Grid Support Capacity Estimation of DERs using Spatiotemporally Downscaled Solar Irradiance

Accurately estimating the capacity of distributed energy resources (DERs) to provide grid support functions is critical for their effective integration into transmission-level grid operations. Traditional weather forecasting methods typically provide irradiance data over large spatial grids, neglecting localized variations essential for precise DER capacity estimation. This study addresses this limitation by employing spatiotemporally downscaled solar irradiance data, enabling the generation of realistic, time-varying PV output profiles for each residential unit within a 12-house feeder network. The capability of residential solar photovoltaic (PV) systems to offer voltage and frequency support through inverter-based droop control methods (Volt-Watt, Volt-VAR, and Freq-Watt) is evaluated. A 24-hour simulation was conducted to assess voltage deviations resulting from varying solar conditions, followed by the activation of Volt-Watt and Volt-VAR control functions to mitigate these deviations and ensure compliance with American National Standards Institute (ANSI) voltage standards. Due to complexities in translating PV outputs to frequency deviations in grid-following inverter setups, Freq-Watt control was only evaluated under constant solar conditions and not applied to the time-varying scenarios. Results demonstrate that integrating spatiotemporally downscaled solar irradiance significantly enhances the accuracy of DER capacity estimation and confirms the effectiveness of inverter-based droop controls in maintaining grid voltage stability.