Turbo-electric Distributed Aircraft Propulsion: Microgrid Architecture and Evaluation for ECO-150

Abstract

This work describes the architecture and evaluation of a turbo-electric distributed propulsion microgrid for ECO-150, a NASA funded 154 passenger subsonic fixed wing commercial transport aircraft concept for entry into service by 2035. Three different microgrid types are considered: ac synchronous distribution, dc distribution, and a hybrid approach. A high level architecture for each grid type is proposed, considering requirements for single point failure accommodation, redundancy and reconfigurability, and electrical protection. Component sizing models were developed for rotating electrical machines, power converters, distribution, and protection equipment, targeting a technology readiness level (TRL) of TRL-6 by 2025. These tools are combined to evaluate the mass and efficiency metrics for each microgrid type. Sensitivity sweeps on grid voltage and frequency were completed in order to determine optimal choices for both parameters. Results indicate that microgrid performance metrics are optimized for ECO-150 near 6 kilovolts (kV) and 1 kilohertz (kHz), with the dc and hybrid grids having a greater sensitivity to voltage than the ac grid. Advantages of the dc and hybrid grids include ability to provide powered yaw, and ability to incorporate energy storage. However, powered yaw control was investigated and determined to be less effective than a conventional tail on a per mass basis. After accounting for the mass of the associated thermal management system (TMS), the dc grid emerges as the lowest mass option above 3 kV, followed by the ac and the hybrid grid. However, ac grid achieves a transmission efficiency 2-3% higher than the dc grid, which will have system level effects on fuel burn, fuel weight, and overall propulsive efficiency. For near term practical implementation of turbo-electric distributed propulsion, the ac synchronous system should be considered seriously as a strong candidate.