高压输电线路可听噪声空间传播计算模型(英文)

Audible noise from high voltage transmission lines’ corona discharge has become one of the decisive factors affecting design of high voltage transmission lines, thus it is very important to study the spatial propagation characteristics of audible noise for its accurate pre- diction. A calculation model for the propagation of audible noise is presented in this paper, which is based on the basic equation of the sound wave and can involve the influences of the atmosphere absorption and ground effects. The effects of different ground impedances and the atmospheric attenuation on the distribution of sound pressure level are discussed in this paper. The results show that the atmospheric absorp- tion may increase the attenuation of the audible noise, and the ground surface affects both the amplitude and phase of the sound. The spatial distribution fluctuates considering the ground effects. The atmospheric attenuation and the ground effect are closely related to the frequency of the noise. In the frequency range of the audible noise, the influence of atmospheric attenuation on the spatial propagation characteristics is more obvious in high frequency while ground has significant influences in low frequency.     

A Review of Power Electronics for Wind Power

The paper reviews the power electronic applications for wind energy systems.Main wind turbine systems with different generators and power electronic converters are described.The electrical topologies of wind farms with power electronic conversion are discussed.Power electronic applications for improving the performance of wind turbines and wind farms in power systems have been illustrated.     

惰性气体对氧气介质阻挡放电臭氧生成的影响(英文)

This paper reports the results of an experimental study of the effect of inert gases He,Ar and Kr on ozone generation in a Dielectric Barrier Discharge(DBD) fed by pure oxygen.The chemical reaction mechanisms related to the process of ozone generation are discussed.The experimental results show that ozone concentration decrease with decreasing oxygen content in all He+O2,Ar+O 2 and Kr+O 2 mixtures mainly owing to the decrease of oxygen content.The conversion ratio of oxygen into ozone increases with increasing oxygen content in He+O2 mixtures,but the addition of Ar and Kr can improve the conversion ratio due to the increase of free electrons density and excited oxygen molecules required for ozone formation through ionization and Penning effect.The effect of Kr is more significant for the lower first ionization energy of metastable state compared with other gases.It is probable that the ozone concentration,and ozone production efficiency increase with Kr addition when the reduced electric field and mean electron energy are high enough.     

中功率激光器驱动电路的研究与设计

In order to improve the performance of the antenna at low frequency, short circuit branch and coupling feed structure are introduced into the folded broadband single antenna in this paper, then resonant frequency is merged into the antenna using method of stagger tuning, finally, a UWB antenna is designed to work between 800MHz～2700MHz. Analysis are conducted to determine the antenna’s properties. The short-circuit wire location, feeding point location and the length of folded strip are discussed in detail. The SAR is calculated by HFSS simulation software while the antenna is close to a 3D human head model. The research results show that the antenna can cover eight commonly used commercial frequency bands at present, and electromagnetic radiation of the antenna has tiny influence on the human head model.     

Study on the Characteristics of the Gas Switch Electrode Erosion

Gas spark switch is one of the key parts in pulsed power technology.Electrode erosion has great influence on the switch performance and lifetime.In this paper,a field distortion gas switch is selected for the experiment and a great deal of discharging experiments have been conducted in different test conditions.The forming process of etch pit as well as its influencing factors is discussed briefly and surface roughness coefficient(SRC) of the electrode is put forward to evaluate the state of electrode erosion.Experimental results show that current peak plays an important role in electrode erosion when waveforms of discharge current are the same,and electric charge and oscillation frequency of discharge current also have great effect on the electrode erosion when waveforms of discharge current are different.With the increase of discharge times,SRC decreases slowly at first and then decreases quickly after three thousand of discharge times.     

混响室频率搅拌技术研究（英文）

The radio frequency(RF)modes of reverberation chamber(RC) in different frequency ranges are calculated to develop frequency-stirring techniques for RCs.An experimental system is built with a two-port vector network analyzer,of which one port is connected to a transmitting antenna located in a corner of a RC,and the other port is connected to a receiving antenna located in the working area of the RC.The parameter S21 is obtained in eight different locations of the receiving antenna for discussing the number of RF modes and the stirring bandwidth.It is found that the lowest useable frequency of a RC is determined by the RC’s dimension:the larger the dimension is,the lower the lowest useable frequency is.S21 at the lowest useable frequency is about-20 dB,and it is more stable than that at lower frequencies when the frequency increases.Increasing the bandwidth would result in a smoother dependence of S21 on frequency,which shows that frequency stirring is effective.In a RC with frequency stirring,the standard deviations of three individual field components and the total field are within the specified tolerance,i.e.the electric field distribution is uniform.Meanwhile,the electric field’s magnitude is characterized by the Chi-distribution with two degrees of freedom or the Rayleigh distribution,and the square of the magnitude is characterized by the Chi-square distribution with two degrees of freedom or the exponential distribution.Therefore,both good uniformity and good behavior of the electric field can be obtained if the RF modes in the RC are sufficient.     

Time–frequency multiresolution of fault-generated transient signals in transmission lines using a morphological filter

The ongoing transformation of electrical power systems highlights the weaknesses of the protection schemes of traditional devices because they are designed and configured according to traditional characteristics of the system. Therefore, this work proposes a new methodology to study the fault-generated high frequency transient signals in transmission lines through multiresolution analysis. The high frequency components are determined by a new digital filtering technique based on mathematical morphology theory and a spectral energy index. Consequently, wide spectra of signals in the time–frequency domain are obtained. The performance of this method is verified on an electrical power system modeled in ATP-Draw, where simulation and test signals are developed for different locations, fault resistances, inception angles, high frequency noises, sampling frequencies, types of faults, and shapes of the structuring element. The results show the characteristics of the fault such as the traveling wave frequency, location, and starting time.     

向家坝—上海±800kV特高压直流输电工程中直流电压分压器故障分析(英文)

Transient DC voltage measurement error has been observed several times ever since Xiangjiaba-Shanghai ±800 kV UHVDC project started its commercial operation.The measurement error causes considerable disturbances to the AC networks.By analyzing the time frequency record,simulating faults at different positions of the divider,and testing the gas in voltage dividers,the fault is located and then is proved to be some partial discharges inside DC voltage dividers.The reason of the internal flashes and the solution to the problem is also discussed in this paper.The conclusion is that instead of N2,SF6 should be used for the internal insulation of high voltage DC voltage dividers.     

基于变压器绕组中谐振过电压识别的传输函数

Power transformer insulation systems are subjected to many stresses during normal operation due to lightning and switching.If the spectrum of incoming surge voltage matches the winding one,the corresponding resonance will be excited.Therefore external transients occurring in power systems might trigger internal overvoltages with large maximum value in transformer windings.Overvoltages having such characteristic have been the root cause of many power transformer failures.The paper presents an approach to the identification of sensitive zones in the transformer windings based on the measurements of overvoltages inside windings and frequency dependences of admittance of the power transformer.The frequency characteristic of the transformer winding may determine those regions in the frequency spectrum.The presented approach might be used both for design optimization and diagnostics of distribution and power transformers.     

Impact of Shaft Stiffness on Inertial Response of Fixed Speed Wind Turbines

Future power system faces several challenges,one of them is the high penetration level of intermittent wind power generation,providing small or even no inertial response and being not contributing to the frequency stability.The effect of shaft stiffness on inertial response of fixed speed wind turbines is presented.Four different drive-train models based on the multi-body system are developed.The small-signal analysis demonstrates no significant differences between models in terms of electro-mechanical eigen-values for increasing shaft stiffness.The natural resonance frequency of drive-train torsion modes shows slightly different values between damped and undamped models,but no significant differences are found in the number-mass models.Time-domain simulations show the changes in the active power contribution of a wind farm based on a fixed speed wind turbine during the system frequency disturbance.The changes in the kinetic energy during the dynamic process are calculated and their contribution to the inertia constant is small and effective.The largest contribution of the kinetic energy is provided at the beginning of the system frequency disturbance to reduce the rate of the frequency change,it is positive for the frequency stability.     

A cost accounting method of the Li-ionbattery energy storage system forfrequency regulation considering the effectof life degradation

The cost of Energy Storage System (ESS) for frequency regulation is difficult to calculate due to battery’s degradation when an ESS is in grid-connected operation. To solve this problem, the influence mechanism of actual operating conditions on the life degradation of Li-ion battery energy storage is analyzed. A control strategy of Li-ion ESS participating in grid frequency regulation is constructed and a cost accounting model for frequency regulation considering the effect of battery life degradation is established. The estimated operating life and annual average cost of the Li-ion ESS under different dead bands and SOC set-points are calculated. The case studies show that the estimated operating life of the Li-ion ESS under the actual operating condition differs significantly from the nominal life provided by the manufacturer under the standard condition and the full discharge mode. This paper provides an accurate costing method for the ESS participating in grid frequency regulation to help the promotion of the ESS to participate in the ancillary service market.     

A cost accounting method of the Li-ion battery energy storage system for frequency regulation considering the effect of life degradation

The cost of Energy Storage System (ESS) for frequency regulation is difficult to calculate due to battery’s degradation when an ESS is in grid-connected operation. To solve this problem, the influence mechanism of actual operating conditions on the life degradation of Li-ion battery energy storage is analyzed. A control strategy of Li-ion ESS participating in grid frequency regulation is constructed and a cost accounting model for frequency regulation considering the effect of battery life degradation is established. The estimated operating life and annual average cost of the Li-ion ESS under different dead bands and SOC set-points are calculated. The case studies show that the estimated operating life of the Li-ion ESS under the actual operating condition differs significantly from the nominal life provided by the manufacturer under the standard condition and the full discharge mode. This paper provides an accurate costing method for the ESS participating in grid frequency regulation to help the promotion of the ESS to participate in the ancillary service market.     

A cost accounting method of the Li-ion battery energy storage system for frequency regulation considering the effect of life degradation

The cost of Energy Storage System (ESS) for frequency regulation is difficult to calculate due to battery’s degradation when an ESS is in grid-connected operation. To solve this problem, the influence mechanism of actual operating conditions on the life degradation of Li-ion battery energy storage is analyzed. A control strategy of Li-ion ESS participating in grid frequency regulation is constructed and a cost accounting model for frequency regulation considering the effect of battery life degradation is established. The estimated operating life and annual average cost of the Li-ion ESS under different dead bands and SOC set-points are calculated. The case studies show that the estimated operating life of the Li-ion ESS under the actual operating condition differs significantly from the nominal life provided by the manufacturer under the standard condition and the full discharge mode. This paper provides an accurate costing method for the ESS participating in grid frequency regulation to help the promotion of the ESS to participate in the ancillary service market.     

SIMULATION OF EMERGENCY CONTROL MEASURES AND THEIR EFFECTS ON PROBABILISTIC ASSESSMENT OF TRANSIENT STABILITY

Multiple emergency control measures (ECMs) such as fast valve control (FV), generator shedding (GS), under frequency load shedding (UFLS), under voltage load shedding (UVLS) and interior control measures of DC system etc are simulated, and the effects of ECMs on the risk indices of probabilistic transient stability of hybrid AC/DC power systems are discussed in detail. The statistical results of the modified EPRI 36bus system are investigated and compared. It is shown that different ECMs may have positive or negative effects on the transient stability under different conditions or parameters. And it also shows the necessity of optimizing and coordinating among ECMs.     

甚高频对大气压Ar/SiH4/H2混合等离子体粒子密度分布影响的数值模拟（英文）

To improve the microcrystalline silicon thin film deposition in quality and to increase its microcrystalline silicon content,we numerically investigated the characteristics of homogeneous discharges in hydrogen diluted silane and argon mixed gases at atmospheric pressure using a two-dimensional fluid model.The model takes into account the primary processes of excitation and ionization,sixteen reactions of radicals with radicals in silane/hydrogen/argon discharges,so this model can adequately describe the discharge plasma.The effects of very high frequency(VHF)excitation on the electron density in such discharges are analyzed.The simulation results show that the electron density does not linearly vary with the excitation frequency within from 90150 MHz.he maximum value occurs at an appropriate excitation frequency i.e.the transition frequency.Increasof the excitation frequency would effectively increase the electron density before the transition frequency,but decreases the density afterwards.is.Moreover,the densities of involved particle species,including H2+,H,Ar*,Ar+,SiH3+,SiH3,SiH3,SiH2are closely interrelated.     

NI立足测试测量，助力5G

The SI “second” is realized by caesium primary frequency standards (PFSs) using laser cooled atoms in a fountain configuration. Four sub systems and operation procedure of the NTSC-F1 primary frequency standard are introduced in the paper. The frequency stability of NTSC-F1 is 3.0×10-13/τ-1/2 compared to hydrogen maser. Four terms of frequency shift and uncertainty including second order Zeeman frequency shift, cold collision shift, gravity shift and blackbody shift are evaluated. The improvement of NTSC-F1 is introduced.     

Power frequency testing transformer type YDJC-9000/2250

Power frequency testing transformer typeYDJC-9000/2250 made in Shenyang Trans-former Works,is the power frequency testingdevice of the biggest capacity and the highestvoltage up to the present time.It plays an impor-tant part in the fields of improvement of 500 kVpower transmission equipments and provides thetest condition for 1000 kV electrical device incontaminated flash over,corona disturbance andelectrostatic induction etc.In April 1985,whencascade test carrying on in Wuhan,the voltage     

基于时频组合的强脉冲电磁场测试方法研究（英文）

Many conventional methods of testing strong and pulsed electromagnetic fields,the ones used in radars for example,had deficiencies due to the difficulty in obtaining simultaneous information about the electromagnetic field’s peak both in the time domain and in the frequency domain.With regard to this problem,after analyzing the time-domain and the frequency-domain characteristics of radar pulsed signals,we propose a new time-frequency combination test method based on the correction of the test parameters,as well as its correction method at different bandwidths.The test method is applied in a quick test of a high-power pulsed radar signal,and the corrected results have error less than 1 dB in both the time domain and the frequency domain,which indicates that the proposed time-frequency combined method is effective in testing strong and pulsed electromagnetic fields.     

Difficulties and Solutions for Desulphurization of Thermal Power Plants in China

As coal is the most important primary energy in China, SO2 , the main pollutant of coal-fired power plantsseriously pollutes the environment in the course of energy utilization and conversion. Flue gas desulphurization is inevitable in China, however, it is rather difficult to reach the stipulated standards without any compulsory administrative measures of the government. What are the exact difficulties and solutions for the desulphurization in power plants?     

A Real-time EMF Measuring System for Mobile Communication Towers in Sri Lanka

Telecommunications Regulatory Commission of Sri Lanka is the governing body which is responsible for the frequency allocation and monitoring the unauthorized Electromagnetic frequency (EMF) signal transmitting violations. However, in Sri Lanka, currently there is not any proper mechanism to monitor the radiation hazard level and its impact to the people living in the vicinity of mobile communication towers. There are approximately 7000 mobile transmitting towers in Sri Lanka to date and the used frequency range lies between 900MHz to 3GHz for mobile communication. Over the last few decades, many of the health hazard conditions were reported due to the radiation of those harmful EMFs. To cater this problem, a portable real time EMF signal strength measuring system with a radiation hazard level indicator was developed to monitor the EMF level and its impact. The proposed system operates with three intermediate frequency bands (i.e.900MHz, 1800 MHz and 2400MHz) and it’s capable of measuring the power density and the radiation hazard level at that particular point which is being measured. Moreover, the corresponding radiation hazard level is indicated with reference to the standard power density levels published by the International Commission on Non-Ionizing Ra-diation Protection (ICNIRP*). The system works with the overall accuracy of 88% in terms of identifying the power densities and its corresponding radiation hazard levels.