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Xie Q.,Tongji University | Wang Y.,East China Electric Power Design Institute
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

Complicated interactions exist in the flexible bus connected substation equipment under earthquake. In this paper, firstly, the flexible bus was simplified as a cable. By introducing deformation compatibility condition between the substation equipment and the flexible bus, the tension and tension stiffness of the cable were derived. Then a mathematical model for analyzing the dynamic interaction between the equipment and the cable was proposed and solved by using the Runge-Kutta method. The following case study and parametric analysis showed that due to the interconnection by the cable, the seismic response of the coupling system, which was different from that of the independent equipment, exhibited strong nonlinearity and the tension in the cable varied abruptly under earthquake action. The results demonstrated that the interaction between the flexible bus and the equipment should be considered in the seismic design of substation equipment and the mathematical model derived in this paper could be used to analyze the seismic response of the equipment in random frequency interconnected by the flexible buses. © 2010 Chinese Society for Electrical Engineering. Source

Chen J.,Tongji University | Yuan S.,East China Electric Power Design Institute
Journal of Engineering Mechanics | Year: 2014

Solving the Fokker-Planck-Kolmogorov (FPK) equation is one of the most important and challenging problems in highdimensional nonlinear stochastic dynamics, which is widely encountered in various science and engineering disciplines. To date, no method available is capable of dealing with systems of dimensions higher than eight. The present paper aims at tackling this problem in a different way, i.e., reducing the dimension of the FPK equation by constructing an equivalent probability flux. In the paper, two different treatments for multidimensional stochastic dynamical systems, the FPK equation and the probability density evolution method (PDEM), are outlined. Particularly, the FPK equation is revisited in a completely new way by constructing the probability fluxes based on the embedded dynamics mechanism and then invoking the principle of preservation of probability. The FPK equation is then marginalized to reduce the dimension, resulting in a fluxform equation involving unknown probability flux caused by the drift effect. On the basis of the equivalence of the two treatments, this unknown probability flux could be replaced by an equivalent probability flux, which is available using the PDEM. An algorithm is proposed to adopt the data from the solution of the generalized density evolution equation in PDEM to construct the numerical equivalent flux. Consequently, a onedimensional parabolic partial differential equation, i.e., the flux-equivalent probability density evolution equation, could then be solved to yield the probability density function of the response of concern. By doing so, a high-dimensional FPK equation is reduced to a one-dimensional partial differential equation, for which the numerical solution is quite easy. Several numerical examples are studied to verify and validate the proposed method. Problems to be further studied are discussed. © 2014 American Society of Civil Engineers. Source

Li G.J.,Shanghai JiaoTong University | Ma F.,Arizona State University | Choi S.S.,Nanyang Technological University | Zhang X.P.,East China Electric Power Design Institute
IET Power Electronics | Year: 2012

A three-phase unified power quality conditioner (UPQC) with cross-phase connection is investigated. The UPQC is designed to mitigate voltage sags/swells, including those resulting from single-phase faults. Based on an analysis of the configuration of the conditioner, multi-loop control schemes are proposed for the voltage and current compensation strategies. The practicability of the topology and the effectiveness of the control schemes are verified through simulations using PSCAD/EMTDC. The results demonstrate the proposed control strategy for the cross-phase-connected UPQC is capable of regulating load terminal voltage and compensating load current changes simultaneously and effectively. © 2012 The Institution of Engineering and Technology. Source

Fan H.,Shanghai JiaoTong University | Zhou H.,East China Electric Power Design Institute | Wang J.,East China University of Science and Technology
Energy Conversion and Management | Year: 2014

The pyrolysis of three municipal sewage sludges was carried out using a slowly heating and gas sweeping fixed-bed reactor in the temperature range between 300 °C and 700 °C. The study was aimed to characterize the gaseous and liquid products derived from three different sewage sludges and mainly to discuss the varieties of sewage sludges on the yields and compositions of the gaseous and liquid products. The pyrolysis in this reactor was observed to produce high yields of liquid (above 40 wt.% at 700 °C) that contained high proportions of oxygen-containing compounds and nitrogenated compounds, with minor monoaromatics and aliphatic compounds. The gas and liquid yields correlated with the volatile matter contents in the sludges. For all three sewage sludges, the oxygenated compounds were the principal liquid compounds which could be produced at a low temperature of 300 °C, while more of nitrogenated compounds and other compounds were formed at 700 °C depending on the varieties of sewage sludges. © 2014 Elsevier Ltd. All rights reserved. Source

Chen J.,Tongji University | Yuan S.,East China Electric Power Design Institute
Probabilistic Engineering Mechanics | Year: 2014

Engineering structures usually exhibit hysteretic property when they are subjected to disastrous loadings such as earthquakes, strong wind and huge waves. The solution of FPK equation related to such complex systems are of great significance but is still an extremely challenging problem. In the present paper, the FPK equation for hysteretic systems is studied and the dimension is reduced to render an efficient numerical solution. The equivalence of probability flux in two different treatments, i.e., in the FPK equation which is based on the state space description and in the generalized density evolution equation which is mainly based on the random event description, are first examined. Then the FPK equation for additively excited multi-degree-of-freedom structures exhibiting nonlinear behaviors, including hysteresis together with strength degradation and stiffness degradation, is discussed. By invoking the basic idea of equivalence of probability flux, an equivalent probability flux due to drift could be constructed by the probability density evolution method (PDEM) instead of the direct coupled high-dimensional integral. Numerical implementation procedure is outlined. Two numerical examples are illustrated. Problems to be further studied are discussed. © 2014 Elsevier Ltd. All rights reserved. Source

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