基于二次电弧光伏接入配网故障识别研究

为了提高光伏接入配电网单相自动重合闸的成功率,减少配电网瞬时性故障的非全相运行时间,搭建了适用于配电网的二次电弧模型,通过对二次电弧阶段故障相出口电压进行快速傅里叶分解,分析了在瞬时性故障与永久性故障时,故障相基波电压幅值变化率的差异,提出了在二次电弧阶段基于故障相基波分量的故障识别方法,该方法具有原理简单、计算量小和识别速度快的优点。通过在PSCAD中建立动态仿真模型,验证了所提方法的正确性和有效性。     

考虑多DG接入的配电网自适应电流主保护方案

为解决多个分布式电源(DG)接入配电网后保护装置拒动、误动、灵敏度低的问题,提出了一种考虑多DG接入配电网的自适应电流主保护方案.首先建立PQ控制的IIDG模型,分析多DG接入影响.然后根据故障复合序分量的关系,求解在线路不同位置发生两相短路、三相短路故障时各保护安装处的正序电流,提出改进的自适应Ⅰ段电流保护方案;并基...     

牛从直流牛寨站典型故障仿真分析及保护改进建议

为了研究牛从直流牛寨站发生各典型故障时的故障发展机理以及当前保护系统动作特性,以便为直流控制保护逻辑优化提供理论依据,在牛从直流PSCAD/EMTDC仿真模型中设置牛寨站各典型故障,研究发现牛寨站换流变网侧故障消除后直流系统可快速恢复正常.换流变阀侧及阀区接地故障均导致牛从直流牛寨侧接地极流过强电流,短路故障均导致交流...     

基于GRU神经网络的送电线路故障在线检测方法

为防止因输电线路故障导致事故影响的范围进一步扩大,提出一种基于改进的长短期记忆网络GRU对电力系统中输电线路的故障在线识别的方法.采用固定时间窗口移位标记的方法对故障起始时刻附近数据编码,搭建故障起始时刻判别逻辑;再根据返回的起始时刻对故障清除前的节点运行数据映射故障位置及类型.最后在PSCAD/EMTDC中以新英格兰...     

光伏电源经新能源同步机并网的仿真研究

针对大规模光伏接入电网带来的稳定性问题,提出光伏电源经新能源同步机MGP并网的解决方法.目前对于MGP的研究仍集中于理论分析与实验室单机模型阶段,尚未得出可用于电磁暂态仿真分析的系统模型.为研究各工况下MGP运行的电磁暂态特性,基于MGP理论研究及同步电机对轴系连接关系,在PSCAD/EMTDC软件中搭建110 kW光...     

户用光伏接入对配电网电压影响及优化研究

户用光伏的随机性和波动性是制约网络消纳的关键因素,高比例的户用光伏并网将影响区域网络的静态电压稳定。文章通过户用光伏系统分析,研究了户用光伏接入对配电网电压波动的影响;并提出基于遗传算法的含户用光伏配电网无功优化方法;最后,利用IEEE33节点配电网模型,针对不同渗透率下户用光伏接入配电网进行仿真实验,验证了所提含户用光伏配电网无功优化方法的可行性与准确性,可有效解决配电网电压波动问题。     

基于暂态能量比的交流输电线路故障选相方法

针对传统利用小波变换等方法获取暂态能量实现故障选相存在算法和选相判据复杂的问题,提出一种利用故障分量构建暂态能量的输电线路故障选相方法。该方法从电压、电流故障分量角度构建三相暂态能量比和零序暂态能量指标,通过将这些指标与相应的阈值比较,完成故障选相。基于某实际系统动模试验的故障录波数据验证了方法的有效性;并通过PSCAD/EMTDC搭建典型双端电源输电线路仿真模型,验证了所提选相方案可以不受故障点位置、故障初相角等的影响,可耐受更高的过渡电阻。     

直流配电网交流侧不对称故障对直流侧电容电压影响研究

直流配电网的AC/DC换流器交流侧不对称故障对直流侧正、负极电容电压有重要影响。本文对直流配电网在交流不对称故障工况下直流侧电容电压进行理论推导分析,指出单相接地故障下因零序分量的存在使得AC/DC换流器直流侧正、负极两个电容的电压会呈现出共模波动特征。在PSCAD/EMTDC软件中搭建典型的直流配电网电磁暂态仿真模型,分别开展直流配电系统在稳态和交流单相接地故障暂态工况下的仿真分析,仿真结果也表明交流侧不对称故障过程中AC/DC换流器直流侧正、负极两个电容的电压表现共模波动过程,进而引起正、负极电容电压的不平衡,使得AC/DC换流器交流侧三相交流电压也出现直流偏置,影响系统恢复。     

基于故障时刻自同步的波形比较式多端配电网快速保护方案

为打破电气量的同步采集技术壁垒,并合理应对不平衡差流问题,分析了基于故障检测时刻保护数据自同步的实现方法,利用多端电流合成和Tanimoto系数构建了波形相似度比较式保护新判据。基于5G网络数据实时传输功能,形成了一套适用于多端配电网的综合快速保护方案。经PSCAD/EMTDC软件仿真,验证了所提方案能够快速可靠地确定故障区段,能很好地适应配电网复杂故障场景。     

基于阻抗模型故障特征匹配技术的 配电网单相接地故障测距研究

单相接地故障是配电网最常发生的故障,准确而快速地确定配电网单相接地故障位置对排除系统故障,减少事故损失具有非常重要的作用。针对当前配电网单相接地故障精确定位问题,通过采用网络故障时测量点处的电压预存信息,同时利用故障中馈线出口处测得的零序电压和零序电流信号,提出了一种采用差分进化算法的基于阻抗模型故障特征匹配的配电网单相接地故障测距的新方法。该方法基于系统阻抗模型定义了系统故障特征适应度指标,利用枚举法确定故障分支线路,并采用差分进化算法精确定位故障位置。中石化西北油田艾丁变10 kV线路配电网仿真结果表明了所提出的配电网单相接地故障测距方法的有效性     

并网光伏最大接入功率的研究

在简化低压配网模型中,分析了在负荷水平、功率因素及电压波动的情况下,光伏电源最大接入功率受母线电压及线路电流约束的变化趋势,推导出配变低压侧母线电压影响其变化趋势临界值的计算公式;提出了针对低压配网光伏电源的最大接入功率计算方法。通过仿真验证了该计算方法具有较高的准确性以及光伏接入具有减少低压配电线路网损的作用。     

配电变压器“双地网”防雷有效性研究

从实际出发,分析了配电变压器采用"双地网"接地方式所引起的故障,计算得出了电源防雷箱防雷效果不明显,双地网并不能够有效隔离高、低压接地网的结论。并以此为中心,分析了配电变压器防雷思路,提出了有效的配电变压器防雷方法,建议在配电变压器防雷保护中将"双地网"改成"三点一地"接线方式,高、低压侧均装设避雷器。     

计及逆变型分布式电源的有源配电网单相接地故障分析

风电、光伏等可再生能源以逆变型分布式电源(IIDG)形式并网后,使配电网成为有源配电网,其接地故障分布特点与传统配电网不同。文章通过分析恒功率控制型和低电压穿越控制型IIDG故障电流特性,建立其故障等值模型,然后,针对不接地系统建立计及IIDG的单相接地故障分析模型,分析并网变压器中性点不同接地方式和IIDG的接入位置下,故障点电流以及IIDG至故障点间线路零序电流特征分布,最后,通过PSCAD/EMTDC建立含IIDG接入的配电网故障仿真模型,验证了单相接地故障建模及分析方法的有效性。     

Single-phase-to-ground fault protection based on zero-sequence current ratio coefficient for low-resistance grounding distribution network

Definite-time zero-sequence over-current protection is presently used in systems whose neutral point is grounded by a low resistance (low-resistance grounding systems). These systems frequently malfunction owing to their high settings of the action value when a high-impedance grounding fault occurs. In this study, the relationship between the zero-sequence currents of each feeder and the neutral branch was analyzed. Then, a grounding protection method was proposed on the basis of the zero-sequence current ratio coefficient. It is defined as the ratio of the zero-sequence current of the feeder to that of the neutral branch. Nonetheless, both zero-sequence voltage and zero-sequence current are affected by the transition resistance, The influence of transition resistance can be eliminated by calculating this coefficient. Therefore, a method based on the zero-sequence current ratio coefficient was proposed considering the significant difference between the faulty feeder and healthy feeder. Furthermore, unbalanced current can be prevented by setting the starting current. PSCAD simulation results reveal that the proposed method shows high reliability and sensitivity when a high-resistance grounding fault occurs.     

Optimal operation management of fuel cell/wind/photovoltaic power sources connected to distribution networks

In this paper a new multiobjective modified honey bee mating optimization (MHBMO) algorithm is presented to investigate the distribution feeder reconfiguration (DFR) problem considering renewable energy sources (RESs) (photovoltaics, fuel cell and wind energy) connected to the distribution network. The objective functions of the problem to be minimized are the electrical active power losses, the voltage deviations, the total electrical energy costs and the total emissions of RESs and substations. During the optimization process, the proposed algorithm finds a set of non-dominated (Pareto) optimal solutions which are stored in an external memory called repository. Since the objective functions investigated are not the same, a fuzzy clustering algorithm is utilized to handle the size of the repository in the specified limits. Moreover, a fuzzy-based decision maker is adopted to select the ‘best’ compromised solution among the non-dominated optimal solutions of multiobjective optimization problem. In order to see the feasibility and effectiveness of the proposed algorithm, two standard distribution test systems are used as case studies.     

Research progress on fre protection technology of LFP lithium-ion battery used in energy storage power station

随着电化学储能市场的蓬勃发展,电化学储能电池本身的安全性越来越受到关注,如何最大程度地降低储能电池组火灾风险是电化学储能大规模应用时亟需解决的问题。本文综述目前国内外针对锂离子电池热失控已有的研究成果,包括磷酸铁锂电池的燃烧特性、火灾危险等级以及在储能电站预警系统中应用的锂离子电池热失控及热扩散参数;梳理不同灭火剂对电池火灾的灭火效率;同时总结电化学储能电站的灭火系统选择,为电网储能工程应用提供参考,有效支持锂离子储能电池的大规模工程需求。     

Influence of photovoltaic generation model and time resolution on the reliability evaluation of distribution systems

This paper aims to investigate the influence of photovoltaic (PV) generation on reliability evaluation of distribution systems. Two PV generation models are used to predict the output power injected into the grid, taking into account the main relevant environmental variables, the irradiance and ambient temperature. Issues that directly affect the output power, such as the spatial smoothing effect due to the plant size and the influence of the irradiance and temperature measurement interval are taken into consideration. Using measurement time series of irradiance and local temperature, the models are used to generate power series in 4‐minute and hourly resolutions. The generated power series are used in a reliability assessment model, with the objective of evaluating the impact of solar resource variability on the reliability indices of the system. Case studies on the IEEE RBTS‐Bus 2 and on the real distribution system of Fernando de Noronha in Brazil are presented and discussed, for power plants of different capacities, considering the effect of the PV generation models, the temporal resolution of the time series and the spatial smoothing of the power output fluctuations. The results show that the power time series in hourly resolution significantly underestimates the frequency of interruptions. For the real system, this index is underestimated at the system level (up to 43%) and at the load points (up to 72%). On the other hand, for the interruption duration index, the temporal aggregation results in a small underestimation (just 4%). The results also indicates that the smoothing effect is irrelevant for typical PV system sizes of distribution systems with discretization equal to or above 4 minutes.     

分布式电源对杭州配网保护的影响及准入容量的计算

分布式电源具有投资少、见效快、节约土地、清洁更环保等优点,作为未来能源结构的一个重要组成部分,已得到人们的普遍认可。分布式电源的接入对整个电力系统的影响巨大而深远,同时给系统的运行带来一系列技术问题。文章详细分析了分布式发电对配网保护的影响及准入容量的计算。     

Novel method for setting up the relay protection of power systems containing renewable energy sources and hydrogen energy storage systems

Integration of renewable energy sources (RES) together with energy storage systems (ESS) changes processes in electric power systems (EPS) significantly. Specifically, rate of change and the lowest values of operating conditions during the emergencies are got influenced. Such changes can cause incorrect actions of relay protection (RP) as it was designed and adjusted with no regard for influence of RES and ESS. Detailed research on processes during the different normal and abnormal modes in both EPS and primary transducers and also in RP devices should be done to take preventive actions. To do this research mathematical modeling based on detailed and authentic models of all elements including RP should be used. HRTSim (which was developed by authors) software for simulating EPS provides the opportunity to create such models of EPS of any size without simplifications and limits. Using of this instrument together with detailed mathematical models of RP which were developed before provided the opportunity to investigate them rigorously in RES-integrated EPS. Settings providing adequate action of RP in certain conditions were performed as a result of this investigation. Fragments of these investigations are performed in this paper. Results of these investigations would be useful for designing new methods and tools of RP adjustment.