Muhammad Nawaz

Dynamic Characterization of Parallel-Connected High-Power IGBT Modules

In high-power converter design, insulated gate bipolar transistor (IGBT) modules are often operated in parallel to reach high output currents. Evaluating the electrical and thermal behavior of the parallel IGBTs is crucial for the design and reliable operation of converter systems. This paper investigates the static and dynamic characterization of parallel IGBTs and the influence of the electrical parameters on the IGBT behavior. Si-based IGBT power modules with voltage rating of 4.5 kV and current rating of 1 kA are used for the experimental evaluation of module parallel connections. Parallel-connected modules have been driven by several commercial IGBT gate units at various dc-link voltages and current levels and with different temperatures. The tested IGBT gate units show good current sharing performance between the two parallel modules. Other important influencing factors such as busbar design layout, stray inductance variation, and gate driving are also investigated for parallel connections of IGBT modules. Finally, the switching energy of the parallel modules is extracted for IGBTs and diodes under different conditions.

Dynamic characterization of parallel-connected high-power IGBT modules

In high power converter design, IGBT modules are often operated in parallel to reach high output currents. Evaluating the electrical and thermal behaviour of the paralleling IGBTs is crucial for the design and reliable operation of converter systems. This paper investigates the static and dynamic characterization of paralleling IGBTs and the influence of the electrical parameters on the IGBT behaviour. Si based IGBT power modules with voltage rating of 4.5kV and current rating of 1 kA are used for the experimental evaluation of module parallel connections. Parallel connected modules have been driven by several commercial IGBT gate units at various DC-link voltages and current levels and with different temperatures. The tested IGBT gate units show good current sharing performance between the two parallel modules. Other important influencing factors such as busbar design layout, stray inductance variation and gate driving are also investigated for parallel connections of IGBT modules. Finally, the switching energy of the paralleling modules is extracted for IGBTs and diodes under different conditions.

Reliability assessment of SiC power MOSFETs from the end user's perspective

The reliability of commercial Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) is investigated, and comparative assessment is performed under various test environments. The MOSFETs are tested both regarding the electrical properties of the dies and the packaging properties of the devices. The results of each reliability stress are utilized not only for mutual comparison of SiC-based power commercial modules, but also as a tool to understand the underlying physical mechanisms of degradation. Towards this goal, the devices were placed under accelerate stress conditions, such as: high electric field, high temperature and high humidity. Finally, a preliminary judgment is performed on each kind of stress, based on the quality assessment of the semiconductor as well as the packaging material.

Development of Simulink-based SiC MOSFET modeling platform for series connected devices

A new MATLAB/Simulink-based modeling platform has been developed for SiC MOSFET power modules. The modeling platform describes the electrical behavior f a single 1.2 kV/ 350 A SiC MOSFET power module, as well as the series connection of two of them. A fast parameter initialization is followed by an optimization process to facilitate the extraction of the models parameters in a more automated way relying on a small number of experimental waveforms. Through extensive experimental work, it is shown that the model accurately predicts both static and dynamic performances. The series connection of two SiC power modules has been investigated through the validation of the static and dynamic conditions. Thanks to the developed model, a better understanding of the challenges introduced by uneven voltage balance sharing among series connected devices is possible.

Static and dynamic characterization of high power silicon carbide BJT modules

Silicon carbide (SiC) based power semiconductor devices are now considered as key components for future power applications where high power density, high temperature and high ruggedness against radiation are key parameters. This thanks to lower conduction and switching losses offered by the SiC devices. This paper deals with static and dynamic measurements performed for SiC based BJTs (Bipolar Junction Transistors) power modules with voltage rating 1200 V and current rating 800 A. The power modules are fabricated in flexible half bridge configuration in order to allow either full power module with 2400 V and 800 A as one power switch or by using two parallel 1200 V and 400 A half bridge legs. Results from engineering samples show overall good confidence as promised by the manufacturer for most of the transistor samples. A 40-50% reduction in the current gain was observed when temperature was increased to 475K as expected. Bipolar devices have been found out fairly stable under continuous static operation at nominal current levels.

Short-circuit ruggedness assessment of a 1.2 kV/180 A SiC MOSFET power module

While investigations on short-circuit ruggedness of discrete SiC MOSFET are widely encountered in the scientific literature, there is not so much research dealing with the operational robustness of high power SiC MOSFET modules. In this paper, the short-circuit (SC) ruggedness under hard switching fault (HSF) of a commercial 1.2 kV/180 A SiC MOSFET power module in half-bridge configuration will be presented. The test conditions, such as DC-link voltage (VDC), gate resistance (Rg) and gate-source supply voltage (VGS) are varied systematically to investigate the effect of these parameters on the peak current and short-circuit energy. The peak current of the investigated module can be as high as 2.5 kA for VGS=20 V and does not depend significantly on the gate resistors used in this research. A safe operating area (SOA) is mapped at different VGS and pulse durations and for VDS=800 V, which is typically encountered in applications for devices of these ratings. Five modules were failed in total, with a critical short-circuit energy, Ecr ranging from 7.3 J to 9.7 J. The failure mechanism is generally the thermal runaway. Prior to failure, a decrease in VGS can be observed which is an indication of an increased gate-source leakage current. The results obtained in this experimental work show a good withstand capability of the modules to SC events. The experimental data obtained during this work gives an insight into the device behavior and limitations during SC events and can be used by gate driver designers to develop protection circuits.

Development of PSpice modeling platform for 10 kV/100 A SiC MOSFET power module

This work deals with the implementation and development of a PSpice based modeling platform for 10 kV/100 A SiC MOSFET power modules. The studied SiC MOSFET power module is composed of a total of 9 dies connected in parallel with 10.0 kV blocking voltage capability. The proposed model was implemented based on the already established McNutt Hefner model originally developed for discrete single-die based SiC-MOSFETs. The proposed model has been verified both with static and dynamic experimental data and at different temperatures. Moreover, the energy loss assessment has been performed for a variety of operating parameters (e.g., stray inductance, gate resistance), different load current and supply voltages. The model was also verified with parallel connection of several power modules in order to predict the current unbalance as a result of various parasitic elements in the test circuit. The developed model has been further extended to study the electro-thermal behaviour under short circuit with accurate predictability, and validated with the experimental data. Finally, the operational robustness of the model was judged by simulating an arbitrary Buck, and Boost converter where the converter efficiency was studied with varying circuit parameters.

Comparative assessment of 3.3kV/400A SiC MOSFET and Si IGBT power modules

In this paper, a comparative evaluation between a commercial 3.3 kV/400 A Si-IGBT and a 3.3 kV/400 A SiC MOSFET power module in half-bridge configuration is presented. With a constant current of 250 A, a lower forward voltage (VDS) drop of 1.6 V is obtained for SiC MOSFET at 300 K compared to Si IGBT. At 400 A, the difference is reduced to 1.3 V. SiC MOSFET offers an on-state resistance of 8.7 mΩ, and blocking voltage of 3.5 kV at 300 K. Compared to Si-IGBT, a significant lower leakage current for the SiC MOSFET is obtained with varying temperature from 300 K to 400 K. SiC MOSFET offers 7.5 times lower switching losses compared to Si-IGBTs for a supply voltage of 2000 V at 300 K. The switching losses of the SiC MOSFET are not affected by the temperature. Total energy loss increases (3.5 times) linearly with variation of the gate resistance from 6 Ω to 27 Ω. The capability of the SiC MOSFET to withstand short-circuit (SC) events under hard switch fault condition is also investigated. The SiC MOSFET power modules survived short circuit tests performed at a DC-link voltage of 1.5 kV and a pulse duration of 3 μs with a measured short-circuit energy of 6.4 J. The SiC power module failed when the pulse duration was increased to 4 μs, where a short-circuit energy of 9.1 J was obtained. The cause of the failure is the thermal runaway leading to a drain-source short.

A temperature dependent simple spice based modeling platform for power IGBT modules

This paper deals with the development of a PSpice based temperature dependent modelling platform for the evaluation of silicon based IGBT power modules. The developed device modelling platform is intended to be used for the design and assessment of converter valves/cells for potential high power applications in transmission and distribution networks. An extended version of a previous modelling platform implemented in PSpice is presented here taking into account temperature dependence up to (and even beyond) the specified junction temperature of 125°C of 4.5kV StakPak power modules. A set of device modelling parameters (both for IGBTs and diodes) have first been extracted and verified with static and dynamic comparison of experimental data from 4.5kV and 2.0kA Si based IGBT power modules. An overall fair comparison is achieved with varying set of bus voltages and load currents and at different temperatures.

Development of a modeling platform for 4.5 kV IGBT power modules

This paper deals with the development of a PSpice based evaluation platform for high power IGBT devices. The purpose of this platform is to provide useful information for the design and the assessment of converter cells for potential high power applications. An extended version of Hefner model is presented for high power, high voltage IGBTs taking into account temperature variation. A parametric analysis is presented in order to depict the effect of each parameter in the model. A set of parameters have been extracted and then verified with static and dynamic comparison of experimental data from 4.5 kV and 2.0 kA Si based IGBT power module (StakPak). Finally, an overall energy loss estimation is presented as function of temperature, load current and collector-emitter voltage.