Common-Mode and RF EMI in a Low-Voltage DC Distribution Network With a PWM Grid-Tie Rectifying Converter

In this paper, common-mode (CM) and radio frequency (RF) electromagnetic interferences (EMIs) in a low-voltage direct current (LVDC) distribution network are investigated. LVDC being a novel approach to public electricity distribution, a research site was set up in a public rural-area distribution network to enable comprehensive studies concerning the LVDC distribution. In a previous journal article by the author, CM and RF EMI were studied with the objectives: 1) to determine whether there are disturbances that exceed the requirements of the standards, or whether the CM current could cause safety issues in the converter-fed user-end network; 2) to discuss the effects of the CM current on the feasibility of power line communication in a dc network; and 3) to analyze the measured RF disturbances. However, standardization is still lacking for the frequency range from 2 to 150 kHz. In this paper, in situ measurements are conducted on the LVDC research site to define the levels of disturbance. The results in the previous journal article were based on the research site with a thyristor bridge rectifier, and when the rectifier was upgraded to a PWM grid-tie rectifying converter, disturbances were measured again. In this paper, these results are analyzed against the previous measurements to define whether additional measures are required. Further, the design and implementation of a CM filter and its effects on the disturbances of the dc network are analyzed.