DC component detection in grid connected inverter systems, using a mid-ground low pass filter approach

Zhang, W; Armstrong, M; Elgendy, M

doi:10.1049/cp.2016.0207

DC component detection in grid connected inverter systems, using a mid-ground low pass filter approach

Lookup NU author(s): Weichi Zhang ORCiD, Dr Matthew Armstrong ORCiD, Dr Mohammed Elgendy ORCiD

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Abstract

© 2016, Institution of Engineering and Technology. All rights reserved.Transformer-less, grid connected, photovoltaic inverter systems are becoming increasingly popular due to their reduced volume and high efficiency performance. However, the potential risk of dc current injection into the grid is of significant concern in such systems, and strict guidelines and standards are normally in place to protect the integrity of the distribution network. Nevertheless, accurate determination of the dc current content in the inverter output is particularly challenging. This is primarily because the very small dc signals have to be extracted from much larger ac signals, and the measurements can be significantly influenced by noise. This paper investigates a novel method to detect small dc components in full-scale complex waveforms, using a simple low cost Mid-Ground Low Pass Filter (MGLPF) circuit. Results demonstrate the accuracy and robustness of the proposed circuit.