Ancillary Service Requirements Analysis with Increasing Solar Generation in the ERCOT Interconnection

The increment of solar generation in an electric system will introduce significant variations to its generation supply, compromising the reliability of the system. These variations need to be balanced by counter actions that are provided by other system elements which are procured by the independent system operator (ISO). These counter measures are known as ancillary services. The Electric Reliability Council of Texas (ERCOT) procures ancillary services in order to reduce the instantaneous mismatch between generation and demand. This allows to maintain the frequency and reliability of the electric system [1]. In the last few years, there has been an exponential increase in solar capacity in the ERCOT system, increasing the need for ancillary services. This has lead to the creation of a new methodology to determine ancillary service requirements in order to accommodate the new variables in reliability that renewable generation capacity brings. This paper presents the methodology and associated tool to calculate the ancillary services requirements when solar generation capacity is increased in the system. The methodology and its implementation guide ERCOT and the Public Utility of Texas (PUCT) when evaluating reliability requirements in solar capacity. This allows the creation of policy and protocols to maximize solar energy's economic and electric benefits [2].