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301.
In this work, an accurate coupling capacitor voltage transformer (CCVT) model for electromagnetic transient studies is presented. The model takes into account linear and nonlinear elements. A support routine was developed to compute the linear 230 kV CCVT parameters (resistances, inductances and capacitances) from frequency response data. The magnetic core and surge arrester nonlinear characteristics were estimated from laboratory measurements as well. The model is used in connection with the electromagnetic transients program (EMTP) to predict the CCVT performance when it is submitted to transient overvoltages, as are the cases of voltages due to the ferroresonance phenomenon and circuit breaker switching. The difference between simulated and measured results is fairly small. Simulations had shown that transient overvoltages produced inside the CCVT, when a short circuit is cleared at the CCVT secondary side, are effectively damped out by the ferroresonance suppression circuit and the protection circuit. 相似文献
302.
The paper is concerned with a mathematical model of a biological system. The cases of quasistationary state and transients
are examined. The Laplace-transformed unknown parameters of the biological system are analyzed. A structural element associated
with a quasistationary response of the biosystem to external disturbances is analyzed.
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Translated from Kibernetika i Sistemnyi Analiz, No. 5, pp. 86–95, September–October 2006. 相似文献
303.
In this paper, we present reliable guidelines allowing to maximize the detection and analysis of deep defects in semiconductors by introducing a new method of analysis that we named Modified Levenberg-Marquardt Deep-Level Transient Spectroscopy (MLM-DLTS) based on the Levenberg-Marquardt algorithm that we modified deliberately and associated with two other high-resolution techniques, i.e. the Matrix Pencil algorithm and modified Prony's method. The performances of the method were first assessed with a procedure of simulation by generating multi-exponential capacitance transients with a changing signal-to-noise ratio. These different tests have demonstrated to what extent such a method of analysis is more efficient than classic correlation methods based on DLTS spectra and than three high-resolution methods already existing in the literature. Finally, when the signal-to-noise ratio is low, and in the aim of getting precise results, a few smoothing algorithms were tested. Our findings evidence how the smoothing quality can be controlled under certain conditions while avoiding both the distortions in the shape of the capacitance transients and the DLTS spectra. 相似文献
304.
基于权重数值积分的电力电子开关仿真插值算法 总被引:1,自引:0,他引:1
随着电力电子技术在电力系统中的广泛应用,电力电子开关引起的高频次系统拓扑突变对电磁暂态仿真提出了新挑战,为此,提出了一种电力电子开关仿真插值算法。在全局隐式梯形积分法条件下,该算法在开关动作点通过线性插值计算系统变量,并利用后向欧拉法对系统进行重新初始化,而后根据插值点在当步仿真步长的位置,利用权重法数值积分,灵活改变积分步长,快速积分至仿真整步时间点,对仿真进行再同步。在开关动作过程中,算法仅通过一次插值对仿真进行重新初始化,并在再同步过程中保持节点导纳矩阵不变,且能有效抑制数值振荡。算法在保证精度的前提下,降低了计算负担,提高了计算速度,并考虑了多重开关问题。最后通过算例验证了算法的适应性和有效性。 相似文献
305.
306.
307.
Careful analysis of transients in shipboard power systems is important to achieve long life times of the com ponents in future all-electric ships. In order to accomplish results with high accuracy, it ... 相似文献
308.
J. T. Anderson D. T. Gethin R. W. Lewis 《International Journal of Cast Metals Research》2013,26(5):285-293
An experimental programme to establish shell thermal conductivity and cooling transients in an investment cast part is presented. This showed that shell thermal conductivity is mildly temperature dependent and has a low value, nominally 0.8 Wm?1 K?1. The cooling transients in the cast part were measured with good repeatability and were found to be affected significantly by the addition of forced convection, shell temperature on pour and radiation coupling. Good agreement with an adaptive thermal analysis was achieved using a simple far field radiation model as a basis for establishing heat loss. However, this suggested that the translucent nature of the shell also contributed to heat loss directly from the casting surface. 相似文献
309.
《Urban Water Journal》2013,10(2):113-127
Hydraulic transients generate significant negative pressures in water systems that may cause intrusion of contaminated water from the environment into the pipe. This paper expands the consideration of transient intrusion events from their purely hydraulic aspects by developing a risk-based framework for comparing the relative risk-reduction achieved by alternative transient-intrusion mitigation strategies. Alternative strategies may be any combination of changes to system operation or surge controls that would reduce the potential for intrusion of contaminants from the soil-groundwater environment surrounding the pipe. A reference groundwater contamination is assumed, and intrusion volumes and time-varying pathogen concentrations are computed respectively using hydraulic transient and water quality models. Risk-based measures are proposed to provide quantitative assessments of the relative reduction in the risk of receptor infection achieved by alternative mitigation strategies. 相似文献
310.
Rhonda R. Peters Dharshana Muthumuni Tim Bartel Hossein Salehfar Michael Mann 《Electric Power Systems Research》2010
An installed 900 kW fixed speed stall controlled soft-started wind turbine connected to a weak distribution grid was modeled under start-up conditions. Generator and soft-start control and design parameters were not available, so a modeling process independent of this information was developed. Field measured transients were closely reproduced in simulation using a full-order generator model with generic parameters and a thyristor-based graduated interconnection to the grid. A Static VAR Compensator model was then added to the wind turbine model to explore a method of reducing start-up transients. It was found that for the specific transients modeled, a 300 kVAR SVC supplied sufficient reactive power to limit line voltage variations to within 3% of steady state values. Model details and simulation output are presented in this paper. 相似文献