Integrated Fault Diagnosis And Fault-tolerant Control Of Inverter

Inverter is the most ideal AC drive equipment so far and it has been widelyadopted in many fields. However, just as other mechanical or electronic equipments,inverter is prone to a variety of faults in the case of component aging, improperoperation, ambient interference, man-made sabotage, etc. Seriously, the failure ofinverter will probably cause a major accident and lead to irreparable economic orsocial losses. To solve these problems, if some effective fault diagnosis and tolerantcontrol measures is taken in advance, we can diagnose the faults of inverter quicklyand accurately so that the device will not stop suddenly and the losses is minimized.There are many kinds of inverter faults, wherein the faults of sensors and DC-linkaluminum electrolytic capacitor are the most common. Therefore, in this paper, thefaults of current sensors, speed sensor and DC-link aluminum electrolytic capacitorin AC drive systems are studied and some integrated inverter fault diagnosis andtolerant control scheme are proposed.Firstly, for the sensor faults of inverter, an adaptive observer is designed basedon the Lyapunov stability theory. On this basis, an integrated current-and speed-sensor fault detection and isolation (FDI) strategy with three mutually paralleledadaptive observers is proposed. With this strategy, the faults of current-and speed-sensor can be diagnosed simultaneously in the same system and a sensor fault doesnot affect the diagnosis of the other sensor fault. What’s more, the fault tolerantperformance of the system is very good and mistaken diagnosis does not occur.Matlab/Simulink simulation experiments are implemented to verify the proposedFDI strategy.Secondly, to diagnosis the fault of DC-link aluminum electrolytic capacitor, thephysical structure, equivalent circuit model and failure mechanism of aluminumelectrolytic capacitor are analyzed and a failure criterion is presented. In order toestablish the remaining life model of DC-link aluminum electrolytic capacitor, themain circuit structure of inverter is simplified and a recursive least square (RLS)based parameter identification method for DC–link aluminum electrolytic capacitoris proposed and verified by simulation experiments. The remaining life predictionmethod for DC-link aluminum electrolytic capacitor is studied. A fault pre-diagnosisstrategy is presented.Finally, a1.1kW dual-motor experimental platform is built based on dSPACEreal-time simulation tools. Using this platform, the proposed integrated current-andspeed-sensor fault diagnosis and tolerant control scheme are experimentally testedand verified. Since the sensor faults will probably happen during the empty load, full load, start or steady operation process of the AC motor drive system, multiplesets of comparative experiments are conducted. The fault diagnosis and tolerantcontrol performance of the proposed system is analyzed in all aspects.