多区域互联电力系统输电服务边际电价理论

建立了一个多区域全交流互联电力系统最优潮流模型 (M-OPF),发展了一种基于最优潮流的灵敏度分析方法,该方法可以提供在参数变化同时保持最优解情况下电力系统运行状况的变化信息。M-OPF问题求最优解时,通常有一部分不等式约束条件。在计及不等式约束条件的最优解邻近进行灵敏度分析来计算灵敏度系数。它们是通过产生一个Kuhn-Tucker条件的线性近似来求得的。文中提出用区域发电成本对母线需求及功率交换的灵敏度信息来计算边际转运价格。     

多区域电力联营体运行下的输电成本分配

在发电计划由电力联营体（Pool）集中调度的互联电力系统中，各区域负担的发电量及计划交换功率（SIP）水平是统一决定的。为了让联营体成员得到公平的成本回报及利益分配，有必要对不同的输电交易进行适当的输电运行成本分配。文中提出了将联营体内集中调度的计划交换功率水平分解成多个“一对一”的双边交易。双边交易的交易量及其相关的环流输电成本将用于成本回报和利益分配的计算。同时还提出了一种通过迭代多区域全交流最优潮流来解决成本分配问题的算法。最后通过一个算例来阐明该算法及其实现，并讨论系统参数如系统负荷及输电线容量变化所带来的影响。     

多区域互联电力系统的基于长期边际成本的输电定价

基于长期边际成本的输电定价是基于未来负荷和供给增长的预想峰值,寻求确定未来投资的当前值,该投资应能满足系统中不同位置负荷的边际增长。输电网的用户支付一笔与其在输电网中位置有关的费用给服务的提供者。在一个多区域互联的电力系统中,一个区域的长期边际转运成本为由于系统内2母线间单位交易量而导致该区域的投资成本增加量。提出了一个灵敏度分析的方法来计算各个区域之间的长期边际输电成本。     

运用连续二次规划法计算区域间极限传输容量

区域间功率交换的极限传输容量(TTC)是互联系统电力市场中的一个重要指标。文中运用连续二次规划法进行最优潮流计算,取得相应的TTC。其目标函数是在满足潮流方程和系统运行约束条件下寻求特定发电机群和负荷群之间的传输功率最大值。文中将无功功率作为OPF的控制变量,故节点电压也被优化以得到最大传输容量。采用最优潮流方法可以避免用连续潮流方法计算TTC而较为保守的缺点。给出了有关的数学模型和计算方法及流程。IEEE-30节点系统的计算结果表明了用该方法计算TTC的有效性和实用性。     

单边开放电力市场下最优差价合约

研究了单边开放电力市场下差价合约的最优形式。在只放开发电市场竞争的情况下,电力市场往往处于不稳定的状态,但是在供应函数模型分析的基础上,经研究发现电网公司通过与发电企业签订差价合约即可实现发电市场的均衡,使电力市场处于稳定的状态。但差价合约却需要满足极其严格的条件,即合约电价和合约电量比例的乘积在一定范围之内,该范围取决于发电企业成本和电力需求负荷。当发电企业为常数边际成本时,该乘积越大,电网公司购电成本越小;当发电企业为截距为零线性边际成本或线性边际成本时,该乘积越小,电网公司购电成本越小。因此在单边开放电力市场的情况下,电网公司设计差价合约交易机制时,应充分考虑发电企业成本和电力需求负荷的影响,以实现电网公司购电成本最优。     

风电场相变储能膨胀发电系统容量配置方法

为提高风储发电系统可持续运行能力,提出改进的风电场相变储能膨胀发电系统,对该系统的最优容量选取办法进行了研究。首先采用中值滤波法对特定风电场历史年风电功率数据进行分解,根据风电场实际出力平稳分量与调度水平之间的功率差值制定相变储能膨胀发电系统分频控制策略;然后利用非参数估计计算满足给定风电可调度性置信度水平的系统最优功率交换水平。定义储能系统可持续运行能力评价指标,并与考虑功率投资成本、能量投资成本和保障系统可持续运行投资成本的综合经济学评价函数进行折中,计算系统最优能量交换水平。最后,以配备蒸汽直冲式双螺杆膨胀发电系统的风电场为例进行说明。     

互联电网联网最优潮流模型及其算法

提出了考虑区域间传输断面交易功率约束的互联电网联网最优潮流模型及其算法。该模型中,以网损最小为目标函数,其约束条件中包含了系统的潮流约束、传输断面的有功功率约束以及系统各个变量的运行约束,由此不但可以满足区域断面之间的交易功率约束,而且能保证互联电网的优化运行。针对目前互联电网分层分区管理的特点,根据此最优潮流模型,采用母线撕裂法对互联电网进行切分,建立了相应的分解协调模型,并采用分解协调内点法求解,以进一步提高模型的求解效率。通过对4个测试算例的仿真分析,证明了文中所述模型及其算法的正确性及有效性。     

基于分布式电源模块化互联的多边交易电价机制设计

文章基于分布式发电模块化互联设计了多边交易电价机制,包括模块间供需电价机制和模块内交易电价机制。在模块间的电价机制中考虑电力阻塞费用,通过最优路径函数来优化电价公式,使电力交易收益最大;在模块内设计基于节点边际成本和发电成本因子的弹性电价,并在其中引入了弹性用电容量来衡量分布式能源(distributedenergy resources,DER)用户用电舒适度。在满足一定舒适度的前提下利用弹性电价提高DER用户的经济收益,并促使用户进行电力消纳和电力互济。最后,根据某地区的光照强度预测发电量,计算其交易费用,并与取消政策补贴后的光伏基准电价交易费用进行对比。结果表明所设计的弹性电价需要的费用明显低于光伏基准电价的总费用,可为分布式发电的电力市场规划提供可靠依据。     

基于等效网络的过网损耗计算实用化方法

在电力市场下,省级电网间的转运交易是一种重要的电能贸易形式.文中提出一种基于等效网络的过网损耗实用化计算方法.该方法将转运交易等效为提供转运服务的省网内的发电节点和负荷节点,将损耗计算的范围缩小至等效网络,利用潮流追踪法进行损耗分摊.其中,转运交易对等效发电机和等效负荷提供出力的份额,根据联络线功率对转运交易功率的灵敏度计算得出.对具有775母线的三个省级电网中的转运交易进行了过网损耗计算.结果表明,该方法简便、快捷,除潮流计算外无需过多的附加计算,具有实用意义.     

基于分布式电源模块化互联的多边交易电价机制设计EI北大核心CSCD

文章基于分布式发电模块化互联设计了多边交易电价机制,包括模块间供需电价机制和模块内交易电价机制。在模块间的电价机制中考虑电力阻塞费用,通过最优路径函数来优化电价公式,使电力交易收益最大;在模块内设计基于节点边际成本和发电成本因子的弹性电价,并在其中引入了弹性用电容量来衡量分布式能源(distributedenergy resources,DER)用户用电舒适度。在满足一定舒适度的前提下利用弹性电价提高DER用户的经济收益,并促使用户进行电力消纳和电力互济。最后,根据某地区的光照强度预测发电量,计算其交易费用,并与取消政策补贴后的光伏基准电价交易费用进行对比。结果表明所设计的弹性电价需要的费用明显低于光伏基准电价的总费用,可为分布式发电的电力市场规划提供可靠依据。     

Long-run marginal cost based pricing of interconnected system wheeling

Each utility in an interconnected system has an obligation to guarantee sufficient transmission capability to maintain an efficient, economical, reliable and secure system during peak scenarios. Security is an important consideration underlying network investment. The standards of service have a direct impact on investment burdens and therefore definition and consensus among participants in respect of security standards are necessary. Charging for transmission services, ensuring the investment levels and recovery of sunk capital are new problems now receiving attention in the context of electricity supply industry unbundling. In this paper a method for long run marginal cost (LRMC) based pricing in multi-area interconnected system, based on the incremental use of each area's transmission network at times of peak flow, is proposed. The LRMC of transmission capacity is based on long term costs of transmission investment requirements. The marginal wheeling costs, with security taking into account, are computed using the sensitivities of the MW-mile of each area with respect to the bus power demand. These sensitivities are calculated using a linear expansion of the Kuhn–Tucker conditions of the investment cost optimization problem. Contingency ranking method is used to speed up the computation.     

Evaluation of wheeling and nonutility generation (NUG) optionsusing optimal power flows

The application of optimal power flow for the evaluation of wheeling and nonutility generation (NUG) related options is presented. Both wheeling and NUG options affect vital attributes such as system security, voltage profile, losses, and VAr reserves. These options put a strain on the existing transmission system and may restrict economic utility dispatching. Optimal power flows may be used to determine the best control settings to accommodate wheeling or NUG options so as to maintain system security while minimizing losses or production cost. Short-term marginal wheeling costs may be derived using optimal power flows. Case studies involving the Northeast Utilities and IEEE test systems are presented. These cases show that optimal power flows can be used effectively to address a broad range of wheeling or NUG related planning issues     

Wheeling rates based on marginal-cost theory

Knowledge of what rates for wheeling electric power should be, if based on marginal costs, is vital in the debate on how wheeling should be priced. The authors present extensive computations of marginal costs. Sensitivities to losses, constraints, load levels, amount of power wheeled, revenue reconciliation, etc. are examined in the context of two case studies. Revenue reconciliation for capital recovery is described briefly     

Interchange costing and wheeling loss evaluation by means ofincrementals [electricity]

The authors consider the incremental pricing concepts and incremental loss concepts for use in real-time operations involving interchange evaluation and wheeling loss evaluation. They provide an overview of methods to evaluate the cost of electrical energy for purchases and sales using incrementals (i.e. derivatives of energy costs and energy losses). Since incrementals are directly available from economic dispatch, the methods are well suited for rapid on-line costing. The authors extend the incremental methods to calculate on-line losses associated with three-party or wheeling type transactions. The accuracy of the method of calculating wheeling losses is verified by a load flow comparison. The potential impacts to the production cost for such transactions are also evaluated using a large system model. Finally, it is pointed out that the overall production cost of the wheeling utility may increase or decrease, even though the wheeling losses are completely accounted for, due to the change in generation profile which results from adjustments in the economic dispatch     

Energy and reserve pricing in security and network-constrained electricity markets

This paper analyzes some unresolved pricing issues in security-constrained electricity markets subject to transmission flow limits. Although the notion of separate reserve types as proposed by FERC can be precisely and unambiguously defined, when transmission constraints are active, the very existence of separate reserve prices and markets is open to question when the prices are based on marginal costs. Instead, we submit here that the only products whose marginal costs can be separately and uniquely defined and calculated are those of energy and security at each node. Thus, under marginal pricing, at any given network bus all scheduled reserve types should be priced not at separate rates but at a common rate equal to the marginal cost of security at that bus. Furthermore, we argue that nodal or area reserves cannot be prespecified but must be obtained as by-products of the market-clearing process. Simulations back up these conclusions.     

电力市场下的无功电价研究

无功功率服务价格是电力工业重组中的一个重要的研究课题。由于传统的最优潮流数学模型不考虑无功功率的生产成本,因此无法得到合理的无功功率价格。文中在引入了无功功率的发电成本和无功补偿器的成本之后,运用最优潮流方法,分析了各种不同的优化目标及不同的约束条件对以经济学为基础的无功电价的影响及无功电价的特点。以一个实例系统对无功功率价格进行了研究,揭示了无功电价的一些基本规律,取得了有指导意义的成果。     

Reserve constrained multi-area economic dispatch employing differential evolution with time-varying mutation

For a power pool that involves several generation areas interconnected by tie-lines, the objective of economic dispatch (ED) is to determine the most economical generation dispatch strategy that could supply the area load demands without violating the tie-line capacity constraints. The objective of multi-area economic dispatch (MAED) is to determine the generation levels and the interchange power between areas which would minimize total fuel cost while satisfying power balance constraint, upper/lower generation limits, ramp rate limits, transmission constraints and other practical constraints. In reserve constrained MAED (RCMAED) problem inter-area reserve sharing can help in reducing the operational cost while ensuring that spinning reserve requirements in each area are satisfied. The tie-line limits too play a pivotal role in optimizing the cost of operation. The cost curves of modern generating units are discontinuous and non-convex which necessitates the use of powerful heuristic search based methods that are capable of locating global solutions effectively, with ease. This paper explores and compares the performance of various differential evolution (DE) strategies enhanced with time-varying mutation to solve the reserve constrained MAED (RCMAED) problem.The performance is tested on (i) two-area, four generating unit system, (ii) four area, 16-unit system and (iii) two-area, 40-unit system. The results are found to be superior compared to some recently published results.