To enhance power flow regulation in scenarios involving large-scale renewable energy transmission via high-voltage direct current(HVDC)links and multi-infeed DC systems in load-center regions,this paper proposes a hyb...To enhance power flow regulation in scenarios involving large-scale renewable energy transmission via high-voltage direct current(HVDC)links and multi-infeed DC systems in load-center regions,this paper proposes a hybrid modular multilevel converter–capacitor-commutated line-commutated converter(MMC-CLCC)HVDC transmission system and its corresponding control strategy.First,the system topology is constructed,and a submodule configuration method for the MMC—combining full-bridge submodules(FBSMs)and half-bridge submodules(HBSMs)—is proposed to enable direct power flow reversal.Second,a hierarchical control strategy is introduced,includingMMCvoltage control,CLCC current control,and a coordinationmechanism,along with the derivation of the hybrid system’s power flow reversal characteristics.Third,leveraging the CLCC’s fast current regulation and theMMC’s negative voltage control capability,a coordinated power flow reversal control strategy is developed.Finally,an 800 kV MMC-CLCC hybrid HVDC system is modeled in PSCAD/EMTDC to validate the power flow reversal performance under a high proportion of full-bridge submodule configuration.Results demonstrate that the proposed control strategy enables rapid(1-s transition)and smooth switching of bidirectional power flow without modifying the structure of primary equipment:the transient fluctuation ofDC voltage from the rated value(UdcN)to themaximumreverse voltage(-kUdcN)is less than 5%;the DC current strictly follows the preset characteristic curve with a deviation of≤3%;the active power reverses continuously,and the system maintains stable operation throughout the reversal process.展开更多
基于可控电网换相型换流器(controllable line commutated converter,CLCC)的高压直流输电技术避免了常规直流换相失败问题,为高压直流馈入电网提供了崭新途径。文章揭示CLCC高压直流输电系统的故障响应机理,对比CLCC与电网换相型换流...基于可控电网换相型换流器(controllable line commutated converter,CLCC)的高压直流输电技术避免了常规直流换相失败问题,为高压直流馈入电网提供了崭新途径。文章揭示CLCC高压直流输电系统的故障响应机理,对比CLCC与电网换相型换流器、电压源型换流器等直流输电技术的功率特性差异。针对CLCC可控换流的技术特点,提出一种基于最大触发角提升的CLCC优化控制方法,改善了CLCC的故障响应特性,提升了受端电网交流电压的恢复速度。最后,基于PSD-PSModel电力系统仿真软件,建立送受端电网机电暂态和CLCC直流电磁暂态的混合仿真模型,验证理论分析的准确性和优化控制的有效性。展开更多
To mitigate commutation failures(CFs)of a linecommutated converter based-high voltage direct current transmission system(LCC-HVDC),an evolved thyristor based full bridge sub-module(ET-FBSM)and a compound LCC(CLCC)topo...To mitigate commutation failures(CFs)of a linecommutated converter based-high voltage direct current transmission system(LCC-HVDC),an evolved thyristor based full bridge sub-module(ET-FBSM)and a compound LCC(CLCC)topology are proposed with the capability of commutation voltage compensation and DC power consumption.Under AC fault conditions,additional commutation voltage for LCC can be compensated,and rise of DC current can be suppressed,by switching the control modes of ET-FBSM,to reduce risks of CFs and improve the dynamic characteristics of LCC-HVDC systems.In this paper,working modes of the ET-FBSM and a coordinated control strategy between ET-FBSM and converter valve are presented,and the parameter selection approach for the ET-FBSM is provided.Then,a CLCC-HVDC system with ET-FBSMs embedded in the inverter station is developed in PSCAD/EMTDC to verify effectiveness of the proposed topology.Simulation results show the proposed topology can significantly reduce risks of CFs and improve dynamic performances of the overall system.展开更多
基金supported by Science and Technology Project of the headquarters of the State Grid Corporation of China(No.5500-202324492A-3-2-ZN).
文摘To enhance power flow regulation in scenarios involving large-scale renewable energy transmission via high-voltage direct current(HVDC)links and multi-infeed DC systems in load-center regions,this paper proposes a hybrid modular multilevel converter–capacitor-commutated line-commutated converter(MMC-CLCC)HVDC transmission system and its corresponding control strategy.First,the system topology is constructed,and a submodule configuration method for the MMC—combining full-bridge submodules(FBSMs)and half-bridge submodules(HBSMs)—is proposed to enable direct power flow reversal.Second,a hierarchical control strategy is introduced,includingMMCvoltage control,CLCC current control,and a coordinationmechanism,along with the derivation of the hybrid system’s power flow reversal characteristics.Third,leveraging the CLCC’s fast current regulation and theMMC’s negative voltage control capability,a coordinated power flow reversal control strategy is developed.Finally,an 800 kV MMC-CLCC hybrid HVDC system is modeled in PSCAD/EMTDC to validate the power flow reversal performance under a high proportion of full-bridge submodule configuration.Results demonstrate that the proposed control strategy enables rapid(1-s transition)and smooth switching of bidirectional power flow without modifying the structure of primary equipment:the transient fluctuation ofDC voltage from the rated value(UdcN)to themaximumreverse voltage(-kUdcN)is less than 5%;the DC current strictly follows the preset characteristic curve with a deviation of≤3%;the active power reverses continuously,and the system maintains stable operation throughout the reversal process.
文摘基于可控电网换相型换流器(controllable line commutated converter,CLCC)的高压直流输电技术避免了常规直流换相失败问题,为高压直流馈入电网提供了崭新途径。文章揭示CLCC高压直流输电系统的故障响应机理,对比CLCC与电网换相型换流器、电压源型换流器等直流输电技术的功率特性差异。针对CLCC可控换流的技术特点,提出一种基于最大触发角提升的CLCC优化控制方法,改善了CLCC的故障响应特性,提升了受端电网交流电压的恢复速度。最后,基于PSD-PSModel电力系统仿真软件,建立送受端电网机电暂态和CLCC直流电磁暂态的混合仿真模型,验证理论分析的准确性和优化控制的有效性。
文摘To mitigate commutation failures(CFs)of a linecommutated converter based-high voltage direct current transmission system(LCC-HVDC),an evolved thyristor based full bridge sub-module(ET-FBSM)and a compound LCC(CLCC)topology are proposed with the capability of commutation voltage compensation and DC power consumption.Under AC fault conditions,additional commutation voltage for LCC can be compensated,and rise of DC current can be suppressed,by switching the control modes of ET-FBSM,to reduce risks of CFs and improve the dynamic characteristics of LCC-HVDC systems.In this paper,working modes of the ET-FBSM and a coordinated control strategy between ET-FBSM and converter valve are presented,and the parameter selection approach for the ET-FBSM is provided.Then,a CLCC-HVDC system with ET-FBSMs embedded in the inverter station is developed in PSCAD/EMTDC to verify effectiveness of the proposed topology.Simulation results show the proposed topology can significantly reduce risks of CFs and improve dynamic performances of the overall system.
