Flight-critical load failure analysis in HVDC More-Electric Aircraft applications

The electrification of aircraft is a key and proven means of realising decarbonisation. A key pillar of this, the More-Electric Aircraft (MEA), has been shown to be a viable alternative to conventional aircraft where traditionally pneumatic and hydraulic systems are replaced with electrical equivalent systems such that efficiency gains, noise, carbon emission and mass reductions are achieved. With electrical systems performing new flight-critical roles on-board MEA, and the Power Electronic Converter (PEC) being a core technology in these systems, there has been increased interest in recent years in better characterising and improving the reliability of PECs. Using Fault-Tree Analysis (FTA) and Reliability Block Diagram (RBD) methods, this paper presents a study of the contribution of the PEC failure rates to the reliability of flight-critical loads in a concept High Voltage Direct Current (HVDC) aircraft application. It is shown that whilst the failure rate of PECs will typically shape the overall failure rate of electrical systems and subsystems, the installed redundancy in aircraft Electrical Power System (EPS) mitigates the risk of unacceptably high rates of failure in flight critical loads, even if the aircraft is dispatched in a non-full-up configuration. Moreover, the paper illustrates how the greatest gains in these load systems’ reliability can be realised through improvements in the reliability of the PEC interfaces to these load subsystems, where there is naturally less system redundancy.