Autonomous Demand Response for Primary Frequency Regulation

Demand response has long been an integral part of power system control and operation. Recently, demand response has received more interest as a potentially effective tool to help gain higher levels of asset utilization on the bulk power grid and to avoid or delay the need for new transmission-line construction.

Autonomous demand response is defined as load response to system-based signals rather than to master control signals or price signals from a central dispatch center. The most readily available system-based signal is frequency, which can be a very reliable indicator of grid instability, problems, or abnormal conditions. Speed governing systems at central generating stations, when operating in droop mode, employ frequency as the primary feedback signal. These governors are largely responsible for affecting primary frequency response of the bulk power grid thereby maintaining a continuous balance between supply and demand.

This research examines the use of autonomous demand response to provide primary frequency response in an interconnected grid. Ultimately, it is conceivable that all primary frequency response might be delivered by responsive load leaving dispatchable generation to be base loaded or ramped with
very slow ramp rates. If this objective were to be achieved, numerous benefits might be realized, including reduced emissions from fossil plants as a result of higher operating efficiencies and greater flexibility in integrating variable generation sources such as wind and solar. The work builds on previous studies in several key areas: it uses a large realistic model (i.e., the interconnection of the western United States and Canada); it establishes a set of metrics that can be used to assess the effectiveness of autonomous demand response; and it independently adjusts various parameters associated with using autonomous demand response to assess effectiveness and to examine possible threats or vulnerabilities associated with the technology. Where prior research has focused on showing the efficacy of the concept in delivering primary frequency response, this study’s primary objective was to identify any potential deleterious effects.