T&D Interactions and Future-Grid Stability: Role of IBR-DER-Driven T&D Interactions in Future-Grid Stability

The power grid is rapidly evolving, leading to unplanned operating conditions where the distribution system is no longer a passive consumer of electric energy. Most of the bulk system stability analytics assume that the distribution system is a passive consumer of electricity, which needs to be reevaluated with the evolving power grid. Large-scale integration of inverter-based technology, like distributed generation (DG) and flexible loads [(collectively calleddistributed energy resources(DERs)], in the distribution system is leading to an increase in transmission and distribution (T&D) system interactions.T&D interactionscan be defined as the interdependence of system planning, performance, and operational decision making between T&D systems. T&D interactions impact several power grid aspects, including system stability, system planning, protection and controls, system resilience and reliability enhancement, etc. The California Independent System Operator (CAISO) has shed some light on the operational challenges observed in the real world and has highlighted the need to develop mechanisms to utilize T&D interactions for reliable grid operation (e.g., DER-based automatic generation control). For a stable future power grid, modeling, analyzing, and utilizing these T&D interactions effectively will be crucial. Aggregated models like the composite load models (CLMs) and other reduced order models (ROMs) can capture certain aggregated behavior of distribution system aspects, but they do not capture some features, like unbalanced nature and feeder voltage impacts on the distribution loads and DERs. T&D cosimulation can effectively capture the T&D interactions and their impact on power system stability.