New initial position detection technique for three-phase brushless DC motor without position and current sensors

This paper presents a new detection technique of initial position for a three-phase brushless DC motor which does not require any current and position sensors, and thereby significantly reduces the cost. The fundamental principle of the technique is to determine the initial position of the permanent magnet by the time periods of discharge of stator windings, which are excited before discharge. As compared to previous approaches, the presented technique does not cause any rotation during detection, and it is therefore very promising for particular kinds of applications, which do not allow the motor to rotate potentially in the wrong direction during initial position detection, e.g., electrical vehicles. As compared to earlier techniques, the presented technique dramatically simplifies the detection procedures and cost. Experimental results derived from a field-programmable gate-array-based control system are presented to demonstrate the feasibility of the presented technique.     

A contactless technique for determining the average sizes of erosion-hazardous droplets in polydisperse wet steam flow

A new combined numerical and experimental technique for determining the average sizes of droplets contained in wet steam flows is presented, central to which is the use of laser diagnostic systems. Basic aspects relating to implementation of the technique under static conditions on an experimental steam dynamic setup are considered. Primary results obtained from approbation of the technique for a wet steam flow moving in a narrowing flat nozzle are presented.     

Optimizing reactive volt-ampere regulating devices in transmission systems using a full three-phase representation

A technique is presented for optimizing the locations and sizes of reactive volt-ampere regulating devices in transmission networks or for optimal control of existing devices. The technique is based on linear programming concepts. It uses a full three-phase representation of the transmission network and is therefore capable of analysing systems with unbalanced loads. The technique is also capable of optimizing with both positive and negative variations in the values of the regulating devices. The new technique is applied to an example system and the results are presented.     

机器视觉中照明技术的研究进展

本文综述了机器视觉应用中光学测量技术的最新理论与实验研究结果。着重对光源类型、照明方式以及光源颜色的选择和光源位置的控制在机器视觉成像系统的作用做了深入细致的描述。在此基础上展望了光学技术在机器视觉中的应用前景,并指出了目前研究中有待解决的问题。     

A new modulation technique for reducing the input current harmonicsof a three-phase diode rectifier with capacitive load

In this paper, a new technique for shaping the line current and reducing the total harmonic distortion in a three-phase bridge rectifier, feeding a capacitive load, is presented. Using the topology of a three-level three-switch pulsewidth modulated (PWM) rectifier, a new control technique has been implemented. The main objective here is to minimize the total harmonic distortion (THD) of the line current under different load conditions (20%-100% of full load). A review of the problems inherent in a bridge rectifier feeding a capacitive load and the possible solutions are first presented. Subsequently, the analysis of the new circuit and the control technique used are described, along with simulation results. Finally, the experimental results on a 1.6 kW prototype are presented     

控制系统中的容错技术

介绍容错技术的特点、类型和实现方法 ,并引用实例 ,针对某一特定旋转机械子系统增加了容错技术后的性能进行讨论和仿真。说明容错技术对提高控制系统可靠性起到了一定作用。     

全息动平衡原理

回顾了柔性转子动平衡技术的发展过程，阐述了在全息谱技术基础上发展而成的全息动平衡技术的基本概念，介绍了全息动平衡中的振型分离、迁移矩阵、计算机模拟和遗传算法优化技术，总结了全息动平衡技术的优越性。     

基于多场景和模糊技术的综合无功规划

无功规划问题涉及大量不确定因素,文中分析了多场景技术和模糊技术在电力系统不确定规划应用中只能分别考虑单一类型不确定因素的不足,结合两者的优势,提出了基于这2种规划思想的综合无功规划模型。模型中的多场景和模糊方法分别对应工程中典型的网络结构和负荷水平这2类不确定因素,以无功设备投资期望收益为目标函数,使得优化结果达到概率上的最优。多场景计算采用多种群遗传算法,并通过国内某地区实际电网算例证明了该模型和算法的有效性。     

A technique for estimating transmission line fault locations from digital impedance relay measurements

A technique is presented that is suitable for estimating locations of shunt faults. The estimates are reasonably accurate even if the fault resistance is substantial and the transmission line is connected to energy sources at both terminals. The technique uses post fault fundamental-frequency voltages and currents measured at the two line terminals. The measurements need not be synchronized, and the source impedances are not used by the estimation procedure. The mathematical development of the technique is presented. Sample test results using simulated fault data are included.<>     

全息动平衡原理

回顾了柔性转子动平衡技术的发展过程,阐述了在全息谱技术基础上发展而成的全息动平衡技术的基本概念,介绍了全息动平衡中的振型分离、迁移矩阵、计算机模拟和遗传算法优化技术,总结了全息动平衡技术的优越性。     

管道焊接前防锈新工艺在锅炉施工中的应用

介绍一种管道焊接前防锈新工艺。该工艺能不仅很大程度地节约施工消耗性材料,节省大量的人力和物力,同时还收到较好的经济效益和环保效果。对该工艺所使用的材料及使用方法进行介绍,并结合以往施工工艺进行比对。     

A Gauss-Jacobi-Block-Newton method for parallel transient stabilityanalysis [of power systems]

A parallel method for the transient stability simulation of power systems is presented. The trapezoidal rule is used to discretize the set of algebraic-differential equations which describes the transient stability problem. A parallel Block-Newton relaxation technique is used to solve the overall set of algebraic equations concurrently on all the time steps. The parallelism in space of the problem is also exploited. Furthermore, the parallel-in-time formulation is used to change the time steps between iterations by a nested iteration multigrid technique, in order to enhance the convergence of the algorithm. The method has the same reliability and model-handling characteristics of typical dishonest Newton-like procedures. Test results on realistic power systems are presented to show the capability and usefulness of the suggested technique     

A new generation scheduling program at Ontario Hydro

The new daily generation scheduling model for the Ontario Hydro system is presented. The model is capable of considering the thermal and hydraulic systems together with system reserve requirement and transmission losses. The hydraulic system is considered in a detailed formulation that can handle river couplings in a complete manner. Inability to do this was a major weakness in the peak shaving technique used since early 1970s. A special network programming technique has been used to solve the problem. This method has proved to be very efficient from a computational point of view. Test results from application of the new technique are presented and compared to the peak shaving method. The user has estimated 1.4 million dollars per year of savings from the new computer package     

Fiber Bragg sensors interrogation based on carrier generation bymodulating the coupling length of a wavelength-division multiplexer

A compact all-fiber interrogation technique for Bragg sensors is presented. It is based on the generation of an electric carrier by modulating the coupling length of a wavelength-division multiplexer (WDM). Theoretical and experimental results are presented when both serrodyne and sinusoidal modulations are considered. It is shown that this technique provides static microstrain resolution in measurement intervals larger than some millistrain     

Frequency domain identification for undergraduates

A method to synthesize a transfer function from experimentally obtained gain and phase data is presented. The least squares technique discussed minimizes the error between the inverse transfer function and the inverse of the experimental frequency response data. The relevant formulas are derived in a straightforward manner so that undergraduate students can follow the development. The inverse formulation appears to give a better fit to the data than the previous approaches. This is most likely due to the fact that the technique biases the error with the numerator rather than the denominator of the derived transfer function. There is, however, no guarantee that a minimum phase transfer function will result from this technique. The user of this technique must preselect the numerator and denominator orders. The formulation assumes that there are no zeros at the origin. A modification to the basic scheme is presented for this case     

Export/import of spinning reserve in interconnected generationsystems

Interconnected power systems may import energy and/or purchase spinning reserves from neighbors in order to reduce risk. A probabilistic technique is presented to assess import and/or spinning reserve purchase requirements of interconnected systems in order to overcome the effects of inadequate operating capacity on unit commitment risk. A unit commitment technique which can include options of spinning reserve purchase/sale is presented. A method of assessing the portion of the running cost in interconnected power systems due to export/import and purchase of spinning reserve is also illustrated     

An efficient stochastic self-scheduling technique for power producers in the deregulated power market

Generation scheduling and dispatch are determined by individual power producers’ bids in a deregulated power market. The benefits obtained by a power producer will depend largely on how effectively it can incorporate the variation of the market price in its generation scheduling. A stochastic scheduling technique is presented in this paper for maximizing a producer’s benefit considering the stochastic nature of power price. Formulation of the problem has been presented in detail. Two approaches to the solution, namely two-stage and multi-stage stochastic methods, are presented which accommodate the features of the day-ahead and hour-ahead power markets, respectively.Implementation of the technique is illustrated by applying the technique to scheduling by a power producer with 11 generators in two different seasons. The price data from a real system has been used for the price forecasting and the formation of price scenario tree. It is shown through illustrative case studies that the proposed stochastic methods can enhance benefits if proper values are assigned for the probabilities of the price scenarios and if the selection of the probabilities of price scenarios are directly related to the variation of the actual power prices. The proposed technique is particularly effective when the uncertainty in the price is high and the price forecast is not very accurate.     

Dynamic transmission planning under uncertainty

A new approximate method is presented to solve the dynamic optimization problem in long-range transmission capacity expansion planning. The method employs a static optimization technique along with an iterative procedure to simulate the dynamic solution.The proposed method can be simplified to provide a fast technique, also discussed in the paper. Comparison is made between the fast technique and the conventional horizon year planning approach.     

1kW光伏并网逆变器的设计

介绍了1kW并网逆变器的设计。详细地介绍了逆变器的基本设计和关键技术,以及并网电流的控制策略。并且完成试验装置,验证了逆变器的稳定性和控制策略的可靠性。     

低压母线槽CAD系统的研究

基于AutoCAD2000开发的低压母线槽CAD系统，综合应用了面向对象技术，工程数据库技术和二次开发技术等，提高了设计效率，本文对其基本结构，设计思想，关键技术进行论述。