Complex Power Flexibility Evaluation using Energy Arbitrage between Transmission and Distribution

Abstract

The high-level integration of distributed energy resources has given rise to system security challenges at both transmission and distribution grid levels. A major share of these distributed energy resources is integrated at the distribution end. A constructive solution for system security challenges is to provide flexibility services by the distribution grid itself. The methodology presented in this manuscript evaluates complex power capability and flexibility from these distributed energy resources at primary substation node that connects transmission and distribution at physical levels using probabilistic optimal power flow based on the Monte Carlo method. Monte Carlo is used to generate various scenarios of load and generator flexibilities. This novel research work provides an extensive evaluation of both capability and flexibility regions to quantify various active power ramp services to achieve frequency control ancillary services indicating actual flexibility at transmission-distribution node. Energy arbitrage between transmission and distribution is simulated as an alternating current optimal power flow problem for different scenarios of flexible loads and generators. The analysis is validated using IEEE 5, 9 and 33 bus systems. Effects of active-reactive power dependency, distribution of load and generator flexibility and size of the test system have been highlighted in results. The results highlight the applications of the flexibility region as a subset of the capability graph.