含分布式电源的配电网继电保护技术

随着分布式电源(distributed generation,DG)并入配电网,使配电网的拓扑结构、潮流分布发生变化,传统的配电网继电保护配置不再适用于含分布式电源的配电网络.为了保证电力系统供电可靠性,充分发挥分布式能源的优势,需要对含有分布式电源的配电网保护方案进行研究.在阐述配电网三段式电流保护原理的基础上,详细讨论了分布式电源的准入容量和接入位置不同时,对其配电网不同故障点的电流保护产生的具体影响.并结合国内外的前沿研究成果,论述当前主要的解决方案,对其进行分类讨论不同保护方案的原理和特点,说明其利弊.该文所做工作对含有分布式电源的配电网保护有一定的参考价值.     

基于2n+1点估计法的含分布式电源配电网的 电压质量概率评估

为准确评估分布式电源及负荷功率的随机特性对配电网电压质量的影响,在已有的点估计法的基础上,提出一种2n+1点估计法,求解分布式电源配电网概率潮流。该方法考虑了风速,光照强度以及负荷随机特性对配电网的影响,通过得到电压概率统计值,然后结合半不变量理论与Gram-Charlier级数展开得到相应的概率密度函数以及含分布式电源节点的电压越限概率,对含分布式电源的配电网电压质量进行概率评估。以含有分布式电源的IEEE-30节点系统作为算例,通过2n+1点估计法进行概率潮流计算,分析了分布式电源接入前后对系统节点电压的影响。     

分布式发电对电力系统继电保护的影响

传统配电网一般都是单一电源的辐射状网络,继电保护按照辐射型网络进行设计和整定。随着分布式发电（DG）的接入,辐射式的网络将变为一种遍布电源和用户互联的网络,使得配电网中的潮流分布发生根本变化。详细分析了分布式发电对原有配电网中的电流保护,距离保护以及对重合闸等传统继电保护所带来的影响;最后根据DG接入电网位置的不同以及容量不同提出了相应的解决方案。     

计及运行成本风险的主动配电网两阶段随机模型预测控制

分布式电源出力和负荷不确定性造成主动配电网运行风险,影响其运行安全性和经济性。建立了计及运行成本风险的主动配电网两阶段随机模型预测模型。结合不确定场景集和不同调节设备的动作特性,通过引入条件风险价值作为风险控制手段,构建了计及风险的两阶段随机优化模型,以降低运行成本分布中的“厚尾”风险。利用模型预测控制方法实现时序滚动优化,精细化协调控制,以减少可再生能源波动性以及负荷预测偏差给主动配电网经济运行带来的影响。最后,通过算例仿真分析,验证了所提方法在保证主动配电网安全运行的同时,进一步降低高额运行成本发生的概率,可实现主动配电网运行风险的有效、准确管控。     

考虑光伏储能和可控负荷的配电网检修计划优化

主动配电网（active distribution network, ADN）是传统配电网的一个发展方向,其特点是能够对接入配电网的分布式电源（distributed energy resources, DER）进行主动控制和主动管理,这会对配电网检修计划的制定产生一定的影响。以含有光伏-储能联合发电系统和可控负荷的配电网为例,研究分布式电源在配电网检修中所能起到的作用,建立了相应的二层优化模型。其中子模型为单设备检修优化模型,考虑天气情况对光伏发电出力的影响,通过对储能电池和可控负荷的优化设置来减小功率损失;主模型为全检修计划优化模型,考虑储能电池容量约束,优化目标为减少检修全过程中的经济损失。针对模型特点,采用混沌粒子群分层优化算法和改进的TSP搜索算法进行求解。IEEE33节点系统的仿真结果显示了模型的正确性和有效性,比较不同条件下的仿真结果可以说明分布式能源的接入有助于降低配电网检修造成的损失。     

基于改进灰色理论的主动配电网中长期负荷预测

摘要： 中长期负荷预测是影响主动配电网规划和调度的重要方面。从柔性负荷、分布式电源及电动汽车等主动配电网中特殊负荷入手,分析提炼负荷长期发展的影响因素;将灰色理论引入主动配电网负荷预测,分析了多变量残差修正灰色模型在计及多因素影响作用和消除累积误差方面的作用。通过具体实例计算,证实了改进灰色方法在主动配电网中长期负荷预测中的有效性和实用性。     

双碳量约束下主动配电网网架规划方法设计

传统的配电网网架规划方法缺少对配电网随机潮流的计算过程,导致规划结果的理想度较低。为此,提出双碳量约束下主动配电网网架规划方法。在碳达峰与碳中和思想的约束下,采用牛顿-拉夫逊法计算配电网随机潮流;根据电源出力的随机特性建立主动配电网网架规划模型,并将最小年运行投资费用和分布式电源出力优化设置为上、下层目标函数;采用遗传算法和十进制粒子算法相互嵌套的方式求解模型,将最优解作为最终规划方案。实验结果表明,应用该方法后,主动配电网的总有功损耗率可降至30%以下、节点电压可降至17 kV以下,且优化后的最小负荷峰谷差为1 400.7 kW,说明该方法能够获取更高效的配电网网架规划方案。     

考虑多元协同互动效应的主动配电网多目标规划方法研究

主动配电网规划时需充分计及风、光等间歇式分布式电源的不确定因素的影响,在常规负荷预测的基础上建立了接入主动配电网的风、光等间歇性分布式电源可信出力模型,并考虑负荷需求侧响应对负荷预测结果的影响,提出了考虑源-荷-储多元协同互动效应的配电网负荷预测模型。在负荷预测结果的基础上,建立了主动配电网双层多目标规划模型,上层规划为电网优化规划问题,以年网络综合费用最小为目标;下层规划模型是在上层规划所得到网架下以典型日系统运行经济性确定储能等可控资源的有功出力。通过优化求解得到主动管理模式下配电网网架规划方案及储能的选址定容方案,最终以上海某主动配电网为例验证所提规划方法的科学性和有效性。     

基于自适应算法的含分布式电源继电保护研究

针对分布式电源的接入将影响配电网短路电流和继电保护整定等问题,提出基于自适应算法的含分布式电源配电网继电保护方法,该方法将分布式电源戴维南模型接入配电网的不同位置,对含分布式电源的配电网进行等效建模。根据仿真模型的故障分析表明:当接入点在保护装置上游或相邻母线时,整定值随着接入位置越近、容量的增加而增加;接入点在保护装置下游时,该段线路按双侧电源方式整定保护装置;故障类型会影响整定值的大小。     

分布式电源对配电网继电保护的影响分析及对策

分布式电源的短路电流特征可分三类,与传统的同步发电机不尽相同。通过分析同步发电机型、异步发电机型、逆变型分布式电源型的短路电流特征,发现同步发电机型的短路电流最具代表性,为此利用PSCAD仿真软件,构建等效的分布式电源接入配电网模型,分析对继电保护的影响。结合实际算例,分析分布式电源接入配电网后,对传统三段式电流保护造成保护灵敏度下降、保护出现误动、重合闸不成功等原因,提出将距离保护应用于分布式电源接入的配电网。计算结果表明,接入距离保护装置必要可行,可以有效地解决三段式保护灵敏度下降和误动等问题。     

分布式发电对配电网继电保护的影响

分布式发电是一种新兴的高效、环保的发电技术,近年来获得飞速发展。然而,大量分布式发电系统的接入改变了配电网的故障电流大小和分布以及原有继电保护装置的基础条件,对配电网的继电保护造成影响。分析了分布式发电接入对馈线的两段式保护和自动重合闸以及分支线的熔断器保护产生的各种可能影响,对分布式发电的广泛推广具有一定的意义。     

含可响应分布式电源的智慧能源配网多目标优化调度

分布式电源增加了配电网的灵活性,但同时也给配网调度带来一定挑战。文章针对含有可响应分布式电源的配网多目标优化调度进行研究。首先分析了居民智慧能源的特征以及居民用户、分布式电源、运行商三者的关系;然后考虑了分布式电源的不确定性,建立了风机和光伏的出力模型,从经济性、环保和配网可靠性角度建立了居民智慧能源配网多目标调度优化模型;针对配网负荷多样化的特点,提出了负荷因数模型,计及到多目标优化模型中;最后利用决策算法求解该模型,并在IEEE33节点系统中进行仿真,说明了所提模型和算法的有效性。     

新型负荷接入环境下的配电网分布式电源规划

随着电动汽车以及储能技术的不断成熟,电动汽车及储能设备等新型负荷的不确定性给分布式电源接入配电网的规划工作带来了新的挑战。基于机会约束,建立了一种考虑新型负荷特性的配电网分布式电源规划模型,该模型既包括电动汽车与储能设备等新型负荷,也包括分布式风电、光伏发电等典型分布式电源,并应用概率潮流和遗传算法对模型进行求解。对IEEE33节点测试系统的测试结果表明,接入新型负荷后系统不确定性增强、总体收益有所下降,验证了所建立的电源规划模型处理负荷及分布式电源不确定性问题的可行性。     

Probabilistic load flow using Monte Carlo techniques for distribution networks with photovoltaic generators

Connections of distributed generation (DG) systems to distribution networks are increasing in number, though they may often be associated with the need of costly grid reinforcements or new control issues to maintain optimal operation. Appropriate analysis tools are required to check distribution networks operating conditions in the evolving scenario. Load flow (LF) calculations are typically needed to assess the allowed DG penetration level for a given network in order to ensure, for example, that voltage and current limits are not exceeded.

The present paper deals with the solution of the LF problem in distribution networks with photovoltaic (PV) DG. Suitable models for prediction of the active power produced by PV DG units and the power absorbed by the loads are to be used to represent the uncertainty of solar energy availability and loads variation. The proposed models have been incorporated in a radial distribution probabilistic load flow (PLF) program that has been developed by using Monte Carlo techniques. The developed program allows probabilistic predictions of power flows at the various sections of distribution feeders and voltage profiles at all nodes of a network.

After presenting theoretical concepts and software implementation, a practical case is also discussed to show the application of the study in order to assess the maximum PV peak power that can be installed into a distribution network without violating voltage and current constraints. A comparison between Deterministic Load Flow (DLF) and PLF analyses is also performed.     

Simplified reactive power management strategy for complex power grids under stochastic operation and incomplete information

In the current released energy market, the large-scale complex transmission networks and the distribution ones with dispersed energy sources and “intelligent” components operate under uncertainties, stochastic and prior incomplete information. A safe and reliable operation of such complex power grids is a major issue for system operators. Under these circumstances an online reactive power management strategy with minimum risk concerning all uncertain and stochastic parameters is proposed. Therefore, new concepts such as reactive power-weighted node-to-node linking and reactive power control capability are introduced. A distributed and interconnected stochastic learning automata system is implemented to manage, in a unified and unique way, the reactive power in complex power grids with stochastic reactive power demand and detect the vulnerable part. The proposed simplified strategy can also consider more stochastic aspects such as variable grid’s topology. Results of the proposed strategy obtained on the networks of IEEE 30-bus and IEEE 118-bus systems demonstrate the effectiveness of the proposed strategy.     

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。     

Overview of current and future energy storage technologies for electric power applications

In today's world, there is a continuous global need for more energy which, at the same time, has to be cleaner than the energy produced from the traditional generation technologies. This need has facilitated the increasing penetration of distributed generation (DG) technologies and primarily of renewable energy sources (RES). The extensive use of such energy sources in today's electricity networks can indisputably minimize the threat of global warming and climate change. However, the power output of these energy sources is not as reliable and as easy to adjust to changing demand cycles as the output from the traditional power sources. This disadvantage can only be effectively overcome by the storing of the excess power produced by DG-RES. Therefore, in order for these new sources to become completely reliable as primary sources of energy, energy storage is a crucial factor. In this work, an overview of the current and future energy storage technologies used for electric power applications is carried out. Most of the technologies are in use today while others are still under intensive research and development. A comparison between the various technologies is presented in terms of the most important technological characteristics of each technology. The comparison shows that each storage technology is different in terms of its ideal network application environment and energy storage scale. This means that in order to achieve optimum results, the unique network environment and the specifications of the storage device have to be studied thoroughly, before a decision for the ideal storage technology to be selected is taken.     

含分布式电源的配电网自适应保护算法研究

分布式电源的引入对原有配电网络中的潮流分布、短路电流、电能质量和系统保护等带来一系列的问题。为了克服分布式电源对配电网保护带来较大影响,应用电力系统中公共连接点的戴维南方程,并结合统计学思想对系统短路电流进行估算,其估算结果作为系统继电保护定值的整定依据,从而达到自适应保护的目的。仿真结果表明了所提出算法的有效性。     

Coordinated control of coastal multi-source multi-load system with desalination load: a review

Traditional seawater desalination requires high amounts of energy, with correspondingly high costs and limited benefits, hindering wider applications of the process. To further improve the comprehensive economic benefits of seawater desalination, the desalination load can be combined with renewable energy sources such as solar energy, wind energy, and ocean energy or with the power grid to ensure its effective regulation. Utilizing energy internet (EI) technology, energy balance demand of the regional power grid, and coordinated control between coastal multi-source multi-load and regional distribution network with desalination load is reviewed herein. Several key technologies, including coordinated control of coastal multi-source multi-load system with seawater desalination load, flexible interaction between seawater desalination and regional distribution network, and combined control of coastal multi-source multi-load storage system with seawater desalination load, are discussed in detail. Adoption of the flexible interaction between seawater desalination and regional distribution networks is beneficial for solving water resource problems, improving the ability to dissipate distributed renewable energy, balancing and increasing grid loads, improving the safety and economy of coastal power grids, and achieving coordinated and comprehensive application of power grids, renewable energy sources, and coastal loads.