With the development of smart distribution networks

the soft open point(SOP)

as a sort of promising electronic device in place of traditional tie switch(TC)

can improve the operating flexibility of a distribution network. This paper analyzes the SOP control modes of an active distribution network with SOPs under normal and fault conditions. For the special case that an arising serious fault prevents some regions from the contact with the grid through switches

each of the referred regions is called an unconnected subnetwork

the rest regions that can contact with the grid are called connected subnetworks. Then a service restoration strategy to restore the black-out loads by cooperating SOPs with distributed generators(DGs)is proposed. The power-transferring capability of the connected subnetwork is taken into account

which can provide the corresponding constraints for the restoration of the unconnected subnetwork. The SOP operates in a Vf mode during the service restoration. The objective function consists of the minimum weighted total loss of power load

the least DGs out of the grid and the minimum network loss. A service restoration model for the distribution network with SOPs is developed. The optimization variables are the output voltages of tie switch and SOP. Moreover

the ant colony optimization and chaos algorithm are combined to realize the restoration strategy. Finally

the case studies are conducted on a single IEEE 33-bus system with an SOP and a double IEEE 33-bus system

which show the effectiveness of the proposed service restoration strategy in both recovery schemes and load fluctuation adaptability. The simulation results show that the restoration strategy can not only realize the maximum restoration of the unconnected subnetwork

but also ensure the normal operation of the connected subnetwork.