Assessment of Flexibility Region at TSO-DSO Interface with Dispatchable Resources

With increased dispatchable distributed energy resources (D-DER), distribution systems have increased capacity to support the transmission side. This paper assesses the effect of D-DER capacity on the flexibility region at transmission-distribution (T-D) interface. An optimization problem is formulated to obtain the minimum D-DER capacity required to make a particular T-D interface injection feasible. The proposed assessment considers locational effects of D-DER with distribution network structure. This work highlights that at a particular node, there exists a maximum D-DER capacity beyond which D-DER cannot help increase the flexibility region. Simulation results are presented for the IEEE 34-Bus system, highlighting the importance of D-DER location and maximum injection levels.