Design and Characterization of a Stand-Alone Merging Unit

Merging Units (MUs) play a key role in enhancing the levels of security and the reliability of power systems, allowing for advanced remote diagnostics. Some of the benefits are a more efficient transmission of electricity and a better integration with renewable energy systems. In this article, an implementation of a Stand-Alone Merging Unit (SAMU), compliant with the IEC 61850-9-2 standard and based on a low-cost ARM microcontroller, is described. It acquires two signals, one voltage and one current, and it sends the samples over the ethernet connection. A high-resolution Analogue-to-Digital Converter (ADC), synchronised to the Universal Time Coordinated (UTC) through a Global Positioning System (GPS) disciplined oscillator, is used. The opportune insulation and conditioning stage have been designed. Several tests have been performed, varying amplitude, frequency, and phase of the input signals, in order to evaluate the metrological performance of the proposed SAMU and they are here discussed.</p

Detection of dips, swells and interruptions in DC power network

The recent developments in power electronics have greatly increased the number of appliances that operate in DC and, contextually, the main distributed energy sources such as photovoltaic systems and fuel cells are inherently of DC nature. Therefore, a better integration of these devices into the electrical grid can be achieved with a direct connection in DC, avoiding all the additional losses due to the energy conversion stages currently employed in the traditional AC distribution grid. On the other hand, high voltage transmission in DC (HVDC) offers lower costs due to reduced losses in transmission. Nevertheless, at present, there is a lack of international standards that define Power Quality (PQ) metrics for DC grids. This paper makes a review of the technical report IEC-TR-63282 that is a first normative effort to this aim. Moreover, the authors suggest measuring methods to evaluate dips, swells and interruptions. The measuring method has been finally applied to PQ phenomena detected on simulated and experimental data to evaluate the effect of the time interval adopted in the assessment of these events