Research On SPMSM Inter-Turn Short Circuit Fault Diagnosis Strategy Based On Sliding Mode Observer

Permanent magnet synchronous motors(PMSM)are widely used in fields such as electric vehicles and industrial manufacturing because their high power density and good dynamic performance.Because its working principle and environment,many problems such as interturn short circuit(ITSC)faults and bearing faults are inevitable during long-term operation.If the faults is not detected in a timely manner,it can cause economic losses to the motor,and even endanger life safety.Therefore,ensuring the safe and reliable operation of the motor is particularly important.Fault diagnosis of PMSM is one of the effective methods to ensure the safe and reliable operation of the system,this article takes Surface Mounted Permanent Magnet Synchronous Motor(SPMSM)as the control object,and uses a sliding mode observer(SMO)combined with signal processing to achieve fault detection,localization,and degree estimation for the ITSC fault with the highest probability of SPMSM occurrenceFirstly,the mathematical model of SPMSM in healthy condition is analyzed.By introducing a short circuit in the A phase winding of the motor to simulate ITSC fault and establishing a fault mechanism model,aiming at the contradiction between the accuracy and computational complexity of the mechanism model,the change of stator winding resistance and inductance parameters after the fault is calculated by the proportional principle and consistency principle,so as to simplify the ITSC fault mechanism model and effectively solve the problem.Subsequently,the ITSC fault model was analyzed,and the back electromotive force in the two-phase stationary coordinate system is used as the fault signal,laying the foundation for subsequent fault diagnosis.Secondly,the basic principle of sliding mode variable structure is elaborated and traditional SMO is designed based on the mathematical model of SPMSM system.In response to the problem of reduced fault feature accuracy caused by traditional SMO output signal chattering,nonlinear saturation functions and low-pass filters are studied to weaken the chattering phenomenon.To address the impact of amplitude attenuation and phase delay caused by low-pass filters on fault indicators,a second order generalized integrator(SOGI)is used to extract the estimated back electromotive force signal without distortion based on the characteristics of no amplitude attenuation and phase delay at the center frequency.Considering the impact of ITSC faults on the back electromotive force,a study is conducted to extract the unbalanced components caused by faults using the symmetric component method and convert them into direct flow for fault detection.The residual of the back electromotive force was used to locate faults,as SOGI can obtain the orthogonal signal of the output signal and estimate the degree of fault based on fault loop constraints.Finally,the SMO based SPMSM fault diagnosis strategy studied in this paper is simulated and experimentally validated using Matlab/Simulink simulation software and a 2kW SPMSM pairing experimental platform with TMS320F28335 as the control chip.The results indicate that the proposed diagnostic method verifies the correctness and effectiveness of fault detection,localization,and degree estimation without increasing the complexity of the fault diagnosis algorithm.