Distribution power flow management utilising an online optimal power flow technique

This paper describes the current connection regime for distributed generation (DG) in the UK and presents a novel application of the Optimal Power Flow (OPF) technique for automatic power flow management (PFM) to manage thermal constraints in distribution networks. OPF formulations have been used, in an offline mode, as a power system planning tool for several years. The novel implementation of OPF for ‘corrective’ PFM in an online operational mode, for MV distribution networks, is presented and tested in this paper. The authors demonstrate, through simulations conducted on a commercially available substation computer, that such an application of OPF can represent first on, last off generator connection agreements that reflect the current principles of access in the UK. Two case study networks, a 33kV and an 11kV, provide the basis for assessment of the OPF-based PFM algorithm in terms of computation time to arrive at a solution in the event of a network thermal excursion and the level of DG curtailment necessary to meet network thermal limits. Assessments are made and fully discussed of the suitability for an OPF-based approach for distribution network management within an online network control scheme including discussion of the important consideration of control robustness.