Discussion on “A Modular Speed-Drooped System for High Reliability Integrated Modular Motor Drives”

This note studies stability of an integrated modular motor drive (IMMD) under the parallel operation scheme proposed in [1]. The IMMD consists of multiple identical motors, rotors of which are coupled with each other rigidly to collectively drive a common shaft. The objective of the parallel operation is to achieve speed regulation and load torque sharing. According to the experimental result provided, both speed regulation and load torque sharing properties are achieved by the parallel operation scheme. However, the stability analysis of this note reveals that the load torque sharing dynamics of EVIMD is marginally stable under the operation scheme in general. This note further shows that, if appropriately implemented with a common desired speed set -point restorer, the parallel operation scheme ensures stability of the IMMD.