Practical issues in load modeling for voltage stability studies

Load modeling has become a critical component for the comprehensive and accurate analysis of power systems. In particular, voltage stability limits derived from simulations may be highly influenced by load models used in both static and dynamic analysis. While data for most transmission and generation elements is either well established or can be readily determined from measurement, good load data and models remain difficult to reliably ascertain. This paper discusses the requirements of load models, current approaches, and provides a practical approach to develop models for use in voltage stability analysis. Based on billing data or load inventory surveys, the load is classified into broad types such as residential, industrial, and commercial load and each is subdivided into more specific components including induction motors and other elements. Time-domain simulations are used to establish the load characteristics and general purpose models are synthesized from the results for use in static analysis. Examples of this approach are presented in case studies.