Based on the full domain partition, a parallel finite element algorithm for the stationary Stokes equations is proposed and analyzed. In this algorithm, each subproblem is defined in the entire domain. Majority of the...Based on the full domain partition, a parallel finite element algorithm for the stationary Stokes equations is proposed and analyzed. In this algorithm, each subproblem is defined in the entire domain. Majority of the degrees of freedom are associated with the relevant subdomain. Therefore, it can be solved in parallel with other subproblems using an existing sequential solver without extensive recoding. This allows the algorithm to be implemented easily with low communication costs. Numerical results are given showing the high efficiency of the parallel algorithm.展开更多
Conventional gradient-based full waveform inversion (FWI) is a local optimization, which is highly dependent on the initial model and prone to trapping in local minima. Globally optimal FWI that can overcome this limi...Conventional gradient-based full waveform inversion (FWI) is a local optimization, which is highly dependent on the initial model and prone to trapping in local minima. Globally optimal FWI that can overcome this limitation is particularly attractive, but is currently limited by the huge amount of calculation. In this paper, we propose a globally optimal FWI framework based on GPU parallel computing, which greatly improves the efficiency, and is expected to make globally optimal FWI more widely used. In this framework, we simplify and recombine the model parameters, and optimize the model iteratively. Each iteration contains hundreds of individuals, each individual is independent of the other, and each individual contains forward modeling and cost function calculation. The framework is suitable for a variety of globally optimal algorithms, and we test the framework with particle swarm optimization algorithm for example. Both the synthetic and field examples achieve good results, indicating the effectiveness of the framework. .展开更多
模块化多电平换流器高压直流输电（modular multilevel converter based HVDC,MMC-HVDC）面临半桥子模块拓扑不能清除直流故障电流和子模块电容电压排序计算量过大、对传感器实时性要求高等问题。有文献针对低压领域MMC应用中存在的负...模块化多电平换流器高压直流输电（modular multilevel converter based HVDC,MMC-HVDC）面临半桥子模块拓扑不能清除直流故障电流和子模块电容电压排序计算量过大、对传感器实时性要求高等问题。有文献针对低压领域MMC应用中存在的负荷电流过大、电容电压监测困难等问题,提出并联全桥子模块（paralleled full bridge sub-module,P-FBSM）拓扑,对MMC-HVDC具有借鉴意义。该文从P-FBSM结构出发,分析其开关状态集,进而推导以开关函数表示的并联全桥MMC桥臂模型;基于最近电平逼近调制,设计P-FBSM动态分配均压控制策略,实现无需子模块电容电压的自均压控制,有效减小控制器计算量、降低传感器实时性要求。最后,在PSCAD/EMTDC中的电磁暂态仿真结果表明,采用所提均压控制策略可同时实现子模块电容电压的自均衡和直流故障电流快速清除。展开更多
基金Project supported by the National Natural Science Foundation of China (No.10971166)the National Basic Research Program (No.2005CB321703)the Science and Technology Foundation of Guizhou Province of China (No.[2008]2123)
文摘Based on the full domain partition, a parallel finite element algorithm for the stationary Stokes equations is proposed and analyzed. In this algorithm, each subproblem is defined in the entire domain. Majority of the degrees of freedom are associated with the relevant subdomain. Therefore, it can be solved in parallel with other subproblems using an existing sequential solver without extensive recoding. This allows the algorithm to be implemented easily with low communication costs. Numerical results are given showing the high efficiency of the parallel algorithm.
文摘Conventional gradient-based full waveform inversion (FWI) is a local optimization, which is highly dependent on the initial model and prone to trapping in local minima. Globally optimal FWI that can overcome this limitation is particularly attractive, but is currently limited by the huge amount of calculation. In this paper, we propose a globally optimal FWI framework based on GPU parallel computing, which greatly improves the efficiency, and is expected to make globally optimal FWI more widely used. In this framework, we simplify and recombine the model parameters, and optimize the model iteratively. Each iteration contains hundreds of individuals, each individual is independent of the other, and each individual contains forward modeling and cost function calculation. The framework is suitable for a variety of globally optimal algorithms, and we test the framework with particle swarm optimization algorithm for example. Both the synthetic and field examples achieve good results, indicating the effectiveness of the framework. .
文摘模块化多电平换流器高压直流输电（modular multilevel converter based HVDC,MMC-HVDC）面临半桥子模块拓扑不能清除直流故障电流和子模块电容电压排序计算量过大、对传感器实时性要求高等问题。有文献针对低压领域MMC应用中存在的负荷电流过大、电容电压监测困难等问题,提出并联全桥子模块（paralleled full bridge sub-module,P-FBSM）拓扑,对MMC-HVDC具有借鉴意义。该文从P-FBSM结构出发,分析其开关状态集,进而推导以开关函数表示的并联全桥MMC桥臂模型;基于最近电平逼近调制,设计P-FBSM动态分配均压控制策略,实现无需子模块电容电压的自均压控制,有效减小控制器计算量、降低传感器实时性要求。最后,在PSCAD/EMTDC中的电磁暂态仿真结果表明,采用所提均压控制策略可同时实现子模块电容电压的自均衡和直流故障电流快速清除。
