A significant geologic event occurred on the Oligocene/Miocene boundary at 23.8 Ma in the northern South China Sea, which is named the Baiyun （白云） movement in this article. This event strongly affected not only th...A significant geologic event occurred on the Oligocene/Miocene boundary at 23.8 Ma in the northern South China Sea, which is named the Baiyun （白云） movement in this article. This event strongly affected not only the South China Sea, but also East Asia. After the Baiyun event, the ridge of seafloor spreading of the South China Sea jumped southward and rotated counterclockwise, and a strong subsidence occurred in the Baiyun sag of the Pearl River Mouth basin. The shelf break shifted suddenly from the south to the north of the Baiyun sag, and the deposition environment in this sag changed from continental shelf with neritic deposition to continental slope with deep-water deposition. Sediment geochemistry study indicated that the Baiyun event played a key role in the rapid change of sediment provenance for the Pearl River Mouth basin. Between 32 and 23.8 Ma, the source of sediments was mainly from the granites in South China, while after 23.8 Ma some sediments might have come from the eastern Himalaya, as the Pearl River drainage extended westward after the uplift of Tibet since that time. The Baiyun event led to a great change in the drainage framework of the paleo- Pearl River, sediment types and the depositional environments in the Pearl River Mouth basin, and relative sea level of the northern South China Sea, as well as sedimentation and hydrocarbon accumulation in the area.展开更多
对换流站的控制能够实现多端柔直系统在电网调频过程中的相互支撑。但不同扰动下,需考虑换流站的功率裕度及频率、电压之间的耦合性,以提升多端柔性直流输电(multi-terminal flexible direct current transmission systems,MTDC)系统的...对换流站的控制能够实现多端柔直系统在电网调频过程中的相互支撑。但不同扰动下,需考虑换流站的功率裕度及频率、电压之间的耦合性,以提升多端柔性直流输电(multi-terminal flexible direct current transmission systems,MTDC)系统的调频能力。该文对此展开研究,首先,根据各区域频率、直流电压及传输功率等信息,以各VSC在分担不平衡功率时的参与度一致、频率偏差变化率最小为目标设计触发规则,作为是否进行改进下垂控制策略切换的依据。其次,触发事件发生后,为减小传统P-Udc-f下垂控制中电压、频率的耦合,控制受扰区域换流站工作在P-f下垂控制模式,未受扰区域换流站工作在P-Udc下垂控制模式;并在常规下垂系数设置基础上,设计考虑换流站(voltage source converter,VSC)的功率裕度因子等因素的下垂系数调整举措。仿真结果表明,所提策略能有效均衡各VSC分担不平衡功率时的参与度,减小直流电压及各区域频率偏差。展开更多
基金supported by the National Natural Science Foundation of China (No. 40238060)
文摘A significant geologic event occurred on the Oligocene/Miocene boundary at 23.8 Ma in the northern South China Sea, which is named the Baiyun （白云） movement in this article. This event strongly affected not only the South China Sea, but also East Asia. After the Baiyun event, the ridge of seafloor spreading of the South China Sea jumped southward and rotated counterclockwise, and a strong subsidence occurred in the Baiyun sag of the Pearl River Mouth basin. The shelf break shifted suddenly from the south to the north of the Baiyun sag, and the deposition environment in this sag changed from continental shelf with neritic deposition to continental slope with deep-water deposition. Sediment geochemistry study indicated that the Baiyun event played a key role in the rapid change of sediment provenance for the Pearl River Mouth basin. Between 32 and 23.8 Ma, the source of sediments was mainly from the granites in South China, while after 23.8 Ma some sediments might have come from the eastern Himalaya, as the Pearl River drainage extended westward after the uplift of Tibet since that time. The Baiyun event led to a great change in the drainage framework of the paleo- Pearl River, sediment types and the depositional environments in the Pearl River Mouth basin, and relative sea level of the northern South China Sea, as well as sedimentation and hydrocarbon accumulation in the area.
文摘对换流站的控制能够实现多端柔直系统在电网调频过程中的相互支撑。但不同扰动下,需考虑换流站的功率裕度及频率、电压之间的耦合性,以提升多端柔性直流输电(multi-terminal flexible direct current transmission systems,MTDC)系统的调频能力。该文对此展开研究,首先,根据各区域频率、直流电压及传输功率等信息,以各VSC在分担不平衡功率时的参与度一致、频率偏差变化率最小为目标设计触发规则,作为是否进行改进下垂控制策略切换的依据。其次,触发事件发生后,为减小传统P-Udc-f下垂控制中电压、频率的耦合,控制受扰区域换流站工作在P-f下垂控制模式,未受扰区域换流站工作在P-Udc下垂控制模式;并在常规下垂系数设置基础上,设计考虑换流站(voltage source converter,VSC)的功率裕度因子等因素的下垂系数调整举措。仿真结果表明,所提策略能有效均衡各VSC分担不平衡功率时的参与度,减小直流电压及各区域频率偏差。
