基于MATLAB／SIMULINK动态仿真模型的高转矩软起动器研究

介绍了一种能使软起动器实现分级变频的方法 ,它能使电机以高转矩和较小起动电流平滑起动 ,且控制简单 ,成本低廉。该方法是通过改变工频电压半波的数量和顺序 ,使输出电压频率离散地增加到50Hz。本文基于MATLAB5.3/SIMULINK ,对三相交流异步电机和采用分级变频的软起动器进行建模与仿真 ,将仿真结果与传统电子软起动器进行比较 ,证明采用分级变频的软起动器可以使电机减小起动电流、增大起动转矩 ,还可使电机短时运行于低速状态     

Mathematical dynamic optimization model for electrical distribution system planning

A dynamic mixed-integer programming model is presented that has been developed to solve a distribution system expansion problem. The results of the study indicate that the computerized modelling approach is a promising tool that can provide considerable savings to the electrical utility industry in reducing not only planning man-hours but also the fixed and variable costs of distribution system operation and the final cost to the consumer.     

电力市场和节能发电调度的关系

从分析"节能发电调度"对现有电力市场交易的影响入手,阐述了两者协调运作的现实意义,并结合江苏省电力市场交易现状和节能发电调度试运行情况,设计了机组物理调度和市场金融结算并行运作的模式,建立了经济补偿的电力交易机制,阐述了节能发电调度下电力交易机制的运作全流程,分析探讨了电力市场实现电力行业节能减排的必要条件.     

Comparison of joint torque evoked with monopolar and tripolar-cuff electrodes

Using a self-sizing spiral-cuff electrode placed on the sciatic nerve of the cat, the joint torque evoked with stimulation applied to contacts in a monopolar configuration was judged to be the same as the torque evoked by stimulation applied to contacts in a tripolar configuration. Experiments were carried out in six acute cat preparations. In each experiment, a 12-contact electrode was placed on the sciatic nerve and used to effect both the monopolar and tripolar electrode configurations. The ankle torque produced by electrically evoked isometric muscle contraction was measured in three dimensions: plantar flexion, internal rotation, and inversion. Based on the recorded ankle torque, qualitative and quantitative comparisons were performed to determine if any significant difference existed in the pattern or order in which motor nerve fibers were recruited. No significant difference was found at a 98% confidence interval in either the recruitment properties or the repeatability of the monopolar and tripolar configurations. Further, isolated activation of single fascicles within the sciatic nerve was observed. Once nerve fibers in a fascicle were activated, recruitment of that fascicle was modulated over the full range before "spill-over" excitation occurred in neighboring fascicles. These results indicate that a four contact, monopolar nerve-cuff electrode is a viable substitute for a 12 contact, tripolar nerve-cuff electrode. The results of this study are also consistent with the hypothesis that multicontact self-sizing spiral-cuff electrodes can be used in motor prostheses to provide selective control of many muscles. These findings should also apply to other neuroprostheses employing-cuff electrodes on nerve trunks.     

Tremor suppression using functional electrical stimulation: a comparison between digital and analog controllers.

In this study, we compared digital and analog versions of a functional electrical stimulator designed to suppress tremor. The device was based on a closed-loop control system designed to attenuate movements in the tremor frequency range, without significantly affecting slower, voluntary movements. Testing of the digital filter was done on three patients with Parkinsonian tremor and the results compared to those of a functional electrical stimulation device based on an analog filter evaluated in a previous study. Additional testing of both the analog and digital filters was done on three subjects with no neurological impairment performing tremor-like movements and slow voluntary movements. We found that the digital controller provided a mean attenuation of 84%, compared to 65% for the analog controller.     

无刷直流电机换相转矩脉动减小及动态仿真

针对无刷直流电动机转矩脉动大的问题,提出了采用不同的PWM调制方式以及不同的重叠换相角减小换相电流所引起的转矩脉动,并运用Matlab/simulink软件对相应控制策略下的无刷直流电机进行了仿真。结果表明,增加PWM调制频率,选择合适的占空比和重叠换相角时可以使无刷直流电动机的换相转矩脉动减小。     

轴流式原型和模型水轮机的压力脉动相似性分析

本文利用RNG κ-epsilon湍流模型对轴流式原型和模型水轮机进行了全流道三维非定常湍流计算,预测原型和模型水轮机的压力脉动性能.在此基础上,本文通过对原型水轮机与模型水轮机压力脉动结果的比较,探讨两者在压力脉动性能方面可能存在的相似关系.结果表明,原型水轮机和模型水轮机的压力脉动具有相似的频率特征,但是振幅上并没有明确的相似规律可循.     

Role of ground reaction torque and other dynamic measures inpostural stability

To compare the sensitivity of different balance parameters of movement of the center of pressure (COP) and ground reaction torque (GRT) measurements, data from balance tests are presented. To examine dynamic parameters and possible quantitative interpretations, data are presented for an identical test condition (feet tandem, eyes closed) for a traumatic brain-injured patient and a norm. It is shown that the plot of the COP position during a balance test, the stabilogram, was a less sensitive measure of balance than dynamic parameters of radial velocity or GRT     

Vectorial torque control: a novel approach to torque and fluxcontrol of induction motor drives

A general approach to torque and flux control of an induction motor fed by a voltage-source inverter is described in this paper. It is independent of whether rotor or stator flux is controlled. Based on this, an algorithm can be set up which allows the generation of the inverter switching patterns as a function of the reference values, both of the electromagnetic torque and of the controlled flux. Experimental comparisons with traditional direct torque control and field-oriented control techniques confirm the possibility of achieving very high dynamic performance with the proposed strategy     

锂电池组动态热模型在混合动力汽车中的应用

锂离子电池热模型对于电池单体和热管理系统的设计有着重要的意义,研究串并联组合的锂离子电池组在混合动力汽车系统中的性能和寿命,提出面向控制的电池组动态热模型,该模型能根据电池组当前的环境温度、运行负荷、冷却强度和初始荷电状态实时估计电池组中各单体电池的运行温度。实验利用18650型锂离子电池单体,实现3并3串和3串3并形式的电池组循环充放电,得到单体电池温度分布曲线。仿真比较结果表明,提出的电池组热模型具有较高的估计精度,满足混合动力汽车的热管理系统的设计要求。     

电力需求与GDP关系的面板数据模型分析

基于面板数据模型对冀北5市电力需求与GDP之间的关系进行了分析,解决了一般模型对二维数据尤法处理的问题。通过模型形式设定检验判断不同地Ⅸ用电规模、用电结构是否存在差异,为崩电分析提供了一种新的手段。分析了模型中各方程的截距和斜率,实现了各地区特点的定量化比较。在面板数据模型中应用虚拟变量法,证明了经济周期对用电需求有显著影响。     

The relationship between cardiac contraction and intramyocardialhemodynamics

Since coronary venous flow is squeezed out from the myocardial vascular bed by the extravascular compressive force of heart muscle, the coronary venous system provides a suitable model to investigate the relationship between cardiac contraction and intramyocardial hemodynamics. To investigate coronary venous flow velocity in more detail, we previously developed a laser Doppler velocimeter (LDV) with an optical fiber. Furthermore, we have recently developed a needle probe charge-coupled device (CCD) videomicroscope to visualize intramyocardial microvessels. In this article, we report I) blood flow velocity waveforms in the epicardial small veins of the left ventricle and 2) subendocardial venular diameter changes during a cardiac cycle     

Isometric torque about the knee joint generated by microstimulation of the cat L6 spinal cord.

Isometric torque was generated about the knee joint by microstimulation of the cat L6 spinal cord using a single microelectrode. The torque responses varied with microstimulation location. Appreciable extension torque was generated by microstimulation in ventrolateral locations of the L6 spinal cord. Stimulation parameters (intensity, frequency and pulse-width) also influenced the extension torque. Specific stimulation parameters (100 microA intensity, 40 Hz frequency and 0.20 ms pulse-width) appear best suited for mapping the spinal cord based on knee joint torque responses. Low levels of cocontraction of the extensor and flexor could be achieved when extension torque was produced, but also varied with the stimulation locations. There are locations in the L6 ventral horn where microstimulation could evoke sustained extension for at least 4 min with only a slight change in torque. This study suggests the possibility of restoring lower limb function in patients with spinal cord injury above the lumbar level.     

Nonlinear dynamic load modelling: model and parameter estimation

This paper is devoted to nonlinear dynamic modelling of electric loads. A composite dynamic-static model proposed by P. Ju et.al. (see Control and Decision, vol.4, no.2, p.20-3, 1989) is further developed. This model represents both dynamic and static load characteristics. Meanwhile, it includes the effect of voltage angle on transient active power. The second contribution of this paper is to provide a parameter estimation approach using genetic algorithms. This new approach is proven to be simple yet powerful     

电力用户从发电商购电定价的双边贝叶斯动态博弈学习模型

电力用户从发电商直接购电是打破电力垄断经营过程的前奏.采用序贯博弈理论设计二者的交易机制,引入贝叶斯学习模型以提高发电商和用户的学习能力.通过发电商与电力用户的多轮报价,彼此逐轮更新对对方保留价格的认识,以更精确的预期修正报价,改进自身博弈效用,提高双方博弈过程的效率.算例表明发电商和大用户采用贝叶斯学习模型进行博弈具有有效性.     

球形Ni(OH)2XRD线谱与制备工艺的关系

研究了球形Ni(OH) 2 XRD线谱的变化对提高MH /Ni电池容量的影响。实验表明Ni(OH) 2 在制备过程中随结晶粒度的变化 ,其XRD线谱呈不同程度的选择性宽化 ,这又与反应的 pH值、氨镍比、温度、搅拌效果和添加剂有重要关系。要制备高活性球形氢氧化镍 ,必须综合考虑以上因素。     

Policy analysis model of a large electrical supply system

A simulation model of the capacity-acquisition process in a large electricity-supply system is described, and its output is compared with the actual behavior of the system. The model was built to be used in the testing and assessment of alternative capacity-acquisition policies, particularly the demand-forecasting element of such policies. A simple experiment is described that indicates that the performance of the acquisition policy is sensitive to relatively small changes in the forecasting technique employed. The value of the model in corporate planning is considered briefly.     

电子机柜的静载荷和动载荷的振动试验

本文介绍了电子机柜的静载荷和动载荷振动试验的国际(国家)标准及试验方法,并根据具体机柜试验中出现的问题,提出今后机柜设计和生产中的一些解决方法。     

审计效率与风险导向审计的关系

提高审计效率是风险导向审计模式产生的主要原因之一,在当前经济社会活动日益复杂的情况下,研究风险导向审计与审计效率之间的关系就显得十分必要。审计效率与审计风险二者之间存在相互制约的关系,影响这二者关系的重要因素主要有重要性水平、风险审计模型以及风险导向审计运行成本和运行技术等因素。通过对这些影响因素的分析,基于提高审计效率的角度,提出了相应的建议。