Valuation of distributed energy resources in active distribution networks

In concert with the transformation of conventional passive power distribution system, distributed energy resources (DERs) have progressively become participants in the provision of electricity services in active distribution networks (ADNs). In this paper, we propose a systematic valuation process to quantify the value of DERs in the ADN context. The paper first provides comprehensive insights into the impacts of DERs on ADN and the society as a whole. Given the technological, locational, and temporal diversity of DERs, a two-part scheme is developed to value and compensate DER portfolios proposed by customers and independent third parties. In particular, DERs are valued for their benefits and costs in both short and long terms. An integrated resource planning model is formulated to quantify the value of a given DER portfolio to be installed, where bi-level optimization techniques are applied to coordinate decisions on ADN planning and operations. In order to determine the short-term operation benefits of the DER portfolio on a continuous basis, a retail market operation model is developed based on peer-to-peer energy transactions among prosumers, when the impacts of DERs on ADN operations are monetized by distribution locational marginal prices. It is finally concluded in the paper that the proposed valuation scheme will not only contribute to the proactive investment of DERs in ADN but also help enhance the role of DERs in offering affordable, reliable, resilient and sustainable electricity services to customers.     

分布式能源提供未来辅助服务的技术能力

近年来,分布式能源技术（Distributed Energy Resource）得到了快速发展。分布式能源（DER）系统具有可靠、高效、清洁、环保、配置灵活等优势,有着巨大的发展潜力,因此研究分布式能源技术具有重要的理论意义和重大的应用价值。概述了国内外分布式能源的发展现状及应用前景,简要介绍了分布式能源的概念、技术和特点,分析了DER提供当前和未来的辅助性服务（频率控制、电压控制、拥塞管理、电能质量提高、网络恢复、孤岛操作和电网损耗优化）的控制能力（分布式发电机DGs,存储和加载）。主要重点是对技术能力的评估。此外,通过DER系统的电网连接技术分析了这种技术方法,因为不同类型的电网连接技术可以应用在同样的DER系统中,而且电网连接技术决定了整个DER系统的许多功能。     

Sensitivity-based locational marginal value calculations in distribution grids

Electric utilities are experiencing a rapid growth of distributed energy resource (DER) deployment in their distribution grids. DERs can result in operational challenges in distribution grids, while at the same time can be viable assets in helping electric utilities better plan and manage grid design, operation, and planning. The DER valuation becomes an extremely important factor in this situation to ensure that DERs are fairly and accurately valued for the services they provide. This paper investigates the idea of spatiotemporal valuation of DERs and develops a sensitivity-based locational marginal value (LMV) calculation method that can be solved without the need for solving the network power flow problem. Furthermore, the impact of cost allocation to various upgrades in the system on LMV calculation is investigated, with the goal of demonstrating the fairness of the proposed LMV calculation method. The proposed model is applied to a standard test system for evaluation and validation.     

基于IEC 61850的DER并网监控信息模型研究

DER(Distributed Energy Resources)并网需要解决的问题之一是DER与整个配电网系统的信息采集和交互。以IEC61850标准为基础,研究DER并网监控的信息内容,设计了一种基于IEC 61850的综合并网监控信息模型。该模型采用面向对象的抽象方法,将DER并网监控系统各设备抽象为逻辑功能节点,分析DER接入10 kV配网的监控信息流,定义了各信息所属的数据对象,建立逻辑设备节点信息模型。最后以PV(Photovoltaic System)并网为例,选取发电子系统和并网点的典型逻辑节点,建立了不同并网状态下的综合信息模型。     

基于IEC 61850-7-420标准的DER通信及控制通用接口设计与实现

为了提高分布式能源通信及控制功能的扩展性与互操作性,针对分布式能源的信息模型构建与信息交互,提出了一种基于IEC 61850-7-420标准的分布式能源通信及控制通用接口,给出了通用接口具体的设计与实现方法。开发了通用接口实际的智能电子设备,并基于构建的多分布式能源集成测试平台,对分布式能源通信及控制功能进行了相应的实验测试。研究结果表明,通用接口的设计与实现方法切实可行,分布式能源在其状态信息、设置、控制以及测量/计量值等方面能够实现快速、准确的信息交互,为分布式能源系统集成提供有效的技术手段和解决方案。     

智能营销研究概述(四)——DER带来的变革

分布式能源(DER)的快速发展和大规模应用将给智能营销带来新的机遇和挑战.基于智能电网技术路线提出DER发展展望,引入计及分布式发电单元的3级控制信息管理、电量消纳原理、虚拟营销、需求侧引导等全新概念,重点阐述其对智能营销带来的变革.最后针对我国智能电网发展愿景、能源利用等热点问题对DER参与下的智能营销做深入思考,提出其建模、接入权等问题,探讨了包含DER框架下的智能营销发展前景和研究方向.     

Increasing DER integration through discrete intraday settlements

Deployment of distributed energy resources (DERs) is accelerating across the United States. These assets have the potential to provide cost-effective grid services and bulk power while supporting a low-cost energy transition to carbon-free electricity. Full integration of these resources into the bulk power system remains a barrier to unlocking the potential value of these assets. The regional wholesale energy markets, originally designed to integrate centralized, dispatchable power plants, must be reformed to adapt to the changing potential resource mix. The current day-ahead and real-time system is poorly designed for DERs. Day-ahead DER forecast errors create exposure to real-time price variations, as resources committed in the day-ahead market are required to rebalance in real-time, challenging the business model for DERs. New intraday markets with multiple discrete intermediate auctions between the day-ahead market and real-time market are needed to enable proper integration of DERs and efficient mitigation of forecast uncertainty risk. These markets must incorporate financially-binding commitments, closer-to-dispatch price signals, and adequate liquidity to ensure competition. Intermediate auctions should be built on top of existing intraday processes in each regional market, incorporating the principles of the existing market structures and leveraging the benefits of the centralized dispatch systems. Regional transmission organization (RTOs) and Independent System Operators (ISOs) should pursue and implement intermediate auctions to support fair, open, and efficient markets in the U.S.     

Energy requirement for distributed energy resources with battery energy storage for voltage support in three-phase distribution lines

Integration of distributed energy resources (DER) into distribution systems is a new concept for improving system capacity and stability, feeder voltage, and supply quality and reliability. This paper has addressed voltage support in distribution systems by energy injection from a battery storage distributed energy system. An operation strategy for an inverter interface battery energy storage DER has been developed for maximum improvement in feeder voltage with minimum energy injection from the DER. A control strategy has been proposed for inverter based battery storage DER to regulate network voltage effectively, through operating the DER to generate real (P) and reactive (Q) power with Q priority. The implementation of the inverter interface DER with battery energy storage will save fuel cost of DER but be of much higher capital cost than using a rotary generator. The proposed technique has been evaluated by simulation on a three-phase distribution system with time varying loads. Test results indicate that DER operating with Q priority offers the best solution for maximum voltage improvement. The results also confirm that DER injecting P and Q at the ratio of maximum voltage sensitivity of line presents better solution for power loss reduction than the solution offered by the DER operating with Q priority.     

孤岛状态下含分布式电源的配电系统可靠性分析

分析了孤岛状态下含分布式电源的配电系统可靠性。针对配电网孤岛运行的特点,提出了可靠性分析的复合随机性负荷模型,提出了既能反映系统充裕度又体现动态特性的可靠性计算方法和衡量指标。计算结果表明,所提的模型、计算方法和衡量指标能充分反映分布式电源在不同程度上提高配电系统的可靠性,为系统的规划设计提供了重要参考。     

From microgrids to aggregators of distributed energy resources. The microgrid controller and distributed energy management systems

Microgrids are a collection of distributed energy resources (DER) within a specific boundary, with a control system for their management and operations at the point of interconnection with the distribution utility. As microgrid concepts evolve, they are being applied to aggregations of DER outside boundaries with appropriate controls for operation with transmission and distribution utilities and participation in markets. This article marks this evolution and points towards the common functionalities of microgrid controllers and distributed energy management systems for integration of DER into transmission and distribution operations and markets.     

Analysis and visualization method for understanding the voltage effect of distributed energy resources on the electric power system

While adding distributed energy resources (DER) to a distribution circuit will affect numerous aspects of operation, bus voltage is a critical aspect that must be maintained within acceptable limits. It is therefore critical to: (1) quantify how DER installation will affect the voltage, (2) visualize the voltage change, and (3) predict the voltage change of the alternatives within the DER operational space. These three goals are achieved through the development of a simple voltage change potential (VCP) visualization method that can be determined using the basic characteristics of an inverter-based DER installation. The VCP results compare favorably with equivalent complete non-linear Matlab/Simulink™ models of DER implementation in distribution circuits at a fraction of the computational time. Calculation of VCP also enables a new control method that uses circuit information and simple equations to provide situation-dependent and optimal voltage regulation.     

Active distribution network fault location methodology: A minimum fault reactance and Fibonacci search approach

Active Distribution Networks (ADN) are defined as distribution networks with presence of Distributed Energy Resources (DER). In this paper, a Fault Location (FL) analytical methodology for active distribution networks is presented. The proposed technique combines the minimum fault reactance concept and a Fibonacci search method to estimate the fault location. Synchronized current phasors provided by Intelligent Electronic Devices (IED) located at the DER units are considered. A ladder-based technique is proposed and used to estimate the current contribution of each DER to the fault point. Proposed analytical methodology is applicable for all DER types without need to know its individual parameters and model. Validation is made using the IEEE 34-nodes test feeder. Test feeder is modeled using ATP/EMTP software and modified with the addition of several DER. Test results show the robustness of the methodology, indicating its potential for real-life applications.     

Resolving the conflict between new and old: A comparison of New York,California and other state DER proceedings

Distributed energy resources present opportunities to serve grid and customer need through two-way power flow. New values, methods, and planning are required to efficiently interconnect and utilize DERs. This paper analyzes New York’s and California’s DER proceedings to provide a comparison of the similarities and differences between these and other states that will result in different levels of deployments and valuations of DERs.     

One metric to rule them all: A common metric to comprehensively value all distributed energy resources

Traditional energy and demand savings metrics for distributed energy resources (DER) do not accurately describe the value of DERs to meet future energy needs, minimize grid investments, maintain reliability, and reduce greenhouse gasses. This problem is exacerbated in an increasingly renewable grid in which DER impact varies significantly with time and location. Moreover, different DERs are also valued using disparate metrics; this fragmented DER valuation and procurement creates process and economic inefficiencies. A new path forward is the Total System Benefits metric (TSB); the TSB aggregates all electric system benefits, and relevant environmental externalities that accrue to DERs. The TSB is the only metric that comprehensively values DER’s to meet future electric system needs and environmental policy goals. This common metric will enable electricity planners, regulators, utilities, and implementers to best deploy and track DER to meet electric grid and environmental policy needs. This paper explains why the TSB is the right metric to value all DER, data requirements to develop the TSB, how to express DER in terms of the TSB, and lessons learned so far from California's implementation of the TSB.     

Adaptive coordinated feeder flow control in distribution system with the support of distributed energy resources

This paper aims to minimize the feeder power flow deviation from scheduled value by balancing generation and load demand within the distribution system under various local disturbances. The available distributed energy resources (DER) can be properly utilized to control the feeder flow which gains significant advantages (i) to support load frequency control (LFC) problem at transmission level (ii) reduces unscheduled interchange in feeder which is priced higher (iii) increased reliability of the grid. The deviation in feeder flow is reduced by properly coordinating the power output from DER such as fuel cell, battery storage system and responsive loads (demand response) through an adaptive fuzzy controller with optimally tuned gains using particle swarm optimization. The level of participation from each DER units are decided using fuzzy inference system based on the availability of resources and level of disturbance. The photovoltaic array and wind turbine are also considered in the system and always operated at the maximum power point. The proposed method is examined on IEEE 37 bus system implemented in the MATLAB based Power Analysis Toolbox (PAT) for performing time-domain dynamic analysis. It is shown that the proposed adaptive controller exhibits better performance for various disturbance conditions.     

以区域能效优化为目标计及不确定因素的分布式能源综合优化配置

分布式能源的大规模应用,可以有效缓解化石能源引起的环境污染和能源危机。针对如何确定分布式能源位置和容量的问题,建立了考虑不确定因素影响的分布式能源综合优化配置模型。模型以规划期内总成本最小为目标,以系统安全运行要求为约束,考虑区域能效优化、低碳目标及分布式能源的建设成本、运行成本和维护成本,并以机会约束规划解决风机、光伏等出力的不确定性及负荷的波动性问题。在确定目标函数的基础上,采用基于蒙特卡洛模拟嵌入量子粒子群算法来求解该NP难问题,较粒子群算法在搜索效率和搜索能力上均有较大提升。通过对IEEE 37-bus配电系统的分析,表明所建模型能够较好地解决不同资源水平、经济发展程度地区分布式能源的选址与定容问题。     

一种分布式电源并网监控通信适应性评价方法

分布式电源(DER)与配电网之间以及DER之间的通信不畅,会导致DER并网后对电网的电能质量、继电保护、孤岛问题产生不利影响,进一步影响整个电网的经济性和安全性。文中综合考虑技术性、经济性、适应性、扩展性和对DER的支撑性,设计了一种DER并网监控的解决方案,并提出了含DER的配电网通信方式适应性评价指标体系。根据DER并网监控通信需求,提出一种模糊一致的层次分析评价方法,并选择多种通信方式进行适应性评价。该评价方法结合了主客观需求,为含DER并网的配电网通信平台建设提供了可行性依据。     

2011年国际供电会议系列报道:分布式能源发展与用户侧电能的高效利用

对第21届国际供电会议的分布式能源(DER)与高效用能专题进行了梳理,围绕分布式电源(DG)/DER规划及研究、含DG/DER的配电网控制、用户侧发展及DG/DER技术4个方向详细归纳并介绍了世界范围内在该领域研究工作的重点、难点与进展情况。所述内容希望能够开拓中国学者在相关研究领域的视野,加深对当前配电网所面临的问题、机遇与挑战的理解,并最终推动国内智能配电网相关技术的研究、开发与工程应用。     

基于贡献度分层的主动配电网供电能力评估

主动配电系统（active distribution system,ADS）的供电能力（power supply capacity,PSC）受配电网络的拓扑结构、元件故障、负荷水平及分布式能源资源出力波动性等诸多不确定性因素的影响。为快速评估中长期配电网的供电能力,首先从影响中长期供电能力的因素入手,对分布式电源（distributed energy resource,DER）、负荷出力进行了不确定性建模,采用贡献度分层抽样算法进行抽样,得到具有代表性的样本,对于元件运行的不确定性,基于线路重要度进行网络不确定性建模;其次,定义了适用于中长期供电能力评估的指标;最后,采用改进的IEEE 14节点算例进行验证,通过与传统蒙特卡洛法的对比证明本文所提模型及算法的正确性和有效性。     

配电网节点边际容量成本及应用

分析了现有配电网边际容量成本的不足。通过将支路增量成本合理地分摊到各负荷节点,提出配电网节点边际容量成本（LMCC）的概念,反映未来各节点负荷占用供电容量的成本。LMCC基于配电网供电容量的利用现状和负荷增长趋势,并不依赖于未来规划网架,因而具有较强的可操作性。最后,讨论了LMCC在配电网规划、容量定价、需求侧管理和分布式电源接入中的应用前景。