Electric Power Systems and Components for Electric Aircraft

Electric aircraft have gained increasing attention in recent years due to their potential for environmental and economic benefits over conventional airplanes. In order to offer competitive flight times and payload capabilities, electric aircraft power systems (EAPS) must exhibit extremely high efficiencies and power densities. While advancements in enabling technologies have progressed the development of high performance EAPS, further research is required. One challenge in the design of EAPS is determining the best topology to be employed. This work proposes a new graph theory based method for the optimal design of EAPS. This method takes into account data surveyed from a large set of references on commonly seen components including electric machines, power electronics and jet engines. Thousands of design candidates are analyzed based on performance metrics such as end-to-end system efficiency, overall mass, and survivability. It is also shown that sensitivity analysis may be used to systematically evaluate the impact of components and their parameters on various aspects of the architecture design. Once an EAPS architecture has been selected, further, detailed, validation of the power system is required. In these EAPS, many subsystems exist with timescales varying from minutes to hours when considering the aerodynamics, to nanosecond dynamics in the power electronics. This dissertation presents a multiphysics co-simulation framework for the evaluation of EAPS with a unique decoupling method to reduce simulation time without sacrificing detail. The framework has been exemplified on a case study of a 500kW all-electric aircraft, including models for aerodynamics, energy storage, electric motors and power electronics. Electric machines for aviation propulsion must meet several performance requirements, including a constant power speed range (CPSR) of approximately thirty percent above rated speed. This operation is traditionally achieved through the flux weakening technique with an injection of negative d-axis current. However, the degree of CPSR achievable through flux weakening is a strong function of the back emf and d-axis inductance. This dissertation reviews alternative methods for CPSR operation in machines with low inductance. A new method of current weakening has been proposed to address this challenge, involving reducing the machine\u27s current inversely proportional to the operating speed, maintaining constant power through the extended speed range. One benefit of the proposed method is that all current is maintained in the q-axis, maintaining maximum torque per ampere operation. Coreless axial flux permanent magnet (AFPM) machines have recently gained significant attention due to their specific form factor, potentially higher power density and lower losses. Coreless machine designs promise high efficiency particularly at higher speeds, due to the absence of a ferromagnetic core. In this dissertation, coreless AFPM machines with PCB stators are investigated as candidates for propulsion in electric aircraft applications. Two PCB stator design variations are presented with both simulation and experimental results

A review on power electronics technologies for electric mobility

Concerns about greenhouse gas emissions are a key topic addressed by modern societies worldwide. As a contribution to mitigate such effects caused by the transportation sector, the full adoption of electric mobility is increasingly being seen as the main alternative to conventional internal combustion engine (ICE) vehicles, which is supported by positive industry indicators, despite some identified hurdles. For such objective, power electronics technologies play an essential role and can be contextualized in different purposes to support the full adoption of electric mobility, including on-board and off-board battery charging systems, inductive wireless charging systems, unified traction and charging systems, new topologies with innovative operation modes for supporting the electrical power grid, and innovative solutions for electrified railways. Embracing all of these aspects, this paper presents a review on power electronics technologies for electric mobility where some of the main technologies and power electronics topologies are presented and explained. In order to address a broad scope of technologies, this paper covers road vehicles, lightweight vehicles and railway vehicles, among other electric vehicles.This work has been supported by FCT – Fundação para a Ciência e Tecnologia with-in the Project Scope: UID/CEC/00319/2020. This work has been supported by the FCT Project DAIPESEV PTDC/EEI-EEE/30382/2017, and by the FCT Project new ERA4GRIDs PTDC/EEI-EEE/30283/2017. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT

A review of electrical motor topologies for aircraft propulsion

This paper provides a review of the state-of-the art in aircraft electrical propulsion (AEP). Initially, the limitations of on-board energy storage devices are highlighted and contextualised. The definitions of useful measures for determining the suitability of motor design, namely specific power and motor torque per unit rotor volume (TRW), are discussed and relevant examples are provided. The classifications of motors used for terrestrial vehicle applications are reviewed and their limitations highlighted regarding their suitability to AEP applications. A discussion on motor configurations for aerospace applications is provided which includes: synchronous motor stator winding configurations; axial flux motor configurations and the causes of energy losses. Additionally, the topologies and performance characteristics of existing aerospace motor technologies are examined. It was concluded that electrical motors provide an ideal means for achieving aircraft propulsion and that higher motor speeds are likely to be required for future commercial aircraft motor designs

Multiport Bidirectional SRM Drives for Solar-Assisted Hybrid Electric Bus Powertrain With Flexible Driving and Self-Charging Functions

The hybrid electric bus (HEB) presents an emerging solution to exhaust gas emissions in urban transport. This paper proposes a multiport bidirectional switched reluctance motor (SRM) drive for solar-assisted HEB (SHEB) powertrain, which not only improves the motoring performance, but also achieves flexible charging functions. To extend the driving miles and achieve self-charging ability, photovoltaic (PV) panels are installed on the bus to decrease the reliance on fuelsbatteries and charging stations. A bidirectional front-end circuit with a PV-fed circuit is designed to integrate electrical components into one converter. Six driving and five charging modes are achieved. The dc voltage is boosted by the battery in generator control unit (GCU) driving mode and by the charge capacitor in battery driving mode, where the torque capability is improved. Usually, an extra converter is needed to achieve battery charging. In this paper, the battery can be directly charged by the demagnetization current in GCU or PV driving mode, and can be quickly charged by the PV panels and GCUAC grids at SHEB standstill conditions, by utilizing the traction motor windings and integrated converter circuit, without external charging converters. Experiments on a three-phase 128 SRM confirm the effectiveness of the proposed drive and control scheme

Development of a Hybrid-Electric Aircraft Propulsion System Based on Silicon Carbide Triple Active Bridge Multiport Power Converter

Constrained by the low energy density of Lithium-ion batteries with all-electric aircraft propulsion, hybrid-electric aircraft propulsion drive becomes one of the most promising technologies in aviation electrification, especially for wide-body airplanes. In this thesis, a three-port triple active bridge (TAB) DC-DC converter is developed to manage the power flow between the turbo generator, battery, and the propulsion motor. The TAB converter is modeled based on the emerging Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) modules operating at high switching frequency, so the size of the magnetic transformer can be significantly reduced. Different operation modes of this hybrid-electric propulsion drive based on the SiC TAB converter are modeled and simulated to replicate the takeoff mode, cruising mode, and regenerative charging mode of a typical flight profile. Additionally, soft switching is investigated for the TAB converter to further improve the efficiency and power density of the converter, and zero voltage switching is achieved at heavy load operating conditions. The results show that the proposed TAB converter is capable of achieving high efficiency during all stages of the flight profile

Recent Technologies and Control Methods for Electric Power Systems in More Electric Aircrafts: A Review

This paper is aimed at discussing the current trends in the design of Electric Power Systems (EPS) architectures which are intended to be implemented in More Electric Aircrafts (MEAs). Various EPS architectures such as HVAC, HVDC, hybrid HVAC/HVDC etc are studied and compared. Various control techniques which are implemented in order to control the EPS are also reviewed and they are compared on the basis of power quality, ease of installation and maintenance, possibility of future expansion of EPS, need of active power filters and so on. On the basis of the evaluation of various EPS architectures, the need of fuel cell installation in the EPS to be used for MEAs is explained and various ways to incorporate the fuel cell in the said EPS are discussed. Further the need of DC to DC converters in the power grid of a MEA is discussed and various possible choices for the topologies of DC to DC converters are compared on the basis of the parameters such as efficiency, transient response, reliability, electromagnetic emissions, size, weight and so on. Moreover, various controllers such as PI controller, PID controller, Sliding Mode Controller etc which can be used for a closed loop control of DC to DC converters are discussed

Power Electronics Powertrain Architectures for Hybrid and Solar Electric Airplanes with Distributed Propulsion

Distributed propulsion in aircraft has been shown to increase reliability and benefit aerodynamic performance. This paper discusses power electronic architectures and proposes control schemes suitable for distributed propulsion in hybrid and electric airplanes. Hybrid electric airplanes include permanent magnet synchronous generators driven by jet engines. The output of the generators is connected to the propulsion motors through back to back voltage source converters. Batteries, connected to the DC bus through buck-boost converters, are used to provide additional power to the propulsion motors during take off and climb. In the case of electric airplanes, the jet engine-permanent magnet generator system is replaced by solar photovoltaic (PV) panels. The output of the solar PV system is controlled such that it operates at its maximum power point, and power is provided to batteries and propulsion motors. Simulation results on both hybrid and solar electric systems are presented

Discussion on Electric Power Supply Systems for All Electric Aircraft

The electric power supply system is one of the most important research areas within sustainable and energy-efcient aviation for more- and especially all electric aircraft. This paper discusses the history in electrication, current trends with a broad overview of research activities, state of the art of electrication and an initial proposal for a short-range aircraft. It gives an overviewof the mission prole, electrical sources, approaches for the electrical distribution system and the required electrical loads. Current research aspects and questions are discussed, including voltage levels, semiconductor technology, topologies and reliability. Because of the importance for safety possible circuit breakers for the proposed concept are also presented and compared, leading to a initial proposal. Additionally, a very broad review of literature and a state of the art discussion of the wiring harness is given, showing that this topic comes with a high number of aspects and requirements. Finally, the conclusion sums up the most important results and gives an outlook on important future research topics

Design and analysis of three phase inverter based Solar PV powered single switch Buck-Boost converter with reduced THD for industrial applications

The development of economical and sustainable eco-friendly renewable source powered power electronic converters have become more attractive in various areas such as automotive, household and industrial applications etc., Bucking and boosting of voltage according to the requirement is also much needed. So, this work proposes a solar PV powered single switch buck-boost converter which reduces implementation cost, minimal voltage and current stress across the capacitors and diodes and less switching power losses. The work structure comprises of solar PV source with modified P and O algorithm based MPPT, single switch buck-boost dc-dc converter, battery backup to store excess energy, three phase inverter with sinusoidal PWM to find optimal switching angles for harmonic control and 3Φ induction motor load. Here reduction of THD is applied to the line to line voltage of the inverter. Performance analysis of the proposed circuit is done using MATLAB/SIMULINK platform. A detailed steady state analysis of the dc-dc converter topology is also analyzed to system stability. The proposed single switch buck-boost converter is designed to provide an output voltage and current of 363V, 45.5A DC from 520V, 35A PV array. The designed converter is then employed to run a three phase full bridge inverter with 440V, 15A AC. From the simulation results, it is found that the solar powered single switch buck-boost with MPPT is stable, efficient with minimal losses and less THD with better quality output