Impact of distributed generation on distribution contingency analysis

Alternative energy sources are becoming more cost effective, and many utilities are now providing incentives for alternative power. Placing these alternative energy sources, as well as other smaller traditional energy sources, on the distribution power system, allows the development of a new paradigm related to distributed generation (DG). The size and site of the DG will have an effect on the voltages and operations of the distribution power system in the future. This paper discusses a procedure for evaluating the impact of site and size on both the original distribution power system as well as a reconfigured power system after a fault. Validation of this work is done using the IEEE 37 node distribution feeder and the results and trends are presented.     

A generalized power flow analysis for distribution systems with high penetration of distributed generation

In this paper, the element incidence matrix has been extended to develop a comprehensive three-phase distribution system power flow program for radial topology. Three-phase overhead or underground primary feeders and double-phase or single-phase line sections near the end of the feeder laterals have been considered. Unbalanced loads with different types including constant power, constant current and constant impedance are modeled at the system buses. Substation voltage regulator (SVR) consisting of three single phase units connected in wye or two single-phase units connected in open delta are modeled to satisfy the desired voltage level along the feeder. The mathematical model of distributed generation (DG) connected as PQ and PV buses are integrated into the power flow program to simulate the penetration of DGs in the distribution systems. The proposed method has been tested and compared with different IEEE test feeders result. The developed algorithm has been used to study the impact of both SVR and high penetration of DG on voltage profile and system power losses.     

Short-circuit calculations in networks with distributed generation

Fault level considerations may be an inhibiting factor for the interconnection of distributed generation (DG) to the network, particularly at the medium voltage level. In this paper, the latest edition of the IEC 60909 Standard is applied for the calculation of the resulting fault level in medium and low voltage distribution networks with DG. First, an outline of the IEC calculation methodology is presented, including all relevant equations for DG cases studies. Then the short-circuit contribution of the various DG types is extensively discussed. The application of the methodology is demonstrated on a study case medium voltage distribution network, which includes all representative types of DG sources. Emphasis is placed on the contribution of the upstream system, which is the dominant source of short-circuit current. A discussion is also included on potential measures for fault level reduction.     

基于免疫遗传算法的含分布式电源配网规划

大量分布式电源的接入使配电网规划更加复杂.在限制分布式电源接入总量和考虑多种约束的基础上,建立以配网年费用最小为目标函数的规划模型.针对该模型的特点,采用一种新型免疫遗传算法( IGA)对配电网扩展规划进行优化.该算法综合了免疫系统和遗传算法的优点,可实现群体收敛性和个体多样性间的动态平衡,具有良好的全局收敛能力.分别...     

A Petri net based protection monitoring system for distribution networks with distributed generation

Connection of distributed generation (DG) essentially changes distribution network operation and creates a range of well-documented effects varying voltage levels and short circuit currents. Among others, DG can alter protection system operations in distribution networks, leading to failure of reclosing, disconnection of healthy feeder or prevention of protection operation. This paper proposes a procedure, based on Petri nets and supported by a centralized monitoring architecture for monitoring failures of the protection systems in radial distribution networks. Some case studies applied to a real Italian distribution network proved the effectiveness of the proposed procedure that can therefore represent an effective solution to improve distribution systems reliability in presence of DG.     

A technical evaluation framework for the connection of DG to the distribution network

Technical advances and institutional changes in the electric power industry have resulted in a constantly increasing penetration of distributed generation (DG) resources in the grids. For the connection of new DG installations to the network a variety of factors are taken into account, including technical requirements imposed by utilities to ensure that the DG station does not adversely affect the operation and safety of the network. In this paper, fundamental issues related to the interconnection of DG installations to the grid are discussed and evaluation rules are presented, which address power quality considerations and are suitable for application by electric utility and DG engineers. The attention is focused on the steady-state and fast voltage variations, flicker and harmonic emissions. The simplified evaluation procedures of the paper are largely based on the relevant IEC publications and reflect the current practice of several European utilities. A discussion of the interconnection protection requirements is also included in the paper.     

A procedure for distribution system planning of a large-scale agricultural project

Different mathematical techniques adapting linear, nonlinear, mixed-integer, and network flow programming have been developed over the past decades to solve the distribution planning optimization problem. The high dimensionality of the problem made it in some of practical cases unmanageable by such classical optimization techniques. This gave rise to the application of knowledge based, heuristics, artificial intelligence, and approximate iterative techniques to search for the optimal solution. The problem also was typically perceived from the distribution companies’ perspectives with the objective being to supply sustainable yet cost effective power to multi-objective multi-interest consumers with different damage functions and relatively uncertain data. This paper presents a value-based distribution system planning procedure for large-scale agricultural real life project. This type of distribution planning is characterized not only by high load demand but also with a huge distribution network covering the vast agricultural area. Yet it is a planning for single type of customers who has a consistent developing policy, interest, cost damage function, together with a realistic and less uncertain data. The planning is also perceived from the consumer perspective who may even question the connection to the power utility unless it is proved as cost effective way of power supply. Macro and micro-levels planning is suggested for both overall project and farm modules, respectively. The proposed planning procedure evaluates different feasible alternatives based on life cycle cost while reliability indices and cost of interruption are taken into consideration. The procedure is illustrated on the micro-level for a real life agricultural problem.     

分布式发电对配电网继电保护及自动化的影响

大量分布式发电的并网运行将深刻影响现有配电网络的结构、以及配电网中短路电流的大小、流向及分布,由此给配电网的运行与控制带来多方面的影响.针对基于断路器的三段式电流保护、基于重合器等自动化电器的馈线保护以及基于FTU的配网自动化保护方案,探讨了分布式发电对配电网继电保护以及自动化的影响.     

A novel algorithm for ATC calculations and applications in deregulated electricity markets

In this new deregulated environment, transmission networks should be regulated to ensure a competitive, open, and reliable market, which relies on the implementation of many transmission assessment functions. Among them, a key concept is the ability to quantify accurately and rapidly the capabilities of the transmission system. Accurate ATC values on major interfaces of the system can provide an important index to evaluate system security and reliability.

The main contribution of this paper is to propose a novel algorithm for contingency ATC computation and a sensitivity analysis for system uncertainties. It incorporates linear distribution factors and AC load flow sensitivity-based method in order to calculate ATC values efficiently and speedily considering line outages.     

新能源分布式发电系统储能电池综述

风、光等新能源分布式发电受天气和气候的影响出现间隙性和随机性等使得发电的不稳定缺点正成为阻碍其深度发展的重要障碍。储能技术的发展和应用,打破了风电、光伏发电等的接入和消纳瓶颈问题。介绍了应用于储能系统的主要化学储能电池:铅酸电池、液流电池、钠硫电池和锂电池的技术发展、组成结构和储能原理,详细对比了各种电池的性能及特点,特别对能量密度、功率密度和功率等级进行介绍,这是储能系统电池元件选择的关键,最后对储能电池的应用和发展作了展望。     

Generation expansion planning in electricity markets: A novel framework based on dynamic stochastic MPEC

This paper presents a novel framework for generation expansion planning (GEP) of restructured power systems under uncertainty in a multi-period horizon, which includes generation investment from a price maker perspective. The investment problem is modeled as a bi-level optimization problem. The first level problem includes decisions related to investment in order to maximize total profit in the planning horizon. The second level problem consists of maximizing social welfare where the power market is cleared. Rival uncertainties on offering and investment are modeled using sets of scenarios. The bi-level optimization problem is then converted to a dynamic stochastic MPEC and represented as a mixed integer linear program (MILP) after linearization. The proposed framework is examined on a typical six-bus power network, MAZANDARAN regional electric company (MREC) transmission network as an area of IRAN interconnected power system and IEEE RTS 24-bus network. Simulation results confirm that the proposed framework can be a useful tool for analyzing the behavior of investments in electricity markets.     

Short-term operation planning on cogeneration systems: A survey

This paper presents a survey of the developed researches from 1983 up to 2006 related to the cogeneration systems. The survey is focused on short-term operation planning and papers are grouped according to the most important characteristics. This paper contributes to: (i) give an extensive survey in the area and (ii) mention aspects in the short-term operation planning that have been poorly developed and where future contributions are required.     

Voltage regulation in distribution networks in the presence of distributed generation: A voltage set-point reconfiguration approach

In this paper a control strategy based on predictive control ideas is proposed for reconfiguring on-line the on-load tap changer (OLTC) voltage set-point in electrical medium voltage (MV) power grids in the presence of distributed generation (DG). The idea is that an active management of the set-point can be effective for maintaining relevant system variables within prescribed operative constraints in response to unexpected adverse conditions, e.g. changing loads or generation failures. The voltage set-point reconfiguration problem is formulated as a constrained optimization problem by imposing that the voltages at certain nodes have, compatibly with all prescribed constraints and changed conditions, minimal deviations from their nominal values. Simulation results show that the proposed approach ensures, under certain conditions, feasible evolutions to the overall network whenever critical events occur.     

Multiobjective electric distribution system expansion planning using hybrid energy hub concept

This paper presents a novel approach for optimal electric distribution system expansion planning (OEDSEP) using a hybrid energy hub concept. The proposed method uses an energy hub model to explore the impacts of energy carrier systems on OEDSEP procedure. This algorithm decomposes the OEDSEP problem into three subproblems to achieve an optimal expansion planning of a system in which the investment and operational costs are minimized, while the reliability of the system is maximized. The algorithm was successfully tested in the present research for an urban distribution system.     

Development of an analytical model for generation expansion planning as a tool to provide guidelines for preventing instability in the long‐term electricity market

This paper considers the problem of deciding multiperiod investments for generation expansion planning (GEP) in restructured power systems. This problem has presented a challenge for both market managers and suppliers regarding the stability in the electricity market and minimum income for suppliers over the planning period. In this paper, an analytical model for studying the GEP problem from the viewpoint of a central management entity is presented. The aim of this method is to establish a dynamic balance between energy supply and demand by adjustment of GEP over the horizon of planning so that not only the expected profit is provided for all new generating plants but the long‐term stability in the electricity market is also improved. This analytical model can be utilized by regulatory bodies to obtain some guidelines and thereby to set their policies for improving GEP and preventing instability in the long‐term electricity market. To do so, in this study, the uncertainties of demand and supply have been modeled through two stochastic processes. Furthermore, the market price dynamics and their mutual effects on the GEP's results have been considered. Finally, this nonlinear dynamic optimization problem is solved using a modified genetic algorithm (GA). The efficiency and ability of the proposed method are examined on a test power system. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

无线局域网在配电自动化通信系统中的应用

分析了配网自动化通信系统的构成和特点，结合实际应用的需要提出了无线局域网技术在配电通信系统中的应用。在介绍了无线局域网技术原理的基础上，从网络接口的角度探讨了其在配电通信系统中的应用。作为现有通信方式的一种有益补充，无线局域网技术必将在配电通信系统中得到广泛的应用。     

光伏发电接入智能配电网后的系统问题综述

简述了智能配电网的发展情况和光伏发电系统的应用研究概况,分别从基础研究、网络规划和系统运行等方面分析了光伏发电接入智能配电网后对配电网的影响,重点介绍了光伏电站建模、基本运行特性、光伏电站建设规划及出力预测、含光伏电源的智能配电网规划、网络潮流、电压与无功平衡、电能质量、继电保护、故障与可靠性、微网动态特性、优化调度与协调运行等内容,以期为光伏电源接入智能配电网、促进智能电网快速发展提供参考。     

A theory of maximum capacity of distributed generators connected to a distribution system using electric power density model

Recently, the number of distributed generators (DGs) connected to distribution systems has been increasing. System operators should know the maximum capacity of DGs that can be connected without problems to one feeder of the system in order to control the system appropriately. Many studies of the maximum capacity of the DG have been presented, but they have produced limited results calculated by a typical or average‐value model. However, many DGs will access one feeder if deregulation of the electric power industry is accelerated in the near future. In order to deal with this situation, the authors have derived a general formula to calculate the range of the maximum DG capacity per feeder. Copyright © 2004 Wiley Periodicals, Inc. In order to deal with sets of DGs that are dispersed completely on the distribution line, the authors have derived a differential equation for the complex power and one for the voltage drop, which are expressed as functions of distance from the substation. The general formula to calculate the range of the maximum DG capacity connected to the system is determined by solving these equations under the constraints of the line voltage, the line current, and the power factor of the DGs. By a numerical analysis, the authors have calculated the maximum capacity of DGs depending on many parameters, such as the length of the feeder, the DG power factor, and the like. In a short‐length system, the maximum DG capacity is governed by the current constraint, but in a long length system, it is governed by the upper voltage constraint. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(3): 18–28, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20330     

Integration of a hybrid fuel cell-battery system to a distribution grid

In order to integrate a proton exchange membrane type (PEM) fuel cell system (FCS) combined with a battery bank to a distribution grid; this paper proposes a local controller based on fuzzy logic. The proposed system provides primary frequency control and local bus voltage support to the local grid. This opposes the passive distributed generation of the present that do not provide auxiliary services, such as back-up power, voltage support and reliability of supply as they operate under constant power factor equal to 1 at all times. During network disturbances, the distributed generations of the present are disconnected until normal operation is reestablished. When the distributed generation penetration is high this may lead to system instability. The microgrid concept is the effective solution for the control and quality improvement of grids with high level of DG penetration. So, the proposed system, also, can be an active controllable microsource of a microgrid in the future that cooperates with other microsources in order to cover the local load demands for active and reactive power either under grid-connected mode or under islanding operating mode. In cases where the distribution grid (working as microgrid) is forced to operate in islanded mode, the hybrid system provides the demanded active and reactive power. The FCS is connected to a weak distribution grid so that the system performance is studied under the worst conditions. The simulation results are obtained using MATLAB software under a severe step load change where the grid is still connected and under islanded operation. In both cases the system presents a good performance.