More Electric Aircraft Research Articles

Accelerated and Adaptive Power Scheduling for More Electric Aircraft Via Hybrid Learning

In recent studies, the power scheduling in more electric aircraft (MEA) has been formulated as a mixed-integer quadratic programming problem. Many model-driven methods, such as branch-and-bound algorithms, are advocated to solve it. However, these methods are often prone to considerably high complexities, which makes real-time processing a problem. In this article, a two-stage hybrid learning-based optimization approach is proposed to address this challenging issue. In the first stage, the task of optimizing integer variables is considered as a multilabel classification problem, which is solved by a data-driven method, i.e., ensemble deep neural networks (EDNNs). In the second stage, with the obtained integer solutions, the problem is transformed into a quadratic programming problem that can be quickly solved by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">model-driven</i> numerical optimization methods. Compared to the state-of-the-art power scheduling algorithms, the model-driven and data-driven methods can compensate each other so that this two-stage hybrid learning-based approach can achieve orders of magnitude speedup in computational time, while guaranteeing the optimal scheduling performance. The structures of EDNNs are well designed so that the proposed approach can adapt to varying operating conditions in MEA. An offline simulation test and an online hardware-in-the-loop test validate the above advantages of the proposed approach.

Finite-time tracking control with fast reaching condition for disturbed more electric aircraft direct current microgrid with constant power loads

Future more electric aircraft (MEA) can be seen as a direct current microgrid (DC MG). While DC MG can generally achieve safe, efficient and reliable operation of the system, constant power loads (CPLs), unknown resistive loads, DC source voltage variations, and disturbance inputs might degrade the overall stability and performance if they are not compensated in the control design procedure. In this paper, a fast-reaching condition-based sliding mode control (SMC) is proposed for the DC MG. The fast-reaching law contains two terms that improve the transient performance by forcing the system states to reach a sliding surface with two different rates. This attribute enhances the speed of convergence of the states to the sliding surface compared to conventional SMC. Additionally, the suggested method is resilient to system parameter uncertainties, which is indispensable in practice. The proposed controller is implemented to a DC MG that is supplied by an uncertain DC source and feeds CPLs and resistive load with time-varying power and resistance. OPAL RT results illustrate the robustness and fast convergence of the planned SMC controller.

Multi-Source Dual Active Bridge DC/DC Converter for More Electric Aircraft

The topology proposed in this paper aims for a multiple sources/loads integration to improve the power density of the electrical power distribution system (EPDS) of the more-electric aircraft (MEA) architecture. The different operating modes of the proposed topology add flexibility to the system enabling power flow between different sources, while controlling the power supplied to the low voltage (LV) network on the aircraft. Better system utilization is achieved as compared to conventional solutions. The system stability is improved considering that the multi-source DAB (MSDAB) topology can be configured to stabilize the high-voltage DC (HVDC) bus in case of voltage sag. A battery charging configuration utilizing the magnetizing inductance of the transformer is proposed and discussed as one of the operating modes of the converter. The power flow to the low-voltage bus network is controlled by phase shifting the gating signals between the two bridges. A design process using genetic algorithm (GA) optimization is introduced to optimally select the converter parameters to minimize the transformer RMS current. Simulation and experiments of the control schemes were performed to validate optimal operation of the proposed converter.

A two-stage bidirectional DC-DC converter system and its control strategy

With the development of more-electric aircrafts, bidirectional DC-DC converter has been widely used in this field. In order to improve the voltage regulation range and stability of the bidirectional DC-DC converter system, a two-stage bidirectional DC-DC converter with some operation modes is used and analyzed in this paper. The converter is composed of a four-switch buck-boost circuit and an isolated CLLC resonant circuit, where all MOSFETs can realize soft switching action. The four-switch buck-boost circuit regulates the output voltage in a certain range through the duty cycle control, and the CLLC resonant circuit can control the output voltage by changing its switching frequency, where the two-stage bidirectional DC-DC converter adopts voltage closed-loop control strategy to realize the stable voltage output. Due to the existence of the intermediate part conversion voltage, the converter has three-port network characteristics, which makes it applicable to the working occasions with multiple voltage levels. The feasibility of this two-stage bidirectional DC-DC converter system combined with control strategy and its three-port operation used for more-electric aircraft power system are verified by simulation analysis.

Design Space Analysis of the Dual-Active-Bridge Converter for More Electric Aircraft

In the literature, different DC/DC power electronic converters (PECs) have been found to interconnect high-voltage DC and low-voltage DC grids in the electric power distribution networks of aircraft. In this scenario, the dual-active-bridge (DAB) converter has been shown to be one of the most promising topologies. The main disadvantages of this PEC are the large output capacitance required to satisfy more electric aircraft (MEA) requirements and the high conduction losses produced in low-voltage power devices of (LV). Therefore, this paper proposes analytical models to determine the voltage ripple and root-mean-square (RMS) current in DC bus capacitors of DABs considering different modulation strategies. Moreover, an analysis of the design space in an MEA case study is performed to evaluate the influence of the design variables in power losses of power devices and peak-to-peak voltage ripple in DC bus capacitors. These models are useful for the design stage of this PEC, as well as to enable multi-objective optimization procedures by reducing the computational cost of these methodologies. Furthermore, the exploration of the switching frequency and limit of the modulation angle aid in reducing the resulting volume of the low-voltage DC capacitor.

An improved energy management strategy for fuel cell/battery/supercapacitor system using a novel hybrid jellyfish/particle swarm/BAT optimizers

In this paper, a fuel cell (FC) hybrid emergency system is presented. It contains fuel cells, batteries, and supercapacitors which are effective for different conveyance applications. Abbreviating the hydrogen consumption and incrementing the lifetime of power sources are the key factors of each energy management strategy (EMS). An incipient proposed EMS depending on an optimized proportional-integral (PI) controller is presented considering FC efficiency to ensure the operation of the FC stack within its maximum efficiency region and reduce the stress on it which in turn leads to reducing its hydrogen consumption. Regarding tunning the PI controller gains (Kp,Ki), a proposed hybrid metaheuristic optimization technique named JSPSOBAT has been presented which merges jellyfish (JS) optimizer, particle swarm optimizer (PSO) and BAT optimizer to achieve the balance between exploration and exploitation phases. To firstly validate the effectiveness of the JSPSOBAT technique, a comparative study with other single and hybrid metaheuristic optimization techniques is presented by testing on 50 complex benchmark functions. Then, the JSPSOBAT is used to select the controller gains of the proposed PI controller. A 30 min load profile of a More Electric Aircraft (MEA) is used. The performance of the proposed EMS using the proposed optimization technique is compared with other EMS such as state machine control strategy, classical PI control strategy, equivalent consumption minimization strategy, external energy maximization strategy, and the results show that the proposed technique produces the best performance.

Component-Level Modeling of More Electric Auxiliary Power Units for Cooperative Control

Today, the more electric aircraft (MEA) concept is gaining tremendous popularity. As a key component of the MEA, a more electric auxiliary power unit (MEAPU) integrated model with high accuracy and real-time performance is essential when conducting cooperative control and hardware-in-the-loop (HIL) test research. This paper proposes a novel MEAPU integrated model consisting of a MEAPU component-level-model (CLM) and a starter-generator (SG) model. Firstly, a MEAPU CLM was built and a continuous scaling method for the component characteristic map in the CLM is proposed to improve the model’s accuracy. Then, a double winding induction starter-generator (DWISG) model based on the electromagnetic theory, which is quite time consuming, was simplified using the pulse width modulation (PWM) rectifier linearization method. Finally, considering the coupling relationship between the MEAPU CLM and DWISG, an accurate real-time MEAPU integrated model was built and its simulation results were analyzed. Compared with the test results, the error of the proposed model was less than 0.5%; meanwhile its single-step simulation time was less than 20 ms, which can meet the demands of cooperative control and HIL test research. Furthermore, the continuous scaling method and PWM rectifier linearization method were found to be effective for modeling other MEAPUs and more electric engines (MEE).

Efficiency Focused Energy Management Strategy Based on Optimal Droop Gain Design for More Electric Aircraft

Due to the substantial increase in the number of electrically driven systems onboard more electric aircraft (MEA), the onboard electric power systems (EPSs) are becoming more and more complex. Therefore, there is a need to develop a control strategy to manage the overall EPS energy flow and ensure the operation of safety-critical systems (which are electrical loads) under different operating scenarios and to consider EPS losses minimization, exploiting the thermal capability of generators, different load priorities, and available batteries with their charging and discharging schedules. This article presents an energy management (EM) strategy that considers the aforementioned objectives. The optimal droop gain approach is employed as a power-sharing method to minimize the total EPS losses in MEA. A finite state machine (FSM) has been used to implement the control strategy to realize the EPS reconfiguration operation. The proposed EM strategy is implemented and simulated using MATLAB/Simulink and hardware-in-the-loop (HIL) under different operational scenarios, such as normal operations, failure of one of the power generation channels, and failure of all power generation channels. The proposed EM method has shown its capability to efficiently manage the EPS under different operating conditions to reduce the overall system losses.

Analysis of SiC and SiC-Cascode MOSFET in the design of power electronics converters for more electric aircrafts

&lt;span&gt;Wideband gap (WBG) semiconductors have developed rapidly in recent years, enabling greater efficiency and power density in the design of power electronics converters for several areas of application. In this sense, this work analyzes the efficiency and specificities of silicon carbide (SiC) technologies and their cascode topology (SiC-Cascode), operating at high switching frequencies. The analyzes are performed using a Boost converter designed for conversion systems in the more-electric aircraft (MEA) context, where the alternating current (AC) power systems can operate at fixed frequency (115V/400Hz), or at variable frequency (115V/360-800Hz), such as observe in Boeing 787, and the direct current (DC) power system can operate with a DC bus of 400 V and +/-270 V are normally used. To validate the project, computer simulations were performed and a 1.0kW prototype was built in the laboratory. The performance analyses demonstrates that 97.5% of efficiency is achieved at 500 kHz switching frequency.&lt;/span&gt;

Design and Demonstration of a 100 kW High-Frequency Matrix Core Transformer for More Electric Aircraft Power Distribution

The rapid development of more electric aircraft (MEA) raises the demand for high-power converters with significant weight and volume reduction for onboard power distribution. The isolated dc/dc converter using the medium-frequency transformer (MFT) is a feasible solution. To design an MFT with improved electromagnetic and thermal performance, a matrix core transformer (MCT) architecture is proposed with accurate models in this article. With superior heat dissipation ability, the high current windings can be effectively cooled with both natural and forced air convection. In addition, an optimization methodology for MCT design is presented. As a result, the prototype of a 100-kW, 50-kHz MCT with an additive manufactured bobbin is built. The results of both finite element analysis (FEA) simulation and experimental study in a full power dual active bridge (DAB) with the MCT prototype are presented to verify the theoretical design. The power density and efficiency of the MCT reach 17.7 kW/L and 99.63%, respectively.

Aircraft Distributed Electric Propulsion Technologies—A Review

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.

A Low Inductance, High Power Density 3L-TNPC Power Module for More-Electric Aircraft Applications

Three-level T-type neutral-point-clamped converters (3L-TNPCs) are widely used in propulsion converters in more-electric aircraft (MEA) applications as higher efficiency, improved output total harmonic distortion (THD), and lower common-mode noise. However, such topology suffers from high stray inductance because of complicated power loop. Its power module current density is also less than the two-level (2L) converter as the increased switch counts. To solve the issue, this article proposes a novel hybrid-structure-based full SiC-MOSFET 3L-TNPC power module. The module has a printed circuit board (PCB) stacked on top of the substrate, with bare dies soldered on direct bond copper (DBC) and connected to PCB by bonding wires. Such a structure allows the power loop on both the substrate and PCB. This reduces the stray inductance by enhanced mutual inductance cancellation. The heat from dies can be directly dissipated through the substrate and the proposed base-plate-embedded cooling system, enhancing thermal conductivity by 55%. Based on the structure, a 1.2-kV, 300-A 3L-TNPC module is fabricated with a stray inductance of 2.5 nH. Because the stray inductance is 68% smaller than a state-of-the-art module, faster driving speeds can be used with limited voltage overshoots. As a result, the switching loss of the module is reduced by 62.5% compared with the same bare die at a state-of-the-art module’s power loop at 800 V, 450 A. Eventually, impedance characterization by impedance analyzer, double-pulse tests, and continuous tests are performed for experiment evaluation.

An Advanced Switching Harmonic Cancellation Method for a Dual-Generator Power System in More-Electric Aircraft

Dual-generator power systems have attracted increased attention in recent years as it can significantly reduce the fuel assumption of aircraft engines allowing power transfer between different engine shafts. In such a system, two generators supply a common dc bus together. A dc-bus capacitor is required to filter switching harmonics to ensure that the dc-bus voltage satisfies the MIL-STD-704F standard. Due to the high current rating, this capacitor is normally bulky and heavy. This article aims to introduce a switching harmonic cancellation method, which can effectively reduce harmonics at the dc bus. This, in return, will extend the lifetime and reduce the weight of the dc-bus capacitor. With the assumption that power converters connected to the dc bus are modulated with the commonly used space vector pulsewidth modulation (SVPWM) technique, a simplified mathematical model to estimate both first and second switching harmonics is developed. Based on the proposed models, an advanced method of switching harmonic cancellation scheme is proposed through an adaptive phase shift of carrier signals for different power outputs of converters. Both simulation and experimental results are used to validate the proposed model and the suppression method.

Capacitor Energy-Based Current Sharing Control for More-Electric-Aircraft Onboard Microgrids With Parallel Sources

A current-sharing (CS) strategy based on capacitor energy control (CEC) is proposed for more-electric-aircraft (MEA) onboard microgrids with parallel sources. In conventional sources, the reference value is the dc-link voltage, which can be corrected based on the error between the output and the average current to realize CS. However, since the source characteristics are different, each source needs a proportion-integration-differentiation (PID) controller for CS control. In the CEC-based source, the reference value is the energy stored in the dc-link capacitor. The CEC calculates the reference output current, which is the input value of the field current controller. In the proposed CS control, the reference output current is corrected by the error between the output current and the average current. Since the current values are directly added up, differences between sources are eliminated. Fewer controllers are needed and the scheme is simplified. The dynamic performance and adaptability to operating condition variations are optimized. The CS error is low and dynamic responses are accelerated. A 270- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\mathrm {dc}}$ </tex-math></inline-formula> microgrid with parallel-connected doubly salient electromagnetic generators (DSEGs) is investigated and implemented. The CEC CS control and the conventional method are compared. The CS error, dynamic responses during connection, disconnection, speed variation, and load variation are investigated. The optimized performances of the CEC CS method are verified by experimental results.

Review of DC Series Arc Fault Testing Methods and Capability Assessment of Test Platforms for More-Electric Aircraft

In the new era of increasingly electric aircraft, the need for reliable and safe electrical systems is more important than ever. In addition, the wide-scale adoption of dc distribution is considered a key enabling technology for more efficient aircraft operation. In this context, arc fault detection devices (AFDDs) have become a topic of interest for the aviation industry with ongoing research to characterize the impact and adequately protect against severe dc series arc faults. Although dc arc faults have been widely investigated for utility applications (such as solar photovoltaic systems), direct adoption of current practices for validating arc detection devices is not straightforward due to the distinct aircraft operating environment. This article provides a first-of-its-kind landscaping exercise of published series arc fault testing based on factors associated with aircraft applications that have the potential to influence the arc characteristics. In addition, an appraisal and associated gap analysis of published arc test platforms is undertaken in order to assess their suitability to support in-depth testing of the impact and mitigation of series arcs within future aircraft dc electrical systems and identify future testing needs, in particular, to better facilitate a comprehensive performance validation of new AFDDs.

Active Disturbance Rejection Control of DC-Bus Voltages Within a High-Speed Aircraft Electric Starter/Generator System

Wide-speed range operation capabilities in both motoring and generation modes are essential for an aircraft electrical starter/generator (ESG) drive system for more-electric aircraft applications. When running as a generator, the ESG is supplying power to the main HVdc bus within the onboard electrical system. A fast and robust dc bus voltage would be beneficial to electrical loads connected to it. In this article, an active disturbance rejection control (ADRC) is proposed to realize a fast and robust regulation of onboard dc bus voltages. The ADRC is achieved with a second-order extended state observer (ESO) to generate torque reference for the ESG. All the key characteristics, such as the stability of ESO, dc voltage tracking performance, and disturbance rejection capability of the ADRC for aircraft ESG applications, are thoroughly analyzed. To enhance system stabilities, an innovative and simple design method for the ADRC and ESO gains is introduced based on the gain-margin and phase-margin criteria. Experimental results have shown that, compared with the conventional PI-based dc voltage control, the proposed method can realize a faster and more robust dc voltage control.

Thermal Management Technologies Used for High Heat Flux Automobiles and Aircraft: A Review

In recent years, global automotive industries are going through a significant revolution from traditional internal combustion engine vehicles (ICEVs) to electric vehicles (EVs) for CO2 emission reduction. Very similarly, the aviation industry is developing towards more electric aircraft (MEA) in response to the reduction in global CO2 emission. To promote this technology revolution and performance advancement, plenty of electronic devices with high heat flux are implemented on board automobiles and aircraft. To cope with the thermal challenges of electronics, in addition to developing wide bandgap (WBG) semiconductors with satisfactory electric and thermal performance, providing proper thermal management solutions may be a much more cost-effective way at present. This paper provides an overview of the thermal management technologies for electronics used in automobiles and aircraft. Meanwhile, the active methods include forced air cooling, indirect contact cold plate cooling, direct contact baseplate cooling, jet impingement, spray cooling, and so on. The passive methods include the use of various heat pipes and PCMs. The features, thermal performance, and development tendency of these active and passive thermal management technologies are reviewed in detail. Moreover, the environmental influences introduced by vibrations, shock, acceleration, and so on, on the thermal performance and reliability of the TMS are specially emphasized and discussed in detail, which are usually neglected in normal operating conditions. Eventually, the possible future directions are discussed, aiming to serve as a reference guide for engineers and promote the advancement of the next-generation electronics TMS in automobile and aircraft applications.

Design and Application of a Fault Detection Method Based on Adaptive Filters and Rotational Speed Estimation for an Electro-Hydrostatic Actuator.

The electro-hydrostatic actuator (EHA) is a promising actuating apparatus used in flight control systems for more electric aircraft (MEA) due to its high power density and low maintenance. Since the reliability of the system decreases with increasing complexity, fault detection is becoming increasingly important. In this paper, an adaptive filter was designed based on a normalized least mean square (NLMS) algorithm, which could identify the resistance of the motor windings online to detect electrical faults in the EHA. Additionally, based on the analytical relationship between rotational speed and displacement, a rotational speed estimation method was designed. By comparing the actual rotational speed with the estimated one, hydraulic faults could be detected. To verify the efficacy of the aforementioned method, software was applied for the modeling and simulations, which included fault injection and detection. On this basis, an experimental platform was built and then subjected to a series of validation experiments. The results indicate that the fault detection method has the potential to detect electrical and hydraulic faults in an EHA.

Adaptive state of energy evaluation for supercapacitor in emergency power system of more-electric aircraft

This paper presents an adaptive state of energy (SOE) evaluation method for a supercapacitor in the emergency power system of a more-electric aircraft. The adaptive SOE evaluation is realized based on a dynamic first-order RC equivalent circuit and its self-adaptive updated parameters. First, a dynamic first-order RC equivalent circuit with three parameters (i.e., the charge/discharge resistance R0, the dynamic self-discharge resistance R1, and the dynamic capacity C1) and a state-space model are introduced for modeling the supercapacitor. Then, an adaptive sliding mode observer is designed for tracking the dynamic change of the three state-space model parameters (i.e., R0, (R0+R1)/R1C1, and 1/R1C1). With this design, the three parameters of the dynamic first-order RC equivalent circuit can be updated adaptively along with the derivation of the three state-space model parameters. Moreover, the adaptive sliding mode observer is redesigned with a sign function, which can enhance the convergence rate of the three self-adaptive updated parameters. Finally, the accurate SOE evaluation would be achieved based on the three self-adaptive updated parameters. Various simulations and experiments are conducted to validate the adaptive SOE evaluation method. It is shown that the adaptive SOE evaluation method can achieve 0.5% of the maximum relative error of the estimated SOE. Compared with the commonly used method, the adaptive SOE evaluation method has over 1% improvement for the SOE estimation accuracy.

Quantitative Modeling and Analysis of Switching Oscillations of Cascode GaN Devices in Half-Bridge Converters

Having high efficiency and power density, the motor drives based on wide bandgap (WBG) devices can better meet the requirements for developing more electric aircraft (MEA). However, the fast switching characteristic of gallium nitride (GaN) devices has led to undesirable voltage and current oscillations during turn-ON and turn-OFF processes, thus decreasing the reliability of the electric drive system. The complicated structure of cascode GaN devices and various parasitic parameters in the device and the half-bridge converter make the switching oscillation modeling of cascode GaN device comparatively complex. In this article, an equivalent circuit approach in consideration of nonlinear characteristics in voltage-dependent junction capacitances is presented to model the switching oscillation for high-voltage (650 V) cascode GaN-based half-bridge converters. Quantitative mathematical models are derived to provide a theoretical analysis of the switching oscillation for turn-on and turn-off processes of cascode GaN devices. Furthermore, the influences of device and circuit parameters on the oscillation are investigated in detail, offering a reliable guidance to the gate driver and print circuit board design. Finally, experimental studies on the basis of cascode GaN and custom cascodes are carried out to validate the modeling approach. The results have proved that one of the root causes of the oscillations is how the different parasitics interact.