High-voltage direct current(HVDC)grids require fast and reliable protection of the DC lines.The performance of traditional protection schemes is easily impaired by the limitations of the boundary condition and nonline...High-voltage direct current(HVDC)grids require fast and reliable protection of the DC lines.The performance of traditional protection schemes is easily impaired by the limitations of the boundary condition and nonlinearity from the control of converters.One of the key technologies for flexible HVDC grids is the half-bridge modular multilevel converter(HB-MMC).Considering the high controllability of HB-MMC,this study proposes an active injection protection scheme to improve the reliability and sensitivity of the HVDC grid protection.The HB-MMC is used to inject a sinusoidal characteristic signal,at the specified frequency,into the DC lines.Then,the voltage and current at the specified frequency are extracted using the Prony algorithm to calculate the input impedance,which is used for the identification of internal and external faults.The active injection protection scheme was simulated for various cases in the simulation software Power Systems Computer Aided Design.The simulation results indicate that the proposed protection scheme is highly reliable and can overcome transition resistance.展开更多
Because of the realization of HVDC connections parallel to the synchronous grid in Germany, operational concepts become more important in the context of system security aspects. In this article commonly known concepts...Because of the realization of HVDC connections parallel to the synchronous grid in Germany, operational concepts become more important in the context of system security aspects. In this article commonly known concepts are analyzed regarding their suitability for the German transmission system. Therefore, an approach for the analysis was developed and exemplary results are given using this approach. Under consideration of the overall system, the concepts of reducing losses in combination with minimizing(n-1)-warnings or-indications^1 as well as the sole minimization of(n-1)-warnings and-indications are the most reasonable approaches. However, under grid security aspects best results can be achieved by reducing operational limits and therefore, by the minimization of(n-1)-warnings.展开更多
双馈/直驱风机混合接入模块化多电平高压直流输电(modular multi-level converter based HVDC,MMC-HVDC)的次同步振荡事件频繁发生,已有双馈或直驱某一种风机与MMC-HVDC交互产生振荡的研究,但鲜有针对双馈/直驱风机混合接入MMC-HVDC的...双馈/直驱风机混合接入模块化多电平高压直流输电(modular multi-level converter based HVDC,MMC-HVDC)的次同步振荡事件频繁发生,已有双馈或直驱某一种风机与MMC-HVDC交互产生振荡的研究,但鲜有针对双馈/直驱风机混合接入MMC-HVDC的次同步振荡分析与抑制措施研究。该文首先阐述并分析了某双馈/直驱风机混合接入MMC-HVDC后发生次同步振荡实际事件的特征与原因,通过阻抗相量方法研究了双馈/直驱风机频域阻抗的交互影响方式。研究表明,在双馈或直驱风机单独接入MMC-HVDC不存在振荡风险的条件下,双馈和直驱风机并联接入后依然可能存在振荡风险。最后,根据电网调度运行的实际要求,提出了考虑机组启停数量调配的临时抑制振荡策略。展开更多
For demonstrating a multiterminal voltage-source converter(VSC)-based high-voltage DC(HVDC)(VSCHVDC) project, this study puts forward a technical route for calculating the power flow in a 500-kV VSC-HVDC power grid in...For demonstrating a multiterminal voltage-source converter(VSC)-based high-voltage DC(HVDC)(VSCHVDC) project, this study puts forward a technical route for calculating the power flow in a 500-kV VSC-HVDC power grid in comparison with that of an AC power grid. The Jacobian matrix used in the power-flow calculation was deduced through methods such as Newton–Laphson iteration and Taylor series expansion. Further, the operation effect of powerflow calculation on a true bipolar VSC-HVDC power grid was analyzed briefly. The elements of the Jacobian matrix corresponding to VSC were studied under the mode of droop control and the control strategy of VSC-HVDC power grid was analyzed in detail. The power-flow calculation model for VSC-HVDC power grid of the master–slave control mode was simplified using the PQ decomposition method of the power-flow calculation of an AC power grid. Moreover, a four-terminal model of the Zhangbei VSC-HVDC demonstration project was established and tested on MATLAB. The simulation results under two kinds of operating conditions were analyzed and compared to the results of BPA; the deviation between the power-flow results was studied. The results show that the proposed calculation method can provide a feasible support for calculating the power flow in VSC-HVDC grids.展开更多
针对大规模近海风电场地理分布上高度分散以及主要采用双馈式或直驱/半直驱式风电机组的特点,提出了相应的电压源型变流器的高压直流(voltage source converter based HVDC,VSC-HVDC)并网传输拓扑结构,并设计了相应的控制策略。为验证...针对大规模近海风电场地理分布上高度分散以及主要采用双馈式或直驱/半直驱式风电机组的特点,提出了相应的电压源型变流器的高压直流(voltage source converter based HVDC,VSC-HVDC)并网传输拓扑结构,并设计了相应的控制策略。为验证所提方案的可行性,利用Matlab/Simulink构建了一个近海风电场的5端口VSC-HVDC并网传输系统,并进行了系列仿真。仿真结果表明,所提VSC-HVDC方案可为大规模近海风电场的并网传输提供优化的解决方案。展开更多
为揭示具有新型拓扑结构的基于模块化多电平换流器直流输电系统MMC-HVDC(modular multilevel converter high voltage direct current)的电磁暂态特性,对该系统进行典型扰动暂态响应的特性分析根据MMC拓扑结构,推导了交流电网不平衡时的...为揭示具有新型拓扑结构的基于模块化多电平换流器直流输电系统MMC-HVDC(modular multilevel converter high voltage direct current)的电磁暂态特性,对该系统进行典型扰动暂态响应的特性分析根据MMC拓扑结构,推导了交流电网不平衡时的MMC交流侧电磁暂态模型,并基于模型设计了正、负序双内环电流控制和外环功率控制的控制策略。同时,对MMC-HVDC在各种典型扰动下的暂态响应特性进行了详细的仿真分析,仿真结果表明所设计的控制策略的正确性。MMC-HVDC在遭受各种典型扰动时具有良好的暂态响应特性,并能稳定、充裕地运行。展开更多
模块化多电平换流器型直流输电系统(modular multilevel converter based high voltage direct current,MMCHVDC)和交流线路可为重要负荷双路供电,因此MMCHVDC需具备在联网运行状态和孤岛运行状态间稳定转换的能力。该文分析了MMC在联...模块化多电平换流器型直流输电系统(modular multilevel converter based high voltage direct current,MMCHVDC)和交流线路可为重要负荷双路供电,因此MMCHVDC需具备在联网运行状态和孤岛运行状态间稳定转换的能力。该文分析了MMC在联网状态和孤岛状态间相互转换的过程,并设计了一种基于本地电气量的MMC控制模式切换策略。之后,对MMC无源供电控制器进行改进,设计了一种无需切换控制模式的MMC下垂控制策略。最后,通过PSCAD仿真对上述2种转换策略进行验证和比较,结果表明2种策略均能使MMC在联网状态和孤岛状态间稳定转换。2种策略各有优缺点,实际应用中MMC需依据具体的控制目标选取合适的策略。展开更多
基金supported by the Fundamental Research Funds for the Central Universities(No.2020YJS169)The National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid(No.U2066210).
文摘High-voltage direct current(HVDC)grids require fast and reliable protection of the DC lines.The performance of traditional protection schemes is easily impaired by the limitations of the boundary condition and nonlinearity from the control of converters.One of the key technologies for flexible HVDC grids is the half-bridge modular multilevel converter(HB-MMC).Considering the high controllability of HB-MMC,this study proposes an active injection protection scheme to improve the reliability and sensitivity of the HVDC grid protection.The HB-MMC is used to inject a sinusoidal characteristic signal,at the specified frequency,into the DC lines.Then,the voltage and current at the specified frequency are extracted using the Prony algorithm to calculate the input impedance,which is used for the identification of internal and external faults.The active injection protection scheme was simulated for various cases in the simulation software Power Systems Computer Aided Design.The simulation results indicate that the proposed protection scheme is highly reliable and can overcome transition resistance.
文摘Because of the realization of HVDC connections parallel to the synchronous grid in Germany, operational concepts become more important in the context of system security aspects. In this article commonly known concepts are analyzed regarding their suitability for the German transmission system. Therefore, an approach for the analysis was developed and exemplary results are given using this approach. Under consideration of the overall system, the concepts of reducing losses in combination with minimizing(n-1)-warnings or-indications^1 as well as the sole minimization of(n-1)-warnings and-indications are the most reasonable approaches. However, under grid security aspects best results can be achieved by reducing operational limits and therefore, by the minimization of(n-1)-warnings.
文摘双馈/直驱风机混合接入模块化多电平高压直流输电(modular multi-level converter based HVDC,MMC-HVDC)的次同步振荡事件频繁发生,已有双馈或直驱某一种风机与MMC-HVDC交互产生振荡的研究,但鲜有针对双馈/直驱风机混合接入MMC-HVDC的次同步振荡分析与抑制措施研究。该文首先阐述并分析了某双馈/直驱风机混合接入MMC-HVDC后发生次同步振荡实际事件的特征与原因,通过阻抗相量方法研究了双馈/直驱风机频域阻抗的交互影响方式。研究表明,在双馈或直驱风机单独接入MMC-HVDC不存在振荡风险的条件下,双馈和直驱风机并联接入后依然可能存在振荡风险。最后,根据电网调度运行的实际要求,提出了考虑机组启停数量调配的临时抑制振荡策略。
基金supported by the State Grid Corporation of China Headquarter technology project (52010118000K)
文摘For demonstrating a multiterminal voltage-source converter(VSC)-based high-voltage DC(HVDC)(VSCHVDC) project, this study puts forward a technical route for calculating the power flow in a 500-kV VSC-HVDC power grid in comparison with that of an AC power grid. The Jacobian matrix used in the power-flow calculation was deduced through methods such as Newton–Laphson iteration and Taylor series expansion. Further, the operation effect of powerflow calculation on a true bipolar VSC-HVDC power grid was analyzed briefly. The elements of the Jacobian matrix corresponding to VSC were studied under the mode of droop control and the control strategy of VSC-HVDC power grid was analyzed in detail. The power-flow calculation model for VSC-HVDC power grid of the master–slave control mode was simplified using the PQ decomposition method of the power-flow calculation of an AC power grid. Moreover, a four-terminal model of the Zhangbei VSC-HVDC demonstration project was established and tested on MATLAB. The simulation results under two kinds of operating conditions were analyzed and compared to the results of BPA; the deviation between the power-flow results was studied. The results show that the proposed calculation method can provide a feasible support for calculating the power flow in VSC-HVDC grids.
文摘针对大规模近海风电场地理分布上高度分散以及主要采用双馈式或直驱/半直驱式风电机组的特点,提出了相应的电压源型变流器的高压直流(voltage source converter based HVDC,VSC-HVDC)并网传输拓扑结构,并设计了相应的控制策略。为验证所提方案的可行性,利用Matlab/Simulink构建了一个近海风电场的5端口VSC-HVDC并网传输系统,并进行了系列仿真。仿真结果表明,所提VSC-HVDC方案可为大规模近海风电场的并网传输提供优化的解决方案。
文摘为揭示具有新型拓扑结构的基于模块化多电平换流器直流输电系统MMC-HVDC(modular multilevel converter high voltage direct current)的电磁暂态特性,对该系统进行典型扰动暂态响应的特性分析根据MMC拓扑结构,推导了交流电网不平衡时的MMC交流侧电磁暂态模型,并基于模型设计了正、负序双内环电流控制和外环功率控制的控制策略。同时,对MMC-HVDC在各种典型扰动下的暂态响应特性进行了详细的仿真分析,仿真结果表明所设计的控制策略的正确性。MMC-HVDC在遭受各种典型扰动时具有良好的暂态响应特性,并能稳定、充裕地运行。
文摘模块化多电平换流器型直流输电系统(modular multilevel converter based high voltage direct current,MMCHVDC)和交流线路可为重要负荷双路供电,因此MMCHVDC需具备在联网运行状态和孤岛运行状态间稳定转换的能力。该文分析了MMC在联网状态和孤岛状态间相互转换的过程,并设计了一种基于本地电气量的MMC控制模式切换策略。之后,对MMC无源供电控制器进行改进,设计了一种无需切换控制模式的MMC下垂控制策略。最后,通过PSCAD仿真对上述2种转换策略进行验证和比较,结果表明2种策略均能使MMC在联网状态和孤岛状态间稳定转换。2种策略各有优缺点,实际应用中MMC需依据具体的控制目标选取合适的策略。
