Research On On-line Monitoring Method Of Aging State Of Power Devices In PMSM

There are many outstanding properties,such as green environmental protection,small volume,high energy utilization,accurate and convenient control in Permanent magnet synchronous motor(PMSM).Especially under the background of increasingly serious energy and environmental problems,it has been widely used in the fields of transportation,agriculture,industry,national defense and aerospace.According to the research statistics,the power switching device in the inverter is one of the parts with the highest fault frequency in the motor control system.Its main faults include open circuit fault and short circuit fault.However,with the use of the system,when the power devices work in high-frequency switching mode for a long time,the aging phenomenon will gradually appear,resulting in the inverter working in an abnormal state,increasing the pressure of current and voltage borne by the residual power devices,causing system instability and increasing the risk of failure.By effectively monitoring the health status of power devices in PMSM system,the safety and reliability of the system can be effectively improved,which is of great practical significance.However,the normal operation of the system is not affected by slight aging,so the traditional fault diagnosis methods have limited effect on monitoring the early aging status of power devices.Therefore,this paper takes the PMSM system as the research object,the features of the most widely used field-oriented control(FOC)and direct torque control(DTC)are analyzed.And the on-line monitoring method for aging status of power devices under different control strategies are proposed and verified by simulationIn the field-oriented control strategy,based on the analysis of the operating characteristics of the system,an on-line monitoring method for aging status of power devices based on line voltage and current energy is proposed.In the method of power device aging monitoring based on line voltage,it is necessary to collect the line voltage in the operation of the system and compare it with the reference voltage in the healthy state to obtain the eigenvalues,and then get the corresponding status monitoring index of power device aging through experiments.In the aging monitoring method of power devices based on current energy,the current of the inverter is collected,and the current data of the same period when the system is stable is selected for energy calculation.The aging eigenvalue of power devices can be extracted by comparing the difference values,and then the specific aging intervals can be obtained by analyzing the extracted data according to the deformation formula.Finally,through experiments,the status monitoring indicators corresponding to the aging of power devices are obtained.In the direct torque control strategy,because of its good robustness and closed-loop flux linkage characteristics,the new strategy based on phase diagram and three-phase current are proposed to realize on-line monitoring of aging status of power devices.Firstly,the parameters related to power device aging are found by observing each parameter of the system through analog power device aging.Secondly,through further analysis of the relevant parameters,the characteristic variables of power device aging are obtained,and the related eigenvalue are the phase diagram of the magnetic chain and the peak of the three-phase current.Then,the on-line monitoring method based on magnetic chain diagram and three-phase current is validated through a number of experiments,and the relationship between power device aging and this characteristic value is obtained.Finally,the status monitoring indicators corresponding to the aging of power devices are summarized.In this paper,by analyzing the characteristics of different control strategies and combining with the actual use scenarios,several schemes for monitoring the aging status of power devices under different control strategies are obtained.By comparing different methods,it is found that the proposed methods can achieve on-line monitoring of power device aging status in permanent magnet synchronous motor system.The method is simple,low cost and short diagnostic time,which avoids the system failure caused by power device aging and improves the security and reliability of the whole system.