The process of decarbonization of the electricity system requires an increase in power generation from renewable sources and widespread deployment of charging stations to ensure the use of electric vehicles to replace classic endothermic engines. This implies, for the electric system, an aggravation in terms of the disturbances in the grid, mainly due to the increasing presence of electronic power converters. As a result, it is necessary to monitor continuously the power quality events occurring in the network; the digitization of the electricity system allows us to create a broader network of measurement systems, thus benefiting from the potential of a distributed approach.

Currently, the voltage and current signals in the electricity transmission and distribution network are mostly measured by means of classical inductive measurement transformers, which are characterized by both excellent accuracy at nominal voltage and industrial frequency and significant long-term stability; however, they have the disadvantage of having nonlinear amplitude and frequency behavior with the consequent degradation in measurement accuracy the further from nominal conditions we move. They also have analog output, which must be digitized for remote monitoring. For this reason, we decided to develop a new technique to compensate for the non-idealities of measurement transformers, based on the Volterra integral, the calculation of the relative extended kernels and the physical parameters of the component itself.

This ensures model characterization that can be easily applied in the industrial field. The developed technique showed that it is possible to reduce the ratio and phase errors of inductive measurement transformers by several orders of magnitude as compared to using the nominal transform ratio alone, especially in the case of measuring harmonic components. A new prototype Stand-Alone Merging Unit was then developed equipped with innovative features compared to those defined by the current standard.

The prototype was developed with the following objectives: guaranteed high accuracy for the measurement of the component at the fundamental frequency and for the related harmonics, up to the fiftieth; computational capacity such as to ensure the application of non-ideality compensation algorithms to the measurements made and of the main algorithms for the estimation of Power Quality phenomena; and guarantee the sending of the acquired data, with and without compensation, via standard communication protocols.

Activities will continue with the experimental validation of the developed algorithm and the final design of the boards of the new SAMU-NG prototype.