Open-circuit Fault Diagnosis And Fault Tolerant Voltage Balancing SVPWM Algorithm Of Single-phase Cascaded Rectifier

The single-phase cascaded H-bridge rectifier used in the front of power electronic traction transformer has a highly modular structure,and the power switching device as its core component has a high failure rate,which has a great impact on the reliability of the system.In this thesis,to solve the problem of the open-circuit fault of its power switching device in the single-phase two-level H-bridge cascaded rectifier,an open-circuit fault diagnosis algorithm of power switching device based on analytic model and a fault tolerant voltage equalization space vector pulse width modulation(SVPWM)algorithm are studied.The specific content is as follows:Firstly,the topological structure and basic working mode of the single-phase two-level H-bridge rectifier are analyzed,and the mathematical model of the single-phase cascade rectifier is established on this basis.By analyzing the operation mode of each power switching device in a single module when the open-circuit fault occurs,a mathematical model of the current error rate of the cascaded rectifier is established.According to this mathematical model,the characteristics of the current error rate of the single-phase two-level H-bridge cascaded rectifier with single or double open-circuit faults are analyzed accurately.On the basis,the idea of diagnosis and location of open-circuit fault and the specific flow of diagnosis algorithm are established.Secondly,one-dimensional space vector diagram is established according to onedimensional SVPWM algorithm,and the principle of voltage equalization and priority of voltage equalization are analyzed.On the basis of the above analysis of basic principles,the selection strategy of voltage equalization and fault tolerant voltage equalization vector for two and n-module cascade rectifier with open-circuit fault is proposed,and the concrete implementation steps of fault tolerant voltage equalization SVPWM algorithm are given.Finally,the feasibility and effectiveness of the open-circuit fault diagnosis algorithm and the fault tolerant voltage equalization SVPWM algorithm for two-module and six-module single-phase cascade rectifiers are verified by Matlab/Simulink simulation software.And,through the FPGA based two-module cascade rectifier hardware experiment platform and Verilog based software platform designed in this thesis,the inverter and rectifier experiments are completed,and then the fault diagnosis experiment and fault tolerant experiment of the system in the case of single or double open-circuit faults are completed.The results also verify the feasibility and effectiveness of the open-circuit fault diagnosis algorithm and the fault tolerant voltage equalization SVPWM algorithm proposed in this thesis.