Electric Aircraft Applications Research Articles

230 VAC/28 VDC high‐power density power supply for more electric aircraft applications

The most important characteristics of aircraft power system are power density, reliability, availability and power quality. The traditional more electric aircraft (MEA) 28 VDC network is used to power the core electronic system. However, the 28 VDC network in modern MEAs such as B787 or A380 is a centralised power network obtained by transformer rectifier unit (TRU), battery charge and rectifier unit (BCRU) or two-stage power conversion (AC/DC + DC/DC) from 230 VAC, 400–800 Hz variable frequency input. The traditional centralised architecture is of low-power density and low fault tolerance. Furthermore, compared to distributed power network, the centralised architecture is of less availability inherently, therefore a single-stage, isolated, low-power and high-power density power supply is required to achieve the distributed 28 VDC network. In this study, a three-phase single-switch discontinuous mode AC–DC flyback converter is proposed. The converter directly rectifies a three-phase, 400–800 Hz, 230 VAC network into a 28 VDC network. The operation modes of the converter are analysed. A prototype is carefully designed and implemented using high-frequency planner transformer and SiC MOSFET techniques, aiming at higher performance. Experimental results demonstrate the practicability and high performance of the proposed power supply system.

Thermal analysis of fault‐tolerant electrical machines for more electric aircraft applications

For safety critical applications, electrical machines need to satisfy several constraints, in order to be considered fault-tolerant. In fact, if specific design choices and appropriate control strategies are adopted, fault-tolerant machines can operate safely even in faulty conditions. However, particular care must be taken for avoiding uncontrolled thermal overload, which can cause severe failures. This study describes the thermal modelling of a three-phase, synchronous machine for aerospace applications, analysing the machine's thermal behaviour under open-circuit fault conditions. A particular winding's layout is chosen with the purpose of satisfying fault-tolerance constraints. The winding temperature is evaluated by using a simplified thermal model, which was experimentally validated. Copper and iron losses, necessary for the thermal simulations, are calculated analytically and through electromagnetic finite element analysis, respectively. Finally, an aerospace study case is presented and the machine's thermal behaviour is analysed during both healthy and open-circuit conditions.

Fault diagnosis and tolerant control for power converter in SRM drives

Switched reluctance motors (SRMs) are considered a competitive technology for more electric aircraft and automotive applications due to their excellent fault-tolerant capabilities and robust configuration. In such applications, system reliability is a crucial feature. Therefore, here, a new fault-tolerant control strategy with real-time fault diagnosis for power transistor faults in SRM drives is proposed. The developed fault-tolerant topology is composed of four additional power switches and a relay network based on the conventional asymmetric converter. Moreover, an online fault diagnostic algorithm based on high-frequency (HF) signal injection is proposed. In contrast to the existing strategies that use additional sensors, this diagnostic algorithm extracts the fault signatures from the fundamental current by injecting an HF voltage signal into the upper switches of the asymmetric converter. Open- and short-circuit faults of the power switches are analysed by monitoring the variation in frequency and amplitude of the resulting HF current along with the amplitude variation in fundamental current with the occurrence of fault. Simulations performed on a three-phase 12/8 SRM drive and results are presented to validate the effectiveness of the proposed strategy.

A review of electromechanical actuators for More/All Electric aircraft systems

Conventional hydraulic actuators in aircraft systems are high maintenance and more vulnerable to high temperatures and pressures. This usually leads to high operating costs and low efficiency. With the rapid development of More/All Electric technology, power-by-wire actuators are being broadly employed to improve the maintainability, reliability, and manoeuvrability of future aircraft. This paper reviews the published application and development of the airborne linear electromechanical actuator. First, the general configuration, merits, and limitations of the gear-drive electromechanical actuator and the direct-drive electromechanical actuator are analysed. Second, the development state of the electromechanical actuator testing systems is elaborated in three aspects, namely the performance testing based on room temperature, testing in a thermal vacuum environment, and iron bird. Common problems and tendencies of the testing systems are summarized. Key technologies and research challenges are revealed in terms of fault-tolerant motor, high-thrust mechanical transmission, multidisciplinary modelling, thermal management, and thermal analysis. Finally, the trend for future electromechanical actuators in More/All Electric Aircraft applications is summarized, and future research on the airborne linear electromechanical actuators is discussed.

The IGBT Losses Analysis and Calculation of Inverter for Two-seat Electric Aircraft Application

This paper presented a parabola interpolation method to calculate the inverter IGBT losses, diode conduction losses, switching losses, total losses and efficiency. The method used parabola interpolation to fit the losses characteristic curves instead of linear approximation. A test platform for the two-seat electric aircraft inverter was set up, and the efficiency was tested. The efficiency was 95.13% at the current of 68.31 A and 93.42% at the current of 97.41 A. The errors between calculation and tested results were 3.3% and 3.9%, respectively. The errors both in the range of 4% verified a good agreement with experimental values and affirmed the accuracy of the parabola interpolation method.

A Droop Control Based Three Phase Bidirectional AC-DC Converter for More Electric Aircraft Applications

This paper addresses the design and implementation of a droop controlled three phase bidirectional AC-DC converter for more electric aircraft (MEA) applications. A unified control strategy using a droop characteristic is presented to achieve the bidirectional power flow between the AC and DC source while maintaining a stable DC output voltage. Based on the rigorous control design, the converter is capable of operating over a wide frequency range with a unity power factor. The key findings obtained from the theoretical analysis are confirmed by simulation studies and further validated by a scaled down laboratory prototype. The practical results show good performance of the bidirectional converter and demonstrate the effectiveness of the proposed control strategies.

Preliminary Development of Electric Motorcycle Engine for Sport Aviation Vehicles

Flying activities of sport aviation vehicles normally use Internal Combustion Engines (ICE) for their powerplant, which emits Carbon Dioxide (CO2) and also produces noise. Environmental issues regarding harmful gas emission and noise may restrict the sport aviation activities and resulting in reduction of interest in flying as a sport activity. The feasible solution for this issue is by replacing the Internal Combustion Engines (ICE) with Electric Engines on all sport flying vehicles. The Modenas CTric Electric Engines was tested to measure the parameters required by comparable Internal Combustion Engine used by sport aviation flyers. Other parameters; engine endurance, temperature and performance, were also tested. The bench test was conducted using specially design test rig. The results show that there is a possibility for the Modenas CTric Motorcycles Electric Engine used as an alternate source of powerplant for paramotors and microlight aircraft. However, there is penalty on the vehicle payloads due to weight of the battery. Lighter battery technology integration is to be developed to reduce the weight of the flight vehicles. This study serves as a platform for further work in electric engine technology for commercial aircraft application. Availability of green engine (no emission and noise output) will generate more interest in sport aviation activities and prepare for the future commercial Electric Engine aircraft application.

Low-inductance axial flux BLDC motor drive for more electric aircraft

As aircraft technology is moving towards more electric architecture, use of electric motors in aircraft is increasing. Axial flux BLDC motors (brushless DC motors) are becoming popular in aero application because of their ability to meet the demand of light weight, high power density, high efficiency and high reliability. Axial flux BLDC motors, in general, and ironless axial flux BLDC motors, in particular, come with very low inductance Owing to this, they need special care to limit the magnitude of ripple current in motor winding. In most of the new more electric aircraft applications, BLDC motor needs to be driven from 300 or 600 Vdc bus. In such cases, particularly for operation from 600 Vdc bus, insulated-gate bipolar transistor (IGBT)-based inverters are used for BLDC motor drive. IGBT-based inverters have limitation on increasing the switching frequency, and hence they are not very suitable for driving BLDC motors with low winding inductance. In this study, a three-level neutral point clamped (NPC) inverter is proposed to drive axial flux BLDC motors. Operation of a BLDC motor driven from three-level NPC inverter is explained and experimental results are presented.

Real-time simulation and control systems design by the Response Surface Methodology and designed experiments

This paper examines two cases where the fitting of a model to experimental data makes possible the solution of extremely difficult design and simulation problems. In the first (aerospace) case, designed experiments were conducted on a permanent magnet AC motor which provided the motive power for a flight surface actuator in a more electric aircraft application. The Response Surface Methodology is applied to the measured data to achieve inclusion of the component in a real-time distributed aircraft simulation. In the second (automotive) case, oscillatory acceleration responses are controlled via an electronically actuated (drive by wire) throttle. Designed experiments were conducted on the test vehicle to achieve a systematic excitation of the vehicle driveline. An approximation to the measured data is achieved by the Response Surface Methodology allowing a controller to be designed extremely rapidly.