电能反馈型电子负载的设计与实现

采用电压型 PWM变流器设计实现了电子模拟功率负载 ,控制系统采用了性能优良的专门用于实时控制领域的数字信号处理器 TMS32 0 F2 40 ,优良的控制方法使得所研制的功率负载在实现电能的再生并网时功率因数趋近于 1.0 ,且电压和电流谐波满足 IEEE- 5 19标准。实验结果证实该方案能很好的解决直流电源出厂试验问题。

Enhanced Photoelectrochemical Property of Zn Loaded TiO2 Nanotube Arrays Electrode

TiO2 nanotube arrays （TNTs） electrode loaded with Zn nanoparticles was prepared by anodization and the size of Zn nanoparticle loaded on TNTs electrode was controlled by chronoamperometry deposition time. Results of SEM and XRD analysis show that Zn nanoparticles had a diameter of about 15-25 nm when the deposition time was 3-5 s. The UV-Vis diffuse reflectance spectra show the Zn loaded harvest light with 480-780 nm more effectively than the unloaded sample. The photocurrent response of Zn loaded TNTs electrodes were studied, the results showed that TNTs electrodes loaded with Zn nanoparti-cles has 50% increased photocurrent response under high-pressure mercury lamp irradiation compared with unloaded TNTs electrode.

农网低压计量箱应用中的问题

结合低压计量箱的使用情况,介绍在农网改造中,使用低压计量箱存在的一些问题及改进办法。

提高变电站计量装置准确度分析

通过实例,分析了电压互感器二次负载、电压互感器二次回路压降、电流互感器变比及电能表结构对变电站侧电能计量装置计量准确度的影响,并提出了改善措施。

Solar-Powered Direct-Current Loads in Small Buildings

Traditional light bulbs （e.g., incandescent, fluorescent） use too much electricity, convert very little energy into light of sufficient quality and in their production use toxic contaminants. During the last few years, a new type of light source, LED （light emitting diode） bulb, has gained increasing popularity and its costs are set to plunge even further. LED bulbs offer many advantages over traditional sources, and they can be used as a direct replacement to existing lighting. This paper will use a spreadsheet-based analysis with hourly solar data supplied by Ecotect to show that, the efficiency of LED installations can be increased when used in conjunction with photovoltaic modules, as the two generate （and use） DC （direct-current） electricity, thereby eliminating intermediate-level losses in the electronic circuitry. If a storage battery is included, the solar panels generate electricity during the times when the occupants are not necessarily using the lighting, but the stored electricity can be used to power the lighting when the energy is required. The latest results demonstrate that, a slight reduction in the required floor area to be lit allows the solar-battery-LED system to be implemented in small buildings using a storage battery size that is within the range of present commercial devices.

Fuzzy Logic Controlled Dual Active Bridge Series Resonant Converter for DC Smart Grid Application

Over the last few years, smart grids have become a topic of intensive research, development and deployment across the world. This is due to the fact that, through the smart grid, stable and reliable power systems can be achieved. This paper presents a fuzzy logic control for dual active bridge series resonant converters for DC smart grid application. The DC smart grid consists of wind turbine and photovoltaic generators, controllable and DC loads, and power converters. The proposed control method has been applied to the controllable load＇s and the grid side＇s dual active bridge series resonant converters for attaining control of the power system. It has been used for management of controllable load＇s state of charge, DC feeder＇s voltage stability during the loads and power variations from wind energy and photovoltaic generation and power flow management between the grid side and the DC smart grid. The effectiveness of the proposed DC smart grid operation has been verified by simulation results obtained by using MATLAB and PLECS cards.

Design and Performances of High-Current Modular Pulsed Power

A design of the high-current modular pulsed power generator and results of the test of this generator are presented. The generator is based on two capacitors each of 2.5μF and 50 kV maximum charging voltage. Two multi-gaps gas spark switches with capacitive coupled triggering are used to discharge stored energy into the load. The triggering pulse with amplitude up to 70 kV and rise time of-50 ns is supplied by three-stage Marx-generator. The output of each capacitor with multi-gaps spark switch is connected to the load by eight coaxial cables -1 m in length. The total inductance of the generator does not exceed 200 nil. At 40 kV charging voltage this generator produces 180 kA with a quarter of period of 1.6 μs at short circuit load of-15 nil. The generator has been used in the research of underwater electrical wire explosion. The space separation of the load and modules of generator allows one to avoid possible damages of the generator by shock waves produced during the wire explosion. In addition, this modular generator design allows to increase easily the number of modules and to reach several hundreds of kiloamperes in the load.

Integrated Power Conversion for Multiple DC Voltage Sources and Its Power Quality

In a smart grid, electric loads are supplied by various DC （direct current） power sources, such as solar cells or batteries. On the other hand, traditional AC （alternating current） loads like a directly connected induction motors will also be used. In the circumstances, a smart power conversion unit is one of key components, which can integrate these DC or AC apparatus and trade power among them. Authors have developed an integrated power converter based on a well-known circuit topology of flying capacitor multilevel converter. This paper describes the detail of the circuit topology and its characteristics depending on designed parameters. The achieved power quality is also verified by simulation study.

Frequency Variations of Power System Due to Switching of Renewable Energy Sources

Power systems in Germany mainly containing intermittently operating renewable sources require load/frequency control which is performed up to now at the AC transmissioh and distribution levels. Frequency control can be achieved by employing short-and long-term storage plants buffering and complementing renewable energy sources. A representative grid consists of a natural-gas-fired plant serving as frequency leader, long-term storage plant, wind-power farm with associated short-term storage plantfor energy buffering, and photovoltaic farm with associated short-term storage plant interconnected by a long transmission line to two load circuits. Transient analysis is performed with Mathemafica solving the differential equation system for frequency variation. Powerflow through the AC transmission line is limited by its impedance. The long transmission line must be segmented to achieve stability and voltage control over an 800 km distance. The renewable plants must be operated together with the storage plants in order tominimize frequency variations by smoothing the power output of renewable plants, achieving step-wise control of the transmission-line power. Although to date only AC Iransmission lines in Germany exist, it is anticipated that within the next 10 years these will beaugmented by DC high-voltage lines.

A Case Study Survey of the Impact of the Inductive Loads on Power Quality

Power quality is a complex term that is defined by the legislation, but also as an obligation of the supplier and customer. The customer must return the negative effects of its consumers （taking reactive power, harmonic generation, phase unbalance） down to the prescribed limits. This primarily refers to the presence of non-linear consumers, leading to distortion of the basic parameters of voltage and current, in steady or transient conditions, and therefore the deformation of waveform. One way to reduce the negative feedback effects, especially with inductive loads, is the reactive energy compensation. The paper presents one of the solution for reactive power compensation, applied on the pumping station of public company ＂Waterworks and Sewerage---Bar＂, Bar.

Assessing Micro-generation＇s and Non-linear Loads＇ Impact in the Power Quality of Low Voltage Distribution Networks

Distribution networks face an increasing penetration of solar PV （photovoltaic） and small WTG （wind turbine generator） as well as other forms of micro-generation. To this scenario, one must add the dissemination of non-linear loads such as EV （electric vehicles）. There is something in common between those loads and sources： the extensive use of power electronic converters with commutated switches. These devices may be a source of medium-to-high frequency harmonic distortion and their impact on the local distribution grid must be carefully assessed in order to evaluate their negative impacts on the network, on the existing conventional loads and also on other active devices. In this paper, methodologies to characterize effects such as： harmonics, network unbalances, damaging power line resonance conditions, and over/under voltages are described and applied to a real local grid configuration.

Study on load performance of electric motor system used in hybrid electric vehicle

The performance of the power assist, global optimization solved by dynamic programming （DP） method, Chery and Insight control strategies are analyzed using the mild parallel hybrid electric vehicle （PHEV） model based on Insight structure. The influence of the four control strategies to the load power of the electric motor system used on parallel hybrid electric vehicle is studied. It is found that 80 percent of the motor load power points are under 1/5 of the electric peak power. The motor load power of the power assist control strategy is distributed in the widest range during generating operation, and the motor load power of the global optimization control strategy has the smallest one.

Smart load control of the large-scale offshore wind turbine blades subject to wake effect

The smart fatigue load control of a large-scale wind turbine blade subject to wake effect was numerically investigated in this paper. The performances were evaluated and compared at selected typical wind speeds within the whole operational region under three turbine layout strategies, i.e., column, row and array arrangements, together with a single turbine case as reference, utilizing our newly developed aero-servo-elastic platform. It was observed that not only the blade fatigue loads but the stabilities of power and collective pitch angle were effectively controlled for all cases, especially at the highest studied hub velocity of20 m/s, leading to the averaged reduction percentages in the standard deviations of the flapwise root moment, the flapwise tip deflection and the root damage equivalent load, of about 30.0 %, 20.0 % and 20.0 %, respectively. Furthermore, the control effectiveness gradually lessened in the sequences of single, column, row and array cases, with successively increasing effective turbulence intensity,within regions II and III. The performances in region III,associated with the impaired flow separation on the blade by the effective pitching action, were much better than those in region II, related to enhanced flow detachment. In addition,at the rated wind velocity, the control for the array case was superior over other three cases, which was thought to be originated from the more pitch activities to impair the uncontrolled flow separation on the blade surface.

Ni nanoparticles supported on carbon as efficient catalysts for the hydrolysis of ammonia borane

We report on the preparation of three kinds of Ni nanoparticles supported on carbon （Ni/C） and their application in the catalytic hydrolysis of ammonia borane （AB）. Three Ni/C catalysts were prepared from a Ni metal-organic framework （Ni-MOF） precursor by reduction with KBI-G calcination at 700 ℃ under Ar, and a combination of calcination and reduction, the products being denoted as Ni/C-1, Ni/C-2, and Ni/C-3, respectively. The structure, morphology, specific surface area, and element valence were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, nitrogen adsorption-desorption measurements, and X-ray photoelectron spectra （XPS）. The results demonstrate that Ni/C-1 is composed of amorphous Ni particles agglomerated on carbon, Ni/C-2 is characteristic of crystalline Ni nanoparticles （about 10 nm in size） supported on carbon with Ni oxidized on the surface, while the surface of the Ni particles in Ni/C-3 is less oxidized. The specific surface areas of Ni-MOF, Ni/C-1, Ni/C-2, and Ni/C-3 are 1239, 33, 470, and 451 m2·g-1, respectively. The catalytic hydrolysis of AB with Ni/C-3 shows a hydrogen generation rate of 834 mL-min^-1·g-1 at room temperature and an activation energy of 31.6 kJ/mol. Ni/C-3 shows higher catalytic activity than other materials, which can be attributed to its larger surface area of crystalline Ni. This study offers a promising way to replace noble metal by under ambient conditions. Ni nanoparticles for AB hydrolysis

The study of the active surface for CO oxidation over supported Pd catalysts

CO oxidation was investigated on various powder oxide supported Pd catalysts by temperature-programined reaction. The pre-reduced catalysts show significantly higher activities than the pre-oxidized ones. Model studies were performed to better understand the oxidation state, reactivities and stabilities of partially oxidized Pd surfaces under CO oxidation reaction condi tions using an in situ infrared reflection absorption spectrometer （IRAS）. Three O/Pd（100） model surfaces, chemisorbed oxygen covered surface, surface oxide and bulk-like surface oxide, were prepared and characterized by low-energy electron diffraction （LEED） and Auger electron spectroscopy （AES）. The present work demonstrates that the oxidized palladium surface is less active for CO oxidation than the metallic surface, and is unstable under the reaction conditions with sufficient CO.