基于系统电压分布曲线拟合的后备保护方案

拓扑结构的多样性和电源特性的复杂性使得基于稳态电流量的后备保护整定工作量大且失配现象时有发生,无需整定且具有自动配合功能的后备保护技术是继电保护工作人员追求的目标。在分析了传统反时限过流保护存在的问题和辐射状配电网正、负序电压故障分量分布特征的基础上,提出了基于系统电压分布曲线拟合的后备保护方案。所提方案利用综合电压序分量的系统分布与各级保护实现逐级配合的最小动作时间拟合具有反时限特性的动作曲线,得出拟合后的分段函数表达式。由其计算的保护动作时间可自动反映各保护与故障位置的拓扑关联关系,在满足选择性和快速性要求的前提下实现各级保护的自适应配合。DG接入不会改变综合电压序分量的分布特征,因而所提方法对含DG的网络具有自适应性。理论分析和仿真结果表明,所提方法可自动实现任一点故障时上下级保护的快速、逐级配合。     

距离保护在具有分布式电源的配电网系统中的应用

研究了分布式电源接入放射状配电网对配电网继电保护的影响。利用Matlab/Simulink建立了直接并网和逆变并网两种分布式电源模型,并对配电网进行距离保护整定计算。针对分布式电源的类型、容量和接入位置等因素,探讨了在有分布式电源接入的配电网系统中,电流速断保护和距离保护的工作情况。分析了运行中可能出现的问题,如长短线配合、短路点过渡电阻对测量阻抗的影响,并给出了相应解决办法。结果表明分布式电源对配电网继电保护的灵敏度,选择性有一定的影响。     

A novel neural network and backtracking based protection coordination scheme for distribution system with distributed generation

With the increased installation of renewable energy based distributed generations (DGs) in distribution systems, it brings about a change in the fault current level of the system and causes many problems in the current protection system. Hence, effective protection schemes are required to ensure safe and selective protection relay coordination in the power distribution system with DG units. In this paper, a novel adaptive protection scheme is proposed by integrating fault location with protection relay coordination strategies. An automated fault location method is developed using a two stage radial basis function neural network (RBFNN) in which the first RBFNN determines the fault distance from each source while the second RBFNN identifies the exact faulty line. After identifying the exact faulty line, then protection relay coordination is implemented. A new protection coordination strategy using the backtracking algorithm is proposed in which it considers the main protection algorithm to coordinate the operating states of relays so as to isolate the faulty line. Then a backup protection algorithm is considered to complete the protection coordination scheme for isolating the malfunction relays of the main protection system. Several case studies have been used to validate the accuracy of the proposed adaptive protection schemes. The results illustrate that the adaptive protection scheme is able to accurately identify faulty line and coordinate the relays in a power distribution system with DG units. The developed adaptive protection scheme is useful for assisting power engineers in performing service restoration quickly so as to decrease the total down time during faults.     

Adaptive overcurrent protection scheme coordination in presence of distributed generation using radial basis neural network

The operational performance of conventional overcurrent protection relay coordination connected to a distribution network is adversely afected by the penetration of distributed generators (DG) at diferent buses in the network. To address this problem, this paper proposes a novel adaptive protection coordination scheme using a radial basis function neural network (RBFNN), which automatically adjusts the overcurrent relay settings, i.e., time setting multiplier (TSM) and plug setting multiplier (PSM) based on the penetration of DGs. Short circuit currents and voltages measured at diferent buses are acquired using the remote terminal units (RTU) connected to diferent buses within the terminal network. Communication between the various remotes and local end station RTUs is through hybrid communication systems of fber optic and power line communication system modules. The new adaptive overcurrent protection scheme is applied to the IEEE 33-bus distribution network with and without DGs, for single and multi-DG penetration using both the ETAP and MATLAB software. The simulation results show the proposed scheme signifcantly improves the protection coordination.     

Adaptive centralized protection scheme for distribution systems with DG using risk analysis for protective devices placement

Conventional electric distribution systems are radial in nature, supplied at one end through a main source. These networks generally have a simple protection system usually implemented using fuses, re-closers, and over-current relays. Recently, great attention has been paid to applying Distributed Generation (DG) throughout electric distribution systems. Presence of such generation in a network leads to losing coordination of protection devices. Therefore, it is desired to develop an algorithm which is capable of protecting distribution systems that include DG, through diagnosis and isolation of faults. A new approach for the protection of distribution networks in the presence of DGs is presented in this paper. The algorithm is based on dividing an existing distribution network into several zones, each capable of operating in island operation. In the suggested method, risk analysis is used to optimize the protection zones by optimal placement of protective devices. Multilayer Perceptrons (MLPs) neural networks are used for determination of faults. The proposed scheme has been implemented on a selected part of a real distribution network of a large city and a MATLAB based developed software has been used to implement the proposed algorithm on the real network data.     

考虑分布式电源的配电网优化规划

分布式电源（DG）的发展给配电网络规划带来了新的挑战。考虑负荷增长,从供电公司的角度,以DG接入投资、线路投资以及电网有功损耗最小为目标函数,建立了配电网节能减损的规划模型,充分利用配电网正常运行呈辐射状网络的特点,采用启发式方法对含DG的配电网进行规划,通过模糊评估算法分析了DG接入对配电网运行带来的影响,进而引入协调系数,对目标函数进行优化。算例计算结果验证了所提出的模型和算法的有效性。     

含高渗透率DG的配电网实用化保护方案

分析了高渗透率DG接入配网对传统三段式过流保护的影响。为了解决三段式过流保护可能存在的误动、拒动问题,提出了一种含高渗透率DG的配电网实用化保护方案并给出了保护配置及整定原则。该保护方案基于重合闸前加速保护、防孤岛保护和合于故障保护之间的时序配合,不依赖于通信且无需装设大量PT,保护定值整定按照常规配网无DG接入条件下整定,不受DG接入的数量、容量和位置影响。RTDS仿真结果表明,所提出的保护方案实用、有效,能够在含高渗透率DG接入环境下准确隔离配网故障。     

分布式发电接入对配电网继电保护的影响分析

分布式发电接入配电网后,对配电网系统继电保护会产生影响。针对传统单电源放射式配电网络,研究了分布式发电接入位置和接入容量对过电流保护的影响,研究结果对含分布式发电的配电网继电保护的整定有参考价值。     

Fault diagnosis in distribution networks with distributed generation

The penetration of distributed generation (DG) in distribution power system would affect the traditional fault current level and characteristics. Consequently, the traditional protection arrangements developed in distribution utilities are difficult in coordination. Also, the reclosing scheme would be affected. With the rapid developments in distribution system automation and communication technology, the protection coordination and reclosing scheme based on information exchange for distribution power system can be realized flexibly. This paper proposes a multi-agent based scheme for fault diagnosis in power distribution networks with distributed generators. The relay agents are located such that the distribution network is divided into several sections. The relay agents measure the bus currents at which they are located such that it can detect and classify the fault, and determine the fault location. The proposed technique uses the entropy of wavelet coefficients of the measured bus currents. The performance of the proposed protection scheme is tested through simulation of two systems. The first system is a benchmark medium voltage (MV) distribution system and the second system is practical 66 kV system of the city of Alexandria.     

基于状态量信息的含分布式电源配电网保护新方案

为消除分布式电源(DG)接入对保护的影响,同时尽量减少改造成本,提出了一种基于多点状态量信息的含DG配电网保护新方案。对于DG下游辐射状线路和无DG接入的馈线,所提方案根据过电流保护动作信息实现故障定位。另外,基于馈线首端和DG并网点处的电压和电流信息,提出了补偿阻抗极性信息的新判据及其故障定位方法。当DG上游区域发生故障时,所提方案无需加装电压互感器,即可快速准确地切除DG上游区域的故障线路。最后,通过PSCAD/EMTDC软件对一个含DG的10 kV配电网进行故障仿真与分析,结果验证了所提方案的有效性和正确性。     

网源协调驱动下考虑网络转供能力的配电系统多目标双层近期规划

提高供电能力和对分布式电源(DG)的接纳是未来环网状配电网扩展规划的新目标。为此,通过引入安全距离这一配电网N-1安全评价指标,提出了一种考虑N-1安全和DG与网架协调的配电网多目标双层优化规划模型。该模型以改造线路、新增负荷接入位置和DG安装位置及容量为决策变量,计及了系统故障负荷的转供和不可控DG出力及负荷波动带来的不确定性。根据模型的特点,利用多场景技术将随机性问题转化为确定性问题,并采用正态边界交点和动态小生境差分进化算法组成的混合策略对模型加以求解。通过算例对比分析了是否考虑N-1安全和网源协调对规划结果的影响,仿真结果表明,所提规划模型能够在提高DG渗透率的同时,挖掘配电网的供电潜力和推迟线路改造;所得规划方案实现了配电网经济效益和安全水平的综合优化,更适用于负荷增长平缓和占地通道资源紧张的城市建成区配电网近期扩展规划。     

含分布式电源配电网保护方案

分布式电源（DG）接入配电网会对传统的配电线路电流保护产生影响,可能导致保护不正确动作。针对这一问题,文中提出一种新的保护方案,对传统的配电线路保护配置进行了改进。该保护方案根据DG接入点的位置,对被保护馈线进行了分区,在DG的上游区域配置了方向纵联保护,而整条馈线则保留了过电流保护。为了能方便整定工作以及更快地切除故障,根据DG接入位置的不同,馈线的过电流保护分别采用定时限或反时限形式。采用该保护方案后,无论DG的输出功率如何变化,故障都能被可靠切除。最后,对一个10 kV配电系统进行了仿真,验证了保护方案的有效性。     

分布式发电接入位置和注入容量限制的研究

位于负荷中心的分布式发电系统对配电网的电压分布有重大影响,影响大小与分布式电源的接入位置和注入容量有很大关系。首先研究了放射状链式配电网络在并入一定容量分布式电源后各负荷节点电压幅值的变化,然后推广到一般性连续解析形式,继而对电压分布的特点、分布式发电的可行接入位置以及注入容量限制进行了理论探讨。研究表明从稳态电压角度,分布式电源接入馈线的位置和具体注入容量的大小有较严格的理论依据。     

含放射性约束条件的配电网重构研究

研究网络重构是配电网运行及优化的重要功能之一,在各种重构算法中,网络模型通常采用放射性的拓扑结构。为保证重构结构满足拓扑的放射性约束,把放射约束的数学模型纳入到含分布式电源(DG)的网络重构系统中,使以往复杂的方法转化为一个简单而有效的方法。进而把该放射性约束条件运用于基于粒子群优化算法的配电网重构中,克服了粒子群寻优的盲目性,提高运算速度。最后通过IEEE33和IEEE69节点算例表明,放射性条件的约束和DG的引入能够更进一步实现整个网络重构方案的优化。     

Characterization of the loss allocation techniques for radial systems with distributed generation

In the restructured electricity industry, meaningful loss allocation methods are required in order to send correct signals to the market taking into account the location and characteristics of loads and generations, including the local sources forming the distributed generation (DG). This paper addresses the issues related to loss allocation in radial distribution systems with DG, with a three-fold focus. First, the key differences in the formulation of the loss allocation problem for radial distribution systems with respect to transmission systems are discussed, specifying the modeling and computational issues concerning the treatment of the slack node in radial distribution systems. Then, the characteristics of derivative-based and circuit-based loss allocation techniques are presented and compared, illustrating the arrangements used for adapting the various techniques to be applied to radial distribution systems with DG. Finally, the effects of introducing voltage-controllable local generation on the calculation of the loss allocation coefficients are discussed, proposing the adoption of a “reduced” representation of the system capable of taking into proper account the characteristics of the nodes containing voltage-controllable DG units. Numerical results are provided to show the time evolution of the loss allocation coefficients for distribution systems with variable load and local generation patterns.     

Optimal location and sizing of real power DG units to improve the voltage stability in the distribution system using ABC algorithm united with chaos

The introduction of a Distributed Generation (DG) unit in the distribution system improves the voltage profile and reduces the system losses. Optimal placement and sizing of DG units play a major role in reducing system losses and in improving voltage profile and voltage stability. This paper presents in determination of optimal location and sizing of DG units using multi objective performance index (MOPI) for enhancing the voltage stability of the radial distribution system. The different technical issues are combined using weighting coefficients and solved under various operating constraints using a Chaotic Artificial Bee Colony (CABC) algorithm. In this paper, real power DG units and constant power load model and other voltage dependent load models such as industrial, residential, and commercial are considered. The effectiveness of the proposed algorithm is validated by testing it on a 38-node and 69-node radial distribution system.     

DG planning with amalgamation of economic and reliability considerations

Distributed generation has been playing a vital role in dealing with issues related to distribution systems. This paper presents an approach which provides the distribution system operator with a set of solutions for DG placement to optimize reliability and total cost of power consumed by the distribution system. Optimal location of a Distributed Generator is evaluated based on the performance indices derived for reliability index and total cost of power consumed by the system. The proposed approach is applied to a 15-bus radial distribution system and a 18-bus radial distribution system and the results are analyzed.     

计及分布式电源的配电网重构研究

分布式电源因其独有的环保性和经济性,在电力系统中拥有广阔的发展前景,但同时对配电网络的运行控制等方面产生了重大影响。研究了计及分布式电源的配电网络重构,采用了一种适合于含分布式电源的配电网络重构的改进二进制粒子群优化算法,并建立了计及分布式电源的配电网络辐射状运行判定依据。最后对IEEE33节点测试系统进行仿真,表明本文所用的方法是合理有效的。     

计及多约束的多分布式电源接入配电网最大承载力分段算法

分布式电源(DG)大量并网给电能质量带来风险,评估DG接入配电网的最大承载力对DG规划具有指导意义。建立了多DG接入配电网承载力评估的优化模型:目标为DG并网容量最大,约束涉及电压偏移、电压波动、短路电流和继电保护的相关技术标准。针对该模型,提出了基于约束指标相对于DG容量灵敏度的单约束和多约束协调分段计算方法。基于不同的DG初始值,分段计算可分别采用倒推和顺推2种计算流程进行。最后计算分析了辐射型配电网在多约束多个不同类型DG情况下的系统最大承载力,表明了所提方法在计算精度和效率方面的优越性。     

应用边界保护原理提高分布式发电系统并网协调性的方法

为解决分布式发电系统与配电网保护的协调性问题,提出了一种新的分布式发电(distributed generation,DG)并网控制方法。由于在DG系统并网点上游和下游线路故障时,DG系统对电网保护的影响是不同的,因此提出在带有DG 系统的配电线路上装设阻波器构成线路边界的思想,采用行波边界保护模式,对DG系统并网点上游和下游故障进行选择性保护,进而保证配电线路故障后DG系统能够快速准确地解列,确保系统的安全运行,并最大限度地提高DG的利用效率。仿真结果和理论分析表明,新保护方法可提高DG与配电网的协调性,并可有效提高DG的利用效率。