A High-Frequency Digitiser System for Real-Time Analysis of DC Grids with DC and AC Power Quality Triggering

Abstract

The presence of DC grids in distribution networks is being increased nowadays and is expected to be quite relevant in a near future, due to several advantages compared to traditional AC systems. Regardless of this, Power Quality in DC grids (DC PQ) (voltage variations, transients, spectral components, etc.) still remains not properly considered and there is a lack of reference normative documents such as standards, application guides or technical reports for their application. In this context, it is necessary to obtain more experience on real measurements, in order to define appropriate DC PQ parameters and limits that assess a reliable operation of the whole power network and eventually lead to establishing a reference frame acceptable for both generation sources and final users. In this work, a novel high frequency (up to 4 MS/s) digitiser system is presented for the study of DC PQ events. The system is designed to acquire waveforms with triggers fired by events in both DC and AC signals. The captured signals are pre-processed in real-time to be able to recover pre-trigger information stored in memory. The system was installed in a real DC micro-grid and configured to take data in an unattended way. Additionally, the results of the first months of data acquisition are presented.

Keywords

• low voltage DC networks
• DC power quality
• DC power quality indices
• DC measurement techniques
• standardisation
• high-frequency acquisition