Solid-State Transfer Switch Topologies for a Switched Doubly Fed Machine Drive

Switched doubly fed machines (DFM) enable the creation of variable speed drives with reduced power electronics requirements compared to shaft power, and with the additional benefit of controllable stator power factor. A transfer switch is a critical component of a switched-DFM drive, permitting reconfiguration of the stator power connections. A solid-state transfer switch not only allows seamless shaft control across the full-speed range but also permits effective grid interaction. This paper presents and compares different transfer switch topologies that can reconfigure the DFM connections on-the-fly as shaft speed demands vary. Constraints on operating conditions are derived that can allow DFM mode transitions without any additional commutation circuitry. Experiments demonstrate the performance of the transfer switch under different operating conditions.