Modern battlefield doctrine is based on mobility, flexibility, and rapid response to changing situations. As is well known, mobile ad hoc network systems are among the best utilities for battlefield activity. Although...Modern battlefield doctrine is based on mobility, flexibility, and rapid response to changing situations. As is well known, mobile ad hoc network systems are among the best utilities for battlefield activity. Although much research has been done on secure routing, security issues have largely been ignored in applying mobile ad hoc network theory to computer technology. An ad hoc network is usually assumed to be homogeneous, which is an irrational assumption for armies. It is clear that soldiers, commanders, and commanders-in-chief should have different security levels and computation powers as they have access to asymmetric resources. Imitating basic military rank levels in battlefield situations, how multilevel security can be introduced into ad hoc networks is indicated, thereby controlling restricted classified information flows among nodes that have different security levels.展开更多
On the basis of analyzing the flaws of present multiple-attribute and multilevel evaluation methods, concerning the problem of characteristics of the multiple-attribute and multilevel system s appraisal and the partic...On the basis of analyzing the flaws of present multiple-attribute and multilevel evaluation methods, concerning the problem of characteristics of the multiple-attribute and multilevel system s appraisal and the particular emphasis on the respective attributes in the evaluation process, as well as its relevance to the environment, an optimal attribute system is proposed, and the multiplicative analytic hierarchy process (MAHP) is used to obtain subjective weight coefficients and the objective weight coefficient evaluating method is given. The deviation between the index value of each level and the values of the same index of other levels are formulated, and an optimal model is gained, thus establishing the weight coefficients of the whole optimal attribute system. Furthermore, the detailed implementation procedure of this method is introduced. Besides, favorable results have been gained by applying the model to the practical problems of economic evaluation.展开更多
在海上风电直流汇集-直流送出系统中,基于单相模块化多电平换流器的面对面型(modular multilevel converter based front-to-front,MMC-FTF)高压大功率DC/DC变换器是连接中压汇聚线与高压直流输电(high voltage direct current,HVDC)线...在海上风电直流汇集-直流送出系统中,基于单相模块化多电平换流器的面对面型(modular multilevel converter based front-to-front,MMC-FTF)高压大功率DC/DC变换器是连接中压汇聚线与高压直流输电(high voltage direct current,HVDC)线路的关键接口设备。然而,针对MMC-FTF变换器的阻抗建模鲜有报道,且含MMC-FTF变换器的HVDC系统的小信号稳定性问题尚不明确。针对此问题,该文首先根据频率耦合效应提出共差模提取矩阵,实现了多谐波线性化方法下单相及三相MMC交直流侧阻抗模型的统一,并建立了MMC-FTF变换器的直流侧阻抗模型。其次,利用阻抗稳定性判据揭示了MMC-FTF变换器与岸上三相MMC换流站互联时存在的振荡风险。接着,根据相角灵敏度指标定量评估了不同控制器参数对系统稳定性的影响,并提出用于提升系统稳定性的调参准则。最后,基于MATLAB/Simulink仿真和硬件在环实验验证了结果的正确性。展开更多
为了研究模块化多电平换流器(modular multilevel converter,MMC)在嵌入储能系统(battery energy storage system,BESS)后内部动态特性的变化规律,对MMC-BESS的运行特性进行了详细分析,并提出了一种桥臂级平均值模型(arm average model,...为了研究模块化多电平换流器(modular multilevel converter,MMC)在嵌入储能系统(battery energy storage system,BESS)后内部动态特性的变化规律,对MMC-BESS的运行特性进行了详细分析,并提出了一种桥臂级平均值模型(arm average model,AAM)进行验证。首先,在假设桥臂中各储能子模块状态一致的前提下,将离散环节连续化,并根据电路特性方程构建了MMC-BESS的AAM电路模型。然后,根据交流端、直流端以及储能端之间的功率关系对MMC-BESS的运行模式进行划分,建立了桥臂电流与电池功率之间的关系,并对电池功率不均衡状态下的桥臂电流进行了分析。最后,利用Matlab/Simulink分别搭建了MMC-BESS的开关模型和AAM模型,并基于AAM验证了多种工况下的桥臂电流响应。仿真结果表明,AAM在显著提高仿真效率的同时可保证较高的准确性,电池功率的大小与均衡状况对桥臂电流的成分有较大影响。展开更多
基金the National Natural Science Foundation of China (60773049)the Natural Science Foundationof Jiangsu Province (BK2007086)the Fundamental Research Project of Natural Science in Colleges of Jiangsu Province(07KJB520016).
文摘Modern battlefield doctrine is based on mobility, flexibility, and rapid response to changing situations. As is well known, mobile ad hoc network systems are among the best utilities for battlefield activity. Although much research has been done on secure routing, security issues have largely been ignored in applying mobile ad hoc network theory to computer technology. An ad hoc network is usually assumed to be homogeneous, which is an irrational assumption for armies. It is clear that soldiers, commanders, and commanders-in-chief should have different security levels and computation powers as they have access to asymmetric resources. Imitating basic military rank levels in battlefield situations, how multilevel security can be introduced into ad hoc networks is indicated, thereby controlling restricted classified information flows among nodes that have different security levels.
基金The project was supported by the National Natural Science Foundation of China( 70172015) the Research Fund for Doc-toral Program of Higher Education(20010533016).
文摘On the basis of analyzing the flaws of present multiple-attribute and multilevel evaluation methods, concerning the problem of characteristics of the multiple-attribute and multilevel system s appraisal and the particular emphasis on the respective attributes in the evaluation process, as well as its relevance to the environment, an optimal attribute system is proposed, and the multiplicative analytic hierarchy process (MAHP) is used to obtain subjective weight coefficients and the objective weight coefficient evaluating method is given. The deviation between the index value of each level and the values of the same index of other levels are formulated, and an optimal model is gained, thus establishing the weight coefficients of the whole optimal attribute system. Furthermore, the detailed implementation procedure of this method is introduced. Besides, favorable results have been gained by applying the model to the practical problems of economic evaluation.
文摘在海上风电直流汇集-直流送出系统中,基于单相模块化多电平换流器的面对面型(modular multilevel converter based front-to-front,MMC-FTF)高压大功率DC/DC变换器是连接中压汇聚线与高压直流输电(high voltage direct current,HVDC)线路的关键接口设备。然而,针对MMC-FTF变换器的阻抗建模鲜有报道,且含MMC-FTF变换器的HVDC系统的小信号稳定性问题尚不明确。针对此问题,该文首先根据频率耦合效应提出共差模提取矩阵,实现了多谐波线性化方法下单相及三相MMC交直流侧阻抗模型的统一,并建立了MMC-FTF变换器的直流侧阻抗模型。其次,利用阻抗稳定性判据揭示了MMC-FTF变换器与岸上三相MMC换流站互联时存在的振荡风险。接着,根据相角灵敏度指标定量评估了不同控制器参数对系统稳定性的影响,并提出用于提升系统稳定性的调参准则。最后,基于MATLAB/Simulink仿真和硬件在环实验验证了结果的正确性。
文摘为了研究模块化多电平换流器(modular multilevel converter,MMC)在嵌入储能系统(battery energy storage system,BESS)后内部动态特性的变化规律,对MMC-BESS的运行特性进行了详细分析,并提出了一种桥臂级平均值模型(arm average model,AAM)进行验证。首先,在假设桥臂中各储能子模块状态一致的前提下,将离散环节连续化,并根据电路特性方程构建了MMC-BESS的AAM电路模型。然后,根据交流端、直流端以及储能端之间的功率关系对MMC-BESS的运行模式进行划分,建立了桥臂电流与电池功率之间的关系,并对电池功率不均衡状态下的桥臂电流进行了分析。最后,利用Matlab/Simulink分别搭建了MMC-BESS的开关模型和AAM模型,并基于AAM验证了多种工况下的桥臂电流响应。仿真结果表明,AAM在显著提高仿真效率的同时可保证较高的准确性,电池功率的大小与均衡状况对桥臂电流的成分有较大影响。
