Magnetic force distribution and deformation law of sheet using uniform pressure electromagnetic actuator

The distribution of magnetic forces and current on sheet and coil was analyzed in detail according to the structural parameter of the coil which was invalid.The result shows that the current direction based on simulation result agrees with the principles of uniform pressure electromagnetic actuator.The reason for coil failure was proposed.Then the magnetic forces on the sheet were input into an explicit finite element software ANSYS/LS-DYNA to analyze the deformation law of the sheet.

Intelligent power factor compensation equipment of three phase low voltage loads

An intelligent power factor correction scheme is presented for three phase low power factor loads. This new scheme is able to perform individual phase sensing of parameters by monitoring at all times to sense a change in system parameters and affects individual phase correction by applying the exact amount of reactive components needed for each phase, and can also reduce negative sequence current caused by the load to improve system balance. An optimization criterion is used for the proper calculation of reactive power steps in a power compensation installation of capacitor banks. The criterion is enabled by sampling measurements performed on the electrical plant examined within specific interval of time.

Modeling of Arc Force in Plasma Arc Welding

A three-dimensional mathematical model for the transferred-type argon arc was developed to describe arc force on the anode surface. The software ANSYS was employed to solve the model. The model includes a part of torch and tungsten electrode to achieve more reasonable resuits. The arc temperature and flow fields were derived. And the influences of welding parameters on arc force were also studied. The simulated results show that arc pressure at the anode are dependent on the welding current, plasma gas flow rate and electrode neck-in, while not sensitive to arc length.

Science Letters:Analytical solution for fixed-end beam subjected to uniform load

A bi-harmonic stress function is constructed in this work. Ariy stress function methodology is used to obtain a set of analytical solutions for both ends fixed beams subjected to uniform load. The treatment for fixed-end boundary conditions is the same as that presented by Timoshenko and Goodier (1970). The solutions for propped cantilever beams and cantilever beams are also presented. All of the analytical plane-stress solutions can be obtained for a uniformly loaded isotropic beam with rectangular cross section under different types of classical boundary conditions.

Piezoelectric responses of brittle rock mass containing quartz to static stress and exploding stress wave respectively

The electromagnetic emission(EME) induced from the rock containing piezoelectric materials was investigated under both static stress and exploding stress wave in the view of piezoelectric effect. The results show that the intensity of the EME induced from the rock under static stress increases with increasing stress level and loading rate; the relationship between the amplitude of the EME from the rock under different modes of stress wave and elastic parameters and propagation distance was presented. The intensity of the EME relates not only to the strength and elastic moduli of rock masses,but also to the initial damage of the rock. The intensity of EME induced by stress wave reaches the highest at the explosion-center and attenuates with the propagation distance. The intensity of EME increases with increasing the elastic modulus and decreases with increasing initial damage. The results are in good agreement with the experimental results.

SVR-Boosting ensemble model for electricity price forecasting in electric power market

A revised support vector regression (SVR) ensemble model based on boosting algorithm (SVR-Boosting) is presented in this paper for electricity price forecasting in electric power market. In the light of characteristics of electricity price sequence, a new triangular-shaped 为oss function is constructed in the training of the forecasting model to inhibit the learning from abnormal data in electricity price sequence. The results from actual data indicate that, compared with the single support vector regression model, the proposed SVR-Boosting ensemble model is able to enhance the stability of the model output remarkably, acquire higher predicting accuracy, and possess comparatively satisfactory generalization capability.

Modeling of sensor function for piezoelectric bender elements

An analytical sandwich beam model for piezoelectric bender elements is derived based on the first-order shear deformation theory (FSDT), which assumes a single rotation angle for the whole cross-section and a quadratic distribution for coupled electric potential in piezoelectric layers. Shear coefficient is introduced to correct the effect of transverse shear strain on shear force and the electric displacement integration. Static and free vibration analyses of simply-supported bender elements are carried out for the sensor function. The results illustrate the high accuracy of the present model compared with the exact 2D solutions.

China Needs Prompt Construction of a Strong National Power Grid (Excerption)

China needs to develop a strong national power grid which takes ultra-high-voltage (UHV) transmission systems as its core. The grid is expected to adopt 1000-kV-class AC and ± 800-kV DC transmission systems. In view of significant achievements in technological research and considerable progress in UHV manufacturing technology, China is capable of developing UHV systems. In order to promote the construction of UHV systems,China Electric Power Research Institute and other institutions have initiated first-phase research activities of UHV transmission technologies. The main contents involve research on UHV transmission technology and its economy,developing and manufacturing abilities on UHV equipment, prospective of UHV network frame and selection of demonstration projects, etc.

Dynamic Characteristic Investigation on the Fuel Pressure of Diesel Engines Electronic In-line Pump System

The electronic in-line pump (EIP) is a complex system consisting of mechanical, hydraulic, and electromagnetic parts. Experimental study showed that the fuel pressure of the plunger and the fuel drainage of the pressure system after fuel injection could result in fuel pressure fluctuation in the low pressure system. Such fluctuation exhibited pulsating cycle fluctuation as the amplitude rose with the increase of the injection pulse width. The time domain analysis found that the pressure time history curve and injection cylinders corresponded with a one-to-one relationship. By frequency domain analysis, the result was that with the increase of the working cylinder number, the high frequency amplitude gradually increased and the basic frequency amplitude gradually decreased. The conclusion was that through wavelet transformation, the low pressure signal simultaneously moved towards low frequency as the high frequency of the wavelet transformation signal with the working cylinder number increased. Lastly, by using the numerical model, the study investigated the simulation research concerning the relationship of the fluctuation dynamic characteristic in the low pressure system and the fuel injection characteristic of the high pressure system, completing the conclusions obtained by the experimental study.

《锅规》与《电锅规》统一的探讨

该文对《蒸汽锅炉安全技术监察规程》(1996年版)(以下简称《锅规》)和DL612 1996《电力工业锅炉压力容器监察规程》(以下简称《电锅规》)同时实施的现状所引起的问题进行了叙述;从性质和内容上探讨了"两规"统一的可行性;着重对照了"两规"的部分内容,并探讨了统一可能出现的问题,从技术角度进行了分析,以科学合理为原则提出了建议。

A Tool for the Assessment of the Electromagnetic Forces in Power Distribution Transformers

This paper compares the estimated electromagnetic forces due to short circuits in power transformers using two computational models. The first model is based on approximate analytical expressions of the electromagnetic lbrces as they have been compiled in earlier versions of the IEC standard 60076-5. The second model is based on a finite element model of the transformer using the software FEMM （Finite Element Method Magnetics）. The paper shows how valid the analytical model is for design purposes. Results have been obtained and compared from both models in a number of actual power distribution transformers. It is possible to conclude that the analytical formulation provides satisfactory results for the design of power transformers compared to detailed finite element models. A tool has been designed for this purpose and the main features of it will be described in the paper.

Pressure Tolerant Power Electronics： IGBT Gate Driver for Operation in High Pressure Hydrostatic Environment

Abstract： This paper presents results from an on-going research project on pressure tolerant power electronics at SINTEF Energy Research, Norway. The driving force for this research is to enable power electronic components to operate in pressurized dielectric environment. The intended application is the converters for operation down to 3,000 meters ocean depth, primarily for subsea oil and gas processing. The paper focuses on the needed modifications to a general purpose gate driver for IGBT （insulated gate bipolar transistors） that will give pressure tolerance. Adaptations and modifications of the individual driver components are presented.The results from preliminary testing are promising, which shows that the considered adaptations give feasible solutions.

面貌相似 内容类同的两个锅炉规程给企业带来的困惑

《蒸汽锅炉安全技术监察规程》（以下简称《蒸规》）与《电力工业锅炉压力容器监察规程》（以下简称《电规》），性质都是强制性的规程，目的都是为了保证锅炉及其系统的安全运行，内容都是有关锅炉从设计、制造、安装、运行、检验、修理和改造等方面的要求。一个是国家规程，一个是行业规程。规程也是标准的一种形式。行业规程理应服从国家规程，两者可以说是执行同一任务的上下级关系，本不应该有矛盾、分歧。

《蒸规》与《电规》在锅炉制造上的主要差异

目前，锅炉制造企业在签锅炉销售合同技术协议中，经常有用户要求必须同时满足《蒸汽锅炉安全技术监察规程》（以下简称（《蒸规》）和DL612—1996《电力工业锅炉压力容器监察规程》（以下简称《电规》）的要求。但是上述两规程所涉及到的标准各有不同的要求。使得锅炉制造行业无所适从。下面笔者仅对两规程的适用范围及制造要求做比较，希望对技术协议的签订和执行有所帮助。

Validation of DFIG and PMSG Wind Turbines' LVRT Capabilities Through Real Field Tests

Low voltage ride through (LVRT) capability has become more and more an issue for newly integrated wind turbines. The LVRT programs described in this paper developed field tests for newly installed wind turbines on wind farms in Northeast China. It is therefore different from other papers that only validate LVRT control strategies through running computer software simulations. To examine a single wind turbine's LVRT capability, the wind turbine's terminal voltage dip was realized by using a grid voltage dip emulator, which was located on the 690 V side of the generator transformer. In this paper, by artificially making various grid faults, the dynamic behavior of DFIG and PMSG wind turbines are analyzed and compared, control strategies such as active/passive crowbar and chopper protection schemes are verified, and new active/reactive power compensation methods are investigated and compared.

Analysis and Simulation of a Crowbar Protection for DFIG Wind Application during Power Systems Disturbances

The performance of a 1.5 MVA wind-power Doubly Fed Induction Generator （DFIG） under network fault is studied using simulator developed in MATLAB-SIMULINK. This paper investigates a new control method able to improve the fault-ride through capability of DFIG. In such generators the appearance of severe voltage sags at the coupling point make highlight important over currents at the rotor/stator windings, making the use of crowbar protection device necessary and inevitable in order to protect the machine as well as the rotor side power converter. The simulator consists of the DFIG analytical model, power transformer model and the detailed frequency converter model including crowbar protection device. Simulation results are carried out to show the transient behavior of the DFIG when a sudden voltage dip is introduced with and without the crowbar implementation.

Considerations of Electricity Supply Quality in Spain

The quality of supply in Spain is regulated by Act 54/1997 as the basic standard and further developed by Royal Decree 1955/2000, among others. Also this law （1997） introduces the division between generators, distribution companies and retailers. The aim of this paper is to provide an overview of the fundamental parameters to be taken into account when examining the status of national regulations in Spain on the quality of electricity supply, in addition to describing the various agents intervening in these. There are two more aspects to consider： the guarantee of supply and energy is provided at the lowest cost to consumers. The authors propose to include phase-shifting transformers at specific strategic points, in accordance with power flow control principles in parallel circuits. Finally, it can be concluded that Royal Decree 222/2008 needs reviewing and applying effectively, as do modifications to Royal Decree 1995/2000 providing remuneration that effectively induces electricity companies to invest in their networks, and ends with ＂a well-paid electricity company is obliged to invest in network improvements＂.

Application of fuzzy analytic hierarchy process and neural network in power transformer risk assessment

In operation,risk arising from power transformer faults is of much uncertainty and complicacy.To timely and objectively control the risks,a transformer risk assessment method based on fuzzy analytic hierarchy process(FAHP) and artificial neural network(ANN) from the perspective of accuracy and quickness is proposed.An analytic hierarchy process model for the transformer risk assessment is built by analysis of the risk factors affecting the transformer risk level and the weight relation of each risk factor in transformer risk calculation is analyzed by application of fuzzy consistency judgment matrix;with utilization of adaptive ability and nonlinear mapping ability of the ANN,the risk factors with large weights are used as input of neutral network,and thus intelligent quantitative assessment of transformer risk is realized.The simulation result shows that the proposed method increases the speed and accuracy of the risk assessment and can provide feasible decision basis for the transformer risk management and maintenance decisions.

规程要求不一致给监检工作带来的困难

劳动部劳部发[1996]276号《蒸汽锅炉安全技术监察规程》（以下简称《蒸规》）和DL612-1996《电力工业锅炉压力容器监察规程》（以下简称《电规》）都是强制性规程。《蒸规》第一章第四条规定：“本规程的规定是锅炉安全管理和安全技术方面的基本要求。有关技术标准的要求如果与本规程的规定不符时，应以本规程为准”。《电规》在前言中明确本规程是“指导电力工业锅炉压力容器的安全工作的综合性管理规程，是强制性行业标准”。由此可见。这2个规程的权威性和地位。