Observer-based Fault Detection And Diagnosis Scheme For The Inverter Circuit

With the development of power electronic technology, inverter-fed motor drive systems arewidely used in modern industry. Inverter is a fragile part in the drive systems, and the powerswitches in the inverter often have open circuit and short circuit fault. All these faults degrade theperformance of the drive system. It has great significance in theory and application to study onfault detection and isolation for the inverter fed motor drive systems.On studying the fault detection and isolation method for inverter with motor drive systems, thethesis proposes a fault detection and isolation method based on robust sliding mode observer.Firstly, based on the dynamic mathematical model of three-phase asynchronous motor, the thesisdesigns a robust sliding mode observer model by using the state equation of the motor and thestates are estimated. Secondly, the residual is obtained by comparing the output of the robustsliding mode observer with the real output of motor drive system, and the upper and lowerthreshold are gained by simulations. The decision strategy for fault detection is formed bycomparing the residual with the threshold, and the switch open circuit fault is detected.By usingcoordinate transformation method, the residual in dq reference frame is converted toabc reference frame, and the residual in abc frame is obtained. The fault isolation strategy ispresented by using the residual in abc frame, and the faulty switch is located.In the end, usingMATLAB/SIMULINK simulation, the simulation results of the nonlinear proportional integralobserver model and the robust sliding mode observer proposed in the thesis are compared, theadvantages and disadvantages of the two observers are analyzed. The simulation results showsthat the robust sliding mode observer proposed in the thesis has good properties in robust todisturbance and fast in convergence to real value, the fault detect and isolation method proposedin the thesis can detect and isolate the switch open circuit faults occurred in the inverter rapidlyand effectively.