锂离子动力电池热管理系统的研究

目前电动汽车上应用最广泛的电化学动力源是锂离子动力电池,因为其具有高比能量、长循环寿命等显著的优点。然而,电池本身的温度变化会对电池的安全性、性能、寿命等造成较大的影响。所以,本文重点介绍,在特定的环境下,研究电池温度变化的特性,并且通过电池温度合理有效的控制,利用关键技术分析,其本身就具有重要的现实意义。     

主动队列管理中的PID控制器

作为对终端系统上拥塞控制的一种补充,中间节点上的主动队列管理(AQM)策略在保证较高吞吐量的基础上有效地控制队列长度,从而实现了控制端到端的时延,保证QoS的目的。C.Hollot等人(2001)用经典控制理论中频域校正的方法设计了用于AQM的PI控制器,但参数整定上的试凑方法不免代有盲目性;算法的瞬态性能指标也不够理想。为此,该文引入了微分环节来增强系统的响应能力,同时给出了基于稳定裕度的参数整定方法,使PID控制器的稳定性有了绝对保障。仿真试验表明PID算法的调节时间远远短于PI控制器,从而为在负载瞬息万变的网络环境中实现控制分组排队等待时间的目标提供了有力的技术保障。     

Thermal management of power electronics modules packaged by a stacked-plate technique

The research presented in this paper is part of a multidisciplinary research program of the Center for Power Electronics Systems at Virginia Tech. The program supported by the Office of Naval Research focuses on the development of innovative technologies for packaging power electronics building blocks. The primary objective of this research is to improve package performance and reliability through thermal management, i.e., reducing device temperatures for a given power level. The task of thermal management involves considering trade-offs in the electrical design, package layout and geometry, materials selection and processing, manufacturing feasibility, and production cost. Based on the electrical design of a simple building block, samples of packaged modules, rated at 600 V and 3.3 kW, were fabricated using a stacked-plate technique, termed metal posts interconnected parallel plate structure (MPIPPS). The MPIPPS technique allows the power devices to be interconnected between two direct-bond copper substrates via the use of metal posts. Thermal modeling results on the MPIPPS packaged modules indicate that the new packaging technique offers a superior thermal management means for packaging power electronics modules.     

A review of passive thermal management of LED module

Recently, the high-brightness LEDs have begun to be designed for illumination application. The increased electrical currents used to drive LEDs lead to thermal issues. Thermal management for LED module is a key design parameter as high operation temperature directly affects their maximum light output, quality, reliability and life time. In this review, only passive thermal solutions used on LED module will be studied. Moreover, new thermal interface materials and passive thermal solutions applied on electronic equipments are discussed which have high potential to enhance the thermal performance of LED Module.     

火电厂基建项目调试中的安全管理研究

在科学技术的带动下,我国火电技术得到了快速的发展和完善,保证了当地的正常供电。但是从当前火电厂基建项目的实际运行来看,由于很多火电厂为了加快完成任务,不能精确统计并对火电厂运行状况进行测量,导致实际运行中产生了较多安全问题。本文主要对火电厂基建项目调试中的安全管理进行研究,希望可以给相关人员提供参考。     

电力企业营销管理系统设计研究

为了分析研究电力企业的营销管理系统设计,针对某电力企业设计了一种营销管理系统,并分析应用的具体方案及技术.结果显示在该电力企业中,应用营销管理系统之后,不仅提升企业的营销管理效率,提高70％的工作效益,企业的营销管理产生问题的几率也降低40％,具有实际的应用价值.在电力企业中,针对电力企业设计营销管理系统,不仅可以有效降低电力企业营销管理中问题的发生几率,还可以提升电力企业营销管理的工作效益,具有一定的可行性.     

A review of passive thermal management of LED module

Recently,the high-brightness LEDs have begun to be designed for illumination application.The increased electrical currents used to drive LEDs lead to thermal issues.Thermal management for LED module is a key design parameter as high operation temperature directly affects their maximum light output,quality,reliability and life time.In this review,only passive thermal solutions used on LED module will be studied.Moreover,new thermal interface materials and passive thermal solutions applied on electronic equipments are discussed which have high potential to enhance the thermal performance of LED Module.     

Optimization of wire connections design for power electronics

In automotive power electronics, low cost and reliability requirements both demand to optimize each part of the package in order to increase its life time during use. The wire bonding breakage accounts for one of the most common failures observed on power modules. In particular, the heel crack mechanism, mainly due to Joule self-heating, can occur in the module, leading to its death. Thus, the wire geometry design has to be set up to maximize its endurance. This paper presents an analytical method able to predict the optimal wire length regarding a wire displacement criterion. Finally, comparisons between experimental results and predictions of the analytical model are given.     

Advanced thermal architecture for cooling of high power electronics

This paper presents a thermal architecture concept for analysis of thermal problems and solutions existing in electronics systems. The thermal problems are categorized into a total of seven levels from chip to system. Advanced thermal technologies for addressing the thermal problems at all seven levels are discussed. Integrating the thermal architecture with the electronic architecture can significantly improve the effectiveness of the thermal management.     

Dielectric strength and thermal performance of PCB-embedded power electronics

Advantages of embedded power electronics compared to classical soldered and bonded DCB modules are smaller size, less weight, and cost savings (Hofmann et al., 2012) [1]. In addition, the low parasitic inductance provided by the embedded technology offers the potential to better utilize the maximum chip voltages and the use of fast switching semiconductors. Compared to a standard module of 15.4 nH, the measurement at the embedded module showed 2.8 nH (Neeb et al., 2014) [2].Heat-spreading in the thick copper plate inside the printed circuit board improves the thermal conductivity. At the same time, by combination with silver sintering for the die attach, higher lifetimes compared with standard DCB (direct copper bonding) assemblies may be reached.Potential risks of this new approach are lifetime limitations, and restricted dielectric strength and thermal performance of the module. In order to evaluate the embedding technology for power devices, test samples were designed and fabricated.In this study, different PCB materials were evaluated. Temperature dependent thermal conductivity of each material was measured and temperature-dependent partial discharge tests have been conducted.     

Microjet cooling devices for thermal management of electronics

This research is an effort to demonstrate the applicability of miniaturized synthetic jet (microjet) technology to the area of thermal management of microelectronic devices. Synthetic jets are jets which are formed from entrainment and expulsion of the fluid in which they are embedded. Design issues of microjet cooling devices are discussed along with characterization of excitation elements and the turbulent synthetic jets produced thereby. Geometrical parameters of the microjet cooling devices were empirically optimized with regards to cooling performance. The cooling performance of the optimized microjets was compared with previous theoretical and empirical studies of conventional jet impingement. The cooling performance of the microjet devices has been investigated in an open environment as well as in a vented and closed case environment. In such experiments, the synthetic jet impinges normal to the surface of a packaged thermal test die, comprising a heater and a diode-based temperature sensor. This test assembly allows simultaneous heat generation and temperature sensing of the package, thereby enabling assessment of the performance of the synthetic jet. Using microjet cooling devices, a thermal resistance of 30.1/spl deg/C/W has been achieved (when unforced cooling is used, thermal resistance is 59.6/spl deg/C/W) when the test chip is located at 15mm spacing from the jet exit plane. In order to more directly compare and scale the cooling results, a preliminary study on heat transfer correlations of the microjet cooling device has been performed. Finally, a comparison of the performance of the microjet cooler with standard cooling fans is given.     

智能移动终端产品热设计研究

为了解决智能移动终端局部过热的问题,从平面热布局面积入手,采用热传导技术,抓住多模智能移动终端热源器件布局的关键,给出一个考虑散热的布局最小面积;根据热流密度来计算结构的整机高度。通过热仿真来进行布局和结构设计的模拟,给出结构设计的参考意见,最后通过测试去验证和完善热设计。经过实际产品的发热红外图谱分布试验,获得智能移动产品实际的温度分布平面图,得到了与仿真一致的结论。     

Junction temperature management of IGBT module in power electronic converters

IGBT power module is the key component of the power electronic converter, but it has the lowest reliability. The junction temperature is the crucial factor which affects power module’s reliability. To some extent, the power handling capability of the converter depends on the thermal stress of the power module. Thermal management is an effective method to improve the reliability of power device, as well as enhance the power capability. For this purpose, this paper introduces the reliability design to the power converter’s traditional compensation controller design for the first time. A new concept of generalized dual-loop controller, which includes temperature control loop and electric power control loop, is proposed. The reliability and stability of the system are both considered, with the help of the hybrid controller, the power converter can operate steadily with higher reliability. The novelty of this paper is to improve the thermal control method of carrier frequency adjustment through experimental implementation during the full life cycle of the converter. The target is to control the temperature variation to be almost a constant value as well as extend the lifetime of the converter. IR sensor is used to measure the chip temperature of the unpackaged IGBT module. The temperature variation and the average temperature are all considered in thermal management, from the reliability improvement point of view. At last, the idea is digital implemented based on a varying load of power inverter system with real-time measurement of the chip’s surface temperature.     

Robust snubberless soft-switching power converter using SiC power MOSFETs and bespoke thermal design

A number of harsh-environment high-reliability applications are undergoing substantial electrification. The converters operating in such systems need to be designed to meet both stringent performance and reliability requirements. Semiconductor devices are central elements of power converters and key enablers of performance and reliability. This paper focuses on a DC–DC converter for novel avionic applications and considers both new semiconductor technologies and the application of design techniques to ensure, at the same time, that robustness is maximized and stress levels minimized. In this respect close attention is paid to the thermal management and an approach for the heatsink design aided by finite element modelling is shown.     

Degradation of thermal interface materials for high-temperature power electronics applications

The specific thermal resistance values of several thermal interface materials (TIMs) intended to thermally enhance Cu contact pairs and their degradation under isothermal ageing at 170 °C have been investigated using Cu stack samples consisting of 10 Cu discs and 9 layers of the TIMs. The results obtained indicate that the specific thermal resistance values of the as-prepared Cu stack samples, one with conductive Ag thermal grease, one with Sn–3.5Ag solder joints and one with 25 μm thick Sn foil as TIMs are significantly lower than those of the Cu stack sample without any TIM. However, after the isothermal ageing at 170 °C for 90 days, the specific thermal resistance values of the samples with these TIMs are not substantially different from those of the sample without any TIM. Also reported in this paper is an estimation of testing errors for the specific thermal resistance values, microstructure characterization of the aged samples and effect of the degradation of these TIMs on the thermal performance of a high-temperature half bridge power switch module.     

高功耗2.5D封装的热性能优化设计分析

Based on ANSYS and Icepak softwares, the numerical analysis method is used to build up the thermal analysis model of the 2.5D package, which contains a high power CPU chip. The focus of the research is on the determination of the contributing factors and their effects on the thermal resistance and heat distribution of the package. The parametric analysis illustrates that the substrate conductivity, TIM conductivity and fin height are more crucial for heat conduction in the package. Furthermore, these major parameters are compared and analyzed by orthogonal tests, and the optimal solution for 2.5D integration is proposed. The factors' influence patterns on thermal resistance, obtained in this article, could be utilized as a thermal design reference.     

Reliability-oriented environmental thermal stress analysis of fuses in power electronics

This paper investigates the thermo-mechanical stress experienced by axial lead fuses used in power electronics. Based on some experience, the approach used in this paper is pure thermal cycling, and the found failure mechanisms have been investigated through X-ray imaging. A two-step analysis, i.e. microscopic inspection and FEM thermo-mechanical simulation have been carried out based on the real geometry, including core and isolation materials, as well as the arc quenching one, which is typically quartz sand. The failure mechanism hypothesis of higher temperature variation at the end hole of the fuse element has been confirmed thanks to the analysis performed. Finally, the fatigue analysis is presented obtained by FEM-based fatigue tool.     

探讨火力发电企业ERP体系结构

作者结合实际参加了发电企业信息化建设,通过调研大量电力行业信息化建设项目和参考ERP实施相关资料的基础上对发电企业ERP特点和体系结构进行分析,最后结合火力发电企业的特点提出了发电企业ERP体系结构。     

纯电动汽车热管理系统的研究

随着世界各国对环境问题的日益重视,纯电动汽车已受到社会各界的广泛青睐,而电动汽车的发展,很大程度上受电池热管理系统、电机和电机驱动热管理系统、空调热管理系统三大系统技术成熟度的制约.本文将从结构布置和控制方式方面研究讨论,提供建议,以减少电池能耗,增加续航里程、提升整车可靠性和舒适性,希望能为EV热管理系统设计提供借鉴和参考.     

Investigations of thermal interfaces aging under thermal cycling conditions for power electronics applications

This paper presents new investigations on the aging of Thermal Interface Materials (TIMs) subjected to thermal cycling conditions. The challenge was to design a specific and original set-up in order to not only undergo avionic temperature mission profile (?50 °C/+150 °C) but also to perform standardized thermal characterization at always same conditions. Thermal conductivity is used as aging indicator. Several TIM materials (change phase, graphite and polymer based) have undergone more than 1500 of such cycles. As a result, only the phase change material thermal interface has been affected with a 30% increase of initial thermal resistance.