The authors recommend standard load models for power flow and dynamic simulation programs. The goal of this paper is to promote better load modeling and advanced load modeling, and to facilitate data exchange among users of various production-grade simulation programs. Flexibility of modeling is an important consideration. For transient stability, longer-term dynamics, and small-disturbance stability programs, the authors recommend the structure of multiple load types connected to a load bus. Load types are static including discharge lighting, induction motors, synchronous motors, and transformer saturation. For each load type, multiple models may be connected to the bus. For longer-term dynamics programs, a model for LTC transformers is also recommended.

Standard load models for power flow and dynamic performance simulation

The paper reviews literature which addresses the application of Flexible AC Transmission System (FACTS) concepts to the improvement of Power System utilisation and performance. It summarises literature on using high speed thyristor based control of HVAC power system elements to enhance the power carrying capacity of existing transmission circuits without compromising reliability. It describes a study system representative of existing power systems that has been developed to evaluate the economic and technical issues of loading transmission lines to their thermal limits. Considered are two scenarios, a multi-line corridor and a long radial interconnection, where the issues addressed are transient and dynamic stability, power flow control, reactive support and voltage stability. A benchmark system is developed to validate performance of die more simple devices. It is concluded that FACTS devices have the potential to significantly increase system stability margins thereby increasing loading capabil...

Flexible AC transmission systems (FACTS)

The accuracy of the load model has great effects on power system stability analysis and control. Based on our practice in China on modeling load from field measurements, this paper systematically develops a measurement-based composite load model. Principles guiding the load modeling practice are discussed based on detailed analysis on stochastic characteristics of the modeling procedure. The structure of the measurement-based composite load model is presented. A multicurve identification technique is described to derive parameters. The generalization capability of this built load model is also investigated in this paper. Two cases are studied to illustrate the accuracy of the developed load model on describing the load dynamic characteristics in the actual power system.

Composite load modeling via measurement approach

This paper presents the experimental determination of the ZIP coefficients model to represent (static) modern loads under varying voltage conditions. ZIP are the coefficients of a load model comprised of constant impedance $Z$ , constant current $I$ , and constant power $P$ loads. A ZIP coefficient load model is used to represent power consumed by a load as a function of voltage. A series of surveys was performed on typical residential, commercial, and industrial customers in New York City. Household appliances and industrial equipment found in the different locations were tested in the laboratory by varying the voltage from 1.1-p.u. voltage to 0 and back to 1.1 pu in steps of 3 V to obtain the individual $P$ – $V$ , $Q$ – $V$ , and $I $ – $V$ characteristics. Customer load tables were built using seasonal factors and duty cycles to form weighted contributions for each device in every customer class. The loads found in several residential classes were assembled and tested in the lab. It was found that modern appliances behave quite differently than older appliances even from only 10 years back. Models of the different customer classes were validated against actual recordings of load variations under voltage reduction.

Experimental Determination of the ZIP Coefficients for Modern Residential, Commercial, and Industrial Loads

Load modeling has significant impact on power system studies. This paper presents a review on load modeling and identification techniques. Load models can be classified into two broad categories: 1) static and 2) dynamic models, while there are two types of approaches to identify model parameters: 1) measurement-based and 2) component-based. Load modeling has received more attention in recent years because of the renewable integration, demand-side management, and smart metering devices. However, the commonly used load models are outdated, and cannot represent emerging loads. There is a need to systematically review existing load modeling techniques and suggest future research directions to meet the increasing interests from industry and academia. In this paper, we provide a thorough survey on the academic research progress and industry practices, and highlight existing issues and new trends in load modeling.

Load Modeling—A Review

A novel method is presented for preparing load models for power flow and stability studies. The LOADSYN load model synthesis software package transforms data on load class mix, composition, and characteristics into the form required for commonly used flow and transient stability simulation programs. Typical default data have been developed for load composition and characteristics. The load-modeling techniques used in this software and results of initial testing are described. Significant improvements in simulation accuracy are demonstrated. >

Load modeling for power flow and transient stability computer studies

The use of power system stabilizers (PSS) to damp power system swing mode oscillations is of practical importance. The design of PSS is taught in graduate level courses on power system dynamics and control, and has been the topic of numerous M.S. and Ph.D. theses. This paper discusses the experience in assigning PSS projects in an undergraduate control design course to provide students with a challenging design problem using three different techniques and to expose them to power system engineering. The details of the PSS design projects using root-locus, frequency-domain, and state-space methods are provided.

Power system stabilizers as undergraduate control design projects

By transforming utility load-mix data for use in standard load flow and transient stability programs the LOADSYN software makes it easy for power system analysts to produce new, more-accurate load models for system simulations. Better models can better predict power system behavior and thus improvements in transmission system utilization and planning.

Load modeling for power flow and transient stability computer studies: Volume 1, Summary report: Final report

By transforming utility load-mix data for use in standard load flow and transient stability programs, the LOADSYN software makes it easy for power system analysts to produce new, more accurate load models for system simulations. Better models can better predict power system behavior and thus bring improvements in transmission system utilization and planning. This volume is intended to assist power system analysts in the process of developing and using load models for power flow and transient stability studies. It covers load modeling philosophy, data sources, and the models and methods developed in this project.

Load modeling for power flow and transient stability computer studies: Volume 2, Load-modeling reference manual: Final report

This report presents a summary of the development of the Load Model Synthesis (LOADSYN) computer software, which transforms data on load class mix, composition, and characteristics into the form required for commonly-used power flow and transient stability simulation programs, including the EPRI (RP1208), Philadelphia Electric, and Power Technologies, Inc. (PSS/E) programs. The load modeling software is designed for ease of use by electric utility engineers, with default data provided for load composition and characteristics. This volume describes the internal structure and variables of the Load Model Synthesis programs, including the detailed requirements specification and instructions for interfacing with additional power flow and stability programs.

A. Murdoch

Papers

Load modeling for power flow and transient stability computer studies

Power system stabilizers as undergraduate control design projects

Load modeling for power flow and transient stability computer studies: Volume 1, Summary report: Final report

Load modeling for power flow and transient stability computer studies: Volume 2, Load-modeling reference manual: Final report

Load modeling for power flow and transient stability computer studies: Volume 4, LOADSYN code program reference manual