Based on the framework of critical state soil mechanics,a subloading surface plastic model for sand, being applicable to cyclic loading, was proposed. The model can be used to describe strain softening behaviour of sa...Based on the framework of critical state soil mechanics,a subloading surface plastic model for sand, being applicable to cyclic loading, was proposed. The model can be used to describe strain softening behaviour of sand under monotonic loading when the similarity-ratio equals to unity. The characteristics of the model are as follows: 1) A reverse bullet-shaped yield surface is adopted to ensure accurate prediction of the behavior of sand, instead of bullet-shaped or elliptical yield surface in Cam-Clay model. 2) No unique relationship between void ratio and the mean normal stress for sand prevents the direct coupling of yield surface size to void ratio, so incremental deviatoric strain hardening rule is used. 3) The model combines the concept of state-dependent dilatancy by incorporating state parameter in Rowe's stress dilatancy equation, which accounts for the dependence of dilatancy on the stress state and the material internal state. A single set of model constants, which is calibrated, can simulate stress-strain response under different initial void ratios and different confine pressures. The model is validated true by comparing predicted results with experimental results under monotonic and cyclic loading conditions.展开更多
针对高比例新能源电力系统,基于模型参数的电压支撑强度量化方法已具有较为深入的方法和结论,但是尚缺乏基于本地响应信息的电压支撑强度实时量化方法,电压支撑强度就地监测水平亟待提高。该文提出电压支撑强度实时量化方法,实现短路比...针对高比例新能源电力系统,基于模型参数的电压支撑强度量化方法已具有较为深入的方法和结论,但是尚缺乏基于本地响应信息的电压支撑强度实时量化方法,电压支撑强度就地监测水平亟待提高。该文提出电压支撑强度实时量化方法,实现短路比实时计算,及时给出安全预警信号,为提高新能源系统安全运行水平提供技术支撑。首先,构建实时短路比(real-time short circuit ratio,RSCR)及临界实时短路比(critical real-time short circuit ratio,CRSCR)指标,实现基于本地响应信息的短路比指标实时计算,提供电压支撑强度实时量测的指标基础;其次,提出有功功率裕度、稳态低电压两类安全约束下的RSCR裕度分析方法,通过建立RSCR与功率、电压之间的函数关系分析不同安全约束下RSCR裕度的适应性,为设置安全预警阈值提供参考;然后,构建实时量测系统架构,提出涵盖系统戴维南等值参数实时辨识、短路比指标实时计算、实时安全预警等功能的算法流程,建立电压支撑强度全流程实时量测方法;最后,通过算例验证RSCR、CRSCR的准确性以及实时量测方法的有效性。实现基于实时量测信息的电压支撑强度就地监测,可以为运维人员及时掌握新能源运行状态提供一定指导,支撑更高比例新能源并网消纳。展开更多
基金Project(07JCZDJC09800) supported by Tianjin Natural Science FoundationProject(07FDZDSF01200) supported by Tianjin Science and Technology Innovation Special Funds
文摘Based on the framework of critical state soil mechanics,a subloading surface plastic model for sand, being applicable to cyclic loading, was proposed. The model can be used to describe strain softening behaviour of sand under monotonic loading when the similarity-ratio equals to unity. The characteristics of the model are as follows: 1) A reverse bullet-shaped yield surface is adopted to ensure accurate prediction of the behavior of sand, instead of bullet-shaped or elliptical yield surface in Cam-Clay model. 2) No unique relationship between void ratio and the mean normal stress for sand prevents the direct coupling of yield surface size to void ratio, so incremental deviatoric strain hardening rule is used. 3) The model combines the concept of state-dependent dilatancy by incorporating state parameter in Rowe's stress dilatancy equation, which accounts for the dependence of dilatancy on the stress state and the material internal state. A single set of model constants, which is calibrated, can simulate stress-strain response under different initial void ratios and different confine pressures. The model is validated true by comparing predicted results with experimental results under monotonic and cyclic loading conditions.
文摘针对高比例新能源电力系统,基于模型参数的电压支撑强度量化方法已具有较为深入的方法和结论,但是尚缺乏基于本地响应信息的电压支撑强度实时量化方法,电压支撑强度就地监测水平亟待提高。该文提出电压支撑强度实时量化方法,实现短路比实时计算,及时给出安全预警信号,为提高新能源系统安全运行水平提供技术支撑。首先,构建实时短路比(real-time short circuit ratio,RSCR)及临界实时短路比(critical real-time short circuit ratio,CRSCR)指标,实现基于本地响应信息的短路比指标实时计算,提供电压支撑强度实时量测的指标基础;其次,提出有功功率裕度、稳态低电压两类安全约束下的RSCR裕度分析方法,通过建立RSCR与功率、电压之间的函数关系分析不同安全约束下RSCR裕度的适应性,为设置安全预警阈值提供参考;然后,构建实时量测系统架构,提出涵盖系统戴维南等值参数实时辨识、短路比指标实时计算、实时安全预警等功能的算法流程,建立电压支撑强度全流程实时量测方法;最后,通过算例验证RSCR、CRSCR的准确性以及实时量测方法的有效性。实现基于实时量测信息的电压支撑强度就地监测,可以为运维人员及时掌握新能源运行状态提供一定指导,支撑更高比例新能源并网消纳。
