| 引用本文: | 张艳霞,宋金孺,张子扬.中性点不接地柔直配电网的单极接地故障暂态过程分析及保护新方案[J].电力自动化设备,2025,45(2):94-102. |
| ZHANG Yanxia,SONG Jinru,ZHANG Ziyang.Single-pole-grounded fault transient process analysis and a novel protection for flexible DC distribution network with neutral point ungrounded[J].Electric Power Automation Equipment,2025,45(2):94-102. |
|
| 摘要: |
| 针对中性点不接地的柔直配电网分析了直流馈线发生单极接地故障的暂态过程，提出了单极接地保护新方案，能有效解决现有直流线路保护不能反应中性点不接地柔直配电网的单极接地故障问题。在单极接地故障的分析中，将故障发展过程分为子模块电容放电阶段和交流重新馈入充电阶段。基于叠加原理分析了子模块电容放电阶段的电流流通路径、直流馈线暂态零模电流的电流成分和变化规律，得到故障馈线暂态零模电流主要呈现衰减非周期分量特征、非故障馈线暂态零模电流主要呈现振荡衰减分量特征的结论；利用牛顿迭代法推导了交流重新馈入充电的时刻，分析了影响因素并计算了过渡过程持续的最短时间。基于子模块电容放电开始时刻至交流重新馈入充电时刻这一段的暂态特征提出单极接地保护方案。该方案利用直流母线出现的零模电压启动保护，利用零模电压极性实现故障选极，利用故障馈线暂态零模电流绝对值的第一个积分时段值大于非故障馈线的值、且呈现衰减非周期分量特征选出故障馈线。搭建仿真模型，对故障分析结果和保护方案的有效性进行了验证。 |
| 关键词: 柔直配电网 直流中性点不接地 模块化多电平换流器 单极接地故障 暂态特性 零模分量 继电保护 |
| DOI：10.16081/j.epae.202408019 |
| 分类号:TM77 |
| 基金项目: |
|
| Single-pole-grounded fault transient process analysis and a novel protection for flexible DC distribution network with neutral point ungrounded |
|
ZHANG Yanxia, SONG Jinru, ZHANG Ziyang
|
|
Key Laboratory of Smart Grid of Ministry of Education, Tianjin University, Tianjin 300072, China
|
| Abstract: |
| The transient process of single-pole-grounded fault of DC feeder in flexible DC distribution network with neutral point ungrounded is analyzed, and a novel single-pole-grounded fault protection method is proposed, which can effectively solve the problem that the existing DC line protection cannot reflect this kind of fault in the special DC distribution network. In the analysis of the single-pole-grounded fault, the fault development process is divided into the sub-module capacitance discharging stage and the AC re-fee-ding charging stage. Based on the principle of superposition, the current flow path of the sub-module capacitance discharging stage, the DC feeder transient zero-mode current composition and its change rule are analyzed. It is concluded that the fault feeder transient zero-mode current mainly presents the characteristic of attenuation non-periodic component, and the non-fault feeder transient zero-mode current mainly presents the characteristic of oscillating attenuation component. Newton’s iterative method is used to deduce the AC re-feeding charging time, then its influencing factors are studied and the shortest time of the transition process is calculated. According to the transient characteristics of the period from the beginning time of sub-module capacitance discharge to the time of AC re-feeding and charging, a single-pole-grounded protection method is proposed. This method uses the zero-mode voltage of DC bus to start the protection and uses its polarity to select the fault pole, and combines two features of fault feeder that the first integrated time period result of the absolute value of its transient zero-mode current is larger than the result of the non-fault feeder and its characteristic of the attenuation non-periodic component to select the fault feeder. A simulation model is built to verify the fault analysis results and the effectiveness of the protection method. |
| Key words: flexible DC distribution network DC neutral point ungrounded modular multilevel converter single-pole-grounded fault transient characteristics zero-mode component relay protection |
