7.

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.

6.

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.

5.

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.

4.

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{%}.

3.

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.

2.

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.

1.

A. Bartsch, F. Senicar, S. Kratz and S. Soter, "Enhanced FPGA based three level space vector pulse width modulation with active neutral point balancing" in 2013 IEEE Energy Conversion Congress and Exposition, 2013, pp. 1748--1753.

Abstract:
This paper presents an FPGA based implementation of an improved space vector pulse width modulation for neutral point clamped three-level topologies. For this purpose the flatspace modulation calculating the timings is used in combination with an optimized switching pattern to reduce the switching edges to a minimum. Additionally a combination of two methods for balancing the neutral point is developed which are both implemented without adding any additional harmonics to the modulated output.