Lehrstuhl für Elektrische Maschinen und Antriebe

Veröffentlichungen



79.
K. Nötzold, N. Brissing, A. Uphues and S. Soter, "Generalized Integrator Based Active Damping" in 2022 IEEE 7th Southern Power Electronics Conference (SPEC), 2022, pp. 1--6.

Abstract:
To actively damp the inherent resonance of a LCL-topology applied as an output filter for a grid-connected inverter without capacitor current measuring capability, the derivative of the capacitor voltage can be utilized and fed back instead. However, digital implementation of this derivative is generally challenging due to noise-sensitivity or an introduced phase lag. In literature a second-order nonideal generalized integrator is proposed to indirectly differentiate the capacitor voltage and successfully tested in combination with a control loop based on grid current feedback. Here, this damping approach is adapted to a control loop based on converter current feedback. Simultaneously, and in contrast to more complex damping functions suggested in literature, the phase lag caused by computational delay is particularly compensated by simple proportional capacitor voltage's derivative feedback. To determine the required feedback constant, the feedback path is transformed into an equivalent impedance, connected in parallel to the filter capacitor. Consequently, the generalized integrator as well as the proportional feedback constant is simply parameterizable regarding the desired overall damping constant. Finally, experimental results with a 625 kW inverter demonstrate the active damping capability across a large frequency range.
78.
M. Weisbach, T. Schneider, D. Maune, H. Fechtner, U. Spaeth, R. Wegener, S. Soter and B. Schmuelling, "Intelligent Multi-Vehicle DC/DC Charging Station Powered by a Trolley Bus Catenary Grid", Energies, vol. 14, no. 24, pp. 8399, 2021.

Abstract:
Abstract This article deals with the major challenge of electric vehicle charging infrastructure in urban areas—installing as many fast charging stations as necessary and using them as efficiently as possible, while considering grid level power limitations. A smart fast charging station with four vehicle access points and an intelligent load management algorithm based on the combined charging system interface is presented. The shortcomings of present implementations of the combined charging system communication protocol are identified and discussed. Practical experiments and simulations of different charging scenarios validate the concept and show that the concept can increase the utilization time and the supplied energy by a factor of 2.4 compared to typical charging station installations.
77.
S. Kratz, B. Krüger, R. Wegener and S. Soter, "Expansion of a Trolleybus Infrastructure towards a 100{%} Renewable Energy Usage" in 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC), 2021, pp. 0233--0236.

Abstract:
The german government furthers a research project targeting the full electrification of the largest trolleybus network in Germany in prospect of deriving a pilot scheme for major cities. Based on the good interim results, another near future aim arised: operation of the trolleybus network with 100{%} renewable energy. To achieve this, the large-scale integration of photovoltaic arrays in combination with second life bus batteries into the network is planned. This paper presents the actual status of the research project and the already closed steps towards the aim. It presents measurement results of the developed hardware from the laboratory and the last adaptations for field testing. Overall the measurements show a high efficient integration of photovoltaics and batteries which leads to a positive prediction regarding the aim with an integration and interaction in large-scale.
76.
D. Maune, B. Krüger, P. Sahm and S. Soter, "Speed Control for Lifting Devices with Conical Cable Drum through Indirect Position Determination" in 2020 IEEE International Conference on Industrial Technology (ICIT), 2020, pp. 401--405.

Abstract:
Lifting devices are often provided with a spring to compensate their constant weights. But because the force of a spring is depending on its stretch, the compensation ratio during a lifting process is fluctuating. By changing the characteristic of the load with the help of a variable radius drum it is possible to mitigate this drawback. In this paper a torsion spring and a conical cable drum are used for compensation. Because the wound cable length per revolution is changing, the lifting speed also varies. For the introduced speed controller the position of the drum is measured with an absolute, magnetic sensor. The actual lifting speed is then indirectly determined by calculation utilizing the cable drum parameters.
75.
S. Kratz, P. Hanses, B. Krüger, R. Wegener and S. Soter, "Integration of Second Life Batteries into a Smart Overhead Contact System based on SiC-Technology" in 2019 IEEE Transportation Electrification Conference and Expo (ITEC), 2019, pp. 1--5.

Abstract:
This paper presents the starting situation and some interim results of a research project with the aim of a fully electrified short-range public transportation in a German town called Solingen. It gives an insight to the existing trolleybus infrastructure and the benefits of second life battery usage. Following, the design configuration of a refurbished trolleybus battery system for stationary usage in substations is shown and evaluated. Based on this a new silicone carbide power electronic for a direct integration of stationary battery systems are proposed and evaluated. Available semiconductors for the prototype are specified and compared by measurements. The results show that the integration of trolleybus batteries can be done with high system efficiency.
74.
S. Kratz, A. Schmidt, B. Krüger, R. Wegener and S. Soter, "Power Supply of a Short-Range Public Transportation System Based on Photovoltaics - Potential Analysis and Implementation" in 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC), 2019, pp. 3077--3081.

Abstract:
This paper answers the question of if an existing short-range public transportation system in a German town called Solingen could be exclusively supplied by photovoltaics and presents a fitted device for energy conversion. Based on the results of the proposed method for a photovoltaic potential analysis, the above question is answered and the main benefits of the direct integration of photovoltaic arrays are shown. The presented measurements of a 10kW prototype show that a high conversion efficiency can be achieved.
73.
T. Schneider, S. Kratz, R. Wegener and S. Soter, "Symmetrical Bidirectional CLLC-Converter with Simplified Synchronous Rectification for EV-Charging in Isolated DC Power Grids" in 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE), 2019, pp. 990--995.

Abstract:
This paper presents a bidirectional CLLC resonant converter for the use in electric vehicle fast charging applications, fed from a trolley bus DC power grid. Bidirectional converters generally introduce an increase in design complexity as well as a decreased power density and conversion efficiency, compared to their unidirectional equivalents. The presented converter, because of its symmetrical layout, is able to concentrate all necessary resonant inductances in one passive component and uses a simplified sensorless synchronous rectification technique in order to mitigate these drawbacks. A 12.5kW CLLC prototype for input voltages between 600-800V and output voltages between 300-400V is used for validation. The achieved maximum efficiency equals 96.6{%}.
72.
B. Krüger, S. Kratz, T. Theopold and S. Soter, "Wear Reduction Control Method in a Blade Pitch System of Wind Turbines" in 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE), 2019, pp. 1107--1112.

Abstract:
Mechanical transformation of speed is needed in a lot of industrial applications but it is attended by backlash. Gear parts without closed linkage can accelerate and crash to another. So with the backlash comes the wear. There are many technical solutions and ideas to reduce the backlash by mechanical and electrical components and adaptions, but in most cases with the goal to increase the precision. In some applications, like the described pitch drive, the precision is not the problem and the increasing costs for backlash elimination are not to justified because the reduction of wear is more important. Further the extensive adaption has influence on functional safety and maintenance. This paper gives a short overview of mechanisms that reduce the wear in a given application without mechanical adaptions, only by adding a software module. In the first step backlash is detected and in dependence on its reason in a second step a reaction is induced by the drive to spare the mechanics.
71.
S. Kratz, B. Krüger, R. Wegener and S. Soter, "Integration of Photovoltaics into a Smart Trolley System Based on SiC-Technology" in 2018 IEEE 7th International Conference on Power and Energy (PECon), 2018, pp. 168--173.

Abstract:
This paper gives an insight to a research project with the aim of a fully electrified short-range public transportation in a German town called Solingen. It starts with an overview of the special characteristics of the existing fully isolated overhead contact system and then derives the projected system. A new silicone carbide power electronic and the necessary control algorithms for the direct integration of photovoltaic arrays are proposed and evaluated. The measurement of a first small volume 10kW prototype inverter shows that the integration can be done with high efficiency.
70.
A. Uphues, K. Nötzold, R. Wegener and S. Soter, "DFIG's virtual resistance demagnetization for crowbar less LVRT" in 2017 IEEE 12th International Conference on Power Electronics and Drive Systems (PEDS), 2017, pp. 265--270.

Abstract:
Due to the increased renewable power penetration level renewable power plants have to provide low-voltage ride-through (LVRT) capability with simultaneous dynamic voltage support, to ensure the grid stability during grid faults. Concerning doubly fed induction generator (DFIG) based wind energy conversion systems (WECS) large transient electromotive forces (EMF) and rotor currents, which may damage the rotor-side converter (RSC), or adversely affect the controllability of the DFIG are induced into the rotor circuit in case of voltage dips. To limit the rotor currents and to accelerate the transient flux component's or transient electromotive force's damping respectively, a virtual resistance demagnetization approach based on the standard dq-control in the synchronous reference frame is discussed. The theoretical results are compared with those of more demanding virtual inductance and virtual impedance approaches. Additionally, to increase the IGBT's current conductivity, a reduction of switching losses due to a simple pulse pattern optimization is provided. The LVRT-capability is verified with measurement results, recorded during a certification campaign at a 2.1 MW WECS in India, concerning the Indian grid code.

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