Seamless grid interaction for a switched doubly-fed machine propulsion drive

Switched doubly-fed machine (DFM) drives can provide shaft speed control over a wide range without the need for a full power converter. Seamless shaft behavior across the complete speed range is achieved using a thyristor-based transfer switch in the stator of the DFM and appropriate control in the rotor converter. The drive must also operate without glitch with respect to the ac source. The seamless grid interaction is critical in applications such as in ship propulsion, where the drive may consume a major share of the generated power. This paper presents a coordinated control of the rotor converter that can ensure seamless operation for the switched-DFM drive with respect to the ac source. A laboratory setup emulating a ship microgrid is used to demonstrate the drive performance under different loading conditions.