Demagnetization Fault Diagnosis For High-Power Permanent Magnet Synchronous Traction Motor

Permanent magnet synchronous traction motor system has the advantages of high efficiency and energy saving, and it has gradually entered into engineering and commercial application stage in the field of the rail transport. High-power permanent magnet synchronous traction motor is the power source in the traction system. However, compared with asynchronous motors and other electrical excitation motors, permanent magnet synchronous permanent magnet traction motor has the risk of demagnetization, which may bring bad effects. So it is significant to carry out study for demagnetization fault diagnosis of the permanent magnet.This paper takes permanent magnet synchronous traction motor system as engineering background, considers high-power permanent magnet synchronous traction motor as specific research object. Based on the analysis of demagnetization fault mechanism and the establishment of mathematical model with demagnetization fault, we carry out in-depth study on how to accurately diagnosis the demagnetization fault for pmsm with variable parameters. The main research work and conclusions are as follows:Firstly, based on in-depth analysis of demagnetization mechanism for permanent magnet of permanent magnet synchronous motor(PMSM), this paper analyzes the characteristics and problems of the existing demagnetization fault detection methods, and points out the real-time observation method based on analytical model of permanent magnet flux linkage has more operability and engineering practicability in the actual system.Consider the shortage of PMSM integrated database model, we first give the basic electrical and mechanical equations for interior permanent magnet synchronous motor(IPMSM) on the d-q axis. Then we analyze the requirements of complex advanced algorithm for the study of parameters perturbations. And based on these two points, some improvements have done in order to satisfy the dynamic inputs of motor parameters.For the perturbation of permanent magnet flux linkage caused by demagnetization fault, we propose the state equation for permanent magnet synchronous motor with demagnetization. A new motor simulation model is established, the motor flux linkage is identified using the adaptive parameter method.Due to the parameter perturbation of traction motor in the actual operation condition, this paper analyzes the cause of existing error during demagnetization fault diagnosis with conventional sliding mode observation method. With the combination of adaptive control and sliding mode variable structure control, we propose the adaptive sliding mode observation method to overcome the deviation caused by parameter perturbation. The simulation results illustrate the effectiveness and robustness of the proposed method.