Structural,electrical, and linear/nonlinear optical characteristics of thermally evaporated molybdenum oxide thin films

Homogeneous thin films of Molybdenum oxide (MoO₃) were grown on quartz and glass substrates using the thermal evaporation method. XRD results showed that the MoO₃ powder has a polycrystalline structure with an orthorhombic crystal system whereas the MoO₃ thin films have amorphous nature. SEM images showed that the MoO₃ thin films have a nearly uniform surfaces with worm-like shape grains. The film thickness influences on the linear and nonlinear optical characteristics of MoO₃ thin films that were examined using spectrophotometric measurements and from which, the linear optical constants of the MoO₃ thin films were estimated. The electronic transition type was determined as a direct allowed one. The values of the optical band gap were obtained to be in the range of 3.88–3.72 eV. The dispersion parameters, third-order nonlinear optical susceptibility, and the nonlinear refractive index of the MoO₃ thin films were determined and interpreted in the light of the single oscillator model. The temperature dependence of the DC electrical conductivity and the corresponding conduction mechanism for the MoO₃ films were investigated at temperatures ranging from 303 to 463 K.     

计及RSC控制的DFIG短路电流直流分量解析表达

现有文献针对计及转子变流器(RSC)控制的双馈感应风电机组(DFIG)定子短路电流解析表达,将定子磁链当作一阶直流衰减分量或忽略功率外环控制。基于DFIG电压、磁链和RSC控制方程,得到定子电流关于定子电压和定子功率的传递函数,提出定子电流的精确解析表达式。基于RSC内、外环PI参数关系,推导直流分量衰减时间常数和角频率关于PI参数的表达式。分析了RSC内外环PI参数对定子电流直流衰减分量的影响。仿真结果验证了解析表达式的准确性,为PI参数选取和保护装置测量、整定提供依据。     

直流配网型混合动力系统在车客渡船上的应用

针对车客渡船动力负荷切换频繁,传统柴油机推进油耗高、排放和噪声大的问题,提出一种基于变速发电机组和超级电容储能装置的直流配网型混合动力系统。目前系统已成功应用于“江苏路渡3011”轮,实船运行数据显示:该混合动力系统不仅能达到较好的节油效果、降低排放,更在操控性、舒适性上优于传统的柴油机推进模式。     

基于单片机C8051F500的无刷直流电机控制研究

永磁无刷直流电机是近些年发展起来的一种新型电机,具有效率高、调速性能好、启动转矩大等诸多优点,在运动控制领域中的应用日趋广泛。基于电机专用控制芯片MC33035,采用单片机C8051F500为主控芯片,设计一款无刷直流电机智能控制器,实现对无刷直流电机启动停止、正反转、调速、转速显示等控制。通过简要介绍无刷直流电机工作原理,使用MATLAB/Simulink对控制系统进行建模仿真,对无刷直流电机控制系统进行软、硬件设计。实验结果表明,该控制系统运行稳定,抗干扰性强,具有良好的市场应用价值。     

±800kV换流变压器套管电场分布三维仿真研究

为解决特高压直流套管绝缘破坏问题,分析了±800kV特高压直流套管的特性,利用Ansoft软件建立套管的三维仿真模型,计算了特高压直流套管在稳态直流、工频交流和极性反转电压下套管内部的精确场强和电位分布,并得到了在温度梯度作用下直流电压和极性反转电压下的特高压套管的电场、电位仿真结果。结果表明,直流电压下,套管的最大电位与交流电压相比,高出约37%。在法兰处,直流电压下其最大电场强度为2.07MV/m,交流电压下其最大电场强度为1.5MV/m,最大电场强度高出27.5%。靠近中心导管端部分的SF6气体中电位分布较集中。温度梯度影响下套管的硅橡胶伞裙最高场强出现在极性反转完成时第5片伞裙附近,最高场强达到1.16 MV/m。相比于常温下硅橡胶伞裙最高场强0.85 MV/m提高了36.4%,说明套管的电场强度更容易发生畸变,将导致绝缘问题的发生。研究成果可为特高压直流套管设计提供参考。     

考虑特高压和复杂接线的直流偏磁风险治理

准东—皖南特高压直流工程是世界上首个±1 100kV特高压输电工程,避免其可能造成的直流偏磁风险意义重大。为此,结合安徽电网规划情况,对接地极附近165km范围内的大地构造调研和现场实测反演得到等效的土壤模型,依据场路耦合理论建立安徽电网交流系统直流电流分布计算模型,计算各个变电站主变中性点电流,分析了直流偏磁对安徽省交流电网影响范围、影响程度及主要的影响因素,并探讨了换流站和特高压站变压器受直流偏磁的影响,针对各电压等级变电站提出直流偏磁抑制措施,制定治理原则,进一步探究综合治理方案,从而使治理效果、治理经济性达到较好的平衡。     

Refinement of primary carbides in AISI DC 53 cold work tool steel by thin section copper permanent mould casting and water atomization

In this study, as alternative methods to conventional production methods involving thin section copper permanent mould casting (fast solidification) and water atomization (rapid solidification) of AISI DC 53 cold work tool steel have been investigated. Thin slabs obtained by copper mould casting was homogenized at 1150 °C for one hour and then hot rolling was be applied. After hot rolling, conventional heat treatment have been applied to thin slabs. The same heat treatment procedure have been performed for a commercially available AISI DC 53 which is manufactured by thick section ingot casting and rolling. In order to investigate also the effect of rapid solidification on AISI DC 53 tool steel, steel powder was produced by water atomization technique. Experiments have revealed that thin steel slabs in permanent copper mould and rapidly solidified tool steel powder by water atomization have a more refined primary M₇C₃ carbides than commercially available steel.     

Effects of temperature on creepage discharge characteristics in oil-impregnated pressboard insulation under combined AC–DC voltage

Due to the complexity of the valve side winding voltage of the converter transformer, the insulation characteristics of the oil-impregnated pressboard (OIP) of the converter transformer are different from those of the traditional AC transformer. The study on effect of temperature on the creeping discharge characteristics of OIP under combined AC–DC voltage is seriously inadequate. Therefore, this paper investigates the characteristics of OIP creepage discharge under combined AC–DC voltage and discusses the influence of temperature on creepage discharge characteristics under different temperatures from 70°C to 110 °C. The experimental results show that the partial discharge inception voltage and flashover voltage decrease with increasing temperature. The times of low amplitude discharge (LAD) decrease and amplitude of LAD increases. Simultaneously, the times of high amplitude discharge (HAD) gradually increase at each stage of creepage discharge with higher temperature. The analysis indicates that the charge carriers easily accumulate and quickly migrate directional movement along the electric field ahead of discharging. The residual charge carriers are more easily dissipated after discharging. The ‘hump’ region of LAD moves to the direction of higher discharge magnitude. The interval time between two continuous discharges is shortened obviously. The concentration of HAD accelerates the development of OIP insulation creepage discharge. The temperature had an accelerating effect on the development of discharge in the OIP under applying voltage.     

基于平均功率平衡控制的磁悬浮分子泵电力失效补偿方法

高速磁悬浮涡轮分子泵（Turbo Molecular Pump, TMP）因其高能量密度、微振动、无需润滑等优点被广泛应用于工业领域，但外部电源失效时，高速转子跌落后与保护轴承产生剧烈撞击和摩擦，将给系统带来致命损害。针对以上问题，提出一种基于平均功率平衡法的电力失效补偿控制（Power Failure Compensation Control, PFCC）方法。首先，设计电机能量回馈电路；其次，对Buck-Boost变换器进行数学建模，设计一种双环非线性控制器，其中电流内环使用滑模控制，电压外环使用平均功率平衡控制（Average Power Balance Control, APBC），并利用Lyapunov函数推导出系统的稳定性条件；最后，通过搭建磁悬浮分子泵PFCC实验平台，对所提出的方法进行实验验证。结果表明：本文所提出的方法具有快速响应和输出鲁棒性，磁悬浮转子由额定转速21000 r/min降至3900 r/min时跌落，电机能量转化效率为96.6%，提高了磁轴承系统的安全性。     

A fuel-cell/battery hybrid DC backup power system via a new high step-up three port converter

In this paper, a fuel-cell (FC)/battery hybrid direct-current (DC) backup power system is proposed for high step-up applications. This system is composed of a newly developed non-isolated three-port converter, which achieves a high voltage gain by taking the advantage of a quasi Z-source network and an energy transfer capacitor. After analyzing the converter, a comprehensive comparison study and a design procedure are provided. Moreover, the controllers regulating the source power levels while smoothing the FC power profile according to the proposed energy management strategy (EMS) are designed based on the developed small-signal model of the proposed converter. Both hardware and controller design procedures are validated through the PSIM model of the whole system. As a result, it is shown that the proposed system can effectively couple FC and battery while transferring their energies to a high voltage DC bus according to the offered EMS.