New Ancillary Service Market for ERCOT

Abstract

Ancillary services (AS) are the services necessary to support the transmission of electric power from generators to consumers given the obligations of control areas and transmitting utilities within those control areas to maintain reliable operations of the interconnected transmission system. As a result of the increasing penetration of renewable resources, the new reliability needs are emerging so that the changes made to the AS market become necessary. This paper presents a new AS framework being implemented at the Electric Reliability Council of Texas (ERCOT) in order to address the primary frequency control issues associated with the declining system inertia. This new design can balance the need for both reliability and economics while opening up the AS market to the traditional and non-traditional resources, including load resources with under-frequency relays and energy-limited resources like batteries. This paper also introduces a new way to quantify the benefits of the new AS design using ERCOT model and data.

Keywords

• Ancillary service
• primary frequency control
• system inertia
• load resources with under-frequency relays
• energy-limited resources
• battery