Aircraft Electrical System Research Articles

Optimised temperature fluctuation control strategy for lifetime improvement in aircraft electrical power distribution system

As a power electronic converter with bidirectional energy transmission, the Dual Active Bridge (DAB) has a broad application prospect in the electrical power distribution system of hybrid-electric flight. For the DAB application in the electrical power distribution system, high efficiency and high reliability are envisaged due to the mission-critical nature of the application. A new pulse width modulation optimization control strategy is proposed, which is based on the feedback temperature fluctuations of the GaN (Gallium Nitride) power transistors, to improve the lifetime of the whole circuit. The complete topology and simulations of the DAB converter are carried out in PLECS. Detailed simulation results manifest the precise lifetime of the GaN power transistors and verify the accuracy of the new optimization control strategy. Meanwhile, Insulated Gate Bipolar Translator is set as a control group to compare the lifetime of conventional silicon-based power devices with the GaN power transistor. Hardware In Loop platform test is built to further validate the proposed method.

ANALYSIS OF STANDARDS REQUIREMENTS FOR AIRCRAFT BONDING

In the design, modernization and further aircraft operation, the issue of bonding as a means of electromagnetic interference control from equipment and static electricity, lightning protection is given much attention.
 The relevance of this article lies in the need to understand and comply with the requirements of the standards of all parts of the research and production cycle of modernization of aircraft from enterprises that develop devices and equipment for aircraft to the design bureaus of aircraft repair plants.
 To ensure the normal operation of radio technical apparatus on aircraft, protection against interference is applied, that caused by electrostatic charges due to voltage ripples on the generator commutator and engine manifold or at the output of rectifiers, as well as due to magnetic fields generated by various electrical facilities and wires.
 Interference protection of aircraft onboard equipment from electromagnetic interference is achieved by carrying out special measures, including screening of conductors, harnesses of the aircraft electrical system and ignition system of power drive units, bonding of shielding coatings of conductors and harnesses, structural elements and aircraft units. Bonding is also carried out to protect against lightning strikes.
 The article analyzes the requirements of state and industry standards for bonding, as the main technical measure of lightning protection and electromagnetic interference control on aircraft. Careful selection of the requirements of the standards allows to properly conduct and control the bonding of aircraft. It helps to determine the division of responsibilities in the design, execution and control of the state of bonding.

Development of a Wire Mesh Composite Material for Aerospace Applications

The electrical conductivity of Fiber-Reinforced Polymers (FRPs) may be used to reduce the dangers of lightning strikes, radar radiation, and aerial radio frequency transmitters. Metal Matrix Composites (MMCs) were created to guard against Electromagnetic Interference (EMI) in the aircraft's electric and electrical systems. High-Intensity Radiated Field Protection (HIRFP) aircrafts are required to be manufactured from a metal matrix consisting of Al6061, Al2O3, and Fly Ash (FA) to keep up with the ever-increasing needs of industry. The current work considered three MMC combinations. MMC1 is AL6061+10% and Al2O3+5% FA, MMC2 consists of AL6061+15 and Al2O3+5% FA, and MMC3 of AL6061+20% and Al2O3+5% FA. These MMCs made the shielding more effective at different percentages. The material electrical properties were interpreted based on experiments. Analytical approaches include the testing of the electrical parameters of materials to measure the shielding effectiveness. The calculated shielding efficiencies MMC1-55.7dB, MMC2-57.2dB, and MMC3-59.1dB allow the composites to be employed in aircrafts. This indicates that, for specific applications like HIRFPs, the constructed MMCs perform well.

A Quadrature Signal-Based Control Strategy for Vienna Rectifier Under Unbalanced Aircraft Grids

In order to eliminate the input current harmonics and dc-link voltage ripples of Vienna rectifier under unbalanced input, a novel control strategy applicable to wide variable frequency (360–800 Hz) aircraft electrical system is proposed in this article. To serve this purpose, current references on natural frame are first derived, which contain quadrature signals of grid voltages. Then, a natural-frame-based control strategy is designed, in which the second-order generalized integrator (SOGI) frequency-locked loop (FLL) is employed for variable frequency grids. Compared with traditional dual-frame control strategy, the proposed strategy reduces the algorithm complexity and has better frequency adaptability. The proposed strategy is suitable for all the unbalanced conditions, which is defined by test procedures DO-160G. Simulation and experimental results verify the effectiveness of the proposed control strategy.

Health management using fault detection and fault tolerant control of multicellular converter applied in more electric aircraft system

1. Rodger D. Current status and future plans for electric motors and drives at NASA. IEEE International Electric Motors and Drives Conference. 2021. Google Scholar

Application of Radar-Absorbing Materials for Attenuating High-Frequency Interference in the Electrical Circuits of Aircraft Electrical Systems

Conducted high-frequency electromagnetic interference is induced in the electrical circuits of aircraft electrical systems under the effect of external man-induced electromagnetic fields penetrating into the aircraft structure through radio-transparent apertures. To attenuate the impact of the conducted high-frequency electromagnetic interference induced in the two-wire lines of electrical bundles and other electrical circuits of electrical systems on sensitive semiconductor elements and integral microchips of on-board instruments and devices, low-pass filers on the basis of lumped components are used. At high frequencies, resonance phenomena may occur in the filter electrical circuits, which degrade the filter capabilities to attenuate conducted interference. Conducted high-frequency interference can be attenuated, and their propagation paths in the two-wire lines of electrical bundles and in the electrical circuits of on-board instruments and electrical system devices can be eliminated by applying radar-absorbing materials (RAM). Conducted electromagnetic interference in two-wire lines at a frequency above 1000 MHz generates high-frequency electromagnetic fields. With RAM placed in close proximity to the conductors of two-wire lines, it is possible to attenuate conducted high-frequency interference due to absorption of the interference electromagnetic field energy. The results of experimental studies are presented, the data of which make it possible to evaluate the extent to which the conducted high-frequency interference is attenuated in the frequency band 0.1–3000 MHz by applying radar-absorbing materials.

Hybrid Harmonic Suppression Method at DC Link of Series-Connected 18-Pulse Rectifier

To suppress the harmonics of series-connected 18-pulse rectifier, a hybrid harmonic suppression method is proposed in this paper. According to the structure of the converter and the KVL, the injection voltages are expressed. According to the injection voltages, the relation between the input voltage THD and the injection transformer turn ratio is obtained. Based on the relationship, when the THD of the input voltage researches the lowest value, the optimal injection transformer turn ratio is determined. Testing result shows that after using the proposed reduction method, the input side THD values of the converter are reduced. The capacity of the suppression circuit is only about 2% of the load power. The proposed converter is qualified for the interface between the AC generator and the DC bus of the aircraft electrical system.

Fault Diagnosis of Civil Aircraft Electrical Power System Based on Triangular Fuzzy Number and Grey Relational Analysis

Abstract The stable operation of the aircraft electrical power system is closely related to aircraft’s function implementation and safety. Therefore, research on fault diagnosis of aircraft electrical system is important and necessary. This paper proposes a fault diagnosis method of civil aircraft power system based on triangular fuzzy number and grey relational analysis. For the purpose of obtaining complete data, it takes into account single fault symptom and historical data, and keeps the fuzzy feature from initial estimation of diagnosis scheme to the end. The example analysis shows that this method has feasibility and efficiency in practical application.

Performance Investigation of Power Inverter Components Submersed in Subcooled Liquid Nitrogen for Electric Aircraft

Investigating the performance of power electronics devices and thus power inverters at cryogenic temperatures for electric aircraft systems are of great interest. Accordingly, the purpose of this study is to examine the inverter circuit technologies used in cryogenically-cooled electric aircraft applications from three perspectives: inverter topologies, power capabilities, and electromagnetic interference (EMI) that may occur. At a cryogenic temperature, the characteristics of five power semiconductor switches with different technologies (Si MOS, SiC MOS, and GaN HEMT) used in cryogenically-cooled electric aircraft inverters were tested and the results were presented. Furthermore, the low-temperature performance of three types of capacitors commonly used in power electronics inverters was investigated. The research findings provide crucial considerations for the research and development of power inverters cooled by sub-cooled liquid nitrogen for modern electric aircraft.

Pre-Flight Test Verification of Automatic Stabilization System Using Aircraft Trimming Surfaces

The new requirement of installing the flight stabilization system onboard the airplanes for performing the single-pilot flights in IFR rules was issued lately. It caused the necessity of developing such a system for small aircraft. The proposed system was developed using Model-Based Design then tuned and tested in Model, Pilot and Hardware in the Loop Simulations. The paper presents the next advanced stage of testing—verification in simulation and ground tests on the PZL-130 Orlik airplane. The implementation of this system does not modify the pilot’s primary manual controls. The newly introduced electrical trim is used for automatic stabilization but can be used at manual trimming as it was previously, depending on the chosen operation mode. The ground tests were planned according to civil aviation authority and aviation law requirements. Chosen results from simulated flights were analyzed and presented, confirming the effectiveness of the proposed system. The dedicated application allowing the test engineer to change stabilization system parameters during the flight on a touchscreen tablet was developed and described. The outcome of the stabilization system test campaign was a verification of its performance before the flight tests. The comparison of simulated and real flight data will allow identifying model deficiencies and flight stabilization system efficiency, which makes possible improvements implementation. Additionally, it appeared to be the cost-effective and less electrical energy-consuming automatic flight stabilization system for small aircraft. Such features benefit initiatives like Future Sky, More Electric Aircraft and aircraft stabilization system retrofit.

Structural static test for validation of the structural integrity of an aircraft pylon

Aircraft components can only be mounted on an aircraft if the structural integrity has been validated under flight load conditions. Among the major components of an aircraft, a pylon is a structure that connects external equipment such as an engine and external attachments (e.g., instruments or weapons) to the main wing of an aircraft. The loads acting on the pylon are transmitted to the main structure of the aircraft. Pylons play a key role in the requirements of aircraft structure, aerodynamics, hydraulics, and electrical systems. In civilian aircraft, pylons also play a role in preventing fire from spreading to the wings in the case of a fire near an engine. This study presents the results of structural static tests performed to validate the structural integrity of a pylon used to mount external fuel tanks and weapons in military aircraft under all loading conditions. Test requirements consisting of flight-load and drop-load conditions are explained in the main text. A test set-up diagram consisting of test fixtures, hydraulic pressure unit, load control equipment, and data acquisition equipment is presented. Moreover, the software needed to control the actuator loads is introduced and the test load profiles for each test load condition are provided. As a result of the structural static test, it is shown that the actuator loads were properly controlled within the allowable error range in each test. It was also confirmed that the behavior of the pylon was well predicted through numerical analysis by comparing the results of the numerical analysis and the structural tests of the main parts of the test specimen. Moreover, it was found that the test specimen did not cause damage or buckling, which would cause serious structural defects for the required load. In conclusion, by performing structural static tests on the design limit load and the design ultimate load, it was proved that the newly developed pylon had sufficient static strength under all load conditions during flight.

Advanced Aircraft Electric System and Equipment Testing

Advanced Aircraft Electric System and Equipment Testing

Analysis of shielding effectiveness and mechanical properties of metal matrix composite AL6061 reinforced with Al2O3 and fly ash for oblique incidence of EM wave

PurposeFiber-reinforced polymers (FRP) contain critical electrical conductivity for high-intensity radiated fields such as lightning strike susceptibility, electromagnetic energy from radar, airborne radio frequency transmitter. To provide high-intensity radiated field protection (HIRFP) for the electric and electronic aircraft system and defied the EMI effect on it, metal matrix composite was conquered. To provide the dynamic ever-increasing requirement of industries, it is necessary that Al6061 metal matrix composite assisted with AL2O3 and fly ash is used to construct the aircraft to provide HIRFP. The thickness of the material can be maintained as low as possible to use it as a coating material for the aircraft surface. X-band for oblique incidence is used to measure electromagnetic and mechanical safeguarding properties of composites.Design/methodology/approachDay by day, the applications of aerospace are becoming digital and automated. Proper shielding techniques are required to operate digital electronic devices without electromagnetic interference. It leads to a rapid rise in temperature, thermal ablation, delamination, and adverse effects on the electric and electronic aircraft system. Fly ash, a metal matrix material composite AL6061 with different percentages of reinforcement of Al2O3, was contemplated and experimented with for mechanical properties like tensile strength, density and hardness.FindingsThe obtained results compared with adjusted values and an improvement of 0.19, 0.18, 0.14 g/cm3 for density of MMC-1, MMC-2, MMC-3.31, 11 MPa for tensile strength of MMC-1, MMC-2. 24, 27, 23 BHN for hardness of MMC-1, MMC-2, MMC-3. With regard to the shielding effectiveness the results compared with adjusted values and obtained 11.36, 14.56, 19.47 dB better value than it. According to the above results, fabricated MMC’s provide superior results for a defined application like HIRFP(Surface material of aircraft).Practical implicationsIt can be used to protect electronic devices under a high-intensity radiated field, mainly in aircraft design to protect from lightning effect.Originality/valueFor a better approximation of the signal toward the practical case, the oblique incidence was considered with a different combination of Al2O3 and fly ash, reinforced to pure AL6061 to get better shielding and mechanical properties.

Moving towards Future Commercial Aviation and Electric Aircraft Systems

Moving towards Future Commercial Aviation and Electric Aircraft Systems

A multi-star synchronous machine model for real-time digital simulation and its applications

Poly-phase electric machines have the advantages of low ripple in torque, better fault tolerance and high reliability in operation. Such properties make them attractive for applications in renewable energies, electric ship propulsion, traction, aircraft systems and electric vehicles [1,2]. Failure of the drive system through a few phases could be tolerated by operating the remaining phases of the machine. One popular group amongst poly-phase electric machines is the category of multi-star machines.This paper presents development and validation of a multi-star synchronous machine model for a real-time digital simulator. The paper starts with the introduction and analysis of multi-star machines. A generalized method of Vector-Space Decomposition (VSD) is introduced for analyzing machines with an arbitrary number of stars. The method of incorporating the model into the network solution of real-time electromagnetic transient program is described. For the purpose of demonstration, a typical circuit of a marine electric vessel, containing poly-phase generators, power electronic converters, DC bus, hotel load, battery, and poly-phase propulsion systems is simulated in real time.

Development of a Turbo Electric Distribution System for Remotely Piloted Aircraft Systems

Turboelectric distributed propulsion systems are paving the way for more electric aircraft systems (TeDP). This type of system provides a solution for some of the drawbacks of current low-energy-density batteries, which limit the ability of long-endurance electric aircraft. However, turboelectric propulsion requires the use of advanced turboelectric motors, superconductive materials and cryogenic cooling technologies, which are still under development and may be in production in the near future. This paper investigates a turboelectric propulsion system that can be considered an initial step in the production of TeDP in a remotely piloted aircraft system with the use of existing technology. This is achieved by replacing the gear and the starter motor of a turboprop with a high-speed permanent magnet electric machine to generate electrical power and propelling the aircraft through a distributed electric propulsion system. In this theoretical study, an augmentation to Breguet’s range and endurance equation is developed. This study confirmed that the new system is 31% lighter than the turboprop engine. Then the effect of the weight savings is used in the distributed electric propulsion (DEP) aerodynamic studies and found that there is a drastic increase in the range for a TeDP developed with the high-speed machine.

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.

Перекрестные помехи в электрических соединителях

Crosstalk electromagnetic interference occurs in on-board electrical wire bundles of aircraft electrical systems under the effect of external electromagnetic fields. Efficient reduction of crosstalk and elimination of their propagation paths in wire bundles can be achieved by shielding the conductors in the bundles and the bundles as a whole without breaks and discontinuities between the shields and housings of electrical connectors. The shielding of conductors in bundles does not eliminate the crosstalk completely, which can propagate through the contacts of electrical connectors. For estimating the influence of electrical connectors on the levels of crosstalk in electrical system circuits, their experimental studies should be carried out. In the course of these experimental studies, the interference voltage induced at the receptor contacts when voltage is applied to the source contacts in the specified frequency band is measured. The results from experimental studies of crosstalk for various types of electrical connectors in a specified frequency band make it possible to evaluate the resonance nature and levels of crosstalk interference levels depending on the relative position of the contacts and frequency.

A proposal for a lightweight, large current superconducting cable for aviation

More Electric Aircraft (MEA) is one of the most important subjects for designing the next generation of aircraft. Since we cannot ground the electric power systems of a flying aircraft and the air insulation voltage is lower at high altitude, a low voltage, direct current (DC) aircraft electrical system is preferable for a MEA. Since the current must be high to supply high power, we consider high temperature superconducting (HTS) technology because it handles large currents well. We propose a new HTS cable in this paper. The cable uses a stacked conductor, with oppositely directed current in each HTS tape, a structure that has already been shown to be feasible for low voltage cables. It enhances the critical current compared to a single tape conductor, especially for Bi2223 tape. In order to avoid a current imbalance in the stacked conductor, we use the current lead resistance rather than a Roebel conductor design. Then the critical current remains high, and this is confirmed by measurements. The cryogenic pipe will be made of magnesium-lithium alloy, one of the lightest metals available at the present time. We estimate the weight-to-current ratio per unit length to be less than 0.5 kg/A/km at the liquid nitrogen operational temperature of 77 K, lighter than conventional copper cable. If instead we use liquid hydrogen at 20 K, we expect a value less than 0.1 kg/A/km, which is one of the lowest presently achievable values and satisfies the requirements for MEA.

Utilisation of Ram Air Turbine on a Fighter Platform for Energy Extraction Failure Mode Study

Aircraft electrical system needs to be robust enough to cater for electrical power requirements of all the systems of the aircraft and all the safety/degraded mission critical systems in failure modes. Designing such a robust electrical system for a developmental aircraft program is a challenge. A developmental aircraft during its various phases would involve integration of additional systems and new weapons (in case of fighter aircraft). Integration of newer systems imposes fresh challenges in managing the electrical system architecture especially in failure modes. Weapon integration in a prototype fighter program is dynamic as newer contemporary weapons are developed at faster pace and ever evolving. Power crisis through existing on-board power generation systems in failure mode was felt during an indigenous aircraft development program. A novel idea of introducing a Ram Air Turbine and utilize the power generated during main alternator failure for critical systems was studied. The intention of this paper is to cover the details of the study carried out towards utlisation of such a Ram Air Turbine in landing phase for extraction of energy in case of main alternator failure.