Single-Electrical-Port Control of Cascaded Doubly-Fed Induction Machine for EV/HEV Applications

A single-electrical-port control scheme, for four-quadrant operation of cascaded doubly-fed induction machine (CDFIM), which has long been conceived as a motor or generator only suitable for limited two-quadrant operation, is proposed and theoretically demonstrated. The drive system is configured as a master/slave architecture, that is, the power winding is supplied with a constant-voltage constant-frequency inverter, termed as the master inverter, in an open-loop way, while the control winding is fed by a closed-loop field-oriented-controlled (FOC) variable-voltage variable-frequency inverter, termed as slave inverter. With this configuration, the control emphasis is placed on the slave inverter, yielding reduced control complexity and cost, and the inaccuracy of flux estimation in conventional FOC for singly-fed induction machines is avoided at very low or even zero speed. It is found that the doubly-fed synchronous operation of the CDFIM can achieve wider constant torque region and constant power region than the singly-fed synchronous operation. Simulations and experimental results are provided to verify the proposed drive configuration and control algorithm.