轨道车辆永磁直驱技术综述

Review on permanent magnet direct drive technology of railway vehicles

概述了国内外采用永磁直驱技术的轨道车辆发展状况,归纳了永磁直驱转向架的结构形式,讨论了抱轴式直驱结构与弹性架悬式直驱结构的特点及其适用情形,分析了永磁直驱转向架的蛇行运行稳定性与曲线通过性;针对轨道车辆应用,从磁性材料、冷却系统、温升效应、电机质量、气隙磁密、反电势抑制、失磁故障、电路结构等方面论述了永磁直驱牵引电机的结构设计与优化方法,分析了传统的牵引电机控制策略,讨论了模型预测控制技术和无位置传感器控制技术的研究现状及其用于永磁直驱电机的可行性和存在的问题;总结了轨道车辆永磁直驱技术的现存问题并展望了其未来发展方向。研究结果表明:刚性抱轴式永磁直驱结构紧凑,但电机受轮轨振动影响较大且增加了列车簧下质量,仅适用于低速轨道车辆;高速轨道车辆直驱技术宜采用弹性架悬式直驱结构,但需要进一步研究永磁牵引电机和直驱转向架的弹性连接方式和最优匹配参数,优化簧上、簧下质量分布;内置式永磁直驱转向架可缩短车轴长度和减少轴距,具有质量轻、动力特性好等优势,较适用于复杂的地形环境应用;需要研究更为快速准确的永磁电机故障在线诊断、预警与抑制方法,可结合基于故障诊断及预测的智慧运维技术,为车辆提供维修决策建议;需对永磁直驱电机定子、转子拓扑结构进一步优化,并提出更为有效的冷却结构及精确的温升计算方法;传统矢量控制与直接转矩控制难以兼顾高转矩动态响应和低转矩脉动,模型预测控制因其结构简单、动态响应快等优点,较适用于轨道车辆这类低开关频率大功率应用,但仍需进一步研究以降低其运算负荷并提升其稳态性能;无位置传感器技术可节省电机内部空间体积,且能防止编码器故障带来的可靠性问题,适用于内部空间狭小的直驱转向架,现有中高速无位置传感器技术已具有较好的性能,零速和低速下采用高频信号注入法虽能实现较准确的位置估计,但其对电机控制性能带来的一系列不利影响还需要进一步研究。

The development of domestic and overseas railway vehicles adopting permanent magnet direct drive technology was reviewed. The forms of permanent magnet direct drive bogies structures were summarized, and the characteristics and applications of the shaft-holding direct drive structure and elastic suspension direct drive structure were discussed. The snaking operation stability and curve passing ability of permanent magnet direct drive bogies were analyzed. According to railway vehicle application conditions, the structure design and optimization methods of permanent magnet direct drive motors were discussed in terms of magnetic materials, cooling system, temperature rising effects, motor mass, air gap flux density, back electromotive force suppression, demagnetization faults, and circuit structure. Conventional control strategies for traction motors were analyzed. The current research status of model predictive control and sensorless control technologies were discussed, and moreover, their feasibility and application challenges for permanent magnet direct drive motors were studied. Existing challenges associated with permanent magnet direct drive technology for railway vehicles and outlook for future development were summarized. Research results suggest that the shaft-holding direct drive structure is compact but only suits for low-speed trains, since the motor is greatly affected by wheel-rail vibration and will increase the unsprung mass. The elastic suspension direct drive structure can be suitable for high-speed trains, however, further studies should be investigated on the elastic connection mechanisms between the permanent magnet motor and direct drive bogie, the optimal matching parameters, and the optimal suspended and unsprung mass distributions. The permanent magnet direct drive inboard bearing bogie can shorten the axle length and wheelbase, which is suitable for complex terrains application due to its advantages of low mass and good dynamic properties. The faster and more accurate online diagnosis and warning methods with the fault suppression strategy for the permanent magnet direct drive motors need to be studied, which can adopt the fault diagnosis and prediction strategy based intelligent operation and maintenance technique, so as to give a guidance for the vehicle maintenance. There is also a need for further optimization on the topologies of stator and rotor of permanent magnet direct drive motors, where a more effective cooling structure and an accurate calculation method for the temperature increase should be put forward. Traditional field oriented control and direct torque control have difficulties in achieving the high-torque dynamic response and low-torque ripple simultaneously, while model predictive control is more suitable for high power applications with low switching frequency such as railway vehicles due to their advantages of simple structure and fast dynamic response. However, further studies need to be focused on the reduction of the computational burden and the improvement of steady-state performance. Sensorless control technology saves the internal space of motor and avoids some reliability problems due to the elimination of encoders, which is suitable for direct drive bogies with small internal spaces. The state of art sensorless technology has good performance in medium to high speed ranges. The high-frequency signal injection strategies for zero to low speed can realize the accurate position estimation, but further investigations are needed to eliminate its adverse effects to motor control performance.19 figs, 89 refs.