单相级联整流器开路故障诊断和容错均压空间矢量脉宽调制算法

Open-Circuit Fault Diagnosis and Fault-Tolerant Voltage Balancing Space Vector Pulse Width Modulation Algorithm of Single-Phase Cascaded Rectifier

针对单相级联H桥整流器(CHBR)的功率开关器件存在的开路故障问题,研究一种开关管开路故障的快速诊断算法,以及针对开关管开路故障的容错均压空间矢量脉宽调制(SVPWM)算法。首先,该文分析单相CHBR功率开关管开路故障时电流流通路径的变化,建立电流误差变化率的分析模型,并提出一种基于电流误差变化率的快速诊断算法。该算法可以快速且准确地定位到故障开关管,且易于在程序中实现。其次,该文提出一种故障容错均压SVPWM算法,该算法在开关管开路故障时利用冗余矢量和冗余开关状态可以使系统在发生故障时仍然可以正常运行,并且各模块间的直流电压也能保持均衡。最后,通过仿真和实验验证了该文所提算法的可行性。

The single-phase cascaded H-bridge rectifier(CHBR)used in the front of power electronic traction transformers has a highly modular structure,and its core component,power switching,has a high failure rate,dramatically impacting system reliability.To solve the open-circuit fault problem of its power switching device in the single-phase two-level H-bridge cascaded rectifier,this paper proposes a fast diagnosis algorithm based on an analytic model and a fault-tolerant voltage balancing space vector pulse width modulation(SVPWM)algorithm.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.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.Accordingly,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.Then,the specific flow of the diagnosis algorithm is provided.Secondly,based on the one-dimensional SVPWM algorithm,the one-dimensional space vector graph is established,and the influence of switch fault on vector selection is analyzed.Then,the redundant vector and redundant switch state of the cascaded converter are used to reselect the fault-tolerant vector to avoid the action of the faulty switch tube and restore the rectifier to normal operation.The selected vector still has the voltage-sharing function.The selection strategy of voltage equalization and fault tolerant voltage equalization vector is proposed for two and n-module cascade rectifiers with open-circuit faults,and the implementation steps of fault-tolerant voltage equalization SVPWM algorithm are given.Finally,the open-circuit fault diagnosis algorithm and the fault-tolerant voltage equalization SVPWM algorithm for six-module single-phase cascade rectifiers are verified by Matlab/Simulink simulation.Moreover,through the FPGA-based two-module cascade rectifier hardware experiment platform and the Verilog-based software platform,fault diagnosis and fault tolerant experiments under single or double open-circuit faults are conducted.The following conclusions are obtained:(1)The open-circuit fault diagnosis algorithm can localize single or double tubes within 1/4 of a fundamental wave cycle,and the speed is fast.Moreover,this algorithm requires minimal computation without additional hardware.It has the advantages of simplicity,speed,and high feasibility,suitable for multi-module cascaded converter systems.(2)The fault-tolerant voltage balancing SVPWM algorithm can achieve fault tolerance for single or double tube open-circuit faults without additional circuits.In addition,it can restore the rectifier to normal operation under single-tube open-circuit faults and double-tube open-circuit faults of typesⅠand,respectively.The system can also maintain the DC voltageⅡbalance of each module under unbalanced loads after fault tolerance.