Lossy power flow naturally extends lossless linear power flow to lossy distribution networks,further improving the accuracy of approximate computation and analysis.However,these enhanced versions are only applicable a...Lossy power flow naturally extends lossless linear power flow to lossy distribution networks,further improving the accuracy of approximate computation and analysis.However,these enhanced versions are only applicable at the alternating current(AC)transmission level,and the accuracy is limited in distribution networks,especially in hybrid AC-direct current(DC)distribution networks.In this paper,we revisit the lossy power flow model and extend it to hybrid AC-DC distribution networks with multi-terminal voltage source converters.The proposed lossy power flow model can be reformulated as an iteration problem with node power injection as the fixed point.For this purpose,a node power injection modification model based on direct derivation is proposed by exploiting the negligibility of the phase angle differences,and iteratively solving lossy power flows for both AC and DC sub-networks.For coupling devices,to guarantee that the power flow is matched on both AC and DC sides,we formulate a rigorous fixed-point problem to solve the lossy power flow of voltage source converters.Finally,the high accuracy and computational efficiency of the proposed model are verified on multiple test cases.展开更多
文章设计了一种基于远距离无线电(Long Range Radio,LoRa)技术的水情信息无线传输系统,构建了感知层、网络传输层、边缘处理层和平台服务层的多层架构。文章通过低功耗多参数采集节点、自适应通信机制与边缘计算融合,实现了复杂环境下...文章设计了一种基于远距离无线电(Long Range Radio,LoRa)技术的水情信息无线传输系统,构建了感知层、网络传输层、边缘处理层和平台服务层的多层架构。文章通过低功耗多参数采集节点、自适应通信机制与边缘计算融合,实现了复杂环境下水情数据的高效获取与智能处理。系统引入轻量级抗冲突协议与边缘异常识别模型,提升了传输可靠性与响应能力。结合网络模拟器3(Network Simulator 3,NS-3)仿真平台对不同地形与节点密度下系统性能进行量化评估,结果表明该系统在典型水情场景中具备良好的通信稳定性、可扩展性与抗干扰能力,验证了其在实际部署中的可行性和实用价值。展开更多
配电网中关键节点与主干线路的失效可能引发电网大规模故障,对供电可靠性构成严重威胁。为有效识别配电网薄弱环节,提出一套适用于网架数字化建模与脆弱性评估的节点与线路脆弱性指标体系。对于节点脆弱性评估,除对传统指标(如节点度数...配电网中关键节点与主干线路的失效可能引发电网大规模故障,对供电可靠性构成严重威胁。为有效识别配电网薄弱环节,提出一套适用于网架数字化建模与脆弱性评估的节点与线路脆弱性指标体系。对于节点脆弱性评估,除对传统指标(如节点度数、节点介数、节点紧密中心度、节点注入功率及电压偏离度)进行优化外,进一步引入基于空间直接估计(spatial direct estimation,SDE)的结构脆弱性指标,以及考虑线路越限风险的抗扰动脆弱性指标;对于线路脆弱性评估,构建了线路度数、线路介数和线路SDE三类指标。基于上述指标体系,采用熵权法与直接赋权法分别确定节点与线路脆弱度权重,进而计算节点与线路的综合脆弱性评分。最后,以IEEE33节点系统和某中型城市中心城区实际配电网为例进行仿真验证,结果表明所提方法能有效辨识配电网节点与线路的薄弱环节,及时发现潜在运行隐患。展开更多
We report a novel battery-less wireless current sensor node without an analog to digital converter (ADC). If a capacitor is charged using a current transformer (CT) and a rectifying circuit, the charging time depends ...We report a novel battery-less wireless current sensor node without an analog to digital converter (ADC). If a capacitor is charged using a current transformer (CT) and a rectifying circuit, the charging time depends on the current flowing through a power line. In the case that the node transmits data every time when voltage of the capacitor exceeds a threshold voltage, we can indirectly measure the current by measuring the transmission intervals. In this method, the circuit of the node can be simplified and power consumption for the wireless transmission can be decreased because the measured current data does not need to be included in the transmitted packet. However, the measurable range is about single digit because the transmission interval decreases suddenly as the current increases. In this work, we have ex- panded the range using one CT, one wireless transmission module, and two charging circuits that include different load resistors connected in series. The results indicated that the measurable range was from 0.5 A to 50 A.展开更多
基金supported by the National Natural Science Foundation of China(No.52022016).
文摘Lossy power flow naturally extends lossless linear power flow to lossy distribution networks,further improving the accuracy of approximate computation and analysis.However,these enhanced versions are only applicable at the alternating current(AC)transmission level,and the accuracy is limited in distribution networks,especially in hybrid AC-direct current(DC)distribution networks.In this paper,we revisit the lossy power flow model and extend it to hybrid AC-DC distribution networks with multi-terminal voltage source converters.The proposed lossy power flow model can be reformulated as an iteration problem with node power injection as the fixed point.For this purpose,a node power injection modification model based on direct derivation is proposed by exploiting the negligibility of the phase angle differences,and iteratively solving lossy power flows for both AC and DC sub-networks.For coupling devices,to guarantee that the power flow is matched on both AC and DC sides,we formulate a rigorous fixed-point problem to solve the lossy power flow of voltage source converters.Finally,the high accuracy and computational efficiency of the proposed model are verified on multiple test cases.
文摘文章设计了一种基于远距离无线电(Long Range Radio,LoRa)技术的水情信息无线传输系统,构建了感知层、网络传输层、边缘处理层和平台服务层的多层架构。文章通过低功耗多参数采集节点、自适应通信机制与边缘计算融合,实现了复杂环境下水情数据的高效获取与智能处理。系统引入轻量级抗冲突协议与边缘异常识别模型,提升了传输可靠性与响应能力。结合网络模拟器3(Network Simulator 3,NS-3)仿真平台对不同地形与节点密度下系统性能进行量化评估,结果表明该系统在典型水情场景中具备良好的通信稳定性、可扩展性与抗干扰能力,验证了其在实际部署中的可行性和实用价值。
文摘配电网中关键节点与主干线路的失效可能引发电网大规模故障,对供电可靠性构成严重威胁。为有效识别配电网薄弱环节,提出一套适用于网架数字化建模与脆弱性评估的节点与线路脆弱性指标体系。对于节点脆弱性评估,除对传统指标(如节点度数、节点介数、节点紧密中心度、节点注入功率及电压偏离度)进行优化外,进一步引入基于空间直接估计(spatial direct estimation,SDE)的结构脆弱性指标,以及考虑线路越限风险的抗扰动脆弱性指标;对于线路脆弱性评估,构建了线路度数、线路介数和线路SDE三类指标。基于上述指标体系,采用熵权法与直接赋权法分别确定节点与线路脆弱度权重,进而计算节点与线路的综合脆弱性评分。最后,以IEEE33节点系统和某中型城市中心城区实际配电网为例进行仿真验证,结果表明所提方法能有效辨识配电网节点与线路的薄弱环节,及时发现潜在运行隐患。
文摘We report a novel battery-less wireless current sensor node without an analog to digital converter (ADC). If a capacitor is charged using a current transformer (CT) and a rectifying circuit, the charging time depends on the current flowing through a power line. In the case that the node transmits data every time when voltage of the capacitor exceeds a threshold voltage, we can indirectly measure the current by measuring the transmission intervals. In this method, the circuit of the node can be simplified and power consumption for the wireless transmission can be decreased because the measured current data does not need to be included in the transmitted packet. However, the measurable range is about single digit because the transmission interval decreases suddenly as the current increases. In this work, we have ex- panded the range using one CT, one wireless transmission module, and two charging circuits that include different load resistors connected in series. The results indicated that the measurable range was from 0.5 A to 50 A.
