Multi-port power conversion systems for the more electric aircraft

In the framework of the More Electric Aircraft (MEA), weight reduction and energy efficiency constitute the key figures. In addition to these requirements, the safety and the continuity of operation is of critical importance. These sets of desired feature are in disagreement, because the redundancy needed to guarantee the safety of operation implies necessarily in additional weight. Several concepts of the electrical power distribution systems have been proposed, in this manuscript, an approach based on the widespread use of multi-port power converters both for the DC/DC and for the DC/AC stages is proposed. These two technologies allows for a ring distribution of the electrical power whereas the galvanic isolation is still kept. Simulation and experimental results show the feasibility of the concept in common and fault operation conditions

Assessment of lightweight mobile nuclear power systems

A review was made of lightweight mobile nuclear power systems (LMNPS). Data cover technical feasibility studies of LMNPS and airborne vehicles, mission studies, and non-technical conditions that are required to develop and use LMNPS

A multi-port power conversion system for the more electric aircraft

In more electric aircraft (MEA) weight reduction and energy efficiency constitute the key figures. Additionally, the safety and continuity of operation of its electrical power distribution system (EPDS) is of critical importance. These sets of desired features are in disagreement with each other, because higher redundancy, needed to guarantee the safety of operation, implies additional weight. In fact, EPDS is usually divided into isolated sections, which need to be sized for the worst-case scenario. Several concepts of EPDS have been investigated, aiming at enabling the power exchange among separate sections, which allows better optimization for power and weight of the whole system. In this paper, an approach based on the widespread use of multi-port power converters for both DC/DC and DC/AC stages is proposed. System integration of these two is proposed as a multiport power conversion system (MPCS), which allows a ring power distribution while galvanic isolation is still maintained, even in fault conditions. Thus, redundancy of MEA is established by no significant weight increase. A machine design analysis shows how the segmented machine could offer superior performance to the traditional one with same weight. Simulation and experimental verifications show the system feasibility in both normal and fault operations

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

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 Multi-port Smart Transformer for Green Airport Electrification

Green transportation and renewable energy production have attracted a global attention due to the needs of decreasing the environmental impact and still sustain increased energy needs. In this framework, the aircraft and airports are facing a profound renovations towards green technologies, among which the electrical ones are playing a central role. This paper explores how a Smart Transformer can upgrade the existing airport power system, enabling an efficient interface for renewable energy, electric vehicles and the future hybrid/electric aircraft, substituting the ground power units and enabling a smarter behavior of the electrical grid

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 34)

Abstracts are provided for 124 patents and patent applications entered into the NASA scientific and technical information systems during the period July 1988 through December 1988. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or patent application

Conceptual design studies of candidate V/STOL lift fan commercial short haul transport for 1980 - 1985 V/STOL lift fan study

Conceptual designs of V/STOL lift fan commercial short haul transport aircraft for the 1980-85 time period were studied to determine their technical and economic feasibility. The engine concepts included both integral and remote fans. The scope of the study included definition of the hover control concept for each propulsion system, aircraft design, aircraft mass properties, cruise performance, noise and ride qualities evaluation. Economic evaluating was also studied on a basis of direct operating costs and route structure

Nuclear air cushion vehicles

The state-of-the-art of the still-conceptual nuclear air cushion vehicle, particularly the nuclear powerplant is identified. Using mission studies and cost estimates, some of the advantages of nuclear power for large air cushion vehicles are described. The technology studies on mobile nuclear powerplants and conceptual ACV systems/missions studies are summarized

Fiber optic control system integration

A total fiber optic, integrated propulsion/flight control system concept for advanced fighter aircraft is presented. Fiber optic technology pertaining to this system is identified and evaluated for application readiness. A fiber optic sensor vendor survey was completed, and the results are reported. The advantages of centralized/direct architecture are reviewed, and the concept of the protocol branch is explained. Preliminary protocol branch selections are made based on the F-18/F404 application. Concepts for new optical tools are described. Development plans for the optical technology and the described system are included