Grid supply point operations with TSO-DSO interaction: A comprehensive assessment of operating voltage feasibility

The feasible operating voltage at grid supply point is significantly affected by the high level of distributed energy resources (DERs) integration. However, while the operating voltage is typically defined by the transmission system operator (TSO), often the integration of DERs at specific nodes within the distribution system is not taken into account. This oversight can lead to security issue for the distribution system operator (DSO). Addressing this critical gap, this manuscript offers an in-depth analysis of voltage feasibility at the grid supply point. The TSO-DSO interaction has been utilized to estimate the revised limits of voltage, and the influence of several factors such as the level of DER integration, associated flexibility cost, system's demand level, and regulation of the reactive-to-active power ratio (Q/P) has been highlighted. For this, IEEE 9 bus system for TSO and 33 bus for DSO, are considered to estimate the balance condition between them. The revised voltage limits are estimated on DSO's 33-bus system. The study shows that DER integration reduces voltage range at the transmission -distribution (T-D) interface. However, high DER integration increases the feasible voltage range by enhancing flexibility. Cost willingness and activation cost widen the voltage range with minimal impact during peak load, while demand levels affect limits throughout the operation window. Furthermore, Q/P regulations have the potential to expand the feasible voltage range.