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High-Fidelity Liquid-cooling Thermal Modeling of a WBG-based Bidirectional DC-DC Converter for Electric Drivetrains
Abstract
The advent of Wide-Bandgap (WBG) semiconductors, e.g., Silicon Carbide (SiC) and Gallium Nitride (GaN), power electronics E-drive converters are projected to obtain an increase in power density as ~2x
for SiC devices and ~4x for GaN devices, which demand detailed thermal modeling and analysis of power semiconductors and cooling systems. This paper has proposed high-fidelity (HiFi) modeling of
bidirectional DC-DC converter coupled with liquid cooling system providing detailed information with higher accuracy and less complexity to determine performance during conceptual modeling in electric vehicle drivetrain with minimum testing and development effort.
... Furthermore, the inductor's current ripple ∆ is proportional to the flux density ripple [15]. Finally, the ESR losses of the DC-link electrolytic capacitor is measured using equation (6) [16]. ...
... Based on the power loss model, analytical equations have been developed to estimate the junction-to-case temperature (Tjc), case-to-heatsink ( ) and heat sink temperature ( ) as expressed in equation (9)-(11) [16]. Hot spot temperature (Th) of the capacitor is found using equation (12). ...
... Through the application of a thermal wear-out model and the Palmgren-Miner linear damage accumulation rule[10], the effects of different loads can be combined, and the life cycle of semiconductor modules (LCsw) can be calculated as follows in equations (15) -(16). ...
As Wide Bandgap (WBG)-based semiconductors are being widely used in Electric Vehicles (EVs) drivetrains, it becomes essential to assess the reliability of the WBG-based power electronics converters (PEC). Nevertheless, the ageing response of WBG-based converters in the EVs throughout a complete mission-profile has remained a significant concern for Automotive Original Equipment Manufacturers (OEMs). This paper presents a reliability assessment of a WBG-based Interleaved Bidirectional high-voltage (HV) DC/DC Converter (IBC) for EV-drivetrains. The reliability of IBC is assessed stepwise using a standard mission-profile based on a reliability estimation toolchain that simulates the thermal wear-out of failure-prone components like the semiconductor's module and DC-link electrolytic capacitor. A modified rainflow algorithm is used to count the thermal stress, swings and expansion of the active and passive components on the IBC system. Outcomes of this article depict that the DC-link capacitor and the upper MOSFET of the half-bridge module are the most failure-prone components when the EV is driven using the dynamic WLTC mission-profile. Moreover, experimental results have presented the accuracy of the electro-thermal modelling by operating 30kW IBC prototype at different load conditions.
... The ideal switching waveforms of a semiconductor and its power losses (conduction and switching) can be seen in Figure 6. Figure 6. Electric behavior modeling, ideal conduction and switching waveforms and conduction and switching losses estimation [19]. ...
... Tj dependent Econd I dependent Econd I and Tj dependent Econd Figure 6. Electric behavior modeling, ideal conduction and switching waveforms and conduction and switching losses estimation [19]. ...
... Like the conduction power losses, the switching losses are calculated by means of the universal losses model [18][19][20][21]. The switching losses appear during the turn-on and turn-off transition of the semiconductors. ...
With the increasing demand for electric vehicles, the requirements of the market are changing ever faster. Therefore, there is a need to improve the electric car's design time, where simulations could be an appropriate tool for this task. In this paper, the modeling and simulation of an inverter for an electric vehicle are presented. Four different modeling approaches are proposed, depending on the required simulation speed and accuracy in each case. In addition, these models can provide up to 150 different electric modeling and three different thermal modeling variants. Therefore, in total, there were 450 different electrical and thermal variants. These variants are easily selectable and usable and offer different options to calculate the electrical parameters of the inverter. Finally, the speed and accuracy of the different models were compared and the obtained results presented.
... Both the simulation and experiment results in Ref. [161] indicated fewer losses and better performance of the direct heat removal structure. Afterwards, to determine the cooling performance of converters and inverters during conceptual modelling in EV, Sajib et al. [162] modelled a bidirectional DC-DC converter with high-fidelity. The inputs are the transient power losses, the flow velocity of coolant, and the coolant temperature. ...
Proton exchange membrane fuel cell (PEMFC) vehicles (PEMFCV) have drawn tremendous attention owing to the advantages of low or zero emissions. Effective integrated thermal management systems (ITMS) considering thermal loops coupling and interaction and with a rational strategy are crucial for the efficient and secure operation of PEMFCV. Therefore, ITMS in PEMFCV are worthy to be reviewed comprehensively. This paper aims to provide the general and current ideas of ITMS design in PEMFCV from part-level to system-level, along with control strategies. The factors that affect the thermal performance of heat-generating components and systems are deeply analysed, and the key findings, challenges, and future work are presented. It is found that liquid cooling is more appropriate for ITMS because of the high specific heat and the convenience of integrating other thermal systems, and that heat pumps tend to be a more suitable choice for air conditioning systems. The future work mainly includes the improvement of cooling and cold start of PEMFC, perfection and verification of waste heat recovery system, exploration of new air conditioning systems, integration of systems, coupling of ITMS and energy management systems, and enhancement of model accuracy. The provided information is useful to guide the system layout and control strategies for ITMS at the early design stage.
... None of these publications in [26]- [44], discussed converter's optimization processes with detailed modelling issues such as universal switch model, instantaneous loss profile of power device and passive components (inductor and capacitor) and liquid-cooling thermal modelling for dynamic BEV simulation. ...
Automotive Original Equipment Manufacturers (OEMs) require varying levels of functionalities and model details at different phases of the electric vehicles (EV) development process, with a trade-off between accuracy and execution time. This article proposes a scalable modelling approach depending on the multi-objective targets between model functionalities, accuracy and execution time. In this article, four different fidelity levels of modelling approaches are described based on the model functionalities, accuracy and execution time. The highest error observed between the low fidelity (LoFi) map-based model and the high fidelity (HiFi) physics-based model is 5.04%; while, the simulation time of the LoFi model is ~104 times faster than corresponding one of the HiFi model. A detailed comparison of all characteristics between multi-fidelity models is demonstrated in this paper. Furthermore, a dSPACE SCALEXIO Hardware-in-the-Loop (HiL) testbench, equipped with a minimal latency of 18μsec, is used for real-time (RT) model implementation of the EV’s HV DC/DC converter. The performance of the entire HiL setup is compared with the Model-in-the-Loop (MiL) setup and the highest RMSE is limited to 0.54 among the HiL and MiL results. Moreover, the accuracy (95.7%) of the passive component loss estimation is verified through the Finite Element Method (FEM) software model. Finally, the experimental results of a full-scale 30-kW SiC DC/DC converter prototype are presented to validate the accuracy and correlation between multi-fidelity models. It has been observed that the efficiency deviation between the hardware prototype and multi-fidelity models is less than 1.25% at full load. Furthermore, the SiC Interleaved Bidirectional Converter (IBC) prototype achieves a high efficiency of 98.4% at rated load condition.
Grid-connected Fast Charging Stations (FCS) are a vital part of the infrastructure that will enable the widespread transition to Electrical Vehicles (EVs). This work deals with the modeling of a popular grid-connected common DC bus Electric Vehicle Fast Charging Station (EVFCS), its impacts on power quality of the hosting grid, and the comparative analysis of two control strategies based on the Voltage Source Converter (VSC) that is used in this system topology. A weak electric grid connection is assumed to assess the impact on power quality. The FCS is designed to have a maximum load to charge 10 EVs. A 2-level VSC is used as the main AC-DC converter. Two control strategies—Unit Template Control (UTC) and dq-SRF (Synchronous Reference Frame)—are used for the VSC by performing steady-state and dynamic analyses. Constant Voltage-Constant Current (CC-CV) strategy is employed for the cascaded DC-DC converter. Power quality problems and their impact on the Distribution Transformer (DT) are also a focus of the study.
This article reviews the design and evaluation of different DC-DC converter topologies for Battery Electric Vehicles (BEVs) and Plug-in Hybrid Electric Vehicles (PHEVs). The design and evaluation of these converter topologies are presented, analyzed and compared in terms of output power, component count, switching frequency, electromagnetic interference (EMI), losses, effectiveness, reliability and cost. This paper also evaluates the architecture, merits and demerits of converter topologies (AC-DC and DC-DC) for Fast Charging Stations (FCHARs). On the basis of this analysis, it has found that the Multidevice Interleaved DC-DC Bidirectional Converter (MDIBC) is the most suitable topology for high-power BEVs and PHEVs (> 10kW), thanks to its low input current ripples, low output voltage ripples, low electromagnetic interference, bidirectionality, high efficiency and high reliability. In contrast, for low-power electric vehicles (<10 kW), it is tough to recommend a single candidate that is the best in all possible aspects. However, the Sinusoidal Amplitude Converter, the Z-Source DC-DC converter and the boost DC-DC converter with resonant circuit are more suitable for low-power BEVs and PHEVs because of their soft switching, noise-free operation, low switching loss and high efficiency. Finally, this paper explores the opportunity of using wide band gap semiconductors (WBGSs) in DC-DC converters for BEVs, PHEVs and converters for FCHARs. Specifically, the future roadmap of research for WBGSs, modeling of emerging topologies and design techniques of the control system for BEV and PHEV powertrains are also presented in detail, which will certainly help researchers and solution engineers of automotive industries to select the suitable converter topology to achieve the growth of projected power density.
Lifetime of PV inverters is affected by the installation sites related to different solar irradiance and ambient temperature profiles (also referred to as mission profiles). In fact, the installation site also affects the degradation rate of the PV panels, and thus long-term energy production and reliability. Prior-art lifetime analysis in PV inverters has not yet investigated the impact of PV panel degradations. This paper thus evaluates the lifetime of PV inverters considering panel degradation rates and mission profiles. Evaluations have been carried out on PV systems installed in Denmark and Arizona. The results reveal that the PV panel degradation rate has a considerable impact on the PV inverter lifetime, especially in the hot climate (e.g., Arizona), where the panel degrades at a faster rate. In that case, the PV inverter lifetime prediction can be deviated by 54%, if the impact of PV panel degradations is not taken into account.
Finite element analysis is used to examine the gap losses that occur in finely laminated nanocrystalline inductor cores under high frequency operation. The losses are seen to be concentrated in the region of the air gap and the dependence of the losses on key design parameters and operating conditions is explored. The results show that gap losses can be significant in this type of core, creating hot spots around the gap, and the losses are not accurately predicted by established design equations for low frequency laminated cores. A modified loss equation is proposed. Validation is provided by measurements on a 300 A, 60 kHz inductor.
The constant demand for higher efficiency and power density and lower costs of power electronics systems could be met by application of new topologies and/or modulation schemes and future wide-band gap semiconductor technology. However, the performance of state-of-the-art systems also could be improved significantly by multi-domain/objective optimisation, i.e. by assigning overall optimal values to the design variables in the course of the design process. In order to perform such an optimisation first a comprehensive mathematical model of the main converter circuit has to be established, including thermal component models and the measures for DM and CM EMI filtering. Based on this model, an optimisation for multiple objectives, as e.g. efficiency and power density, can be performed. The optimisation makes best use of all degrees of freedom of a design and also allows to determine the sensitivity of the system performance on base technologies like Figures of Merit of the power semiconductors or properties of the magnetic core materials. Furthermore, different topologies can be easily compared and inherent performance limits can be identified. In the paper, analytical approaches for designing the main functional elements of a power electronics converter are described and arranged to a linear design process in a first step. Moreover, the linking of the component models, i.e. of the electric, magnetic, thermal and thermo-mechanic design domains and an overall optimisation of the respective design variables based on the linked models is discussed. Finally, the coupling of the different domains and for example the utilisation of electrical equivalent circuits for implementing these couplings are investigated.
Abstract: The life time of a component is defined by the reliability demands place on it due to its operating environment and operation conditions. To evaluate the necessarily thermal / power cycle stability of a power semiconductor module in a hybrid electrical vehicle (HEV), a vehicle driving cycle profile is used to calculate the thermal reliability requirements. The calculations are based on power loss calculation, thermal modeling and a general approach of a life cycle model. This paper discusses the reliability requirements due to active and passive thermal stress on various joints such as solder or bond joints resulting by using different connections of a power module to varied cooling systems.
Keywords: Power Semiconductor Module, Hybrid Electrical Vehicle (HEV), Power Cycling (PC), Thermal Cycling (TC), Reliability.
This article presents the scalable and accurate modelling technique of a Wideband Gap-based (WBG) bidirectional DC/DC converter to achieve high efficiency while satisfying a set of design constraints. Using Si and SiC-based switches, the converter is scaled for different power ratings (10kW~50kW). Moreover, to scale the passive components of the DC/DC converter empirical design approach is developed for inductor while the systematic approach is used for capacitor selection. The accuracy (~95% accurate) of the inductor design approach is verified by the Finite Element Method (FEM) COMSOL software and accurate loss model is validated using the MATLAB tool Simulink®. The proposed study reduces 60% of core losses in comparing with a conventional silicon core, reduces 2.5% of output voltage ripples while maximum efficiency is obtained up to 98.5% at 30kW load using CAS120M12BM2 SiC MOSFET module.
The thermal behavior of power electronics devices has been a crucial design consideration, because it is closely related to the reliability and also the cost of the converter system. Unfortunately, the widely used thermal models based on lumps of thermal resistances and capacitances have their limits to correctly predict the device temperatures, especially when considering the thermal grease and heat sink attached to the power semiconductor devices. In this paper, frequency-domain approach is applied to the modeling of the thermal dynamics for power devices. The limits of the existing RC lump-based thermal networks are explained from a point of view of frequency domain. Based on the discovery, a more advanced thermal model developed in the frequency domain is proposed, which can be easily established by characterizing the slope variation from the bode diagram of the typically used Foster thermal network. The proposed model can be used to predict not only the internal temperature behaviors of the devices but also the behaviors of the heat flowing out of the devices. As a result, more correct estimation of device temperature can be achieved when considering the cooling conditions for the devices.
Numerical simulation of junction temperature time behavior in a circuit simulation is performed by setting up thermal models of power semiconductors and cooling systems, and connecting these models, typically composed of thermal RC-networks, to the calculated power losses. Calculating or estimating accurately conduction losses and, especially, switching losses has been discussed in the literature but seems to be not well known among many engineers. Therefore, in this paper we will give an overview of this topic and propose improvements of the procedure of loss-estimation in power electronic circuit simulations. The proposed scheme calculates conduction losses and switching losses with minimum effort, high accuracy and does not slow down the numerical simulation. It can be embedded directly in any circuit simulator employing ideal switches. Loss calculations are based on datasheet values and/or experimental measurements. As an example, a 5kW-inverter connected to a drive is set up with each bridge leg realized by a power module, where the characteristic parameters for the loss calculation scheme are extracted from datasheet diagrams.
Power electronics interfaces play an increasingly important
role in the future clean vehicle technologies. This paper
proposes a novel integrated power electronics interface (IPEI) for
battery electric vehicles (BEVs) in order to optimize the performance
of the powertrain. The proposed IPEI is responsible for the
power-flow management for each operating mode. In this paper, an
IPEI is proposed and designed to realize the integration of the dc/dc
converter, on-board battery charger, and dc/ac inverter together in
the BEV powertrain with high performance. The proposed concept
can improve the system efficiency and reliability, can reduce
the current and voltage ripples, and can reduce the size of the
passive and active components in the BEV drivetrains compared
to other topologies. In addition, low electromagnetic interference
and low stress in the power switching devices are expected. The
proposed topology and its control strategy are designed and analyzed
by using MATLAB/Simulink. The simulation results related
to this research are presented and discussed. Finally, the proposed
topology is experimentally validated with results obtained fromthe
prototypes that have been built and integrated in our laboratory
based on TMS320F2808 DSP.
Estimation of Liquid Cooled Heat Sink Performance at Different Operation Conditions
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Frequency-Domain Thermal Modeling and Characterization of Power Semiconductor Devices
- K Ma
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of Power Semiconductor Devices," IEEE Trans. Power Electron., vol. 31, no. 10, pp. 7183-7193, 2016.