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DC grid technology is regarded as a promising solution for future electric networks integrating a great amount of renewable energies. It calls for high-efficiency bidirectional dc-dc converters with a high step-up ratio to interconnect mediumvoltage dc (MVDC) distribution grids and high-voltage dc (HVDC) transmission grids. This paper focuses on dynamic performance and fault-tolerant capability of...
A method for in-situ high bandwidth junction temperature estimation of Insulated Gate Bipolar Transistors (IGBTs) is introduced. The method is based on the acquisition of the gate voltage plateau during turn-on, which can be directly related to the junction temperature. This allows fast over temperature protection of the power device and thus enables operation at the boundary of the device safe operation...
This paper presents a galvanically isolated two channel measurement system for voltage and current measurement in medium-voltage dc-dc converters with more than 1 kV operating voltage. The system uses delta-sigma modulation and signal multiplexing to transmit the digitalized signals over fiber optical cables. In combination with a current-loop power supply, high noise immunity and excellent electrical...
Supplying 25 kV, 50 Hz railway systems is a challenging task due to the load characteristics of those systems. Hence, several approaches are developed to improve their grid integration with the static frequency converter based substations. However, this supply system can be further refined by the application of a dc grid. Hence, this paper presents and discusses one possible approach to enhance the...
This paper presents different experimental methods for measuring parasitic capacitances and inductances of direct copper bond (DBC) based power semiconductor modules. The found parasitics are compared with finite element simulations to evaluate their accuracy. A very good match of the simulated and measured stray capacitances is found. The parasitics, which are found via simulations and experiments,...
The output capacitance Coss of power semiconductors is highly dependent on the drain-source voltage. In today's commercially available silicon carbide (SiC) modules an oscillation between COSS and the parasistic module inductances occurs. The battery voltage varies with the state of charge (SoC) between 250 V and 430 V. With a dc-dc converter connected to the battery, the dc-link voltage can be adjusted...
For the transmission of electricity across long distances, high voltage direct current (DC) transmission is discussed in Germany as an alternative to the currently used alternating current (AC) as it is more efficient for these distances. Changes in energy infrastructure are known to raise public awareness. However, little is known whether differences in transmission technology are relevant for the...
Modeling the terminal behavior of power system components in transient condition is of great necessity for systemlevel simulations of future DC grids. One vital component in DC grids are power electronic converters. Therefore, efficient models of power electronic converters, which model their terminal behavior, are needed for transient system-level simulations. In this paper, an approach for eliminating...
This paper topics the effect of the phase-number and the semiconductor-device selection on the volume and weight of a medium-voltage (MV) DC-DC converter intended for offshore wind turbines. In recent years, many papers have discussed the transposition from MVAC to MVDC collector grids in offshore wind, where the main motivation is to reduce losses of the system. The authors have identified that the...
In this paper, a duty-cycle control (DCC) method for a three-phase dual-active bridge (DAB3) converter with snubber capacitors is proposed to ensure the zero-voltage switching (ZVS) operation over the whole operation range. Closed-form expressions for the proposed modulation scheme are derived. Furthermore, the equivalent circuit and mathematical model of the converter commutation process are presented...
Position sensorless control of switched reluctance motors reduces the system cost and increases the drives overall reliability. The flux-linkage method is a commonly applied technique when sensorless control of switched reluctance motors is pursued. The sensing quality, though being sensitive to model errors and further effects, can be sufficient for a number of applications. However, sophisticated...
The increasingly ambitious CO2 emission regulations for internal combustion engine (ICE) vehicles prove unachievable without at least some degree of electrification of the drivetrain. Therefore, a 48 V battery solution has been adopted by the automotive industry as a transitional step towards full electrification. The low power components are still fed from the 12 V network. A bidirectional dc-dc...
In this work, a gate driver with multiple stages based on switched resistors is presented. The influence of the different stages on the turn-on and on the turn-off behaviour is investigated using experimental measurements conducted on a double pulse test bench. It is shown that, compared to a single-stage reference driver, switching loss improvements are possible while maintaining the same voltage...
To estimate the short-circuit capacity of future low-voltage DC (LVDC) grids, it is important to determine the transient and steady state short-circuit (SC) current characteristics of DC-DC converter which is an integral part of LVDC grids. The study focuses on the short-circuit behavior of Dual Active Bridge (DAB) topology of DC-DC used for integrating LVDC grid applications like photovoltaic, battery...
Wide-band-gap (WBG) semiconductor devices represent an opportunity for reaching higher power densities for power electronic converters due to higher switching speeds, and thus, a size reduction of the passive components is enabled while the total efficiency of the converter is not compromised. In this paper, four SiC-MOSFETs from CREE/Wolfspeed are compared regarding their losses and performance in...
Many publications present the extension of the soft-switching range of the dual-active bridge (DAB). Unfortunately soft-switching over the entire operating area of the DAB is hard to realize. In this paper, the loss reduction of a 5 MW dual-active bridge using the auxilary-resonant commutated pole technique are derived by simulation. The aim of this technique is to improve the converter's efficiency...
This paper discusses the design of a control strategy for a three-phase dual-active bridge (DAB3) dc-dc converter, which is employed as the central converter to track the maximum power point (MPP) of a large-scale photovoltaic (PV) farm, and to deliver the generated energy into dc distribution grids. Considering the soft-switching characteristics of the DAB3 converter, two different maximum output...
An electric motor can be overloaded shortly to produce a much higher torque than the rated value due to its inherent large thermal capacitance. The state-of-the-art overload strategies are often based on the static characteristics of the motor. The real-time thermal condition is not taken into account, which leaves certain overload potential unused. This paper presents a model predictive overload...
Switched reluctance generators (SRG) are a promising solution for back-up power generation for renewable energy or in electric vehicles. Classic approaches suggest choosing single pulse control angles to minimize dc-link rms current or excitation penalty to maximize system efficiency. Those publications only investigate the effect of turn-on angle θon and turn-off angle θoff. The influence of an additional...
The critical components in electric machines must be protected against overheating. Overheating shortens the life span of the machine and causes machine failure in extreme cases. This paper presents an online temperature estimator for an automotive switched reluctance machine based on a space-resolved lumped parameter thermal network. The losses are calculated online using a pre-measured loss map...
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