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The frequency dependent grid impedance at the terminals of an electrical supply grid is an essential parameter for power quality and grid feedback analysis. In this contribution the identification of the grid impedance is achieved using spectral excitation currents at the corresponding grid connection point, which generate measureable changes in the grid voltage spectra. Different measurement systems based on this method have been successfully realized for the low-and medium-voltage level. A measurement system for the high-voltage level is currently being realized. The application of the measurement systems are facing quite different external framework conditions leading to specific system designs for each measurement device. The spectral grid impedance identification on these voltage levels is done through fast switching of an ohmic load with power electronic. The requirements and setup of the grid impedance measurement systems are outlined and measurement results on the low-and medium-voltage level are presented and discussed. The systems can be used to evaluate grid connection points and to verify other active or passive grid impedance identification methods on different voltage levels.

This paper deals with an aircraft weight optimization through an analysis of different loadconverter-architectures. A major effort in the development of new aircraft is the reduction of the weight. This results from a direct relationship between aircraft mass and efficiency. At a first step the global onboard converter architecture is analyzed. In addition to the conventional architectures two DC-grid architectures are shown. In the second step a weight reduction through converter optimization is presented.

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