A Lifetime Estimation Method of MMC Submodules Based on the Combination of FEA and Physical Lifetime Model

Binyu Wang,Jianpeng Wang,Dingkun Ma,Laili Wang,Fengtao Yang,Xinying Li,Youbo Tan 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Due to a series of advantages compared with other existing power converters, modular multilevel converters (MMCs) have been widely used in the last decade. However, in some applications, such as the offshore wind power transmission, the MMC submodules (SMs) are subjected to harsh operating environment and adverse mission profiles which can easily lead to failures in the solder layers of IGBT modules. Therefore, the lifetime estimation is very important to predict the reliability of MMC. This paper studies the fundamental-frequency thermal cycles and proposes a lifetime estimation method of MMC SMs based on the combination of finite element analysis (FEA) and the physical lifetime model. This method provides a deeper physical description of the failure mechanism and considers the thermal coupling among the chips, which make the lifetime calculation more accurate. The simulation time of FE in this research is acceptable. The distribution of lifetime is presented in the form of a colorful cloud map, rather than a single number, from which we can know the most vulnerable part of the solder layers. This can help us find the appropriate measures to improve the reliability of MMC SMs. In this paper, the principle and reliability issues of MMC are first analyzed. Second, the loss of the SM is calculated through simulation and curve fitting. Then, a 3D finite element (FE) model of MMC SM is developed and the FE simulation is performed. Finally, the lifetime of the SM is obtained based on the FEA results and Morrow lifetime model.

Research on the Energy Hole Problem Based on Non-uniform Node Distribution for Wireless Sensor Networks

( Tangliu ),( Jianpeng ),( Xiao-fen Wang ),( Jin Yang ),( Bing Guo ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.9

Based on the current solutions to the problem of energy hole, this paper proposed a nonuniform node distribution clustering algorithm, NNDC. Firstly, we divide the network into rings, and then have an analysis and calculation on nodes` energy consumption in each ring of the network when clustering algorithm is applied to collect data. We also put forward a scheme of nonuniform node distribution on the basis of the proportion of nodes` energy consumption in each ring, and change nodes` active/hibernating states under density control mechanism when network coverage is guaranteed. Simulation shows NNDC algorithm can satisfyingly balance nodes` energy consumption and effectively avoid the problem of energy hole.

Boundary conditions and experimental observation of micro-explosion for water-ethanol diesel emulsified fuel droplets

( Xiaoqing Zhang ),( Tie Li ),( Jianpeng Song ),( Bin Wang ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

Droplet micro-explosion is a severe crushing phenomenon of emulsified fuel droplets during heating and evaporation. It is caused by overheating and vaporization of light components as the temperature rising to the extreme heat. Currently there are mainly two methods for solving the limit of superheat: Avedisian-Glassman kernel method and the intermolecular potential model. For the former, the nucleation rate obtained by this method is much smaller than the experimental observation, and also the surface tension for the activation energy of the molecule is not suitable for micro-size. While for the latter, it can only apply to pure liquid. Based on the Avedisian-Glassman kernel method and the intermolecular potential model, a solution for the three-component droplet micro-explosion limit of aqueous ethanol diesel emulsified fuels. Considering that the water and ethanol between the main bond energy is larger than other potential hydrogen bonding by one to two orders of magnitude, recombining the number density of molecules and the structure of molecular clusters, the hydrogen bond saturation is revised, further the activation energy of molecules can be calculated, the temperature boundary conditions for micro-explosion of water-ethanol diesel emulsified fuel droplets are obtained last. This method is not only applicable for pure liquids such as water and alcohols, but also for fuels with small liquid molecules and intermolecular potential energy with hydrogen bonds. The result of the superheat limit temperature of water under atmospheric pressure by using this method is consistent with the value of present literatures well. For more, the micro-explosion temperature boundary conditions for a kind of aqueous ethanol diesel emulsified fuel(HE30) droplet is calculated by using this method, and an observation experiment for micro-explosion is conducted to verify calculation results at last.

Experimental and Numerical Simulation Study on Mechanical Properties of Shallow Slope Root-soil Composite in Qinghai Area

Yuan Sun,Hui Li,Zhifeng Cheng,Jianpeng Dong,Yawei Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7

Natural disasters such as landslides often occur in Qinghai under the double deterioration ofearthquake and freeze-thaw cycles, ecological slope protection is an effective way to preventand control this type of disaster. In this paper, the mechanical properties of root-soilcomposites are investigated experimentally using triaxial apparatus and dynamic single shear(DSS) apparatus, and based on the discrete element method, a contact model more suitablefor reinforced soil materials is proposed to study the dynamic properties of root-soilcomposites under cyclic shear from a fine viewpoint. Based on the results of the study, thefollowing conclusions were drawn: 1) The presence of roots under the action of freeze-thawcycles increases the strength properties of the soil. At the same number of freeze-thaw cycles,the shear strength and cyclic resistance of the root-soil composites are higher than those of theloess. And the strength of the root-soil composites decreases with the increase of the numberof freeze-thaw cycles and then flattens out; 2) The proposed contact model can bettersimulate the softening effect of reinforced loess material under cyclic shear, which is moresuitable for simulating the mechanical behavior of loess and laying the foundation for furtherstudy of reinforced loess material from a fine viewpoint.; 3) The presence of the root systemwill improve the stability of the slope soil, and the root system will have a positive effect on theshear strength of the soil when the moisture content is within a certain range. The presence ofthe root system also increases the cyclic resistance of the soil. Under the same cyclic shearstress conditions, the number of damage cycles of the root-soil composites is higher than thatof the loess, the cumulative shear strain is less than that of the loess. However, the root systemno longer exerts positive effects under saturated conditions. The research results can providesome guidance for the construction of ecological slopes in loess areas, and provide a new wayto investigate the dynamic properties of root-soil composites from a fine viewpoint.

Design and properties analysis of total internal reflection gratings for pulse compressor at 1053 nm

Qunyu Bi,Jiangjun Zheng,Ailin Guo,Meizhi Sun,Jianpeng Wang,Fuling Zhang,Qingwei Yang,Xinglong Xie,Zunqi Lin 한국물리학회 2011 Current Applied Physics Vol.11 No.1

High-efficiency compression gratings based on total internal reflection (TIR) are promising alternatives of compressor gratings because of their high diffraction efficiency, potential high damage resistant ability,and compact structure. Dependence of the 1 order diffraction efficiencies on grating parameters is analyzed for TE- and TM-polarized incident light of 1053 nm at Littrow angle, which is calculated by using the rigorous coupled-wave analysis. A more intuitional view on the relation is offered through three-dimensional slicing figures instead of two-dimensional ones. The performances of high-efficiency gratings are compared and regarded as criteria for further choices, including spectral bandwidth, angle bandwidth, dispersion, and intensity distribution. For TE- and TM-irradiations, similar spectral bandwidth and angle bandwidth can be achieved by different grating parameters. However, the computer simulation result on the intensity distributions of the two polarized waves shows that such design should be used under the illumination of TE-polarized wave for lower intensity enhancement ratio,which is an important factor related to the gratings’ damage threshold.