About Analysis of Emissions from a Switched Mode Power Supply

The paper is dedicated to the analysis in the frequency domain of the currents (in common mode and differential mode) which generate conducted emissions in the supplying cable of the equipment containing a switch mode power supply (SMPS). The performed simulation considers the standard CISPR 16-1-2 which refers to specifications, methods, and test apparatus for the measurements of disturbances and immunity to conducted emissions. One proposes solutions to limit and control the conducted emissions generated by the SMPS within the supplying cable that result into noise currents and high frequency currents within the range 150 kHz – 30 MHz that might interfere with other electric equipment. Various ways to limit the mentioned emissions are simulated and analyzed. The influence of the duty-cycle over the frequency spectrum from the conducted emissions range is considered and the worst case is determined. The conclusion is that the optimum filtering solution involves the use of an EMI filter, the results being compared to the CISPR 22 standard

Analysis of Common Mode Currents and Harmonic Pollution at Supplying Induction Motors from Static Converters with Variable Modulation Frequency

The problems of Electromagnetic Compatibility (EMC) in three-phase systems are less studied than single-phase or direct current, due to the smaller ratio of emissions relative to the rated power of such systems. This paper is focused on the problem of emissions in three-phase variable frequency drive systems in the low-frequency EMC range, specifically on the common mode current through the connected ground wire between the static converter and power grid. The common mode current is determined to be variable depending on switching frequency. For a deeper understanding Fast Fourier Transform was used to decompose the signal. Main parameter to understand the magnitude of common mode current was the RMS of the current. The decomposition showed a significant DC component which cannot be picked up by the used RF probe, thus presenting a noise offset necessary to be considered when calculating the total effective value of common mode current. The analysis was made on the time-domain representation and the frequency behavior of the converter. The paper suggests that the standard measurement in the low-frequency range and the picked-up signal are investigated enough, as there is a disparity in the impact of emissions in the low-frequency range compared to what off-the-shelf devices have to offer, which are standard compliant, but still present considerable emissions

Design of Proportional-Resonant Control for Current Harmonic Compliance in Electric Railway Power Systems

This paper presents the process of designing proportional-resonant controller for a four-quadrant rectifier in electric railway traction system. In the context of ever-stricter power quality and electromagnetic compatibility standards in electric railway power systems, developers of electric locomotives need to adapt with new ways to comply. This paper develops on the process of designing a four-quadrant rectifier proportional-resonant control for mitigation of low frequency current harmonic distortion, a novel method in the field of railway EMC. The control parameters are determined through analytical modeling of the rectifier through transfer functions. For the purpose of studying the harmonic distortion mitigation effects, only the current control loop was modeled and designed. The modeling starts with simplification of the model via large-signal modeling of the power converter. The parameters of the circuit then were used to develop the transfer functions, and select the appropriate parameter values of the current loop plant. The control loop and parameters were evaluated on test locomotive to validate the control, with results confirming the improved impact on the electromagnetic compatibility and conformity to regulation