Daily Load Shape Research Articles

A demand side response scheme for enhancing power system security in the presence of wind power

One of the major concerns associated with the wind power integration is its anti-peaking characteristic which increases the required ramping of the conventional generators and potentially threatens power system security. Recently, demand side response has become one of the likely successful solutions that can be employed in overcoming the negative impact of the anti-peaking characteristic of the daily net load curve. This paper presents a demand side response framework in which the load shifting strategy is effectively applied to improve the daily load profile of the system in the presence of wind power. The size of the load to be shifted is determined such that the system security in terms of voltage magnitudes and voltage stability margins is preserved for the normal state and prospective emergency states. To stimulate the demand side response candidates to shift their load and support the utilities to realize a particular daily load shape, an incentive reimbursement pattern based on the participants’ submitted sizes has been proposed. The mathematical formulation of the problem is stated as a nonlinear mixed integer programming problem. The problem is solved using Benders decomposition technique where the intact problem is split into a master problem and several smaller nonlinear problems solved individually by the conventional methods. The performance of proposed approach has been evaluated by its application on the IEEE 57- and 118-bus systems.

Segmentation analysis of residential water-electricity demand for customized demand-side management programs

With increasing water and energy use in the residential sector, due to population growth, urbanization, and climate change, demand-side management (DSM) is essential to complement supply-side interventions to meet future demands and reduce costs. This paper explores how customer segmentation analysis can support customized water and electricity DSM. We contribute a three-phase customer segmentation analysis of over 1000 residential accounts in the Los Angeles County (Southern California) to explore the heterogeneity of residential water-electricity demand profiles and provide insights for coordinated water-energy DSM. Results show that, on the one hand, daily water and electricity consumption are correlated, thus groups of high consumers can be targeted with coordinated water-electricity DSM interventions. On the other hand, the absence of a relevant causal nexus between water and electricity daily load shapes suggests that DSM actions for water should be differentiated from those for electricity. Finally, both objective (e.g., presence of swimming pool) and subjective psychographic features (e.g., conservation attitude) are found to be relevant potential drivers of water-electricity demands. Based on these findings, we propose recommendations for designing a portfolio of mixed customized water-electricity DSM interventions to foster conservation or peak shifting objectives.

Correction of load curves estimated by electrical appliances ownership surveys using mass memory meters

Through the PPHs (Energy Audit on Ownership and Usage of Electrical Appliances), one has a rough idea of the daily load shape curves by appliance. However, the curves obtained this way tend to be a little inaccurate, as they are generated by the consumer survey information of usage of the equipments, which tend to be imprecise information. Despite its inaccuracy, the energy audits (PPHs) are a simple and cheap way to understand equipment ownership and consumption habits of the residential consumers of such a large country as Brazil. In this work, it presented a statistical-based model that allows a better calibration of the load shape curve for appliances for residential consumers using information from two sources: PPHs and household measurements through specific devices that provide real-time measures of the total consumption. Two methodologies using linear regression were tested, one considering a two parameter linear model and another one considering only the slope parameter. It is shown that the latter produced better results.

Harmonic Impact of Plug-In Hybrid Electric Vehicle on Electric Distribution System

This paper presents the harmonic effects of plug-in hybrid electric vehicles (PHEV) on the IEEE 37-bus distribution system at different PHEV penetration levels considering a practical daily residential load shape. The PHEV is modeled as a current harmonic source by using the Open-Source Distribution System Simulator (OpenDSS) and DSSimpc software. Time series harmonic simulation was conducted to investigate the harmonic impact of PHEV on the system by using harmonic data obtained from a real electric vehicle. Harmonic effects on the system voltage profile and circuit power losses are also investigated by using OpenDSS and MATLAB software. Current/voltage total harmonic distortion (THD) produced from the large scale of PHEV is investigated. Test results show that the voltage and current THDs are increased up to 9.5% and 50%, respectively, due to high PHEV penetrations and these THD values are significantly larger than the limits prescribed by the IEEE standards.

The impact of a cold snap on daily system load shapes

During the last decade, the city of Austin has witnessed two important cold snaps, one of which has brought the system load very close to peaking during otherwise average winter months. We examine the effect of a cold snap on load curves. To do so, we have estimated a time-series hourly load model allowing for both time-dependent and weather-dependent activities, and for serial correlation. We find three significant results. First, there is a significant first-order serial correlation, and this autoregressive process must be accounted for. Otherwise strong doubts are cast upon results based on models which do not. Second, not only is the system-load consumption significantly affected by unusual and extreme weather conditions, but there is also marked difference between load curves for an average and a peak winter day. Finally, the severity of the cold snap has a stronger influence on system load in both increasing average consumption levels and modifying the shape of the load curves than does the length of the cold snap itself. Given the important impact of changes in outside temperature on system load in general and the (sometimes heated) debates surrounding the construction of new generating and distributing facilities, these findings should be of general interest.

An expert system based algorithm for short term load forecast

Existing studies on 1-24 hr load forecasting algorithms are reviewed, and an expert-system-based algorithm is presented as an alternative. The logical and syntactical relationships between weather and load as well as the prevailing daily load shapes have been examined to develop the rules for this approach. Two separate, but similar, algorithms have been developed to provide 1-6 hr and 24 hr forecasts. These forecasts have been compared with observed hourly load data for a Virginia electric utility for all seasons of the year. The 1 hr and 6 hr forecast errors (absolute average) ranged from 0.869% to 1.218% and from 2.437% to 3.48% respectively. The 24 hour forecast errors (absolute average) ranged from 2.429% to 3.300%. >

Impacts of New Entry and Horizontal Joint Ventures on Industrial Rates of Return

Data Resources, Inc., Regional Load-Curve Models, vols. 1 and 3 (Aug., Sept. 1981). Engle, Robert, Clive W. J. Granger, Allen Mitchem, and Ramu Ramanathan, Some Problems in the Estimation of Daily Load Shapes and Peaks, Modelling and Analysis ofElectricity Demand by Time-of-Day, Electric Power Research Institute (EPRI), EA-1304, Dec. 1979. Engle, Robert F., Clive W. J. Granger, and Ramu Ramanathan, Regional Load Curs e Models: QUERJ's Model Long Run Forecasts and Sensitidvity Analysis, EPRI, EA-1672, vol. 4 (Sept. 1981). Granger, Clive W. J., Robert F. Engle, Ramu Ramanathan, and Allan Andersen, Residential Load Curves and Time-of-Day Pricing: An Econometric Analysis,' Journal ofEconometrics 9 (1979), 13-32. Granger, Clive W. J., et al., A Regional Load Curve Model: Specification and Estimation, Electric Power Research Institute, forthcoming. Graybill, Franklin, Theory and Application of the Linear Model (North Scituate, MA: Duxbury Press, 1976). Hanushek, Eric A., Efficient Estimators for Regressing Regression Coefficients, The American Statistician 28 (May 1974), 66-67. Mitchem, Allen, A Regional Model of Time of Day Elasticity Demand: A Tiuo Stage Approach, unpublished PhD dissertation, University of California at San Diego, 1981. Poirier, Dale, Economic Issues in Land Forecasting, Modelling and Analysis of Electricity Demand by Time-oJ-Day, EPRI, EA-1304, Dec. 1979. Ramanathan, Ramu, Robert F. Engle, and Clive W. J. Granger, Regional Load Curlve Models: QUERJ's Model Long Run Forecasts and Sensitivity Analysis, EPRI, EA-1672, vol. 2 (Aug. 1981). University of Arizona Engineering Experiment Station, Modelling and Analysis of Electricity Demand by Time-of-Day, EPRI, EA-1304, Dec. 1979 (proceedings of the EPRI workshop at San Diego). U.S. Department of Commerce, Notes on TemperatureHumidity Index, L.S. 5922, June 1959.

American-Electric Power System Electric Thermal Storage Program: An Evaluation of the Impact on the Gereration System

The impact of the cperation of Electric Thermal Storage (ETS) equipment o a residential customr's daily load shape, based on test data, was estimated. The effect on the system's load shape was then determined, and an evaluation of econormic benefits resulting frcm this change performed, both from the standpoint of an individual ETS installation and a hypothetical expansion of installations. Incentives required to implement sach a program wre considered, and costs of such incentives compared with expected benefits. Finally, the rumber of ETS installations which the AEP System could accommodate was considered, to assess the feasibility of a potential ETS implementation program.

American Electric Power System Electric Thermal Storage Program: An Evaluation of the Impact on the Generation System

The impact of the cperation of Electric Thermal Storage (ETS) equipment o a residential customr's daily load shape, based on test data, was estimated. The effect on the system's load shape was then determined, and an evaluation of econormic benefits resulting frcm this change performed, both from the standpoint of an individual ETS installation and a hypothetical expansion of installations. Incentives required to implement sach a program wre considered, and costs of such incentives compared with expected benefits. Finally, the rumber of ETS installations which the AEP System could accommodate was considered, to assess the feasibility of a potential ETS implementation program.

Calculation of Energy Losses in a Distribution System

A new method for evaluating energy and capacity losses on a distribution feeder in a rigorous manner is presented. Typical daily load shapes are integrated with a load flow procedure to produce an energy model. The performance of a feeder is analyzed by a three-phase load flow program capable of modeling the different load component characteristics as well as imbalance in loading and system configuration. The system configuration can be any combination of single, two and three-phase circuits as required, up to the capacity of the program. The effects of neutral and ground return paths are included. The load flow program utilitizes a new approach to load modeling that recognizes the key load components and their voltage sensitive characteristics.