风电的大规模并网导致系统等效惯量下降、不确定性增加,给电力系统的负荷频率控制(loadfrequency control,LFC)带来新的挑战。考虑到柔性直流输电系统(voltage source converter based high voltage DC,VSC-HVDC)具有的潜在调频能力,对...风电的大规模并网导致系统等效惯量下降、不确定性增加,给电力系统的负荷频率控制(loadfrequency control,LFC)带来新的挑战。考虑到柔性直流输电系统(voltage source converter based high voltage DC,VSC-HVDC)具有的潜在调频能力,对此展开研究,针对风电场经VSC-HVDC并网的情形提出了一种虚拟同步发电机(virtual synchronous generator,VSG)变参数负荷频率控制策略。首先,在风电场经VSC-HVDC并网的LFC模型及拓扑结构分析基础上,为了提高VSC-HVDC的可控性,对换流器的控制环节进行了VSG控制方法的设计;然后,对VSG控制参数与频率变化的关联性进行分析,并基于分数阶梯度下降法(fractional-order gradient descent method,FOGDM),利用频率的分数阶导数提取频率深层变化特征,以优化VSG控制参数;在此基础上,考虑到系统的不确定性,设计触发机制对VSG变参数优化模式进行调整,以降低VSG参数的变换频次,提高系统频率控制的针对性。仿真结果表明:所提控制方法能有效改善电网负荷频率控制效果,具有良好的适应性。展开更多
分布式资源(distributed energy resources,DERs)的随机元素会引起多虚拟电厂(multi-virtual power plant,MVPP)系统内虚拟电厂(virtual power plant,VPP)策略频繁变化。对于某主体,如何感知其他主体策略突然变化时对自身收益的影响趋势...分布式资源(distributed energy resources,DERs)的随机元素会引起多虚拟电厂(multi-virtual power plant,MVPP)系统内虚拟电厂(virtual power plant,VPP)策略频繁变化。对于某主体,如何感知其他主体策略突然变化时对自身收益的影响趋势,并快速调整自身策略,是亟需解决的难点。该文提出基于二阶随机动力学的多虚拟电厂自趋优能量管理策略,旨在提升VPP应对其他主体策略变化时的自治能力。首先,针对DERs异质运行特性,聚焦可调空间构建VPP聚合运行模型;然后,基于随机图描绘VPP策略变化的随机特性;其次,用二阶随机动力学方程(stochastic dynamic equation,SDE)探索VPP收益结构的自发演化信息,修正其他主体策略变化时自身综合收益;再次,将修正收益作为融合软动作-评价(integrated soft actor–critic,ISAC)强化学习算法的奖励搭建多智能体求解框架。最后,设计多算法对比实验,验证了该文策略的自趋优性能。展开更多
Laminated hard-soft integrated structures play a significant role in the fabrication and development of flexible electronics devices. Flexible electronics have advantageous characteristics such as soft and light-weigh...Laminated hard-soft integrated structures play a significant role in the fabrication and development of flexible electronics devices. Flexible electronics have advantageous characteristics such as soft and light-weight, can be folded,twisted, flipped inside-out, or be pasted onto other surfaces of arbitrary shapes. In this paper, an analytical model is presented to study the mechanics of laminated hard-soft structures in flexible electronics under a stickup state. Thirdorder polynomials are used to describe the displacement field,and the principle of virtual work is adopted to derive the governing equations and boundary conditions. The normal strain and the shear stress along the thickness direction in the bimaterial region are obtained analytically, which agree well with the results from finite element analysis. The analytical model can be used to analyze stickup state laminated structures, and can serve as a valuable reference for the failure prediction and optimal design of flexible electronics in the future.展开更多
According to the characteristic of the echo of highfrequency ground wave radar（HF GWR）, which is one-dimensional narrow band signal, a virtual direction of arrival（DOA） matrix is constructed at first, then the DOA...According to the characteristic of the echo of highfrequency ground wave radar（HF GWR）, which is one-dimensional narrow band signal, a virtual direction of arrival（DOA） matrix is constructed at first, then the DOA of target evaluation is achieved by the method of resolving equations for two-dimensional DOA matrix. And this method bases on the redundancy information of a linear two-row array of antennae. Both the simulation process and the treatment results of measured data （in the case of low SNR echoes and short data series） are given at the end of this paper. By comparing with GPS data of the targets, the validity and practical applicability of the method in this paper is verified.展开更多
文摘风电的大规模并网导致系统等效惯量下降、不确定性增加,给电力系统的负荷频率控制(loadfrequency control,LFC)带来新的挑战。考虑到柔性直流输电系统(voltage source converter based high voltage DC,VSC-HVDC)具有的潜在调频能力,对此展开研究,针对风电场经VSC-HVDC并网的情形提出了一种虚拟同步发电机(virtual synchronous generator,VSG)变参数负荷频率控制策略。首先,在风电场经VSC-HVDC并网的LFC模型及拓扑结构分析基础上,为了提高VSC-HVDC的可控性,对换流器的控制环节进行了VSG控制方法的设计;然后,对VSG控制参数与频率变化的关联性进行分析,并基于分数阶梯度下降法(fractional-order gradient descent method,FOGDM),利用频率的分数阶导数提取频率深层变化特征,以优化VSG控制参数;在此基础上,考虑到系统的不确定性,设计触发机制对VSG变参数优化模式进行调整,以降低VSG参数的变换频次,提高系统频率控制的针对性。仿真结果表明:所提控制方法能有效改善电网负荷频率控制效果,具有良好的适应性。
文摘分布式资源(distributed energy resources,DERs)的随机元素会引起多虚拟电厂(multi-virtual power plant,MVPP)系统内虚拟电厂(virtual power plant,VPP)策略频繁变化。对于某主体,如何感知其他主体策略突然变化时对自身收益的影响趋势,并快速调整自身策略,是亟需解决的难点。该文提出基于二阶随机动力学的多虚拟电厂自趋优能量管理策略,旨在提升VPP应对其他主体策略变化时的自治能力。首先,针对DERs异质运行特性,聚焦可调空间构建VPP聚合运行模型;然后,基于随机图描绘VPP策略变化的随机特性;其次,用二阶随机动力学方程(stochastic dynamic equation,SDE)探索VPP收益结构的自发演化信息,修正其他主体策略变化时自身综合收益;再次,将修正收益作为融合软动作-评价(integrated soft actor–critic,ISAC)强化学习算法的奖励搭建多智能体求解框架。最后,设计多算法对比实验,验证了该文策略的自趋优性能。
基金supported by the National Natural Science Foundation of China (Grants 11572022 and 11172022)
文摘Laminated hard-soft integrated structures play a significant role in the fabrication and development of flexible electronics devices. Flexible electronics have advantageous characteristics such as soft and light-weight, can be folded,twisted, flipped inside-out, or be pasted onto other surfaces of arbitrary shapes. In this paper, an analytical model is presented to study the mechanics of laminated hard-soft structures in flexible electronics under a stickup state. Thirdorder polynomials are used to describe the displacement field,and the principle of virtual work is adopted to derive the governing equations and boundary conditions. The normal strain and the shear stress along the thickness direction in the bimaterial region are obtained analytically, which agree well with the results from finite element analysis. The analytical model can be used to analyze stickup state laminated structures, and can serve as a valuable reference for the failure prediction and optimal design of flexible electronics in the future.
基金Supported by the National High Technology and Devel-opment Program of China (2001AA631050)
文摘According to the characteristic of the echo of highfrequency ground wave radar（HF GWR）, which is one-dimensional narrow band signal, a virtual direction of arrival（DOA） matrix is constructed at first, then the DOA of target evaluation is achieved by the method of resolving equations for two-dimensional DOA matrix. And this method bases on the redundancy information of a linear two-row array of antennae. Both the simulation process and the treatment results of measured data （in the case of low SNR echoes and short data series） are given at the end of this paper. By comparing with GPS data of the targets, the validity and practical applicability of the method in this paper is verified.
