Diagnosis And Fault-tolerant Control Of Inverter In Induction Motor Drive System

Induction motor drive system is widely used in industrial production and social life, which effectively improves the automation level and production efficiency of the equipment. The voltage source inverter is the core component of induction motor drive system. Reliable and safe operation of inverter is very important to the system. Power electronic device such as IGBT is easily prone to open circuit and short circuit on high voltage and large current condition because of its own vulnerability. It is necessary to study the diagnosis and fault-tolerant problems of device. For induction motor drive system, double closed-loop vector control scheme is designed. Diagnosis and fault-tolerant of switching devices in inverter are well done to improve performance and operating reliability of the system.Mathematical models of induction motor in different coordinate are established. A double closed-loop vector control scheme of rotor flux and electromagnetic torque is given by rotor flux orientation. The feedback linearization control method in nonlinear system is adopted to realize precise decoupling control of excitation current and torque current based on the two-order state equations of induction motor. The observation of flux amplitude and slip frequency is realized by rotor flux model in two phase rotating coordinate.An open circuit fault diagnosis algorithm based on average current is proposed. Fault diagnosis mechanism is analyzed and the realization method of fault diagnosis algorithm is given. The three-phase four-switch fault-tolerant control scheme is designed. Characteristics of space voltage vectors are analyzed. SVPWM modulation algorithm is presented. Aiming at the problem of unbalanced neutral voltage of capacitors on DC side, the offset of space voltage vectors is deeply studied and a three-phase four-switch SVPWM optimization algorithm is proposed. A neutral voltage compensation scheme is designed to eliminate DC offset of the voltage and expand stable operating region of the system.Finally, an experimental platform for induction motor drive system is set up. The scheme of hardware circuit and control program is given in detail. Results of simulation and physical experiment verify the validity and reliability of the proposed control strategy.