A stepwise methodology for the design and evaluation of protection strategies in LVDC microgrids

Over the past years, there has been an increasing scientific interest in Low Voltage DC grids as an alternative to traditional Low Voltage AC grids, driven by the energy transition. However, fault detection and protection of LVDC microgrids still poses an important challenge for their breakthrough on a large scale. Due to the required speed and reliability of LVDC microgrid protection, an increasing amount of research is focussing on local, measurement-based protection algorithms. While several solutions for such a local, measurement-based fault protection algorithm have been proposed in literature, the design process of these algorithms is often unclear. As a result, it is often not straightforward to an LVDC grid designer how to tackle the design of an LVDC microgrid protection strategy. Furthermore, the framework within which the proposed algorithms are designed is often not discussed, as well as how well the algorithm will perform when the fault conditions deviate from this reference framework. Therefore, this paper presents a stepwise methodology for the design of fault protection strategies in LVDC microgrids with the aim of making this design process more straightforward and transparent. Furthermore, the proposed methodology allows to evaluate the robustness and boundaries of the designed protection strategy easily. The different steps of the methodology are discussed in detail and applied to a case study, followed by a sensitivity analysis of the developed protection algorithm to investigate its boundaries and improve its robustness.