37.

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.

36.

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.

35.

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.

34.

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.

33.

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{%}.

32.

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.

31.

A. Uphues, K. Nötzold, R. Wegener and S. Soter, "Crowbar-less ride through of asymmetrical gric faults with DFIG based WECS" in 2017 IEEE AFRICON, 2017, pp. 1026--1031.

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 electromotive forces and rotor currents, which may damage the rotor-side converter, or adversely affect the DFIG's controllability are induced into the rotor circuit in case of voltage dips. To handle and limit the rotor currents in case of asymmetrical voltage dips without crowbar triggering, a virtual resistance control 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 control. The LVRT capability is verified with measurement results, recorded during a certification campaign at a 2.1 MW WECS concerning the Indian grid code.

30.

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.

29.

A. Uphues, K. Nötzold, R. Wegener and S. Soter, "Comparison of parameter identification approaches with linearised process models based on RLS for induction machines with P {\textgreater} 100 kW" in 2016 IEEE International Conference on Industrial Technology (ICIT), 2016, pp. 134--140.

Abstract:
This paper presents a comparison between a continuous time domain approach (CTD) and a discrete time domain approach (DTD) for parameter identification of induction machines P{\textgreater}100 kW fed with a voltage source inverter (VSI). The machine parameters are identified off-line, based on the reference voltage and the measured current at standstill and single-axis excitation by the VSI. The quality of the identified parameters is verified with the comparison of measured and estimated torque for the whole operating range, exclusively the field weakening region.

28.

A. Uphues, K. Nötzold, R. Griessel, R. Wegener and S. Soter, "Overview of LVRT-capability pre-evaluation with an inverter based test bench" in 2015 IEEE 24th International Symposium on Industrial Electronics (ISIE), 2015, pp. 748--753.

Abstract:
With increased renewable power penetration level the system operators of power grids require low-voltage ride-through (LVRT) capability of renewable power plants. The LVRT-capability has to be verified during the process of certification with precisely defined short circuit tests on a reactance based test bench. For the development of the fault ride through (FRT) capability the cost intensive reactance based test configuration is replaced by an inverter based voltage sag generator (VSG). This paper deals with an overview of the whole inverter based test configuration including the control structure of the grid emulator and the adjustment of the grid side converter's control structure to reach LVRT-capability as well as measurement results for the pre-evaluation.