MMC型电力电子变压器运行可靠性分析及其应用

Operational Reliability Analysis and Application of MMC Power Electronic Transformers

电力电子变压器的运行可靠性水平受历史运行工况、元器件健康水平等因素直接影响。基于功率器件损耗分析,该文提出模块化多电平级(modular multilevel converter,MMC)型电力电子变压器运行可靠性评估方法,将运行条件纳入分析范畴以评估短期运行时设备可靠性变化情况。首先详细分析电力电子变压器输入级、隔离级和输出级的绝缘栅双极型晶体管(insulated gate bipolar transistor,IGBT)模块损耗及其结温波动情况。然后,分析了不同时间尺度结温波动对元器件故障率的影响,建立了电力电子变压器可靠性状态空间,并利用可靠性灵敏度指标辨识运行阶段设备的薄弱环节。最后,以RBTS-BUS2系统算例进行验证,分析表明不同时间尺度的结温波动对功率器件可靠性影响存在差异,隔离级二次侧绝缘栅双极型晶体管对装置故障率贡献度最大,所提方法能够有效反应不同工况下装置及配电网可靠性水平的时变特性,验证了该文模型与评估方法的有效性。

Operational reliability of power electronic transformers is affected by various factors, such as the working conditions or the component health status. Based on the power loss analysis of the IGBT modules, an operational reliability assessment method of the MMC power electronic transformer is proposed in this paper to analyze the reliability time-varying characteristics. Firstly, the insulated gate bipolar transistor(IGBT)power losses and its junction temperatures in the equipment input stage, isolation stage and output stage are analyzed in detail. Then,the relationship between the junction temperatures in different time scales and the component failure rates is analyzed, and the equipment reliability state space is established. The reliability sensitivity indexes are utilized to identify the weak links during the operation. Finally, numerical analysis is carried out based on the modified RBTS-BUS2 case system. The results show that the contributions of the junction temperature fluctuation at different time scales to the IGBT module failure rate are different, among which the IGBT module on the secondary side of the isolation link has the greatest impact. Meanwhile, our method can effectively reflect the time-varying reliability levels of the equipment and the distribution network under different working conditions, thus verifying the effectiveness of the model and the evaluation method presented in this paper.