Research on Direct Drive Technology of the Permanent Magnet Synchronous Motor for Urban Rail Vehicles

Compared with the traditional gear reduction mechanism of the asynchronous motor, the permanent magnet synchronous motor (PMSM) direct drive technology has obvious advantages and has attracted increasing attention. We analyzed the advantages of the PMSM direct drive technology and put forward the hollow shaft structure of the coupling to reduce the impact force of the wheel and rail, additional noise, vibration, and loss. We deeply studied the topology and mathematical model of the PMSM. To keep the maximum running speed unchanged, it is necessary to conduct a flux weakening control above the rated speed to increase the speed regulation range of the PMSM. To prevent frequent switching jitter at the transition point and smooth the transition between different weak magnetic fields, we designed a new flux-weakening controller to control the current. Simulation results have been presented to verify the proposed approach efficiency. Taking the PMSM system train on Suzhou Metro line 3 as an example, the on-site energy consumption test was carried out. The energy consumption of the PMSM direct drive and asynchronous motor gear mechanism was compared. The energy consumption of the PMSM direct drive is increased by 16.50%. The flexible plate coupling can alleviate the adverse effects of vibration and improve the reliability of train operation. Finally, we put forward the technical difficulties and challenges of the PMSM direct drive technology. We need to optimize the mass distribution of the direct drive bogie to improve the dynamic performance of the bogie, the heat dissipation conditions, and the accurate control of the PMSM. It will have reference value for the development of the PMSM direct drive in the future.