Current-limiting characteristics of saturated iron-core fault current limiters in VSC-HVDC systems based on electromagnetic energy conversion mechanism

A common method to examine the current-limiting performance of saturated iron-core fault current limiter(SI-FCL) in high-voltage direct-current transmission based on voltage source converter(VSC-HVDC) systems is to solve differential equations based on the system fault transient characteristics and the equivalent inductance calculation equation. This method analyzes the fault current of the VSC-HVDC system in the time domain. However, it is computationally complex and cannot directly reflect the relationship between parameters and the currentlimiting effect of the SI-FCL.In this paper,the relationship between the magnetic flux density and magnetic field energy of the SI-FCL is analyzed. The energy exchange between the DC capacitor and the SI-FCL in the DC short circuit fault process is analyzed. From the perspective of electromagnetic energy conversion, the criterion for determining the current-limiting ability of the SI-FCL in the transient process is given based on the parameters of the SI-FCL and VSC-HVDC system. On this basis, the characteristics of the DC side fault current and the capacitor voltage when the SI-FCL has current-limiting ability are examined.Based on the parameters of the SI-FCL and VSC-HVDC system, a method for calculating the fault current peak value and capacitor voltage drop time is given. Finally, the accuracy of the analysis of the SI-FCL in the VSC-HVDC system based on the electromagnetic energy conversion mechanism is demonstrated through a case study and simulation results of the VSC-HVDC system with different SI-FCLs.

大容量永磁饱和型故障限流器参数设计与优化

为适应大容量应用需求,针对一种直线式永磁饱和型故障限流器(permanent-magnet-biased saturation based fault current limiter,PMFCL)磁拓扑结构,基于等效磁路法建立了以饱和深度比、电感比与电感和为基本变量的结构参数设计算法,并通过分析铁心上工作点的变化规律,将PMFCL结构参数优化转化为对3个独立变量的优化,即对铁心i-Be曲线上3个关键点的优化问题,为获得最优结构参数奠定了算法基础。将参数优化算法应用于110 kV系统设计实例,并基于Maxwell-2D软件建立了直线式PMFCL的场–路耦合仿真模型,验证了算法及优化结构参数的有效性。

永磁饱和型故障限流器的高压大容量化分析

为提高永磁体的偏置能力以利永磁饱和型故障限流器朝高压大容量发展,从温度和外磁场两方面分析了钕铁硼永磁体的稳定性问题,论证了其应用到该限流器的可行性;提出"饱和深度比"的定义,指出改善永磁体的偏置能力与提高铁心的饱和深度比等价;基于一种结构参数可调的永磁饱和型故障限流器拓扑,分析了限流器结构参数与铁心饱和深度比的数量关系,并通过有限元法仿真以及实验加以验证;最后给出了10kV等级永磁饱和型故障限流器的一个设计实例。仿真与实验结果均表明,增加永磁体的厚度与截面积可获得较优的偏置能力,实现永磁饱和型故障限流器的高压大容量化在技术上是可行的。

永磁饱和型故障限流器的永磁体稳定性实验研究

为获得用于永磁饱和型故障限流器(permanent-magnet-biased saturation based fault current limiter,PM-FCL)的钕铁硼(Nd-Fe-B)N35永磁体的运行稳定性能,从时间、温度和外磁场影响3方面展开了实验研究。以永磁体随时间的退磁率来表征时间稳定性,以可逆损失率和可逆温度系数来表征温度稳定性,并分析了永磁部件的面积厚度比S/L对温度稳定性的影响。进一步,用通电螺线管模拟220kV变电站的工程磁场环境,通过实验考查了PMFCL永磁体的外磁场稳定性。实验表明,钕铁硼永磁体具有较好的时间稳定性和外磁场稳定性,在温度较高时的退磁效应并不明显,并可通过设计面积厚度比S/L较低的限流拓扑予以抵消。所得研究结果为研制面向工程应用的高压大容量PMFCL提供了基础依据。

兼顾技术经济性的永磁偏置型故障限流器优化配置算法

提出了一种兼顾技术性和经济性的大电网永磁偏置型故障限流器(Permanent-magnet-biased Saturation based Fault Current Limiter,PMFCL)优化配置算法.介绍了PMFCL限流机理,定义了短路电流裕量作为挑选超标节点的标准.将节点自阻抗作为节点短路电流水平的衡量指标,基于节点自阻抗增量,构建了兼顾全局限流效果与经济性的PMFCL优化配置评价函数.综合考虑了PMFCL启动条件和节点自阻抗对支路阻抗参数的灵敏度指标以缩小寻优空间,提出了PMFCL在大电网中配置优化算法.将该算法应用于IEEE 39节点标准算例,调用Matlab遗传算法函数完成仿真.结果表明,与不计及灵敏度相比,该算法寻优效率较高;所得最优配置方案能够使所有节点短路电流满足限流要求并保留一定裕量,对超标越严重的节点限流效果较好,验证了该算法的可行性及有效性.

饱和铁心型超导限流器在柔直系统中的限流特性研究

饱和铁心型超导限流器是一种新型故障限流装置,在处理电力系统短路故障方面具有广阔应用前景。该限流器利用铁心的饱和特性,具有响应速度快、限流过程不失超等优点。但是,目前对于饱和铁心型超导限流器的研究主要集中在交流系统,对其在柔性直流输电系统中的应用效果及限流特性的研究较少。该文分析了饱和铁心型超导限流器在柔直系统中的限流机理,基于PSCAD/EMTDC,研究了限流器在基于模块化多电平换流器的柔性直流输电(MMC-HVDC)系统中的限流特性。结果表明,饱和铁心型限流器对柔直系统短路电流峰值具有很强的限制作用,但无法限制故障稳态电流值。最后,分析了励磁电流大小对铁心饱和状态及限流器限流效果的影响,明确了励磁电流的选取原则。