Metrics for Conducted Emissions Assessment up to 150 kHz in Grid-connected Systems with Power Electronic Converters

Abstract

This paper presents an analysis of power quality metrics for conducted emissions assessment in ac/dc and dc/ac power electronic converters (PECs), in the frequency range from dc to 150 kHz. As regards the dc side, it is discussed how actual voltage and current waveforms can significantly differ from the ideal constant dc value and alternating components can have not negligible amplitudes. Also at ac side, voltage and current signals are not sinusoidal and they can be affected by the presence of harmonics in a wide frequency range, due to the PECs switching operation. In this framework, metrics to be adopted for conducted emission assessment are not univocally defined, and standards consider different approaches. In the paper the investigated metrics are those considered in current standards for power quality and harmonics measurements in ac systems in the different range up to 150 kHz. The same metrics are adopted for signals analysis at the dc side. The effectiveness of such metrics is investigated by means of experimental measurements, which have been carried out on a real case study test system, consisting of a grid connected PEC and a battery pack, operating in both charging and discharging mode.