针对日益复杂的运行情况和可能的极端外部灾害,提出了一种采用扩展等面积准则EEAC(extended equal area criterion)自动识别暂态稳定关键输电断面方法。将稳定裕度小于门槛的故障确定为关键故障,利用暂态稳定仿真动态过程中各线路的功...针对日益复杂的运行情况和可能的极端外部灾害,提出了一种采用扩展等面积准则EEAC(extended equal area criterion)自动识别暂态稳定关键输电断面方法。将稳定裕度小于门槛的故障确定为关键故障,利用暂态稳定仿真动态过程中各线路的功率波动幅度筛选候选断面组成支路,以支路首末端节点中分别同S群和A群连通的节点作为起点和终点,通过拓扑搜索获取所有连接起点和终点的连通路径,优先挑选功率波动幅度较大的连通路径支路构成割集断面,根据机组参与因子的大小确定注入量空间安全域边界进而确定关键断面。所提方法满足在线应用要求,某实际系统的算例验证了其实用性和有效性。展开更多
A mimetic finite difference scheme for the transient heat equation under Robin’s conditions is presented. The scheme uses second order gradient and divergence mimetic operators, on a staggered grid, to approximate th...A mimetic finite difference scheme for the transient heat equation under Robin’s conditions is presented. The scheme uses second order gradient and divergence mimetic operators, on a staggered grid, to approximate the space derivatives. The temporal derivative is replaced by a first order backward difference approximation to obtain an implicit formulation. The resulting scheme contains nonstandard finite difference stencils. An original convergence analysis by the matrix’s method shows that the proposed scheme is unconditionally stable. A comparative study against standard finite difference schemes, based on central difference or first order one side approximations, reveals the advantages of our scheme without being its implementation more expensive or difficult to achieve.展开更多
Spinach is one of the dioecious plant which is considered as a model plant in genetic and molecular studies of sex determination because of its special characteristics such as low chromosome number and short life cycl...Spinach is one of the dioecious plant which is considered as a model plant in genetic and molecular studies of sex determination because of its special characteristics such as low chromosome number and short life cycle. An efficient protocol for Spinacia oleracea Agrobacterium-mediated gene transformation was developed. The leaf disks, roots, hypocotyls and cotyledons of this plant were inoculated with LBA4404. LBA4404 carrying pCAMBIA3301 binary vector with 35SCaMV gusint and 35SCaMV bar cassettes. Effects of two preparation condition (induction of vir genes and noninduction) were considered. Also effects of different number days of co-cultivation and pre-culture of explants were examined. After co-cultivation, the explants were transferred to regeneration medium containing 250 mg·L-1 Carbeniciline. Transient expression efficiency was calculated based on the number of blue spots per explants one week after inoculation. Based on the results of transient expression, stable transformation was carried out. After formation of callus the histochemical GUS assay was carried out on some parts of them and other parts were leaved for being regenerated.展开更多
This paper proposes a fractional-order simplest chaotic system using a bi-stable locally-active memristor.The characteristics of the memristor and transient transition behaviors of the proposed system are analyzed,and...This paper proposes a fractional-order simplest chaotic system using a bi-stable locally-active memristor.The characteristics of the memristor and transient transition behaviors of the proposed system are analyzed,and this circuit is implemented digitally using ARM-based MCU.Firstly,the mathematical model of the memristor is designed,which is nonvolatile,locally-active and bi-stable.Secondly,the asymptotical stability of the fractional-order memristive chaotic system is investigated and some sufficient conditions of the stability are obtained.Thirdly,complex dynamics of the novel system are analyzed using phase diagram,Lyapunov exponential spectrum,bifurcation diagram,basin of attractor,and coexisting bifurcation,coexisting attractors are observed.All of these results indicate that this simple system contains the abundant dynamic characteristics.Moreover,transient transition behaviors of the system are analyzed,and it is found that the behaviors of transient chaotic and transient period transition alternately occur.Finally,the hardware implementation of the fractional-order bi-stable locally-active memristive chaotic system using ARM-based STM32F750 is carried out to verify the numerical simulation results.展开更多
新能源并网逆变器的自同步电压源控制技术对构建以新能源为主体的新型电力系统具有重大意义,然而当弱电网电压发生跌落时,传统的自同步控制方法在低电压穿越(low voltage ride through,LVRT)过程中会出现由于电网阻抗大、相角差大等引...新能源并网逆变器的自同步电压源控制技术对构建以新能源为主体的新型电力系统具有重大意义,然而当弱电网电压发生跌落时,传统的自同步控制方法在低电压穿越(low voltage ride through,LVRT)过程中会出现由于电网阻抗大、相角差大等引起的瞬态电流冲击大、弱电网电压无法维持稳定、电压-电流控制能力须相互平衡等一系列问题。推导了低电压跌落时弱电网电压矢量与弱电网阻抗、并网电流之间的关系以及影响因素,进而提出了一种基于暂稳态阻抗重塑的多状态跟随自同步电压源LVRT控制方法,通过稳态阻抗来平衡电压和电流之间的控制能力;通过暂态阻抗重塑保证了整个过程的电压与电流瞬态控制与平滑过渡能力。为了进一步保证弱网下跌落和恢复过渡过程的平滑切换与稳定运行,提出了基于多状态跟随的暂态控制策略,优先发出无功支撑电网电压,并补偿相角和幅值突变带来的瞬态过电压和过电流冲击,帮助电网电压平稳过渡。最后,在Matlab/Simulink中验证了所提控制方法的正确性与有效性。展开更多
文摘针对日益复杂的运行情况和可能的极端外部灾害,提出了一种采用扩展等面积准则EEAC(extended equal area criterion)自动识别暂态稳定关键输电断面方法。将稳定裕度小于门槛的故障确定为关键故障,利用暂态稳定仿真动态过程中各线路的功率波动幅度筛选候选断面组成支路,以支路首末端节点中分别同S群和A群连通的节点作为起点和终点,通过拓扑搜索获取所有连接起点和终点的连通路径,优先挑选功率波动幅度较大的连通路径支路构成割集断面,根据机组参与因子的大小确定注入量空间安全域边界进而确定关键断面。所提方法满足在线应用要求,某实际系统的算例验证了其实用性和有效性。
文摘A mimetic finite difference scheme for the transient heat equation under Robin’s conditions is presented. The scheme uses second order gradient and divergence mimetic operators, on a staggered grid, to approximate the space derivatives. The temporal derivative is replaced by a first order backward difference approximation to obtain an implicit formulation. The resulting scheme contains nonstandard finite difference stencils. An original convergence analysis by the matrix’s method shows that the proposed scheme is unconditionally stable. A comparative study against standard finite difference schemes, based on central difference or first order one side approximations, reveals the advantages of our scheme without being its implementation more expensive or difficult to achieve.
文摘Spinach is one of the dioecious plant which is considered as a model plant in genetic and molecular studies of sex determination because of its special characteristics such as low chromosome number and short life cycle. An efficient protocol for Spinacia oleracea Agrobacterium-mediated gene transformation was developed. The leaf disks, roots, hypocotyls and cotyledons of this plant were inoculated with LBA4404. LBA4404 carrying pCAMBIA3301 binary vector with 35SCaMV gusint and 35SCaMV bar cassettes. Effects of two preparation condition (induction of vir genes and noninduction) were considered. Also effects of different number days of co-cultivation and pre-culture of explants were examined. After co-cultivation, the explants were transferred to regeneration medium containing 250 mg·L-1 Carbeniciline. Transient expression efficiency was calculated based on the number of blue spots per explants one week after inoculation. Based on the results of transient expression, stable transformation was carried out. After formation of callus the histochemical GUS assay was carried out on some parts of them and other parts were leaved for being regenerated.
文摘This paper proposes a fractional-order simplest chaotic system using a bi-stable locally-active memristor.The characteristics of the memristor and transient transition behaviors of the proposed system are analyzed,and this circuit is implemented digitally using ARM-based MCU.Firstly,the mathematical model of the memristor is designed,which is nonvolatile,locally-active and bi-stable.Secondly,the asymptotical stability of the fractional-order memristive chaotic system is investigated and some sufficient conditions of the stability are obtained.Thirdly,complex dynamics of the novel system are analyzed using phase diagram,Lyapunov exponential spectrum,bifurcation diagram,basin of attractor,and coexisting bifurcation,coexisting attractors are observed.All of these results indicate that this simple system contains the abundant dynamic characteristics.Moreover,transient transition behaviors of the system are analyzed,and it is found that the behaviors of transient chaotic and transient period transition alternately occur.Finally,the hardware implementation of the fractional-order bi-stable locally-active memristive chaotic system using ARM-based STM32F750 is carried out to verify the numerical simulation results.
文摘新能源并网逆变器的自同步电压源控制技术对构建以新能源为主体的新型电力系统具有重大意义,然而当弱电网电压发生跌落时,传统的自同步控制方法在低电压穿越(low voltage ride through,LVRT)过程中会出现由于电网阻抗大、相角差大等引起的瞬态电流冲击大、弱电网电压无法维持稳定、电压-电流控制能力须相互平衡等一系列问题。推导了低电压跌落时弱电网电压矢量与弱电网阻抗、并网电流之间的关系以及影响因素,进而提出了一种基于暂稳态阻抗重塑的多状态跟随自同步电压源LVRT控制方法,通过稳态阻抗来平衡电压和电流之间的控制能力;通过暂态阻抗重塑保证了整个过程的电压与电流瞬态控制与平滑过渡能力。为了进一步保证弱网下跌落和恢复过渡过程的平滑切换与稳定运行,提出了基于多状态跟随的暂态控制策略,优先发出无功支撑电网电压,并补偿相角和幅值突变带来的瞬态过电压和过电流冲击,帮助电网电压平稳过渡。最后,在Matlab/Simulink中验证了所提控制方法的正确性与有效性。
