供电单位电力工作票网上流传系统的.net技术实现

本文针对电力系统变电工作票系统的原理结合在管理上的应用,采用面向对像技术用.net实现了供电系统变电工作票。对其实现原理及架构设计进行了分析。

一种分布式光纤多点电流传感系统

电力系统中,利用输电母线磁场的法拉第效应可研制磁光光纤电流传感模块,可在需要实时监控的节点处安放该模块,并采用波分复用(WDM)技术把所有节点的实时数据通过光纤网络汇集到中央计算机中,从而构成分布式光纤电流传感系统。

高压直流传变系统中一次电流传感器的实现

介绍了一种基于"分流器+光纤传输"技术的高压直流电流传变系统。与利用铁芯线圈电磁效应的传统直流测量系统原理不同,该系统利用分流器测量直流电流,在高压侧把测量信号转换为光信号,利用光纤将信号从高压侧传输到低压侧,既克服了传统测量暂态性、抗饱和能力较差的缺点,又很好地解决了高低压侧之间的信号隔离问题。由分流器、导电连接等元件组成的一次电流传感器是该系统的关键组件,由于分流器输出为极易受干扰的毫伏级电压信号,在分析了温升、集肤效应、膨胀应力和结构设计等因素对测量精度所造成的影响后,提出了一次电流传感器的实现方案。最后,通过建模仿真和试验验证了该方案设计合理,精度、温升等主要指标满足我国高压直流传变系统的需求。

《战国策》在北宋时期的整理和流传

北宋时期是《战国策》流传史上的关键时期，有赖曾的整理，《战国策》才得以“完篇”流传至今。本文考证认为：曾云经他整理后“三十三篇复完”，实仅指无整卷使失，字句段落乃至整章佚失仍不在少数；曾校此书的时间为嘉六年至嘉八年；此后，有李格非、王觉、孙朴等续校《战国策》；孙朴校本是北宋传本中的最佳本。

基于波分复用光纤网络的大电流实时监控系统设计(英文)

设计一种基于输电母线电流法拉第效应的磁光光纤电流传感系统。在需要实时监控的节点上放置传感器模块,并且利用波分复用光纤网络技术从各节点处传输实时数据至中央计算机,构成分布式光纤电流监控系统。

藏蒙《格萨尔》音乐比较研究

产生在雪域藏族的长篇英雄史诗《格萨尔》,上千年来以它特有的魅力被多民族所接受,并各自得到巨大的发展,形成了其独具的博大、渊深、丰厚与多彩.这种多民族共同发展一部史诗的现象,将为我们在民族关系和文化发展方面提供好多有价值的信息.因此,现就在《格萨尔》学中具有独特意义的藏蒙《格萨尔》音乐试做一比较研究.一、关于流传系统与音乐形态藏蒙两族在历史上以政治、军事等方面关系密切,特别是通过藏地宗教和文化对蒙区的大量渗透,将这种关系深刻化、永久化.《格萨尔》现象就是这种关系的一个缩影.

Applications of cascade multilevel inverters

Cascade multilevel inverters have been developed for electric utility applications. A cascade M level inverter consists of (M 1)/2 H bridges in which each bridge's dc voltage is supported by its own dc capacitor. The new inverter can: (1) generate almost sinusoidal waveform voltage while only switching one time per fundamental cycle; (2) dispense with multi pulse inverters' transformers used in conventional utility interfaces and static var compensators; (3) enables direct parallel or series transformer less connection to medium and high voltage power systems. In short, the cascade inverter is much more efficient and suitable for utility applications than traditional multi pulse and pulse width modulation (PWM) inverters. The authors have experimentally demonstrated the superiority of the new inverter for power supply, (hybrid) electric vehicle (EV) motor drive, reactive power (var) and harmonic compensation. This paper summarizes the features, feasibility, and control schemes of the cascade inverter for utility applications including utility interface of renewable energy, voltage regulation, var compensation, and harmonic filtering in power systems. Analytical, simulated, and experimental results demonstrated the superiority of the new inverters.

Role of Downward Momentum Transport in the Formation of Severe Surface Winds

The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan and Shandong Provinces of China. The results show that there was a strong westerly jet belt with a wind speed greater than 30 m s 1 and a thickness of 5 km at an altitude of 11-16 km. The jet belt was accelerated, and it descended while the squall line convective system occurred. It was found that the appearance of strong negative perturbation pressure accompanied by the squall line caused the acceleration of the upper-level westerly jet and increased the horizontal wind speed by a maximum of 18%. Meanwhile, the negative buoyancy due to the loading, melting, and evaporation of cloud hydrometeors induced the downward momentum transport from the upper levels. The downward momentum transport contributed approximately 70% and the surface cold pool 30% to the formation of severe surface winds.

Alternating current sensor system using GMM

Based on the principle of FBG sensing mechanism,an alternating current sensor system,which uses a FBG attached on a magnetostrictive rod as the probe,was developed.A dynamic interrogation method was proposed based on wide band light source,by making use of the linear relationship between its power intensity and wavelength as spectrum filter.A 50 Hz AC signal is interrogated successfully through the developed system and the system transfer function was established.The amplitude and frequency of the AC signal to be measured can be well deduced through the transfer function of the system, so the alternating current measurement is accomplished.

Simulation on model predictive control for PMSM drive system based on double extended state observer

A novel double extended state observer(DESO)based on model predictive torque control(MPTC)strategy is developed for three-phase permanent magnet synchronous motor(PMSM)drive system without current sensor.In general,to achieve high-precision control,two-phase current sensors are necessary for successful implementation of MPTC.For this purpose,two ESOs are used to estimate q-axis current and stator resistance respectively,and then based on this,d-axis current is estimated.Moreover,to reduce torque and flux ripple and to improve the performance of the torque and speed,MPTC strategy is designed.The simulation results validate the feasibility and effectiveness of the proposed scheme.

Traffic Assignment Forecast Model Research in ITS

As an important role in the development of ITS, traffic assignment forecast is always the research focus. Based on the analysis of classic traffic assignment forecast models, an improved traffic assignment forecast model, multi-ways probability and capacity constraint (MPCC) is presented. Using the new traffic as- signment forecast model to forecast the traffic volume will improve the rationality and veracity of traffic as- signment forecast.

Research on Tian-Guang AC and DC Hybrid System Operation

This paper describes the transmission capability of Tian-Guang AC and DC hybrid system, as well as various operational effects on the transmission capability, such as HVDC modulation, AC voltage level and generating reserves. The study has shown that when both AC and DC systems operated in parallel, this system has higher transmission capability than operated separately, thus it satisfies stability criterion after the project put into operation.

Mathematical model for coupled reactive flow and solute transport during heap bioleaching of copper sulfide

Based on the momentum and mass conservation equations, a comprehensive model of heap bioleaching process is developed to investigate the interaction between chemical reactions, solution flow, gas flow, and solute transport within the leaching system. The governing equations are solved numerically using the COMSOL Multiphysics software for the coupled reactive flow and solute transport at micro-scale, meso-scale and macro-scale levels. At or near the surface of ore particle, the acid concentration is relatively higher than that in the central area, while the concentration gradient decreases after 72 d of leaching. The flow simulation between ore particles by combining X-ray CT technology shows that the highest velocity in narrow pore reaches 0.375 m/s. The air velocity within the dump shows that the velocity near the top and side surface is relatively high, which leads to the high oxygen concentration in that area. The coupled heat transfer and liquid flow process shows that the solution can act as an effective remover from the heap, dropping the highest temperature from 60 to 38 ℃. The reagent transfer coupled with solution flow is also analyzed. The results obtained allow us to obtain a better understanding of the fundamental physical phenomenon of the bioleaching process.

Connecting Wind Turbine Generator to Distribution Power Grid--A Preload Flow Calculation Stage

A distribution grid is generally characterized by a high R/X （resistance/reactance） ratio and it is radial in nature. By design, a distribution grid system is not an active network, and it is normally designed in such a way that power flows from transmission system via distribution system to consumers. But in a situation when wind turbines are connected to the distribution grid, the power source will change from one source to two sources, in this case, network is said to be active. This may probably have an impact on the distribution grid to whenever the wind turbine is connected. The best way to know the impact of wind turbine on the distribution grid in question is by carrying out load flow analysis on that system with and without the connection of wind turbines. Two major fundamental calculations： the steady-state voltage variation at the PCC （point of common coupling） and the calculation of short-circuit power of the grid system at the POC （point of connection） are necessary before carrying out the load flow study on the distribution grid. This paper, therefore, considers these pre-load flow calculations that are necessary before carrying out load flow study on the test distribution grid. These calculations are carded out on a test distribution system.

Application of Neuro-Fuzzy Estimation for Rotor Flux in Speed Vector Control of Bearingless Induction Motor

The main requirement of a vector controller is knowing the magnitude and position of the rotating flow in the rotor. This feature permits to use either flow sensors or flow estimators. The solution chosen was the estimation of rotor flux with the hybrid neuro-fuzzy system. The motor characteristics are： 3.75 kW （5 HP）, two pole-pair, operate at 60 Hz and air-gap length 0.2 mm. The ANFIS （adaptive neuro-fuzzy inference system） was used to tune the membership functions in fuzzy system. The hybrid estimator aims at compensating possible parametric variations of the machine caused by agents, such as temperature or nucleus saturation. The simulated results have shown good performance.

Application of genetic algorithm for influent flow distribution in the four stage A/O biological nutrient removal system

The application of the Genetic Algorithm （GA） for the influent flow optimized distribution in the four stage pilot plant of Step-Feed Biological Nutrient Removal （BNR） System was discussed. Under decided process parameter and influent water conditions, the objective function of optimization was designed to minimize the difference between estimated and required effluent concentrations at the four stage pilot plant of Step-Feed BNR System, the optimized parameter for influent distribution ratios of the four stages is 37.2%, 27.4%, 23.2% and 12.2% respectively. According to the optimizations results and raw wastewater pilot-scale experiment, the average removal efficiencies for pollutants are higher.

The synthesis of micro-sized silicon carbide whiskers and the application for heat transfer enhancement

This paper presents a simple and cost-effective method for the production of micro-sized silicon carbide whiskers at high yield and the effect on heat transfer enhancement for the whisker laden fluids. For SiC whisker synthesis, the starting powder mix- ture is obtained by milling short carbon fibers with the white ashes of rice hulls. Calcina：ion in argon, together with the subse- quent purification process, results in a high yield of SiC whiskers, which possess a diameter of 200-400 nm and a length of several tens of microns. The formation of the whiskers is discussed according to VS growth mechanism. Convective heat transfer performance in small channel tubes is then studied for fluid systems mixed with those micro-sized SiC whiskers at different concentrations. The heat transfer coefficient of SiC containing fluid can be significantly improved in comparison to the base fluid.

Study on the performance of TEG with heat transfer enhancement using graphene-water nanofluid for a TEG cooling system

Improvement of the heat transfer effect of cold side of a thermoelectric generator(TEG) is one of the approaches to enhance the performance of the TEG systems.As a new type of heat transfer media,nanofluids can enhance the heat transfer performance of working liquid significantly.In this study,the performance of a commercial TEG with graphene-water(GW) nanofluid as coolants in a minichannel heat exchanger is investigated experimentally at low temperatures.The results show that the output power of TEG increases with the flow rate under 950 mL/min.However,the fluid flow rate has no influence on the output power of TEG with higher flow rate(larger than 950 mL/min) when the heat transfer dynamic balance state of the system is reached.The optimal concentration and flow rate of nanofluid are 0.1 wt%and 950 mL/min,respectively.At the optimal conditions,the improved voltage,output power and conversion efficiency with GW nanofluid applied in the cooling system are increased by11.29%,21.55%and 3.5%in comparison with those with only water applied,respectively.

Experimental and Theoretical Analysis of an Optical Current Sensor for High Power Systems

A magneto-optical sensor, using a dual quadrature polarimetfic processing scheme, was evaluated for current metering and protection applications in high voltage lines. Sensor calibration and resolution were obtained in different operational conditions using illumination in the 1550-nm band. Results obtained indicated the feasibility of interrogating such sensor via the optical ground wire （OPGW） link installed in standard high power grids. The polarimetric bulk optical current sensor also was theoretically studied, and the effects of different sources of error considering practical deployment were evaluated. In particular, the interference from external magnetic fields in a tree-phase system was analyzed.

Transportation of dynamic biochemical signals in non-reversing oscillatory flows in blood vessels

Biological processes and behaviors of endothelial cells on the inner surfaces of blood vessels are regulated by the stimulation from biochemical signals contained in the blood.In this paper,the transportation of dynamic biochemical signals in non-reversing oscillatory flows in blood vessels is analyzed by numerically solving a nonlinear governing equation for the time-dependent Taylor-Aris dispersion.Results show that the nonlinear frequency-amplitude modulation of the transportation of biochemical signals is more(less) significant when the frequency of an oscillatory flow is close to(higher than) that of an oscillatory signal.Under steady flow,the transfer function for the signal transmission system is obtained,showing that the system is a low-pass filter.Lower inner radius or higher center-line velocity of a blood vessel increases the cutoff frequency of the transportation system.These results suggest the possibility and condition for the 'remote' transmission of low-frequency dynamic biochemical signals in pulsatile blood flows.