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Journal Article

A Holistic Approach towards Optimizing Energy Storage Response during Network Faulted Conditions within an Aircraft Electrical Power System

2012-10-22
2012-01-2229
Within aircraft electrical network designs, energy storage systems (ESS) provide a means of decoupling the electrical-mechanical interactions between the aircraft electrical power system and the aircraft engine, meeting peak load demand and maintaining power quality during network disturbances and variable load conditions. Within the literature to date, control and management strategies of ESSs for such applications has primarily focused on normal network operation with only limited coverage on the behavior of such technologies under abnormal conditions and the subsequent impact on the operation of the wider power system. Through modeling and simulation of a generic aircraft electrical system, this paper will highlight the potential risks of the inherent, sub-optimal operation of certain existing control strategies during fault conditions.
Technical Paper

Aircraft Power and Propulsion Systems-Research Challenges and Opportunities for Electrical Systems

2012-10-22
2012-01-2212
NASA has compiled a set of research goals for five year periods starting 2015, 2020 and 2025 for three classes of future subsonic aircraft, N+1 (2015), N+2 (2020) and N+3 (2025). With the intention of progressively making reductions in noise emissions, greenhouse gas emissions, fuel burn and energy consumption at each of these points to achieve Technology Readiness Levels (TRL's) of between 4 and 6. In the last few years much progress has been made towards achieving these goals through the development of new technologies and designs. This paper assesses how the current More Electric Aircraft (MEA) design concepts are advancing to allow the near term, N+1 goals of reducing 32 dB of noise emissions, 60% of the landing and take-off (LTO) NOx emissions, 55% of cruise emissions and 33% saving of fuel burn and energy consumption, relative to single aisle B737-800, could be met and eventually surpassed.
Technical Paper

Protection System Considerations for DC Distributed Electrical Propulsion Systems

2015-09-15
2015-01-2404
Distributed electrical propulsion for aircraft, also known as turbo-electric distributed propulsion (TeDP), will require a complex electrical power system which can deliver power to multiple propulsor motors from gas turbine driven generators. To ensure that high enough power densities are reached, it has been proposed that such power systems are superconducting. Key to the development of these systems is the understanding of how faults propagate in the network, which enables possible protection strategies to be considered and following that, the development of an appropriate protection strategy to enable a robust electrical power system with fault ride-through capability. This paper investigates possible DC protection strategies for a radial DC architecture for a TeDP power system, in terms of their ability to respond appropriately to a DC fault and their impact on overall system weight and efficiency.
Technical Paper

Failure Analysis of a Turboelectric Distributed Propulsion Aircraft Electrical Network: A Case Study

2015-09-15
2015-01-2403
A number of concepts have been proposed to meet future aircraft performance goals. One such concept under consideration is Turboelectric Distributed Propulsion (TeDP) featuring a large number of superconducting motors powered by two superconducting generators placed on each wingtip and connected through a DC distribution network. A key aspect in any design concept is the ability to prove that the system will exhibit a satisfactory reliability for all intended operating conditions. A common tool to support the calculation of failure rates and reliability is Fault Tree Analysis (FTA), and this will be utilized within this paper. The paper undertakes an architectural level FTA on a NASA proposed TeDP architecture to identify any significant factors contributing to the failure rate of key functionalities within the network.
Technical Paper

Evaluation of Paralleled Generation Architectures for Civil Aircraft Applications

2015-09-15
2015-01-2407
The aviation industry has witnessed a technological shift towards the More Electric Aircraft (MEA) concept. This shift has been driven by a number of perceived benefits including performance optimization and reduced life-cycle costs. Increased electrification within MEA has made aircraft electrical networks larger and more complex and this necessitates an increased electrical power offtake from the engine. The paralleling of multiple generation sources across the aircraft is one potential design approach which could help improve engine operability and fuel efficiency within more-electric aircraft platforms. Accordingly, this paper will investigate options for the realization of paralleled generation systems within the context of current design and certification rules. The paper first illustrates, through simulation, that MIL-STD-704F voltage envelopes may be breached for some interconnected electrical architectures under fault conditions.
Technical Paper

AC/DC Converter with DC Fault Suppression for Aircraft +/− 270 VDC Distribution Systems

2015-09-15
2015-01-2411
The increasing electrical demand in commercial and military aircraft justifies a growing need for higher voltage DC primary distribution systems. A DC system offers reduced power losses and space savings, which is of major importance for aircraft manufacturers. At present, challenges associated with DC systems include reliable fast acting short circuit protection. Solid State Contactors (SSC) have gained wide acceptance in traditional 28 VDC secondary systems for DC fault interruption. However, the reliable operation at higher operating voltages and currents requires further technology maturation. This paper examines a supporting method to SSC for more reliable fault mitigation by investigating bidirectional AC/DC converter topology with DC fault current blocking capability. Replacement of semiconductor switches with full bridge cells allows instant reversal of voltage polarities to limit rapid capacitor discharge and machine inductive currents.
Technical Paper

Modular and Reconfigurable Transient Modeling and Simulation Design Support Tool for MEE/MEA Power Systems

2016-09-20
2016-01-2031
There is a well-recognised need for robust simulation tools to support the design and evaluation of future More-Electric Engine and Aircraft (MEE/MEA) design concepts. Design options for these systems are increasingly complex, and normally include multiple power electronics converter topologies and machine drive units. In order to identify the most promising set of system configurations, a large number of technology variants need to be rapidly evaluated. This paper will describe a method of MEE/MEA system design with the use of a newly developed transient modeling, simulation and testing tool aimed at accelerating the identification process of optimal components, testing novel technologies and finding key solutions at an early development stage. The developed tool is a Matlab/Simulink library consisting of functional sub-system units, which can be rapidly integrated to build complex system architecture models.
Journal Article

Impact of Engine Certification Standards on the Design Requirements of More-Electric Engine Electrical System Architectures

2014-09-16
2014-01-2119
The development of the More-Electric Engine (MEE) concept will see an expansion in the power levels, functionality and criticality of electrical systems within engines. However, to date, these more critical electrical systems have not been accounted for in existing engine certification standards. To begin to address this gap, this paper conducts a review of current engine certification standards in order to determine how these standards will impact on the design requirements of More-Electric Engine (MEE) electrical system architectures. The paper focuses on determining two key architectural requirements: the number of individual failures an architecture can accommodate and still remain functional and the rate at which these failures are allowed to occur.
Journal Article

An Optimisation Based Design Approach for Aircraft Electrical Power Systems

2014-09-16
2014-01-2121
The More Electric Aircraft (MEA) concept coupled with recent advances in power electronics has seen an increasing number of on-board tasks being facilitated by electrical power, as opposed to more conventional hydraulic, mechanical and pneumatic power systems. The migration to a predominantly electrical power system is expected to bring significant cost and performance benefits; however, the devices used to facilitate this change have led to an increasingly complicated electrical power system with heightened levels of system sophistication and interdependence. These developments have the potential to drastically alter the solution space of all feasible aircraft Electrical Power System (EPS) designs. The technological advancements facilitating the MEA progression have allowed for a broader range of design solutions to exist that increase the size of the solution space. Meanwhile increasing system sophistication has led to an increasingly non-linear and complex solution space.
Journal Article

A Method for the Evaluation of the Effectiveness of Turboelectric Distributed Propulsion Power System Architectures

2014-09-16
2014-01-2120
Radical new electrically propelled aircraft are being considered to meet strict future performance goals. One concept design proposed is a Turboelectric Distributed Propulsion (TeDP) aircraft that utilises a number of electrically driven propulsors. Such concepts place a new and significant reliance on an aircraft's electrical system for safe and efficient flight. Accordingly, in addition to providing certainty that supply reliability targets are being met, a contingency analysis, evaluating the probability of component failure within the electrical network and the impact of that failure upon the available thrust must also be undertaken for architecture designs. Solutions that meet specified thrust requirements at a minimum associated weight are desired as these will likely achieve the greatest performance against the proposed emissions targets.
Technical Paper

Defining Requirements for the Implementation of Interconnected Generation in Future Civil Aircraft

2013-09-17
2013-01-2125
In addition to providing thrust, the engines on conventional civil jet airliners generate power for on-board systems and ancillary loads in the form of pneumatic, hydraulic and electrical power. Reduced fuel-burn and efficiency targets have driven the move towards More Electric Aircraft (MEA) technology which seeks to replace hydraulic and pneumatic loads with electrical equivalents. This technological shift, in conjunction with a growing electrical power load per passenger in general, has greatly increased the electrical power demands of aircraft in recent years - over 1 MVA for the Boeing 787 for example. With increasing fuel prices, there is a growing need to optimise efficiency of power extraction from the aircraft engines for the electrical system and loads. In particular, the utilisation of multi-shaft power off-takes, interconnected generation and power sharing between shafts is thought to offer potentially significant engine operability and fuel efficiency benefits.
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