Modular Modeling and Distributed Control of Permanent-Magnet Modular Motor Drives (MMDs) for Electric Aircraft Propulsion

Abstract

Permanent magnet (PM) modular motor drives (MMDs) have been recognized as promising candidate machine drive propulsion units in electrified aircraft due to their high power density, high efficiency, and high fault tolerance. Heterarchical, distributed, and modular control schemes are preferred to enhance the system reliability by eliminating single points of failure (SPOFs) from controllers. To facilitate modular machine control design and analysis, a generalized module-level machine analysis and modeling framework has been developed. Module-level machine analysis reveals intra-module unbalanced inductances and inter-module unbalanced cross-coupled fluxes that differ from conventional machines due to asymmetric mutual slot leakage flux couplings among the modules. An asymmetric module-level machine model has been developed by using complex vectors and conjugate complex vectors. Due to the asymmetry, balanced three-phase module voltage excitation induces both positive and negative sequence module current responses when the modules are not evenly loaded. This feature deteriorates the inter-module independence of MMDs, especially under fault conditions where maximum inter-module independence is desired. A modular control with a negative sequence regulator is proposed to eliminate the undesired negative sequence component under uneven loading and fault conditions in order to achieve the desired high level of inter-module independence.