A study on transformer loading in Manitoba-peak-load ambient temperature

It is shown that the hourly ambient temperature and load of a substation transformer in Manitoba, observed over the three-month winter or summer time window, are governed by the normal distribution, respectively, and they jointly follow the bivariate normal distribution. Based on this, a rigorous model for the peak-load ambient temperature (i.e., the ambient temperature at the time when the winter or summer peak-load of the transformer occurs) is developed. This makes it possible to accurately determine the peak load capability of the transformer if its historical hourly ambient temperature and load data are available.     

NEW APPROACH FOR PLANNING PRIMARY DISTRIBUTION NETWORKS

ABSTRACT

The paper presents a new and simple methodology for planning primary distribution networks. It enables distribution system planners to determine: optimum feeder routes, optimum wire sizes, optimum substation locations and optimum substation sizes. The objective is to achieve a reliable and efficient configuration to supply the given loads with an overall minimum investment.

A criterion is established to determine the best feeder routing directly from the topology or the served area and load locations. An accurate representation for feeder cost models is presented and an economic loading limits for each feeder type are introduced.

A sample planning study is presented to indicate that the proposed method is simple, fast, efficient, and hence, it can be very valuable for system planning engineers.     

Reliability of various industrial substations

Many utility and industrial substation configurations have been designed to interconnect energy sources and individual industrial load points. The design, protection schemes, and operating procedures of a substation configuration directly affect the reliability of the power supply to these load points. When an existing or planned substation configuration is unreliable, the question is: which substation configuration will be more reliable? Another question is: what reliability methodology will account for the protection schemes in place, the operating procedures and the common cause failures of utility supplies? This paper will discuss and present a reliability analysis of eight basic industrial substation configurations that are typically used inside process plants. The zone branch reliability methodology is used to calculate load point reliability indexes of each substation configuration. The reliability analysis includes open and short-circuit failure modes of circuit protective devices, operating practices and common cause failures of utility supplies. The significant impact of common cause utility supply failures on load point reliability levels will be presented and discussed in detail.     

基于模糊控制的区域电动汽车入网充放电调度策略

提出一种基于模糊控制的电动汽车入网(V2G)充放电调度策略。首先,提出V2G管理系统的整体结构,其主要由有序充电调度系统和V2G变流器控制系统组成,前者合理安排各充电桩的充放电功率,实现削峰填谷的辅助功能;后者响应上层调度下发的功率指令,控制实际充放电行为,提供稳定的电能变换和能量交换的接口。然后,在有序充电调度系统中综合当前配电网的负荷特点,对当前接入充电站的全部电动汽车进行调配,并采用模糊控制算法计算充放电功率并下发给各充电桩,改善区域电网的负荷特性,实现削峰填谷的辅助功能。最后,通过仿真实验证明所提有序充电调度系统在满足电动汽车充电需求的同时,能够充分地利用电动汽车负荷的灵活性;在实现对电网削峰填谷的同时,有效地避免了电网负荷低谷时段大量电动汽车充电引起新负荷尖峰的问题。     

考虑柔性电负荷和热负荷的综合能源系统容量优化配置

柔性负荷参与调度能够削峰填谷、优化负荷曲线,降低系统成本。考虑可平移负荷、可转移负荷和可削减负荷建立了电力柔性负荷模型;根据用户对温度感知的模糊性建立了热力柔性负荷模型;采用混合整数线性规划方法,以经济成本最小和一次能源消耗量最少为目标,对综合能源系统进行配置优化,得到各个设备的最佳容量和各时段出力。算例结果表明,通过调度柔性电负荷和灵活调整室内温度,可促进可再生能源消纳、优化电负荷和热负荷曲线,从而提高风机装机容量、降低燃气轮机容量和蓄热罐容量、提高系统经济性、降低一次能源消耗量、提高可再生能源渗透率。     

面向新能源消纳的调峰辅助服务市场研究综述

随着新能源电源并网规模的不断提升,电力系统调峰压力日益突出,难以满足新能源快速发展,如何完善和深化电力调峰辅助服务市场机制进而提升系统调节能力已成为亟待解决的问题。在此背景下,首先梳理了我国电力辅助服务市场发展历程及关键政策;接着选取5个典型地区,具体从电厂、用户、储能等方面对其调峰辅助服务市场政策及机制进行了归纳分类和对比分析;最后结合我国电力调峰辅助服务市场发展背景以及各地区调峰服务市场的发展实际,在构建新型电力系统的目标导向下,提出了4点建议,以期为新时期我国调峰辅助服务市场的建设提供研究方向,为高比例可再生能源的消纳提供新思路。     

调峰运行对汽轮机主要辅助设备的影响

大机组参与调峰运行，由于大幅度负荷变动，要承受剧烈的温度变化和交变应力，从而缩短使用寿命。参与调峰还要求机组在一些特殊工况下长时间运行，对机组的安全和经济运行带来不利的影响。根据机组调峰运行方式，分析调峰运行对汽轮机辅助设备的影响。     

630 MW超临界火电机组深度调峰适应性研究

提高煤电机组灵活性,是提高我国电力系统调节能力的现实选择,以一台630MW超临界机组为例,通过掺烧优质烟煤和调节烟气旁路控制脱硝系统入口烟温的方法对机组调峰能力进行试验,实现了32％额定负荷下的稳定运行,分析了调峰运行过程中燃烧器、水冷壁及脱硝系统在调峰负荷下的适应性.试验结果显示,在32％负荷下,炉膛燃烧稳定,四周水...     

用于削减工业园区用电功率峰值的蓄冷空调系统的动态建模和优化控制

蓄冷可以通过利用峰谷电价差,使空调系统更加经济,还可以作为一种间接蓄电措施,在峰电时段释放冷量,减少空调系统耗电,实现削减用电峰值功率的功能。对工业园区内需要24 h供冷的、包含基载的蓄冷空调系统的控制进行优化建模,在满足供冷及削峰需求条件下,以经济最优化为目标,分别针对非削峰日、2类削峰日提出相应的控制策略。并以工业园区某一水蓄冷空调系统的控制为例进行了算例分析,结果表明蓄冷空调在削峰时具有削峰幅度大、削峰时间长的优势。另外,当该日冷负荷需求越大时,2类削峰日对蓄冷空调系统运行费用的影响越大,此时可能需要增加削峰补贴电价。     

Application of expert system to power system restoration in local control center

A method of restoration in power systems is developed by using sensitivity analysis. Heuristic rules are used in the plan to restore the blackout area that is recognized by the network topology and on/off status of switches (circuit breakers, line switches). The rules are categorized as flow-control rules, energization rules and line switching rules. A set of network switching changes not only the network topology but also the state of power systems. The switching for alleviating overloads is determined by analyzing the line power variations using sensitivities with respect to line switching and load shedding. This paper deals with each feeder power in a substation as a unit power, so the sum of load shedding can be reduced by the methodology proposed in this study. The representation of the power system components has hierarchical data structures for the real time recognition of network topology.     

The application of artificial neural networks to substation load forecasting

The substation loading is highly correlated with the customers served. The substations in a distribution system can be categorized as residential, commercial and industrial. Each type has a different power consumption pattern. The substation loading will be varied according to the combination of the above three types of customers. In this paper, a supervisory functional artificial neural network (ANN) technique is applied to solve the load forecasting of three Taipower substations which serve the different customer types. The load forecasting accuracy is enhanced by considering the temperature effect on the substation load demand. With the converged ANN models derived by a training procedure, the temperature sensitivity of the substation load demand is easily obtained by the recall process. It is suggested that the substation load forecasting can be performed efficiently by the proposed method to support distribution operation effectively.     

智能变电站负荷自动分配技术

研究智能变电站负荷自动分配技术的主要措施、提出发展方案,对支撑智能电网发展具有重要意义。基于配电网无功优化和网络重构,建立了智能变电站负荷自动分配数学模型,选取基于导向搜索法的无功优化算法和基于虚拟流法的网络重构算法,实现了以有功网损最小为目标的负荷自动分配。充分考虑分布式电源接入后配电网结构和运行方式发生的变化,基于出力特性,采用场景分析法建立模型,优化智能变电站负荷自动分配算法,实现了根据分布式电源出力调整负荷分配量的智能变电站负荷分配系统方案。验证表明,该方案能够保证无功补偿装置正确投入退出、分段开关和联络开关正确开合,线路有功损耗下降,有效提高了电网分析和控制功能的速度和可靠性。     

An interactive distribution load forecasting methodology forminicomputer use based upon a Markov-type process

An efficient comprehensive methodology is described that allows interactive forecasting of distribution-substation load growth and load sharing, with application to the determination of an economically feasible timing schedule for adding substation capacity. A BASIC-language implementation illustrating some of its capabilities is discussed. Load growth is expressed by a Gompertz model using parameters evaluated from historical data; however, other load-growth models can be easily implemented. Load transfer, which can be set to begin at any percentage of the substation capacity, is accomplished stochastically in the algorithm by means of a quasi-Markov process. Default load transfer threshold, load transfer flags, and other parameters are under direct control of the user and can be set to conform to individual base-case and historical data. The implementation of this algorithm for minicomputer use as an interactive planning and instructional tool is discussed, and an example is presented     

江苏省2003年夏季气温对电力负荷的影响

针对夏季降温电力负荷的比例较大而造成大部分地区电力短缺的问题,分析了江苏省2003年夏季最大用电需求与最高温度、最低温度的关系,划分了影响电力负荷变化的温度敏感区,得出了敏感区内温度对负荷的影响结论。这一结论对于电力主管部门进行来年的负荷预测、合理制定电力调度计划,具有实际的参考价值。     

全网无功优化的变电站电压无功控制策略

九区图是以工作点是否位于最优控制区为启动控制判据的无功优化调控策略;五区图是一种基于动作效果预算,以操作优劣距离为判据,面向VQC装置的调控策略;针对五区图的边界盲区缺乏明确的动作判据的缺陷,提出了九区图五区图组合调控策略;对于全网的变电站,根据设定的最优限值曲线,按照九区图判断各变电站的无功调压设备的工作点区域及启动区的上下限,仅对有越限的变电站按照五区图进行VQC装置的调控,既可减少控制变量的频繁操作,又可保证全网电压的质量和全网潮流的最优分布。     

Load to voltage dependency tests at B.C. Hydro

This paper describes the methodology, design, and results of a measurement-based determination of the load to voltage dependencies (also described as load sensitivities to voltage change) for a B.C. Hydro substation selected for a distribution automation pilot project. The test methodology was based on using data from a “control” substation, which represented the “natural” variation of the load at the test substation. The measured data was processed using correlation and multi-regression analysis. The tests were performed on a customer base which is mainly residential with some commercial, and a common high penetration of resistive-load. Spring and summer sets of measurements were gathered, and different load to voltage sensitivities for different seasons and time of day were derived. The difference between the sensitivity of the load at the measurement site and at the customer terminals was determined by using a detailed operation model     

基于启动时间延迟的家庭负荷管理优化策略

针对家庭中典型温控负荷会给用户带来高峰负荷需求,提出了一种基于启动时间延迟的家庭负荷管理优化策略。首先,给出了一种智能家电负荷控制架构,以支撑负荷优化控制算法在智能家电中的应用;然后,建立了基于启动时间延迟的负荷优化控制模型,并提出了一种启发式的启动时间延迟调整算法,该算法能够在负荷高峰时刻对各个负荷的运行周期施加一个最优的相位延迟,达到均衡负荷的目标;最后,通过仿真实验对比了多种场景下的优化效果,验证了所提策略能够降低短时负荷高峰、减小峰谷差。     

Impacts of high penetration level of fully electric vehicles charging loads on the thermal ageing of power transformers

This paper develops a methodology to determine the impacts of high penetration level of fully electric vehicles (FEVs) charging loads on the thermal ageing of power distribution transformers. The method proposed in this paper is stochastically formulated by modelling the transformer life consumption due to FEVs charging loads as a function of ambient temperature, start time of FEVs charging, initial state-of-charge and charging modes. FEVs loads are modelled using the results from an analytical solution that predicts a cluster of FEVs chargers. A UK generic LV distribution network model and real load demand data are used to simulate FEVs’ impacts on the thermal ageing of LV power distribution transformers. Results show that the ambient temperature, FEVs penetration level, and start time of charging are the main factors that affect the transformer life expectancy. It was concluded that the smart charging scenario generally shows the best outcome from the loss of life reduction perspective. Meanwhile, public charging which shifts a large percentage of charging load to commercial and industrial areas can significantly alleviate the residential transformer loading thus has little impact on the loss of life of transformers. The proposed method in this paper can be easily applied to the determination of the optimum charging time as a function of existing loads, and ambient temperature.     

采用二级热网电锅炉调峰的消纳弃风机理及经济性分析

针对中国西北、华北、东北(简称"三北")地区冬季供暖期弃风现象日益严重的问题,在研究电负荷特性、热负荷特性与风电场出力特性相关性基础上,结合电网调峰、热网调峰特点,提出二级热网配置电锅炉进行日调峰的消纳弃风方案。分析了方案的消纳弃风机理,研究了调峰电锅炉的启停控制策略,构建了基于二级热网电锅炉调峰的电热联合系统优化调度模型,并分析了方案的经济性。研究表明,该方案能在降低热电机组热负荷峰值、"以热定电"必发电功率的同时增加电网负荷谷值,从而为风电上网留出更大空间,提升风电消纳率,且能为整个电热联合系统带来经济收益。     

Dynamic data system modelling of electrical power demand

Time-series models are fitted to electrical load demand and ambient temperature using the dynamic data system methodology to identify the dynamic features of demand and temperature and to evaluate the impact of temperature dynamics on load demand. The models are used to forecast demand and the results agree closely with the actual data.