Performance comparison of transfer switch topologies in switched-doubly-fed machine drives

Switched doubly-fed machines (DFM) creates variable speed drives with reduced power electronics requirements compared to shaft power, and with the additional benefit of controllable stator power factor. A solid-state transfer switch is a critical component of a switched-DFM drive that not only allows seamless shaft control across the full speed range but also permits effective grid interaction. This paper presents and compares two transfer switch topologies - twelve-thyristor-based and eight-thyristor-based that reconfigures the DFM connections on-the-fly with different shaft torque-speed demands. Reducing the number of thyristors allows the operation of the DFM with lesser commutation constraints. Appropriate control input is derived that maximizes the damping of the stator flux during the mode transition.