Paula Diaz Reigosa

Prediction of Bond Wire Fatigue of IGBTs in a PV Inverter Under a Long-Term Operation

Bond wire fatigue is one of the dominant failure mechanisms in IGBT modules. However, the bond wire lifetime is not easily predictable and measurable to date due to several challenges. To overcome this challenge, this paper proposes a Monte Carlo based analysis method to predict the lifetime consumption of bond wires in a Photovoltaic (PV) inverter under long-term operation. The parameter distributions of IGBTs due to manufacturing variation and the annual stress profiles due to intermittent nature of solar irradiance and ambient temperature are taken into consideration. The proposed method enables a more realistic lifetime prediction with a specified confidence level compared to the state-of-the-art approaches. A study case on IGBT modules in a 10 kW three-phase PV inverter demonstrates the procedure and the results of the analysis. Finally, the lifetime distribution of bond wires permits to estimate the risk of unreliability of a single IGBT in a Photovoltaic (PV) inverter.

A Short-Circuit Safe Operation Area Identification Criterion for SiC MOSFET Power Modules

This paper proposes a new method for the investigation of the short-circuit safe operation area (SCSOA) of state-of-the-art SiC MOSFET power modules rated at 1.2 kV based on the variations in SiC MOSFET electrical parameters (e.g., short-circuit current and gate–source voltage). According to the experimental results, two different failure mechanisms have been identified, both reducing the short-circuit capability of SiC power modules with respect to discrete SiC devices. Based on such failure mechanisms, two short-circuit safety criteria have been formulated: 1) the short-circuit-current-based criterion; and 2) the gate-voltage-based criterion. The applicability of these two criteria makes possible the SCSOA evaluation of SiC MOSFETs with some safety margins in order to avoid unnecessary failures during their SCSOA characterization. SiC MOSFET power modules from two different manufacturers are experimentally tested in order to demonstrate the procedure of the method. The obtained results can be used to have a better insight of the SCSOA of SiC MOSFETs and their physical limits.

Study on Oscillations During Short Circuit of MW-Scale IGBT Power Modules by Means of a 6-kA/1.1-kV Nondestructive Testing System

This paper uses a 6-kA/1.1-kV nondestructive testing system for the analysis of the short-circuit behavior of insulated-gate bipolar transistor (IGBT) power modules. A field-programmable gate array enables the definition of control signals to an accuracy of 10 ns. Multiple 1.7-kV/1-kA IGBT power modules displayed severe divergent oscillations, which were subsequently characterized. Experimental tests indicate that nonnegligible circuit stray inductance plays an important role in the divergent oscillations. In addition, the temperature dependence of the transconductance is proposed as an important element in triggering for the oscillations.

Prediction of bond wire fatigue of IGBTs in a PV inverter under long-term operation

Bond wire fatigue is one of the dominant failure mechanisms in insulated-gate bipolar transistor (IGBT) modules under cyclic stresses. However, there are still major challenges ahead to achieve a realistic bond wire lifetime prediction in field operation. This paper proposes a Monte Carlo based analysis method to predict the lifetime consumption of bond wires of IGBT modules in a photovoltaic (PV) inverter. The variations in IGBT parameters (e.g., on-state collector-emitter voltage), lifetime models, and environmental and operational stresses are taken into account in the lifetime prediction. The distribution of the annual lifetime consumption is estimated based on a long-term annual stress profile of solar irradiance and ambient temperature. The proposed method enables a more realistic lifetime prediction with a specified confidence level compared to the state-of-the-art approaches. A study case of IGBT modules in a 10-kW three-phase PV inverter is given to demonstrate the procedure of the method. The obtained results of the lifetime distribution can be used to justify the selection of IGBTs for the PV inverter applications and the corresponding risk of unreliability.

Mission profile based sizing of IGBT chip area for PV inverter applications

Maximizing the total energy generation is of importance for Photovoltaic (PV) plants. This paper proposes a method to optimize the IGBT chip area for PV inverters to minimize the annual energy loss of the active switches based on long-term operation conditions (i.e., mission profile). The design process is firstly introduced. Then the power loss, thermal characteristic and lifetime for IGBT modules with different chip areas are modeled. After that, the dependence of the annual energy loss and maximum junction temperature on the IGBT chip area and switching frequency is derived under a specific yearly mission profile. Simulation results are given to verify the thermal characteristics. Furthermore, a Monte Carlo based lifetime evaluation is presented to check the IGBT reliability. The proposed design method enables a reliability-oriented energy optimized sizing of active switches for PV inverter applications, which otherwise cannot be achieved by taking into account the power efficiency at rated condition or the weighted power efficiency at several loading levels only.

Modern IGBT gate driving methods for enhancing reliability of high-power converters — An overview

Abstract This paper presents a survey of existing gate driving approaches for improving reliability of Insulated Gate Bipolar Transistors (IGBTs). An extensive and various lists of techniques are introduced and discussed, including fast detection, identification and protection against IGBT failures, also considering cost-effective solutions. Gate-driver circuit solutions to improve short-circuit robustness, overload, voltage and current overshoots withstanding capability are first introduced to cope with abnormal conditions severely affecting lifetime expectation. Later, some advanced, state-of-the-art control techniques are discussed to minimize the real-mission-profile stresses in terms of voltage and current stresses to the device, together with, not least, temperature variations. Future challenges and perspectives are finally discussed at the end of the paper.

A humidity-dependent lifetime derating factor for DC film capacitors

Film capacitors are widely assumed to have superior reliability performance than Aluminum electrolytic capacitors in DC-link design of power electronic converters. However, the assumption needs to be critically judged especially for applications under high humidity environments. This paper proposes a humidity-dependent lifetime derating factor for a type of plastic-boxed metallized DC film capacitors. It overcomes the limitation that the humidity impact is not considered in the state-of-the-art DC film capacitor lifetime models. The lifetime derating factor is obtained based on a total of 8,700 hours accelerated testing of film capacitors under different humidity conditions, enabling a more justified lifetime prediction of film capacitors for DC-link applications under specific climatic environments. The analysis of the testing results and the detailed discussion on the derating factor with different lifetime definitions and confidence levels are presented.

Investigation on the short circuit safe operation area of SiC MOSFET power modules

This paper gives a better insight of the short circuit capability of state-of-the-art SiC MOSFET power modules rated at 1.2 kV by highlighting the physical limits under different operating conditions. Two different failure mechanisms have been identified, both reducing the short-circuit capability of SiC power modules in respect to discrete SiC devices. Based on such failure mechanisms, two short circuit criteria (i.e., short circuit current-based criterion and gate voltage-based criterion) are proposed in order to ensure their robustness under short-circuit conditions. A Safe Operation Area (SOA) of the studied SiC MOSFET power modules is formulated based on the two proposed criteria.

A comprehensive investigation on the short circuit performance of MW-level IGBT power modules

This paper investigates the short circuit performance of commercial 1.7 kV / 1 kA IGBT power modules by means of a 6 kA Non-Destructive-Tester. A mismatched current distribution among the parallel chips has been observed, which can reduce the short circuit capability of the IGBT power module under short circuit conditions. Further Spice simulations reveal that the stray parameters inside the module play an important role in contributing to such a phenomenon.

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.