The close proximity and the necessity of coordination between multiple high-voltage direct currents(HVDCs)raise the issue of grid partitioning in multi-infeed HVDC systems.A multi-objective partition strategy is propo...The close proximity and the necessity of coordination between multiple high-voltage direct currents(HVDCs)raise the issue of grid partitioning in multi-infeed HVDC systems.A multi-objective partition strategy is proposed in this paper.Several types of relationships to be coordinated and complemented are analyzed and formulated using quantitative indices.According to the graph theory,the HVDC partition is transformed into a graph-cut problem and solved via the spectral clustering algorithm.Finally,the proposed method is validated for a practical multi-HVDC grid,confirming its feasibility and effectiveness.展开更多
In multi-infeed HVDC system, the interactions and influences between DC systems AC systems are complex as the electrical distances among DC converter stations which are relatively short. Multi-infeed interaction facto...In multi-infeed HVDC system, the interactions and influences between DC systems AC systems are complex as the electrical distances among DC converter stations which are relatively short. Multi-infeed interaction factor (MIIF) can effectively reflect the interaction among DC systems. The paper theoretically analyzes the impact factors of MIIF like the electrical distances between two DC converter stations and the equivalent impedance of the receiving end AC system. By applying the Kirchhoff’s current law on the inverter AC bus, the paper deduces the analytical expressions for MIIF. From the expression, it is clear how the equivalent impedance of AC system and coupling impedance can affect MIIF. PSCAD simulations validate the effectiveness and the correctness of the proposed expression and some useful conclusions are drawn.展开更多
More and more high voltage direct current(HVDC) converters are being located in a load area in the Yangtze River Delta Region in China. It's large transmission capacity and intensive placement are hardly seen in o...More and more high voltage direct current(HVDC) converters are being located in a load area in the Yangtze River Delta Region in China. It's large transmission capacity and intensive placement are hardly seen in other countries. Accurate and reliable study tools and methods are extremely needed for power system engineers and researchers to deal with such problems which were never met before and otherwhere. A novel approach on electromagnetic modeling of alternating current / direct current(AC/DC) system is proposed and simulation is carried out to replay a real AC 3-phase to ground fault on a multi-infeed high voltage direct current(MIHVDC) system. AC system is specially simplified. Dynamic models and real parameters are adopted in main AC/DC equipments concerned and retained. Modeling and simulation are based on the power system computer aided design/electro-magnetic transient in direct current(PSCAD/EMTDC) system software package.Comparisons between simulation results and the records from the fault recorders are studied including both AC and DC quantities.展开更多
When multiple LCC-HVDC transmission lines are densely fed into a receiving AC system,voltage dips can easily propagate in the power system,resulting in multiple LCC commutation failures simultaneously.The VSC-HVDC can...When multiple LCC-HVDC transmission lines are densely fed into a receiving AC system,voltage dips can easily propagate in the power system,resulting in multiple LCC commutation failures simultaneously.The VSC-HVDC can be used to divide the receiving sys-tem into several interconnected sub-partitions and improve the voltage support capability of the receiving system.Compared with asyn-chronous interconnection,which completely separates the receiving systems with VSC-HVDC,incomplete segmentation with an AC connection is a more pertinent segmenting method for multilayer complex regional power grids.To analyze the voltage support capability of the VSC in incomplete segmentation,a micro-incremental model of the VSC was established,the operating impedance of the VSC was calculated,and the voltage support function of the VSC was quantified.The effect of the fault on the system short-circuit capacity was analyzed,and a calculation method for the multi-infeed short-circuit ratio in an incompletely segmented scenario was obtained.A VSC-segmented model of a two-infeed DC system was built on the EMTDC/PSCAD simulation platform,and the validity of the micro-increment model and accuracy of the proposed conclusions were verified.展开更多
During the power modulation process of line com-mutated converter-based high-voltage direct current(LCC-HVDC),the transient power mismatch between the fast-change converter station and the slow-response reactive power...During the power modulation process of line com-mutated converter-based high-voltage direct current(LCC-HVDC),the transient power mismatch between the fast-change converter station and the slow-response reactive power compen-sators(RPCs)can cause transient voltage disturbances at the weak sending end of the AC grid.To mitigate such voltage dis-turbances,this paper proposes a coordinated feedback power control method for the hybrid multi-infeed HVDC(HMI-HVDC)system comprising an LCC-HVDC and voltage source converter-based HVDC(VSC-HVDC)systems.The mechanism of the disturbance caused by transient power mismatch is quan-titatively analyzed,and the numerical relationship between the instantaneous unbalanced power and the AC voltage is derived.Based on the numerical relationship and considering the time-varying relationship of reactive power between converter sta-tions,the unbalanced power is set as the feedback and coordi-nately distributed among the inverter stations of VSC-HVDC,and the rectifier and the inverter stations of LCC-HVDC.Simu-lation results verify that the proposed method can effectively suppress voltage disturbance without relying on remote commu-nication,thus enhancing the operation performance of the HMI-HVDC system.展开更多
“双碳”目标驱动新能源快速发展,大规模风电经由传统高压直流输电(Line-Commutated Converter Based HVDC,LCC-HVDC)并网外送是风电开发利用的主要方式,直驱风机与LCC-HVDC之间的交互作用不当是导致次同步振荡的主要原因,但其振荡机理...“双碳”目标驱动新能源快速发展,大规模风电经由传统高压直流输电(Line-Commutated Converter Based HVDC,LCC-HVDC)并网外送是风电开发利用的主要方式,直驱风机与LCC-HVDC之间的交互作用不当是导致次同步振荡的主要原因,但其振荡机理和影响因素不明确。文中面向直驱风电场经LCC-HVDC外送系统的次同步振荡问题,通过扰动测辨法构建直驱风电场、直流输电系统和公共并网点(Point of Common Coupling,PCC)端口阻抗模型。基于阻抗分析法提出一种适用于交直流系统的稳定性判据,分析影响系统稳定域的主导因素和各设备对系统阻抗特性的影响,揭示控制参数对系统阻抗特性的影响规律,结果表明随着直驱风机网侧变流器、LCC-HVDC整流侧控制器比例系数减小和积分系数增大,LCC-HVDC、风电场端口阻抗均易呈现负电阻特性,直驱风电场和LCC-HVDC构成的并联阻抗呈现负阻尼特性,系统存在次同步振荡风险。最后,基于PSCAD/EMTDC平台进行时域仿真,进一步验证各控制参数对系统稳定性的影响。展开更多
“沙戈荒”风电经高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)送至负荷中心消纳场景中,风机采用虚拟同步机控制(virtual synchronous generator control,VSG)可自行构建输出电压和频率,为LCC-...“沙戈荒”风电经高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)送至负荷中心消纳场景中,风机采用虚拟同步机控制(virtual synchronous generator control,VSG)可自行构建输出电压和频率,为LCC-HVDC提供换相电压。采用虚拟同步机控制的直驱风电场(virtual synchronous generator direct-drive wind farm,VSG-DDWF)接入LCC-HVDC送端换流站近区时,系统次同步振荡(sub-synchronous oscillation,SSO)特性及机理尚未有定论。首先,文章采用模块化小信号建模方法建立了VSG-DDWF接入LCC-HVDC送端近区系统状态空间模型;其次,基于特征值分析法分析了系统SSO特性;然后,通过阻尼路径法揭示VSG-DDWF与LCC-HVDC系统SSO交互作用机理,并分析了风机机侧动态对系统阻尼的影响;最后,分析了风机台数、短路比(Short Circuit Ratio,SCR)、控制器参数对系统阻尼的影响。结果显示,VSG-DDWF同步控制环节主导的SSO模态具有失稳风险,VSG-DDWF与LCC-HVDC间存在SSO交互作用,加剧了系统发生的SSO风险;风机机侧动态会引入负阻尼,并使振荡频率发生偏移;风机网侧外环控制器比例系数减小,短路比增大时,系统SSO模态阻尼减小;VSG-DDWF中风机台数增多,系统SSO模态阻尼先增加后减小。展开更多
针对模块化多电平换流器型高压直流输电(modular multilevel converter-high voltage direct current,MMC-HVDC)系统,提出了一种创新的换流器桥臂保护方法。首先,分析了在换流器单桥臂接地以及单相桥臂间接地情况下电流的流通路径,构建...针对模块化多电平换流器型高压直流输电(modular multilevel converter-high voltage direct current,MMC-HVDC)系统,提出了一种创新的换流器桥臂保护方法。首先,分析了在换流器单桥臂接地以及单相桥臂间接地情况下电流的流通路径,构建了等值电路,并推导了换流器闭锁前后桥臂电流的表达式。基于此,剖析了故障后三相桥臂电流之和的独有特征,提出了通过检测三相桥臂和电流的基频分量是否为零来区分桥臂内部故障与外部故障的保护策略。鉴于现有桥臂保护方法无法有效应对换流器单相桥臂间短路的问题,进一步研究了此类短路情况下的特性,发现故障相上、下桥臂电流仅包含基频分量而不含直流分量,从而制定了相应的动作判据。将三相桥臂和电流保护与单相桥臂间短路保护判据进行,能够全面识别换流器桥臂上发生的各种故障,丰富和完善了换流器桥臂的保护原理。最终,通过在MATLAB/SimulinK中搭建双极MMC-HVDC系统仿真模型验证了所提出保护方法的有效性和可靠性。展开更多
This paper provides a comprehensive analysis of local and concurrent commutation failure(CF)of multi-infeed high-voltage direct current(HVDC)system considering multi-infeed interaction factor(MIIF).The literature indi...This paper provides a comprehensive analysis of local and concurrent commutation failure(CF)of multi-infeed high-voltage direct current(HVDC)system considering multi-infeed interaction factor(MIIF).The literature indicates that the local CF is not influenced by MIIF,whereas this paper concludes that both the local CF and concurrent CF are influenced by MIIF.The ability of remote converter to work under reduced reactive power enables its feature to support local converter via inter-connection link.The MIIF measures the strength of electrical connectivity between converters.Higher MIIF gives a clearer path to remote converter to support local converter,but at the same time,it provides an easy path to local converter to disturb remote converter under local fault.The presence of nearby converter increases the local commutation failure immunity index(CFII)while reducing concurrent CFII.Higher MIIF causes reactive power support to flow from remote converter to local converter,which reduces the chances of CF.A mathematical approximation to calculate the increase in local CFII for multi-infeed HVDC configurations is also proposed.A power flow approach is used to model the relation between MIIF and reactive power support from remote end.The local and concurrent CFIIs are found to be inverse to each other over MIIF;therefore,it is recommended that there is an optimal value of MIIF for all converters in close electric proximity to maintain CFII at a certain level.The numerical results of established model are compared with PSCAD/EMTDC simulations.The simulation results show the details of the influence of MIIF on local CF and concurrent CF of multi-infeed HVDC,which validates the analysis presented.展开更多
High-voltage direct current(HVDC)transmission is playing an increasingly important role in modern power systems,and the resulted power/voltage stability issue has raised widespread concern.This paper presents an on-li...High-voltage direct current(HVDC)transmission is playing an increasingly important role in modern power systems,and the resulted power/voltage stability issue has raised widespread concern.This paper presents an on-line power/voltage stability index(PVSI)for multi-infeed HVDC(MIDC)systems.Different from the existing indices which are developed mainly for off-line and static analysis,the proposed PVSI can be applied in real time.Effects of system changes on stability assessment such as change of system states and control strategies are considered.Thus,helpful guidance can be provided for on-line HVDC stability and controls.The PVSI is originally deduced for single-infeed HVDC systems in an‘‘AC way’’by analyzing the power and voltage stability of both pure AC systems and HVDC systems.Moreover,its on-line application in practical MIDC systems is realized by building an equivalent single-infeed model,and utilizing nowadays measurement and communication infrastructures such as wide-area measurement system(WAMS).The effectiveness of the PVSI is verified through simulations in real-time digital simulator(RTDS).展开更多
Voltage source converter based high voltage direct current(VSC-HVDC)can participate in voltage regulation by flexible control to help maintain the voltage stability of the power grid.In order to quantitatively evaluat...Voltage source converter based high voltage direct current(VSC-HVDC)can participate in voltage regulation by flexible control to help maintain the voltage stability of the power grid.In order to quantitatively evaluate its influence on the voltage interaction between VSC-HVDC and line commutated converter based high voltage direct current(LCC-HVDC),this paper proposes a hybrid multi-infeed interaction factor(HMIIF)calculation method considering the voltage regulation control characteristics of VSC-HVDC.Firstly,for a hybrid multi-infeed high voltage direct current system,an additional equivalent operating admittance matrix is constructed to characterize HVDC equipment characteristics under small disturbance.Secondly,based on the characteristic curve between the reactive power and the voltage of a certain VSC-HVDC project,the additional equivalent operating admittance of VSC-HVDC is derived.The additional equivalent operating admittance matrix calculation method is proposed.Thirdly,the equivalent bus impedance matrix is obtained by modifying the alternating current(AC)system admittance matrix with the additional equivalent operating admittance matrix.On this basis,the HMIIF calculation method based on the equivalent bus impedance ratio is proposed.Finally,the effectiveness of the proposed method is verified in a hybrid dual-infeed high voltage direct current system constructed in Power Systems Computer Aided Design(PSCAD),and the influence of voltage regulation control on HMIIF is analyzed.展开更多
基金supported by the Science and Technology Project of State Grid Corporation of China:“Control Strategy Optimization Technology for Large-Scale Photovoltaic Power Generation on the Sending-end and Receiving-end of DC Power System”(4000-201934198A-0-0-00)
文摘The close proximity and the necessity of coordination between multiple high-voltage direct currents(HVDCs)raise the issue of grid partitioning in multi-infeed HVDC systems.A multi-objective partition strategy is proposed in this paper.Several types of relationships to be coordinated and complemented are analyzed and formulated using quantitative indices.According to the graph theory,the HVDC partition is transformed into a graph-cut problem and solved via the spectral clustering algorithm.Finally,the proposed method is validated for a practical multi-HVDC grid,confirming its feasibility and effectiveness.
文摘In multi-infeed HVDC system, the interactions and influences between DC systems AC systems are complex as the electrical distances among DC converter stations which are relatively short. Multi-infeed interaction factor (MIIF) can effectively reflect the interaction among DC systems. The paper theoretically analyzes the impact factors of MIIF like the electrical distances between two DC converter stations and the equivalent impedance of the receiving end AC system. By applying the Kirchhoff’s current law on the inverter AC bus, the paper deduces the analytical expressions for MIIF. From the expression, it is clear how the equivalent impedance of AC system and coupling impedance can affect MIIF. PSCAD simulations validate the effectiveness and the correctness of the proposed expression and some useful conclusions are drawn.
文摘More and more high voltage direct current(HVDC) converters are being located in a load area in the Yangtze River Delta Region in China. It's large transmission capacity and intensive placement are hardly seen in other countries. Accurate and reliable study tools and methods are extremely needed for power system engineers and researchers to deal with such problems which were never met before and otherwhere. A novel approach on electromagnetic modeling of alternating current / direct current(AC/DC) system is proposed and simulation is carried out to replay a real AC 3-phase to ground fault on a multi-infeed high voltage direct current(MIHVDC) system. AC system is specially simplified. Dynamic models and real parameters are adopted in main AC/DC equipments concerned and retained. Modeling and simulation are based on the power system computer aided design/electro-magnetic transient in direct current(PSCAD/EMTDC) system software package.Comparisons between simulation results and the records from the fault recorders are studied including both AC and DC quantities.
基金supported by the State Grid Science and Technology Project 5108-202218280A-2-87-XG.
文摘When multiple LCC-HVDC transmission lines are densely fed into a receiving AC system,voltage dips can easily propagate in the power system,resulting in multiple LCC commutation failures simultaneously.The VSC-HVDC can be used to divide the receiving sys-tem into several interconnected sub-partitions and improve the voltage support capability of the receiving system.Compared with asyn-chronous interconnection,which completely separates the receiving systems with VSC-HVDC,incomplete segmentation with an AC connection is a more pertinent segmenting method for multilayer complex regional power grids.To analyze the voltage support capability of the VSC in incomplete segmentation,a micro-incremental model of the VSC was established,the operating impedance of the VSC was calculated,and the voltage support function of the VSC was quantified.The effect of the fault on the system short-circuit capacity was analyzed,and a calculation method for the multi-infeed short-circuit ratio in an incompletely segmented scenario was obtained.A VSC-segmented model of a two-infeed DC system was built on the EMTDC/PSCAD simulation platform,and the validity of the micro-increment model and accuracy of the proposed conclusions were verified.
基金This work was supported in part by the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(No.LAPS23020).
文摘During the power modulation process of line com-mutated converter-based high-voltage direct current(LCC-HVDC),the transient power mismatch between the fast-change converter station and the slow-response reactive power compen-sators(RPCs)can cause transient voltage disturbances at the weak sending end of the AC grid.To mitigate such voltage dis-turbances,this paper proposes a coordinated feedback power control method for the hybrid multi-infeed HVDC(HMI-HVDC)system comprising an LCC-HVDC and voltage source converter-based HVDC(VSC-HVDC)systems.The mechanism of the disturbance caused by transient power mismatch is quan-titatively analyzed,and the numerical relationship between the instantaneous unbalanced power and the AC voltage is derived.Based on the numerical relationship and considering the time-varying relationship of reactive power between converter sta-tions,the unbalanced power is set as the feedback and coordi-nately distributed among the inverter stations of VSC-HVDC,and the rectifier and the inverter stations of LCC-HVDC.Simu-lation results verify that the proposed method can effectively suppress voltage disturbance without relying on remote commu-nication,thus enhancing the operation performance of the HMI-HVDC system.
文摘“双碳”目标驱动新能源快速发展,大规模风电经由传统高压直流输电(Line-Commutated Converter Based HVDC,LCC-HVDC)并网外送是风电开发利用的主要方式,直驱风机与LCC-HVDC之间的交互作用不当是导致次同步振荡的主要原因,但其振荡机理和影响因素不明确。文中面向直驱风电场经LCC-HVDC外送系统的次同步振荡问题,通过扰动测辨法构建直驱风电场、直流输电系统和公共并网点(Point of Common Coupling,PCC)端口阻抗模型。基于阻抗分析法提出一种适用于交直流系统的稳定性判据,分析影响系统稳定域的主导因素和各设备对系统阻抗特性的影响,揭示控制参数对系统阻抗特性的影响规律,结果表明随着直驱风机网侧变流器、LCC-HVDC整流侧控制器比例系数减小和积分系数增大,LCC-HVDC、风电场端口阻抗均易呈现负电阻特性,直驱风电场和LCC-HVDC构成的并联阻抗呈现负阻尼特性,系统存在次同步振荡风险。最后,基于PSCAD/EMTDC平台进行时域仿真,进一步验证各控制参数对系统稳定性的影响。
文摘“沙戈荒”风电经高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)送至负荷中心消纳场景中,风机采用虚拟同步机控制(virtual synchronous generator control,VSG)可自行构建输出电压和频率,为LCC-HVDC提供换相电压。采用虚拟同步机控制的直驱风电场(virtual synchronous generator direct-drive wind farm,VSG-DDWF)接入LCC-HVDC送端换流站近区时,系统次同步振荡(sub-synchronous oscillation,SSO)特性及机理尚未有定论。首先,文章采用模块化小信号建模方法建立了VSG-DDWF接入LCC-HVDC送端近区系统状态空间模型;其次,基于特征值分析法分析了系统SSO特性;然后,通过阻尼路径法揭示VSG-DDWF与LCC-HVDC系统SSO交互作用机理,并分析了风机机侧动态对系统阻尼的影响;最后,分析了风机台数、短路比(Short Circuit Ratio,SCR)、控制器参数对系统阻尼的影响。结果显示,VSG-DDWF同步控制环节主导的SSO模态具有失稳风险,VSG-DDWF与LCC-HVDC间存在SSO交互作用,加剧了系统发生的SSO风险;风机机侧动态会引入负阻尼,并使振荡频率发生偏移;风机网侧外环控制器比例系数减小,短路比增大时,系统SSO模态阻尼减小;VSG-DDWF中风机台数增多,系统SSO模态阻尼先增加后减小。
文摘针对模块化多电平换流器型高压直流输电(modular multilevel converter-high voltage direct current,MMC-HVDC)系统,提出了一种创新的换流器桥臂保护方法。首先,分析了在换流器单桥臂接地以及单相桥臂间接地情况下电流的流通路径,构建了等值电路,并推导了换流器闭锁前后桥臂电流的表达式。基于此,剖析了故障后三相桥臂电流之和的独有特征,提出了通过检测三相桥臂和电流的基频分量是否为零来区分桥臂内部故障与外部故障的保护策略。鉴于现有桥臂保护方法无法有效应对换流器单相桥臂间短路的问题,进一步研究了此类短路情况下的特性,发现故障相上、下桥臂电流仅包含基频分量而不含直流分量,从而制定了相应的动作判据。将三相桥臂和电流保护与单相桥臂间短路保护判据进行,能够全面识别换流器桥臂上发生的各种故障,丰富和完善了换流器桥臂的保护原理。最终,通过在MATLAB/SimulinK中搭建双极MMC-HVDC系统仿真模型验证了所提出保护方法的有效性和可靠性。
基金This work was supported by science and technology project of China Southern Power Grid(No.ZBKJXM20180104).
文摘This paper provides a comprehensive analysis of local and concurrent commutation failure(CF)of multi-infeed high-voltage direct current(HVDC)system considering multi-infeed interaction factor(MIIF).The literature indicates that the local CF is not influenced by MIIF,whereas this paper concludes that both the local CF and concurrent CF are influenced by MIIF.The ability of remote converter to work under reduced reactive power enables its feature to support local converter via inter-connection link.The MIIF measures the strength of electrical connectivity between converters.Higher MIIF gives a clearer path to remote converter to support local converter,but at the same time,it provides an easy path to local converter to disturb remote converter under local fault.The presence of nearby converter increases the local commutation failure immunity index(CFII)while reducing concurrent CFII.Higher MIIF causes reactive power support to flow from remote converter to local converter,which reduces the chances of CF.A mathematical approximation to calculate the increase in local CFII for multi-infeed HVDC configurations is also proposed.A power flow approach is used to model the relation between MIIF and reactive power support from remote end.The local and concurrent CFIIs are found to be inverse to each other over MIIF;therefore,it is recommended that there is an optimal value of MIIF for all converters in close electric proximity to maintain CFII at a certain level.The numerical results of established model are compared with PSCAD/EMTDC simulations.The simulation results show the details of the influence of MIIF on local CF and concurrent CF of multi-infeed HVDC,which validates the analysis presented.
基金supported in part by the National Key Research and Development Program of China(No.2016YFB0900100)part by the National Natural Science Foundation of China(No.51577136)part by the Natural Science Foundation of Hubei Province,China(No.2018CFA080).
文摘High-voltage direct current(HVDC)transmission is playing an increasingly important role in modern power systems,and the resulted power/voltage stability issue has raised widespread concern.This paper presents an on-line power/voltage stability index(PVSI)for multi-infeed HVDC(MIDC)systems.Different from the existing indices which are developed mainly for off-line and static analysis,the proposed PVSI can be applied in real time.Effects of system changes on stability assessment such as change of system states and control strategies are considered.Thus,helpful guidance can be provided for on-line HVDC stability and controls.The PVSI is originally deduced for single-infeed HVDC systems in an‘‘AC way’’by analyzing the power and voltage stability of both pure AC systems and HVDC systems.Moreover,its on-line application in practical MIDC systems is realized by building an equivalent single-infeed model,and utilizing nowadays measurement and communication infrastructures such as wide-area measurement system(WAMS).The effectiveness of the PVSI is verified through simulations in real-time digital simulator(RTDS).
基金supported by the Technology Project of the State Grid Corporation Headquarters Management(Contract No.5100-202158467A-0-0-00).
文摘Voltage source converter based high voltage direct current(VSC-HVDC)can participate in voltage regulation by flexible control to help maintain the voltage stability of the power grid.In order to quantitatively evaluate its influence on the voltage interaction between VSC-HVDC and line commutated converter based high voltage direct current(LCC-HVDC),this paper proposes a hybrid multi-infeed interaction factor(HMIIF)calculation method considering the voltage regulation control characteristics of VSC-HVDC.Firstly,for a hybrid multi-infeed high voltage direct current system,an additional equivalent operating admittance matrix is constructed to characterize HVDC equipment characteristics under small disturbance.Secondly,based on the characteristic curve between the reactive power and the voltage of a certain VSC-HVDC project,the additional equivalent operating admittance of VSC-HVDC is derived.The additional equivalent operating admittance matrix calculation method is proposed.Thirdly,the equivalent bus impedance matrix is obtained by modifying the alternating current(AC)system admittance matrix with the additional equivalent operating admittance matrix.On this basis,the HMIIF calculation method based on the equivalent bus impedance ratio is proposed.Finally,the effectiveness of the proposed method is verified in a hybrid dual-infeed high voltage direct current system constructed in Power Systems Computer Aided Design(PSCAD),and the influence of voltage regulation control on HMIIF is analyzed.
