Symmetrical monopolar configuration is the prevailing scheme configuration for modular multilevel converter based high-voltage direct current(MMC-HVDC) links, in which severe DC overvoltage or overcurrent can be cause...Symmetrical monopolar configuration is the prevailing scheme configuration for modular multilevel converter based high-voltage direct current(MMC-HVDC) links, in which severe DC overvoltage or overcurrent can be caused by the DC faults. To deal with the possible asymmetry in the DC faults and the coupling effects of the DC lines, this paper analyzes the DC fault characteristics based on the phase-mode transformation. First, the DC grid is decomposed into the common-mode and the differential-mode networks. The equivalent models of the MMCs and DC lines in the two networks are derived, respectively. Then, based on the state matrices, a unified numerical calculation method for the fault voltages and currents at the DC side is proposed. Compared with the time-domain simulations performed on PSCAD/EMTDC, the accuracy of the proposed method is validated. Last, the system parameter analysis shows that the grounding parameters play an important role in reducing the severity of the pole-to-ground faults, whereas the coupling effects of the DC lines should be considered when calculating the DC fault currents associated with the pole-to-pole faults.展开更多
This paper presents the behavior analysis of modular multilevel converter under DC pole-to-pole short-circuit fault, which is an important issue in fault management, electrical system design and MMC based power system...This paper presents the behavior analysis of modular multilevel converter under DC pole-to-pole short-circuit fault, which is an important issue in fault management, electrical system design and MMC based power system protection and control. Firstly, the transient behavior is analyzed and the conduction overlap- ping angle γ, is defined. Secondly, seven possible short-circuit current paths induced by different γ values are identified, and the corresponding engineering short-circuit current calculation methods for both AC and DC sides are proposed. And then, the influences of impedance distribution factor κ and equivalent short-circuit resistance Rsc on short-circuit currents are elaborated the proposed analysis methods. Finally, case study is used to verify the effectiveness of展开更多
In this paper, we establish a general theta function identity. It is a common origin of many theta function identities. From which many classical and new modular equations are derived. All the proofs are elementary.
直流双极短路故障是柔性直流输电(voltage source converter based high voltage direct current,VSC-HVDC)系统最严重的故障之一。具有桥臂阻尼的半桥型模块化多电平换流器在故障后能加快故障电流的衰减速度,实现系统快速重启动。基于...直流双极短路故障是柔性直流输电(voltage source converter based high voltage direct current,VSC-HVDC)系统最严重的故障之一。具有桥臂阻尼的半桥型模块化多电平换流器在故障后能加快故障电流的衰减速度,实现系统快速重启动。基于含桥臂阻尼的HBMMC(half bridge sub-module modular multilevel converter)-HVDC系统建立了一套完整的直流双极短路故障机理分析的解析模型,分别对换流器闭锁前,换流器闭锁后和交流断路器断开后3个阶段的故障机理进行了详细分析,并给出了每个阶段对应的桥臂电流解析表达式。通过此解析模型,可快速准确地计算直流双极短路故障发生后的故障电流及故障衰减时间,为其工程应用提供理论依据。最后,基于Matlab/Simulink仿真软件搭建了含桥臂阻尼的HBMMC-HVDC系统仿真模型,通过仿真验证了该解析模型的可行性与准确性。展开更多
直流变压器是解决直流输电系统互联时电压等级不一致问题的主要方法,然而直流变压器的故障特性和恢复策略尚不清楚。文中研究了模块化组合式直流变压器(modular combined DC transformer,MCT)在直流单极接地故障下的暂态特性,并分析了...直流变压器是解决直流输电系统互联时电压等级不一致问题的主要方法,然而直流变压器的故障特性和恢复策略尚不清楚。文中研究了模块化组合式直流变压器(modular combined DC transformer,MCT)在直流单极接地故障下的暂态特性,并分析了不同故障下交流侧隔直电容的放电过程,提出了相应的故障恢复策略。最后在PSCAD/EMTDC中搭建了含有MCT的柔性直流输电系统仿真模型,时域仿真结果验证了故障特性分析和故障恢复策略的正确性和有效性。展开更多
文摘Symmetrical monopolar configuration is the prevailing scheme configuration for modular multilevel converter based high-voltage direct current(MMC-HVDC) links, in which severe DC overvoltage or overcurrent can be caused by the DC faults. To deal with the possible asymmetry in the DC faults and the coupling effects of the DC lines, this paper analyzes the DC fault characteristics based on the phase-mode transformation. First, the DC grid is decomposed into the common-mode and the differential-mode networks. The equivalent models of the MMCs and DC lines in the two networks are derived, respectively. Then, based on the state matrices, a unified numerical calculation method for the fault voltages and currents at the DC side is proposed. Compared with the time-domain simulations performed on PSCAD/EMTDC, the accuracy of the proposed method is validated. Last, the system parameter analysis shows that the grounding parameters play an important role in reducing the severity of the pole-to-ground faults, whereas the coupling effects of the DC lines should be considered when calculating the DC fault currents associated with the pole-to-pole faults.
文摘This paper presents the behavior analysis of modular multilevel converter under DC pole-to-pole short-circuit fault, which is an important issue in fault management, electrical system design and MMC based power system protection and control. Firstly, the transient behavior is analyzed and the conduction overlap- ping angle γ, is defined. Secondly, seven possible short-circuit current paths induced by different γ values are identified, and the corresponding engineering short-circuit current calculation methods for both AC and DC sides are proposed. And then, the influences of impedance distribution factor κ and equivalent short-circuit resistance Rsc on short-circuit currents are elaborated the proposed analysis methods. Finally, case study is used to verify the effectiveness of
基金Supported by the National Natural Science Foundation of China（11071107, 11371184）
文摘In this paper, we establish a general theta function identity. It is a common origin of many theta function identities. From which many classical and new modular equations are derived. All the proofs are elementary.
文摘直流双极短路故障是柔性直流输电(voltage source converter based high voltage direct current,VSC-HVDC)系统最严重的故障之一。具有桥臂阻尼的半桥型模块化多电平换流器在故障后能加快故障电流的衰减速度,实现系统快速重启动。基于含桥臂阻尼的HBMMC(half bridge sub-module modular multilevel converter)-HVDC系统建立了一套完整的直流双极短路故障机理分析的解析模型,分别对换流器闭锁前,换流器闭锁后和交流断路器断开后3个阶段的故障机理进行了详细分析,并给出了每个阶段对应的桥臂电流解析表达式。通过此解析模型,可快速准确地计算直流双极短路故障发生后的故障电流及故障衰减时间,为其工程应用提供理论依据。最后,基于Matlab/Simulink仿真软件搭建了含桥臂阻尼的HBMMC-HVDC系统仿真模型,通过仿真验证了该解析模型的可行性与准确性。
文摘直流变压器是解决直流输电系统互联时电压等级不一致问题的主要方法,然而直流变压器的故障特性和恢复策略尚不清楚。文中研究了模块化组合式直流变压器(modular combined DC transformer,MCT)在直流单极接地故障下的暂态特性,并分析了不同故障下交流侧隔直电容的放电过程,提出了相应的故障恢复策略。最后在PSCAD/EMTDC中搭建了含有MCT的柔性直流输电系统仿真模型,时域仿真结果验证了故障特性分析和故障恢复策略的正确性和有效性。
