Congestion management solution under secure bilateral transactions in hybrid electricity market for hydro-thermal combination

The deregulation of power system has created an environment of competitiveness among different market players and the transmission lines are forced to operate near to their thermal or stability limits. It is a challenge with System Operators (SO) to ensure a secure and reliable transmission of power under these conditions. This paper proposes a rescheduling based congestion management strategy in hybrid (pool + bilateral) electricity market structure for a combination of hydro and thermal units. The proposed congestion management problem has been formulated as mixed integer nonlinear programming (MINLP) problem with an objective to minimize the congestion management cost by suitably rescheduling the hydro and thermal units based on their up and down generation cost bids. The hydro units having lowest operational cost and fast startup time have been used to alleviate the congestion by considering non-concave piecewise linear performance curves for them. The secure bilateral transactions have been ensured while rescheduling of the generators for alleviating the congestion. The performance of the proposed model has been demonstrated by solving the congestion management problem on modified IEEE-24 bus system.     

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     

开放电力市场环境下的动态阻塞管理

提出一种电力市场环境下的动态阻塞管理模式。在这种模式下,具有不同市场属性的市场参与者,进入实时市场中专门设置的动态阻塞管理市场。提供动态阻塞时可用的服务及相应的报价。当动态阻塞发生时,ISO利用动态阻塞管理市场中可用的资源,以系统总的动态阻塞费用最小为原则,进行动态阻塞管理．确保电力系统的稳定运行．同时尽可能减小电力系统动态对电能交易方的影响。文中以IEEE30母线系统为例说明了所提出的市场管理模式。     

电能期货合同市场的输电拥堵定价及其输电网的开放

该文提出了一个输电拥堵管理的新方法，这个方法能确保对所有的输电网使用者公平开放电网，并且对输电价格进行公平定价。首先，输电网使用者对使用区域电网之间的输电线路进行容量投标。然后，电网调度机构(ISO)按照输电网使用者对容量投标的价格来分配输电线路的可用容量，使得输电可用容量的总价值最大化。在一条拥堵的线路上得到输电容量调度计划的用户按照边际成本价格为使用这条线路输电而付费。在ISO为缓解区域之间的输电线路拥堵而调整输电计划时，它要对每个发电商和它们的相应用户之间的输电量分别进行平衡。通过将每对发电商，用户组合的输电业务量分离出来，ISO就可以只组织管理输电市场，而不介入发电商和用户之间双边合同形式的电能交易。     

考虑静态电压安全的输电阻塞管理

在电力系统中,输电网络是电力市场的基础和载体,过负荷或违反静态电压安全指标是输电阻塞的主要表现.阻塞将降低电力市场的公平有序竞争,削弱输电系统稳定性,降低电能质量,增加能量成本.因此,研究由于违反静态电压安全标准引起的系统阻塞问题,对于保证电力市场的正常运行和提高电力系统的效率具有重要的现实意义.考虑有载调压变压器以及可投切电容器组在保证系统安全性方面的重要作用,本文把这两个控制方法引入阻塞管理的优化策略中,与发电机组再调度一起,共同优化以处理由于系统静态电压安全引起的阻塞问题.     

Market-Based Price Differentials in Zonal and LMP Market Designs

The California ISO is redesigning procedures for scheduling, dispatch, and congestion management, which are critical to reliable, nondiscriminatory transmission service. The redesign implements security constrained unit commitment and locational marginal pricing to reflect actual costs of delivering energy, using an accurate network model to price both congestion and losses. CAISO simulations of the market redesign are a unique opportunity to compare a) estimated LMPs if the redesign were in place during recent historical periods with b) actual conditions, as logged in operating records. The study uses market schedules and bids in an alternating current optimal power flow simulation. Resulting LMPs are similar within current congestion zones, but price differences occur during high loads, reflecting actual changes in system conditions. The frequency and magnitude of LMP differences are consistent with the current market, suggesting that the increased market transparency will produce stable, predictable prices. Case studies demonstrate that optimization using SCUC and SCED, coupled with the state estimator, allows more appropriate responses to system conditions, improved utilization of transmission capacity, reduction in congestion costs, and enhanced system reliability.     

Optimal supply curve bidding using Benders decomposition in competitive electricity markets

This paper describes a new approach for optimal supply curve bidding (OSCB) using Benders decomposition in competitive electricity markets. The inclusion of physical unit constraints and transmission security constraints will assure a subsequent feasible solution for the problem. We decompose the problem into a base-case OSCB (without unit and network constraints) and subproblems for checking the feasibility of unit and network constraints. For a given base-case OSCB schedule, line flow violations are minimized by adjusting units’ generation and phase shifters. In case transmission violations cannot be removed, additional linear constraints are introduced in the master problem in the form of price signals for rescheduling OSCB. An IEEE 24-bus system is used to demonstrate the effectiveness of the proposed approach.     

Congestion management with FACTS devices in deregulated electricity markets ensuring loadability limit

This paper addresses an important issue of transmission system congestion management in a pool electricity market environment with the consideration of voltage stability as loadability limit. The optimal generators’ rescheduling has been obtained for three block bid structure submitted to the ISO in a day-a-head market. The base case economic load dispatch has been obtained for generators ensuring the loadability limits and is taken as base case generation output data during the congestion management to obtain new generation scheduling. The generation pattern has been obtained for three bid blocks taking load variation for 24 h considering load scaling factor. The three block bid structure offered to the ISO has been modeled as a linear curve, function of up and down rescheduling within the upper and lower limits offered for congestion management. The impact of third generation FACTS devices has also been studied on the optimal rescheduling of generators’ outputs and thereby the congestion cost. The results have been obtained for IEEE 24 bus and IEEE 57 bus test systems.     

Hydrothermal self-scheduling problem in a day-ahead electricity market

This paper addresses the self-scheduling problem of determining the unit commitment status for power generation companies before submitting the hourly bids in a day-ahead market. The hydrothermal model is formulated as a deterministic optimization problem where expected profit is maximized using the 0/1 mixed-integer linear programming technique. This approach allows precise modelling of non-convex variable cost functions and non-linear start-up cost functions of thermal units, non-concave power-discharge characteristics of hydro units, ramp rate limits of thermal units and minimum up and down time constraints for both hydro and thermal units. Model incorporates long-term bilateral contracts with contracted power and price patterns, as well as forecasted market hourly prices for day-ahead auction. Solution is achieved using the homogeneous interior point method for linear programming as state of the art technique, with a branch and bound optimizer for integer programming. The effectiveness of the proposed model in optimizing the generation schedule is demonstrated through the case studies and their analysis.     

主动配电网与输电网协调调度与阻塞管理

针对主动配电网优化调度的研究局限于配电网内部而未考虑与输电网关系的问题,提出了一种计及阻塞管理的输配电网协调优化调度策略。定义了主动配电网的广义投标函数和对外调节裕度作为输、配电网间协调媒介,对系统进行优化调度,通过潮流计算判断输电网的阻塞支路,在阻塞优化中考虑主动配电网中分布式电源的可调度性,利用节点对线路的灵敏度系数进行阻塞管理,消除线路阻塞。上述问题采用改进的粒子群优化算法解决。利用改编的IEEE30节点系统进行仿真实验,验证了所提输配电网协调优化策略与阻塞管理方法的有效性。     

电力现货市场下输配协同传输阻塞管理

电力现货市场中传输阻塞管理需要协调输电网和配电网可控资源。鉴于虚拟电厂(VPP)具有能够聚合分布式电源(DG)参与电力市场的良好特性,提出了配电网作为VPP参与电力现货市场阻塞管理的输配协同双层优化模型。输电网层综合考虑了由母线电压越限和支路/断面功率越限引起的输电网阻塞,实现了VPP和常规机组的协同优化;VPP层考虑了配电网可控DG和可中断负荷的参与并满足了配电网安全约束。通过2层之间的交互协调,实现了输配全局资源的经济利用、给出了更加合理的价格信号。对由IEEE 30节点输电网和3馈线、16节点配电网组成的输配全局电网算例进行仿真,结果表明了文中模型与方法的有效性。     

Transmission congestion management in an electricity market

Managing transmission congestion in an unbundled electric power system poses a challenge to an independent system operator (ISO). This paper considers an open transmission dispatch environment in which pool and bilateral/multilateral dispatches coexist and proceeds to develop a congestion management strategy for this scenario. Prioritization of electricity transactions and related curtailment strategies are explored and a mechanism for coordination between market participants to achieve additional economic advantages is described     

Optimal power scheduling of thermal units considering emission constraint for GENCOs’ profit maximization

In this paper, authors propose a novel method to determine an optimal solution for profit based unit commitment (PBUC) problem considering emission constraint, under a deregulated environment. In a restructured power system, generation companies (GENCOs) schedule their units with the aim of maximizing their own profit by relaxing demand fulfillment constraints without any regard to social benefits. In the new structure, due to strict reflection of power price in market data, this factor should be considered as an important ingredient in decision-making process. In this paper a social-political based optimization algorithm called imperialist competitive algorithm (ICA) in combination with a novel meta-heuristic constraint handling technique is proposed. This method utilizes operation features of PBUC problem and a penalty factor approach to solve an emission constrained PBUC problem in order to maximize GENCOs profit. Effectiveness of presented method for solving non-convex optimization problem of thermal generators scheduling in a day-ahead deregulated electricity market is validated using several test systems consisting 10, 40 and 100 generation units.     

基于可中断负荷拍卖模型电力双边交易阻塞管理

提出了基于可中断负荷拍卖模型的电力双边交易阻塞管理构架,通过市场机制来确定最优的负荷削减程序.在该构架中阻塞调度过程可以分为三个阶段:调度前阶段、无约束调度阶段和考虑可中断负荷拍卖的阻塞调度阶段.在第三阶段,用户可以向调度机构提交各自的可中断负荷服务报价曲线.构建了阻塞调度模型,综合考虑了最小化所中断的负荷量和最小化向用户支付的可中断负荷服务费这两个优化目标.最后用算例对所提出的阻塞调度模型进行了验证.     

GENCO's Risk-Based Maintenance Outage Scheduling

This paper presents a stochastic model for the optimal risk-based generation maintenance outage scheduling based on hourly price-based unit commitment in a generation company (GENCO). Such maintenance outage schedules will be submitted by GENCOs to the ISO for approval before implementation. The objective of a GENCO is to consider financial risks when scheduling its midterm maintenance outages. The GENCO also coordinates its proposed outage scheduling with short-term unit commitment for maximizing payoffs. The proposed model is a stochastic mixed integer linear program in which random hourly prices of energy, ancillary services, and fuel are modeled as scenarios in the Monte Carlo method. Financial risks associated with price uncertainty are considered by applying expected downside risks which are incorporated explicitly as constraints. This paper shows that GENCOs could decrease financial risks by adjusting expected payoffs. Illustrative examples show the calculation of GENCO's midterm generation maintenance schedule, risk level, hourly unit commitment, and hourly dispatch for bidding into energy and ancillary services markets.     

考虑消除阻塞的分段竞价电力市场出清算法

研究了在发电侧开放的电力市场下,作为电网公司,在保证电网运行的安全性及电能质量的前提下,如何购买各发电厂的电力,使得既满足用户的需要又实现安全性和经济性。提出了一种用灵敏度方法消除阻塞的分段竞价电力市场的出清算法,先在不考虑支路过载的情况下,按各发电机的报价进行竞价,依次安排基荷、腰荷和峰荷段的出力;再选取负荷最大时刻对网络进行阻塞管理,以阻塞调整的费用最小为目标,根据各发电机相对阻塞支路的灵敏度调整各发电机的功率,根据此阻塞管理结果对整体竞价过程进行调整并考虑爬坡约束,通过优化腰、峰荷的分界点,得到考虑消除阻塞的分段竞价电力市场的各发电机出力。这种考虑消除阻塞的分段竞价电力市场的出清算法不仅满足电能生产的连续性,区分了电能质量,体现了市场公平性,而且消除了阻塞,因此其结果更具有实用价值。以IEEE 30节点系统为例,证明了算法的可行性。     

基于市场报价的阻塞管理模型及内点法实现

提出了一种电力市场下解决阻塞问题的新方法,它可以根据市场报价同时调整实时平衡市场下的发电机出力和削减部分短期双边合同量。建立了阻塞管理的非线性数学模型,应用改造的非线性原对偶内点法最优潮流求解以上模型,计算出的节点实时电价体现了如何在各用户中分摊阻塞管理费用。算例表明,该方法可以根据市场参与者的报价得到最优的调度方案,利用节点电价指导用户调整用电计划,从而有效地解决了阻塞问题。     

Comparison of Sen Transformer and UPFC for congestion management in hybrid electricity markets

Congestion management (CM) is one of the most important and challenging tasks of the Independent System Operator (ISO) in the deregulated environment. Recently, Sen Transformer (ST) has emerged as an important power flow control device which has the capability of power flow control over a wide range like UPFC. This device with a conventional transformer and tap changers has the capability of bidirectional control of active and reactive power and can play a very important role in future markets for mitigating the congestion problems. In this paper, the capability of ST has been utilized to manage transmission line congestion for hybrid based electricity market model. The main contribution of the paper is: (i) to develop an optimal rescheduling of generators strategy for real time congestion management and impact of ST for congestion management, (ii) the comparison of ST with unified power flow controller (UPFC) for congestion management, (iii) the secure bilateral transactions determination in a hybrid market model and congestion management with both power flow controllers in combined pool and bilateral market model. The optimal location of ST and UPFC has been obtained solving mixed integer non-linear programming model of congestion management. The proposed model has been applied for results on IEEE 24-bus RTS test system.     

Genetic algorithm-based fuzzy multi-objective approach to congestion management using FACTS devices

This paper investigates a novel optimization-based methodology for placement of Flexible AC Transmission Systems (FACTS) devices in order to avoid congestion in the transmission lines while increasing static security margin and voltage profile of a given power system. The optimizations are carried out on the basis of location, size, and number of FACTS devices. Thyristor Controlled Series Compensator (TCSC) and Static Var Compensator (SVC) are two FACTS devices which are implemented in this investigation to achieve the determined objectives. The problem is formulated according to Sequential Quadratic Programming (SQP) problem in the first stage to accurately evaluate static security margin with congestion alleviation constraint in the presence of FACTS devices and estimated annual load profile. In the next stage a Genetic Algorithm (GA)-based fuzzy multi-objective optimization approach is used to find the best trade-off between conflicting objectives. The IEEE 14-bus test system is selected to validate the proposed approach.     

考虑热泵负荷和分布式光伏的配微网协调调度

随着农村清洁供热改造以及城镇分布式光伏建设的不断推进,配电网中出现了大量农村微电网。分布式光伏的强随机性和波动性给电网的运行调控带来了诸多挑战,电网面临剧烈的潮流波动和严重的电压越限等问题。首先,构建了计及热泵、光伏和储能的配微网分解协调模型,其中热泵用等效状态空间模型描述;然后,提出一种配微网有功无功协调优化方法,并采用改进的Benders分解算法进行求解;最后,在D141-M4算例系统上进行了算例测试。测试结果表明,所提方法可以在保证用户舒适度的前提下,有效降低电网峰值负荷,并提升电压安全水平。