共查询到20条相似文献，搜索用时 31 毫秒
1.
电网可靠性评估的网络静态等值模型分析 总被引：2，自引：0，他引：2
为缓解大电网可靠性评估的计算复杂性,采取等值参数联合概率密度分布建模的方式开展了外网静态等值研究。在常规确定性静态Ward等值技术基础上,考虑外部区域发电机和线路随机故障,通过计算各种随机故障状态下的外网等值参数,即外网等值注入功率和外网等值串联支路阻抗,基于概率密度估计技术建立了等值参数的联合概率密度分布。外网静态概率等值模型克服了常规确定性静态Ward等值技术的不足,充分计入外网等值参数的随机性,减少了电网可靠性评估计算时间的同时提高了计算精度。对两区域RBTS系统和RTS79系统研究验证了其有效性和准确性。 相似文献
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According to the fuzzy and uncertainty characteristics of soil liquefaction, a comprehensive fuzzy evaluation model of soil liquefaction is presented. In the comprehensive fuzzy evaluation model of soil liquefaction, the following factors, such as earthquake intensity, SPT counts, groundwater level and mean diameter of sand soil particle which affect the liquefaction of sand soil were considered, and the sketch map of trapezoid subordinate function was adopted and the subordinate function expression of each factor was given. The results show that the comprehensive fuzzy evaluation model of soil liquefaction is feasible and valuable. 相似文献
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Chen Ganping Xu Guoyu Qin Yihong 《保鲜与加工》1990,(1):43-48
A digital power system stabilizer ( DPSS ) and its design method are presented in this paper. The mathematical model of a single machine infinite bus power system is obtained using off-line parameter identifications, and on the base of the identified model the control system is synthesized by generalized minimum variance control principles. Through feedback combination of several signals this control system has double functions of damping low frequency oscillation and automatic voltage regulating. In order to avoid static errors the very effective way is to combine discrete generalized minimum variance control with continuous integral control. Besides the proposed control strategy is very simple in structures and very easy to realize. Simulation results under several cases have shown the correctness and effectiveness of the proposed control strategy. 相似文献
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The voltage instability of power system often occurs when the active power on one or more weak branches exceeds its transfer capability. A preventive control model for static voltage stability is proposed using the active power transfer capability of weak branches as static voltage stability constraints. A local line based voltage stability index is used to determine the critical contingencies, weak branches and transfer capability of each weak branch. A static security analysis method, which is based on DC power flow equations, is used to establish the non linear active power flow expressions on weak branches following each critical contingency. The active power constraints on weak branches can be obtained from the active power flow expressions and transfer capabilities of weak branches. A quadratic optimal model for preventive control including the proposed active power constraints on weak branches is presented. The simulation results for IEEEE14 bus system and IEEE118 bus system demonstrate the correctness and effectiveness of the proposed preventive control model. 相似文献
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A nitrogen expansion liquefaction process which is suitable for small-scale liquefaction plants is proposed for coalbed methane (CBM) with high nitrogen content. In order to investigate the effects of the nitrogen content on the liquefaction system performance, optimizations are done for CBM with nitrogen content among 0~70% via simulation and calculation with HYSYS when the liquefaction rate and the methane recovery rate are fixed respectively, and with the unit product liquefaction power consumption as the major index, the corresponding system performance is compared. The results show that, the system performance of CBM liquefaction process changes greatly along with nitrogen content. However, the changing is not monotonous. 相似文献
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Based on the mechanism of steel slit wall, a simplified elasto plastic analytical model which allows for nonlinear dynamic and static analysis was proposed. The parameters of simplified model related to configuration and nonlinear behavior were defined. In order to validate the simplified model, the pushover analysis of steel slit wall and a frame with steel slit wall were conducted. The results show that the load displacement curves obtained from simplified models, experiments and FEM are similar. The proposed model can fully represent the mechanism of steel slit wall, and it can correctly predict the internal forces and deformations of each member in the model. 相似文献
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Considering the interference introduced by primary user, the outage probability of cognitive relay networks under imperfect channel state information is analyzed based, on the relay selection for the maximum channel gain. In addition, the mathematical optimization model of maximizing the spectrum efficiency under the interference constraint of primary user and the QoS requirement of cognitive user is proposed for cognitive relay networks. Then, the optimal solution of the model is obtained with the Lagrangian method. The proposed scheme improves the spectrum efficiency of cognitive relay networks on the premise of guaranteeing the transmission performance of primary user. Simulation results show that the proposed power allocation scheme improves the system performance compared with the traditional equal power allocation scheme. Meanwhile, it indicates that the approximate spectrum efficiency can be obtained under the perfect channel state and the imperfect channel state. Under the imperfect channel state, the feedback information and the complexity of implementation will be reduced, which is beneficial to the engineering application. 相似文献
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The transporting unit is one of the indispensable facilities in the biomass pyrolytic liquefaction system and the continuous and steady transporting characteristic is the key to ensure the process of biomass pyrolytic liquefaction.This paper introduces one biomass transporting system adopted in the experiment;taking sawdust,paddy shell, wheat hull and corn grain with different grain diameters as the representative materials,the influence law of various factors on transportation capacity is studied in this paper.The research results obtained can offer an important reference for realizing a continuous and reliable biomass pyrolytic liquefaction process. 相似文献
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多角度认识农田生态系统在CO2源或汇的问题有助于中国制定正确的农业管理措施,通过减少农田生态系统碳的排放或增加碳的储存,可以使中国在国际排放权的争夺中处于主动地位;笔者总结了国内外最新文献中农田CO2交换量的研究现状和通量观测方法;对近年来国内外农田生态系统CO2交换量研究所取得的进展进行了详细阐述,并介绍了测量农田生态系统CO2通量的微气象法和箱法等通量观测的代表性方法,列表说明了涡度相关法、静态透明箱法、静态暗箱法三者存在的优缺点。分析了提高农田生态系统碳交换测定通量的准确性的途径及扩大不同农作物CO2测定量的适用范围;对农田生态系统CO2交换量观测全面深入研究提出了一些建议和展望。 相似文献
12.
Ran Li Ren Zhen Jiang Zejia 《保鲜与加工》1988,(6)
An optimal active power adjustment model is deve in this paper for hybrid AC/DC systems after outage contingencies. The objective of the model is to minimize the rejection of load when some elements are out of service, with adjustment strategy approaching practical system operation. A large number of outage contingencies are simulated when the Monte-Carlo Method is emyloyed to evaluate the system reliability, requiring fast calculation of each simulation. The model and computer method proposed in this paper satisfy such a requirment because of the application of concentric relaxation, recursive branch constraint treatment in linear programming and a direct method for B-1 matrix modification. This paper is concerned with the simplified steady state conditions of the system based on DC load-flow, which implies the reliability indices calculated are the measures about static loss of load. The results for a 14-bus hybrid AC/DC system are given. 相似文献
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木质纤维素的催化热化学液化是制备液体燃料的重要途径之一,其中液化溶剂和催化剂的选择很重要。总结了催化热化学液化中所用到的溶剂和催化剂及它们的液化效果,初步探索了木质纤维素在溶剂中的催化热化学液化机理。 相似文献
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The static load test and the finite element analysis of the multi-tower cable-stayed bridge with tie-down cables are carried out. The test and analysis model of the bridge is created by referencing to the actual structure of a Changjiang River bridge. The static mechanical behaviors of such bridge with tie-down cables and the normal multi-tower cable-stayed bridge are comparatively analyzed by the static load test and the finite element analysis. It is shown that the structural system of the cable-stayed bridge with tie-down cables can effectively improve the structural rigidity and reduce the bending moment of the main beams, pylons and piers. According to the results, the best scheme about the location and number of tie-down cables is proposed. 相似文献
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With the development of circulating fluidized bed boiler(CFB),the study field of external heat exchanger(EHE) is greater in extent and degree.In order to research the working process of EHE,the model which deals with flow and heat transfer of EHE for 300MW CFB of Dong Fang Boiler Grou PCo.Ltd.is presented.Based on the cell modeling theory,the EHE is divided into several chamber by heating surfaces.The mass and energy conservation equations of each cell have been developed according to some reasonable assumption.The complete mathematical model has been compiled by Fortran and solved by classical Algorithm of Runge-Kutta.The static test and perturbation experiment of simulating model has been performed.The simulation results show that the model has been reached the steady state rapidly,the dynamic responses are reasonable and the modeling presented in the paper is reliable and appropriate. 相似文献
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提出了一种包含了逆变器接口（voltage source inverter,VSI）、同步电机接口（synchronous generator,SG）的独立微网控制策略,并分析了其小信号稳定性。VSI接口和SG接口的分布式电源均采用下垂控制策略,二者之间无需实时通信,可实现负荷功率共享。建立了系统的小信号状态空间模型,主要包括：同步发电机及其控制器的小信号模型、逆变器及其控制器的小信号模型、电网络及负荷小信号模型。计算了下垂增益变化时的根轨迹,得到了系统主特征值随参数变化的根轨迹,计算了不同状态变量对特征值的参与因子。稳定性分析结果表明：当所有分布式电源采用下垂控制时,引入同步发电机接口的分布式电源,系统频率小信号稳定性大大增强。PSCAD时域仿真验证了特征值计算的正确性。 相似文献
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生物质热化学法液化可分为加压液化和常压快速液化。与加压液化方法相比,常压快速液化法具有反应条件温和、设备简单、产品可以替代传统石油化学品的特点,具有可以在农村就地开展液化生产的优势。从液化剂的角度阐述了常压快速液化的发展趋势,并建议加强生物质常压快速液化工艺的研究。 相似文献
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Kinetics characteristics of resolving of rock salt of Changshan in dynamic state have been studied by using conductance method and equipment made by ourself. The results show that the quantitative relationship between conductance(L) or concentration (c) of resolving solution in the process of resolving of rock salt and time t ( kinetics equation )is analogous to Langmuir equation for different flows in ambient temperature.Constant E or a increases with the increase of the flow( V ), whereas constant F or b constant decreases. The above 4 constants in dynamic state are smaller than those in static state. 相似文献
20.
Chen Ganping Qin Yihong Xu Guoyu 《保鲜与加工》1989,(4):55-62
This paper obtains the mathematical model of a single machine infinite bus power system using the idea of parameter identifications. Because the noise is considered in parameter identification process, the model reflects the real system more exactly. On the base of the identified model this paper also presents a discrete automatic voltage regulator by minimum variance control principles. In order to avoid the static error, we combine discrete minimum variance control with continuous integral control and get very satisfactory effects. This proposed control strategy is very easy to realize. The simulation results show that in every case the dynamic qualities of the proposed control strategy are incomparably superior to that of the conventional PI regulator, which means the proposed control strategy has great practical values. 相似文献