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Research Into Possibilities to Increase Input Impedance of Voltage and Frequency Converters Fed from DC Network

High level requirements have been applied to static voltage and frequency converters by which a tolerable level of current disturbances, generated into the network by means of converters, is determined. The European railway supply network is specific due to two types (dc & ac) and four voltage levels. One of the very important requirements when converter is considered operating on dc network is the input impedance higher than permitted by UIC 550 VE regulations in the frequency range from 50 Hz to 100 kHz. Based on the research by means of mathematical models and physical model 2, 5 kW power, the solution has been chosen and described in this paper. It is the active filter in voltage and converter dc link, carried out as a controlled boost converter, which enables to meet the requirements regarding the input impedance. The dc link voltage maintenance in steady and transient states, during the load or input voltage changes, has been solved at the same time by controlling the boost converter. The presented measurement results on the physical model give an insight into the dependence of the input impedance on the impressed signal frequency according to UIC 550 VE.

Input impedance; current disturbances; dc network; voltage and frequency converter; railway supply network; boost converter

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