Research On Comprehensive Diagnosis Method Of Electrical And Demagnetization Faults Of PMSM System In Vehicle

With the acceleration of electric vehicles replacing traditional fuel vehicles,the requirements of electric drive system for high-performance drive motors are becoming higher and higher.Permanent magnet synchronous motor(PMSM)meets the above requirement because of its advantages such as small volume,high power density,good stability,strong overload capacity and good controllability.However,the fragile components of PMSM system bring severe challenges to the reliability and safety of electrical vehicles.Therefore,online fault diagnosis of PMSM system is particularly important.This paper proposes a comprehensive diagnosis method for inverter open-circuit fault(OCF),interturn short-circuit fault(ISCF)and local demagnetization fault(LDF),which is of great significance to improve the safety and reliability of electrical vehicles.In view of the research on fault diagnosis of vehicle PMSM system at home and abroad,the problems of PMSM system fault diagnosis are summarized and the corresponding solutions are put forward.Three kinds of independent fault diagnosis of PMSM system,OCF,ISCF and LDF are deeply studied,and the design principle of multi-faults comprehensive diagnosis algorithm is proposed.Based on the study of multi-faults classification,a comprehensive diagnosis algorithm for electrical faults and demagnetization fault of PMSM system is designed.Compared with the existing related technologies,the research results of this paper have certain advantages.The main research results of this paper are as follows:1.To meet the requirement of the low detection limit in ISCF diagnosis for low speed PMSM,a new ISCF diagnosis method based on zero-sequence voltage vector decomposition is proposed to solve the problem of residual zero-sequence voltage caused by inherent asymmetry of PMSM.By establishing the mathematical model of PMSM with ISCF,the ISCF degree indicator and the fault phase location formula are constructed.The results show that the method proposed in this paper has the advantages of low fault detection limit,accurate fault phase location and less influence with speed and load variation.2.For the difficulty of fast detection of OCF in PMSM drive system,an OCF diagnosis method based on current variation trend is proposed.This paper extracts the current behavior characteristics and constructs the OCF indicator for inverter power switches.The state transition relationship models of various OCFs types are established,and the fault location of switches is realized through model matching and state transition sequence analysis.The results show that the proposed method greatly improves the diagnosis efficiency of OCF compared with the existing related technologies,and the problem of accurate positioning of fault switches under 21 OCFs is solved.3.For improving the online non-invasive diagnosis sensitivity of LDF and fault location accuracy,a new LDF diagnosis and demagnetization pole location method based on coil voltage is proposed through the analysis of the change mechanism of back EMF in PMSM winding slot caused by air gap magnetic density.The analytical calculation formula of PMSM coil back EMF is deduced by using the sampling function,and the characteristic information regarding LDF is extracted.The results show that the proposed method greatly improves the sensitivity of LDF diagnosis and realizes the absolute positioning of demagnetized permanent magnet.4.To solve the coupling problem of ISCF,OCF and LDF in the characteristic information of diagnosis,a fault classification method based on different current balance degree is proposed.Through the analysis of the influence mechanism of OCF,ISCF and LDF on currents amplitudes,the in-phase fluctuation characteristics of currents amplitudes in one cycle of rotor rotation are extracted,and the fault classification indicator is established.The results show that the proposed method improves the universality of fault classification compared with the related technologies.5.For the complexity of electrical faults and LDF comprehensive diagnosis in the PMSM system,the principle of multi-faults comprehensive diagnosis is proposed based on the above research results.Meanwhile,the priority is set according to the characteristics of fault source,and the multi-faults comprehensive diagnosis algorithm is designed to ensure the low detection limit of ISCF,the diagnosis rapidity of OCF and the high detection sensitivity of LDF.The problem of fault misdiagnosis caused by multi-faults feature coupling is effectively solved.