Industrial Overview of Back-to-Back VSC Power Links in MV Distribution Networks

This paper presents an overview of Back-to-Back-VSC type power links as a promising technology, yet little deployed, to enhance the operational flexibility of MV distribution networks. It provides a technical insight of four cornerstones that Distribution System Operators could consider from a planning perspective: power electronics, backhaul network characteristics, dispatching control strategies and protection requirements. Details on power electronics and protections are given with an industrial approach, differential with information available in academic works and generic reviews. The paper showcases figures of multi-megawatt size converters and uses a real 30kV distribution network model to assess converter capacity selection and protection requirements. Additionally, different control strategies of Back-to-Back VSC power links are introduced showing the influence that backhaul network can have over them. Seen from a dispatching perspective, an overview of different control strategies is presented describing options available for MV grids that account for different digitalization levels. The overview given in this paper allows to have a clear vision of technology readiness, integration requirements and technical limitations of Back-to-Back VSC power links for its deployment in MV distribution networks.