Three major DEP categories, i.e., turboelectric, hybrid-electric, and all-electric propulsion technologies, are investigated. Although all of them utilize electric fans as propulsors, their system structures and power generation stages are different. Hence, comprehensive considerations are required to optimize the DEP system designs. Starting with the multifarious electrical system architectures proposed in the literature, a thorough review is conducted including the system parametric specifications, design considerations of power converters, the power electronics devices’ characteristics in cryogenic conditions, and various energy storage systems. This review aims to provide a reference to researchers, engineers, and policy-makers in aviation to accelerate the progress toward future net-zero emissions.

This paper presents the state-of-the-art review of high-conversion high-voltage (HCHV) DC-DC converters for a modern aerial vehicle’s power distribution system. Higher DC bus voltages have become a trend in recent aerial vehicle development because of the potential reduction in size and weight of the rest of the power system and an increase in power density. Some front-end DC energy sources, such as fuel cells, batteries, and supercapacitors, may level at a low-voltage and require HCHV DC-DC converters to integrate with the high-voltage DC bus. On the other hand, high-conversion step-down converters are required between the DC bus and various low-voltage electronic loads. A detailed review of HCHV DC-DC converters for an aviation power distribution system is limited in the literature. This paper presents two main architectures of such converters. Architecture-I employs individual two-port DC-DC converters to link each source to the DC bus, and Architecture-II uses a single multiport converter to connect all the sources to the DC bus. Architecture-I categorizes the two-port DC-DC converter topologies into unidirectional and bidirectional converters, followed by further classifications based on isolation and control schemes. Multiport DC-DC converters for Architecture-II are categorized based on port numbers and then source connection methods. This review investigates multiple topologies within each category or classification, highlighting selected circuit diagrams and their features and shortcomings. The paper presents several insightful comparisons, among various bidirectional converters for Architecture-I, and multiport converters for Architecture-II, for a designer to choose a proper converter. In terms of converter characteristics, this paper focuses on DC voltage gain, power density, efficiency, and reliability, as these qualities are of utmost importance in an aviation application.

Simulation of electric vehicles (EVs) over driving schedules within a fully dynamic EV simulator requires battery models capable of accurately and quickly predicting state of charge (SOC), $I$ – $V$ characteristics, and dynamic behavior of various battery types. An electric battery model utilizing multiple time constants, to address ranges of seconds, minutes, and hours, is developed. The model parameters include open-circuit voltage, series resistance, and equivalent RC circuits, with nonlinear dependence on battery SOC. The SOC captures effects from discharge and charge rate, temperature, and battery cycling. Thermal modeling predicting real-time battery temperature is introduced. One focus of this paper is presenting a systematic and generic methodology for parameter extraction as well as obtaining SOC factors through reasonable test work when evaluating any given lithium-ion (Li-ion), nickel-metal hydride, or lead-acid battery cell. In particular, data sets for a Panasonic CGR18650 Li-ion battery cell are tabulated for direct use. The Li-ion battery model is programmed into a MATLAB/Simulink environment and used as a power source within an existing comprehensive dynamic vehicle simulator. Validation of the Simulink model is through a battery testing apparatus with a hardware-in-the-loop driving schedule that cycles real batteries. Results from simulations and measurements of Li-ion battery packs show that the proposed battery model behaves well and interacts appropriately with other subcomponents of the vehicle simulator.

This article proposes a fixed zone perturb and observe (FZPO) technique to achieve improved steady-state efficiency and a fast and drift-free maximum power point tracking (MPPT) for photovoltaic (PV) systems without any additional sensors. In this technique, the PV array’s power–voltage (P–V) curves are divided into multiple zones with unique zone boundary voltages for different irradiance conditions. This technique employs a combination of adaptive and fixed step sizes to improve the performance, where the adaptive step size is calculated from simple mathematical equations, resulting in a reduced computational burden. Besides, natural drift-free tracking is achieved without any additional sampling or computation, overcoming existing techniques’ limitations. The FZPO technique requires a PV panel’s information only at the initial design stage but not during real-time tracking, making the implementation possible using only low-cost processors. This article presents the implementation and design of the proposed controller. The FZPO technique’s performance is validated through a comprehensive set of hardware experiments on a buck–boost full-bridge (BBFB) converter under various irradiance conditions per the EN50530 standard. For a step change in irradiance, the FZPO technique is experimentally verified to be 42% and 20% more efficient than the conventional and VSS techniques, respectively. During the irradiance varying conditions using the FZPO technique, the peak power loss is one-sixth compared to the conventional and VSS techniques. Practical field-related considerations, such as PV panel temperature effects, are further investigated through experiments.

Wireless power transfer (WPT) has proven to be an effective solution for electric vehicle charging. As two mainstream near-field WPT technologies, inductive and capacitive power transfer (IPT and CPT) have many similarities. This paper aims to explore the remaining opportunities in CPT systems, not yet reported in existing literature, based on duality with the mature IPT technology. First, a generic modeling method based on two-port network theory is proposed, which contributes to unified modeling and analysis for both inductive and capacitive couplings. Then, power transfer mechanism of IPT and CPT couplers is compared, and unified transfer efficiency is derived, promoting CPT theory developments. Last, the duality between existing IPT and CPT circuits is demonstrated in two aspects: compensation circuit configuration and resonant relationship. 14 CPT topologies are derived based on duality with the existing 7 mainstream IPT circuits, of which 11 circuits do not exist in literature, offering future opportunities in CPT. Detailed comparison and evaluation of the derived 14 CPT circuits are conducted, and high-performance circuits are recommended. As a demonstration, a case study of a 2.1kW 3MHz CPT system is implemented in hardware based on the newly proposed M ₁ - SS topology. This example system achieves a peak efficiency of 93.19% with the predicted circuit properties of load-independent constant-voltage (CV) output and zero-phase-angle (ZPA) property.

This article proposes a thermally enhanced reliability modeling framework which works from the mission profile of an electrified aviation propulsion system, incorporating known fault-tolerant power electronics, motor drives, control, and their pre and postfault behaviors. The reliability framework is presented in a hierarchical fashion. Multiphysics modeling is used, incorporating electromechanical states, power losses, and thermal behaviors. The approach includes the device thermal stress in healthy and postfault operating states in the failure rate calculations. Markov chain models are then used with the calculated failure rates to form system level reliability models. A case study of an electric vertical takeoff and landing urban aerial vehicle (eVTOL UAV) walks through the proposed method, modeling multiple versions of the propulsion system, with various levels of fault tolerance and redundancy. The proposed reliability modeling framework captures the operating temperatures and thermal swings seen by the components due to the flight mission, enhancing the failure rate calculation. Further, since the postfault operating mode of the fault tolerant system causes higher component currents and temperatures, different component failure rates are calculated for postfault operation. Finally, the Markov chain modeling allows for a reliability comparison between various UAV propulsion systems, including the effect of combining fault tolerance at the subsystem level, with redundancy at the system level.