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Electric propulsion is widely used in ship propulsion systems, and multiphase machines are gaining increasing popularity because of their fault-tolerant ability, high power density, and reduced torque ripple. This study concentrates on the tandem ship propulsion configuration with two 15-phase induction machines (IMs) fixed on the same shaft. Based on fieldoriented control and reconfiguration fault-tolerant control for the single 15-phase IM, the master-slave coordinated control strategy is designed for the tandem motors, which can not only achieve power allocation between two motors during normal operation, but also minimise the total stator copper loss of the two motors and maximise the propulsion output power ability during fault-tolerant operation. Experiment results from a ship propulsion experimental platform verify the effectiveness of the proposed control strategies.

This paper proposes optimized control methods for global minimum backflow power based on a triple-phase-shift (TPS) control strategy. Three global optimized methods are derived to minimize the backflow power on the primary side, on the secondary side and on both sides, respectively. Backflow power transmission is just a portion of non-active power transmission in a dual active bridge (DAB) converter. Non-active power transmission time is proposed in this paper, which unifies zero power transmission and backflow power transmission. Based on the proposed index, an optimized control method is derived to achieve both the maximum effective power transmission time and minimum current stress of DAB at the same time. A comparative analysis is performed to show the limitations of the minimum backflow power optimization method. Finally, a prototype is built to verify the effectiveness of our theoretical analysis and the proposed control methods by experimental results.

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