现有电网换相换流器型高压直流输电(line commutated converter based HVDC,LCC-HVDC)输电系统动态等值计算依赖于送受端电压同步实时量测,无法实现经LCC-HVDC输电送出系统的单端暂态等值计算。论文基于直流系统动态相量等值计算框架,...现有电网换相换流器型高压直流输电(line commutated converter based HVDC,LCC-HVDC)输电系统动态等值计算依赖于送受端电压同步实时量测,无法实现经LCC-HVDC输电送出系统的单端暂态等值计算。论文基于直流系统动态相量等值计算框架,提出仅基于逆变侧单端交流电压信息的经LCC-HVDC直流输电送出系统的等值计算方案,论证整流侧准稳态模型+逆变侧动态相量模型的混合等值计算框架的可行性,解决换相失败准确判别等关键问题,仿真对比分析了多场景故障,证明所提出的计算框架在送端交流系统信息缺失的情况下,能实现受端交流线路故障暂态大扰动下经LCC-HVDC输电送出系统响应的准确实时计算。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
Once an asymmetrical fault occurs on the AC side of the receiving-end of a high-voltage direct current(HVDC)transmission system,the current reference will be affected by the control regulation on the DC inverter side ...Once an asymmetrical fault occurs on the AC side of the receiving-end of a high-voltage direct current(HVDC)transmission system,the current reference will be affected by the control regulation on the DC inverter side and the commutation voltage asymmetry.In this case,the advance firing angle will fluctuate periodically,causing security threats to the system.If the fault cannot be cleared in time,the effect may be even more serious.However,the traditional proportional-integral(PI)controller cannot effectively suppress the periodic components in the input error signal,which is an important cause of continuous commutation failure.Thus,the system requires more time to recover from the fault.Motivated by this,a selfadaptive auto-disturbance rejection PI controller is proposed in this study.The controller has the advantages of fast response speed and strong anti-interference ability of the auto-disturbance rejection controller.On one hand,it can automatically adjust PI,and the parameters can maintain the system’s adaptive ability.On the other hand,the discretization process satisfies the computer simulation requirements.By applying the proposed controller to a system under constant current control and extinction angle control,the dynamic response speed can be improved and the robust performance of the system can be ensured when dealing with a wide range of perturbations.Finally,simulation results show that the proposed algorithm can effectively suppress the continuous commutation failure of DC transmission systems.展开更多
For the hybrid multi-infeed HVDC system in which the receiving-end grid is a strong AC grid including LCC-HVDC subsystems and multiple VSC-HVDC subsystems,it has higher voltage support capability.However,for weak AC g...For the hybrid multi-infeed HVDC system in which the receiving-end grid is a strong AC grid including LCC-HVDC subsystems and multiple VSC-HVDC subsystems,it has higher voltage support capability.However,for weak AC grid,the voltage support capability of the multi-VSC-HVDC subsystems to the LCC-HVDC subsystem(voltage support capability-mVSCs-LCC)can resist the risk of commutation failure.Based on this consideration,this paper proposes an evaluation index called Dynamic Voltage Support Strength Factor(DVSF)for the hybrid multi-infeed system,and uses this index to qualitatively judge the voltage support capability-mVSCs-LCC in weak AC grid.In addition,the proposed evaluation index can also indirectly judge the ability of the LCC-HVDC subsystem to suppress commutation failure.Firstly,the mathematical model of the power flow of the LCC and VSC networks in the steady-state is analyzed,and the concept of DVSF applied to hybrid multi-infeed system is proposed.Furthermore,the DVSF index is also used to qualitatively judge the voltage support capability-mVSCs-LCC.Secondly,the influence of multiple VSC-HVDC subsystems with different operation strategies on the DVSF is analyzed with reference to the concept of DVSF.Finally,the indicators proposed in this paper are compared with other evaluation indicators through MATLAB simulation software to verify its effectiveness.More importantly,the effects of multi-VSC-HVDC subsystems using different coordinated control strategies on the voltage support capability of the receiving-end LCC-HVDC subsystem are also verified.展开更多
Line-commutated converter based high-voltage direct-current(LCC-HVDC)transmission systems are prone to subsequent commutation failure(SCF),which consequently leads to the forced blocking of HVDC links,affecting the op...Line-commutated converter based high-voltage direct-current(LCC-HVDC)transmission systems are prone to subsequent commutation failure(SCF),which consequently leads to the forced blocking of HVDC links,affecting the operation of the power system.An accurate commutation failure(CF)identification is fairly vital to the prevention of SCF.However,the existing CF identification methods cause CF misjudge or detection lag,which can limit the effect of SCF mitigation strategy.In addition,earlier approaches to suppress SCF do not clarify the key factor that determines the evolution of extinction angle during system recovery and neglect the influence.Hence,this paper firstly analyzes the normal commutation process and CF feature based on the evolution topology of converter valve conduction in detail.Secondly,the energy in the leakage inductance of converter transformer is presented to characterize the commutation state of the valves.Then a CF identification method is proposed utilizing the leakage inductance energy.Thirdly,taking the key variable which is crucial to the tendency of extinction angle during the recovery process into account,a fault current limiting strategy for SCF mitigation is put forward.Compared with the original methods,the proposed methods have a better performance in CF identification and mitigation in terms of detection accuracy and mitigation effect.Finally,case study on PSCAD/EMTDC validates the proposed methods.展开更多
The Brazilian transmission system is facing challenging problems with the distance between its generation areas and consumer centers that will be partly solved by the use of HVDC point-to-point systems.In the near fut...The Brazilian transmission system is facing challenging problems with the distance between its generation areas and consumer centers that will be partly solved by the use of HVDC point-to-point systems.In the near future,the southeast subsystem will have a large amount of power injected through HVDC Systems in multiple points with relatively close electrical proximity.Therefore,the effects of a multi-infeed system are expected to influence the performance and operation of the network.Extensive studies and simulations will play an important role in determining the extension of the interactions among HVDC converters and determine if such interactions cause multiple commutation failures,thus disturbing the dynamic stability of the system.The use of CCC(Capacitor Commutated Converter)HVDC systems will also be assessed and is expected to diminish the need for a strong AC network(high short circuit level)and,therefore,mitigate multi-infeed interactions.The southeast subsystem of the Brazilian Power System currently has four LCC inverters,two of them belong to the Madeira power plant and the other two are from the Itaipu power plant.By the year 2024,four other HVDC systems will be arriving in the same region.This paper discusses the HVDC multi-infeed phenomena regarding the relevance of using synchronous machine models to represent important power plants and the application of mitigation methods regarding the 2020 network model,where six HVDC links will be present.展开更多
换相失败在高压直流输电系统(high voltage direct current power transmission,HVDC)中时有发生。针对现有自校正控制器依赖参考模型的局限性和模糊自适应PI控制器运算复杂且需先判断出故障类型再选择最优控制方式的局限性,采用一种基...换相失败在高压直流输电系统(high voltage direct current power transmission,HVDC)中时有发生。针对现有自校正控制器依赖参考模型的局限性和模糊自适应PI控制器运算复杂且需先判断出故障类型再选择最优控制方式的局限性,采用一种基于比例积分运算式离散化推导的自适应PI控制器,提出抑制HVDC系统换相失败的自适应PI控制方法。通过对原始CIGRE HVDC标准模型和含直流电流预测控制和换相失败预防控制(commutation failure prevention,CFPREV)模块的CIGRE HVDC系统的仿真,结果表明:在40组测试中,有37组的临界换相失败电抗得到降低。相比现有系统中参数固定的PI控制器,该自适应PI控制方法能够有效抑制HVDC系统的换相失败。展开更多
为解决交流大扰动下电网换相换流器型高压直流(line commutated converter based HVDC,LCC-HVDC)输电系统等值计算模型中整流侧信息不易获取的问题,基于动态相量模型和准稳态模型,建立基于受端交流信息下LCC-HVDC的建模方法,针对受端换...为解决交流大扰动下电网换相换流器型高压直流(line commutated converter based HVDC,LCC-HVDC)输电系统等值计算模型中整流侧信息不易获取的问题,基于动态相量模型和准稳态模型,建立基于受端交流信息下LCC-HVDC的建模方法,针对受端换流器容易发生的换相失败问题,创建基于换相机理的开关函数的修改方法。故障仿真结果表明,该方法可以较为准确地反映受端交流扰动下的暂态响应特征,同时该方法还提高了计算速度,实现了仅基于受端交流信息下LCC-HVDC的高精度、实时化计算。展开更多
针对一种由高压直流输电(high voltage DC,HVDC)系统引起汽轮发电机轴系扭振现象的机理,首先分析逆变站所连交流系统扰动时,逆变站换流阀组的换相失败过程,分析得出逆变站换流阀组换相失败引起整流站附近的汽轮发电机轴系扰动,引起发电...针对一种由高压直流输电(high voltage DC,HVDC)系统引起汽轮发电机轴系扭振现象的机理,首先分析逆变站所连交流系统扰动时,逆变站换流阀组的换相失败过程,分析得出逆变站换流阀组换相失败引起整流站附近的汽轮发电机轴系扰动,引起发电机转矩的变化,而HVDC系统不恰当的控制,为扰动提供负阻尼,从而形成一种正反馈性质的扭振相互作用,最终使得发电机出现轴系扭振。采用时域与频域相结合的仿真方法计算复转矩系数,并仿真再现由HVDC系统引起的轴系扭振现象。研究成果为交直流互联系统次同步振荡预测和分析提供理论依据。展开更多
文摘现有电网换相换流器型高压直流输电(line commutated converter based HVDC,LCC-HVDC)输电系统动态等值计算依赖于送受端电压同步实时量测,无法实现经LCC-HVDC输电送出系统的单端暂态等值计算。论文基于直流系统动态相量等值计算框架,提出仅基于逆变侧单端交流电压信息的经LCC-HVDC直流输电送出系统的等值计算方案,论证整流侧准稳态模型+逆变侧动态相量模型的混合等值计算框架的可行性,解决换相失败准确判别等关键问题,仿真对比分析了多场景故障,证明所提出的计算框架在送端交流系统信息缺失的情况下,能实现受端交流线路故障暂态大扰动下经LCC-HVDC输电送出系统响应的准确实时计算。
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 by the Science and Technology Project of State Grid Corporation of China(No.524608170147)
文摘Once an asymmetrical fault occurs on the AC side of the receiving-end of a high-voltage direct current(HVDC)transmission system,the current reference will be affected by the control regulation on the DC inverter side and the commutation voltage asymmetry.In this case,the advance firing angle will fluctuate periodically,causing security threats to the system.If the fault cannot be cleared in time,the effect may be even more serious.However,the traditional proportional-integral(PI)controller cannot effectively suppress the periodic components in the input error signal,which is an important cause of continuous commutation failure.Thus,the system requires more time to recover from the fault.Motivated by this,a selfadaptive auto-disturbance rejection PI controller is proposed in this study.The controller has the advantages of fast response speed and strong anti-interference ability of the auto-disturbance rejection controller.On one hand,it can automatically adjust PI,and the parameters can maintain the system’s adaptive ability.On the other hand,the discretization process satisfies the computer simulation requirements.By applying the proposed controller to a system under constant current control and extinction angle control,the dynamic response speed can be improved and the robust performance of the system can be ensured when dealing with a wide range of perturbations.Finally,simulation results show that the proposed algorithm can effectively suppress the continuous commutation failure of DC transmission systems.
基金supported by the National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid(No.U2066210).
文摘For the hybrid multi-infeed HVDC system in which the receiving-end grid is a strong AC grid including LCC-HVDC subsystems and multiple VSC-HVDC subsystems,it has higher voltage support capability.However,for weak AC grid,the voltage support capability of the multi-VSC-HVDC subsystems to the LCC-HVDC subsystem(voltage support capability-mVSCs-LCC)can resist the risk of commutation failure.Based on this consideration,this paper proposes an evaluation index called Dynamic Voltage Support Strength Factor(DVSF)for the hybrid multi-infeed system,and uses this index to qualitatively judge the voltage support capability-mVSCs-LCC in weak AC grid.In addition,the proposed evaluation index can also indirectly judge the ability of the LCC-HVDC subsystem to suppress commutation failure.Firstly,the mathematical model of the power flow of the LCC and VSC networks in the steady-state is analyzed,and the concept of DVSF applied to hybrid multi-infeed system is proposed.Furthermore,the DVSF index is also used to qualitatively judge the voltage support capability-mVSCs-LCC.Secondly,the influence of multiple VSC-HVDC subsystems with different operation strategies on the DVSF is analyzed with reference to the concept of DVSF.Finally,the indicators proposed in this paper are compared with other evaluation indicators through MATLAB simulation software to verify its effectiveness.More importantly,the effects of multi-VSC-HVDC subsystems using different coordinated control strategies on the voltage support capability of the receiving-end LCC-HVDC subsystem are also verified.
基金supported by the National Natural Science Foundation of China(No.51977183).
文摘Line-commutated converter based high-voltage direct-current(LCC-HVDC)transmission systems are prone to subsequent commutation failure(SCF),which consequently leads to the forced blocking of HVDC links,affecting the operation of the power system.An accurate commutation failure(CF)identification is fairly vital to the prevention of SCF.However,the existing CF identification methods cause CF misjudge or detection lag,which can limit the effect of SCF mitigation strategy.In addition,earlier approaches to suppress SCF do not clarify the key factor that determines the evolution of extinction angle during system recovery and neglect the influence.Hence,this paper firstly analyzes the normal commutation process and CF feature based on the evolution topology of converter valve conduction in detail.Secondly,the energy in the leakage inductance of converter transformer is presented to characterize the commutation state of the valves.Then a CF identification method is proposed utilizing the leakage inductance energy.Thirdly,taking the key variable which is crucial to the tendency of extinction angle during the recovery process into account,a fault current limiting strategy for SCF mitigation is put forward.Compared with the original methods,the proposed methods have a better performance in CF identification and mitigation in terms of detection accuracy and mitigation effect.Finally,case study on PSCAD/EMTDC validates the proposed methods.
基金This research was supported by ANEEL(Brazilian Energy Regulatory Agency)and the State Grid Brazilian Holding,as well as the University of Sao Paulo.
文摘The Brazilian transmission system is facing challenging problems with the distance between its generation areas and consumer centers that will be partly solved by the use of HVDC point-to-point systems.In the near future,the southeast subsystem will have a large amount of power injected through HVDC Systems in multiple points with relatively close electrical proximity.Therefore,the effects of a multi-infeed system are expected to influence the performance and operation of the network.Extensive studies and simulations will play an important role in determining the extension of the interactions among HVDC converters and determine if such interactions cause multiple commutation failures,thus disturbing the dynamic stability of the system.The use of CCC(Capacitor Commutated Converter)HVDC systems will also be assessed and is expected to diminish the need for a strong AC network(high short circuit level)and,therefore,mitigate multi-infeed interactions.The southeast subsystem of the Brazilian Power System currently has four LCC inverters,two of them belong to the Madeira power plant and the other two are from the Itaipu power plant.By the year 2024,four other HVDC systems will be arriving in the same region.This paper discusses the HVDC multi-infeed phenomena regarding the relevance of using synchronous machine models to represent important power plants and the application of mitigation methods regarding the 2020 network model,where six HVDC links will be present.
文摘换相失败在高压直流输电系统(high voltage direct current power transmission,HVDC)中时有发生。针对现有自校正控制器依赖参考模型的局限性和模糊自适应PI控制器运算复杂且需先判断出故障类型再选择最优控制方式的局限性,采用一种基于比例积分运算式离散化推导的自适应PI控制器,提出抑制HVDC系统换相失败的自适应PI控制方法。通过对原始CIGRE HVDC标准模型和含直流电流预测控制和换相失败预防控制(commutation failure prevention,CFPREV)模块的CIGRE HVDC系统的仿真,结果表明:在40组测试中,有37组的临界换相失败电抗得到降低。相比现有系统中参数固定的PI控制器,该自适应PI控制方法能够有效抑制HVDC系统的换相失败。
文摘为解决交流大扰动下电网换相换流器型高压直流(line commutated converter based HVDC,LCC-HVDC)输电系统等值计算模型中整流侧信息不易获取的问题,基于动态相量模型和准稳态模型,建立基于受端交流信息下LCC-HVDC的建模方法,针对受端换流器容易发生的换相失败问题,创建基于换相机理的开关函数的修改方法。故障仿真结果表明,该方法可以较为准确地反映受端交流扰动下的暂态响应特征,同时该方法还提高了计算速度,实现了仅基于受端交流信息下LCC-HVDC的高精度、实时化计算。
文摘针对一种由高压直流输电(high voltage DC,HVDC)系统引起汽轮发电机轴系扭振现象的机理,首先分析逆变站所连交流系统扰动时,逆变站换流阀组的换相失败过程,分析得出逆变站换流阀组换相失败引起整流站附近的汽轮发电机轴系扰动,引起发电机转矩的变化,而HVDC系统不恰当的控制,为扰动提供负阻尼,从而形成一种正反馈性质的扭振相互作用,最终使得发电机出现轴系扭振。采用时域与频域相结合的仿真方法计算复转矩系数,并仿真再现由HVDC系统引起的轴系扭振现象。研究成果为交直流互联系统次同步振荡预测和分析提供理论依据。
