Research Fault Detection And Fault-tolerant Technology Of Inverter In Three-phase Motor Drive System

As the three-phase motor drive system is widely used in the industrial, commercial, military, transportation, aerospace and other fields, it’s especially important to improve the reliability of the system. Three-phase motor drive system is generally composed of motor, inverter, sensors and motor controller. The inverter is the high incidence of failure, and its reliability is directly related to the security and stability of the drive system. In order to improve the reliability of the system, we study deeply the fault diagnostic method and fault-tolerant control strategy of the three-phase inverter motor drive system in this paper.Firstly, we study the fault diagnostic method of the inverter open circuit fault, including expert system diagnosis method, the current-based approach for open-circuit fault diagnosis and the voltage-based approach for open-circuit fault diagnosis. Among them, the voltage error diagnosis method based on the three phase current can only detect single power switch open-circuit fault. In order to solve this problem, a new method is proposed in this paper. Simulation results show that: the improved voltage diagnostic method which this paper improved can detect and locale 15 kinds of open-circuit faults by adding an auxiliary detection variable and simplify the input variables. Moreover, the improved method can detect and locale all 27 kinds of open-circuit faults, and eliminate some of the open-circuit faults exist uncertainty by using the redundant switch to replace the faulty switch.Secondly, we study the inverter fault-tolerant control strategy, and mainly study the topology reconstruction of hardware and the software control strategy with the combination of fault-tolerant technology. On the basis of in-depth research with redundant fault-tolerant topology, we improve it by separating the top and bottom switches of the fourth leg, and using them independently. Simulation results show that: the improved redundant fault-tolerant topology can deal with not only single-switch open circuit fault, single-switch short circuit fault, single-phase open circuit fault, and single-phase short circuit fault, but also the open or short circuit faults occurring in a top switch and a bottom switch in different legs.Finally, we design the hardware in the loop simulation platform based on dSPACE for Experimental verification. The experimental results show that: the improved voltage-based approach can realize all 27 kinds of open-circuit faults online detection and location about experiencing more than one current period, and it can also eliminate some of the open-circuit faults exist uncertainty. The improved redundant fault-tolerant topology can also deal with the open or short circuit faults occurring in a top switch and a bottom switch in different legs under the condition of keeping the inverter output power, control strategy and control method without change. The method presented in this paper improves the reliability of the system through timely fault detection and fault-tolerant control.