TSO-DSO interaction: Active distribution network power chart for TSO ancillary services provision

Within the timely framework examining interaction modes at the interfaces between transmission system operator (TSO) and distribution system operators (DSOs), this letter proposes the new concept of active-reactive power (PQ) chart, which characterizes the short-term flexibility capability of active distribution networks to provide ancillary services to TSO. To support this concept, an AC optimal power flow-based methodology to generate PQ capability charts of desired granularity is proposed and illustrated in a modified 34-bus distribution grid.