Combination of multiple-input multiple-output (MIMO) with orthogonal frequency division multiplexing (OFDM) has become a promising candidate for high performance wireless communications. However one major disadvantage...Combination of multiple-input multiple-output (MIMO) with orthogonal frequency division multiplexing (OFDM) has become a promising candidate for high performance wireless communications. However one major disadvantage of MIMO-OFDM systems lies in a prohibitively large peak-to-average power ratio (PAPR) of the transmitted signal on each antenna. In this paper we extend from SISO to MIMO systems a method based on allocating dedicated subcarriers for PAPR mitigation. These subcarriers are located on unused subcarriers of OFDM spectrum under the assumption they all fall under the power mask. This is originally implemented with a SOCP optimization algorithm applied before space time coding scheme. This jointly mitigates PAPR on each MIMO branch scheme. This approach does not degrade the bit-error-rate (BER) and the data bit rate and no side information (SI) transmission is required. Simulation results are presented in the IEEE 802.16 WiMAX standard contexts: an Alamouti space time code with two transmitted antennas and 256 OFDM subcarriers are considered where 56 of which are unused and allocated for PAPR reduction. PAPR gains up to 7dB are obtained depending on mean power increase limitation. Moreover, with a spectrum mask constraint, this method is standard compliant.展开更多
经逆变器接入配电网的分布式电源提供有功与无功辅助服务是确保配电网安全经济运行的重要手段。该文同时计及了储能系统、可投切电容电抗器、有载调压变压器分接头、静止无功补偿器调节能力,以储能与网络损耗及弃风弃光最小为目标函数,...经逆变器接入配电网的分布式电源提供有功与无功辅助服务是确保配电网安全经济运行的重要手段。该文同时计及了储能系统、可投切电容电抗器、有载调压变压器分接头、静止无功补偿器调节能力,以储能与网络损耗及弃风弃光最小为目标函数,计及运行约束,基于支路潮流方程构建了部分分布式电源提供辅助服务的多时段二阶段混合整数二阶锥鲁棒优化模型,提出了一种新颖的基于割平面的主、次问题二阶段直接交替迭代求解方法。不同于现有列与约束生成(columns and constraints generation,CCG)算法,该方法求解主问题时无需增加新的变量与约束条件,求解次问题时,只需针对每个时段进行求解,因此极大降低了求解复杂度与计算机内存。若求解结果不满足二阶锥精确凸松弛条件,则构建二阶段混合整数序列二阶锥鲁棒优化模型,依然能够快速求解,且可恢复出原问题的精确解。最后,采用2个仿真实例验证了所提出方法的性能。IEEE 123节点配电网的仿真结果表明,该方法计算速度是CCG算法的12~22倍。该方法可为含高比例间歇性分布式电源配电网鲁棒优化运行提供实时快速分析与求解工具,提高新能源就地消纳能力。展开更多
In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a gene...In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner(HR)variational principle,creating an implicit PFEM formulation.To mitigate the volumetric locking issue in low-order elements,we employ a node-based strain smoothing technique.By discretising field variables at the centre of smoothing cells,we achieve nodal integration over cells,eliminating the need for sophisticated mapping operations after re-meshing in the PFEM.We express the discretised governing equations as a min-max optimisation problem,which is further reformulated as a standard second-order cone programming(SOCP)problem.Stresses,pore water pressure,and displacements are simultaneously determined using the advanced primal-dual interior point method.Consequently,our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation.Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy,obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches.This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.展开更多
随着多个微电网接入主动配电网(acitve distribution network, ADN)系统运行,微电网与ADN之间的相互作用关系越加明显,使得求解ADN系统经济调度难度加大。为更好平衡微电网和ADN的经济关系,提高ADN系统的经济调度求解效率,提出一种考虑...随着多个微电网接入主动配电网(acitve distribution network, ADN)系统运行,微电网与ADN之间的相互作用关系越加明显,使得求解ADN系统经济调度难度加大。为更好平衡微电网和ADN的经济关系,提高ADN系统的经济调度求解效率,提出一种考虑分时电价机制的多微电网与ADN双层模型。根据优化目标的不同,将整个ADN系统分为上、下层,层与层通过联络线的传输功率来实现整个系统的最优调度。其中下层以各微电网内可控电源出力、买/卖电收益及有功平衡为约束建立并网微电网的数学模型,采用基于Tent映射和正态分布交叉(normal distribution crossover, NDX)算子结合非支配排序遗传算法Ⅱ (non-dominated sorting in genetic algorithm-II,NSGA-II)求解。上层以ADN系统买/卖电的功率和ADN系统最优潮流为约束建立ADN系统最优潮流模型,通过二阶锥规划(second order cone programming, SOCP)松弛技术与Gurobi工具求解系统最优解。最后以改进IEEE 33节点的配电网系统作为算例进行验证,结果表明:所提的双层模型具有一定的可行性;与固态电价下的ADN系统经济性相比,动态分时电价机制下ADN系统的经济性更好。展开更多
文摘Combination of multiple-input multiple-output (MIMO) with orthogonal frequency division multiplexing (OFDM) has become a promising candidate for high performance wireless communications. However one major disadvantage of MIMO-OFDM systems lies in a prohibitively large peak-to-average power ratio (PAPR) of the transmitted signal on each antenna. In this paper we extend from SISO to MIMO systems a method based on allocating dedicated subcarriers for PAPR mitigation. These subcarriers are located on unused subcarriers of OFDM spectrum under the assumption they all fall under the power mask. This is originally implemented with a SOCP optimization algorithm applied before space time coding scheme. This jointly mitigates PAPR on each MIMO branch scheme. This approach does not degrade the bit-error-rate (BER) and the data bit rate and no side information (SI) transmission is required. Simulation results are presented in the IEEE 802.16 WiMAX standard contexts: an Alamouti space time code with two transmitted antennas and 256 OFDM subcarriers are considered where 56 of which are unused and allocated for PAPR reduction. PAPR gains up to 7dB are obtained depending on mean power increase limitation. Moreover, with a spectrum mask constraint, this method is standard compliant.
文摘经逆变器接入配电网的分布式电源提供有功与无功辅助服务是确保配电网安全经济运行的重要手段。该文同时计及了储能系统、可投切电容电抗器、有载调压变压器分接头、静止无功补偿器调节能力,以储能与网络损耗及弃风弃光最小为目标函数,计及运行约束,基于支路潮流方程构建了部分分布式电源提供辅助服务的多时段二阶段混合整数二阶锥鲁棒优化模型,提出了一种新颖的基于割平面的主、次问题二阶段直接交替迭代求解方法。不同于现有列与约束生成(columns and constraints generation,CCG)算法,该方法求解主问题时无需增加新的变量与约束条件,求解次问题时,只需针对每个时段进行求解,因此极大降低了求解复杂度与计算机内存。若求解结果不满足二阶锥精确凸松弛条件,则构建二阶段混合整数序列二阶锥鲁棒优化模型,依然能够快速求解,且可恢复出原问题的精确解。最后,采用2个仿真实例验证了所提出方法的性能。IEEE 123节点配电网的仿真结果表明,该方法计算速度是CCG算法的12~22倍。该方法可为含高比例间歇性分布式电源配电网鲁棒优化运行提供实时快速分析与求解工具,提高新能源就地消纳能力。
基金supported by the Swiss National Science Foundation(Grant No.189882)the National Natural Science Foundation of China(Grant No.41961134032)support provided by the New Investigator Award grant from the UK Engineering and Physical Sciences Research Council(Grant No.EP/V012169/1).
文摘In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner(HR)variational principle,creating an implicit PFEM formulation.To mitigate the volumetric locking issue in low-order elements,we employ a node-based strain smoothing technique.By discretising field variables at the centre of smoothing cells,we achieve nodal integration over cells,eliminating the need for sophisticated mapping operations after re-meshing in the PFEM.We express the discretised governing equations as a min-max optimisation problem,which is further reformulated as a standard second-order cone programming(SOCP)problem.Stresses,pore water pressure,and displacements are simultaneously determined using the advanced primal-dual interior point method.Consequently,our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation.Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy,obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches.This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.
文摘随着多个微电网接入主动配电网(acitve distribution network, ADN)系统运行,微电网与ADN之间的相互作用关系越加明显,使得求解ADN系统经济调度难度加大。为更好平衡微电网和ADN的经济关系,提高ADN系统的经济调度求解效率,提出一种考虑分时电价机制的多微电网与ADN双层模型。根据优化目标的不同,将整个ADN系统分为上、下层,层与层通过联络线的传输功率来实现整个系统的最优调度。其中下层以各微电网内可控电源出力、买/卖电收益及有功平衡为约束建立并网微电网的数学模型,采用基于Tent映射和正态分布交叉(normal distribution crossover, NDX)算子结合非支配排序遗传算法Ⅱ (non-dominated sorting in genetic algorithm-II,NSGA-II)求解。上层以ADN系统买/卖电的功率和ADN系统最优潮流为约束建立ADN系统最优潮流模型,通过二阶锥规划(second order cone programming, SOCP)松弛技术与Gurobi工具求解系统最优解。最后以改进IEEE 33节点的配电网系统作为算例进行验证,结果表明:所提的双层模型具有一定的可行性;与固态电价下的ADN系统经济性相比,动态分时电价机制下ADN系统的经济性更好。
