Congestion Management in Distribution Networks With Asymmetric Block Offers

Abstract

In current practice, the day-ahead market-clearing outcomes are not necessarily feasible for distribution networks, i.e., the network constraints might not be satisfied. Hence, the distribution system operator may consider an ex-post re-dispatch mechanism, exploiting potential flexibility of local distributed energy resources including demand response (DR) units. Many DR units have an inherent “rebound effect,” meaning a decrease in power demand (response) must be followed by an increase (rebound) or vice versa, due to their underlying physical properties. A naive re-dispatch mechanism relying on DR units with non-negligible rebound effect may fail, since those units may cause another congestion in the rebound period. We propose a mechanism, which models the rebound effect of DR units using asymmetric block offers—this way, those units offer their flexibility using two subsequent blocks (response and rebound), each one representing the load decrease/increase in a time period. We demonstrate that though linear approximations of optimal power flow (OPF) models as potential re-dispatch mechanisms are more computationally efficient, they can result in a different dispatch of the asymmetric blocks than an exact convex relaxation of an AC-OPF model, and therefore, must be used with caution.