Customer choice of reliability in spinning reserve procurement and cost allocation using well-being analysis

A novel pool-based market-clearing algorithm for spinning reserve (SR) procurement and the cost allocation associated with provision of spinning reserve among customers (DisCos) is developed in this paper. Rational buyer market model is used to clear energy and spinning reserve markets in the proposed algorithm. This market model gives DisCos the opportunity to declare their own energy requirement together with their desired reliability levels to the ISO and also they can participate in the SR market as a interruptible load. The DisCos’ desired reliability levels are selected from a hybrid deterministic/probabilistic framework designated as the system well-being model. Using the demand of each DisCo and its associated desired reliability level, the overall desired system reliability level is determined. The market operator then purchases spinning reserve commodity from the associated market such that the overall desired system reliability level is satisfied. A methodology is developed in this paper to fairly allocate the cost associated with providing spinning reserve among DisCos based on their demands and desired reliability levels. An algorithm is also presented in this paper for implementing the proposed approach. The effectiveness of the proposed technique is examined using the IEEE-RTS.     

电力市场下基于分层可靠性服务的可靠性电价体系研究

利用基于电量不足期望值贡献系数的方法,并结合可靠性灵敏度分析,将事故备用费用分摊到发电侧和输电侧,并形成了相应的发电侧和输电侧可靠性电价。利用模糊聚类分析方法,根据用户的可靠性服务综合指标要求,将系统中的用户划分为几个层次类别,对每层用户进行归一化处理并用一个虚拟用户来代表该层用户的可靠性服务要求,然后根据各层虚拟用户...     

Effects of Load Forecast Uncertainty on Bulk Electric System Reliability Evaluation

Load forecast uncertainty is an important factor in long-range system planning and has been shown to have a significant impact on the calculated reliability indices in generating capacity studies. In general, a higher capacity reserve is required to satisfy a future uncertainty load than to serve a known load, at a specified level of reliability. Load forecast considerations are also important in composite generation and transmission system reliability studies, and their associated probability distributions. This paper examines the effects of load forecast uncertainty in bulk system reliability assessment incorporating changes in system composition, topology, load curtailment policies and bus load correlation levels.     

双侧开放市场中能量与备用容量的联合优化

为缓解系统中有限装机容量与一定的备用容量要求之间的矛盾,根据电力用户可以采取积极措施主动进行负荷管理而为系统提供备用容量的思想,提出一种基于最优潮流的能量和备用容量市场联合优化模型;研究在双侧开放的电力市场环境中,用户主动参与备用容量服务对市场运营效益的影响。IEEE 30节点系统算例表明,用户进入旋转备用容量市场,成为系统备用容量的新供应者,可使全系统的运营效益有较大提高,减少了系统备用容量购买支出,降低了各节点上的电价水平和系统备用价格。     

Distribution Feeder Scheduling Considering Variable Load Profile and Outage Costs

In a deregulated power market, customers would have more choices for their power service and the improvement of service quality has become a challenge to power transmission and distribution companies. Distribution system reliability that was traditionally considered within the planning activities is now incorporated in the operational environment. This paper presents study results of a multiobjective feeder operation optimization problem that considers how to balance network efficiency, switching and reliability costs in a distribution network. The proposed method divides annual feeder load curve into multiperiods of load levels and optimizes the feeder configurations for different load levels in annual operation planning. Customer load profiles and seasonal varying data of feeder section failure rates and customer interruption costs are considered. Numerical simulations demonstrate the time-varying effects on the optimal distribution feeder configuration and operation costs. A binary particle swarm optimization (BPSO) search is adopted to determine the feeder switching schedule. Test results indicate that not considering time-varying effects and using only simplified fixed load and reliability parameters could underestimate the total loss to the utility and its customers.     

Composite power systems reliability evaluation based on demand-side reserve

This paper proposes new demand-side reliability indices and useful computational methods for reliability evaluation of composite power systems. These new indices are based on the active power which can reach each demand spot under generating and transmission network constraints. This conception is defined as “reachable power,” and it leads the reserve margin on each demand spot, which is called as “demand-side reserve.” If the reachable power is insufficient to satisfy the demand, load curtailment is required. In the proposed approach, the conception of the load curtailment area is defined, and the estimate method of load curtailment area is indicated. In case the reachable power exceeds the demand, system reliability is evaluated by the demand-side reserve, and the power system is divided into several reliability zones according to the demand-side reserve levels. Small system examples are used to illustrate principles of the proposed approach, and middle system examples show the effectiveness and practicality.     

计及输电线路约束的华东电网备用容量可靠性评估

电力系统必须具有一定的备用容量来满足非计划的负荷需求,由于输电线路的约束、备用容量的数量及分布是否合理,关系到系统运行的安全性和经济性。通过建立计及输电线路约束的电力系统备用容量模型,采用蒙特卡罗重要抽样法对系统备用容量进行短期可靠性评估,给出相应的可靠性概率指标,并针对华东电网的实际运行数据进行分析,为华东电网备用容量管理办法的制定提供参考和依据。     

可中断负荷参与备用市场下的可靠性风险电价计算模型

可中断负荷(interruptible load,IL)作为用户参与电力市场的一种方式,最直接的影响是为供电公司提供另外一种可供选择的备用资源,在这种环境下,供电可靠性成本的内容也发生了变化,相应的可靠性电价计算模型也应有所调整。首先给出可中断负荷参与备用市场下可靠性电价定价流程,在此基础上量化了IL由于减少系统备用风险购电成本和电网投资改造风险成本而产生的经济效益,最后根据我国国情给出了可靠性电价的定价模型。算例分析表明,可中断负荷参与备用市场可为供电公司节约大量的可靠性投资成本,使其规避高购电电价和高投资的市场风险,进而降低用户支付的可靠性电价。     

基于可再生能源不确定性的电力系统双侧备用容量优化

在全球能源互联网背景下,以风电为代表的新能源入网给电力系统安全稳定运行带来新的挑战,同时也对备用容量配置提出了更高的要求,为此提出以双侧备用成本期望最小为目标函数的备用容量优化模型。在考虑需求侧响应中的可中断负荷,以及风速预测偏差和负荷预测偏差等不确定性因素的基础上,建立了满足经济性和可靠性要求的备用容量配置原则。并基于蒙特卡罗随机模拟的遗传算法对改进10机测试系统进行了求解,经过算例求解得到考虑需求侧响应的备用容量优化决策的经济性更好。与以往传统的备用容量配置相比,双侧备用容量配置能够在系统整体内实现资源的优化分配,同时也可以提高风电消纳能力,实现电力系统安全性和经济性最优。     

DG allocation with application of dynamic programming for loss reduction and reliability improvement

Distribution system companies intend to supply electricity to its customers in an economical and reliable manner whereas customers in most distribution system are outspread and connect to distribution system with different type of equipments. These equipment usually have various types and resistance together, that produce highest loss and lowest reliability for distribution systems and customers that are not appreciated in networks. Distributed generations (DGs) are one of the best reliable solutions for these problems if they are allocated appropriately in the distribution system. This paper presents multi-objective function to determine the optimal locations to place DGs in distribution system to minimize power loss of the system and enhance reliability improvement and voltage profile. Time varying load is applied in this optimization to reach pragmatic results meanwhile all of the study and their requirement are based on cost/benefit forms. Finally to solve this multi-objective problem a novel approach based on dynamic programming is used. The proposed methodology is successfully applied to a study case and simulation results are reported to verify the proposed approach.     

Quasi-Newton method for optimal load-flow solution under emergency mode of operation

Power systems in developing countries periodically experience a shortage of reserve capacity and imbalance between generation, transmission and distribution facilities. This results in the emergency operation of power systems. The solution of load flows under emergency operating conditions is used to decide on appropriate control action so as to prevent the spread of an emergency or to bring the system back to a normal state. This paper presents a method for optimal load-flow solution under the emergency mode of operation. The load flow is viewed as an optimization problem in which ‘inconvenience’ experienced by customers, owing to variation in supply voltage and load curtailment, is minimized subject to the network constraints and operational limits of the system. The problem is decomposed into two sub-problem is decomposed into two sub-problems exploiting the P-Q decoupling technique. An algorithm is given for the minimization of the sub-problems. The solution of the problem is based on recurring factorization of the Hessian matrices. For large systems the time required to compute the Hessian matrices is considerable. It is shown that the time can be reduced by approximating the Hessian matrices using a quasi-Newton method. Two versions of updating the Hessian matrix are given and their comparative advantages are discussed. The method is illustrated using the IEEE 14 bus and 30 bus test systems. Improvements in the method have been suggested and test results are presented.     

A comprehensive strategy for transmission switching action in simultaneous clearing of energy and spinning reserve markets

There is a great resolution calling for smart grids in recent years. Introduction of new technologies, that make the network flexible and controllable, is a main part of smart grid concept and a key factor to its success. Transmission network as a part of system network has drawn less attention. Transmission switching as a new transmission service can release us from load shedding and remove the constraints’ violations.Transmission switching can provide economic benefits compared to other control methods such as generation unit rescheduling or load shedding for contingency management.Utilizing a stochastic mix-integer nonlinear programming (SMINLP) model, transmission switching is used during contingencies and steady state to determine optimal required energy and reserve values.Stochastic joint energy and reserve markets with transmission switching considering dynamic constraints has been proposed to minimize the cost of supplying load, security expenses.Considering dynamic constraints in proposed model avoid the occurrence of transient instability when opening the line in transmission switching action.A network reduction method based on modified Jacobean AC Newton–Raphson technique power flow considering switchable line in technique is used for speeding up the calculation, efficiency and simplicity.To investigate the efficiency of the proposed strategy IEEE 14 bus test and IEEE 57 bus test system are studied. According to the obtained results, this strategy decreases energy and reserve marginal prices, as well as security cost.     

适用高压大容量领域的MMC-UPFC应用可靠性分析

统一潮流控制器(UPFC)是一种高度可控的灵活交流输电装置。针对适用于高压大容量输电领域的双回基于模块化多电平换流器(MMC)的UPFC(简称MMC-UPFC),考虑其备用结构和运行保护原则,并将站外交流系统转化为MMC-UPFC子系统,以传统九状态UPFC可靠性模型为基础,建立改进的双回MMCUPFC七状态可靠性模型。建立MMC-UPFC的节点注入功率模型,并基于该模型将含UPFC的最优负荷削减模型应用到合肥南部电网实例中,验证了MMC-UPFC各运行状态对系统可靠性的改善能力,并进一步研究了MMC-UPFC安装位置对可靠性改善能力的影响。     

可靠性与经济性协调的输电线路最大利用率评估方法

电网运行由于受各种因素制约,若仅以可靠性作为判据进行评估,则输电线路最大利用率处于较低水平。针对这一问题,通过对年持续负荷曲线的分析,提出一种基于经济性与可靠性协调的输电线路最大利用率评估方法,通过协调电力系统可靠性与经济性,得出现有线路年平均利用率真正能够达到的最高水平。评估中首先计算系统满足可靠性约束的年最大负荷,进而对持续负荷曲线超过年最大负荷部分作为过负荷切除,并按照可中断负荷方式给予切负荷赔偿;对于年持续负荷曲线中保留部分,针对其电量不足期望值给予停电损失赔偿。二者共同组成可靠性的经济代价,将其增长速度与电网售电带来的经济效益增速比较,只要可靠性的经济代价增速更慢,评估中系统最大年利用率就仍有提升空间。将该方法应用于IEEE RTS79系统,结果表明此评估方法较传统安全评估结果更高,能够进一步开发线路利用空间,充分利用输电线路的可用容量。     

Component criticality importance measures for the power industry

New reliability importance measures have been developed for the power industry to be applied for Electricity Transmission Systems (ETS). Reliability criticality measures are useful metrics to rank components regarding their impact on system performance. Criticality measures serve as useful tools to prioritize reliability improvement activities, identify weak-links in the system and many other uses. These proposed measures pertain to the outage rate of the system and component instead of the probability of failure or survival for a defined mission time. Outage rate is the best suited and appropriate output variable to evaluate the importance of the components in the electricity distribution system. The ETS is the component of the bulk transmission system to provide electricity to large municipalities, large industrial customers and the retail distribution system. The ETS is composed mainly of components such as lines, transformers, breakers and buses. All these components are interconnected with the aim of transporting electrical energy from the bulk transmission system to various load points. The new criticality measures are demonstrated on some commonly used electrical configurations, such as, breaker-and-a-half, breaker-and-a-third and the Dual Element Spot Network (DESN) for ETS.     

计及开关和母线故障的配电系统可靠性评估

在中低压配电系统中，负荷点和系统的可靠性除了与线路的故障有关外，还与系统中各种开关、母线等元件的故障有关。文中给出了考虑开关和母线故障的配电系统可靠性评估程序的设计思路。采用故障模式及其后果分析方法（FMEA），对网络结构进行故障后果区域划分，找出与负荷点停电模式相关的不同元件集合，从而计算了负荷点的可靠性指标和系统的可靠性指标。该程序还采用了递归函数使能很方便地识别辐射型配电系统结构。通过对IEEE6母线可靠性测试系统（RBTS）及实际系统的可靠性计算，结果验证了该程序的准确性和实用性。     

Marginal cost of transmission system adequacy for spot pricing

A model of marginal adequacy costs is developed in order to reflect the influence that any nodal load has on system static security. An adequacy cost function is defined, making use of the load that must be theoretically withdrawn at each node in order to re-establish power flows on transmission elements, after any static contingency of a predefined set occurs. A minimal adequacy transport system is defined as a primary system used as reference for adequacy calculation purposes. Inclusion of adequacy cost function leads to co-ordination equations, which permit identification of marginal costs that are suitable for partial transmission equipment investment recovery. Results of simulations on the reliability test system (RTS) show important costs' components, which are variable in time and space, thus being appropriate for spot pricing schemes. It is verified that a significant part of transmission investment can be recovered by means of the marginal costs of adequacy.     

区域电力系统最优备用容量模型与算法

建立实现备用容量最小的区域互联电力系统最优备用容量数学模型,推算多区域互联电力系统的联络线功率增量方程,以及区域互联电力系统频率偏差与区域备用容量的关系表达式。针对问题的具体特点,运用自适应免疫遗传算法对该模型进行求解,充分考虑频率偏差、负荷的随机波动以及区域互联系统运行的各种可靠安全约束,分别对独立的电力系统以及通过交直流联络线互联组成的区域电力系统进行仿真计算,可得到一天中24个时段的弹性备用容量。独立电力系统的算例表明：随着电力系统规模的扩大以及装机容量的逐步增大,最优备用容量占最大负荷的比例会逐步减小,可以减小0.395%~9.366%。对区域互联系统的算例表明：当区域系统互联时可以在一定程度上减小区域系统的备用容量,互联区域系统比各个独立系统的备用容量要减少1.036%~1.858%,节约了互联区域电力系统的成本,在一定程度上提高了区域互联系统运行的经济性。实例计算结果验证了所提模型的合理性、所提方法的可行性。     

在输电服务价格设计中计入可靠性分量

文中提出在输电服务定价中计入系统可靠性分量的方法,该方法包括3个项工作:①确定单位可靠性价值;②量化各类用户对输电系统可靠性的影响;③把可靠性分量整合到费率设计中。采用文中提出的方法,按照网内负荷、过网和发电等各类用户对系统可靠性的影响计算其应付费用或应得补贴。可靠性分量通过价格信号迫使系统中所有参与者(电力公司和用户)分担它们对系统可靠性的责任,并送出一个激励信息以鼓励新发电机的正确选址。该方法也反映了输电公司的长期投资回收需要。并用加拿大BCTC公司的实际例子解释了所提方法的计算步骤。     

A multi-year transmission planning under a deregulated market

Due to the deregulation of power industry, the transmission expansion plan is different from the process done by the integrated monopolies. In a monopoly electric market, the transmission expansion plan is carried out by the vertically integrated utility. The power company integrates its generations’ exploiting plans and its transmission expansion plans to maintain the system reliability. While in a deregulated power industry, generation, transmission, and distribution companies belong to different owners. The problem becomes more difficult. Generators experiencing transmission constraints can be expected to lobby for new transmission facilities that might relieve their constraints, while generators closer the load centers will likely toward not to build any new transmission facilities that would increase their competition. In order to provide a fair environment for all market participants, this paper proposed a reasonable expansion plan taking the operation cost, load curtailment cost, and investment cost into account. Due to the complexity of this model, the algorithm that combines the genetic algorithm with the linear programming method (GA-LP) is used to solve this problem. The 6-bus system and 24-bus IEEE reliability test system are used to verify the proposed model, and comparisons of test results between the proposed model and the traditional model are also demonstrated in this paper.