Research On Open Circuit And Current Sensor Fault Diagnosis Of Nine-phase Permanent Magnet Synchronous Motor Syste

As the power guarantee of ship integrated power system,the ship operation performance is directly affected by the reliability of propulsion subsystem.When open-circuit(open-phase,open-switch)and current sensor faults occur,the system should have the function of online identification and positioning,and then switch to the corresponding fault tolerant operation strategy to ensure the stable operation.This paper takes nine-phase permanent magnet synchronous motor(PMSM)as the research object.The characteristics of motor magnetomotive force and electromagnetic torque under normal and open-circuit(open-phase,open-switch)faults operation are discussed.And the motor mathematical models in different coordinate systems are analyzed.Aiming at open-circuit and current sensors faults,a multi-fault comprehensive detection method based on current signal processing is proposed.And the corresponding adaptive algorithm is used to quantitatively describe the fault degree.Based on this,the fault tolerant strategy of open-circuit faults and different current sensor faults are studied,so the fault tolerant operation of the motor system is realized.Firstly,the stator magnetomotive force of a nine-phase PMSM under healthy and open-circuit faults are derived.And the analytical formula of electromagnetic torque is further analyzed.Based on the nine-phase vector space decoupling and coordinate transformation,the mathematical models of the nine-phase PMSM in three different coordinate systems are established,so as to facilitate the proposal and discussion of the fault detection and tolerance system.Secondly,the fault phenomena,current characteristics and electromagnetic torque characteristics under different open-circuit faults are analyzed.The traditional average currents detection methods(AAC)rely on threshold diagnosis.Based on this,an open-circuit fault detection method based on the improved algorithm of average currents(IAAC)is proposed to eliminate the threshold selection and reduce the probability of false diagnosis.In addition,the accuracy and validity of the proposed detection algorithm is verified by comparative experiments.Thirdly,aiming at the gain,zero drift,stuck and loss signal faults of current sensors,the IAAC is further optimized.Therefore,a diagnosis method is proposed that synthesizes the current sensor faults and open circuit faults.In addition,an index which can quantitatively describe the fault degree of current sensor is proposed based on the adaptive threshold.The effectiveness of the proposed comprehensive diagnosis method is verified by different fault diagnosis experiments and various robustness experiments.Finally,the open-circuit and current sensor fault tolerant strategy of nine-phase PMSM are studied.Aiming at the open-circuit fault,the fundamental circular rotating magnetic field and effective value of tolerant phase current are used as constraint conditions,the maximum output torque of tolerant operation is used as objective function.Based on this,the fault tolerant currents are calculated and the tolerant control system is designed.Aiming at the current sensor faults,the fault tolerant currents of natural coordinate system or synchronous rotating coordinate system are reconstructed by combining the diagnostic variables and coordinate axis rotation strategy.Therefore,the stable tolerant operation of muti-phase PMSM is ensured.