Results from tests of MV3600/1000/490 mill-ventilators in milling Chinese brown coals

The design characteristics of MV3600/1000/490 mill-ventilators intended for milling Chinese brown coals are given, and the results of their industrial tests are discussed.     

Active inductance simulation with grounded condensers

A technique is presented for grounding the condensers of active RC networks, which requires an additional difference amplifier stage per capacitor grounded. A generalized grounded capacitor (GC) circuit is derived for simulating a grounded inductance and it is shown that the GC-versions of the circuits proposed by Prestcott, Rao–Venkateswaran, and Berndt–Dutta Roy form special cases of this circuit. A critical investigation is made of the sensitivity performances and the frequency limitations introduced by the operational amplifiers (OA's).     

Electromagnetic gate-inductor electric drives with open-loop control systems

A simplified transducer-free realization of electromagnetic gate-inductor electric drives with openloop control systems is proposed with prospective applications for the majority of rotary-, linear-, and alternatemotion-type industrial mechanisms. A functional scheme of the control system for the electric drive under consideration is given. A simplified calculation of the basic parameters of the rotary motion electric drive is presented. The advantages of reducer-free electric drive constructions are shown.     

相位补偿型电光A/D转换器的优化设计

提出了一种可以提高泰勒型电光A/D转换器有效位的方案,其原理是用相位补偿的直接转向波导或分支波导代替传统的S-弯曲波导.采用有限差分束传输法设计出由质子交换工艺制作的高折射率微棱镜进行相位补偿的4位电光A/D转换器的波导结构,利用保角变换方法对调制电极参数进行优化.最后得到优化结构参数为设计4-6位的高速电光A/D转换器提供了理论依据,同时也得到了一些对实际设计有一定指导意义的结论.     

晶闸管的光纤触发技术

介绍了一种新的晶闸管触发电路，用光纤代替了传统的脉冲变压器，尤其适合应用在高电压的场合。     

Purdue's Junior-Level Control Laboratory with Microprocessors

A microprocessor-based direct digital control system laboratory developed at Purdue University is discussed. The microprocessor controller interfaces directly to an analog computer for simulation control or to control components such as motors, heaters, etc. Available resident processor routines (A/D, D/A, arithmetic, timing, etc.) can be easily configured into a digital control system program allowing strategies to be quickly developed and tested. Al operations are performed directly at the control station via a terminal keyboard, and the system has the potential for stand-alone operation with a graphics output terminal A typical digital control system example-servo position control-has been developed for use in the Junior Control Laboratory. In addition to unlimited possibilities for software strategies, patchable features such as comparators, logic circuitry, timing functions, etc., are available on the front panel, allowing quick, efficient development of a complete digital control system.     

Resonant snubbers with auxiliary switches

A resonant snubber is described for voltage-source inverters, current-source inverters, and self-commutated frequency changers. The main self-turnoff devices have shunt capacitors directly across them. A temporary parallel path through a small ordinary thyristor and inductance takes over high-stress turn-on duty from the main device in a manner that leaves no energy trapped after switching     

Hybrid switch with controlled switching for circuits with capacitor banks

An original scheme for constructing a hybrid switch (HSW) for switching capacitor banks is proposed and proven. The experimental studies of the transient processes during current commutation in the hybrid switch are conducted. The dependences of the transition time of the current between a vacuum arcquenching chamber (VDK) and a diode unit on the switching current are determined. A mathematical model of the current transition between the vacuum arc-quenching chamber and diode units under different switching modes is developed.     

A new topology for parallel resonant DC link with reduced peakvoltage

A new topology for a parallel resonant DC link is proposed. It offers reduced peak DC link voltage without generating high di/dt. The effect of various parameters on the link voltage waveform is discussed. A design procedure is outlined to determine the component values for any desired resonant frequency. A comparison with the actively clamped circuit is given. There is an excellent correlation between the experimental and simulation results     

Multi-winding multi-phase transformer model with saturable core

A model is presented for a multiwinding multiphase transformer developed by the nodal inverse inductance matrix (NIIM). To obtain the NIIM the inverse of the inductance matrix is needed. Due to the strong magnetic coupling among the windings, the inductance matrix of a transformer is ill-conditioned. A new way is described to find the inverse of the inductance matrix for transformers. Core saturation and hysteresis effect are also considered. The model can be used to calculate the transients in the windings, ferroresonance, and inrush currents and to perform steady-state analysis in complicated winding arrangements and network configurations     

EMD信号分析方法端点问题的处理

经验模态分解（EMD）是一种新的处理非线性、非平稳的数据分析方法，但是在利用样条插值获得上下包络过程中存在着棘手的端点问题。在解决该问题已有的添加极值点算法的基础上，提出了通过添加极值点和对称延拓相结合的方法抑制端点问题的思路和策略。针对一个仿真振动信号，对比分析了直接以数据端点作为极值点、多项式拟合算法、神经网络延拓算法、极值点与对称延拓相结合4种算法的效果，结果显示了所提出方法能有效地抑制端点效应。     

单相与三相输入兼容的特定消谐式变频器研究

设计了一种新型单相与三相输入兼容的特定消谐式变频器.提出了一种单相与三相输入兼容的变频器主电路,深入研究了离线计算与在线计算相结合实现特定消谐的方法.实验结果表明,该变频器具有消除谐波次数多,残余谐波含量小,电压利用率高,直流母线电压高,输出稳压特性好,开关角数据存储空间小的特点,有很好的应用前景.     

考虑合环调电约束的配电网快速重构方法

为解决10 kV配电网合环调电过程针对合解环开关最优选择问题,提出了以网络损耗为目标,以合解环网络的线路功率限值、电压限值和保护限值为约束条件进行网络重构的方法。该方法采用快速改进遗传算法按开关状态进行二进制染色体编码,利用合环后网络的计算结果,构建针对基因染色体品质编码库,以校核下一代基因染色体编码,加速了算法过程。同时利用分布系数法计算解环后网络的潮流状态,避免了再次潮流计算。测试算例验证了算法的有效性,为合环调电安全实施提供了保证。     

Optimal AGC tuning with genetic algorithms

This paper deals with the application of genetic algorithms for optimizing the parameters of conventional automatic generation control (AGC) systems. A two-area nonreheat thermal system is considered to exemplify the optimum parameter search. A digital simulation is used in conjunction with the genetic algorithm optimization process. Several integral performance indices, or cost functions, are considered in the search for the optimal AGC parameters. The work is further extended to include the use of more elaborate feedback control strategies, such as the proportional-plus-integral type, within the decentralized frame. The results reported in this paper have not been obtained before and they demonstrate the effectiveness of the genetic algorithms in the tuning of the AGC parameters.     

Fast-acting long-stroke bistable solenoids with moving permanentmagnets

The force produced by conventional solenoids is an attraction force exerted across the air gap. It is, therefore, weakest at the beginning of motion when the gap is fully open. For that reason, such solenoids cannot be considered for fast-acting applications when the stroke is large. A new category of actuators is described, capable of providing high initial accelerations and, therefore, fast motion, even when the air gap is large. The concept consists in using the repulsion force that a stationary energized coil can exert on a moving permanent magnet. An experimental assessment of the performance capabilities of this type of actuator is presented. A mathematical model of their dynamics, suitable for design and optimization purposes, is also presented     

一种开关电感型准开关升压变换器

提出了一种开关电感型有源阻抗变换器,并对该变换器工作原理和连续导通工作模式的边界条件进行了探究;对变换器的各元器件进行了电压电流应力计算和参数设计。结果表明,该变换器具有电压增益高、电感电流应力低、元器件总体数量少等特点。利用状态空间平均法建立了变换器的小信号动态模型,证明了该变换器的稳定性。仿真和实验证明了该变换器的有效性。     

Hybrid phase arm power module with nonlinear resonant tank

A soft switching concept for a phase arm module, suitable for switching frequencies in the ultrasonic range, is introduced. Apart from series smoothing capacitors on the supply the only additional components to the switches and diodes of the phase arm is a parallel nonlinear resonant tank. A major feature is that the installed switching power of the semiconductors is close to 1 p.u. pulse-width modulation (PWM), as obtained through control of the saturation depth of the saturating inductor     

配电自动化条件下配电系统供电可靠性评估

针对配电自动化新技术的应用提供了提高供电可靠性的情况,建立了面向供电可靠性分析的配电系统简化模型。该模型将复杂配电网分解为许多最小配电区域,分别计算出其等效故障率和等效平均故障修复时间,再以最小配电区域为单位设置故障并分析其后果,还计及了母线、开关故障和检修的影响,并且在分析故障和检修影响时考虑了系统的电气极限容量,在确保系统安全的条件下借助配电自动化,采取以甩负荷最小为目标的网络重构,最终得出各个负荷点以及系统的供电可靠性指标。实例分析表明,提出的方法可行并显著提高了分析效率,且能够反映配电自动化对配电系统供电可靠性的影响。     

Transient model for induction machines with stator winding turnfaults

A transient model for an induction machine with stator winding turn faults is derived using reference frame transformation theory. A state-space representation of the dynamic equations, suitable for digital simulation is provided. Steady-state equivalent circuits are derived, from which the sequence components of the line currents can be estimated as a function of fault severity. Experimental results are provided to validate the derived model