Mass Balance Modeling for Electric Arc Furnace and Ladle Furnace System in Steelmaking Facility in Turkey

In the electric arc furnace （EAF） steel production processes, scrap steel is principally used as a raw material instead of iron ore. In the steelmaking process with EAF, scrap is first melted in the furnace and then the desired chemical composition of the steel can be obtained in a special furnace such as ladle furnace （LF）. This kind of furnace process is used for the secondary refining of alloy steel. LF furnace offers strong heating fluxes and enables precise temperature control, thereby allowing for the addition of desired amounts of various alloying elements. It also provides outstanding desulfurization at high-temperature treatment by reducing molten steel fluxes and removing deoxidation products. Elemental analysis with mass balance modeling is important to know the precise amount of required alloys for the LF input with respect to scrap composition. In present study, chemical reactions with mass conservation law in EAF and LF were modeled altogether as a whole system and chemical compositions of the final steel alloy output can be obtained precisely according to different scrap compositions, alloying elements ratios, and other input amounts. Besides, it was found that the mass efficiency for iron element in the system is 95.93%. These efficiencies are calculated for all input elements as 8. 45% for C, 30.31% for Si, 46.36% for Mn, 30.64% for P, 41.96% for S, and 69.79% for Cr, etc. These efficiencies provide valuable ideas about the amount of the input materials that are vanished or combusted for 100 kg of each of the input materials in the EAF and LF system.

Computer Aided Mass Balance Analysis for AC Electric Arc Furnace Steelmaking

A mass balance analysis was undertaken for liquid steel production using a computer program specially developed for the AC electric arc furnace at an important alloy steel producer in Turkey. The data obtained by using the computer program were found to be very close to the actual production ones.

Modeling of the Earth’s Planetary Heat Balance with Electrical Circuit Analogy

The integral heat model for the system of the Earth’s surface—the atmosphere—the open space based on the electrical circuit analogy is presented. Mathematical models of the heat balance for this system are proposed. Heat circuit which is analog of the electrical circuit for investigating the temperature dependencies on the key parameters in the clear form is presented.

Temperature Research of Permanent Magnet Brushless DC Motor for Electric Balanced Vehicle

A power system structure composed of a brushless DC motor and a cycloidal reducer for electric balanced vehicle has been proposed, and the temperature of important components in this structure would be discussed. The loss generated by the cycloid reducer is negligible, it’s only need to analyze the thermal field of motor. Since the temperature change will affect the material properties of the target motor, the electromagnetic and temperature fields, involved in the motor, are selected for coupling calculation to determine whether the final temperature distribution can meet the requirements of vehicle for use.

Automatic Generation Control Strategy Based on Balance of Daily Electric Energy

An automatic generation control strategy based on balance of daily total electric energy is put forward. It makes the balance between actual total generated energy controlled by automatic generation system and planned total energy on base of area control error, and makes the actual 24-hour active power load curve to approach the planned load curve. The generated energy is corrected by velocity weighting factor so that it conducts dynamic regulation and reaches the speed of response. Homologous strategy is used according to the real-time data in the operation of automatic generation control. Results of simulation are perfect and power energy compensation control with ideal effect can be achieved in the particular duration.

Balancing Thermal and Electrical Packaging Requirements for GaN Microwave and Millimeter-Wave High Power Amplifier Modules

A method for balancing thermal and electrical packaging requirements for gallium nitride (GaN) high power amplifier (HPA) modules is presented. The goal is to find a design approach that minimizes the junction temperature of the GaN so that it is reliable and has interconnects that meet electrical performance requirements. One benefit of GaN is that it can simultaneously achieve high power density and operate at microwave and millimeter-wave frequencies. However, the power density can be so high that the necessary thermal solutions can have negative impact on electrical performance. This is especially a concern for the electrical interconnects required for the input/ output ports on high power amplifier devices. This is because the signal interconnects must operate at GHz frequencies, which means that special care must be taken to avoid problems such as undesired signal coupling and ground path inductance. Therefore, this work focuses on GaN packaging and its integration into a module. The results show that an optimum thickness for the GaN heat spreader exits for thermal performance but the electrical design is impacted negatively if the optimum thermal design is chosen. Therefore, a balanced design is chosen which meets overall system level requirements.

Electrical stimulation modulates injury potentials in rats after spinal cord injury

An injury potential is the direct current potential difference between the site of spinal cord injury and the healthy nerves. Its initial amplitude is a significant indicator of the severity of spinal cord injury, and many cations, such as sodium and calcium, account for the major portion of injury potentials. This injury potential, as wel as injury current, can be modulated by direct current field stimulation;however, the appropriate parameters of the electrical field are hard to define. In this paper, injury potential is used as a parameter to adjust the intensity of electrical stimulation. Injury potential could be modulated to slightly above 0 mV （as the anode-centered group） by placing the anodes at the site of the injured spinal cord and the cathodes at the rostral and caudal sections, or around-70 mV, which is resting membrane potential （as the cathode-centered group） by reversing the polarity of electrodes in the anode-centered group. In addition, rats receiving no electrical stimulation were used as the control group. Results showed that the absolute value of the injury potentials acquired after 30 minutes of electrical stimulation was higher than the control group rats and much lower than the initial absolute value, whether the anodes or the cathodes were placed at the site of injury. This phenomenon il ustrates that by changing the polarity of the electrical field, electrical stimulation can effectively modulate the injury potentials in rats after spinal cord injury. This is also beneficial for the spontaneous repair of the cel membrane and the reduction of cation influx.

Battery Management System Used in Electric Vehicles

A battery management system(BMS) which contains state of charge(SOC) determination,battery charging control and its optimization,and cell balancing is proposed.Thevenin's model having a RC network characterizing the battery polarization is used for SOC determination.The polarization voltage of the battery model is identified using the nonlinear least square technique.The paper presents a new SOC definition method considering the SOC limit of each cell for battery pack in series.The relationship between the battery current and polarization voltage is analyzed.And then the battery charging approach that the charging current can be adaptively adjusted by the polarization voltage control system is investigated based on fuzzy logic control theory.Cell balancing control strategy is also proposed based on the principle of the maximum use for the capacity and energy of the battery pack.

2D finite element analysis of thermal balance for drained aluminum reduction cells

Based on the principle of energy conservation,the applicable technique for drained cell retrofitted from conventional one was analyzed with 2D finite element model. The model employed a 1D heat transfer scheme to compute iteratively the freeze profile until the thickness variable reached the terminating requirement. The calculated 2D heat dissipation from the cell surfaces was converted into the overall 3D heat loss. The potential drop of the system, freeze profile and heat balance were analyzed to evaluate their variation with technical parameters when designing the 150 kA conventional cell based drained cell. The simulation results show that the retrofitted drained cell is able to keep thermal balance under the conditions that the current is 190 kA, the anodic current density is 0.96 A/cm2, the anode-cathode distance is 2.5 cm, the alumina cover is 16 cm thick with a thermal conductivity of 0.20 W/(m·℃ ) and the electrolysis temperature is 946 ℃ .

Heat balance simulation of drained aluminum reduction cell

Compared with a conventional Hall Heroult cell(H H cell), the interpolar distance of a drained cell can be reduced significantly and the cell voltage and heat produced in the electrolysis will decrease greatly as well, which makes it crucial to achieve a new heat balance in the drained cell. A half anode cathode slice model of a hypothetical drained cell retrofitted from a 160 kA currently used in H H cell was developed for the thermo electric calculation and simulation. The results were presented and analyzed and possible approaches for setting up a new heat balance in a drained cell were discussed.

Unbalance Level Regulating Algorithm in Power Distribution Networks

The paper dwells on the unified power quality indexes characterizing the phenomenon of voltage unbalance in three-phase systems. Voltage unbalance is one of the commonest occurrences in the town mains of 0.38 kV voltage. The phenomenon describes as inequality of vector magnitude of phase voltage and shearing angle between them. Causes and consequences of the voltage unbalance in distribution networks have been considered. The algorithm, which allows switching one-phase load, has been developed as one of the methods of reducing the unbalance level. The algorithm is written in the function block diagram programming language. For determining the duration and magnitude of the unbalance level it is proposed to introduce the forecasting algorithm. The necessary data for forecasting are accumulated in the course of the algorithm based on the Function Block Diagram. The algorithm example is given for transforming substation of the urban electrical power supply system. The results of the economic efficiency assessment of the algorithm implementation are shown in conclusion. The use of automatic switching of the one-phase load for explored substation allows reducing energy losses (active electric energy by 7.63%;reactive energy by 8.37%). It also allows improving supply quality to a consumer. For explored substation the average zero-sequence unbalance factor has dropped from 3.59% to 2.13%, and the negative-sequence unbalance factor has dropped from 0.61% to 0.36%.

Observation of the Effect of Gait-induced Functional Electrical Stimulation on Stroke Patients with Foot Drop

Objective:To explore the effects of functional electrical stimulation and functional mid frequency electrical stimulation on lower limb function and balance function in stroke patients.Methods:20 cases of stroke patients with foot drop after admission were randomly divided into the observation group and the control group,10 cases in each group.On the basis of the two groups of patients,the observation group used the gait induced functional electrical stimulation to stimulate the peroneal nerve and the pretibial muscle in the observation group.The control group used the computer medium frequency functional electrical stimulation to stimulate the peroneal nerve and the anterior tibial muscle for 2 weeks.Before and after treatment,the lower extremity simple Fugl-Meyer scale(FMA),the Berg balance scale(BBS)and the improved Ashworth scale were evaluated respectively,and the comparative analysis was carried out in the group and between the groups.Results:After 2 weeks of treatment,the scores of FMA and BBS in the two groups were significantly higher than those before the treatment(P<0.05),and the scores of FMA and BBS in the observation group were higher than those in the control group(P<0.05),and the flexor muscle tension of the ankle plantar flexor muscle of the observed group was lower than that of the control group(P<0.05).Conclusions:Exercise therapy combined with gait induced functional electrical stimulation or computer intermediate frequency functional electrical stimulation can significantly improve lower limb function and balance function in patients with ptosis,and the therapeutic effect of functional electrical stimulation combined with gait is better.

考虑实时备用率的中长时间尺度新能源发电备用的方法

在新型电力系统中,考虑到中长期时间尺度下新能源出力具有较强规律性,提出了中长时间尺度新能源纳入备用的实时备用率的确定方法。根据实时备用率将新能源可信出力纳入备用,建立多电源电力生产模型。所建模型以生产成本最小为目标函数,考虑电源运行成本、新能源弃电成本、切负荷惩罚成本及机组出力、功率平衡、逻辑变量等约束条件。采用时间迭代将中长时间生产模拟化简为短期优化问题,利用CPLEX求解。以改进IEEE-24节点系统作为算例,优化结果表明新能源电源采用实时备用率的方法纳入备用时,电力系统生产运行总成本更低;新能源渗透率越高,纳入新能源为备用的经济效益越明显;风电和光伏独立确定备用率时,备用成本和污染排放更低。

电能-甲醇跨区协同输运下的电-氢耦合系统调度

针对我国电氢供需时空分布不均导致新能源利用率低、系统运行成本过高等问题,提出一种电能-甲醇跨区协同输运下的电-氢耦合系统调度方法。首先,根据送、受端区域的能源供需特征、电/氢子系统运行特性及甲醇氢载体属性,设计电-氢耦合系统跨区协同运行机制和调度框架,提出电能-甲醇联合输运下的送、受端供需平衡模型,充分利用甲醇的灵活储运能力促进新能源跨时空消纳;然后,构建电能-甲醇跨区协同输运下的电-氢耦合系统双层优化调度模型,考虑长时间尺度下的电、氢能量平衡,以天为调度尺度建立上层模型,确定甲醇输运和机组起停方案;考虑短时间尺度下的电力平衡、氢供需平衡约束,以小时为调度尺度建立下层模型,确定送、受端系统各小时的运行计划,从而实现异质能源的跨时空协同互补,保障送、受端区域多时间尺度能量供需平衡;最后,基于改进的HRP 38系统进行仿真分析,结果表明电能-甲醇跨区协同输运能够显著提高系统经济运行水平,促进新能源规模化消纳。

头针联合助行功能性电刺激促进脑卒中后步行及平衡功能的前瞻性研究

目的:探讨头针联合助行功能性电刺激(FES)对脑卒中患者步行及平衡功能的影响。方法:采取平行随机对照研究,纳入符合标准的脑卒中步行功能障碍患者36例,随机分为头针联合助行FES组和助行FES组,每组各18例。两组在常规康复治疗基础上,助行FES组加助行FES,头针联合助行FES组增加头针干预。训练及头针每次30min,两组干预均为1次/d,持续1周。分别在干预前、干预1周后行功能性步行能力量表(FAC)、起立-行走计时测试(TUG)、10m步行计时测试(10MWT)6min步行试验(6MWT)和平衡功能(睁、闭眼运动轨迹面积及长度)的评定并分析干预周期中不良事件的发生率。结果:(1)36例研究对象均完成了整个试验,两组干预基线情况一致(P>0.05);(2)干预前后组内对比,步行功能(TUG、10MWT、6MWT)和平衡功能(睁、闭眼运动轨迹面积和长度)均较干预前提高(P<0.05);(3)干预前后组间对比:头针联合助行FES组对平衡功能闭眼时运动轨迹面积和长度的改善优于单纯助行FES组(P<0.05),步行功能和平衡功能(睁眼状态下),两组干预前后差值对比无显著性意义(P>0.05);(4)研究中无不良事件,无脱落。结论:头针联合助行FES可以有效改善脑卒中后步行功能及平衡功能,其改善平衡功能的效果优于单纯助行FES。

头部电针结合屈伸肌交替经皮穴位电刺激治疗脑卒中偏瘫患者平衡及步行能力的临床研究

目的:观察头部电针结合屈伸肌交替经皮穴位电刺激治疗脑卒中(CVA)偏瘫患者平衡及步行能力的临床疗效。方法:将60例符合纳入标准的CVA偏瘫患者作为本试验研究对象,运用随机数字表法将患者分为常规组与联合组。两组患者均给予CVA基础治疗;常规组额外给予患肢足三里、阳陵泉、阴陵泉、三阴交、丘墟及太冲进行电针治疗;联合组额外给予百会、病灶侧运动区和双侧平衡区进行电针治疗,同时给予患肢浮郄、殷门、血海及箕门进行屈伸肌交替经皮穴位电刺激治疗。治疗前后采用5次椅子坐立测试(5-TSST)、四阶段平衡测试(4-STB)、简明平衡评价系统测试(Brief-BESTest)、功能性步态评估(FGA)、脑卒中专用生存质量量表(SS-QOL)及表面肌电信号最大肌电幅值(MAX)对患者进行疗效评估。结果:两组患者5-TSST评分治疗后降低,4-STB评分、Brief-BESTest评分、FGA评分、SS-QOL评分及表面肌电信号MAX值治疗后均升高,治疗后两组患者各项评分组间比较差异有统计学意义(P<0.01)。结论:头部电针联合屈伸肌交替经皮穴位电刺激治疗能有效改善CVA偏瘫患者的平衡及步行能力,上下协同同步刺激疗效显著,值得临床推广。

高比例新能源下电能量与平衡调节服务联合运营与出清机制

随着规模化新能源的接入,电网安全保供形势日益严峻。在此背景下,计及新能源的安全外部成本,提出了电能量与平衡调节服务的联合运营与出清机制。将电能量成本与安全外部成本耦合叠加,通过联合出清,以市场化方式精准组织平衡调节服务;以合理的价格体现电能的能量价值与安全价值,从而给出明确的价格信号促进平衡责任的分担。最后,通过算例分析,验证了所提运营机制在经济性与鲁棒性方面均具有显著优势。

基于单芯移相变压器的差动保护配置研究

移相变压器能够有效调控潮流,为保障电力系统安全可靠运行,为移相变压器配置性能优良的保护不可或缺。以某示范工程的35 kV单芯对称型移相变压器为研究对象,提出相应的本体保护方案。首先,基于基尔霍夫电流定律和电磁感应定律分析其运行特性。然后,结合其拓扑结构,设计了保护用电流互感器的安装位置,构建了电平衡差动保护和磁平衡差动保护方案。此方案可覆盖单芯移相变压器内部各绕组和绕组引线相间故障以及各绕组匝间故障。最后,基于Matlab/Simulink平台搭建单芯移相变压器模型,通过设置本体内部典型故障,验证了提出的两种差动保护配置方案的有效性。

计及多时段尺度与地域分层的多能互补系统经济调度

在考虑电热能源互联基础上,提出了计及多时段尺度与地域分层的电热多能互补系统经济调度策略,该策略从单时段和多时段角度出发,综合考虑局域级和区域级的能量平衡关系,以实现电热多能互补系统经济调度为目标。首先,在采集局域级各类能源资源数据与信息的基础上建立母线式电、热能平衡模型;然后,提出区域级能量平衡公共母线式模型,并采用小容量机组等效思想来等效聚合同类型机组;其次,建立典型局域级电热互联能源系统模型;最后,对电热多能互补系统经济调度求解,并输出经济调度结果信息。对电热多能互补系统的经济调度的有效性与合理性通过仿真算例已经得到验证,为区域级电热多能互补系统多能互补利用、资源协调配合、经济高效运行及分析提供参考与理论指导。

德国新型储能政策及市场机制对江苏的启示

当前,新型储能成为构建新型电力系统的重要支撑手段,合理的储能政策及市场机制将会对新型储能的健康发展产生深远影响,因此有必要借鉴储能发展较好国家的先进经验。首先对德国的新能源及新型储能的规划及发展现状开展调研,从经济性、政策刺激、补贴政策等方面分析新型储能增长的内在因素,进一步研究德国储能参与电力市场机制及主要收益模式。然后分析江苏新型储能规划发展现状、市场机制、调用模式。最后对比江苏与德国储能发展的差异性,提出了可供江苏电网借鉴的新型储能发展的相关经验。