Dynamic responses of ultra high voltage transmission line ice shedding

Numerical models of typical 500 kV ultra high voltage (UHV) transmission lines are set up in ABAQUS/CAE software. The dynamic response of the transmission lines with different structure parameters under various ice shedding load cases are analyzed, and th     

Analysis of the distorted scaling factor in wind tunnel modeling of power transmission line system

Because of the limitation of the model making and the existing wind tunnel’s size, it is difficult to keep the line and tower in the same scaling factor in developing the aeroelastic model of the power transmission lines system, and a distorted scaling factor is needed in span length of the lines. With the instance of a 1 000 kV two circuit power transmission lines, the finite element analysis under the along wind load in time history is conducted with keeping the tower in the same and the line scaling factor being 1, 0.5 and 0.25 respectively. The results show that the response of the power transmission lines systems keep in the same, and then the wind induced vibration of the distorted model in the wind tunnel test can actually reflect the response of the power transmission lines system under the wind load.     

An optimal equivalent subchannel algorithm for low voltage power line communication system

According to the low voltage power line channel features,combined with adaptive bit loading and power allocation algorithm,an optimal equivalent subchannel algorithm is proposed.Under the condition of fixed amount of transmitted bits and the minimum transmitted power model,impact of optimal equivalent subchannel on the system performance is studied.The optimization algorithm sorts subchannels with similar transmission features into groups,thus the signaling load can be reduced,and the spectrum can be better used.The simulation results show that system can get lower bit error rate(BER) by adopting optimal equivalent subchannel algorithm.     

从输电阻塞角度建立的风电场容量可信度模型

风电并网时既要考虑系统的可靠性又要考虑输电阻塞。目前风电场容量可信度仅从可靠性单一角度提出。为此从输电阻塞角度提出了风电场容量可信度的定义;通过Monte Carlo法建立计及元件故障(发电机、线路和变压器)的风电场容量可信度模型,并提出该模型的二分法求解算法;同时还提出了风电阻塞指标以描述风电场并入电力系统对缓解系统输电阻塞的贡献。通过对修改的IEEE-RTS进行算例分析,验证了方法的正确性和实用性。结果表明：系统阻塞状况的缓解程度与并入风电场的位置有关,风电场容量可信度和风电阻塞指标相结合可以评价风电场并网对系统阻塞状况改善的有效性和经济性。     

Dynamic optimization design of gear transmission system for wind turbine

The differential equation which governs the behavior of the gear transmission system of 1.5 MW wind turbine is established. The external excitation caused by wind speed fluctuation is discussed and the internal excitation due to time varying mesh stiffness and comprehensive error is also analyzed. The calculating formulations of the harmonic balance method of nonlinear dynamic equations are presented. Then, the multi objective dynamic optimization model is developed to minimize the value of vibration acceleration and the overall volume. The optimization of a practical example using mixed discrete combined programming is performed. The result shows that the proposed method of modeling and optimization design can effectively reduce the wind turbines gearbox vibration levels and weight.     

Optimal bidding models of power plants considering transmission congestion

In order to achieve optimal bidding strategy of power plants in electricity market, the authors build optimal bidding model by predicting the bidding coefficients of competitors, and the optimal bidding coefficient without considering transmission capacity is achieved. Based on the bidding coefficients, the market clearing model is built, and the expected market clearing price is achieved. According to the expected values, the authors calculate the power flow. When forecasting the transmission congestion, this paper presents an optimal bidding model taking transmission congestion into account. Based on sensitivity analysis, the output regulation of power plants with minimum cost of eliminating congestion is achieved. Simulation results demonstrate that the proposed method can help power plants achieve the optimal profit.     

基于Adaboost算法的输电线路舞动预警方法

输电线路舞动是目前尚未被全面准确认识的世界性难题,已严重威胁输电系统的安全稳定运行。文章分析影响舞动的外界气象环境因素,并在此基础上提出一种基于Adaboost集成学习算法的输电线舞动预警方法。采用基于Gini指标的决策桩作为弱分类器,通过对多个弱分类器的训练及加权求和,输出舞动预测结果及其置信度,可为电网运维人员提供决策支撑。最后,使用历史数据进行验证性实验,结果证明了所提方法的有效性。     

Analysis of a multimode transmission line model of the shielding effectiveness of enclosures with apertures

The equivalent transmission line method is extended to multi-transverse electric modes of cavity which are introduced by aperture coupling, and it is used to analyze the shielding effectiveness of rectangular enclosures with apertures. The multimode transmission line method is verified by HFSS(High Frequency Structure Simulator). The results show that higher-order mode is essential to obtain an accurate shielding effectiveness of rectangular enclosure on wide frequency domain. Below the frequency of 1 GHz, nearer to the slot, the impact of higher-order mode on the shielding effectiveness is greater in the place mear the slot. Higher-order mode leads to a better shielding effectiveness.     

Efficiency optimization matching strategy of continuously variable transmission system with reflux power

To solve the problem that the transmission efficiency of continuously variable transmission system with reflux power varies in a great range, and the traditional control strategy can’t make sure that the overall system is under ideal conditions, an economy control method based on system efficiency optimization is put forward. The engine/transmission efficiency numerical model and system optimization model are built. Taking Matlab/Simulink as the platform, objective throttle position control table and objective ratio control table are obtained by solving the optimization model. Furthermore, ECE+EUDC drive cycle simulation based on the fuel economy of sample car is carried out, and the simulation results indicate that the method of system efficiency optimization make fuel consumption reduce by more than 1.5%.     

Optimal placement of bidirectional sensor for extra high voltage transmission towers

Combined the optimal placement method of triaxial accelerometers based upon the effective independence algorithm(EFI3) and the improved one dimensional effective independence algorithm, the optimal placement method of bidirectional accelerometers for the tower (EFI2) is proposed. The modal matrix on x direction and y direction are used as input instead of the uniaxial data. And according to the most linear independence and greater energy distribution of modal shape, EFI2 can optimize the sensor placement of accelerometers on both directions at the same time. On a long span extra high voltage transmission tower as a case study, the sensor placement in the direction of transversal and longitudinal wires is optimized by the EFI2 method. And with assessment by two methods, it is found that the EFI2 method can optimize the sensor placement of accelerometers on both directions effectively.     

计及电网停电风险的输电线路动态融冰决策方法

电网发生大面积冰灾情况时,多条输电线路存在覆冰故障隐患,电网稳定运行受到严重威胁,需要提前制定输电线路融冰方案,合理安排融冰顺序。针对此问题,分析输电线路覆冰继续运行给电网带来的停电风险,将与待融冰输电线路相关联的变电站的电气主接线展开,将传统削负荷模型改进后应用于输电网与变电站主接线的组合网络,建立断路器可靠性模型,计算靠后融冰线路因继续运行的电网停电风险;利用计及风速及降雨影响的输电线路覆冰增长预测模型,计算输电线路的覆冰率,根据覆冰率门槛值确定待融冰线路集,基于覆冰严重度模型构建系统全局的覆冰指数指标;综合考虑电网停电风险及系统全局覆冰指数建立输电线路融冰紧迫度指标,动态更新待融冰线路并决策融冰顺序。最后,以IEEE RBTS系统进行算例分析,验证了所提方法的可行性与合理性。     

Dynamic simulation of and experimentation with tracked vehicle hydrostatic steering characteristics of zero differential systems of a power shift steering transmission

This research investigated problems influencing tracked vehicles steering dynamic characteristics, such as rolling resistance during straight driving, steering centrifugal resistance, acceleration resistance during straight driving, scratching soil resistance of steering. Based on research about the relationship between the hydraulic steering regulation speed system and its maximum stable work pressure when vehicles have central steering on good roads (such as cement and rural roads), a zero differential hydraulic steering system of power shift steering transmission can ensure that vehicles maintain straight ahead stability through reasonably matching a steering drive system. The test indicates that vehicles have good dynamic characteristics when the work pressure accounted for 60% to 80% of the security work pressure.     

LCL型CPT系统的参数设计方法及频率特性分析

以金鲳鱼为原料,固定小麦粉与水的质量比为2∶1,食盐添加量2%,微波真空度0.095 MPa,在单因素试验的基础上,通过正交试验对微波真空技术膨化鱼糜饼工艺条件进行优化。结果表明,鱼糜饼制作的最佳工艺条件为:鱼糜含量35%,膨化温度100℃,膨化时间20 min,鱼糜饼厚度2 mm,在该工艺条件下,制得的膨化鱼糜饼色泽金黄、质地酥脆、风味清香,成品膨化率可达到540%。     

Design of networking condition monitoring andfault diagnosis for wind turbine transmission system

In order to solve the incipient fault diagnose problem of the transmission system, a networking condition monitoring and failure diagnosis system based on B/S and C/S hybrid architecture for wind turbine transmission system is designed in the paper. Firstly, the paper analyzes the demands of condition monitoring and fault diagnosis system for wind turbine transmission system, and designs its overall framework and function modules. Then, combining with the data acquisition equipment, by the .NET and SQL Server platform, the paper designs condition monitoring and failure diagnosis system for wind turbine transmission system, which includes the functions of networking data acquisition, remote condition monitoring, signal analysis, fault diagnosis and database as well. The system has been successfully applied to a condition monitoring and fault diagnosis of wind turbine transmission system.     

高压交直流同塔输电线路无线电干扰与可听噪声的计算

为了寻求一种适合交直流同塔架设线路的无线电干扰与可听噪声计算方法,从理论上分析了混合线路表面场强的特点,利用线性叠加原理求出混合线路表面场强,并结合晴天和雨天对交流和直流线路电晕程度的不同影响,提出在同一种天气状况下计算交直流线路无线电干扰与可听噪声。用3种计算无线电干扰与可听噪声的方法,分晴天和雨天情况进行计算比较,结果表明3种方法中BPA修正公式计算值最大,该方法可视为目前计算交直流同塔线路无线电干扰与可听噪声的有效方法。     

Full Aero-elastic Bridge Model Design of Long Span Arch Bridge

Aero-elastic model design is the precondition of full bridge aero-elastic model tunnel tests. The full aero-elastic bridge model design of long span arch bridge is discussed. The effect on the model design of different transverse rod space and bend stiff is analyzed in detail. Different scheme need to be designed according to the transverse rod stiff. Considering the changing section dimensional arches, the method of projecting the spatial arches to the plane arches, then designing the plane arches, at last projecting the plane arches to the spatial arches is proposed at first. The results show that the method is effective.     

An overview of APSIM, a model designed for farming systems simulation

The Agricultural Production Systems Simulator (APSIM) is a modular modelling framework that has been developed by the Agricultural Production Systems Research Unit in Australia. APSIM was developed to simulate biophysical process in farming systems, in particular where there is interest in the economic and ecological outcomes of management practice in the face of climatic risk. The paper outlines APSIM's structure and provides details of the concepts behind the different plant, soil and management modules. These modules include a diverse range of crops, pastures and trees, soil processes including water balance, N and P transformations, soil pH, erosion and a full range of management controls. Reports of APSIM testing in a diverse range of systems and environments are summarised. An example of model performance in a long-term cropping systems trial is provided. APSIM has been used in a broad range of applications, including support for on-farm decision making, farming systems design for production or resource management objectives, assessment of the value of seasonal climate forecasting, analysis of supply chain issues in agribusiness activities, development of waste management guidelines, risk assessment for government policy making and as a guide to research and education activity. An extensive citation list for these model testing and application studies is provided.     

Testing and modeling studies on creep characters of supports for tunnel using nonlinear constitutive model

Creep characters of tunnel supports structure is analyzed according to triaxial creep test of concrete specimen of deep tunnel supports structure adopting MTS815 hydraulic servo system. The creep parameters of nonlinear creep model are presented based oncreep curve. The finite element numerical model has been established considering tunnel construction process, creep characters of surrounding rock and support structure. The displacement characteristics, the effective stress and the maximum shear stress in different position in primary support and second lining are obtained through creep characters analysis of surrounding rock and supports structure. The features of displacement and stress dependent time of tunnel supports has visible difference comparing with discard creep effect and calculation displacement and practical monitoring results is basic concordance. The creep characters of surrounding rock and tunnel supports should be considered for deep tunnel.     

The harmonic Norton model established conditions of nonlinear load in low voltage distribution system

According to the experiments which concern about nonlinear loads in low voltage distribution systems,the voltage crest factor has a crucial effect on the establishment of nonlinear load harmonic Norton model,and it is verified by a large number of measured data. In the low voltage system that voltage waveform presents a flat characteristic,the nonlinear load can be simplified by the Norton model. Experimental and simulation results also show that different reference voltages can lead to different mean values of Norton model parameter which is obtained by fluctuation quantity method. The differences don’t have any effect on harmonic load flow analysis,but it affects the accuracy and credibility of the assessment load harmonic contribution level.     

Optimal design on the hydraulic system of CVT based on response speed and tracking accuracy

Aiming at speed ratio’s lag, tracking deviation and pulleys’ slipping and over clamping during clamping force control of CVT (continuously variable transmission) hydraulic system, corresponding optimal design methods are employed based on the practical structure of speed ratio control and clamping force control system, and the speed ratio control and clamping force control are employed by the optimal design of the system’s structural parameters. Combine with vehicle’s start-up working condition, simulation analysis is carried out on the platform of AMESim. The analysis results show that the dynamic characteristics and precision of tracking deviation are improved by the optimal design system.