Research On Fault Diagnosis And Fault-tolerant Control Of Dual Three-phase PMSM Drive System

With the increasing requirement of some applications for the power level and reliability of motor speed regulation system,the drawbacks of traditional three-phase motor have been gradually highlighted and the multiphase motor becomes an important way of solving this problem effectively.The high-speed development of power electronic technology and modern control theory makes the power electronic converter widely used in AC drive system,and the phase number of motor is no longer limited by the phase number of power supply.Multiphase motor has been gradually applied in the fields of aerospace,ship propulsion,railway traction,and electric vehicle by virtue of its high power output,small torque ripple,high reliability and flexible control.Although multiphase motor has obvious advantages in the aspect of reliability,the research on fault diagnosis and tolerant control of multiphase motor is still in the initial stage and its superiority in fault-tolerant operation has not been fully utilized in the practical engineering.Therefore,the research on fault diagnosis and tolerant control of multiphase motor drive is of great theoretical and engineering significance to the improvement of motor system reliability.Among all dual multiphase motors,the dual three-phase PMSM is attractive.This thesis takes the dual three-phase permanent magnet synchronous motor(PMSM)as the control objective and aims at optimizing its basic control methods,further exploring its fault-tolerant capability and providing comprehensive diagnosis and tolerant control schemes for multi-class common faults.This research provides important technology reserves for further improving the fault-tolerant capability of motor drive system.The main contents of this thesis are given as follows:The decoupled mathematic models of dual three-phase PMSM in six-phase natural stationary coordinate system and synchronous rotating coordinate system are built.This work provides necessary basic conditions for the follow-up theoretical analysis of motor and design of control methods.The research on modulation strategy and basic control of dual three-phase PMSM is conducted.Two simple and effective modulation strategies are designed for two-level inverter fed dual-three-phase PMSM drives,and the two modulation strategies are extended to the corresponding three-level system.Different basic control methods are designed according to different optimization targets under the basic control frameworks of vector control and direct torque control,and the comparisons of different basic control methods are studied.This work provides high-performance basic control frameworks for the follow-up research on fault diagnosis and tolerant control of dual three-phase PMSM.The research on comprehensive diagnosis and tolerant control of common sensor faults and electric faults in two-level inverter fed dual three-phase PMSM drives is conducted.A set of comprehensive diagnosis and tolerant control schemes are proposed for the speed sensor fault,DC-link voltage sensor fault,phase current sensor fault,inverter open-switch fault and open-phase fault of two-level inverter fed dual-threephase PMSM drives under the framework of direct torque control.The comprehensive diagnosis methods for the five fault types are designed by combining the ideas of model based diagnosis and signal based diagnosis.And fault-tolerant control strategies are designed for the five fault types under the premise of no change in control framework,modulation strategy and machine model.The research on comprehensive diagnosis and tolerant control of common electric faults in T-type threelevel inverter fed dual-three-phase PMSM drives is developed.A set of comprehensive diagnosis and tolerant control schemes are proposed for the inverter open-switch fault,inverter short-switch fault and open-phase fault of T-type three-level inverter fed dual-three-phase PMSM drives under the framework of vector control.The shared features and typical features are extracted through the analysis of faulty operation state.A current feature identification based two-step comprehensive fault diagnosis method is proposed with the idea of signal based diagnosis.Besides,an intervention based diagnosis method is designed to distinguish the opencircuit fault of DC-link switch and the open-circuit fault of mid-point switch which share the relatively same features.In the aspect of fault-tolerant control,a fault-tolerant T-type three-level inverter topology with fast fault response is designed with the aid of Fuse and TRIAC,and different fault-tolerant control schemes are fulfilled by using the respective proposed software algorithms.The research on diagnosis-free self-healing control of common electric faults in dual-three-phase PMSM drives is conducted.The self-healing mechanism of dual three-phase PMSM is deeply analyzed.A diagnosis-free self-healing control scheme is proposed for multi-class common faults with the aid of the selfhealing capability of dual-three-phase PMSM drives,and it relieves the problem of weakening the system reliability arising from the conventional fault diagnosis and tolerant control schemes.The proposed diagnosis-free self-healing scheme is generally applicable to open-switch fault,single-phase open-phase fault and two-phase open-phase fault.The proposed self-healing scheme breaks the stereotype of “diagnose the fault before tolerate it” and provide a novel perspective for the research on fault-tolerant control of driving system.