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Fu X.,Xi'an Jiaotong University | Fu X.,Northwest Electrical Power Design Institute | Wang X.,Xi'an Jiaotong University
International Journal of Electrical Power and Energy Systems | Year: 2011

A computationally simple algorithm is developed for studying the load shedding problem in emergencies where an ac power flow solution cannot be found for the stressed system. The proposed algorithm is divided into two sub-problems: restoring solvability sub-problem and improving voltage stability margin (VSM) sub-problem. Linear optimization (LP)-based optimal power flow (OPF) is applied to solve each sub-problem. In restoring solvability sub-problem, rather than taking restoring power flow solvability as direct objective function, the objective function of maximization of voltage magnitudes of weak buses is employed. In VSM sub-problem, the traditional load shedding objective is extended to incorporate both technical and economic effects of load shedding and the linearized VSM constraint was added into the LP-based OPF. Case studies with a real 682 bus system are presented. The simulation results show that the proposed load shedding algorithm is effective, fast in finding the load shedding scheme to solve the problem of restoring solvability and improving VSM. © 2010 Elsevier Ltd. All rights reserved.

Dang F.,Xi'an University of Technology | Huang J.,Xi'an University of Technology | Guo C.,Northwest Electrical Power Design Institute | Deng Q.,Xi'an University of Technology
Modern Tunnelling Technology | Year: 2015

This paper discusses the stability of tunnels in clay and establishes a state function R for one point of the surrounding rock by fitting the nonlinear behavior of clay with a hyperbolic model and considering impacts of surrounding rock strength and deformation resistance. A quantitative evaluation method is proposed for the stability of tunnels in clay based on the strength reduction theory, i.e., the strength-deformation reduction method. Using the application of a railway tunnel as an example, the results show that this method not only takes multiple factors that may affect the rock deterioration into consideration, but also has results closer to the measured ones when compared with the strength reduction method and limit equilibrium method. © 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Huang J.,Xi'an University of Technology | Dang F.,Xi'an University of Technology | Guo C.,Northwest Electrical Power Design Institute
Modern Tunnelling Technology | Year: 2013

This paper quantitatively evaluates tunnel stabilit y using a safety factor defined in light of rock deformation and discusses the degree of stability by increasing the actual rock displacement caused by tunnel excavation to the ultimate displacement at the critical state. Based on the theoretical elasto-plastic analysis of an unlined circular tunnel, it derives a principle parameter reduction method in which the increase of actual displacement is achieved by considering the elastic modulus degradation of the surrounding rock. The safety factor is calculated by using the ultimate displacement as the criterion of tunnel instability. With the finite -element parameter reduction method, the stability of unlined circular tunnels with different depths and diameters in various grades of rock is discussed. The results show that the parameter reduction method is feasible and applicable to rock masses of grades I to IV, whereas there are some deviations for the rock mass of grade V.

Qu G.-Z.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Zhang J.-M.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Cheng D.-X.,Northwest Electrical Power Design Institute
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

To better understand the in-situ engineering conditions of frozen ground where the piers of Qinghai-Tibetan ±500kV Direct Current Transmission Line Project will be constructed; the direct shearing creep experiment for frozen silty clay, a kind of soil taken from Wudaoliang on the Qinghai-Tibetan Plateau and remodeled in different moisture contents and densities in laboratory at -2°C, was carried out. The study results show that most creep of the frozen silty clay appears as attenuation creep which has two phases: unsteady creep phase and steady creep phase; only several creeps of frozen silty clay takes on the third phases: accelerated creep phase. The long-term strength of frozen soil could be calculated by the long-term strength equation. The long-term strength of the frozen silty clay closely affected by the moisture content and density of the soil; the frozen soil with higher moisture content has higher long-term strength at low moisture circumstance; but it shows opposite trend at high moisture circumstance; the frozen soil with higher density has higher long-term strength with the same moisture content.

Yang S.-B.,Northwest Electrical Power Design Institute | Xu X.,Tianjin Pipeline Engineering Group Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

Based on the support system of deep foundation pit of Beijing Century Building with excavation depth of 19.95 m, the ground situation and surroundings as well as the situation of engineering geology are analyzed concretely. A comprehensive support plan combining the soil-nailing walls with pile-anchor system is proposed to make use of their respective advantages. The technique of artificial excavated piles is adopted to adapt to the cobble stratum so as to solve the problems aroused by power drilling. The maximum value of horizontal displacement is only 12.1 mm, and the mechanical properties of each support element are all in satisfactory. The results illustrate that the design is reasonable and the displacement of the pit is controlled effectively. The experience is valuable to similar projects.

Zhao R.,Northwestern Polytechnical University | Shen X.,Northwestern Polytechnical University | Zhang X.,Northwestern Polytechnical University | Hou J.,Northwest Electrical Power Design Institute
ICCASM 2010 - 2010 International Conference on Computer Application and System Modeling, Proceedings | Year: 2010

Wireless Sensor Networks (WSN) consist of thousands of low-cost sensor nodes that are densely deployed. Broadcasting is a method that allows nodes in WSN to share their data efficiently. Due to the limited energy supply of each sensor node, it has become a crucial issue to maximize the network life-time in the design of broadcast protocols. In this paper, we propose an efficient broadcast protocol - Maximum Life-time Broadcast (MLB) for WSN. It optimizes broadcasting by reducing redundant rebroadcasts and balancing the energy consumption among all nodes. MLB uses the number of neighbors that have not yet received the broadcast packet to measure a node's rebroadcast efficiency. High efficient rebroadcasts will help to reduce the number of rebroadcasts and thus reduce the broadcast overhead of MLB. Simulation results show that MLB can prolong the network life-time of WSN effectively and it is scalable with respect to network size and node density. © 2010 IEEE.

Fu X.,Northwest Electrical Power Design Institute
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2014

An algorithm of static security preventive control is proposed for power system with the consideration of uncertainty factors. A static security index of power system is proposed, which considers the probability of pre-defined contingencies and the uncertainty of load level. The preventive control strategy is obtained by adding the index into the preventive control model, which emphasizes the generator rescheduling and load shedding. For the large influence of load characteristics on system, the ZIP load model is adopted. The simulative result of a practical domestic system verifies its effectiveness.

Fu X.,Northwest Electrical Power Design Institute
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2010

Equivalent two-source phase-domain method is proposed to calculate the open conductor plus short circuit fault for power system with solid-state fault-current limiter. A new simulation method is presented, which adds an impedance branch between virtual fault point and ground in phase domain to simulate the solid state fault current limiter & short circuit fault and another impedance branch between virtual fault points to simulate the open conductor fault. The two-port network theory is applied to simplify the complicated power network into a two-source equivalent circuit with only two nodes, and the phase-sequence parameter transformation technique is applied to simulate the open conductor plus short circuit fault as the connection in phase domain between two nodes of two-source network. The proposed method has two features: the influences of solid-state fault current limiter and fault point resistance are easily taken into account and the complex connections between sequence networks are avoided. Case calculation shows its effectiveness.

Fang X.-W.,Chongqing University | Shen C.-N.,Chongqing University of Science and Technology | Chen Z.-H.,Chongqing University | Liu H.-J.,Northwest Electrical Power Design Institute | Huang X.-F.,Chongqing University
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

A series of triaxial shear tests on intact unsaturated Q2 loess were conducted using computerized tomography (CT)-multi-function triaxial apparatus developed in Logistical Engineering University. The distinct CT images and detailed CT data of the evolution of meso-structure were obtained during loading. A new method is proposed to identify the yield stress of intact Q2 loess using curves of CT-number versus deviatoric stress. A structure parameter and a structure evolution variable are defined based on CT data. The variable of structure evolution increases with the increase in net confining pressure under the same suction; while the variable of structure evolution decreases with the increase in suction under the same net confining pressure. An equation describing the evolution of structure is developed. In the equation, deviatoric strain and volumetric strain are included. The equation reflects the influences of net confining pressure and suction on the evolution of meso-structure during loading. The structure evolution equation successfully simulates the laboratory tests of unsaturated intact Q2 loess.

Zhou H.,Chongqing University | Zhang Z.,Chongqing University | Zhang J.,Northwest Electrical Power Design Institute | Zhang W.,Chongqing University | Zhao Q.,Chongqing University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

Spraying ammonia flow can influence the efficiency of supercritical boiler's flue gas denitrification device based on selective catalytic reduction (SCR). Excessive spraying flow can also result in ash deposit and corruption of backward heating units such as air heater, simultaneously, it causes resource waste and second pollution. Moreover, optimal traditional PID control with variational load on the flow is difficult. And in order to improve traditional radial basis function (RBF) neural network (RBFNN)'s adaptivities of nonlinearity and disturbance during variational working condition, so, a new control scheme based on mixed structure RBFNN (MS-RBFNN) was proposed. This MS-RBFNN can synthetically study current main relative state parameters, so as to parallel calculate the optimal spraying ammonia flow by using least NOx discharge of SCR device as its training signal. Experimental results indicate, comparing with traditional PID control, this scheme's advantages on better NOx control effect and adaptability of variable working condition as well as little ammonia usage. © 2011 Chin. Soc. for Elec. Eng.

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