IGBT Open Circuit Fault Tolerance Technology For Two-motor Drive Syste

With the development of industry,multi-motor drive system has been widely used.Generally,each motor in a multi-motor drive system is independently powered by an inverter,so the two-motor drive system is the smallest unit of a multi-motor drive system.Based on the review of fault-tolerant technology of motor drive system,it can be found that there is a lack of research on fault-tolerant techniques of multi-motor drive system.Therefore,this thesis takes dual permanent magnet synchronous motor system as the control object and focuses on the fault tolerance technology of open switch fault of drive system.The main contents of this thesis are given as follows:First,based on modeling and analyzing of open-switch fault of the power device in inverter,it can be found that the open-switch fault will affect the amplitude and phase of the voltage vector and the current output by the inverter,which will reduce the fundamental frequency component of the current and generate the harmonic components at twice the fundamental frequency.Therefore,the fault will substantially degrade torque output of motor.Three traditional current signal-based power device open-circuit fault diagnosis methods are compared and analyzed to simplify the current signal-based open-circuit fault diagnosis method and achieve fast diagnosis action.It is pointed out that the commonly used moving window averaging algorithm has adverse effects on the speed of diagnosis,the reliability of the diagnosis algorithm in the transient process of the motor,and the problem of occupying more storage resources of the controller in the engineering implementation.A simplified open-switch fault diagnosis algorithm based on normalized phase currents deviation is proposed to solve the problems above,and open-switch fault can be located within 15% of the fundamental current cycle.To improve the fault-tolerant control performance of the dual-motor drive system,the five-leg inverter is used as the fault-tolerant topology of the dual-motor drive system after an open-switch fault of converter.The entire process of fault diagnosis and topology reconstruction is studied.An improved PWM method is proposed to expand the speed range of the two motors after the converter is reconstructed to five-leg inverter.Besides,a control strategy for fault-tolerant reconfiguration is designed to shorten the transient process after fault.Based on the proposed strategy,a fast and reliable faulttolerant reconfiguration process is realized without changing the system control structure and algorithm.All the theories and methods mentioned in this thesis are simulated and verified in Matlab/Simulink.The experimental platform is also built to verify the improved modulation method proposed in this paper.The simulation and experimental results confirm the effectiveness of the proposed diagnosis and fault-tolerant control methods in this thesis.