Contribution of Residential PV and BESS to the Operational Flexibility at the TSO-DSO Interface

The proliferation of distributed energy resources requires more interaction, or even coordination between distribution system operators and these resources so that secure and reliable operation of distribution grid is ensured. These resources can provide active and reactive power flexibility by adjusting their set-points (injecting/absorbing active/reactive power) in an aggregated manner so that they can offer services to the DSOs and/or TSOs. Such coordinated management of these resources can influence positively the transition to a CO2-neutral energy system, by increasing the profitability and, therefore, leading to higher proliferation of renewable resources, such as solar PVs. This paper proposes a methodology to approximate the flexibility of an active distribution grid at the point of interconnection with the transmission system. The focus is given to the contribution of residential PVs and battery energy storage systems to the amount and nature of the flexibility. An optimization-based approach is used to estimate the available active and reactive power flexibility at the TSO-DSO substation. The problem is formulated as an AC-optimal power flow and the methodology is tested on a modified 18-bus distribution system.