Open Access

Astronomers and observatory operators often find themselves in a situation where they can hardly differentiate the signal of interest from the noise. Furthermore, they might experience system and instrument failures - permanent or temporary- whose root-cause might not be 100% clear. This is where the electric power grid and the grounding of the instruments and the observatory itself step onto the scene. The structure of the electric power grid that supplies astronomical observatories differs from that of a standard power grid. Observatories are not integrated into widespread mesh-type power grid configurations, but rather located at the end of so-called stub power lines or cables. Therefore, disturbances in the observatory cannot be properly compensated for by the grid. Uninterruptible Power Supplies (UPS) may be able to mitigate power quality issues such as over- or undervoltage phenomena, but they only address the symptoms and not the root cause or improper engineering of the power grid and power supply of the observatory. Previous studies have measured Power Quality parameters on site, which has led to further research on Power Quality at astronomical observatories. This study will answer the research question of whether a new approach to Power Quality measurements can provide additional information, particularly for remote power grids. The method confidently measures numerous voltage and current signals using a high-speed measurement setup that is commonly used in high-power high-voltage measurements. This setup can accurately identify both the symptoms, such as deviations in voltage or current signals, and the underlying causes that occurred beforehand. The tests are conducted at the Renewable Power Systems Laboratory of Aschaffenburg University of Applied Sciences. The high-bandwidth current sensors adapted to the recorder make for a novel setup. The benchmark measurements, setup, and results have been previously presented at conferences. This contribution highlights the need for further research on power grid disturbances and their proper mitigation. To mitigate high-frequency interference signals that may originate from power electronics, appropriate grounding techniques should be implemented for observatories.

The topology of the dual two-level inverter in combination with an electrical machine with open-end winding is an optimal solution for the realization of high requirements from the automotive sector for high-performance traction drives. In this publication, methods for extending the operating range and improving output voltage and current quality are presented for synchronous as well as asynchronous PWM methods for the entire operating range for this system configuration. Emphasis is placed on symmetrical power sharing between the inverters to maximize the power range. Optimal integration of the system is achieved by the topology-related possibility of DC fast charging of the energy storages from a DC grid without an additional charging unit.

The European Union-funded Advanced Superconducting Motor Experimental Demonstrator (ASuMED) project started in May 2017 with the purpose of demonstrating the benefits of a new, fully superconducting motor for reaching the targets established by the Flightpath 2050 plan. The project aims at a motor power density of 20 kW kg−1 using a high-temperature superconducting (HTS) stator. The rotor will use HTS stacks operating like permanent magnets. A highly efficient cryostat for the motor combined with an integrated cryogenic cooling system and associated power converter will be used. This article provides a general overview of the prototype that is currently being assembled and that will be tested soon.

Electric drives in road vehicles with a battery as energy storage are about to be introduced to the mass market. In order to guarantee the quality and operational safety of battery-powered vehicles, considerable efforts must be made by car manufacturers and their suppliers. Since the properties of the batteries significantly determine the performance of the vehicles, special test benches with precise measuring systems are required for the accurate determination of the battery properties. The safety devices of the traction batteries must also be tested on high-performance test benches. In this paper the necessary test benches and the corresponding measuring systems are presented. Estimations of the measurement uncertainty and possibilities to increase measurement accuracy are presented.

This paper aims to present an optimized inverter topology, based on the dual two-level inverter, for feeding an open-end winding electrical machine with superconductive stator windings and a superconductive rotor. In order to achieve a high torque density, the stator windings are built of several superconducting tapes being in parallel. One inverter of the dual two-level inverter is equipped with powerful IGBT semiconductors and supplies the machine with energy. The second inverter is a low voltage MOSFET inverter that monitors the superconductor resistance (quench detection) and balances the current on the parallel superconductive tapes for guaranteeing an optimum operation with respect to the superconductive losses.