Types of the National Markets of Ancillary Services and Balancing Energy

Modeling of ancillary services market can be described as institutional arrangements for establishing ancillary services management in deregulated electricity market. Models of the national ancillary services markets are market models which offer transmission system operator efficient procurement of ancillary services, reducing the system management risk, more competitive electricity market, better utilization of production facilities and complete deregulation of electricity markets. This paper deals with current mode of ancillary services market and potential market development in Croatia. Described models are used for establishing market of ancillary services which should occur in parallel with the electricity market.

Mechanism Design for Ancillary Service Market Considering Social Welfare and Fairness

Increasing penetration of distributed energy resources in the distribution network(DN)is threatening safe operation of the DN,which necessitates setup of the ancillary service market in the DN.In the ancillary service market,distribution system operator(DSO)is responsible for safety of the DN by procuring available capacities of aggregators.Unlike existing studies,this paper proposes a novel market mechanism composed of two parts:choice rule and payment rule.The proposed choice rule simultaneously considers social welfare and fairness,encouraging risk-averse aggregators to participate in the ancillary service market.It is then formulated as a linear programming problem,and a distributed solution using the multi-cut Benders decomposition is presented.Moreover,successful implementation of the choice rule depends on each aggregator’s truthful adoption of private parameters.Therefore,a payment rule is also designed,which is proved to possess two properties:incentive compatibility and individual rationality.Simulation results demonstrate effectiveness of the proposed choice rule on improving fairness and verify properties of the payment rule.

Design of Robust Var Reserve Contract for Enhancing Reactive Power Ancillary Service Market Efficiency

In a deregulated Var market, market power issue is more serious than in an energy market since reactive power cannot be transmitted over long distances. This letter designs a multi-timescale Var market framework, where market power that may arise in the hourly-ahead Var support service market due to system configuration deficiency and market structure flaws can be eliminated by day-ahead contract-based Var reserve service market. Settlement of day-ahead Var reserve contract is formulated as a two-stage robust optimization (TSRO) model considering worst case of uncertainty realization and potential market power that may arise in hourly-ahead market. TSRO with integer recourses is then solved by a new column and constraint generation algorithm. Results show a robust Var reserve contract can fully eliminate market power, and prevent suppliers from manipulating market prices.

A Simulation of Market-based Non-frequency Ancillary Service Procurement Based on Demand Flexibility

This paper proposes a novel approach for the provision of non-frequency ancillary service(AS)by consumers connected to low-voltage distribution networks.The proposed approach considers an asymmetric pool-based local market for AS negotiation,allowing consumers to set a flexibility quantity and desired price to trade.A case study with 98 consumers illustrates the proposed market-based non-frequency AS provision approach.Also,three different strategies of consumers’participation are implemented and tested in a real low-voltage distribution network with radial topology.It is shown that consumers can make a profit from the sale of their flexibility while contributing to keeping the network power losses,voltage,and current within pre-defined limits.Ultimately,the results demonstrate the value of AS coming directly from end-users.

Dispatch and bidding strategy of active distribution network in energy and ancillary services market

The active distribution network(ADN)is able to manage distributed generators(DGs),active loads and storage facilities actively.It is also capable of purchasing electricity from main grid and providing ancillary services through a flexible dispatching mode.A competitive market environment is beneficial for the exploration of ADN’s activeness in optimizing dispatch and bidding strategy.In a bilateral electricity market,the decision variables such as bid volume and price can influence the market clearing price(MCP).The MCP can also have impacts on the dispatch strategy of ADN at the same time.This paper proposes a bilevel coordinate dispatch model with fully consideration of the information interaction between main grid and ADN.Simulation results on a typical ADN validate the feasibility of the proposed method.A balanced proportion between energy market and ancillary services market can be achieved.

MILP Optimization Model for Assessing the Participation of Distributed Residential PV-battery Systems in Ancillary Services Market

A novel non-linear stochastic method based on a Mixed-Integer Linear Programming(MILP)optimization model is proposed to optimally manage a high number of photovoltaic(PV)-battery systems for the provision of up and down regulation in the ancillary services market.This method,considers both the technical constraints of the power system,and those of the equipment used by all the prosumers.This allows an aggregator of many residential prosumers endowed with photovoltaic(PV)-battery systems to evaluate the baseline of the aggregate by minimizing the costs related to the electrical energy absorbed from the grid and then to assess the up and down flexibility curves with relative offer prices.As confirmed by simulation results carried out considering different realistic case studies,the method can effectively be used by an aggregator to evaluate the economic impact of its participation in the ancillary services market,both for the aggregator and for its prosumers.

Economic potentials of energy storage technologies in electricity markets with renewables

The increasing penetration of renewables in power systems urgently entails the utilization of energy storage technologies.As the development of energy storage technologies depends highly on the profitability in electricity markets,to evaluate the economic potentials for various types of energy storage technologies under the compre-hensive market environment is of great significance.To this end,this study aims at conducting a quantitative analysis on the economic potentials for typical energy storage technologies by establishing a joint clearing model for electric energy and ancillary service(AS)markets considering the operating features of energy storage systems(ESSs).Furthermore,a test system is adopted for numerical analysis that accurately represents for the real-world operation characteristics of power systems in China,with which the market prices,and operation schedules and profitability of ESSs are comparatively studied.The proposed methodology and results could provide benefi-cial references for the modifications on electricity markets and the development of ESSs towards the increasing penetration of renewables in power systems.

The operating schedule for battery energy storage companies in electricity market

This paper presents a series of operating schedules for Battery Energy Storage Companies(BESC)to provide peak shaving and spinning reserve services in the electricity markets under increasing wind penetration.As individual market participants,BESC can bid in ancillary services markets in an Independent System Operator(ISO)and contribute towards frequency and voltage support in the grid.Recent development in batteries technologies and availability of the day-ahead spot market prices would make BESC economically feasible.Profit maximization of BESC is achieved by determining the optimum capacity of Energy Storage Systems(ESS)required for meeting spinning reserve requirements as well as peak shaving.Historic spot market prices and frequency deviations from Australia Energy Market Operator(AEMO)are used for numerical simulations and the economic benefits of BESC is considered reflecting various aspects in Australia’s National Electricity Markets(NEM).

Generalized Energy Storage Allocation Strategies for Load Aggregator in Hierarchical Electricity Markets

The uncertainty of user-side resource response will affect the response quality and economic benefit of load aggregator(LA).Therefore,this paper regards the flexible user-side resources as a virtual energy storage(VES),and uses the traditional narrow sense energy storage(NSES)to alleviate the uncertainty of VES.In order to further enhance the competitive advantage of LA in electricity market transactions,the operation mechanism of LA in day-ahead and real-time market is analyzed,respectively.Besides,truncated normal distribution is used to simulate the response accuracy of VES,and the response model of NSES is constructed at the same time.Then,the hierarchical market access index(HMAI)is introduced to quantify the risk of LA being eliminated in the market competition.Finally,combined with the priority response strategy of VES and HMAI,the capacity allocation model of NSES is established.As the capacity model is nonlinear,Monte Carlo simulation and adaptive particle swarm optimization algorithm are used to solve it.In order to verify the effectiveness of the model,the data from PJM market in the United States is used for testing.Simulation results show that the model established can provide the effective NSES capacity allocation strategy for LA to compensate the uncertainty of VES response,and the economic benefit of LA can be increased by 52.2%at its maximum.Through the reasonable NSES capacity allocation,LA is encouraged to improve its own resource level,thus forming a virtuous circle of market competition.

Heat Pumps in Denmark:Current Situation in Providing Frequency Control Ancillary Services

-The Danish government set an ambitious goal to achieve a fully renewable-based energy system by 2050.In this context,the integrated electricity and heating system is undergoing rapid development in Denmark as a promising way to accommodate the ever-growing renewable energy sources(RESs).The electric heat pumps(HPs),coupled with the power and heat sectors,can propagate the flexibility on the heat consumer side to the power system operations,playing an important role of improving system flexibility and balancing the variability of the RES.In this paper,the current development situation of HPs in Denmark is analyzed,including both the large-scale HPs in the district heating system and individual HPs on the residential side.The possibility of using HPs to provide frequency control ancillary service(FCAS)is analyzed according to the market and technical requirements of the FCAS in the Danish transmission system and experimental results of representative demonstration projects of HPs.A comprehensive analysis of the advantages,barriers,future prospects,and challenges for using HPs to provide the FCAS are carried out from the perspectives of different entities.

Optimal operation strategy for distributed battery aggregator providing energy and ancillary services

The high penetration of distributed renewable energy raises a higher concern for the safe and economic operation of the smart grid. Distributed batteries equipped in demand-side can not only contribute to the reliability and security of the grid, but also make profits by participating in the electricity market, especially when distributed batteries are combined and operated by an aggregator.Considering the well-operated mechanism of performance based regulation(PBR) in the U.S. electricity market, it becomes increasingly lucrative for batteries to participate not only in energy markets for energy arbitrage, but also in ancillary service markets to provide regulation and peakload shaving services. In this study, distributed batteries are operated and coordinated by the aggregator, which simultaneously submits offers to the energy and the ancillary service markets as an individual entity. An optimaldecision model is formulated for the aggregator to determine the operation and bidding strategy for the distributed batteries by considering the characteristics of batteries,including the terms of capacity, efficiency and degradation cost. Finally, a numerical case is conducted to evaluate the benefits of the decision model.

Experiences of the Electricity System Operator Incentive Scheme in Great Britain

National Grid is the electricity system operator in Great Britain and has an unique feature in so far as it is one of the world’s few for-profit system operators. In addition, the commercially orientation of the British market rules means that nearly every action taken by National Grid to operate the system has a cost associated to it. Based on those factors and in order to encourage National Grid to seek continuous improvements and drive for efficient and economic system operation, the regulator (Ofgem) offers an incentive scheme, whereby a target is agreed annually and any savings in relation to this target are shared between consumers and National Grid in the form of a profit. It is in National Grid’s best interest to have mechanisms to mitigate the impacts of volatility in the costs it faces as system operator so that it can implement cost saving actions without the risk of windfall losses (or gains) arising from sudden changes in uncontrollable drivers. The purpose of this paper is to share the experiences of National Grid in the operation of Great Britain's electricity system, with a special interest on the mechanisms created to manage the associated costs in response to the incentive scheme. It does so by describing the market operation in Great Britain and the costs drivers impacting National Grid’s system operation and illustrating the steps recently taken by National Grid to propose volatility mitigation mechanisms. It concludes with the rationale and expected results from the latest proposals as consulted with the industry for introduction in the incentive scheme starting on 1st April 2011. It is worth noting that with this work, the authors wish to both share the experience with other system operators and regulators in the world, as well as give British market participants an insight on the inner workings of National Grid.

Evaluation index system of shared energy storage market towards renewable energy accommodation scenario:A China’s Qinghai province context

With the ever-increased installed capacity of renewable energy generation units in a power system,the so-called shared energy storage(SES),a novel business model under the umbrella of the shared economy principle,has the potential to play an essential role in the accommodation of renewable energy generation.However,unified evaluation standards and methods,which can help decision-makers analyze the performance of the SES market,are still not available.In this paper,an evaluation index system of the SES market is designed based on the trading rules of China’s Qinghai province and the structure-conduct-performance(SCP)analytical model.Moreover,the definition and characteristics of the indices,which can show the performance of the SES market from different perspectives,are given.Furthermore,the ideal cases are presented as the evaluation benchmark based on the development expectation of the SES market,and the analytic hierarchy process(AHP)and the technique for order preference by similarity to an ideal solution(TOPSIS)are applied to evaluate the SES market comprehensively.Finally,a case study based on actual data of the SES trading pilot project in Qinghai shows that the evaluation index system can reflect the operation status,existing problems and influencing factors of the SES market.

考虑换电需求响应的换电站参与电能量-调频市场竞价策略

电动汽车(EV)大规模发展会加大电网的调峰调频压力。通过换电站市场化运营,可有效激励换电站利用EV换电需求和换电站电池灵活性资源,缓解电网调峰调频压力。为此,提出了换电站参与电能量市场和调频辅助服务市场的协同竞价策略及其两阶段优化模型。第1阶段依据调频市场需求制定换电价格,引导EV调整换电需求,优化冗余电池数量及时序,以便与调频需求趋势一致,进而提升换电站调频服务收益;第2阶段考虑换电站需求响应和市场调峰调频需求,制定换电站竞价策略。所提出竞价策略在优先满足EV换电需求的同时,可降低换电站充电成本、提升调频服务收益,并助力电网调峰调频。算例仿真结果验证了所提策略的有效性。

Cross-Subsidy in Electricity Tariffs in China

With the incessant development of power market reform,the existing cross-subsidy in electricity tariffs has become a critical problem in China's power industry development.On the basis of the theories of cross-subsidy and electricity universal service,the authors take foreign countries' experience as reference to design several solutions to cross-subsidies in electricity tariffs in different phases of China's power industry development.Furthermore,the application and implementation of these solutions are analyzed in this paper.

山西电力备用辅助服务市场机制设计与实践

电力备用辅助服务市场是反映备用服务价值、引导传统火电和新型主体积极提供备用服务、支撑新型电力系统构建的重要机制。山西在电力现货市场和调频辅助服务市场正式运行的基础上,针对新能源高占比下电网备用灵活调节资源不足的问题,研究提出了主辅协调的正备用辅助服务市场交易机制。在市场机制设计上,山西采用现货电能量市场和正备用市场的总费用最低为目标确定机组组合、再顺次出清备用和电能量市场的半耦合出清协调模式,并给予备用服务供应商除中标容量补偿以外的富余发电容量补偿费用,以充分反映备用服务保供应和促消纳的双重价值。算例分析及山西正备用市场模拟试运行结果表明,备用服务市场建设有利于发现备用调节价值,优化系统调节资源配置,相关成果可为国内备用市场建设提供参考。

考虑不确定性的综合能源供应商日前优化运行策略

综合能源供应商作为多能源供应主体,可以参与市场化交易。为探索综合能源供应商在电力市场环境下新的盈利点,构建了考虑需求响应的多主体互动机制,并充分考虑光伏出力、多元用能需求、市场电价以及需求响应资源潜力的不确定性,采用区间优化方法构建了表征综合能源供应商日前运行优化问题的混合整数线性规划模型,得到综合能源供应商的购能、设备运行以及需求响应资源调用等策略。算例验证结果表明,需求响应机制可以有效降低购电成本,增加综合能源供应商的运行收益。

电力交易产品细分市场协同机理研究

随着电力市场和可再生能源发电技术的发展,国外典型电力市场在建立电能量市场交易机制后,又相继出现了电力辅助服务和容量等多种电力产品细分市场。我国电力市场建设起始阶段恰逢电力系统转型,系统长期充裕性与短期灵活性不足的问题同时凸显,为有效地发挥市场机制在保障电力系统安全稳定、可靠供电和资源优化配置的多重作用,需对电力细分产品市场的协同机理进行研究,以为电力市场的产品结构体系和关键交易机制设计提供理论基础。该文基于电力系统运行的物理规律,运用市场经济理论,揭示了以“功能互补、时序配合、价本互映、收益互斥”为核心内涵的电力产品细分市场协同机理;以加州电力市场发展沿革为例进行了电力交易产品细分市场协同机理实证分析;并基于所揭示的协同机理,结合宁夏电力系统实际和未来发展需要进行了宁夏电力市场的产品结构体系与关键交易机制设计。通过实证分析与规范设计的实例,验证了所揭示协同机理对电力市场的普适性作用,以期为电力市场协同建设提供理论工具。

面向系统响应能力提升的虚拟电厂聚合特性及交易机制综述

在新型电力系统频率动态品质下降、频率稳定问题突出的背景下,文中综述了面向系统频率响应能力提升的虚拟电厂聚合响应特性与市场交易机制,为当前由于市场机制缺乏导致的分布式资源频率支撑技术应用难题提供市场化解决思路。首先,总结了分布式资源频率动态响应基本原理以及虚拟电厂所需关键支撑技术,剖析了虚拟电厂在提供系统频率支撑方面存在的问题。其次,从时间、空间、成本3个维度提炼了虚拟电厂的频率聚合响应特性,并综述了虚拟电厂提升系统频率响应能力的市场交易机制,涵盖产品设计、出清定价、贡献量化、结算考核4个关键环节。然后,探讨了虚拟电厂聚合响应特性与市场交易机制间的交互作用关系。最后,展望了虚拟电厂提升系统频率响应能力的未来研究重点。

电动汽车协助火电机组参与调频辅助服务优化控制策略

高比例可再生能源接入电网使得系统频率控制难度提升,电力系统二次调频面临新的挑战。为此,提出一种电动汽车(electricvehicle, EV)协助火电调频机组参与辅助服务市场的优化控制策略。在调频指令分配比例优化阶段,考虑调频成本及电池补偿成本,最大化调频商收益为目标,提出滚动优化控制策略。在EV充电站响应阶段,考虑站内各EV荷电状态及可调容量,采用分区分级动态调节充放电功率控制方法响应调频责任。最后,搭建含EV电站的两区域互联电力系统模型,对该调频策略的性能及经济性进行仿真分析。结果表明,所提策略有效降低了频率响应偏差,同时提高了调频商的经济收益。