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

CIGRE WG C4.605 : “Modelling and aggregation of loads in flexible power networks”

A dynamic model of the response of a single residential air conditioner load to weather conditions is developed. The model's performance is evaluated using data obtained from ten customers participating in the Athens Automation and Control Experiment, in Athens, Tennessee and some approaches to the determination of the parameters of a customer's thermal envelope model are discussed. The dynamic model is used for a preliminary assessment of the effect of the level of detail on model accuracy. For the limited number of customers with suitable data and survey information who were available in the experiment, the variability of parameters and responses is assessed. >

Residential air conditioner dynamic model for direct load control

Dynamic load modelling based on measurements in medium voltage distribution network

The authors deal with static load (SL) characteristics (P-V and Q-V characteristics) of a medium-voltage distribution network derived from field measurements. The experiments have been performed by changing the tap position of an on-load tap-changing transformer in different seasons, different week days and day periods. P-V and Q-V load characteristics are divided into two classes, transient and steady-state characteristics. The differences between them are discussed and quantified. Both classes are mathematically described by polynomial, linear and exponential SL models. Model parameters are obtained by curve fitting using a least square method. The adequacy of developed load models is critically assessed and discussed. All the static characteristics are grouped according to seasons and day periods and are mutually compared. Finally, the parameters of the SL models for residential load without electrical heating are suggested for different seasons.

Identification of static load characteristics based on measurements in medium-voltage distribution network

A new aggregation method for deteining load characteristics for representation in computer simulations is proposed. In support of the new method, a mathematical derivation is presented. Also, results are compared with models obtained by using the EPRI/University of Texas at Arlington method and field tests. The application of the proposed method is simpler than existing methods in that it does not require field tests or the use of curve fitting techniques. The procedure should be of primary interest to transmission system planners involved in load flow and dynamic stability simulations of power systems.

J. R. Ribeiro

Papers

A New Aggregation Method for Determining Composite Load Characteristics