Review on development and key technologies of permanent magnet synchronous traction system for rail transit

To systematically analyze and summarize the technologies and development trend of permanent magnet traction system control, the advantages and disadvantages of using the permanent magnet synchronous motor (PMSM) as the traction motor in rail transit were introduced, and the applications of permanent magnet synchronous traction systems in at home and abroad were illustrated. The technologies those control high-power traction inverters at low switching frequencies and control permanent magnet synchronous traction motors were reviewed to analyze the design concepts and research methods of key technologies, such as the pulse width modulation strategies and field-weakening control. Investigations of recent research results were carried out to illustrate the advantages and limitations of various control methods, and the prospects and challenges of PMSM in the field of rail transit traction were predicted. Research results show that the built-in PMSMs are suitable for direct drive systems, and their small volumes and high efficiencies make them superior. A traction inverter usually adopts a hybrid pulse width modulation strategy. The asynchronous, synchronous, and single-pulse modulation are used in low frequency bands, middle frequency bands, and under square wave conditions, respectively. Improving the system's dynamic performance under special synchronous modulation and ensuring the smooth switching between different modulation methods are the most difficult aspects of traction inverter pulse width modulation technologies. The motor control strategy mainly focuses on three field-weakening control methods in high-speed operation areas, such as field-weakening control based on dual current regulators, field-weakening control with voltage vector angles, and field-weakening control under square wave conditions. Based on the previous research, future studies should include the sensorless technology, on-line fault diagnostics and prediction, and high-precision parameter identification of PMSMs, and the electromechanical coupling characteristics and short-circuit handling of traction drive systems are the key research directions in the future. 2 tabs, 16 figs, 68 refs. © 2021, Editorial Department of Journal of Traffic and Transportation Engineering. All right reserved.