Research On Diagnosis And Fault-Tolerant Control Technology Of Switch On Three-Phase Bridge PWM Rectifier For Aircraft Application

With the development of electrical and all electric aircraft, to meet the requirements of power system capacity, variable frequency AC power system has been widely applied in large-scale civil aviation. As an important part of secondary power supply which connects the main power with load,three-phase PWM rectifier for aircraft application has broad application prospects, however, the use of the switch leads to the higher probability of failure. Therefore, the research on diagnosis and tolerant control technology of switch open-circuit fault on three-phase PWM rectifier for aircraft application,is significant to improve the reliability of the rectifier, and promote its application in aviation.The topology of three-phase bridge, the strategy of double closed loop control with PI regulator in dq reference frame, and the method of space vector pulse width modulation have been adopted in the PWM rectifier for aircraft application, which is studied in this paper.The requirements of fault diagnosis methods are analyzed in this paper, then, the principle of selection of diagnostic variables, and setting of parameters are given. Through the analysis on the characteristics of the rectifier with switch open-circuit fault, the available diagnostic variables are discussed. For the characteristics of the distortion of AC-side fault current, a switch open-circuit fault diagnosis method based on the current phase angle is studied and improved. For the characteristics of the changes of the closed loop system under failure, a open-circuit fault diagnosis method based on the reference voltage is studied and improved. Then a open-circuit fault diagnosis method based on fixed-point sampling is proposed, which can deal with the detection and location of multi switch fault.A open-circuit fault diagnosis method based on feature recognition is studied, which is taken examples of modern recognition technology. Finally, the simulation is taken to verify the feasibility of the four methods, and the comparison of their advantages and disadvantages is analyzed.Through detailed analysis of the switch open-circuit fault's impacts on space voltage vector, a fault tolerant control method based on revising the PWM switching patterns is propoaed, which can deal with multi switch fault cases. It can effectively reduce the distortion of AC-side current, as well as the DC voltage ripple.Based on the research of the change of voltage vector, after the analysis of the fault and changes of the equivalent modulation wave after failure and taking fault tolerance control algrothim are comparative analyzed. Finally, the change of the current harmonics and DC voltage ripple, and the influence of PI regulator on fault-tolerant control effect are discussed.Finally, a 5kW PWM rectifier prototype with digital control is designed and built. The experimental results show that, under the aviation power input, the studied and proposed faultdiagnosis and fault-tolerant control method is effective.