相比传统高压直流输电HVDC(high voltage direct arrent),基于电压源换流器的高压直流输电VSC-HVDC(voltage source converter based HVDC)具有较多独特优势,是智能电网发展具有代表性的关键技术之一。首先,基于VSC-HVDC稳态模型的标幺...相比传统高压直流输电HVDC(high voltage direct arrent),基于电压源换流器的高压直流输电VSC-HVDC(voltage source converter based HVDC)具有较多独特优势,是智能电网发展具有代表性的关键技术之一。首先,基于VSC-HVDC稳态模型的标幺制处理分析了VSC-HVDC的稳态方程,并给出了适用于求解含VSC-HVDC的交直流系统潮流的统一法迭代形式;进而,通过计算预估值和校正值2个步骤,利用具有2.414阶次收敛速率的改进牛顿-拉夫逊法修正交直流系统的雅可比矩阵,以节省程序迭代过程中的数据存储空间,加快程序执行调用的速度,从而提高雅可比矩阵的计算速率。最后,基于修改后的IEEE标准算例,从交直流潮流结果、控制方式、算法效率等方面的对比分析,验证了该方法求解含VSC-HVDC的交直流系统潮流的有效性和正确性。展开更多
为解决基于模块化多电平换流器(modular multilevel converter,MMC)的柔性直流输电(high voltage direct current,HVDC)故障电流解析计算精度不足的问题,提出一种计及远端站影响的多端MMC-HVDC故障电流改进时域求解法。首先,在分析故障...为解决基于模块化多电平换流器(modular multilevel converter,MMC)的柔性直流输电(high voltage direct current,HVDC)故障电流解析计算精度不足的问题,提出一种计及远端站影响的多端MMC-HVDC故障电流改进时域求解法。首先,在分析故障后子模块电容放电路径的基础上,推导换流站等效电容值等系统参数,建立MMC-HVDC系统故障后网络等效模型。其次,将直流电网各换流站解耦,以故障后各支路电流近似解为初值,逐次修正计及远端站影响的多端MMC-HVDC线路等效电阻及等效电感,得到多端MMC-HVDC系统中各支路的故障电流值。最后,基于RT-LAB仿真平台搭建四端柔性直流电网模型,对故障电流计算值与详细电磁暂态仿真结果进行对比。结果表明,所提故障电流求解方法能够准确、有效地计算出多端MMC-HVDC短路故障后各支路电流值,最大误差小于5%。展开更多
In this paper,the calculation method and transient characteristics of asymmetric faults in the DC side of a true bipolar system are studied.First,two typical MMC fault equivalent methods are analyzed,and comparison sh...In this paper,the calculation method and transient characteristics of asymmetric faults in the DC side of a true bipolar system are studied.First,two typical MMC fault equivalent methods are analyzed,and comparison shows that active RLC equivalent branches are more suitable for fault analyses of a true bipolar system.Second,considering the influence of mutual impedance between the poles in DC side,a DC fault current calculation method for a true bipolar systems is proposed.Finally,the characteristics of transient electrical quantities including fault current and DC voltage in the process of DC faults in true bipolar systems are analyzed and summarized to provide references for the design of DC line insulation and relay protection schemes.展开更多
Controllability of DC current/power flow is essentialin multi-terminal HVDC (MTDC) grids, particularly for theMTDC grids in a meshed topology. In this paper, consideringmeshed MTDC (M2TDC) grids with the installation ...Controllability of DC current/power flow is essentialin multi-terminal HVDC (MTDC) grids, particularly for theMTDC grids in a meshed topology. In this paper, consideringmeshed MTDC (M2TDC) grids with the installation of twoline/multi-lineDC current flow controllers (CFCs), a small-signalmodel of the DC CFCs integrated M2TDC grids is derived,studying the impact of the power losses of the DC CFC andtheir influence on the analysis of energy exchanges. The systemstability analysis is analysed using the Nyquist diagram, which ismore suitable for analyzing complex nonlinear systems with morecompact and reliable indicators of stability in comparison withgain/phase margins shown in the Bode diagram. In addition, aselection method of the interconnected capacitor of the DC CFCis proposed under different operating conditions. The impact ofthe switching frequencies of the DC CFC on the control ranges ofthe DC current flows is analyzed. The effectiveness of the Nyquistanalysis and the capacitance selection method is verified bysimulation studies using PSCAD/EMTDC. The obtained control ranges of the DC CFC with different switching frequenciesand capacitances would be useful for practical engineeringapplications.展开更多
南澳岛±160 k V多端柔性直流输电工程在我国首次采用了高电压、大长度的挤包绝缘直流电缆系统,而目前在国内尚无此电压等级直流电缆工程的运行及维护经验,因此亟需对交联聚乙烯(XLPE)直流电缆的载流特性展开研究,从而为直流电缆线...南澳岛±160 k V多端柔性直流输电工程在我国首次采用了高电压、大长度的挤包绝缘直流电缆系统,而目前在国内尚无此电压等级直流电缆工程的运行及维护经验,因此亟需对交联聚乙烯(XLPE)直流电缆的载流特性展开研究,从而为直流电缆线路运行限值的控制以及在线监测系统的定制提供技术支持。通过研究不同敷设环境下直流电缆的散热原理,采用专业有限元软件COMSOL Multiphysics建立了带保护套管埋地敷设方式下±160 k V直流XLPE海底电缆的温度场模型,用以模拟其温度分布和计算其载流量;通过在试验场地开展静态载流试验,对仿真模型的可靠性进行了验证;对试验结果进行讨论,分析得出了直流海缆的载流特性。展开更多
给出了一种不发散的大规模交直流系统潮流计算的实用化模型。通过在交直流潮流方程组引入一组松弛量,将常规的潮流计算转换为松弛量平方和最小的非线性规划模型。在该模型中引入不等式约束以反映运行约束及直流控制方式。采用内点法求...给出了一种不发散的大规模交直流系统潮流计算的实用化模型。通过在交直流潮流方程组引入一组松弛量,将常规的潮流计算转换为松弛量平方和最小的非线性规划模型。在该模型中引入不等式约束以反映运行约束及直流控制方式。采用内点法求解该模型,减少修正方程的维数,使之与牛顿–拉夫逊潮流计算修正方程具有完全相同的维数,而且修正方程的系数矩阵具有对称正定特性。采用近似最小度(approximate minimum degree,AMD)算法与改进平方根分解法来求解修正方程以提高程序计算速度。该模型具有如下特点:无需特殊的初值计算环节;能够适应具有大量小阻抗与负阻抗支路的系统;在潮流有解、潮流无解、可行域边界附近具有良好的、一致的收敛性。在6891节点含8回高压直流输电(high voltage direct current,HVDC)线路的测试系统的潮流计算中验证了所提算法的有效性和高效性。展开更多
文摘相比传统高压直流输电HVDC(high voltage direct arrent),基于电压源换流器的高压直流输电VSC-HVDC(voltage source converter based HVDC)具有较多独特优势,是智能电网发展具有代表性的关键技术之一。首先,基于VSC-HVDC稳态模型的标幺制处理分析了VSC-HVDC的稳态方程,并给出了适用于求解含VSC-HVDC的交直流系统潮流的统一法迭代形式;进而,通过计算预估值和校正值2个步骤,利用具有2.414阶次收敛速率的改进牛顿-拉夫逊法修正交直流系统的雅可比矩阵,以节省程序迭代过程中的数据存储空间,加快程序执行调用的速度,从而提高雅可比矩阵的计算速率。最后,基于修改后的IEEE标准算例,从交直流潮流结果、控制方式、算法效率等方面的对比分析,验证了该方法求解含VSC-HVDC的交直流系统潮流的有效性和正确性。
文摘为解决基于模块化多电平换流器(modular multilevel converter,MMC)的柔性直流输电(high voltage direct current,HVDC)故障电流解析计算精度不足的问题,提出一种计及远端站影响的多端MMC-HVDC故障电流改进时域求解法。首先,在分析故障后子模块电容放电路径的基础上,推导换流站等效电容值等系统参数,建立MMC-HVDC系统故障后网络等效模型。其次,将直流电网各换流站解耦,以故障后各支路电流近似解为初值,逐次修正计及远端站影响的多端MMC-HVDC线路等效电阻及等效电感,得到多端MMC-HVDC系统中各支路的故障电流值。最后,基于RT-LAB仿真平台搭建四端柔性直流电网模型,对故障电流计算值与详细电磁暂态仿真结果进行对比。结果表明,所提故障电流求解方法能够准确、有效地计算出多端MMC-HVDC短路故障后各支路电流值,最大误差小于5%。
基金supported in part by the National Key R&D Program of China under Grant 2018YFB0904600in part by the National Nature Science Foundation of China(NSFC)under Grant 51677125in part by Joint Funds of the National Natural Science Foundation of China under Grant U1866205.
文摘In this paper,the calculation method and transient characteristics of asymmetric faults in the DC side of a true bipolar system are studied.First,two typical MMC fault equivalent methods are analyzed,and comparison shows that active RLC equivalent branches are more suitable for fault analyses of a true bipolar system.Second,considering the influence of mutual impedance between the poles in DC side,a DC fault current calculation method for a true bipolar systems is proposed.Finally,the characteristics of transient electrical quantities including fault current and DC voltage in the process of DC faults in true bipolar systems are analyzed and summarized to provide references for the design of DC line insulation and relay protection schemes.
基金National Natural Science Foundation of China under Grant 51807091Natural Science Foundation of Jiangsu Province BK20180478+1 种基金the China Postdoctoral Science Foundation under Grant 2019M661846EPSRC under Grant EP/N032888/1.
文摘Controllability of DC current/power flow is essentialin multi-terminal HVDC (MTDC) grids, particularly for theMTDC grids in a meshed topology. In this paper, consideringmeshed MTDC (M2TDC) grids with the installation of twoline/multi-lineDC current flow controllers (CFCs), a small-signalmodel of the DC CFCs integrated M2TDC grids is derived,studying the impact of the power losses of the DC CFC andtheir influence on the analysis of energy exchanges. The systemstability analysis is analysed using the Nyquist diagram, which ismore suitable for analyzing complex nonlinear systems with morecompact and reliable indicators of stability in comparison withgain/phase margins shown in the Bode diagram. In addition, aselection method of the interconnected capacitor of the DC CFCis proposed under different operating conditions. The impact ofthe switching frequencies of the DC CFC on the control ranges ofthe DC current flows is analyzed. The effectiveness of the Nyquistanalysis and the capacitance selection method is verified bysimulation studies using PSCAD/EMTDC. The obtained control ranges of the DC CFC with different switching frequenciesand capacitances would be useful for practical engineeringapplications.
文摘南澳岛±160 k V多端柔性直流输电工程在我国首次采用了高电压、大长度的挤包绝缘直流电缆系统,而目前在国内尚无此电压等级直流电缆工程的运行及维护经验,因此亟需对交联聚乙烯(XLPE)直流电缆的载流特性展开研究,从而为直流电缆线路运行限值的控制以及在线监测系统的定制提供技术支持。通过研究不同敷设环境下直流电缆的散热原理,采用专业有限元软件COMSOL Multiphysics建立了带保护套管埋地敷设方式下±160 k V直流XLPE海底电缆的温度场模型,用以模拟其温度分布和计算其载流量;通过在试验场地开展静态载流试验,对仿真模型的可靠性进行了验证;对试验结果进行讨论,分析得出了直流海缆的载流特性。
文摘给出了一种不发散的大规模交直流系统潮流计算的实用化模型。通过在交直流潮流方程组引入一组松弛量,将常规的潮流计算转换为松弛量平方和最小的非线性规划模型。在该模型中引入不等式约束以反映运行约束及直流控制方式。采用内点法求解该模型,减少修正方程的维数,使之与牛顿–拉夫逊潮流计算修正方程具有完全相同的维数,而且修正方程的系数矩阵具有对称正定特性。采用近似最小度(approximate minimum degree,AMD)算法与改进平方根分解法来求解修正方程以提高程序计算速度。该模型具有如下特点:无需特殊的初值计算环节;能够适应具有大量小阻抗与负阻抗支路的系统;在潮流有解、潮流无解、可行域边界附近具有良好的、一致的收敛性。在6891节点含8回高压直流输电(high voltage direct current,HVDC)线路的测试系统的潮流计算中验证了所提算法的有效性和高效性。
