Aggregation of Distributed Energy Resources and Energy Storage Systems in Active Distribution Networks: A Critical Review

The transition of modern power systems is going through the challenges of uncertainties originating from equipment unavailability, forecasting errors, market fluctuations, prosumer behaviors, regulatory and policy changes, and extreme weather conditions. These uncertainties can cause deviations from the planned operating points leading to non-optimal and even infeasible operation conditions. Energy storage systems (ESSs) can address these challenges in active distribution networks by compensating deviations caused by uncertainties. Consequently, aggregating distributed energy resources (DERs) and ESSs in active distribution networks is a key research area. This paper first introduces these uncertainties and their imposed challenges on aggregated systems. Moreover, correlations and interdependencies among uncertainties and their impacts on aggregating DERs and ESSs are thoroughly investigated. Subsequently, a critical review of the state-of-the-art aggregation optimization approaches is presented, and the comparison is made between static and dynamic DER-ESS aggregation processes. Next, the practical requirements and applications of DER-ESS aggregation are investigated. Finally, conclusions and future research directions in the area of DER-ESS aggregation are presented.