Aircraft Electrical Power Research Articles

Early Design Stage Evaluation of All Electric Aircraft Power Systems Focusing on Long-Term Behavior

In the aircraft industry, there is a shift towards more and all-electric power systems resulting in great research efforts on single components like batteries. At the same time there is an increasing need to investigate and evaluate the long-term behavior of the whole electric power system to ensure safe and sustainable aircraft operation. Focusing on this challenge, the objective of this article is to propose a framework for electric power system assessment in the early design stages. In particular, the focus is on identifying and handling uncertainties regarding failure behavior and degradation, both on the component and system level. The evaluation of different power system topologies is based on the integration of Model-Based Systems Engineering and robust design methods. In this context, another central aspect is the definition of system and component requirements derived from the flight mission profile. SysML diagrams are used to define use cases and possible system topologies. Sensitivity of degradation effects are evaluated using robust design methods. The application of the framework and these methods is illustrated using a short-range aircraft with an all-electric power system. The results highlight the applicability of the framework to cope with the uncertainties that occur in the early design stages and point out fields of further research.

I-CNN-LSTM: An Improved CNN-LSTM for Transient Stability Analysis of More Electric Aircraft Power Systems

I-CNN-LSTM: An Improved CNN-LSTM for Transient Stability Analysis of More Electric Aircraft Power Systems

Multimodal transient topology optimization design of heat dissipation structure in electric aircraft power cabin

High power density electronic devices are widely installed in electric aircraft power cabin with finite space, which causes the heat to be dissipated difficultly. In this work, a multimodal transient topology optimization model based on the weight coefficient method is proposed to obtain a lightweight and efficient heat dissipation structure in electric aircraft power cabin. The proposed topology optimization model can consider all flight envelope including takeoff, cruise and landing processes. The effect of the topology weight coefficient on the heat dissipation capacity in all flight envelope is investigated. Results show that the heat dissipation efficiency of the topology optimization structure can be improved by 11.25%, 9.18%, and 11.27% in the takeoff, cruise and landing processes compared with that of the conventional heat dissipation structure, respectively. Increasing the topology weight coefficient by 6.67% can result in an 3.47% improvement in the heat dissipation efficiency during the takeoff and landing processes. The above findings can be used as a reference for the design of the lightweight and efficient heat dissipation structure in electric aircraft.

Multilevel Aircraft-Inverter Design Based on Wavelet PWM for More Electric Aircraft

This paper proposes a comprehensive power system designed for the use of a more electric aircraft power distribution system. Instead of traditional Nicad battery solutions as the energy source of the aircraft power system, lithium battery structures, which are a recent and promising solution in the field of aviation power systems, are modeled and analyzed. In this study, a WPWM-based, single-phase, multi-level pure sine wave static aircraft-inverter system is designed and integrated to improve the performance of conventional aircraft power systems. In the designed power system, a boost converter structure is proposed that boosts 28 VDC-to-270 VDC voltage coming from the lithium–ion battery pack and can reach a steady state in 0.032 s. The performance of the modeled WPWM-based aircraft-inverter system, compared to SPWM Bipolar and Unipolar switching techniques commonly used in single-phase inverter designs, reveals a THD reduction of approximately 27% with WPWM, resulting in a THD value below 2% for both load current and load voltage. As a result of the study, a power system that will enable the aircraft avionics, ventilation, and navigation systems to perform better than conventional power systems and comply with aircraft electric-power characteristic standards has been designed and detailed.

Design and Optimization of Control System for More Electric Aircraft Power Systems Using Adaptive Tabu Search Algorithm Based on State-Variables-Averaging Model

Design and Optimization of Control System for More Electric Aircraft Power Systems Using Adaptive Tabu Search Algorithm Based on State-Variables-Averaging Model

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.

A review of conventional and new-generation aircraft starter/generators in perspective of electric drive applications

PurposeMore electric aircraft (MEA) is defined as the extensive usage of electric power in aircraft. The demand for electric power in new generation aircraft rises due to environmental and economic considerations. Hence, efficient and reliable starter/generators (SGs) are trending nowadays. The conventional main engine starting system and power generation system can be replaced with an individual SG. The constraints of the SG should be investigated to handle the aviation requirements. Even though the SG is basically an electric machine, it requires a multidisciplinary study consisting of electromagnetic, thermal and mechanical works to cope with aviation demands. This study aims to review conventional and new-generation aircraft SGs from the perspective of electric drive applications.Design/methodology/approachFirst of all, the importance of the MEA concept has been briefly explained. Also, the historical development and the need for higher electrical power in aircraft have been indicated quantitatively. Considering aviation requirements, the candidate electrical machines for aircraft SG have been determined by the method of scoring. Those machines are compared over 14 criteria, and the most predominant of them are specified as efficiency, power density, rotor thermal tolerance, high-speed capability and machine complexity. The features of the most suitable electrical machine are pointed out with data gathered from empirical studies. Finally, the trending technologies related to efficient SG design have been explained with numeric datasets.FindingsThe induction motor, switched reluctance motor and permanent magnet synchronous motor (PMSM) are selected as the candidate machines for SGs. It has been seen that the PMSM is the most preferable machine type due to its efficient operation in a wide range of constant power and speed. It is computationally proven that the using amorphous magnetic alloys in SG cores increases the machine efficiency more. Also, the benefits of high voltage direct current (HVDC) use in aircraft have been explained by a comparison of different aircraft power generation standards. It is concluded that the HVDC use in aircraft decreases total cable weight and increases aircraft operation efficiency. The thermal and mechanical tolerance of the SG is also vital. It has been stated that the liquid cooling techniques are suitable for SGs.Originality/valueThe demand for electrical power in new generation aircraft is increasing. The SG can be used effectively and efficiently instead of conventional systems. To define requirements, constraints and suggestions, this study investigates the SGs from the perspective of electric drive applications.

Multi-Domain Modeling and Simulation of High-Temperature Superconducting Transmission Lines Under Short-Circuit Fault Conditions

Emission reduction in transportation requires advancements in aviation technologies enabling fully electrified propulsion, among which the use of superconducting technologies can provide untapped benefits given their low weight and minimal losses for high-power transmission. However, to enable their use in aircraft electrical power systems, additional considerations for electrical and thermal performance during faults is required in order to meet stringent aircraft safety requirements. In this work, a cryogenically cooled electric aircraft power system is studied under short-circuit conditions for different cooling media. This system consists of a fuel cell, high-temperature superconducting (HTS) transmission line, inverter, and motor, where each of their fault models have been explored. A trade-off study of the impedance of the fuel cell is conducted to identify the values at which the superconducting cable remains thermally stable after a short-circuit fault, as it is crucial that the cable does not experience a thermal runaway.

Hybrid Deep Reinforcement Learning Considering Discrete-Continuous Action Spaces for Real-Time Energy Management in More Electric Aircraft

The increasing number and functional complexity of power electronics in more electric aircraft (MEA) power systems have led to a high degree of complexity in modelling and computation, making real-time energy management a formidable challenge, and the discrete-continuous action space of the MEA system under consideration also poses a challenge to existing DRL algorithms. Therefore, this paper proposes an optimisation strategy for real-time energy management based on hybrid deep reinforcement learning (HDRL). An energy management model of the MEA power system is constructed for the analysis of generators, buses, loads and energy storage system (ESS) characteristics, and the problem is described as a multi-objective optimisation problem with integer and continuous variables. The problem is solved by combining a duelling double deep Q network (D3QN) algorithm with a deep deterministic policy gradient (DDPG) algorithm, where the D3QN algorithm deals with the discrete action space and the DDPG algorithm with the continuous action space. These two algorithms are alternately trained and interact with each other to maximize the long-term payoff of MEA. Finally, the simulation results show that the effectiveness of the method is verified under different generator operating conditions. For different time lengths T, the method always obtains smaller objective function values compared to previous DRL algorithms, is several orders of magnitude faster than commercial solvers, and is always less than 0.2 s, despite a slight shortfall in solution accuracy. In addition, the method has been validated on a hardware-in-the-loop simulation platform.

A 380 V/50 kVar SiC-SVG Achieving a Power Density of 1.652 kVar/L With the Optimization of Heatsink and Output Filter Volume

With the rapid development of new energy vehicles, 5G facilities, electric aircraft, and new energy power generation, the high-power-density inverters are developed rapidly. A comprehensive optimization method combining heatsink and inductance filter was proposed in this article. Based on accurate thermal modeling and magnetic modeling, the method proposed chose an optimized switching frequency to minimize the volume of the inverters by compromising the design of the heatsink and inductor volume. Among them, a model of multichip forced air-cooling heatsink was proposed to reduce the size of the heatsink, and the comprehensive thermal resistance error of the proposed model is within 2%. The structure of the grid-connected filter and the inductor model is analyzed showing that the single inductor L-filter has a smaller size and more stability than the LCL-filter at a high switching frequency. The comprehensive optimization method proposed was implemented by 380-V/50-kVar SiC-static var generator (SVG) with the 50-kHz switching frequency, and its topology is a two-level inverter with a single inductor filter. This SiC-SVG reached a volume of 30.2 L (including all components required for mainstream products), which is 50% lower than insulated gate bipolar translator (IGBT)-SVGs. Its efficiency is 98.5% at full load, which is 1.5% higher than IGBT-SVGs. The experiments and temperature rising tests at full load proved the feasibility of the comprehensive optimization method.

The Architecture Optimization and Energy Management Technology of Aircraft Power Systems: A Review and Future Trends

With the development of More/All-Electric Aircraft, especially the progress of hybrid electrical propulsion or electrical propulsion aircraft, the problem of optimizing the energy system design and operation of the aircraft must be solved regarding the increasing electrical power demand-limited thermal sink capability. The paper overviews the state of the art in architecture optimization and an energy management system for the aircraft power system. The basic design method for power system architecture optimization in aircraft is reviewed from the multi-energy form in this paper. Renewable energy, such as the photo-voltaic battery and the fuel cell, is integrated into the electrical power system onboard which can also make the problem of optimal energy distribution in the aircraft complex because of the uncertainty and power response speed. The basic idea and research progress for the optimization, evaluation technology, and dynamic management control methods of the aircraft power system are analyzed and presented in this paper. The trend in optimization methods of engineering design for the energy system architecture in aircraft was summarized and derived from the multiple objective optimizations within the constraint conditions, such as weight, reliability, safety, efficiency, and characteristics of renewable energy. The cost function, based on the energy efficiency and power quality, was commented on and discussed according to different power flow relationships in the aircraft. The dynamic control strategies of different microgrid architectures in aircraft are compared with other methods in the review paper. Some integrated energy management optimization strategies or methods for electrical propulsion aircraft and more electric aircraft were reviewed. The mathematical consideration and expression of the energy optimization technologies of aircraft were analyzed and compared with some features and solution methods. The thermal and electric energy coupling relationship research field is discussed with the power quality and stability of the aircraft power system with some reference papers. Finally, the future energy interaction optimization problem between the airport microgrid and electric propulsion aircraft power system was also discussed and predicted in this review paper. Based on the state of the art technology development for EMS and architecture optimization, this paper intends to present the industry’s common sense and future trends on aircraft power system electrification and proposes an EMS+TMS+PHM to follow in the electrified aircraft propulsion system architecture selection

A Novel More Electric Aircraft Power System Rectifier Based on a Low-Rating Autotransformer

From a theoretical and practical point of view, to increase rating and decrease the cost and complexity of a multi-pulse rectifier (MPR), its pulse number has to be increased. In many industrial applications, a 20-pulse rectifier is suggested as the practical solution considering its simple structure and low weight. But the 20-pulse rectifiers, suggested in different studies, must use filters to satisfy the DO-160G requirements for 21st and 39th harmonics for ac–dc more electric aircraft (MEA) power systems. To overcome this problem, this article proposes a novel 20-pulse rectifier for the ac–dc MEA power system based on a low-rating autotransformer (LRA). Also, a passive harmonic reduction circuit (PHRC) is used on the dc side of the 20-pulse rectifier to suppress the harmonics up to the 40th order according to DO-160G without using any filter. In this article, simulations are provided to show the merits of this new rectifier over other proposed solutions. Then, an experimental prototype is implemented for evaluating and verifying the simulation results. By investigating the captured outcomes, this article concludes that the introduced design is practical and can simultaneously consider the trade-off among autotransformer structure, pulse number, complexity, rating, and cost.

Partial discharge detection and identification at low air pressure in noisy environment

Increasing demand for electric power in more electric aircraft requires a higher operating voltage for the power system that leads to higher electric stress on the insulation system. Operating at high altitudes where the electrical strength of air is weakened exposes the insulation system to even higher levels of electrical stress. As such, the probability of partial discharges (PD), which result in insulation degradation and failure, is higher. The presence of switching circuits in the power distribution system of the more electric aircraft is capable of producing high levels of noise. This noise in combination with the background noise and parasitic impedances will cause high amplitude ringing in the measured partial discharge signal waveform. Here, a method based on the combination of the wavelet and energy techniques is employed to detect PD pulses in a noisy environment under the low air pressure condition. To verify the technique, a laboratory setup consisting of two separate PD sources mounted in low air pressure (33 kPa) chamber is developed where sine and square waveforms are used as the applied voltage. The obtained results demonstrate that the proposed approach offers low computational complexity, high performance in PD phase localization, and robustness in a noisy environment.

SiC-Based 5-kV Universal Modular Soft-Switching Solid-State Transformer (M-S4T) for Medium-Voltage DC Microgrids and Distribution Grids

Medium-voltage dc (MVdc) grids are attractive for electric aircraft and ship power systems, battery energy storage system (BESS), fast charging electric vehicle (EV), etc. Such EV or BESS applications need isolated bidirectional MVdc to low-voltage dc (LVdc) or LVac converters. However, the existing Si-based solutions cannot fulfill the requirements of a high-efficiency and robust converter for MVdc grids. This article presents a 5-kV SiC-based universal modular solid-state transformer (SST). This universal current-source SST can interface either an LVac or LVdc grid with an MVdc grid in single-stage power conversion, while the conventional dual-active bridge (DAB) converter needs an additional inverter. The proposed SST module using 3.3-kV SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MOSFET</small> s and diodes is bidirectional and can serve as a building block in series or parallel for higher voltage higher power systems. The topology of each module is based on the soft-switching solid-state transformer (S4T) with reduced conduction loss, which features reduced electromagnetic interference electromagnetic interference (EMI) through controlled dv/dt, and high efficiency with full-range zero-voltage switching for main devices and zero-current switching for auxiliary devices. Operation principle of the modular S4T (M-S4T), capacitor voltage balancing control between the cascaded modules, design of components including a medium-voltage (MV) medium-frequency transformer (MFT) to realize a 50-kVA, 5-kV dc to 600 V dc or 480 V ac M-S4T are presented. Importantly, the MV MFT prototype achieves very low leakage inductance (0.13%) and 15-kV insulation with coaxial cables and nanocrystalline cores. The proposed universal modular SST is compared against the DAB solution and verified with dc–dc and dc–ac simulation and 4-kV experimental results. Significantly, the MV experimental results of a modular dc transformer with each module at MVdc are rarely covered in the literature and reported for the first time.

Multi-Objective Optimization for Aircraft Power Systems Using a Network Graph Representation

Today, the electrification of flight is more popular than ever, creating a wide array of concept aircraft and associated power system topologies. In order to gain insights into benefits of these varying architectures, this article introduces the development of a framework for electric aircraft power system (EAPS) optimization. The proposed framework accepts inputs from a designer in the form of component parameters and desired flight mission characteristics. A collective graph representing many possible architectures is formed, from which subgraphs that describe power system topologies meeting the flight requirements are extracted and analyzed. Optimal EAPS architectures with respect to goals of minimizing mass while maximizing efficiency and reliability can be subsequently selected from these subgraphs. The framework is exemplified on a 500-kW rated aircraft using data collected from surveys of component parameters, such as power density and efficiency. The presented results show a comparative analysis of different EAPS types with respect to the competing performance metrics of mass, efficiency, and survivability.

Бортовая система электроснабжения для электрических самолетов

The development of electric aircraft, the design of which will use, apart from doing away with pneumatic and hydraulic transmissions, electric propulsion, is one of promising lines in aviation technology. As an example, the project of the X-57 Maxwell electric aircraft developed by NASA, which is equipped with 14 propulsion electric motors, is given. In view of insufficient energy efficiency of existing storage batteries, a combined storage battery-and-generator power supply system for electric aircraft is considered. In the considered system, the aircraft propulsion is provided by electric motors, which are powered by storage batteries in combination with permanent magnet generators. The generator shaft is rotated by an auxiliary internal combustion engine, which operates in an economical mode. The power circuit of an active rectifier producing the +270 V DC bipolar output voltage is proposed, with which the permanent magnet generator operates with a sinusoidal phase current waveform and a close-to-unity power factor. The active rectifier control system uses an enhanced phase-locked loop, which eliminates the need to use generator rotor position sensors. For determining the stability domains and revealing undesirable hidden attractors in the considered storage battery-and-generator power supply system, it is proposed to use special analytical-numerical computation procedures based on modifications of Lyapunov's functions methods. The article will be of interest for developers of both aircraft and ground-based self-contained electric power supply systems with a bipolar 270 V DC voltage that must meet stringent requirements for improvement of their mass-and-dimensions and power performance characteristics.

Improvement of Recursive DFT for APF With Higher Switching Frequency to Suppress Wideband Harmonics

Shunt active power filter (APF), with higher switching frequency, has a potential market for suppressing wideband harmonics in the more electric aircraft (MEA) or high-speed train (HST) power grid. In this case, the selective extraction of harmonic current reference is essential. Recursive discrete Fourier transform (RDFT) is widely adopted for its excellent selectivity and low computational burden. However, RDFT is tough to implement in the higher frequency APF with the shorter switching cycle, and suffers from the demerit of slow dynamics. To alleviate those, three improved RDFTs are proposed in this paper. Firstly, it is revealed that RDFT can be regarded as a series of DFT and inverse-DFT (IFT), and its settling time depends on the comb filter of DFT. Then, by rearranging the sampling frequency of DFT according to the extracted harmonic, the computational burden of twice-sampling RDFT (TS-RDFT) is reduced while satisfying the same extraction accuracy. Furtherly, to improve the dynamics of TS-RDFT while retaining the merits of simplicity and selectivity, the comb filter is reconfigured based on the load current spectrum. For balanced loads, the settling time of TS-RDFT can be shortened from 1 to 1/6 fundamental cycle in the synchronous reference frame. For unbalanced loads, it is shortened to 1/2 cycle in the $\alpha \beta $ frame. Finally, the simulations with Matlab for harmonic extraction in 400Hz grid and the experiments with the APF prototype for harmonic suppression in 50Hz grid are carried out to verify the effectiveness of the proposed methods.

Power control system for lightweight electric aircraft

This article describes the development and key features of the lightweight electric aircraft power system. The overview includes internals of main power control units and propulsion system rigging, hardware parts selection guide and fail-safe features in hardware and software of aircraft. The propulsion system includes lightweight solution utilizing brushless DC (BLDC) motor with a propeller as the main thrust generator, and a control system, which consists of insulated gate bipolar transistors (IGBT) 3-phase bridge and control system, as well as a special optical-insulated throttle controller. Main power control system automatically starts up aircraft modules and provides all the necessary information coming from the sensors. All of the key components in aircraft are connected through Controller Area Network (CAN) interface. To create a strong protection against surges and electric interference special cabling and interfacing aspects between several systems of lightweight aircraft are described. Part of the article provides a future extendibility, versatility and economical concepts.

Detection of DC series arc in more electric aircraft power system based on optical spectrometry

Series arcing faults have been recognised as a hazardous phenomenon in the power system of more electric aircraft (MEA), especially with the increasing voltage level and power supply. Instead of the electrical method, the optical method can be used as an approach to detect arc fault with the advantages of fast response and immunity to electromagnetic interference. It is the basis of optical arc detection to determine the distribution spectrum range of direct current (DC) arc fault. Aiming at series arc optical detection in the MEA DC system, a DC series arc test platform was established to measure the series arc spectrum. The spectrum was disassembled though empirical mode decomposition to extract characteristic wavelengths of arc light and de-noised by means of wavelet decomposition and reconstruction (wavelet transformation) to reduce equipment noise. To resolve the baseline drift, the baseline of the arc spectrum measured was calculated and corrected based on Savitzky−Golay. The experimental results indicate that there are several series arc characteristic spectra of the MEA DC system, including 309.3 and 324.5 nm in the ultraviolet range. Moreover, the arc spectrum with different metals, copper and aluminium, were contrasted, indicating the arc spectral behaviour is related to the melting/boiling point and chemical properties of the anode material. The measurement of the series arc spectrum makes it more effective to apply optical detection in the MEA discharging faults diagnosis.

Machine Learning Building Blocks for Real-Time Emulation of Advanced Transport Power Systems

The revolution of artificial intelligence (AI) is transforming major industries worldwide. With accurate inferencing, AI has caught the attention of many engineers and scientists. Promisingly, hardware-in-the-loop (HIL) emulation can adopt this type of modeling method as one of the alternatives after comprehensive investigation. This paper proposes an approach for emulating power electronic motor drive transients for advanced transportation applications (ATAs) using machine learning building blocks (MLBBs) without any traditional circuit-oriented transient solver. The more electric aircraft (MEA) power system is chosen as a case study to validate the real-time emulation performance of MLBBs. Inside MLBBs, neural networks (NNs) have been applied to build component-level, device-level, and system-level models for various equipment. These models are well trained in a cluster and transplanted into the field-programmable gate array (FPGA) based hardware platform. Finally, MLBB emulation results are compared with PSCAD/EMTDC for system-level and SaberRD for device-level, which showed high consistency for model accuracy and high speed-up for hardware execution.