Congestion management with ex ante pricing for decentralized electricity markets

In this paper, the authors present a method and a model for managing transmission congestion based on ex ante congestion prices. Their method is influenced by the yield management approach widely used for airline reservation systems, and their model is built based on the relations between transmission congestion prices and electricity commodity prices that exist for an optimal solution. They formulate the congestion pricing problem as a master problem and the electricity commodity (energy and reserve) pricing as subproblems. Examples are presented to illustrate how a system operator can use this approach to compute ex ante congestion prices and how market operators can determine clearing prices and schedules of forward electric energy and reserve markets.     

基于资源协调的分散优化阻塞管理新算法

将基于资源协调的分散优化算法应用到电力合约市场的阻塞管理问题中。ISO将可能阻塞的线路容量看作公共的全局资源,分配给各合约交易商,并通过与交易商交换必要的信息实现最优的线路容量分配。该分散优化方法中,ISO可在不要求用户私人信息的条件下实现社会效益最优,同时迭代过程中的解总是保持可行,因此更加适用于电力市场环境。该文建立了相应的数学模型,提出求解算法和步骤,并证明了与集中优化解的一致性。最后用IEEE-30节点的算例,验证了该方法的有效性。     

一种阻塞管理分散优化算法的研究

目前输电阻塞管理的研究多基于集中优化算法，而实际生活中市场竞争的参与者是通过分散优化进行竞争的。文中提出了一种用分散优化方法确定阻塞电价的机制，其中每个市场参与者都在系统运行员协调下追求自身利益最大化。分析表明，一定条件下分散优化与集中优化的结果相当接近，而与集中优化相比，分散优化具有更高的市场透明度。IEEE-30节点系统的仿真结果验证了该方法的正确性和有效性。     

Congestion management and transmission rights in centralized electric markets

A new congestion management system is proposed, applied under nodal and zonal dispatches with implementation of fixed transmission rights (FTR) and flowgate rights (FGR), respectively. The FTR model proves to be especially suitable for congestion management in deregulated centralized market structures with nodal dispatch, while the FGR is suitable for decentralized markets. The main contribution of this work is a nontraditional valuation of FGR under a centralized market, such as those present in Latin America, that builds a link between both transmission rights under the same market structure. To accomplish that, a computational model is developed, implementing marginal theory where congestion components are introduced in the pricing model. An application to the Chilean Central Interconnected System indicates that FGR presents advantages over FTR regarding signals on grid use, but its application results in complications that make its implementation unattractive.     

Congestion management impacts on bilateral electricity markets under strategic negotiation

Congestion management design is key to a fair and efficient use of transmission facilities and an improvement of market efficiency. Emergence of bilateral electricity markets provides a more flexible, private and decentralized decision-making scenario, in which the self-interested players autonomously search for counterparts to negotiate profitable transactions. In competitive bilateral markets of imperfect and incomplete information and explicit consideration of the network constraints, which make the markets significantly complex, more sophisticated bargaining strategies and market evaluation tools are imperative to both players and regulators.In this paper, under an assumption of imperfect and incomplete information, evolutionary bipartite complex network theory is employed to develop quantities bidding strategies through a dynamic game, in which the players drive the evolution of the network while maximizing their own utilities with explicitly considering the congestion management results. Resorting to adjustment bids, two congestion management schemes, with and without balancing bilateral transactions, are considered.The approach is illustrated with an application to the IEEE30 test system, assessing the impact of different congestion management schemes on the negotiations, market equilibria, market performance and gaming opportunities for the market participants in congestion managements.     

Coordinated spot market for congestion management of inter-regional electricity markets

The rapid growth of inter-regional trading among electricity markets requires the development of new market-oriented mechanisms for the inter-regional congestion management of such trading. In this paper, we deal with the operation of power systems consisting of several interconnected electricity markets. We propose an alternative approach to inter-regional trade that avoids the flaws of forward markets with explicit auctioning of interconnections capacities. We propose the integration of a forward market with a balancing (spot) market for inter-regional exchanges based on nodal pricing. The interaction of transmission system operators (TSOs) belonging to adjacent markets is efficiently taken into account through a decentralized optimal power flow (OPF), which is solved by interior point methods.     

New models for integrated short-term forward electricity markets

In a typical short-term forward wholesale electricity market where products are auctioned sequentially, one often observes significant market inefficiency and price volatility-thus the growing impetus in developing integrated short-term forward markets where electric energy, reserves, and transmission capacity are auctioned simultaneously. Such markets need new computational methods and models for determining market clearing prices and physical (delivery/consumption) schedules. The purpose of this paper is to examine key aspects of current modeling and pricing methods in short-term forward wholesale electricity markets and to introduce new models suitable for clearing price-based markets of integrated trades of energy, reserve, and transmission. Specifically, an analysis of the impacts of various pricing rules and bidding requirements on market operations is presented, the selection of optimization objectives is discussed, and a new model of transmission congestion and multiproducts simultaneous auction is introduced. Examples are used where appropriate.     

电力市场中市场力的评估与发电竞标策略

提出发电公司竞标价格函数，并构建了在不健全市场下发电公司的竞标模型，在这种竞标模型和竞标价格函数的基础上对市场力加以评估。市场力的评估主要针对供不应求而且具有价格限制的市场。当市场经常出现供不应求的局面时，具有装机容量非常大或市场中主要的市场垄断者或所在地理位置可容易地造成输电阻塞等特性的发电公司，可利用其对市场需求的准确预测，来行使市场力，控制市场价格，从而获取高额的利润。数字仿真结果表明，在市场供不应求和市场供求均衡等2种情况下发电公司实现利润最大化的竞标策略完全不相同，从另一方面看也证实了市场力的存在和表现。     

基于协作拍卖法的跨区域输电阻塞管理

电力改革进一步发展要求开放本地市场，开展跨区交易，促进竞争，提高市场效率，降低电价。区域间联络线的容量限制形成的输电阻塞是影响跨区交易顺利进行的重要因素。该文提出了基于协作拍卖法的跨区域输电阻塞管理方法，适合双边和Pool混合的市场交易模式，并能兼顾区域内存在不同的交易模式。在阻塞调度优化模型中考虑了合同路径和物理路径的不同，利用功率传输分布因子将合同路径转换成物理路径。利用发电转移分布因子将阻塞费用分摊到双边合同，采用潮流跟踪法分摊Pool内部的阻塞费用。改进的IEEE 30节点算例测试了不同输电报价下的阻塞管理效果，结果表明：基于协作拍卖法的阻塞管理方法能够有效地缓解阻塞，并能合理分摊阻塞费用，方法快捷，经济信号明确，适合于不同交易模式共存的跨区交易。     

Congestion rents and FTR evaluations in mixed-pool-bilateral systems

Evaluation of key metrics for congestion management, including the congestion rents and the financial transmission rights (FTR) payoffs, requires the efficient allocation of transmission services and the calculation of appropriate locational marginal prices (LMPs). This requirement is particularly acute when there are bilateral transactions coexisting with the centralized pool markets. We propose a new formulation for this purpose, which captures explicitly the contribution of the bilateral transactions to the social welfare. The proposed formulation effectively integrates the pool market and the bilateral transactions on a consistent basis and results in the more efficient allocation of the transmission resources than the conventional tool. We assess analytically the capabilities of the proposed formulation and solution and quantify the improvements in the evaluations over those done using the conventional approach. Such improvements are also illustrated using simulation results on a wide range of test systems including the IEEE 118-bus network.     

Performance indices to measure and compare system utilization and congestion severity of different dispatch scenarios

In competitive electricity markets, energy Locational Marginal Prices (LMPs) are commonly used to allocate energy payments and transmission congestion charges and credits. In these markets, energy prices and transmission pricing are highly affected by transmission constraints, where a congested transmission is accompanied by congestion costs, lower system utilization, and higher energy prices due to resorting to out-of-merit order as expensive generating units are dispatched to alleviate congestion. The paper presents some performance indices to compare different dispatch options, where it proposes to use some congestion and system utilization measures. These measures are used in the paper to indicate level of system usage and congestion severity under different dispatch scenarios, and may enable the system operator or the qualified dispatch decision-making entity to decide which dispatch, among different dispatch scenarios, is the optimal. To show an example of using presented measures, planned line switching has been used to minimize transmission congestion cost and increase system utilization. The model used for energy market in the paper involves both spot (pool) transactions and firm bilateral contracts. The presented method is applied to a three-bus and an eight-bus test systems, where the results show that considering opening of some transmission lines may improve outcome of social-welfare problem, as reflected in reducing total congestion cost and improving system utilization.     

Transmission access and pricing with multiple separate energyforward markets

California's congestion management protocols provide comparable access and prices to all users of the transmission system (power exchange and bilateral contract parties). The users implicitly bid for capacity on major transmission paths between zones. The independent system operator (ISO) allocates the available transmission capacity on these paths so that it maximizes the value of this capacity as measured by the users' bids. Everyone scheduling flow on a congested path is charged the marginal-cost-based price for using the path. The ISO keeps each party's portfolio of generation and load individually in balance when adjusting schedules to relieve congestion on interzonal paths. By keeping the portfolios of the different parties separate, the ISO clears its transmission market without arranging energy trades between parties. Parties are responsible for arranging their own trades. The ISO does not become involved in the energy forward markets     

An optimal pricing scheme in electricity markets by parallelizing security constrained optimal power flow based market-clearing model

To improve economic efficiency of electricity markets, the market-clearing model must be designed to give transparent information for pricing system security and to quantify the correlation between the market operations and the power systems operations, which is an immensely provocative and challenging issue in electricity markets. This paper sets out to propose a novel approach to pricing the system security by parallelizing the security constrained optimal power flow (SCOPF) based market-clearing model, while providing market solutions as a function of complying with the required voltage security margin and N-1 contingency criteria. The proposed SCOPF based market-clearing framework also takes into consideration the bilateral transaction information and, at the same time, optimal pricing expressions through computing locational marginal prices (LMPs) and nodal congestion prices (NCPs) for ensuring voltage security are derived. The results from a 129-bus model of the Italian HV transmission system turn out to be the validity of the proposed market-clearing model for managing and pricing the system security.     

电力市场中区域电价综合模型

安排发电计划、进行网络阻塞管理以及相应价格的制定是电力市场的基本职能,应将三者集中协调。区别于传统的单时段电价模型,文中所提出的区域电价模型考虑了发电计划各时段之间的耦合约束(如爬坡约束),并提出了一种简单、实用的区域划分方法。建立了区域电价的综合模型,该模型包括3部分：电能交易出清、电价区域划分、解决网络阻塞的同时产生区域电价。通过RTS-24系统和中国某实际系统的验证,所提出的分区方法是合理、可行的,由此产生的电价信号能提高输电资源利用效率,引导发电商合理投资。     

Marginal Loss Pricing for Hours With Transmission Congestion

Nodal electricity prices are designed to send efficient economic signals to market participants for operating and investment decisions. The inherent nonlinearity of transmission losses and the use of marginal loss pricing can obscure the intended economic information in the loss component of nodal prices. As one step in clarifying the determination of the marginal loss price component, this paper discusses the calculation of nodal electricity prices in lossy networks and presents a variety of accepted methods for determining marginal loss. This paper then proposes a method for calculating the marginal loss component of nodal prices during hours with congestion that reflects each market participant's contribution to marginal losses more accurately than current implementations. The proposed method recognizes that increases in incremental energy flows cannot flow across constrained lines, and thus, system-wide marginal losses should not be attributed to generators or loads in the constrained subregions. The objectives of the discussion are to improve the understanding of how marginal losses are determined and also to improve the accuracy of the information conveyed in the marginal loss price component. The ultimate goal is to promote more efficient price signals to electricity market participants for both transmission loss and congestion.     

A Standard Market Design for Regional Transmission Organizations

To attain FERC's goals for efficient competitive markets, RTOs should be encouraged to adhere to the foundation principles set forth in a Standard Design based on a bid-based, security-constrained economic dispatch, coordinated by the RTO, with the market prices used for settlement defined by locational marginal costs.     

FTR-option formulation and pricing

Recent changes in electricity markets have advocated the use of Local Marginal Prices (LMP) for congestion management and pricing. From the perspective of market participants, the LMPs pose a risk since they are not known before a transaction on the grid is made. Financial transmission rights (FTR) are instruments that help market participants hedge this risk and are issuable in two flavors—obligations and options. While pricing obligations are much easier, pricing FTR options pose a significant challenge. In this paper we develop a computational method for pricing FTR options. We also discuss the problem of designing financial instrument sets that assure revenue adequacy for the issuer. We point out the difficulty in assuring revenue adequacy when FTR options are present and propose a scheme for overcoming the difficulty. The proposed pricing method can be used to compute prices of options and obligations in the primary market or as a reliable pricing tool to compute option prices in the secondary market. Finally using a test network we present and discuss numerical results.     

考虑输电阻塞的电网固定成本分摊核仁法

探讨了电力市场环境下多区域互联电网固定成本的分摊问题，给出了固定成本分摊的合作博弈模型。针对输电固定成本分配的核仁模型未考虑输电阻塞的情况，提出了一种区域核仁算法。首先根据系统潮流分布情况确定出现阻塞的线路，再根据节点边际价格的差异将输电网划分成多个输电区域，每个输电区域所有节点边际价格基本一致，区域内部线路没有阻塞；然后采用等值双边交易法将输电固定成本分配给各输电区域；最后在区域内部采用核仁模型将成本分配到用户。该方法考虑了阻塞并减小了将多区域互联电网作为一个整体求核仁解时的计算量。以IEEE14节点系统为例的仿真结果表明了该方法的可行性。     

基于猜测价格函数的混合输电权竞价策略分析

作为市场参与者规避阻塞价格风险的工具,输电权已被成功应用于多个电力市场。文中基于猜测价格函数,提出了一种混合输电权竞价策略的分析方法。在所建模型中,竞标个体可以购买任意组合的义务型金融输电权（FTR）、期权型FTR和关口输电权（FGR）,其策略性竞价行为则通过猜测价格函数进行模拟。将该模型的计算转化为求解一个凸二次规划问题,不仅保证了解的唯一性和存在性,还使得该方法能够用于大规模混合输电权市场中的竞价策略分析。通过算例验证了该方法的有效性。     

考虑跨时段负荷响应的电力市场多时段均衡分析

在电力市场环境下,用户负荷对价格的响应具有跨时段的特性。在计及输电约束的基础上,建立了一个考虑跨时段负荷响应的电力市场多时段线性供应函数均衡模型。该均衡问题是一个具有均衡约束的均衡问题(EPEC),可采用非线性互补方法求解。给出的算例证明了模型的合理性,表明跨时段负荷响应的引入可以缓解由于输电阻塞造成的用电不合理分配,并且能有效抑制发电商的市场力滥用。