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关键词： Thermal effects   Ballistic transport   Drift-diffusion   Time delay   Thermoelectric transport  

摘要： With the size down and integration of power devices, the internal thermal management problem has become particularly severe. Especially in the channel region, significant heat generation can lead to a rapid increase in device temperature, which not only exacerbates the degradation of electrical performance in the channel region but also poses a severe threat to the overall reliability and stability. The drift-diffusion (D-D) transport method is employed to calculate the dynamic heat generation of n-MOSFET power devices, and the effects of size and electrical parameters on the thermal production mechanism are analyzed. Considering the quasi-ballistic effect of carrier transport in nanoscale devices, the ballistic diffusion equation (BDE) is introduced to calculate the heat transfer characteristics, and the temperature distribution is explored. The results show that, under a given input voltage, the heat accumulation due to short-channel effects becomes more pronounced with the Kn increase, forming high-temperature hotspots between the gate and drain. When the scale shrinks further ( Kn = 5 and Kn = 10), energy accumulation will occur between the gate and source, increasing temperature rise. At smaller scales, the thermal production on each side of the gate increases with the rise of the conduction voltage, especially under the working condition of Kn = 10, V g = V d = 1.0 V. Moreover, heat production and temperature transfer have a significant time delay. Specifically, it takes 15 fs for heat generation to reach a stable state, while the stable transfer of heat takes 12 ps.

关键词： 状态估计   最小二乘   潮流计算   无功补偿  

摘要： 针对如何在线实现煤矿电网功率因数提高问题,本文提出了一种实时在线提高功率因数的方法,首先,通过电网监测系统,建立实时数据库,对电网系统的运行状况进行实时跟踪。其次,在此基础上,对系统进行实时状态估计,纠正系统在线上传数据信息的错误。最后,对系统进行潮流计算,得到系统功率因数,并对功率因数不合格的节点进行无功补偿,实现功率因数的提高。通过对某一煤矿电网实例进行仿真,验证了本文提出方法的正确性。

关键词： 水肥一体机   数值分析   状态方程   灌施指令准确率   多维度融合  

摘要： 以进一步提升水肥一体机的智能性、数字性作业为目标,针对整机的灌施精准性要求展开设计。充分考虑水肥一体机的运用特点和结构组成,结合水肥的参数融合关系,建立用于水肥一体机准确控制作业的状态方程模型,设计以数值分析处理函数为核心的软件控制模块,搭建同步动作实施的硬件执行平台。展开多作物的灌施作业试验,结果表明:基于数值分析方法的水肥一体机系统架构设计合理,数值分析算法融入有效,整机试验的数值计算准确率可达98.00%以上;水肥混合均匀有度,整体管路灌施顺畅,灌施指令准确率可达99.00%以上,整机灌施效率较高,充分验证了数值分析方法应用的正确性与优越性,可以促进类似农机装备与高等数学多维度融合。

关键词： 4H-SiC   Power MOSFET   Body diode   SBD-embedded   Third quadrant   SPICE model  

摘要： Based on the measured and the TCAD simulation results, this paper provides a detailed description of the third quadrant characteristics of the Schottky barrier diode (SBD) embedded MOSFETs with different Schottky area ratios of 2.6 %, 5.3 %, and 14.7 %. As the Schottky area ratio increases, the shift of the third quadrant turn-on voltages of the MOSFETs influenced by the gate voltage decreases. The shift rates in the conventional MOSFET and SBD-embedded MOSFETs are from 57.2 % to 0 % when V gs changes from 0 V to-4 V. The shift rate becomes 0 % when the Schottky area ratio is larger than 5.3 %. Simultaneously, the TCAD simulation results and the measured results indicate that the SBD-embedded MOSFETs can effectively suppress the conduction of the low barrier diode and the body diode. Furthermore, the SPICE models were built to explain the physics mechanisms. The fitting error between the measured and fitting results is as low as 1.3 % among the models with the different Schottky area ratios.

关键词： Partial shading   Bypass diode   PV reliability   Hotspot   MOSFET   Thermal imaging  

摘要： The frequently changing environmental conditions have a substantial impact on the performance of photovoltaic (PV) systems, which makes it challenging to ensure its high-performance ratios. Mismatch of solar cells is one such factor, that leads to formation of hotspot in solar PV systems and reduces its reliability. The experimental findings presented in this article shows the inadequacy of conventional bypass circuit to protect the shaded PV module from adverse thermal impacts of small shaded areas at all operating points and for large shaded areas at maximum power point. Its performance is assessed through I-V, P-V, and bypass characteristic of the PV system for various partial shading scenarios. Previous attempts to mitigate hotspots were considered complex and costly for practical use. This article suggests a cost-effective remedy by simplifying the triggering of MOSFET based hotspot mitigation circuit. The performance of the proposed circuit is demonstrated using a 3x3 TCT connected PV array and its efficacy is confirmed via thermographic images, validating the enhanced reliability aspect. The findings reveal that the implemented solution effectively reduces the temperature of the shadowed cell(s) by up to 27.45 % when compared with conventional bypass circuit.

关键词： 鲸鱼算法   10 kV组合互感器   失真电流   电流校正   电流相位   实时功率  

摘要： 对于10 kV组合互感器而言,电流失真会使输出电流的数值水平异常增大,并且长时间不恢复至常规电流状态,从而影响互感器的正常运行。为解决上述问题,设计基于鲸鱼算法的10 kV组合互感器失真电流校正方法。构建10 kV组合互感器结构模型,完善鲸鱼算法流程,基于鲸鱼算法获取失真的电流计量数值,实现组合互感器的失真特性判定,完成基于鲸鱼算法的10 kV组合互感器失真电流校正算法的设计。实验结果表明,经过设计方法对互感器失真电流进行校正处理后,可在2 min之内将失真电流恢复至与常规电流完全相同的数值状态,校正效果较好。

关键词： STM32   功率因数校正   不间断电源   恒流充电  

摘要： 文中以STM32F103C8T6为主控芯片设计了单相在线式不间断电源。该电源由变压器、功率因数校正电路、Buck电路、Boost电路、逆变电路和储能装置等构成。市电经变压等电路以直流电对储能装置进行恒流充电,而直流电也进入逆变电路产生所需的交流电为负载供电。当市电出现停电、过压或欠压的问题时,储能装置受控接入逆变电路,实现不间断电源供电。实验测试表明,系统具有输出电压有效值平均29.99 V,频率50.00 Hz下的总谐波失真不超过2.7%,交流输入时负载调整率1.60%,电压调整率3.69%,直流输入时电源输出效率约89.90%。此外,系统可以通过按键步进设置充电电流。

关键词： 串联电抗器式   高阻抗   变压器   运行状态评估   组合赋权   模糊综合评估  

摘要： 基于准确评估串联电抗器式高阻抗变压器运行状态的目的,诊断其故障级别,构建串联电抗器式高阻抗变压器运行状态评估模型。此模型从影响变压器运行状态的电气类、油气类、油化类、物理类因素着手,构建评估指标体系后,利用基于客观修正主观的评估指标组合赋权方法,以客观修正主观的方式,为指标组合赋权;通过基于模糊综合评估的运行状态评估模型,计算全部赋权后评估指标因素隶属度,分析指标因素标准值后,计算全部指标因素评分值后,结合运行状态级别标准,判断变压器运行状态级别。结果可得,此模型对变压器运行状态级别信息评估结果准确,可得到100%一致的结果。

关键词： Inductance   Multichip modules   Three-dimensional displays   Silicon carbide   MOSFET   Layout   Performance evaluation   2.5-D packaging structure   high dynamic current sharing performance   low parasitic inductance   silicon carbide (SiC) power module  

摘要： The parasitic inductance and dynamic current sharing performances of multichip silicon carbide power module packaging limit the device's performance. Moreover, high electrical properties cannot be achieved in traditional 2-D packaging, and the 3-D packaging manufacturing process is complicated with a necessity for further reliability verification. To solve these problems, a novel 2.5-D wire-bonding packaging was designed in this article, which combines the advantages of the simple structure of 2-D packaging and the high electrical performance of 3-D packaging. Without introducing any additional substrates, a highly symmetrical 3-D commutation loop is formed solely through a distinctive layout and terminal structure. The terminal structure was optimized to achieve extremely low parasitic inductance and excellent dynamic current sharing performance considering the mutual inductance coupling. Due to the compact commutation loop, the proposed power module with a 2.5-D packaging structure could attain a parasitic inductance of 2.31 nH and balanced dynamic currents. A 1200 V/520 A 2.5-D power module was fabricated for verification. The experimental results effectively validated the low parasitic inductance and high dynamic current sharing performances.

关键词： 快速调频   储能   调频辅助服务   电力市场   频率响应  

摘要： 为应对电力系统内同步资源占比逐渐下降给系统频率安全带来的挑战，从储能参与快速调频、提高系统频率安全性的实际需求出发，基于有储能参与的电能量和备用市场出清模型展开推导。依次分析了无储能参与和有储能参与时系统的频率响应过程，确定了储能提供快速调频和二次调频的约束条件，建立了独立储能参与的电能量和备用市场、调频辅助服务市场(包含快速调频)的联合出清模型，并给出了该模型下电能量、运行备用、快速调频和二次调频的定价机制。所提模型涉及了惯量响应、快速调频、一次调频和二次调频4个阶段，反映了电力系统全阶段频率安全特性。仿真结果表明，相比无储能参与的联合出清模型，所提模型在IEEE-30和NREL-118算例下系统运行成本分别降低了约0.72%和0.47%,在提高了系统频率安全性的同时实现了系统运行成本的降低。