The study of Power Quality phenomena in medium voltage direct current (MVDC) and hybrid alternate and direct current (AC/DC) distribution networks represents a research topic of current interest from both a scientific and regulatory point of view at national and international level. In this context, in this year of research, RSE decided to sign a collaboration with the University of Cagliari and the Polytechnic of Milan to define signal processing techniques specifically developed to the study and identification of continuous disturbances typical of DC and AC/DC hybrid networks, proposing solutions suited to the relevant band and the disturbance characteristics.

In particular, it was proposed to extend the concept of remote synchronized measurements, commonly adopted in alternating current systems, also to direct current systems. This would make possible to observe dynamic disturbances and to monitor the energy quality, by detecting and measuring the most significant ripple components and enabling the estimation of the origin of these disturbances.

After a brief survey on the techniques presented in the literature, a first algorithm was developed for this purpose, based on a multi-frequency Taylor-Fourier model suitably modified for applications to DC systems. The performances obtained were evaluated through numerical simulations performed on a realistic situation, namely a direct current load powered by a 12-pulse rectifier operating in both stationary and dynamic scenarios. Furthermore, a first algorithm for identifying the disturbance (load/network) was applied to the same example.

The results show how the proposed method clearly outperforms a conventional approach based on the discrete Fourier transform when considering non-nominal conditions and how it can identify the source of the disturbance.

The Report is available on the Italian site