  The ever-increasing penetration of Distributed Generators (DGs) in
distribution networks suggests to enable their potentials in better fulfilling
the restoration objective. The objective of the restoration problem is to
resupply the maximum energy of loads considering their priorities using minimum
switching operations. Basically, it is desired to provide a unique
configuration that is valid regarding the load and generation profiles along
the entire restorative period. However, this unique configuration may not
satisfy at the same time: I) the DG start-up requirements at the beginning of
the restoration plan and II) the topological conditions that would allow the DG
to provide later on the most efficient support for the supply of loads.
Therefore, it is proposed in this paper to allow a limited number of
reconfiguration steps according to the DG start-up requirements. In addition,
this paper presents a novel formulation for the reconfiguration problem that
accounts for partial restoration scenarios where the whole unsupplied area
cannot be restored. The decision variables of the proposed multi-step
restoration problem are: I) the line switching actions at each step of the
reconfiguration process, II) the load switching actions during the whole
restorative period and, III) the active/reactive power dispatch of DGs during
the whole restorative period. A relaxed AC power flow formulation is integrated
to the optimization problem in order to ensure the feasibility of the solution
concerning the operational safety constraints. The overall model is formulated
in terms of a mixed-integer second-order cone programming. Two simulation
scenarios are studied in order to illustrate different features of the proposed
strategy and to demonstrate its effectiveness particularly in the case of
large-scale outages in distribution networks.
