Jan Gottschlich

A flexible test bench for power semiconductor switching loss measurements

In this paper a flexible double pulse test bench for switching loss characterization of power semiconductors is presented. It allows the characterization of switching losses for conventional power semiconductors such as IGBTs and power MOSFETs, but also for modern fast switching wide bandgap devices. Contrary to alternative test bench topologies, test voltage and current can be adjusted independently and without any changes to the test setup from zero to up to 1 kV and 1 kA, respectively. A modular design simplifies the adaption to different test scenarios and enables the usage of widely available off-the-shelf active and passive components. The topology features low energy stored in the dc link inductor and the high voltage capacitor, thus improving safety in case of a device failure.

Performance analysis of a triple-active bridge converter for interconnection of future dc-grids

Dc-dc converters are a promising technology for interconnection of future dc grids. Besides the relatively low volume and space requirements, dc-dc converters provide good controllability of the power flow. This is particularly important with regard to a more decentralized energy generation, where a fully bidirectional power flow — even between grids of equal voltage levels — is desired to increase overall grid efficiency and stability. This paper analyzes the performance of a three-phase triple-active bridge converter (3ph-TAB) which interconnects a 5 kV medium-voltage dc grid and two low-voltage dc grids with nominal voltages of 380 V and 760 V, respectively. First, the modulation strategy of the converter is described. The different cases of operation are analyzed and a method is developed which significantly simplifies the theoretical analysis of the converter. The design specifications for the leakage inductances of the transformer and the dc-link capacitors are derived and analyzed. Furthermore, the soft-switching boundaries are derived analytically. The theoretical assessment is supported by a semiconductor loss simulation for the whole operating range.

A galvanically isolated gate driver with low coupling capacitance for medium voltage SiC MOSFETs

This paper presents a galvanically isolated gate driver system for medium voltage SiC-MOSFETs. A low common mode coupling capacity of 1 pF and good electrical insulation of the gate driver power supply are achieved by using a current-loop AC-bus power supply. The power semiconductor is protected against unintentional self-turn-on by a low resistance gate path that is active while the gate driver is not powered.

A programmable gate driver for power semiconductor switching loss characterization

This paper presents a programmable gate driver unit for power semiconductors such as IGBTs and MOSFETs which allows to adjust the gate voltage and gate resistance for turn-on and turn-off of the power semiconductor independently. As properties of the gate driver have a major influence on the switching behavior of power semiconductors and thus on switching losses and EMI, it is highly desirable to characterize the influence of gate driver parameters on the switching behavior of power semiconductors experimentally. Contrary to other approaches, the presented circuit is optimized for device characterization in double pulse or similar experiments. The gate voltage range covers most gate-voltage controlled power semiconductors, including GaN and SiC MOSFETs. An internal connection of multiple output stages allows to vary the effective gate resistance over a wide range. As the gate driver parameters can be set remotely during operation, an automated characterization of the gate-driver-dependent switching behavior is enabled.

Fully digital FPGA-based current controller for switched reluctance machines

A novel fully digital FPGA-based current controller for switched reluctance machines is presented in this paper. The digital current controller provides PWM and hysteresis band modulation in a seamless way and allows complex rotor position based shaping of the phase currents to optimize torque ripple and acoustic behavior. Arbitrary phase current waveforms can be stored in a position-addressed memory. The FPGA based implementation ensures flexible scaling and adaptation to various machine designs and inverter topologies. Experimental results prove the feasibility and performance of the chosen approach.

Design and realization of a credit card size driver stage for high power thyristor based devices with integrated MOS structure

The Emitter Turn-off Thyristor (ETO) is an advantageous concept in sense of a MOS gated thyristor device. The innovative integration of the MOSFETs inside the press-pack housing allows a cable connection between the high power device and the external gate driver. After a short introduction, this paper focuses on the design and the realization of the external driver stage. Besides a mechanical and thermal decoupling of the driver from the high voltage device, the advantages are an extremely compact design in credit card dimensions. Todays IGCT solutions require typically A4 format (210 mm × 297 mm). Measurements of the prototype prove a significant lower power consumption, which stays far below 5 W at all operating conditions. Additional functionality is demonstrated by short circuit detection and handling.

Pulse generator for dynamic performance verification of current transducers

In this paper a compact low-cost current-pulse generator circuit is presented. This circuit is used to provide a reference current for the evaluation of the dynamic performance of current transducers. It is able to generate short current pulses with fast rise times of up to 1 kA/μs and variable amplitudes of up to 100 A. The functionality is demonstrated by example measurements of different current transducers.

Dynamic power control of three-phase multiport active bridge DC-DC converters for interconnection of future DC-grids

Dc grid technology is currently expanding from the high-voltage to the medium-voltage range and is expected to penetrate also low-voltage grids. For interconnection of these grids, dc-dc converters that enable a flexible and highly dynamic control of the power flow between different voltage levels are required. In the scope of this paper a highly dynamic power and current control of three-phase multiport-active bridge (3ph-MAB) converters is presented. The investigations are exemplified for a three-phase triple-active bridge (3ph-TAB) converter, i.e., a 3ph-MAB converter with three ports, which connects a medium-voltage dc grid to two separate low-voltage dc grids. Firstly, the complex relation between the power at the ports and the load angles is investigated and algorithms for on-line determination of the according load angles are derived. Secondly, the instantaneous current control (ICC), which is known from the dual-active bridge converter, is adopted for the triple-active bridge converter. Thereby, a highly dynamic current control with settling times of half a switching period is achieved. Based on these considerations, a closed-loop control structure is proposed which fully utilizes the highly dynamic behavior of the ICC. The theoretic analysis is verified by simulation for a 150 kW SiC MOSFET converter prototype with three ports and nominal port voltages of 5 kV, 380 V and 760 V.