Mitigation of Distributed Generation Impact on Protective Devices in a Distribution Network by Superconducting Fault Current Limiter

Protection of radial distribution networks is widely based on coordinated inverse time overcurrent relays (OCRs) ensuring both effectiveness and selectivity. However, the integration of distributed generation (DG) into an existing distribution network not only inevitably increases fault current levels to levels that may exceed the OCR ratings, but it may also disturb the original overcurrent relay coordination adversely effecting protection selectivity. To analyze the potentially adverse impact of DG on distribution system protective devices with respect to circuit breaker ratings and OCR coordination fault current studies are carried out for common reference test system under the influence of additional DG. The possible advantages of Superconducting Fault Current Limiter (SFCL) as a means to limit the adverse effect of DG on distribution system protection and their effectiveness will be demonstrated. Furthermore, minimum SFCL impedances required to avoid miss-operation of the primary and back-up OCRs are determined. The theoretical analysis will be validated using the IEEE 13-bus distribution test system is used. Both theoretical and simulation results indicate that the proposed application of SFCL is a viable option to effectively mitigate the DG impact on protective devices, thus enhancing the reliability of distribution network interfaced with DG.

Current Limiting Characteristic Analysis of Magnetic-controlled Switcher Type Fault Current Limiter

A novel magnetic-controlled switcher type fault current limiter (FCL) based on the topology of the saturated iron core high temperature superconducting FCL is proposed. The magnetic field distribution of the FCL iron core is analyzed by FEA software ANSYS. The current limiting characteristic is investigated by both 3-D field-circuit coupled simulation and Matlab. The experiments on the 220 V/50 A test model show that the FCL can limit the fault current swiftly and effectively,and the FCL has the advantages of simple and reliable structure, flexible control strategy. The simulation and experimental results prove that the theoretical expectation and current limiting performance is satisfactory for practical use.

Superconducting fault current limiter(SFCL)for fail-safe DC-DC conversion:From power electronic device to micro grid protection

In DC micro grids and networks,DC-DC power converters having a large number of semiconductor-based power electronic devices are usually adopted to interconnect the renewable sources and flexible loads.Most of the semiconductor-based devices suffer from poor fault withstanding abilities,but conventional power electronic protection schemes have the bottlenecks of the time-delay,self-malfunction and mis-judgement.This paper presents a novel solution using the superconducting fault current limiter(SFCL)to protect a power electronic device and extend the usage to a micro grid.This SFCL is actually a self-triggering,recoverable,and passive current limiter,which does not involve any additional circuit hardware and software.Experimental investigations and simulation analyses clarify the feasibility of using this superconductor-based protection scheme to implement the self-acting fail-safe protection of DC-DC converters.Further system-level simulations explore the SFCL to suppress the over-current and stabilize the bus voltage of a photovoltaic based DC micro grid,particularly facing millisecond-level transients and faults.Our experimental and theoretical investigations lay some technical bases to establish a superconductor-semiconductor-coupled interdisciplinary application from the view from the applied superconductivity,to power electronics,and to micro grids.

Design aspects of transmission voltage superconducting fault current limiters with YBCO tapes in China

The design progress of superconducting fault current limiter(SFCL)for transmission voltage is presented,with a focus on the results of recent key experiments that have led to a state‐of‐the‐art high‐voltage high‐capacity super‐conducting current limiting techniques:the resistive alternating current(AC)SFCL,saturated iron cores AC SFCL,and resistive direct current(DC)SFCL.The main driving factors for designing SFCL in these projects are the preparation of high‐performance superconducting materials,the development of large‐scale superconducting current limiting winding,system testing,and operation technology.Based on the authors’experience with both AC and DC SFCLs,this paper focuses on the main design aspects of resistive SFCL at transmission voltage.The relationship between the hot spot caused by the inhomogeneity of long superconducting tape and the overall parameter selection is presented.In addition,the thermal calculation based on the current limiting resistance and a real‐time current curve is also proposed for the parameter design of the current limiting winding.

不失超型SFCL特性仿真分析

对不失超型SFCL限流时的线路电流变化曲线进行了理论分析和仿真计算 ,研究了其对节点测量阻抗和线路电流谐波特性的影响 ,并就动作电流对其特性的影响进行了详细分析。仿真计算结果表明 ,不失超型SFCL的阻抗虽然随着线路电流周期性变化 ,但对线路电流谐波特性的影响不大 ,完全可用于电力系统 ;

SFCL对HVDC系统中换相失败的影响

针对逆变侧换流母线逆变侧发生短路使得交流电压下降和直流电流上升而引起的换相失败问题,分析了换相失败影响因素及桥式超导故障限流器(SFCL)限流原理。在PSCAD/EMPDC仿真环境下,以CIGRE HVDC基准模型为研究对象,将SFCL应用于直流输电系统中,研究SFCL对HVDC系统稳定运行及换相失败的影响。研究表明,SFCL能够限制交流系统的故障电流继而使直流输电系统能快速恢复正常运行状态。

限流器配置与网架结构优化协同的受端电网短路电流抑制策略

如何有效地抑制短路电流水平已成为受端电网规划和运行中不可忽视的问题。文中量化和构建了计及超导故障限流器(SFCL)配置与网架结构优化的短路电流约束。在此基础上,提出了一种SFCL配置与网架结构优化协同的短路电流抑制模型,采用基于McCormick包络的交流潮流线性化框架,并通过循环结构最小化松弛误差。为有效求解上述模型,将主问题分解为若干子问题,设计了基于嵌套Benders分解算法的求解策略。基于改进的IEEE 39节点系统和河南电网规划系统开展仿真分析,验证了所提策略在经济性和短路电流抑制效果方面的有效性和实用性。

关于HTSFCL中的超导材料交流损耗分析的一种新方法

分析并推导了高温超导带材的交流损耗模型,给出了一种新的分析其磁滞损耗方法,这样的磁滞损耗模型表明磁滞损耗是电流和与电流成正比的磁场感应强度的函数。

Fabrication of HTS dc Bias Coil for 35 kV/90 MVA SFCL

---For a saturated iron core fault current limiter, superconductor is the only suitable material to make the dc bias coil, especially when the device is used in a high voltage power grid. Commonly, superconducting wires are used to wind the dc bias coil Since the performance of the wires changes greatly under magnetic fields, the calculation of the field spatial distraction is essential to the optimization of the superconducting magnet. A superconducting coil with 141000 ampere-turns magnetizing capacity made of 17600 meters of BSCCO 2223 HTS tapes was fabricated. This coil was built for a 35 kV/90 MVA saturated iron-core fault current limiter. Computer simulations on magnetic field distribution were carried out to optimize the structural design, and experiments were done to verify the performance of the coil The configuration and the key parameters of the coil will be reported in this paper.

含DG的配电网闭环运行SFCL最佳位置分析

分布式电源的并网影响了配电网的可靠性。为更有效地限制有分布式电源时的故障电流,探讨为超导故障限流器寻找最佳位置。在MATLAB中对环形配电网中不同位置发生三相短路进行了仿真,通过仿真的数据确定了在含有分布式电源的环形配电网中超导故障限流器的最佳安装位置。

500 kV限流器高温超导磁体的制作与测试

超导限流器是对超高压输电线路短路故障电流实现快速、有效限制的一种新型电力装置。近年来随着国民经济的发展,用电负荷增长和供电可靠性需求增加,电网短路电流水平已经逼近甚至超过传统开关设备的开断能力,成为超高压电网发展和安全、稳定运行的重要制约因素之一。然而,电网结构调整等传统限流措施降低了电网的安全性和灵活性,亟需研制适用于超高压电网的限流装置。超导限流器集短路故障检测、触发和限流功能于一身,是电力系统最理想的限流装置。依托高电压等级限流器用超导磁体系统的研制项目,完成500 kV限流器用高温超导磁体系统制作与测试工作。该超导磁体的室温孔径为1660 mm,总高度为1960 mm,液氮量为2000 L,中心最大磁场为0.45 T,额定励磁安匝数为468000安匝,由3组线圈共计88个双饼组成,运行电流分别为220 A(YBCO线圈)/1000 A(Bi2223线圈)/220 A(YBCO线圈),杜瓦注入液氮后抽空减压至72 K稳定运行。经过绕制、接线、组装、焊接、检测等工序,完成磁体系统集成,降温后进行整体测试,一次性励磁成功,没有失超。整个系统绝缘等级大于10 kV、真空漏率优于10^(-6)(Pa·L)/s、液氮蒸发量小于70 L/d,指标均达到设计目标。

含磁偏置超导限流器的66/10 kV变电站的故障限流分析

配网系统短路电流越来越大,现有断路器即将超过遮断容量,给电网安全带来较大影响。针对此问题,利用双分裂电抗器反并联低阻抗特性和超导单元故障失超特性,提出一种具有二级逐级限流特征的磁偏置超导限流器。根据辽阳市某66/10 kV变电站线路参数,基于Matlab/Simulink建立含磁偏置超导故障限流器的系统仿真模型,进行限流仿真计算,获得磁偏置超导故障限流器限流效果的变化规律,以及在故障电流下的失超电阻和温度的变化规律,验证了磁偏置超导限流器原理的正确性。结果表明,磁偏置超导限流器在三相短路故障时电网电流限流率最大可达到19.68%,最大温度为123.7 K,失超恢复时间为32 ms,表明其具有限流响应迅速和失超恢复快的优势。

考虑短路电流非周期分量影响的磁偏置型超导故障限流器设计方法及其限流特性分析

随着电力负荷快速增长,电力系统的故障电流水平持续上升,甚至超出了现有断路器的开断能力;为有效限制故障电流,超导故障限流器(superconducting fault current limiter,SFCL)逐渐投入应用。SFCL在正常运行时呈现零阻抗,故障发生后迅速转为高阻抗,可作为配合断路器开断的理想选择,提高电力系统的运行安全性。介绍了一种磁偏置型超导故障限流器(magneto-biased superconducting fault current limiter,MBSFCL),提出了考虑短路电流非周期分量影响的MBSFCL设计方法,对于MBSFCL的制造具有一定的指导意义。通过搭建仿真模型,验证了所提出方法的可行性,并对MBSFCL的限流特性进行了深入分析,讨论了不同非周期分量对断路器的开断影响,以及MBSFCL中电感、电阻参数变化对短路电流及其分量的限流效果影响。分析结果表明,在所提出MBSFCL设计方法中必须考虑非周期分量,且MBSFCL的电阻参数变化对短路电流的抑制效果更为显著。

高温超导限流器对风电场故障穿越能力的影响研究

当电网发生故障时,风电场容易自动解列而导致故障更加严重,因此风电机组应具备一定的故障穿越能力。本文提出将高温超导故障限流器应用于风电场,以提高风电场低电压穿越的能力。通过建立高温超导限流器模型以及含高温超导限流器的风电机组并网模型,然后仿真在不同故障类型和不同拓扑下高温超导限流器对风电场故障穿越能力的影响。研究表明,使用高温超导限流器能够有效提高风电机组在系统发生单相、多相故障下的穿越能力,同时,提高单回线与双回线送出电能的风电场模型故障穿越能力。

感应屏蔽型高温超导故障电流限制器模型机研究

为了研究感应型高温超导故障电流限制器的限流特性,该文建立了一个模型机,模型机由三部分组成:初级铜绕组、次级超导筒以及铁心。初级绕组的匝数N、铁心的有效磁导率meff对超导故障电流限制器的限流特性都有影响。对模型机进行了静态和动态测试,静态实验结果得出了限流器正常运行的范围,动态实验结果描述了限流器的特性。

基于灵敏度法的超导故障限流器的优化配置

提出一种超导故障限流器(SFCL)优化配置的新方法。通过进行短路计算,首先确定安装SFCL能够可靠启动的支路,然后分析SFCL对网络阻抗矩阵的影响,得出短路电流超标点自阻抗对这些支路阻抗参数的灵敏度,根据灵敏度的大小,从中选取安装SFCL的多条候选支路,采用改进的非支配排序遗传算法(NSGA-Ⅱ)这一多目标优化算法对候选支路进行优化计算,实现SFCL的安装位置、数量以及阻抗值的优化配置。最后,通过6节点系统和IEEE 39节点系统的仿真验证了所述方法的有效性和可靠性,大大缩小了解的搜索空间,实现了SFCL的优化配置,限制了超标点短路电流水平。

故障限流装置的发展和应用

在综合大量文献的基础上综述了国内外各种故障限流装置的研究现状、发展应用,特别对广泛应用的电力电子类故障限流器 FCL(Fault Current Limiter)和前景广阔的超导类故障限流器 SFCL(Superconducting Fault Current Limiter)进行了比较深入的分析,对各类限流装置的技术水平做了比较,提出了实用化过程中存在的应用问题,并对限流装置的发展趋势做出了预测。

基于YBa_2Cu_3O_7块材的高温超导限流器的限流特性研究

电阻型高温超导限流器(HTSFCL)利用超导体的超导态-正常态转变来限制短路电流,无需短路故障检测电路,具有体积小、重量轻的优点。为此在国内提出了基于YBa2Cu3O7高温超导材料的电阻型HTSFCL方案;开展了电阻型HTSFCL限流特性的实验研究,得到了不同电压下,HTSFCL的限流效果;分析了超导体失超电阻的传播特性。实验结果表明:电阻型HTSFCL可将预计200A(交流峰值)的短路电流限到120A,限流效果明显。这对进一步开展基于YBCO材料的电阻型HTSFCL研究具有重要的指导意义。

基于MgB_2的新型电阻型超导故障限流器的研制和性能分析

超导故障限流器对限制短路电流和短路容量具有重要的研究意义。文中基于MgB2的特性,采用先变形后退火的方法,并利用特制高温玻璃纤维进行绝缘,在退火处理后再通过环氧树脂胶黏剂固化,研制了一台小体积电阻型超导故障限流器样机。同时通过液氦和氦气冷却,对其性能进行测试;通过建立电阻型超导故障限流器的一维热传导模型和电路方程,对其动作特性进行仿真。测试和仿真结果表明该样机限流效果明显,限流百分比可达44%以上,然而限流器的失超长度、超导线材温度和失超电阻随着时间呈非线性变化且限流器的线材并未全部失超。失超恢复时间约为1.5s,可通过交替连接方式满足重合闸需求。最后针对10kV电力系统,提出了MgB2的小体积电阻型超导故障限流器工程设计原理,并分析了其在工程应用中的可行性。

新型磁控开关型故障限流器参数设计及模型机研究

基于饱和铁心型高温超导故障限流器拓扑,提出了一种适用于中高压电网的磁控开关型故障限流器结构。通过工作原理分析,论证了此拓扑结构的可行性,建立了限流器的数学模型和简化电路模型,推导出这种限流器系统的设计公式,并在此基础上研制了一台220V/50A限流器模型机。试验结果表明,该故障限流器具有快速、有效的故障电流限制作用,且具有结构简单可靠,运行控制灵活的特点。