Abstract：While a large number of distributed generator（DG）keep penetrating into distribution networks，the problems such as voltage violation and network power congestion become more and more serious. Soft open point （SOP）can quickly achieve flexible interconnection and accurate power flow control，effectively addressing the challenges caused by the integration of DG. Considering the installation priority of SOP on branches where active

power is heavily affected by loads，an intelligent soft switch site slection and capacity determination strategy based

on branch active power sensitivity analysis was proposed. Firstly，a load growth factor was introduced into the

power flow equations，and the branch power sensitivity，which reflects time series variation of DG output and load，was theoretically derived. The selection of SOP sites was then ranked according to this sensitivity value. Secondly，the model of SOP site slection and capacity optimization was established，which was solved using a second-order cone algorithm. Finally，validation was conducted on the improved IEEE 33 node distribution system. Results show that the proposed method can affectively save annual comprehensive operation cost of distribution networks，reduce system network losses and improve node voltage deviation.

      Key words：flexible distribution network；branch power sensitivity；soft open point（SOP）；site selection and

capacity determination；second-order cone planning