Jorg Roth-Stielow
University of Stuttgart
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Publication
Featured researches published by Jorg Roth-Stielow.
2010 Emobility - Electrical Power Train | 2010
Marco Weckert; Jorg Roth-Stielow
This paper presents a novel control strategy, on the example of a three-phase voltage source inverter, to increase the life-time of power semiconductor devices. Based on an online estimation of the junction temperatures the switching frequency is modified through the control to decrease thermal cycles. In addition the neutral point potential can be shifted using a flat-top method, resulting in an additional reduction of thermal cycles. So using the presented control system in-stead of an ordinary pulse width modulation the lifetime of power semiconductor devices is increased significantly.
power electronics specialists conference | 2008
Ulrich Ammann; René Vargas; Stephan Rees; Jaume Serm; Jorg Roth-Stielow
Power converters with semiconductors switching only at predefined, equidistant instants - known as ldquodiscrete-time switchingrdquo, ldquosynchronized switchingrdquo or ldquoclocked commutationrdquo - show considerably different current control behavior compared to pulse-width modulated (PWM) converters with linear current con trollers. This paper presents and explains some of the effects of discrete-time-switching on output current waveforms, especially when using a predictive switching state selection algorithm. Typical characteristics of generated switching state patterns are presented. A single-phase and a three-phase inverter controlled by a predictive discrete-time modulation strategy are considered. Analytical, experimental and simulation results show that average switching frequency and error current RMS are well defined, in spite of the inherent randomness of the control scheme.
international conference on industrial technology | 2010
Martin Braun; Oliver Lehmann; Jorg Roth-Stielow
This paper presents a new innovative method for sensorless rotor position estimation at standstill for high speed PMSM. To avoid critical thermal losses in the high speed PMSM a controlled LC filter is connected between the machine and the inverter. This additional filter leads to failure of many known methods for sensorless rotor position detection at standstill. The presented method is suitable for accurate and reliable detection of the rotor position at standstill. The function principle is based on voltage pulses applied on the LC filter and the high speed PMSM. Based on measured stator currents and voltages a special structure to model the system behavior and to calculate the actual rotor position is used. This allows a parameter insensitive operation. All theoretical proposals are proved by practical experiments.
international conference on industrial technology | 2010
Ulrich Ammann; René Vargas; Jorg Roth-Stielow
The variable switching frequency seen at the switches of Direct Model Predictive Control (DMPC) converters with a discrete-time implementation of sampling, prediction and switching is a major concern for the practical application of this control method. This paper gives analytical explanations for the resulting local and global average switching frequency of common DC-DC and DC-AC converters based on the discrete-time DMPC operating principle. The influence of a simple strategy to reduce the average switching frequency is also analytically investigated.
Power Electronics Conference (IPEC-Hiroshima 2014 - ECCE-ASIA), 2014 International | 2014
Quoc Khanh Nguyen; Matthias Petrich; Jorg Roth-Stielow
In this paper, the problem of how to implement the MTPA/MTPV control for an energy efficient operation of a high speed Interior Permanent Magnet Synchronous Motor (IPMSM) used as traction drive is considered. This control method depends on the inductances Ld, Lq, the flux linkage ΨPM and the stator resistance Rs which might vary during operation. The parameter variation causes miscalculation of the set point currents Id and Iq for the inner current control system and thus a wrong torque will be set. Consequently the IPMSM will not be operating in the optimal operation point which yields to a reduction of the total energy efficiency and the performance. As a consequence, this paper proposes the implementation of the the Recursive Least Square Estimation (RLS) for a high speed and high performance IPMSM. With this online identification method the variable parameters are estimated and adapted to the MTPA and MTPV control strategy.
international conference on performance engineering | 2011
D. Tastekin; Quoc Khanh Nguyen; A. Lunk; Jorg Roth-Stielow
For pulsed power applications special pulsed voltage converters are needed. This paper presents an approach for a pulsed power converter, which generates bipolar output voltages up to 10 kV with extremely fast voltage slopes and high repetition rates. The topology is based on a H-bridge with a 10 kV dc-link. The output voltage and current of the pulsed voltage converter are adapted for the operation with Dielectric Barrier Discharge. To avoid the use of spark gaps due to their limited lifetime and thus to the lifetime of the converter, series stacked MOSFETs are used to realize a switch with a high blocking voltage. A balancing network for the series stacked MOSFETs is introduced as well as an adequate gate drive circuit. A matching method for the capacitive load is described, to achieve a maximum voltage slope at this capacitive load. To validate the theoretical considerations a prototype and measurements are presented.
ieee international pulsed power conference | 2011
D. Tastekin; F. Blank; A. Lunk; Jorg Roth-Stielow
A novel approach for a power supply, which generates bipolar pulsed output voltages with high repetition rates, is proposed. It is based on a solid-state Marx topology. The power supply is suitable for high-voltage repetitive pulsed power applications such as generation of Dielectric Barrier Discharges.
european conference on power electronics and applications | 2016
Matthias Zehelein; Stefan Moench; Marco Salvatore Costa; Alexander Barner; Jorg Roth-Stielow
This paper presents a control strategy for a single-phase photovoltaic inverter, using a parallel active buffer circuit. The aim is to reduce the volume demand of the necessary capacitance for filtering the twice line frequency pulsating power. The pulsating power is stored in an additional buffer capacitor, which is decoupled from the input voltage by an active buffer circuit. Therefore a high voltage swing is possible. The control concept allows an independent operation of the parallel buffer circuit from the inverter circuit.
european conference on power electronics and applications | 2016
Stefan Moench; Marco Salvatore Costa; Alexander Barner; Julian Weimer; Rainer Holz; Emilia Schwindt; Matthias Zehelein; Jorg Roth-Stielow; Ingmar Kallfass
Silicon carbide (SiC) trench MOSFET half-bridge and full-bridge power modules with hybrid integrated gate drivers on aluminium nitride (AlN) substrate were designed with electro-thermal co-simulation and soldered on an aluminium heatsink, achieving 0.3 K/W junction-to-heatsink thermal resistance. A 2 kW single-stage PV-inverter with active energy-buffer was built around the modules, achieving a weighted CEC efficiency of 95.4% and power density of 3.14 kW/l at a switching frequency of 100 kHz. The gate driver and bootstrap circuit are hybrid integrated on the power module for low parasitic gate-loop inductance. Electro-thermal co-simulation reveals a low transient temperature ripple of 6 K during the 60 Hz grid-frequency cycles at full load.
european conference on power electronics and applications | 2016
Martin Stempfle; M. Fischer; Maximilian Nitzsche; Julian Wölfle; Jorg Roth-Stielow
For drive train efficiency estimation, three-level inverters are analyzed regarding different modulation techniques and switching frequencies. In this paper an optimized operating mode selector is proposed to choose a loss optimal modulation technique and switching frequency for each operating point. Energy savings due to the operating mode selector are validated on a driving cycle.