多电平变流器系统可靠性建模与分析

Reliability modeling and analysis of multilevel converter systems

多电平变流器因其良好的特性已被广泛应用于各种中、高压大功率的电能变换场合,其采用了比两电平变流器更多的功率开关器件,从理论上讲具有更高的故障率,但多电平变流器自身拥有大量的冗余状态和较高的控制自由度,当开关管存在故障时可通过释放冗余资源使多电平变流器实现容错运行,从而提高多电平变流器系统的可靠性。为了定量分析不同变流器拓扑的可靠性,首先采用故障物理可靠性建模方法建立功率开关管串/并联的可靠性模型,并基于该模型,建立单相三相两电平变流器的可靠性模型;综合考虑多电平变流器拓扑的自身冗余和容错能力对可靠性的影响,建立了三相多电平和新型混合多电平变流器的可靠性模型,并基于所建立的可靠性模型定量分析了不同变流器的可靠性;最后,对三相五电平混合T-ANPC变流器进行了实验验证。结果表明,多电平变流器可通过容错运行实现带故障持续工作,从而有效提高系统可靠性。

Multilevel converters have been widely used in all kinds of medium and high voltage power conversions because of its superior characteristics.It uses more power switching devices than two-level converter,which might have higher failure rate in theory.However,multilevel converter itself has a large number of redundant states and higher control freedom,which can enhance the reliability of the entire system by allowing the converter to realize fault-tolerant operation flexibly by releasing some redundant resources.In order to quantitatively analyze the reliability of different converter topologies,this paper first uses the method of fault physical reliability modeling to establish the reliability model of series/parallel power switches,and then establishes the reliability model of single-phase and three-phase two-level converters.The reliability models for three-phase multilevel converter and new hybrid multilevel converter is established,considering the influence of multilevel converter′s own redundancy and fault tolerance on reliability,the quantitative comparisons of reliability for different converters are carried out.Finally,the fault-tolerant operation of the new five-level hybrid T-ANPC converter is verified by experiments.The results show that the reliability of multilevel converter is related to the circuit and fault tolerance,and the converter can be controlled to operate in multiple fault tolerance modes by releasing its own redundancies,thus greatly improving the system reliability.