Electro-thermal Model Research Articles

Method for evaluating laser welding quality of battery module based on coupling model

Since the existing commonly used welding quality detection techniques cannot effectively detect pseudo welding (PW) defects in the laser welding of a battery module, in this study, we first study a one-dimensional heat transfer model of the PW defects of welding spot. Then, we establish an electro-thermal coupling model of a lithium-ion battery (LIB) module. The voltage of the LIB with and without PW is simulated and analyzed. The influence of charge–discharge rates, and geometric shape of welding spot on the battery voltage is discussed in detail. The simulation results show that at the discharge rates of 5 C, 10 C and 15 C, the voltage of PW battery in the discharge stage is about 12 mV, 15 mV and 20 mV lower than that of the normal one respectively. And the effect of the geometric shape of welding spot on the battery voltage is negligible. Based on experimental data of discharge stage, the complete charge–discharge data are calculated using the electro-thermal coupling model, and the voltage Euclidean distance (VED) is proposed. The experimental results prove that the laser welding quality of module can be quickly and accurately detected based on the electro-thermal coupling model and solving the VED.

Effect of passive thermal management system on the electro-thermal performance of battery module

Passive thermal management systems (BTMS) based on phase change material (PCM) have been proposed in many articles, but more attention has been paid to the temperature effect of BTMS, and the influence of BTMS on the electro-thermal performance of battery module has rarely been studied. Therefore, composite PCM composed of lauric acid, expand graphite (EG) and graphene (GR) with a mass ratio of 8:1.5:0.5 is prepared and used for temperature control of Li-ion battery. Then, a series of experiments are performed to research the performance of the thermal management module based on the cPCM, including thermal property analysis, discharge tests under standard and extreme conditions. In addition, the Gaussian process regression (GPR) model is trained and tested with internal resistance data measured over a wide temperature range, and then combined with an electro-thermal model to estimate the heat generation of batteries and further research the effect of the BTMS on discharge performance. The experimental results show that the maximum temperature (Tmax) of the batteries with cPCM is 47.41 °C, and the maximum temperature difference (ΔTmax) between the batteries is 1.46 °C in the 2C discharge process at 40 °C. The estimation results show that the heat generation of batteries with cPCM is higher than that of the batteries without cPCM under the same working conditions, and it is more sensitive to ambient temperature even without phase transition.

Comparative Characterization of NWFET and FinFET Transistor Structures Using TCAD Modeling.

A complete comparison for 14 nm FinFET and NWFET with stacked nanowires was carried out. The electrical and thermal performances in two device structures were analyzed based on TCAD simulation results. The electro-thermal TCAD models were calibrated to data measured on 30–7 nm FinFETs and NWFETs. The full set of output electrical device parameters Ion, Ioff, SS, Vth, and maximal device temperature Tmax was discussed to achieve the optimum VLSI characteristics.

Application of Analytical Modeling of Flashover Derived for Flat Samples to Polluted 11-kV SiR Insulators

This article introduces a complementary criterion for flashover (FOV) of polluted insulators based on the concept of equivalent impedance variation with discharge length and leakage current. An analytical electrothermal model enabling the calculation of critical FOV voltage and critical current of polluted insulators is developed using this complementary criterion and the equivalent impedance criterion. It is shown that the critical parameters depend on the thermal characteristic of the discharge and the components of the equivalent electrical circuit. The comparison of the computed FOV voltage and critical current is in good accordance with the experimental ones for a laboratory insulation flat sample model with different applied voltage waveforms. The application of the developed model to actual insulators destined for 11-kV systems, by including equivalent salt density deposit (ESDD) and the form factor, shows that FOV voltage values match very well with the experimental data in clean fog test conditions.

Current redistribution during inhomogeneous quench of 2G HTS tapes

Inhomogeneous temperature elevations, also called hot spots, occurring in second generation high-temperature superconductor (2G HTS) tapes may lead to their destruction. A better understanding of inhomogeneous quenches would contribute to develop strategies to better protect superconducting devices based on 2G HTS tapes against hot spots. To do so, we investigated the current redistribution around a dissipative zone in a 2G HTS tape with a combination of experiments and numerical simulations based on the finite element method (FEM). Firstly, the inhomogeneous heat generation in a commercial 2G HTS bare tape (without copper cladding) was observed through the visualization of bubble generation. Secondly, the current redistribution around a dissipative zone in commercial 2G HTS bare tapes from two different manufacturers was investigated using voltage taps on both sides of the tape. The measured voltages showed that the current redistribution around the dissipative area in the top stabilizer layer of the tape is different from that in the bottom stabilizer layer. Using a 3D electro-thermal FEM model, we reproduced these behaviors, assuming a HTS tape architecture with an inhomogeneous local critical current density. Finally, using the same FEM model, we explored the impact of a lack of silver on one lateral side of a 2G HTS tape. Our results indicate that such a lack of silver does not critically affect the quench dynamics.

Electro-thermal modelling of redox flow-batteries with electrolyte swapping for an electric ferry

Vanadium redox flow-batteries in coastal ferry applications have the potential to help bring down the carbon footprint of the shipping industry. There is a lack of research focused on vanadium redox flow-batteries in transport applications due to their low energy density, though electrolyte swapping offers benefits whereby the depleted electrolyte can be rapidly exchanged for a fully charged supply. Vanadium redox flow-batteries also benefit from significantly higher cycle life when compared to Li-ion and fuel cell technologies, offering potential for lower cost per year of ownership. A vanadium redox flow-battery coastal ferry is electro-thermally modelled to identify whether it is feasible in terms of energy capacity, temperature limits, carbon footprint and cost. The ferry journeys between two ports, where each port is equipped with a flow-battery to provide electrolyte swapping. An Equivalent Circuit Model is utilized to model the battery response, while the thermal model predicts the electrolyte temperature based on the conservation of energy. Shunt current and pumping losses are considered in the model. It was found that vanadium redox flow-batteries show real potential for the decarbonisation of the shipping industry. Battery temperature is kept within the safe operating limits, while offering a cost per voyage close to that of a diesel system, with significant reductions in CO2 output.

Data-driven early warning strategy for thermal runaway propagation in Lithium-ion battery modules with variable state of charge

Thermal runaway (TR) propagation is triggered in a battery pack by abnormalities such as a cell fire or explosion, which leads to severe consequences. Predicting the TR propagation is challenging due to the complex, high non-linearity, and uncertain disturbances of TR. This paper establishes an electro-thermal coupling simulation model of TR propagation to supplement experimental data and public datasets for model training and verification. Then, a data-driven fusion model named Multi-Mode and Multi-Task Thermal Propagation Forecasting Neural Network (MMTPFNN) is established quantitative advance multi-step prediction of TR propagation in Li-ion battery modules, and a temperature-based TR propagation grading warning strategy is proposed. The TR propagation is mainly influenced by the thermal characteristics of surrounding batteries, and the temperature distribution in the entire battery module is of great significance to the prediction of TR propagation. Herein, the model is presented by using the thermal image and the discrete operating data of cells. Furthermore, because TR is a small probability event, obtaining the thermal image of the battery module requires additional system memory and computational resources. A switching strategy of the prediction model is established to improve the applicability of the model with the temperature threshold of 60 °C. When the battery is in a safe temperature range (below 60 °C), the long short-term memory (LSTM) model is run to predict the battery temperature. Once the battery temperature is detected above 60 °C, the thermal image is captured, and the MMTPFNN model is run to predict the TR propagation. In the validation section, different network structures are discussed, and different time resolutions and different window settings of the MMTPFNN are compared. Finally, the early warning strategy with three alert levels is introduced, and the effectiveness of the warning strategy with different window settings and initial SoCs is further discussed.

Integration of Computational Fluid Dynamics and Artificial Neural Network for Optimization Design of Battery Thermal Management System

The increasing popularity of lithium-ion battery systems, particularly in electric vehicles and energy storage systems, has gained broad research interest regarding performance optimization, thermal stability, and fire safety. To enhance the battery thermal management system, a comprehensive investigation of the thermal behaviour and heat exchange process of battery systems is paramount. In this paper, a three-dimensional electro-thermal model coupled with fluid dynamics module was developed to comprehensively analyze the temperature distribution of battery packs and the heat carried away. The computational fluid dynamics (CFD) simulation results of the lumped battery model were validated and verified by considering natural ventilation speed and ambient temperature. In the artificial neural networks (ANN) model, the multilayer perceptron was applied to train the numerical outputs and optimal design of the battery setup, achieving a 1.9% decrease in maximum temperature and a 4.5% drop in temperature difference. The simulation results provide a practical compromise in optimizing the battery configuration and cooling efficiency, balancing the layout of the battery system, and safety performance. The present modelling framework demonstrates an innovative approach to utilizing high-fidelity electro-thermal/CFD numerical inputs for ANN optimization, potentially enhancing the state-of-art thermal management and reducing the risks of thermal runaway and fire outbreaks.

Circuit-Based Electrothermal Modeling of SiC Power Modules With Nonlinear Thermal Models

Silicon carbide (SiC) power devices have the potential to operate at high temperatures beyond the capabilities of silicon power devices. At increased temperatures, the temperature-dependent material properties of the SiC die and the package multilayer structure can influence the electrothermal (ET) device performance. In this article, a new step-back-correction technique implemented in a finite-difference-method-based thermal modeling tool is proposed to reduce the computational cost while maintaining a good accuracy of ET simulations for multichip power modules. The simulations take the temperature dependence of the thermal conductivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k(T)$</tex-math></inline-formula> and both conduction and switching losses into account. The importance of considering <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k(T)$</tex-math></inline-formula> for the accurate temperature prediction of SiC power devices is demonstrated for thermal impedance evaluations characterized by high-temperature swings, as well as for a 100-kHz boost converter with low device temperature amplitudes in the steady state. The proposed ET modeling is validated by COMSOL simulations and infrared camera measurements on an example of a custom-designed and custom-manufactured half-bridge SiC power module.

Data-driven modeling of the thermal dynamics of a dual-spectral ultraviolet sterilizer and control of the output irradiance

Multi-channel LED light sources possess complicated nonlinear photo-electro-thermal (PET) dynamics. Modeling such PET dynamics is challenging, but important to ensure the performance of these light sources. Traditional first-principle modeling methods that have been reported in the literature yield either single-channel LED dynamic models, or multi-channel static models. On the other hand, system identification (SID) methods have also been applied, and lead to both single-channel nonlinear dynamic models and multi-channel linear time invariant (LTI) models. However, there are still few attempts given to build multiple-input-multiple-output (MIMO) nonlinear dynamic models of multi-channel LED systems. In this work, we try to model the PET dynamics of a dual-spectral ultraviolet (UV) light source, with a structured nonlinear system identification technique, i.e., linear parameter varying (LPV) SID technique. The experimental prototype contains a 280 nm UVC channel and a 365 nm UVA channel, respectively driven by two separate constant current sources, and is hence a MIMO system. Its nonlinear electro-thermal model is first identified from experimental data by the LPV-SID method, which is then integrated with the estimated photo-electro model to form a complete PET dynamic model. The experimental results have verified that the model can accurately predict the temperature variations at two representative points on the LED board. Moreover, the identified model has been applied in designing a feedforward-feedback controller to precisely track the reference radiation levels of the two UV channels, despite the strong nonlinearity caused by both the electro-thermal dynamics and the temperature-dependent lumen efficacy.

Developing an electro-thermal model to determine heat generation and thermal properties in a lithium-ion battery

Developing an electro-thermal model to determine heat generation and thermal properties in a lithium-ion battery

A Comprehensive Electric Vehicle Model for Vehicle-to-Grid Strategy Development

A comprehensive electric vehicle model is developed to characterize the behavior of the Smart e.d. (2013) while driving, charging and providing vehicle-to-grid services. To facilitate vehicle-to-grid strategy development, the EV model is completed with the measurement of the on-board charger efficiency and the charging control behavior upon external set-point request via IEC 61851-1. The battery model is an electro-thermal model with a dual polarization equivalent circuit electrical model coupled with a lumped thermal model with active liquid cooling. The aging trend of the EV’s 50 Ah large format pouch cell with NMC chemistry is evaluated via accelerated aging tests in the laboratory. Performance of the model is validated using laboratory pack tests, charging and driving field data. The RMSE of the cell voltage was between 18.49 mV and 67.17 mV per cell for the validation profiles. Cells stored at 100% SOC and 40 °C reached end-of-life (80% of initial capacity) after 431–589 days. The end-of-life for a cell cycled with 80% DOD around an SOC of 50% is reached after 3634 equivalent full cycles which equates to a driving distance of over 420,000 km. The full parameter set of the model is provided to serve as a resource for vehicle-to-grid strategy development.

A fast forecasting model of electrothermal distribution for parallelled SiC MOSFETs

Parameter dispersion of SiC MOSFETs causes unbalanced current distribution in parallelled devices, which could increase voltage and current stresses of power devices, and lead to thermal imbalance between the devices, and thus affecting the working life and the safe operation of the converter. In order to accurately forecast the thermal balance of SiC MOSFETs, this paper investigates the problem of predicting their electrothermal models. Firstly, the operating mode of the two parallelled MOSFETs is analysed, and the influencing factors affecting the current balance are derived. Then the losses of the power devices in parallel are analysed, and the forecasting model of the electrothermal distribution is derived. Finally, the electrothermal model is verified on the experimental platform. The experimental results show that the thermal distribution are basically similar to the prediction results of the mathematical model, which largely solves the inaccuracy of forecasting model of the electrothermal distribution.

Improvement of Lithium-Ion Battery Charging From the State-of-the-Art Industrial JEITA Guidelines to a Hybrid Temperature-Regulated Current Control

This article addresses some practical issues of the Japan Electronics and Information Technology Industries Association (JEITA) battery charging guidelines and common industrial practices. The issues involve the temperature-dependent charging profile that may not lead to optimal charging time. A hybrid temperature-regulated current control (HTRCC) is proposed and compared with common JEITA charging profile in order to minimize the charging time within the thermal limits of the battery. The form factor of the charging current is used for a quick verification that HTRCC can shorten the charging time. Based on an electro-thermal battery model, the minimum charging speed improvement rate compared to JEITA charging profile is also predicted. Practical measurements of the charging profile and charging time are included to confirm the theoretical analysis.

Thermal Mitigation and Optimization Via Multitier Bond Wire Layout for IGBT Modules Considering Multicellular Electro-Thermal Effect

The stitch wire configuration is widely adopted for large-area IGBT chips. However, an inhomogeneous wire current density introduces uneven self-heating and nonuniform chip heating, which exacerbates the chip thermal stress. In this article, a multicellular electro-thermal model considering the stitch-bonding wires is derived to optimize the wire layout parameters. Furthermore, the current density alleviation of wire bonds is investigated to be the most sensitive and effective method to comprehensively mitigate the thermal nonequilibrium and local overheating. Consequently, an improved multitier layout is proposed to further achieve thermal stress suppression without any additional components and advanced materials. Finally, a triple-tier-bonded IGBT module with optimal design parameters is fabricated to validate the thermal mitigation performance. The prototype experimental results demonstrate that the modeling error is less than 3.0%. The multitier layout decreases the current density by 57.6%, hence, the maximum and average chip temperature are reduced by 21.8% and 12.4%, respectively.

3-D Physical Electro-Thermal Modeling of Nanoscale Y2O3 Memristors for Synaptic Application

Here, we report the physical electro-thermal modeling of nanoscale Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -based memristor devices. The simulation is carried out by the combined software package of COMSOL Multiphysics and MATLAB. The presented physical modeling is based on the minimization of free energy at an applied voltage. The simulated results exhibit a stable pinched hysteresis loop in resistive switching (RS) response in multiple switching cycles. The RS responses show low values of coefficient of variability ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{V}$ </tex-math></inline-formula> ), i.e., 17.36% and 17.09% in SET and RESET voltages, respectively, during cycle-to-cycle variation. The impact of voltage ramp rate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{RR}$ </tex-math></inline-formula> ) on the device characteristics such as switching response and synaptic plasticity behavior of the device is investigated. The simulated outcomes significantly depict the impact of oxide layer thickness on the switching voltages in the nanoscale device.

Electrothermal Model of a Microstrip Superconducting Detector with Photon Number Resolution

Electrothermal Model of a Microstrip Superconducting Detector with Photon Number Resolution

Accurate Electro-Thermal Computational Model Design and Validation for Inverters of Automotive Electric Drivetrain Applications

This paper proposes the fast and accurate electro-thermal model of the existing Simrod three-phase inverter for an electric vehicle (EV) application. The research focuses on analytical and dynamic electro-thermal models of inverters that can be applied for multi-applications. The optimal design approach of passive filters is presented for the DC and AC sides of the inverter. The analytical model has been established, including a mathematical representation of the inverter and induction motor (IM). The high-fidelity electro-thermal simulation model of an inverter with integrated power loss and thermal model is established. The state-space thermal model (for the IRFS4115PbF device) has been created and incorporated into the MATLAB simulation. The simulation model is then validated with the PLECS software-based thermal model to confirm the accuracy. Indirect field-oriented control (IFOC) is designed for squirrel-cage IM at a maximum power rating of 45 kW and implemented on MATLAB/Simulink. The comparative analysis between the real and simulated results is performed to validate the simulation model at a specific speed, torque, and current. Furthermore, the electro-thermal simulation model has been validated with experimental data using efficiency and temperature comparison. The developed simulation model is beneficial for designing, optimizing, and developing advanced technology-based inverters to achieve higher efficiency at a particular operating range of temperature and power quality. The new European driving cycle (NEDC) speed profile simulation results are demonstrated.

Electrothermal Modelling and Measurements of Parallel-Connected V&lt;sub&gt;TH &lt;/sub&gt;Mismatched SiC MOSFETs under Inductive Load Switching

In high current applications that use several parallel-connected SiC MOSFETs (e.g., automotive traction inverters), optimal current sharing is integral to overall system reliability. Threshold voltage (VTH) variation in SiC MOSFETs is a prevalent reliability issue that can cause current mismatch in parallel-connected devices. Using experimental measurements and compact modelling, a technique has been developed for characterising the impact of VTH variation in up to 8 parallel-connected SiC MOSFETs. This model can predict the allowable VTH variation for optimal current sharing. It can also be used to evaluate the impact of other parameters, including gate driver synchronisation, on current sharing in parallel devices.

The Development of Frequency Multipliers for Terahertz Remote Sensing System

This paper summarizes the development of novel Schottky-diode-based terahertz frequency multipliers. The basic structure and manufacturing process of planar Schottky barrier diodes (SBDs) are reviewed, along with other diode structures that have been proposed in the literature. A numerical modeling method for the novel diodes in the context of terahertz frequency multipliers is presented, which includes 3D electromagnetic (EM) modeling, electro-thermal modeling and modeling of physical non-ideal effects. Furthermore, a general design methodology for developing terahertz frequency multipliers is introduced, involving a sub-division design method (SDM), a global design method (GDM) and a half-sub-division and half-global design method (HS-HGDM). These methods are summarized and compared for 110 GHz and 220 GHz frequency multipliers in the context of communication and imaging applications. Laboratory measurements of these multipliers show good agreement with numerical simulations. Finally, several classic terahertz remote sensing systems are reviewed, and a 220 GHz remote sensing system established using novel frequency multipliers for security inspection purposes is presented along with associated imaging results.