Adoption of soft open points for increasing the flexibility perimeter exploitation on power distribution networks

The optimal flexibility exploitation from Distributed Energy Resources on distribution systems may be limited by the typical radial operation of such networks, causing insufficient availability of flexible resources for solving specific technical issues or lack of competition among them with consequent higher costs of flexibility procurement in a local ancillary service market. Adopting soft open points in place of traditional mechanical tie switches (normally open) may help overcome this limitation by allowing active power exchange among adjacent feeders while preserving the distribution network’s radial operation. The paper presents an operational planning tool for MV distribution networks that optimises the exploitation of flexibility from available resources (generation curtailments and/or demand response) and the operation of soft open points (active and reactive power exchange). The tool uses a Linear Programming approach to assess the optimal flexibility a DSO should purchase in a hypothetical day-ahead local ancillary service market to guarantee a secure and adequate network operation. Tests have been executed on realistic distribution networks to show how introducing network flexibility through these modern power electronic devices contributes to making the flexibility exploitation from energy resources more valuable from the DSO point of view.