高频隔离型双有源桥(dual active bridge,DAB)变换器是电力电子变压器(power electronic transformer,PET)的核心设备之一。其中,高频链的存在以及高开关频率特性,使得PET电磁暂态仿真效率较低。该文对先前研究提出的DAB型变换器积分解...高频隔离型双有源桥(dual active bridge,DAB)变换器是电力电子变压器(power electronic transformer,PET)的核心设备之一。其中,高频链的存在以及高开关频率特性,使得PET电磁暂态仿真效率较低。该文对先前研究提出的DAB型变换器积分解耦算法进行稳定性与截断误差分析,以提高该方法的可信度。首先,建立DAB简化电路并列写其状态方程;其次,选取特殊对称矩阵,利用Lyapunov直接法分析前向欧拉、梯形积分和积分解耦方法下连续系统与离散系统的稳定性,计算不同积分方法的局部截断误差,建立相对均方根误差作为全局误差的衡量指标;并结合实际变压器参数取值,分析不同积分方法对仿真步长的约束;最后,在PSCAD/EMTDC中,进行稳定性与误差验证。结果表明,积分解耦法和梯形积分法的稳定性与截断误差均不会对仿真步长产生附加约束。展开更多
By using Richardson extrapolation and fourth-order compact finite difference scheme on different scale grids, a sixth-order solution is computed on the coarse grid. Other three techniques are applied to obtain a sixth...By using Richardson extrapolation and fourth-order compact finite difference scheme on different scale grids, a sixth-order solution is computed on the coarse grid. Other three techniques are applied to obtain a sixth-order solution on the fine grid, and thus give out three kinds of Richardson extrapolation-based sixth order compact computation methods. By carefully analyzing the truncation errors respectively on 2D Poisson equation, we compare the accuracy of these three sixth order methods theoretically. Numerical results for two test problems are discussed.展开更多
In this paper,we consider high order multi-domain penalty spectral Galerkin methods for the approximation of hyperbolic conservation laws.This formulation has a penalty parameter which can vary in space and time,allow...In this paper,we consider high order multi-domain penalty spectral Galerkin methods for the approximation of hyperbolic conservation laws.This formulation has a penalty parameter which can vary in space and time,allowing for flexibility in the penalty formulation.This flexibility is particularly advantageous for problems with an inhomogeneous mesh.We show that the discontinuous Galerkin method is equivalent to the multi-domain spectral penalty Galerkin method with a particular value of the penalty parameter.The penalty parameter has an effect on both the accuracy and stability of the method.We examine the numerical issues which arise in the implementation of high order multi-domain penalty spectral Galerkin methods.The coefficient truncation method is proposed to prevent the rapid error growth due to round-off errors when high order polynomials are used.Finally,we show that an inconsistent evaluation of the integrals in the penalty method may lead to growth of errors.Numerical examples for linear and nonlinear problems are presented.展开更多
文摘为了解决高速数字接收机中混频数据处理能力有限的问题,设计了基于八分圆周矢量旋转(OCVR)的高速数字正交混频器.该混频器仅通过简单二进制补码运算器和移位加法器即可实现,且不需要进行迭代运算.分析比较了常规的基于ROM架构、基于直接坐标旋转数字计算机(CORDIC)架构以及基于OCVR架构的混频器,结果显示基于OCVR的混频器拥有更高的数据吞吐量、更低的硬件资源消耗以及混频噪声小等特点.根据OCVR特性设计了武汉电离层斜向返回探测系统(WIOBSS)的中频(IF)数字接收机,该系统可以获取实时的宽带扫频后向散射电离图.实验证明该系统的探测覆盖范围已经延伸至3 000 km.
文摘高频隔离型双有源桥(dual active bridge,DAB)变换器是电力电子变压器(power electronic transformer,PET)的核心设备之一。其中,高频链的存在以及高开关频率特性,使得PET电磁暂态仿真效率较低。该文对先前研究提出的DAB型变换器积分解耦算法进行稳定性与截断误差分析,以提高该方法的可信度。首先,建立DAB简化电路并列写其状态方程;其次,选取特殊对称矩阵,利用Lyapunov直接法分析前向欧拉、梯形积分和积分解耦方法下连续系统与离散系统的稳定性,计算不同积分方法的局部截断误差,建立相对均方根误差作为全局误差的衡量指标;并结合实际变压器参数取值,分析不同积分方法对仿真步长的约束;最后,在PSCAD/EMTDC中,进行稳定性与误差验证。结果表明,积分解耦法和梯形积分法的稳定性与截断误差均不会对仿真步长产生附加约束。
文摘By using Richardson extrapolation and fourth-order compact finite difference scheme on different scale grids, a sixth-order solution is computed on the coarse grid. Other three techniques are applied to obtain a sixth-order solution on the fine grid, and thus give out three kinds of Richardson extrapolation-based sixth order compact computation methods. By carefully analyzing the truncation errors respectively on 2D Poisson equation, we compare the accuracy of these three sixth order methods theoretically. Numerical results for two test problems are discussed.
基金The work of both authors has been supported by the NSF under Grant No.DMS-0608844.
文摘In this paper,we consider high order multi-domain penalty spectral Galerkin methods for the approximation of hyperbolic conservation laws.This formulation has a penalty parameter which can vary in space and time,allowing for flexibility in the penalty formulation.This flexibility is particularly advantageous for problems with an inhomogeneous mesh.We show that the discontinuous Galerkin method is equivalent to the multi-domain spectral penalty Galerkin method with a particular value of the penalty parameter.The penalty parameter has an effect on both the accuracy and stability of the method.We examine the numerical issues which arise in the implementation of high order multi-domain penalty spectral Galerkin methods.The coefficient truncation method is proposed to prevent the rapid error growth due to round-off errors when high order polynomials are used.Finally,we show that an inconsistent evaluation of the integrals in the penalty method may lead to growth of errors.Numerical examples for linear and nonlinear problems are presented.
