Contribution to the classification of power electronic assets in converter-dominated grids

The discussion on the stability of converter-dominated grids currently revolves around testing and comparing various scenarios of different grid topologies and different power electronic assets (PEA). One decisive aspect in this ongoing research is the control scheme of PEA and its interaction with the grid. As an increasing amount of proposals is emerging, addressing and comparing the individual solutions has become a considerable problem. One reason for this are the widely used terms grid-forming, grid-supporting and grid-feeding to differentiate between PEA that contribute with different degrees of ancillary services to the stability of power systems. Their suggestive character together with missing or incomplete term definitions are leading to confusion and even to wrong assumptions. A more comprehensive classification of PEA has recently been published by the ENTSO-E. Yet, a widely accepted and precise definition has not been finally agreed upon. This work intends to compare results from a strictly PEA based evaluation with rather grid oriented results from the ENTSO-E regarding relevant asset properties and a consecutive classification system. In a second step, concerning future benchmarking and certification processes, the classification system is extended to provide flexible terminology and to support the design of general test cases. The definition is applicable to all kinds of grids with PEA (micro-grids, AC transmission grids, HVDC, traction grids AC and DC as well as ship and aircraft grids) and can be used by grid operators, control scheme developers and PEA manufactures. A demonstrative example based on a purely power-electronic DC grid, including measurement results, confirms the reasoning presented and proves the applicability of the suggested methodology.