Voltage and frequency control of parallel operated synchronous generator and induction generator with STATCOM in micro hydro scheme

Parallel operation of synchronous and induction generators in micro hydro scheme is presented. The synchronous generator has an exciter, which provides a fixed excitation to produce normal rated terminal voltage at full resistive load. On the other hand, the induction generator has neither exciter nor speed controller. Static compensator (STATCOM) is connected to the common bus for terminal voltage and frequency control. A resistive dump load is connected across the DC link capacitor of STATCOM through a chopper to control active power. Simulink model is developed to perform transient analysis of the proposed scheme. Experimental results are presented to compare with the simulation results. It is found that connection of an induction generator in parallel with the synchronous is much simpler than connecting two synchronous generators in parallel.     

同步发电机励磁系统中PWM控制的仿真研究

优良的励磁控制系统不仅可以保证发电机运行的可靠性和稳定性，而且可有效地提高发电机和电力系统技术指标。同步发电机励磁系统采用了PWM整流技术，实现励磁电流低谐波和励磁功率单元高功率因数转换，提高了发电机供电质量，并用MATLAB对设计系统做出仿真验证，证明该设计对改善发电机输出电压、提高功率单元电能利用率有明显效果。     

区域性能源管理中心平台建设(英文)简

Based on the analysis of different requirements of energy management center construction and the data acquisition of various industries in wide area network, as well as the practices of real-lime online system, the paper puts forward the construction scheme of regional energy management center （REMC） which can achieve real time online monitoring of organizations＇ energy consumption via data collection, and also proposes the design idea of energy data acquisition based on national standards.     

Advanced control for PWM converter and variable-speed induction generator

The paper describes a simple control structure for a vector-controlled stand-alone induction generator (IG) used to operate under variable speeds. Deadbeat current control is developed for a voltage source PWM converter and the three-phase variable speed squirrel-cage IG to regulate DC-link and generator voltages with newly designed phase-locked-loop circuit. The required reactive power for the variable-speed IG is supplied by means of the PWM converter and a capacitor bank to build up the voltage of the IG without the need for a battery and to reduce the rating of the PWM converter with the need for only three sensors. This proposed scheme can be used efficiently for variable speed wind or hydro energy conversion systems. The measurements of the IG system at various speeds and loads are given and show that this proposed system is capable of good AC and DC voltages regulation     

Minimization and identification of conducted emission bearing current in variable speed induction motor drives using PWM inverter

The recent increase in the use of speed control of ac induction motor for variable speed drive using pulse width modulation (PWM) inverter is due to the advent of modern power electronic devices and introduction of microprocessors. There are many advantages of using ac induction motor for speed control applications in process and aerospace industries, but due to fast switching of the modern power electronic devices, the parasitic coupling produces undesirable effects. The undesirable effects include radiated and conducted electromagnetic interference (EMI) which adversely affect nearby computers, electronic/electrical instruments and give rise to the flow of bearing current in the induction motor. Due to the flow of bearing current in the induction motor, electrical discharge machining takes place in the inner race of the bearing which reduces the life of the bearing. In high power converters and inverters, the conducted and radiated emissions become a major concern. In this paper, identification of bearing current due to conducted emission, the measurement of bearing current in a modified induction motor and to minimize the bearing current are discussed. The standard current probe, the standard line impedance stabilization network (LISN)), the electronics interface circuits are used to measure high frequency common mode current, bearing current and to minimize the conducted noise from the system. The LISN will prevent the EMI noise entering the system from the supply source by conductive methods, at the same time prevents the EMI generated if any due to PWM, fast switching in the system, will not be allowed to enter the supply line. For comparing the results with Federal Communications Commission (FCC) and Special Committee on Radio Interference (CISPR) standards, the graphs are plotted with frequency Vs, line voltage in dBμ V, common mode voltage in dBμ V and the bearing current in dBμ A with out and with minimizing circuits.     

Analytical Modeling to Predict the Strain Energy of Circular GLARE Fiber-Metal Laminates Under Lateral Indentation

This article deals with the strain energy calculation of thin circular clamped Glass Reinforced （GLARE） fiber-metal laminates subjected to static indentation by a lateral hemispherical indentor. Using one-, two- and three-parameter Ritz approximations, analytical equations of the strain energy as a function of the central plate deflection are derived. Previously published analytical formulas, concerning the load-indentation response of circular GLARE plates, are used in order to determine the Ritz parameters and the first failure load and deflection due to tensile fracture of glass-epoxy layers. In this study, the membrane and bending strain energy components of aluminum and prepreg layers are determined. Also, the elastic and plastic strain energy absorbed during the indentation loading are calculated. The derived formulas are applied successfully for GLARE 2-2/1-0.3, GLARE 3-3/2-0.4 and GLARE 31 （special lay-up） circular plates subjected to lateral indentation. The strain energy results converge satisfactorily in all examined cases. The predicted strain energy-indentation response is compared with published experimental data and a good agreement is found. No other solution of this problem is known to the authors.     

永磁发电机在离网型风电系统中运行特性的测试分析

通过实验分析法,针对某400W风力发电的永磁同步发电机运行特性进行了测试和分析。为了能准确、有效地对发电机的特性参数进行综合测试,搭建了发电机特性综合测试系统平台,系统采取VVVF交交变频器自动控制的三相异步电动机直接驱动发电机的运转方式,并配备专业化的EDA9033G数据采集器和JW-1型扭矩仪,实现了对发电机电压、电流、频率、功率、转速、转矩等参数的实时监测、显示、存储等功能。依据实验所得数据,拟合了发电机空载特性、输出特性、效率特性、外特性及转矩特性曲线。通过分析各曲线,对该永磁同步发电机的性能做出了评价,并以提高离网型风电机组的风能捕获效率为依据,提出了永磁发电机应具有的最佳性能。     

A General Model for Investigating the Effects of the Frequency Converter on the Magnetic Iron Losses of a Squirrel-Cage Induction Motor

We present a comprehensive analysis of iron losses in an inverter-fed induction motor. We performed experimental and numerical investigations to assess the additional losses produced by a pulsewidth modulated (PWM) supply compared to a sinusoidal supply. We developed an iron-loss model, called the hybrid model, and incorporated it into a two-dimensional (2-D) finite-element method (FEM) to investigate the losses. The model predicts the $Bhbox{-}H$ loops and the ensuing iron losses. We also used a traditional iron-loss model based on the statistical theory for the sake of comparison. We solved the nonlinear dynamic equations of the FEM by the fixed-point method and the Crank-Nicolson time-stepping scheme. We found the hybrid model to be fairly accurate in reproducing the iron losses obtained experimentally on a squirrel-cage induction motor operated under several different conditions. The numerical analysis also provided interesting results regarding the role of the PWM supply in characterizing the behavior and distribution of iron losses in the geometry of the motor.      

能源管理体系标准体系构建与发展研究(英文)简

Energy Management System （EnMS）, benefiting enterprises with energy conservation through the PDCA cycle, has been widely valued and applied by domestic and overseas enterprises. Based on the experience on the construction and implementation of energy management system, the paper systematically analyzes the construction ideas and development requirements of EnMS standards system, aiming to broaden/he coverage of EnMS and its technical indicator system, strengthen the systematicness and comprehensiveness and provide standardized tools and methods for all users.     

MCNPX Modeling of BN-600 Full MOX Fast Reactor Core

The BN-600 full mixed oxide fueled core is modeled using MCNPX code. A three dimensional model typical of the core is prepared which includes 6 radial zones, low enrichment zone, medium enrichment zone and high enrichment zone, two zones of steel shielding assemblies, and a radial blanket in addition to shim and scram rods. The twelve axial zones are also modeled. The model calculates core parameters such as reactor multiplication factor, power distribution through reactor core, and control rod worth. An estimation of isotope transmutation through various reactor zones and analysis of internal breeding zone were presented. The results are compared with previously published results which indicated good agreement. Typical results of the present model for reactor multiplication factor are !.00832 compared with transport model （1.00664） and diffusion model （1.00131）. The high enrichment zone dominates power production. The results also estimate the isotope variation due to burnup in the MOX core.     

Electrical parameter evaluation of a 1 MW HTS motor via analysis and experiments

A 1 MW class HTS (high-temperature superconducting) synchronous motor has been developed. Design concerns of the developed motor are focused on smaller machine size and higher efficiency than conventional motors or generators with the same rating simultaneously reducing expensive Bi-2223 HTS wire which is used for superconducting field coil carrying the operating current around 30 K (−243 °C). Influence of an important parameter, synchronous reactance, has been analyzed on the machine performances such as voltage variation and output power during motor and generator operation. The developed motor was also analyzed by three-dimensional electromagnetic FEM (finite element method) to get magnetic field distribution, inductance, electromagnetic stress and so forth.This motor is aimed to be utilized for industrial application such as large motors operating in large plants. The HTS field coil of the developed motor is cooled by way of Neon thermosiphon mechanism and the stator (armature) coil is cooled by water through hollow copper conductor. This paper also describes evaluation of some electrical parameters from performance test results which were obtained at steady state in generator and motor mode of our HTS machine.     

Novel maximum-power-extraction algorithm for PMSG wind generation system

The paper focuses on the development of a novel maximum-power-extraction algorithm (MPEA) including a maximum-power error-driven (MPED) mechanism and a maximum-power differential-speed (MPDS) control, for a wind generation system with a permanent-magnet synchronous generator (PMSG). In the proposed MPEA scheme, the MPED mechanism, operating like a traditional hill-climbing method, drives the output power gradually increasing to its maximum value by regulating the direction of current command according to the power variation trend. The MPDS control produces an additional step of current command based on the instantaneous difference of generator speeds, so that it can prevent the wind turbine from stalling at the suddenly dropping wind speed and achieve the object of maximum power extraction instantly as a stiff wind flowing through the wind turbine. In addition, the output is connected to a utility grid for providing energy flexibility via a unipolar full-bridge inverter controlled by a digital signal processor. The grid-connected experimentations of the proposed MPEA scheme, without any mechanical sensors for a wind-power emulation system via a PMSG driven by an induction motor, are given to examine its feasibility in practical applications     

Few-Layer Graphene Modified by Bridge-Like Defects as Li-Storing Cells

The paper presents some results of computer simulations and density functional theory calculations of the energetic and structural characteristics of few-layer graphene nanostructures as storing cells for Li. Modeling and calculations allow to reveal some peculiarities in such systems, which can be considered as causes of known dimension instabilities and shortening of the life-time of Li- based electrical power devices. Results of the computational study and calculations predict, that all these problems can be in significant measure solved by modifying of few-layer graphene nanostructures by bridge -like defects, which make them much more stiffer and stable against the deformation.     

水泥行业能源管理体系标准进展及实施探索(英文)简

The energy-saving management of China＇ s cement industry has gradually improved in recent years; however, cement industry still faces big pressure of facilitating energy conservation and emission reduction. Based on the current development of cement industry, the paper summarizes and analyzes the application and promotion of energy management system （EnMS） standardization in cement industry, then gives a brief introduction to the implementation of related standards and at last explores the positive function of energy management system in enhancing enterprises＇ energy management and improving energy performance.     

钢铁行业能源管理体系实施指南(英文)简

The iron and steel industry generally features the characteristics of large volume of energy consumption, multiple sorts of energy medium, complex secondary conversion, more recyclable extra energy, and the energy management of the field may involve the entire personnel, process and system, covering all links from designing, purchasing, energy storage, processing and conversion, distribution, energy use and extra energy recycling. The implementation guidelines summarizes the energy management experience and results and provide a systematic approach for the implementation of GB/T 23331-2012 and GB/T 29456-2012, sharing svstematic instructions and suggestions for the implementing paths and methods of creating, implementing, maintaining and improving the energy management system （EnMS） at the enterprise level.     

Energy Scavenging From Low-Frequency Vibrations by Using Frequency Up-Conversion for Wireless Sensor Applications

This paper presents an electromagnetic (EM) vibration-to-electrical power generator for wireless sensors, which can scavenge energy from low-frequency external vibrations. For most wireless applications, the ambient vibration is generally at very low frequencies (1-100 Hz), and traditional scavenging techniques cannot generate enough energy for proper operation. The reported generator up-converts low-frequency environmental vibrations to a higher frequency through a mechanical frequency up-converter using a magnet, and hence provides more efficient energy conversion at low frequencies. Power is generated by means of EM induction using a magnet and coils on top of resonating cantilever beams. The proposed approach has been demonstrated using a macroscale version, which provides 170 nW maximum power and 6 mV maximum voltage. For the microelectromechanical systems (MEMS) version, the expected maximum power and maximum voltage from a single cantilever is 3.97 muW and 76 mV, respectively, in vacuum. Power level can be increased further by using series-connected cantilevers without increasing the overall generator area, which is 4 mm². This system provides more than an order of magnitude better energy conversion for 10-100 Hz ambient vibration range, compared to a conventional large mass/coil system.     

Research into Excited Long Lived 0.6-6.0 keV Energy Levels in the Cathode Solid Medium of Glow Discharge by X-Ray Spectra Emission

X-ray emissions have been registered in experiments with high-current glow discharge from the different cathode and different plasma forming gases within 100 ms and more after turning off the current. The emission X-rays was realized： in the form of laser microbeams （up to 104beams a second and up to 10^10 X-ray of quanta in a beam, angular divergence was up to 10-4）, The fine structure of X-ray spectra were detected using a bent mica crystal X-ray spectrometer and recorded on X-ray film after the discharge current switching off （during up to 20 h afterwards）. The X-ray energy was 0.8-6.0 keV. The possible mechanism and phenomenon model of producing the X-ray emission on the solid medium cathode with the exited energy levels was considered.     

提高同步电机抗电网电压波动能力的成功实践

60000 m3/h空分设备空压机因同步电机抗电网电压波动能力差而跳车,影响氧、氮、氩产品的安全生产和稳定供应。将常用励磁电源改为UPS稳压电源后,大大提高了同步电机抗电网电压波动的能力。介绍供电电源优化改造前同步电机的运行状况,阐述优化改造的理论依据和具体改造方案。     

风力发电并网系统次同步振荡研究

大规模风力发电并网引发的次同步振荡（subsynchronous oscillation,SSO）问题已严重威胁到电网的安全稳定运行。由于电力电子设备的广泛采用,风电参与的新型次同步振荡的产生机制和作用形态均与传统次同步振荡不同,其中双馈风电场经串补并网和直驱风电场并入弱电网2种场景下出现的次同步振荡问题引起了国内外广泛的关注。首先总结了目前常用的分析方法及其适用性,然后基于典型的工程案例,梳理了近年来风电次同步振荡建模、分析、控制和保护方面取得的理论成果和工程进展,为今后风电次同步振荡的研究提供参考。     

A nine-level hybrid symmetric cascaded multilevel converter for induction motor drive

A nine-level hybrid symmetric cascaded multilevel converter (MLC) fed induction motor drive is proposed in this paper. The proposed converter is capable of producing nine output voltage levels by using the same number of power cells as that of conventional five-level symmetric cascaded H-bridge converter. Each phase in this configuration consists of one five-level transistor-clamped H-Bridge (TCHB) power cell and one three-level H-bridge power cell with equal dc link voltages, and they are connected in cascade. Due to cascade connection and equal dc link voltage, the power shared by each power cell is nearly equal. Near-equal power sharing enables the feature of improving input current quality by using an appropriate phase-shifting multi-winding transformer at the converter input. In this paper, the operation of the converter is explained using staircase and hybrid multi-carrier sine PWM techniques. Further, a detailed analysis for the variations in the dc link capacitor voltages and the dc link mid-point voltage in TCHB power cell is carried out, and the analytical expressions thus obtained are presented. The performance of proposed system is analysed by simulating a 500 hp induction motor drive system in MATLAB/Simulink environment. A laboratory prototype is also developed to validate the claims experimentally.