Multi-Machine Traction Drive Based on Parallel Connected Synchronous Machines

This paper investigates both the system topology and the control strategy of a new multi-machine traction drive for rail vehicle traction bogies. The drive topology is comprised of two pairs of dual paralleled permanent magnet synchronous machines (PMSMs), each linked to a bogie wheelset through a planetary gearset. A pair of these gearsets, which act as an electronically controlled differential mechanism, removes the speed difference of paralleled propulsive PMSMs, through two paralleled auxiliary PMSMs. Then, a new cascaded sliding mode speed control is suggested to generate the reference currents for each shared converter feeding a set of paralleled PMSMs. The proposed controller is based on a reaching law with a reduced chattering approach, on their control signals, while its tracking performance remains satisfactory. Through these suggestions, the drive transient response can be improved during critical situations, especially during regenerative braking and under low adhesion conditions. The performance of proposed multimachine traction drive and its controller are evaluated by simulations and verified by experiments.