A NEW DISCONTINUOUS CURRENT MODEL FOR SCR DC MOTOR SPEED CONTROL SYSTEM AND CURRENT ADAPTIVE CONTROL

The paper presents a new approximative model suitable to discontinuous current and continuons current in the three-phase controlled bridge rectifier DC motor control system. This model offers a new approach for discontinuous current adaptive control.As an example of application of the model, digital simulation results of discontinuous current adaptive control in a double-closed-loop control system are presented.     

Study on constant current control of inductive power transfer with parameter identification

Aiminy at magnetic exciting current (resonant current) control, a constant current control method based on dynamic parameter identification is put forward. With energy conversion analysis, the energy storage, supply and dissipation functions of the system resonant network are constructed. The reflecting impedance identification functions are obtained by constructing the energy equilibrium relations in a period and among several periods. Furthermore, a constant current control strategy by regulating the system input voltage with Buck converter is presented. Combining the relations among system input voltage, the envelope of resonant current and the input of Buck converter, the constant current control law is proposed. The control law is verified with experiments. For the proposed method, in parameter identification, only the data of zero crossing point of resonant voltage and current are required, which reduces the complexity and costs of sampling system. Also, the constant current control law does not need complex computation and is easy to implement.     

A COMPUTER METHOD FOR COMPARISON BETWEEN EHVAC AND EHVDC TRANSMISSIONS

A computer method for comprehensive comparison between EHVAC and EHVDC is presented in this paper after analyzing the fundamental characteristics and studying the design methods of these two types of transmi-sson schemes. Some formulas are developed and an appropriate mathematical model is established. A generally applicable computer program is exploited which is acceptable to IBM-pc and its compatible micro-computers. The results of numerical practical project of the program are given to prove the correctness of the model and the program described in this paper,and it also shows that the method proposed is an efficient one with the practical values in power system planning.     

Simplified Method for Calculation of Current Distribution on Grounding Electrodes

A new method is presented to calculate the non-uniform of current distribution on grounding electrode. Based on the equivalence of low frequency current field and static electric field, the electrode is simplified to he a line charge model with limited length. The charge distribution on the model is calculated by solving equilibrant equations, and the current distribution along the axis of electrode was got. The current density at the end of electrode can he several times of that in the middle, the non-uniformity get worse with the increasing of electrode length and numbers. This is what lead to several problems on grounding systems such as inefficiency, the partial overheat and the severe corrosion of electrode.     

Theoretical analysis on the protection properties against electric shock of low voltage DC distribution system with different grounding types

The low voltage direct current(LVDC)distribution system has great potential and advantage to be applied to conventional areas, such as residential house, due to its characteristics of energy conservation and being eco-friendly, but there is no existing standard specifications to guide its application in practice to ensure the electrical safety of this system. The protection against electric shock is a key indicator of electric safety, but the effect of electric shocks on AC and DC are different. Refer to the international standard IEC60479-1 and analytical method in AC system, the protection against electric shock between DC 750, 400, 300, 220 V and AC 220 V systems are compared and analyzed based on ideal DC source model. It demonstrates that the negative grounded TT & TN DC distribution system has significant advantages over the traditional AC system, and the safety voltages are given, which could be a reference to develop the normative guidance for the application of LVDC in practical application.     

Electrolytic Efficiency of Late Landfill Leachate Pretreated by Electrolytic Oxidation

With trait of late landfill leachate treated hardly, it is an effective method of enhancing biodegradability of late landfill leachate that electrolytic oxidation pretreats late landfill leachate, and it is very necessary to calculate current efficiency. Varity of organic pollutants in the late landfill leachate is studied under the electrochemical action by some tests and current efficiency under different electrolytic condition is calculated. The results show that the most high current efficiency is 34.11% when the current density is 15 mA/cm^2 and electrolytic time is 6.5 h.     

Designing and Realization of Leak Current Fault Flatroof for Lauch Vihicle Controlling System

A visualized analysis system of leak current fault transmission graph is developed. Its functions, program structure and programming principle are described.The system is composed of fault diagnosing module and man machine exchanging module, which make the generation and analysis of leak current fault transmission graph for lauch vehicle controlling system simple and visualized. The system could automatically recognize the picture of transmission and analyze both qualitatively and quantitatively only by drawing it on the monitor by the mouse. Finally an example is given, where a satisfying result is acquired via drawing inputting method which is totally new and expanding-complementing the fault tree alglorithm.     

玉米粉皮胚含量测定器的研制及测定方法的探讨

通过大量试验研制出与国际法（ＧＢ１０４６３－８９）配套的仪器－玉米粉皮胚含量测定器，并对国际法进行了适当改进，提高了方法的准确度。     

Reliability Evaluation of Middle Voltage Distribution Networks

A reliability evaluation algorithm for middle voltage radial distribution network is presented. The algorithm applied ahead-searching-method to determining the area of breaker influencing, applied bidirectional-searching-method to determining faulting area, and applied behind-searching-method to determining connection switch. Then the type of nodes is determined. The reliability index of nodes,feerders and system can be easily computed by the type of nodes.So the computing effeciency is improved. At the same time, the curtailing load algorithms for low-voltage of buses and over-capacity of lines are presented and the foundation for the reliability assessment is established considering the power flow restriction. From the RBTS68-bus and other middle radial distribution networks,the effectiveness and availability of the method are verified.     

Electromagnetic induction method for detecting neglected loading of metal parts

In industrial production, neglected loading of metal parts is very normal. It not only causes the quality reduction of products, but also affects production rate. Based on the theory of electromagnetic induction, by supervising the assemblage process of metal parts, it is able to count the number of assembled metal parts so that automatic online monitoring of neglected loading can be achieved. The feasibility of using the eddy current method to monitor the motions of metal parts is analyzed theoretically and MATLAB is utilized to simulate. On the basis of theoretical analysis, the specific eddy current type transducer, the appropriate signal-processing circuits and the software are designed. A testing system is established for analog. This method can effectively solve the problem of neglected loading by artificial factors, save the costs of factories, raise the FPY of products.     

PARAMETRIC DESINGN OF DC FILTERS

The effect of phase angles of commutating voltages on the performance of dc filters is analgzed for the first time and a heurestic method is presented to choose appropriate parameters for swoothing reactors and dc filters.     

雷电灾害风险评估中P_B因子选取方法的分析及改进

在分析雷电直接击中建筑物导致物理损害的概率PB的影响因素的基础上,本文基于IEC62305推荐的不同防护等级的保护能力以及雷电流概率分布规律,推导出确定规范中LPL对应的PB因子优选值的一般过程。并针对推导过程完全依赖于规范推荐的防护等级及雷电活动特性,针对性差的特点,提出了根据建筑物直击雷防护实际情况以及项目所在位置雷电环境的统计特征确定PB因子的方法,该方法在一定程度上提高了PB因子选取的科学、准确性。同时,也对由于雷击物理过程复杂性、电气-几何模型的科学性、防护装置性能变化等使得PB因子取值中存在的问题进行了分析。     

油脂碘值的快速测定

报道了一种测定油脂碘值的新方法，不改变Hanus法操作步骤，只需在测定过程中加入催化剂醋酸汞。与Hanus法测定碘值相比，测定反应时间由30分钟缩短为4分钟，且本法相对误差小于0．5％，变异系数小于0．2％。     

微波法测定油料水分和脂肪含量的研究

利用微波法测定三种油料中水分、脂肪的含量。实验结果表明：油料种类不同,微波法测定水分的加热时间也不同。微波法测定油菜籽、花生、大豆的最佳条件为：功率为720 W,样品量为2.0 g左右,加热时间分别为9 min、8 min、7 min。测定结果与国标法相比相对误差在0.13%～4.24%之间。利用微波干燥后的样品测定油料脂肪含量,抽提时间由原来的8 h缩短为6 h。测定结果与国标法相比,相对误差在0.82%～2.0%,符合误差允许的范围。微波法测定油料水分、脂肪的含量不仅可以大大缩短分析时间,提高分析效率,而且测定结果准确。     

粮情检测系统打印格式及数据处理研究

现有的粮情检测系统打印格式过于固定,使用者无法根据自身的需要进行分析或编排,限制了使用者对粮温数据更充分的利用,从一定程度上也限制了粮情检测系统功能的发挥。本文通过对电子粮情检测系统的认真研究,采用一定的手段将OPI粮情检测系统内测得粮温数据导出,然后通过文本格式的转换,将粮温数据变成可以进行编辑的数值,根据不同格式的需要随心所欲地进行各种打印报告编排,通过改进,进一步提高了粮情分析效率,节省打印纸张,降低储粮成本。     

simulation of a brushless direct current motor based on finite state machine theory

A novel method simulating a brushless direct current(DC) motor was presented, based on principles of hybrid system modeling and finite state machine theory. Brushless DC motor control mainly focuses on controlling the on/off condition and power switch duration. Modes of control therefore can be defined by corresponding states, and the states can be combined as a finite state machine. This approach uses the popular Simulink/Stateflow simulation method to control brushless DC motor loops. A three phase brushless DC motor was analyzed to illustrate the process of model building with Simulink/Stateflow. The analysis demonstrates the feasibility and validity of the proposed method.     

机载 LiDAR生成DEM的一些关键问题评述

提取DEM是机载LiDAR技术应用研究关键内容之一,从LiDAR数据滤波、DEM模型选择、内插、误差控制和数据压缩等几个方面,分析当前利用机载激光雷达数据提取DEM的主要研究进展.着重讨论插值滤波、倾角滤波和形态学滤波算法,定量分析滤波算法的性能;分析比较确定性内插方法和地学统计内插方法,并指出内插方法在提高精度同时也要考虑稳定性和序同构性;论述DEM格网压缩和三角网压缩方法,并指出在满足地形可视化需要的同时提高压缩效率;并进行了总结展望,为相关研究提供参考.     

笼养蛋鸡健康养殖技术研究的现状与发展趋势

蛋鸡笼养因其突出的优点必将仍是中国以及许多国家主要的养殖模式,笼养蛋鸡健康养殖是目前急需解决的问题.在对畜禽健康养殖发展的重要性和基本概念进行界定的基础上,从优良品种选育、饲养方式完善与替代、饲养环境优化、优质饲料生产与配制、动物疫病防控、健康养殖管理6个方面对国内外笼养蛋鸡健康养殖调控技术研究现状进行了综述,最后探索性地提出了中国笼养蛋鸡健康养殖技术研究的发展趋势.     

Leak Current Fault Diagnosis Problem-Solving in Launch Vihicle Controlling System

In point of view of the system, the characteristic of leak current fault diagnosis in launch vehicle controlling system is analyzed. It is presented that the fault is a connecting way for sytem factors. By building some basic concepts such as componts, syptoms, observation and faults, the system model is turned into graph, where nodes represent components and edges represent fault transmission among components. Besides,designing rule, that is, bisection rule for diagnosing alglorithm is given based on the information theory. Operating feasibility and entropy function characteristic are analyzed using component trade-off value to substitute component entropy, giving fault problem-solving way based on the drawing model.     

Calculating and Eliminating Coupling Current Using the Partial Capacitance Method

A kind of simple model to analyze the coupling current between phases of Metal Oxide surge Arresters (MOA) is presented,and the coupling current in differet voltage degree using the partial capacitance method is calculated.The result of calculation is accorded with the practically measuring data.So it offeres a convenient and feasible way to minish the coupling current between phases when on line monitoring the MOA.