Inter-Laboratory Comparison of Reference Systems for DC Power Quality Measurements

Low-voltage DC microgrids are a popular solution for a direct integration of more and more renewable energy sources. In this scenario, it is reasonable to expect that the power signal will not consist of pure DC components but will be affected by disturbances and power quality (PQ) events coming from the AC bulk grid as well as from switching power supplies or time-varying loads. To the state of the art, the normative framework does not provide a rigorous approach towards DCPQ analysis. We lack a clear and unambiguous definition of some quantities (e.g., DC power) or measurement methods (e.g., DC ripple). In order to solve this problem, the recent project DC grids has developed two reference systems for DCPQ at METAS and VSL laboratories. In this paper, we compare the systems' performance by means of a measurement campaign on the same transfer standard. The results confirm the consistency of the two reference systems and provide some insightful inputs for the standardization of these tests in the normative framework.