Aircraft Electric Power System Research Articles

Robustness and reliability review of Si and SiC FET devices for more-electric-aircraft applications

Increased electrification of traditionally hydraulic and pneumatic functions on aircrafts has put power electronics at the heart of modern aviation. Aircraft electrical power systems have traditionally operated at 115 V AC and 28 V DC with a constant speed generator and transformer rectifier units converting jet engine power into electrical power. However, due to the increasing trend towards the More Electric Aircraft (MEA), 270 V DC systems are likely in the future. This calls into question, the power semiconductor device technology that enables the on-board power converters needed for electro-mechanical actuation as well as solid-state circuit breakers for system protection. Silicon IGBTs have been the work-horse of power electronics, but as switching speeds increase due to the need for high frequency operation, the bipolar nature of IGBT tail currents become a limiting factor for improved energy conversion efficiency. A number of unipolar FET technologies, including SiC trench MOSFETs, SiC planar MOSFETs, silicon super-junction MOSFETs and SiC JFETs in cascode with a low voltage Si MOSFET, have become commercialized at around 650 V. However, reliability and robustness, especially against single event burn-out and/or single event gate rupture is critical. This paper experimentally investigates the performance of the listed FET devices under Unclamped Inductive Switching and Bias Temperature Instability/gate oxide stress tests.

An Analytical AC Resistance Calculation Method for Multiple-Conductor Feeder Cables in Aircraft Electric Power Systems

In multiphase ac power systems, e.g., aircraft electric power systems (EPS), the proximity effect between the feeder cables can be severe and complex due to the tightly wired cable bundles. Simulation software is widely used to analyze such effects in order to guarantee proper system operation, but it is highly time consuming and requires extensive computational resources. Accordingly, this paper proposes an analytical calculation method for estimating the ac resistance of closely bundled power cables, namely multiconductor cables. Simulation and experimental tests are performed to validate the effectiveness and accuracy of the method, showing that the algorithm developed in this paper is easy to implement with a minimum accuracy of 92% in all the tests. It allows online estimation of cable resistances, which can be beneficial for advanced system monitoring and management to enhance safety and reduce losses. Aircraft EPS and cables are used as the example in this paper, while the proposed method is also applicable for other applications, such as shipboard EPS, renewable energy parks, or microgrids where multiconductor cables are used.

A Novel Methodology for Macroscale, Thermal Characterization of Carbon Fiber-Reinforced Polymer for Integrated Aircraft Electrical Power Systems

Carbon fiber-reinforced polymer (CFRP) is increasingly used for aero-structure applications due to their high strength-to-weight ratio. The integration of the on-board electrical power system (EPS) with CFRP is challenging due to the requirement to thermally and electrically isolate these systems to meet existing safety standards. By capturing the thermal characteristics of CFRP at a macro (component) scale for CFRP components, it is possible to understand, and design for, the increased integration of the EPS into CFRP aero-components. A significant challenge is to develop a macroscale characterization of CFRP, which is not only of an appropriate fidelity for compatibility with systems-level models of an EPS but also can be used to represent different geometries of CFRP components. This paper presents a novel methodology for capturing a transient, macroscale thermal characterization of CFRP with regard to component layup and geometry (thickness). The methodology uses experimentally derived thermal responses of specific resin and ply orientation CFRP samples to create a generalized relationship for the prediction of thermal transfer in other sample thicknesses of the same material type. This methodology can be used to characterize thermal gradients across CFRP components in aircraft EPS integration applications, ultimately informing the optimized integration of the EPS with CFRP.

The Analysis of Power supply Characteristics of Aircraft Power supply System

With the rapid development of multi-electric aircraft technology, the aircraft electrical power system is becoming more and more complex and significant. This paper analyzes power supply characterisitics of aircraft power supply system. First, the Generalized State Space Averaging (GSSA) technique is adopted to realize the digital simulation of complex aircraft electrical system. Next, AC vector coordinate transformation, digital zero-crossing detection and least squares polynomial fitting are used to analyze power supply characteristics of aircraft power supply system. Finally, the power quality of the power supply system is analyzed in the time domain and the trend analysis diagram of these power quality parameters with the variation of time is given.

Behavior and functional modeling methods of doubly salient electromagnetic generators for aircraft electrical power system applications

The Doubly Salient Electromagnetic Generator (DSEG) is a promising candidate in aircraft generator application due to the simplicity, robustness and reliability. However, the field windings and the armature windings are strongly coupled, which makes the inductance characteristics non-linear and too complex to model. The complex model with low precision also leads to difficulties in modeling and analysis of the entire aircraft Electrical Power System (EPS). A behavior level modeling method based on modified inductance Support Vector Machine (SVM) is proposed. The Finite Element Analysis (FEA) inductance data are modified based on the experiment results to improve the precision. A functional level modeling method based on input–output characteristics SVM is also proposed. The two modeling methods are applied to a 9 kW DSEG prototype. The steady state and transient process precision of the proposed methods are proved by comparing with the experiment results. Meanwhile, the modeling time consumption, the application time consumption and the calculation resource demand are compared. The DSEG behavior and functional modeling methods provide precious results with high efficiency, which accelerates theoretical analysis and expands the application foreground of the DSEG in the aircraft EPS.

Analysis of Civil aircraft Electrical Power System Load Shed Issue Based on QAR Data

As the significant recording equipment of civil aircraft, Quick Access Recorder (QAR) record the operation status of the aircraft system and QAR Data is the important basis for safety assessment, maintenance check and fault analysis. About civil aircraft system faults or fails, sometimes we can’t give a reasonable explanation just based qualitative analysis. Via the integrity and accuracy of the QAR Data, the crew can give quantitative analysis and get exact determination. Based on the quantitative analysis of the relevant QAR Data, this paper has found the Load Shed caution root cause of a certain type of aircraft.

A Novel Robust Model Predictive Controller for Aerospace Three-Phase PWM Rectifiers

This paper presents a novel Model Predictive Direct Power Control (MPDPC) approach for the pulse width modulation (PWM) rectifiers in the Aircraft Alternating Current Variable Frequency (ACVF) power system. The control performance of rectifiers may be largely affected by variations in the AC side impedance, especially for systems with limited power volume system. A novel idea for estimating the impedance variation based on the Bayesian estimation, using an algorithm embedded in MPDPC is presented in this paper. The input filter inductance and its equivalent series resistance (ESR) of PWM rectifiers are estimated in this algorithm by measuring the input current and input voltage in each cycle with the probability Bayesian estimation theory. This novel estimation method can overcome the shortcomings of traditional data based estimation methods such as least square estimation (LSE), which achieves poor estimation results with the small samples data set. In ACVF systems, the effect on the parameters estimation accuracy caused by the number of sampling points in one cycle is also analyzed in detail by simulation. The validity of this method is verified by the digital and Hard-in-loop simulation compared with other estimation methods such as the least square estimation method. The experimental testing results show that the proposed estimation algorithm can improve the robustness and the control performance of the MPDPC under the condition of the uncertainty of the AC side parameters of the three-phase PWM rectifiers in aircraft electrical power system.

A balancing act for electric aircraft power systems

A balancing act for electric aircraft power systems

Multi-Objective Optimization Control for the Aerospace Dual-Active Bridge Power Converter

With the development of More Electrical Aircraft (MEA), the electrification of secondary power systems in aircraft is becoming more and more common. As the key power conversion device, the dual active bridge (DAB) converter is the power interface for the energy storage system with the high voltage direct current (HVDC) bus in aircraft electrical power systems. In this paper, a DAB DC-DC converter is designed to meet aviation requirements. The extended dual phase shifted control strategy is adopted, and a multi-objective genetic algorithm is applied to optimize its operating performance. Considering the three indicators of inductance current root mean square root (RMS) value, negative reverse power and direct current (DC) bias component of the current for the high frequency transformer as the optimization objectives, the DAB converter’s optimization model is derived to achieve soft switching as the main constraint condition. Optimized methods of controlling quantity for the DAB based on the evolution and genetic algorithm is used to solve the model, and a number of optimal control parameters are obtained under different load conditions. The results of digital, hard-in-loop simulation and hardware prototype experiments show that the three performance indexes are all suppressed greatly, and the optimization method proposed in this paper is reasonable. The work of this paper provides a theoretical basis and researching method for the multi-objective optimization of the power converter in the aircraft electrical power system.

Electrical and Thermal Effects of Fault Currents in Aircraft Electrical Power Systems With Composite Aerostructures

The upward trend for the use of electrical power on state-of-the-art aircraft is resulting in significant change to the design of power system architectures and protection systems for these platforms. There is a pull from the aerospace industry to integrate the electrical power system with the aircraft’s structural materials to form an embedded system, reducing the need for bulky cable harnesses. This directly impacts the fault response for ground faults and ultimately the development of appropriate protection systems. Such structural materials include composites such as carbon fiber reinforced polymer (CFRP). This paper presents the experimental capture and analysis of the response of CFRP to electrical fault current, which indicates the need for two distinct sets of electrical ground fault detection criteria for low and high resistance faults and identifies the threshold resistance for this distinction. By extrapolating these results to develop models of CFRP for use in transient simulation studies, the key electrical fault detection thresholds for speed, selectivity, and sensitivity for a dc system rail to ground fault through CFRP are identified. This provides the first set of key factors for electrical fault detection through CFRP, providing a platform for the design of fully integrated structural and electrical power systems, with appropriate electrical protection systems.

Generic functional modelling of multi-pulse auto-transformer rectifier units for more-electric aircraft applications

The Auto-Transformer Rectifier Unit (ATRU) is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced kVA ratings. Indeed, the ATRU has become a preferred AC/DC solution to supply power to the electric environment control system on-board future aircraft. In this paper, a general modelling method for ATRUs is introduced. The developed model is based on the fact that the DC voltage and current are strongly related to the voltage and current vectors at the AC terminals of ATRUs. In this paper, we carry on our research in modelling symmetric 18-pulse ATRUs and develop a generic modelling technique. The developed generic model can study not only symmetric but also asymmetric ATRUs. An 18-pulse asymmetric ATRU is used to demonstrate the accuracy and efficiency of the developed model by comparing with corresponding detailed switching SABER models provided by our industrial partner. The functional models also allow accelerated and accurate simulations and thus enable whole-scale more-electric aircraft electrical power system studies in the future.

Minimal Cut Sets-Based Reliability Evaluation of the More Electric Aircraft Power System

The More Electric Aircraft (MEA) stands for the direction of aviation development in the new era, and the reliability of power systems on the MEA has attracted widespread attention. Based on the characteristics of MEA power systems, an equivalent method of electrical topology structure is presented in this article, and evaluation method is proposed which shows the reliability of the overall system with the reliability of specific nodes. Firstly, electrical topology structure of a MEA power system is converted into a network node diagram according to the proposed equivalent method. Then, the minimal path sets of specific nodes are obtained by the adjacent matrix algorithm, and the low-order minimal cut sets of disjointed are obtained. After that, the actual failure rate of components is converted to node failure rate, and the reliability of the overall system is evaluated by operational reliability indexes of specific nodes. Finally, taking the MEA A380 as an example, this paper compares and analyzes the reliability of AC loads, DC loads, and key loads to verify the validity and feasibility of the proposed evaluation method. This evaluation system can predict the weak points existing in the MEA power system, as well as providing theoretical support for maintenance schedule.

Exploiting the synergy between aircraft architecture and electric power system in unmanned aerial vehicle through many-objective optimisation

This study addresses the preliminary design of a fixed-wing, tailsitter electric unmanned aerial vehicle (with vertical take-off and landing capability) by optimising the size of the powertrain components together with the main aircraft design specification. To this scope, different optimisation problems are considered, with two, three and four objective functions, respectively. The results of the optimisation are used not only to compare the performance of different optimisation algorithms when increasing the number of goals, but also to discuss the synergy between architecture and power systems optimisation.

Methods for building ATRU real‐time model based on different application scenarios

This study introduces three methods for building an auto-transformer rectifier units (ATRU) real-time model based on different application scenarios. Real-time models run on an advanced real-time simulator that has the capability to leverage central processing units and field programming gate arrays. In the first section, the disadvantages of the off-line simulation are explained and the solution is offered through real-time simulation. In the second section, applications of real-time simulation in a more electric aircraft (MEA) electric power system will be presented. In the third section, methods to build the ATRU real-time model are illustrated based on requirements and different scenarios. Simulations are conducted to demonstrate the agreement between the results and analysis.

Finite state machine control for aircraft electrical distribution system

This study deals with the development of new control logic for more electric aircraft (MEA) electrical power systems (EPSs). A key aspect of the MEA concept is that traditional pneumatic and hydraulic loads are replaced by electrical equivalents. These new electrical systems are more reliable, highly efficient, and easier to replace or maintain. However, as the number of on-board electrical loads increases the electrical distribution systems on-board are becoming more and more complex. As a result, the control system needs to be adapted and improved in order to allow better manage the overall electrical energy flow, provide faster computational operations, and ensure operation of safety-critical loads under all fault scenarios. This study first gives a brief analysis of the different electrical system topologies before outlining potential control strategies which may be applicable to future MEA EPSs. A new control concept for MEA EPSs is then investigated and considered as a potential substitute of the classical control systems. Finally, a model of the newly proposed logic is implemented and simulated showing how it is able to select and apply a correct reconfiguration of the electrical system under different operating conditions.

Exploiting the synergy between aircraft architecture and electric power system in unmanned aerial vehicle through many-objective optimisation

This study addresses the preliminary design of a fixed-wing, tailsitter electric unmanned aerial vehicle (with vertical take-off and landing capability) by optimising the size of the powertrain components together with the main aircraft design specification. To this scope, different optimisation problems are considered, with two, three and four objective functions, respectively. The results of the optimisation are used not only to compare the performance of different optimisation algorithms when increasing the number of goals, but also to discuss the synergy between architecture and power systems optimisation.

A Comparative Study of Neural Network and Fuzzy Logic Control Based Active Shunt Power Filter for 400 Hz Aircraft Electric Power System

Constant Instantaneous Power Control Strategy for extracting reference currents for shunt active power filters have been modified using Artificial Neural Network & Fuzzy logic control based controller and their performances have been compared. The acute analysis of Comparison of the compensation capability based on THD and speed will be done, and recommendations will be given for the choice of technique to be used. The simulated results using MATLAB model are shown, and they will undoubtedly prove the importance of the proposed control technique of aircraft shunt APF.

Overview and analysis of PM starter/generator for aircraft electrical power systems

More Electrical Aircraft (MEA) which replaces the hydraulic and pneumatic power by electrical power leads to reducing emissions and fuel consumption. The MEA concept has led to a growing use of the starter/generator (S/G) system. Permanent magnet (PM) machines have been gaining interests for aircraft S/G system application over the last few years. This is mainly due to the several advantages, including high power density, high efficiency and high speed ability. The shortcoming of the PM machines is the de-excitation problem in case of a failure, which is a main issue for the aircraft application. However, by using a PM machine with high reactance or multiphase configuration, the fault-tolerant ability can be improved. In terms of the aircraft S/G system, this paper is going to present a comprehensive analysis of PM machines. Firstly, the state-of-the-art of PM starter/generator (PMS/G) is summarized and the basic structure of PMS/G system is analyzed. Next, key technologies of the PMS/G system are summarized and analyzed. Finally, a flux weakening fault protection strategy that is used to suppress the turn-to-turn short circuit (SC) current is studied, simulated and verified. With the breakthrough of key technologies based on the development of high temperature electromagnetic material and high temperature power electronics, the PMS/G will be a potential candidate for aircraft S/G system including the embedded power generation system.

Control Design for PMM-Based Generator Fed by Active Front-End Rectifier in More-Electric Aircraft

The future aircraft electrical power system is expected to be more efficient, safer, simpler in servicing and easier in maintenance. As a result, many existing hydraulic and pneumatic power driven systems are being replaced by their electrical counterparts. This trend is known as a move towards the More-Electric Aircraft (MEA). As a result, a large number of new electrical loads have been introduced in order to power many primary functions including actuation, de-icing, cabin airconditioning, and engine start. Therefore electric power generation systems have a key role in supporting this technological trend. Advances in modern power electronics allow the concept of starter/generator (S/G) which enables electrical engine start and power generation using the same electrical machine. This results in substantial improvements in power density and reduced overall weight. One of the potential S/G solutions is to employ a permanent magnet machine (PMM) controlled by active front-end rectifier (AFE). Operation of the PMM as a generator at wide range of speed that is dictated by the engine and electrical loads connected to the aircraft bus require careful design of the controllers. Corresponding plant models are derived and verified with simulations using developed models in Matlab/Simulink. The relevant controllers are designed based on the derived plants and operating points. The controllers are tested with Simulink models and experimentally using a scaled prototype of the investigated generator system.

Sandwich-structured polymer nanocomposites with high energy density and great charge–discharge efficiency at elevated temperatures

The demand for a new generation of high-temperature dielectric materials toward capacitive energy storage has been driven by the rise of high-power applications such as electric vehicles, aircraft, and pulsed power systems where the power electronics are exposed to elevated temperatures. Polymer dielectrics are characterized by being lightweight, and their scalability, mechanical flexibility, high dielectric strength, and great reliability, but they are limited to relatively low operating temperatures. The existing polymer nanocomposite-based dielectrics with a limited energy density at high temperatures also present a major barrier to achieving significant reductions in size and weight of energy devices. Here we report the sandwich structures as an efficient route to high-temperature dielectric polymer nanocomposites that simultaneously possess high dielectric constant and low dielectric loss. In contrast to the conventional single-layer configuration, the rationally designed sandwich-structured polymer nanocomposites are capable of integrating the complementary properties of spatially organized multicomponents in a synergistic fashion to raise dielectric constant, and subsequently greatly improve discharged energy densities while retaining low loss and high charge-discharge efficiency at elevated temperatures. At 150 °C and 200 MV m(-1), an operating condition toward electric vehicle applications, the sandwich-structured polymer nanocomposites outperform the state-of-the-art polymer-based dielectrics in terms of energy density, power density, charge-discharge efficiency, and cyclability. The excellent dielectric and capacitive properties of the polymer nanocomposites may pave a way for widespread applications in modern electronics and power modules where harsh operating conditions are present.