Research On The Inverter High Fault Tolerance Control Method

The AC driver system consisting of the inverter and the motor has stepped into the practical stage for almost 20 years. However, with the application areas broaden, the AC driving system reveals several defects itself. The inverter in the adverse condition has great chance of having fault, such as the switch's open circuit fault, the switch's short circuit fault, the sensor's break fault and so on. The fault in the system will affect the system's normal operation, even make the system shutdown. However, in the area such as navigation,aeronautic,nuclear industry and so on, the shutdown of the system can cause huge economic losses. So the fault detection and fault-tolerant control design are needed, making sure the system running safely. The paper researched the fault detection and fault-torrent design of the speed sensor and the switches in the inverter.For the fault of the speed sensor, the paper detected the fault using hardware circuit. After the fault detection, the model reference adaptive system (MRAS) was used to estimate the motor speed. Taking into account that the voltage reference model in the traditional MRAS has integral drift, the paper used the improved MRAS. The improved MRAS used the motor as the reference model to estimate the motor speed. The paper used simulation and experiment to test the feasibility of the improved MRAS.For the fault of the switch, the paper detected the fault with the average current Park vector. The Park vector can locate the switch which has the fault. After the fault detection, the four-switch-three-phase inverter was used to torrent the fault. Analyzing the four-switch-three-phase inverter, the space vector was used to control the inverter. When the space vector was used to control, the DC bus capacitors had unequal voltage problem. The paper took approach to compensate the unequal voltage of the DC bus capacitors. The paper used simulation to test it.The experimental platform based on DS1104 dSPACE was built. The platform can simulate the switch's open circuit fault, short circuit fault and the sensor's fault. The two 1.1kW induction motors were used as the controlled object. The experiments of the motor speed estimation based on the improved MRAS and the fault detection of the switch in the inverter with the average current Park vector were finished on the experimental platform. The platform tested the feasibility of the methods proposed in the paper.