Research On Fault Diagnosis And Fault-Tolerant Control Of Inverter

Induction motor drive system has been widely used in industrial, commercial and aerospace applications, etc, for its excellent speed control performance and energy saving. However, the complexity of the control strategy and the features of semiconductor results easily in various failures of the drive system. In some special applications, such as automotive and aerospace systems, nuclear power and hazardous chemical plants, there is significantly increasing demand for the drive system capable of high reliability, maintainability and survivability. Therefore, it is important to diagnose the system failures fast and accurately to improve the system reliability using fault-tolerant control strategy. To improve the fault-tolerant capability of the induction motor drive system, sensors malfunction and converter faults are researched in this paper.In induction motor drive system, the key technology is accurate estimation of the motor flux and speed. And the estimation is applied based on the signals of speed, current and voltage, which are sampled by various kinds of sensors. Consequently, the conventional drive system will have to halt to prevent an even worse damage when sensor failures encountered. This paper investigated four different control strategies of induction machine drive system and proposed a tolerant control scheme based on data fusion. Simulation and experimental results verify the validity of the proposed scheme.Furthermore, this paper analyzed various types of faults of PWM voltage source inverter and performed theoretical analysis for the input supply single line to ground fault and the IGBT base drive open fault. The diagnosis circuit was designed for input supply single line to ground fault and the performance of the driver system was studied on the fault condition. A modified current vector method for the diagnosis of IGBT base drive open fault was proposed for the diagnosis of IGBT base drive open fault based on the simulation and experiment of the Park vector method. At last the validity of proposed method was verified by simulation and experiment.At last, to validate the validity and performance of the fault-tolerant method and the fault diagnosis method, all the methods presented above are applied in the 7.5kW induction motor drive system. The experimental results demonstrated that the fault-tolerant capability of the driver system is improved greatly comparing with the conventional vector control system. By adopting the proposed method, continuous operation of the inverter are achieved in the event of losing some or all sensors.