Power Converter Impedance and Emission Characterization Below 150 kHz

IEC standardization is preparing general conducted emission limits for grid connected power converters in the frequency range between 2 kHz and 150 kHz, which has until recent years only been regulated for some categories of equipment. With the necessity of analyzing and estimating power converter behavior, this paper proposes a black-box modeling approach suitable for this new frequency range of interest. A method for measuring the dynamic power converter impedance when powered and in operation has been developed and proven in practice by superposition of a multi-tone signal onto the AC input voltage to the power converter under different load conditions. Later, through extraction of the noise source, an equivalent circuit diagram of the power converter is developed which can be used for emission estimation and further analysis such as EMI filter designing. The provided experimental results showed high accuracy of the proposed method and its suitability in estimating EMI below 150 kHz as a cost-effective and time-efficient approach.