Module Failure Research Articles

Analysis of Blocking Capability Failure Mechanism in IGBT Module Under High Salt Spray Environment

High salt spray environment is a threat to the long-term stability and the robustness of an insulated gate bipolar transistor (IGBT) module. Failure mechanisms of IGBTs have been discussed in normal and high humidity environment, which in high salt spray environment is unclear and seldom reported. In this paper, experiments in high salt spray environment are conducted on wire-bonding IGBT modules to reveal failure mechanism. Different degradations of the blocking capability are observed for the same packaged IGBTs in the salt spray environment. Based on experiment results, degradation substances in the internal package are analyzed by means of scanning electron microscope (SEM) and X-ray diffraction (XRD) to reveal the key composition affecting the blocking capability of IGBT switches. Finally, a failure model is used to reveal the mechanism that the insulation strength of the terminal area in the chip edge is reduced by substances, resulting in the blocking failure of IGBT switches. The analysis of IGBT module failure mechanism is of great significance to reliability evaluation and optimal design for package structures of power modules applied in harsh environments.

Active Thermal Control of IGBT Modules Based on Finite-Time Boundedness.

One of the most important causes of the failure of power electronic modules is thermal stress. Proper thermal management plays an important role in more reliable and cost-effective energy conversion. In this paper, we present an advanced active thermal control (ATC) strategy to reduce a power device's thermal stress amplitude during operation, with the aim of improving the reliability and lifetime of the conversion system. A state-space model based on a Foster-type thermal model is developed to achieve junction temperature estimation in real time. A feedback controller based on finite-time boundedness (FTB) is proposed to precisely regulate the temperature in order to reduce the thermal stress according to the temperature profile. The designed controller permits the precise control of the temperature and strongly reduces the thermal stress during fast transients in the power demand. Simulation and experimental results are provided to validate the effectiveness of the proposed method.

A failure mechanism of IGBT module in MMC and improvement

In modular multi-level converter valves, as the blocked mode happens, the failure in IGBT modules often causes a chain explosion reaction, which masks the initial failure mechanism. The root cause of the failure was that the voltage, consisting of the diode forward voltage and the induced voltage on the parasitic inductance, exceeded the reverse blocking capability of the anti-parallel IGBT. The methods against the failure were studied from three aspects: decreasing the diode’s peak forward voltage, increasing the reverse blocking capability of IGBT, and minimizing the parasitic inductance of the package. It was found that the doping concentration’s effect on the diode’s peak forward voltage is not monotonic. It can be explained from the carrier density distribution during forward recovery transient that lower doping concentration reduces the carrier injection, and higher doping concentration reduces the excess carrier concentration in the doping region. Then, the influence of two buffer designs on the reverse blocking capability of IGBT was compared. It was found that a higher reverse blocking voltage would be achieved when a multi-proton implantation buffer replaced the diffused buffer. And the new design has almost no degradation in forward blocking capability.

From efficiency to eternity: A holistic review of photovoltaic panel degradation and End-of-Life management

The most dependable part of photovoltaic (PV) power systems are PV modules. Under normal operating conditions, the PV module will continue to function properly for 25 years. However, in this period, the output of the solar panel decreases significantly, which is termed “degradation,” and sometimes the panel may fail. To reduce module failure and degradation, an understanding of degradation phenomena and failure modes is crucial. With the advent of new PV technologies and increased installation capacity, the reliability and life of the modules need to be studied. This paper provides a state-of-the-art review of the most recent research on the different degradation modes of PV modules. Globally, PV waste is projected to make up 4 %–14 % of total generation capacity by 2030 and more than 80 % by 2050 due to a 25-year average panel lifespan. Therefore, PV panel disposal will be a significant environmental concern. Therefore, this review contains information on the current state of recycling PV panel waste, the various technologies involved in recycling, and the financial implications of recycling.

Exhaustive Test Case Generation for Nuclear Safety Software Based on the Software Logic Model

An issue regarding the incorporation of software reliability within the nuclear power plant (NPP) probabilistic risk assessment model has emerged in the licensing processes of digitalized NPPs. Since software failure induces common-cause failure of the processor modules, the reliability of the software used in the NPP safety-critical instrumentation and control systems must be quantified and verified with proper test cases and environments. In this study, a software testing method based on the minimal cut set (MCS)–based exhaustive test case generation scheme is proposed where the software logic model is developed from available information on the software development and the MCSs that represent the necessary and sufficient conditions for the software variables’ states to produce safety software outputs are generated. The MCSs are then converted into the test cases, which can be used as inputs to the test bed to verify that the test cases produce correct outputs after software execution. The effectiveness of the proposed method is demonstrated with the safety-critical trip logic software of the APR-1400 reactor protection system. The method provides a systematic way to conduct exhaustive software testing and prove the functionality of the nuclear safety software based on the test result without uncertainties.

Performance degradation and reliability evaluation of crystalline silicon photovoltaic modules without and with considering measurement reproducibility: A case study in desert area

In this paper, performance degradation and reliability evaluation of crystalline silicon photovoltaic modules deployed in desert climate was investigated based on the more than 7-year tracking test. It is found that peak power standard deviation first increased with time, reaching the peak when modules operated for 3 years, and then continuously decreased. Then, relationship among power warranty, power degradation rate and tolerance on maximum power is revealed for the first time. If 1% of module failures during warranty period is allowable, the 30-year warranty can be realized when degradation rate is 0.4–0.6 %/year with tolerance 0 ∼ +5% and 0 ∼ +3%, or degradation rate is 0.5 %/year with tolerance ±5% and ±3%, or degradation rate is 0.4 %/year with tolerance ±10%, ±5% and ±3%. Finally, reproducibility of power measurement is introduced for more accurately evaluating module performance degradation and reliability. Meanwhile, determination procedure of reproducibility for module electrical performance is systematically set forth. It is found that power warranty period can be prolonged if reproducibility is considered. The results obtained in this paper can provide new insights into performance degradation, reliability assessment and power warranty for fielded crystalline silicon solar modules.

Attenuation of hotspot phenomenon in PV systems

ABSTRACT PV waste management is a looming problem and a growing concern for environmental engineers and energy policymakers, as the early PV installations are approaching their end-of-life. Hence, improvement of PV reliability and prevention of early failures has now become more important than ever. Notably, the formation of hotspots in PV cells under partial shading and other mismatch conditions remains a dominant cause of early failures in PV modules. In this study, we undertake an experimental investigation to assess the effectiveness of the extant bypass mechanism in preventing hotspot formation in PV modules. The findings reveal several limitations associated with the conventional bypass approach. Although the bypass diode partially fulfills its intended purpose within a string array configuration, its effectiveness is entirely compromised when connected in the configuration of real-world installations, such as in a series-parallel (SP) array. The hotspot temperature in the SP array increased up to 70.7°C under partial shading conditions at the operating point (i.e., at MPP), whereas no hotspot was created (below 46.1°C) in a string array, except in the single-cell shading scenario. To make the bypass circuits effective, in the present work, a novel bypass strategy is proposed.

Modelling SiC MOSFET module threshold voltage (VTH) and impact of parallel device ΔVTH on short circuit robustness

In SiC modules, where several power MOSFETs are connected in parallel for high current conduction capability, the issue of threshold voltage (VTH) variation between individual devices can become problematic. In instances where the standard deviation of device VTH is minimized by appropriate VTH pre-screening, non-uniform VTH shift under bias-temperature-instability can lead to increased VTH dispersion and potentially poor current sharing. Although non-destructive for normal operation, VTH dispersion in surge events like short circuits can cause premature module failure. In this paper, experimental investigations backed by theoretical models have been developed to explain the relationship between device VTH dispersion and module VTH shift. This is done for Si and SiC MOSFETs. Five Si/SiC MOSFETs are paralleled in a custom printed-circuit-board allowing individual VTH and module VTH measurements. It is shown that the module VTH is typically between the smallest VTH and the mean VTH, depending on the VTH standard deviation. Using empirical models for MOSFETs in weak inversion derived from the measured subthreshold gate transfer characteristics, the model can estimate module VTH from a dispersion of individual MOSFET VTH. It can also predict the impact of non-uniform VTH shift between constituent devices on the overall module VTH. Finally, the impact of VTH mismatch on current sharing during short circuits in parallel connected SiC MOSFETs is presented. The results show that VTH mismatch in parallel connected SiC MOSFETs reduces the short circuit withstand time from 5 μs to 4.5 μs compared to VTH matched SiC MOSFETs.

Effects of Cornices on Wind Loads of Solar Panels Mounted on Gable Roof Building

The effects of various parameters of the solar panel and surrounding structure on wind loads acting on solar panels have been extensively investigated in prior studies. However, the parameter of cornice length has not been considered. With varying lengths of cornices, solar panels can be positioned either near or far away from the roof corner and edge, which are the locations where the largest wind-induced suction forces are likely to occur. To examine the effects of cornices, a wind tunnel test was conducted to measure the wind pressures on a solar module installed on a residential gable roof building. The cornice lengths varied from 0 m to 1.6 m, with an interval of 0.4 m. The results show that when wind blows perpendicular to the roof ridge, cornice can reduce the mean, STD, and peak pressure coefficients on the upper and lower surfaces and resulting net values. However, it should be noted that the most unfavorable area-averaged minimum peaks in the middle and trailing zones exhibit a gradual increase with the growing cornice length. Considering the potential risk of solar module failure resulting from high wind-induced suction forces, more caution is needed when installing solar modules on roofs with larger cornices.

Simple Hybrid Model for Estimating Remaining Useful Life of SiC MOSFETs in Power Cycling Experiments

Recording and prediction of the accumulated damage, which will eventually lead to the failure of power electronic modules, is an aspect of high importance for power electronic systems design and, in particular, for development of Prognostic and Health Management (PHM) schemes for in-field applications. To this end, this paper presents a simple and cost-effective prognostic method for predicting the remaining useful life (RUL) of TO-247 packaged silicon carbide (SiC) metal-oxide semiconductor field-effect transistors (MOSFETs) subjected to power cycling experiments. The model assumes that the major failure mode is bond-wire lift-off and uses a damage accumulation scheme based on Paris’ crack law. The only inputs to the model are historical data on the average junction temperature swing and the temperature-compensated drain-source ON-state resistance at the peak temperature of the current cycle. Using only these two input values, the model is shown to predict RUL with surprising accuracy for the range of constant current loads determining cycling conditions under which the test data series have been acquired. This work is a first step in an ongoing project towards building more elaborate prognostic schemes for RUL-determination of SiC power MOSFETs in actual working conditions, using physics-informed neural networks (PINNs).

Метод синтеза антенной решетки со сниженным уровнем боковых лепестков при наличии отказов каналов и модулей

A method of matrix amplitude-phase synthesis of a flat antenna array with module failures according to the requirements for the envelope of the side lobes is proposed. The problem is reduced to finding the extremum of the Rayleigh ratio of two Hermitian forms, one of which takes into account the requirements for the envelope of the side lobes and is positively determined. The proposed method differs from the known ones by an iterative procedure for searching for a weight function for the formation of integral coefficients of a positive-definite Hermitian matrix of the Rayleigh relation. In the proposed method, failure accounting is carried out using two identical diagonal matrices, single values of these matrices correspond to serviceable elements, and zero – faulty ones. The condition of positive definiteness of the quadratic form, taking into account the requirements for the envelope of the side lobes, is achieved by weighing the diagonal coefficients of the matrix. As a result, when changing the structure of failures of elements and modules of the antenna array, it is not necessary to adjust the dimension of the problem. It is shown that in the presence of module failures, the level of the side lobes of the volumetric directional pattern increases significantly. At the same time, the use of conventional weight signal processing of antenna array channels with a reduced level of side lobes leads to a loss of power of the signal component at the output of the antenna array with a slight decrease in the level of side lobes. It has been found that the application of the proposed method makes it possible to achieve a noticeable decrease in the level of side lobes with controllable losses of the signal-to-noise ratio at the output of the antenna array.

Influence of interfacial interaction on the reliability of the bond between encapsulation epoxy and copper substrate

The need for power modules has been promoted by the emergence of electric vehicles. The requirements of small volume, high integrity, and high reliability for the next-generation power module lead to the change of encapsulation method from previous gel encapsulation to epoxy encapsulation. Efforts have been made to enhance epoxy materials, and commercialized high-end epoxy has shown excellent properties, but power module failures still exist. The possible reason may lie in the interfacial interaction between encapsulation epoxy and substrate, which is less noticed previously. This paper seeks to unveil the influence of interfacial interaction on the bonding reliability between encapsulation epoxy and copper substrate. Three reliability tests were performed: high-temperature storage test (HST), temperature cycling test (TCT), and pressure cooker test (PCT). The bonding strength after these reliability tests was evaluated, and the bonding interface and fracture surface were analyzed in a nanoscale. Our study discovered that interfacial interaction plays a vital role in encapsulation reliability. Copper can diffuse into the epoxy and catalyze epoxy thermal oxidative degradation, which results in bonding strength reduction after HST and PCT. The surface structure change caused by copper oxidation after HST and PCT also reduced the bonding strength. These findings will greatly benefit future power module design.

Multi-physics coupling analysis of high-power IGBT module bonding wires fault considering stray inductance of main circuit

The insulated gate bipolar transistor (IGBT) module is subjected to unbalanced electric-thermal stress for a long time due to its own turn-on and turn-off, the fluctuation of processing power and the change of external operating environment, resulting in fatigue failure. And there is a strong coupling effect between its electrical, temperature and mechanical properties. At the same time, the fatigue failure of IGBT module is also the result of multi-physical field coupling. This paper reveals the influence mechanism of main circuit stray inductance on the electric-thermal-stress coupling characteristics of high power IGBT module bonding wires fault in the context of mine-used inverter application. First, the inverter main circuit topology model considering stray inductance is constructed, and the loss value of the power chip is obtained based on extracting the busbar stray inductance and establishing the IGBT module behavior model, and the validity of the results is verified. Secondly, the package structure model of IGBT module is established and the failure analysis boundary conditions are determined, and then the joint circuit-finite element method is used to reveal the operation behavior characteristics of IGBT module under the combined action of multi-physical fields. Finally, the influence of main circuit stray inductance on the multi-physical field coupling characteristics of IGBT module and its change law are compared and analyzed under the bonding wires fault condition to study the causes of fatigue failure of IGBT module.

Analysis of Discharge Failure Mechanism of IGBT Power Modules

IGBT power modules are usually used as circuit-breaking components in power systems, and are widely used in solid-state DC circuit breakers, hybrid DC circuit breakers, all-electric aircraft, high-speed railways, new energy vehicles, and power transmission systems. In these systems, IGBT power modules are usually faced with extremely harsh working conditions and there is a failure risk. Insulation degradation should be a cause for concern as a potential path of power module failure. In this paper, the discharge phenomena of the IGBT power module were observed based on Intensified Charge Coupled Devices (ICCD), and the triple junctions composed of copper–ceramic–silicone gel inside IGBT were found as the discharge points. Furthermore, the directed bonded copper (DBC) ceramic filled with silicone gel was used as a test sample to study the discharge failure process, including the partial discharge (PD), surface charges, and electric trees. The mechanism of discharge failure is discussed and analyzed. The insulation degradation process is accompanied by phenomena such as severe partial discharge and rapid electric tree growth. This research provides support for the analysis idea and guidance of the research method for the cause of power module failure.

Effect of Solder Flux on Resistive Solder Bond Hotspot Generation in Photovoltaic Module Circuit Process and Restoration of Hotspot Module

In photovoltaic (PV) modules, resistive solder bond (RSB) hotspots are the primary cause for a reduction in output power of over 25%. They may be the result of inadequate soldering between the busbars and/or between the busbars and the interconnector ribbon during the circuit assembly procedure for the PV module. This study proposes a straightforward, dependable, and rapid method for reducing RSB hotspots in PV modules using additional solder flux during the circuit soldering process. The soldering of PV modules is examined in accordance with actual conditions present in PV module manufacturers during the manufacture of circuits. Using the tab pull test and the damp heat test, respectively, the bonding strength and dependability of the soldered connectors are evaluated. Connectors soldered with flux have a void ratio of 10% that is five times lower than connectors soldered without flux. In addition, connectors with flux decrease soldering strength by a range of −1.54% to −7.69%, whereas connectors without flux decrease soldering strength by a range of −17.39% to −29.31%. During long‐term reliability evaluations on repaired 370A and 370B samples, the RSB hotspots are substantially reduced by incorporating additional flux into the circuit process. In addition, the application of additional solder at the busbar to interconnetor ribbon soldering site prevents RSB hotspots effectively. The results are anticipated to provide comprehensive and straightforward solutions for significantly reducing RSB hotspot failures in commercial PV modules.

Experimentally derived models to detect onset of shunt resistance degradation in photovoltaic modules

It has been shown that a reduction in the shunt resistance can lead to solar module degradation over time, resulting ultimately in module failure. This paper reports how the effects of reduced shunt resistance on the current–voltage (I-V) characteristics of a PV cell can be used to identify degradation before it becomes critical. Five commercial polycrystalline solar cell samples had their shunt resistance artificially lowered before measuring their I-V characteristics. Analyses of the effect of lowered shunt resistance on maximum power output (Pmax), short-circuit current (ISC), open-circuit voltage (VOC) and fill factor were conducted. Reduction in shunt resistance was correlated with the cells’ electrical parameters to determine the critical shunt resistance where degradation becomes catastrophic. Linear models were developed relating reduction in shunt resistance to the solar cell’s Pmax and VOC. These relationships are proposed as strong predictors and observers of shunt resistance degradation and are suitable for implementation in online monitoring systems for operational PV modules.

High-Temperature Partial Discharge Characteristics of Power Module Packaging Insulation Under Square Pulse With High Dv/Dt Based on Down-Mixing Method

Partial discharge (PD) in the high voltage packaging insulation under square pulse with a high slew rate (SR or dV/dt) is one of the main causes of the power module failure, especially for wide bandgap (WBG) devices. But PD under fast square pulse at high temperatures is rarely studied and one of the critical reasons is the lack of an effective PD detection method under fast square pulses. In addition, the existing PD standard defines the PD criterion under sinusoidal alternating current (AC) situations, which is not the actual working condition of the power module. To address that, this paper proposes a down-mixing PD detection method and explores the influence of temperature on the PD characteristics of the power module packaging insulation. The results show that the partial discharge inception voltage (PDIV) decreases as the temperature increases. The PDIV under square pulse is always higher than that under AC voltage. The less the SR and the greater the pulse width (PW) of the square pulse, the lower the PDIV. Physical-based models for PDIV estimation concerning SR, PW, and temperature are proposed for industrial reference. Moreover, statistical analysis of PD magnitude, number, and occurrence phase under square pulse indicates that PD number decreases but PD magnitude increases with the increase in temperature. Higher temperature leads to PDs with large magnitudes, which may accelerate the degradation of packaging insulation.

High Efficiency Converters Based on Modular Partial Power Processing for Fully Electric Maritime Applications

This paper proposes an approach for analyzing the benefits that partial-power-processing-based converters can bring to fully electric maritime applications. With the aim of making the system modular and scalable to different powers/energies, series-connected partial power converters are proposed. Serializing these converters entails significant overvoltage issues, and this paper tackles them for one series-connected module failure case. A reliability analysis has been carried out considering that the components of the battery system follow an independent and identical distribution in terms of failure probability. Furthermore, a redundancy factor has been added to allow a certain failure rate in what is known as a fault-tolerant system. Finally, to demonstrate the high efficiency of partial power converters, a 3 kW prototype is tested at different working points that model the charging process of a battery. The experimental results show a peak efficiency of 99.36%.

Exploration of Solar Panel Damage and Service Life Reduction Using Condition Assessment, Dust Accumulation, and Material Testing

This paper presents a comprehensive inspection of a 10.044 MWp solar power plant that had operational problems. The condition assessment was necessary because the power plant was constantly producing electricity significantly below the expected peak power. The research confirmed that the cause of the decrease in performance is the pollution from the industrial park and the conventional power plant located next to the solar system. The accuracy of the results is confirmed using on-site thermal imaging at the solar power plant and laboratory tests. During the laboratory tests, the electrical performance of 1063 solar panels was examined as well as their damaging and life-reducing effect with further thermography tests. Surface dirt deposition cause several significant problems during energy generation. Power outages are a minor problem, and sustainable production is the main goal in the long term. If the failure and destruction of the solar modules cause more serious damage, the lifetime of the photovoltaic power plants can be shortened.

Software Defect Prediction Using Dagging Meta-Learner-Based Classifiers

To guarantee that software does not fail, software quality assurance (SQA) teams play a critical part in the software development procedure. As a result, prioritizing SQA activities is a crucial stage in SQA. Software defect prediction (SDP) is a procedure for recognizing high-risk software components and determining the influence of software measurements on the likelihood of software modules failure. There is a continuous need for sophisticated and better SDP models. Therefore, this study proposed the use of dagging-based and baseline classifiers to predict software defects. The efficacy of the dagging-based SDP model for forecasting software defects was examined in this study. The models employed were naïve Bayes (NB), decision tree (DT), and k-nearest neighbor (kNN), and these models were used on nine NASA datasets. Findings from the experimental results indicated the superiority of SDP models based on dagging meta-learner. Dagging-based models significantly outperformed experimented baseline classifiers built on accuracy, the area under the curve (AUC), F-measure, and precision-recall curve (PRC) values. Specifically, dagging-based NB, DT, and kNN models had +6.62%, +3.26%, and +4.14% increments in average accuracy value over baseline NB, DT, and kNN models. Therefore, it can be concluded that the dagging meta-learner can advance the recognition performances of SDP methods and should be considered for SDP processes.