Bartosz Woszczyna

Currently, manufacturers of power-electronic components are trying to introduce the silicon carbide (SiC) technology in their products and MOSFET transistors made with this technology are available on the market. They are characterised by a significantly higher operating frequency, reaching even 100 kHz and low switching losses. The application of this type of devices causes high voltage gradients at the inverter output, which can lead to increased inverter electromagnetic disturbances. This article presents test results and a high-frequency analysis, allowing for a preliminary evaluation of the use of SiC transistors in inverters in the context of electromagnetic compatibility.

Producers of power electronics components are currently introducing silicon carbide (SiC) to their products and MOSFET transistors made with this technology, working at a wide voltage and current range, are affordable. They are distinguished by high frequency of operation, reaching 100 kHz and low switching losses. Silicon carbide technology allows to build power converters, which are characterized by high efficiency, smaller dimensions, smaller passive components and higher thermal tolerance in comparison with traditional technology (Si). The aspect of the electromagnetic compatibility of SiC technology converter was analyzed in the article. Determined levels of interferences generated by the converter into the supply grid in the range of harmonics and inter-harmonics were presented. Measurement results of electromagnetic conducted disturbances were presented. Increased levels may make it difficult to fulfil standard requirements and may adversely affect the operation of devices connected to the same supply network. Additionally, conducted disturbance levels at converter output have also been analyzed, of which increase may lead to problems in providing the so-called inner compatibility of the tested circuit or may be a source of radiated electromagnetic emission. The results of tests and analysis, presented in the article, conducted for wide frequency range, allow to evaluate the silicon carbide (SiC) technology application for a converter in the EMC scope.

The requirements relating to the emission of auxiliary AC supply sockets in traction vehicles have been extended in standard PN-EN 50121-3-2:2015 by voltage harmonics measurement. This applies to the public on-board AC supply grid which is accessible to all passengers. It is concerned with providing the quality of power supply which is required by computer devices and mobile phone rechargers. This article presents the requirements and test methods resulting from extended standard scope. Normative factors, for which levels of permissible voltage harmonics in the public supply grid of traction vehicle have been defined are discussed. Examples of comparative results obtained from measurements and analyses of voltage harmonics within on-board supply grids are also presented. The presented results include extended calculations of distortion factors for groups and subgroups of supply voltage harmonics. In order to improve the quality of voltage within the on-board grid, which did not meet the requirements, simulation calculations were performed and an additional output sinusoidal filter was proposed.

The paper presents the load currents of two tram traction substations. These substations power lines with different characteristics of tram traffic. Loads were analysed for one working day and one public holiday. Attention was paid to the differences and similarities in the current waveforms. The demand level was assessed, with respect to the rectifier units in the substations. The time series method was used, inter alia, and chiefly an analysis of the characteristics of autoregression and partial autoregression was carried out, to act as a diversity index with respect to the nature of variability in the analysed traction load currents.

The first part of this paper presents a comparison of the measured and simulated results of the load variability of rectifier units of a tram traction substation. The subject of the tests was a power supply substation for the contact line of a tramway, the profile and traffic of which was known. After a positive appraisal of the applied simulation method, an assessment of the range of load variability for the rectifier units took place for a hypothetical situation involving the concentrated disposition (layout) of the traction substations (socalled micro-substations). The results acquired under the described circumstances are presented in the second part of this paper.