A ToolSuite for Increasing Performance and Reliability of Combined Transmission-Distribution under High Solar Penetration

High penetration of solar photovoltaics (PV) in electric power grids has created a need for changes to power system planning and operations analysis. Important technical issues such as two-way power flow, coordination of protection devices, transmission-distribution interaction, and reduction in inertia need to be resolved to enable a greater deployment of solar generation. To overcome these technical barriers, this project will develop a suite of software tools that creates a holistic understanding of the steady-state and transient behavior of transmission-distribution networks’ interaction under high PV penetration levels, along with the capability of real-time monitoring of the distribution systems and integration of system protection.

Three software tools will be developed to help improve grid-reliability and performance of combined transmission-distribution systems with high solar penetration. First, a high-fidelity combined transmission-distribution steady-state analysis tool will perform quasi-static analysis with a time-step resolution of less than five seconds. Second, a simultaneous transmission and distribution system dynamic and protection system analysis tool will be implemented that includes new solar generator PV models based on dynamic phasors and electromagnetic transient principles. Third, a distribution system state estimation tool will be developed to provide near real-time updates of every four seconds. This tool will also handle uncertainty and non-stationary dynamic behavior.

This project will enable engineers to analyze different high PV penetration scenarios with several critical features: fast what-if scenario analyses, modeling of new inverter controls, simulation of large disturbances, protection coordination assessment, and analysis of steady-state and dynamic behavior, both at the transmission and distribution network level. The two proposed frameworks for planning and operation will improve grid performance and reliability by maintaining and enhancing the efficiency and reliability of electric transmission and distribution systems in a cost-effective and safe manner, which will enable hundreds of gigawatts of solar generation to be deployed onto the nation’s electric grid.