针对柔性直流配电网故障特征复杂、暂态特征量不明显,故障难以快速识别、定位等问题,提出了一种分层级的区域式保护方法。该方法将多端柔直配电网划分为两个层级,通过联络线上的保护装置为节点将每个层级划分为多个保护区域,采用Pearso...针对柔性直流配电网故障特征复杂、暂态特征量不明显,故障难以快速识别、定位等问题,提出了一种分层级的区域式保护方法。该方法将多端柔直配电网划分为两个层级,通过联络线上的保护装置为节点将每个层级划分为多个保护区域,采用Pearson相似度方法作为实际电流方向与电流参考方向判据,利用GOOSE通讯分别与不同层级同区域内的保护装置交互电流信息完成故障区域的定位与故障隔离。方案能够有效避免直流故障特征量信息不明显,复杂电磁环境对保护的影响,减少了区域式保护故障搜寻的范围及暂态量信息的交互。最后,在实时数字仿真系统(real time digital simulation,RTDS)中搭建四端柔直配电网模型并模拟多种故障类型验证保护方案的可行性。结果表明所提保护方法能够在不同故障情况下可靠动作,满足保护的速动性与选择性,并具有一定抗干扰能力。展开更多
柔性直流电网的故障检测与保护研究是当前电力领域的关键技术。直流电网发生故障时,故障电流迅速上升导致电网系统设备损坏且稳定性下降,因此对故障保护系统的快速性和可靠性要求极高。通过比较线路上限流电感电压值在故障前后的变化,...柔性直流电网的故障检测与保护研究是当前电力领域的关键技术。直流电网发生故障时,故障电流迅速上升导致电网系统设备损坏且稳定性下降,因此对故障保护系统的快速性和可靠性要求极高。通过比较线路上限流电感电压值在故障前后的变化,提出一种利用限流电感两端电压比值实现线路故障识别的方法。在PSCAD/EMTDC仿真平台建立四端模块化多电平换流器型柔性直流输电(modular multilevel converter high voltage direct current,MMC-HVDC)电网模型,对所提出的方法进行故障启动、类型识别和极线选择验证。在故障被正确识别后,相应的直流断路器(DC circuit breaker,DCCB)能够正确动作并隔离故障。此外,还对系统的性能指标以及故障过渡电阻值、故障后系统的噪声、故障距离和通信误差方面因素进行可行性分析。研究结果表明,所提出的故障保护方案能够准确识别并且快速隔离故障,从而保障电网安全稳定运行。展开更多
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
文摘针对柔性直流配电网故障特征复杂、暂态特征量不明显,故障难以快速识别、定位等问题,提出了一种分层级的区域式保护方法。该方法将多端柔直配电网划分为两个层级,通过联络线上的保护装置为节点将每个层级划分为多个保护区域,采用Pearson相似度方法作为实际电流方向与电流参考方向判据,利用GOOSE通讯分别与不同层级同区域内的保护装置交互电流信息完成故障区域的定位与故障隔离。方案能够有效避免直流故障特征量信息不明显,复杂电磁环境对保护的影响,减少了区域式保护故障搜寻的范围及暂态量信息的交互。最后,在实时数字仿真系统(real time digital simulation,RTDS)中搭建四端柔直配电网模型并模拟多种故障类型验证保护方案的可行性。结果表明所提保护方法能够在不同故障情况下可靠动作,满足保护的速动性与选择性,并具有一定抗干扰能力。
文摘柔性直流电网的故障检测与保护研究是当前电力领域的关键技术。直流电网发生故障时,故障电流迅速上升导致电网系统设备损坏且稳定性下降,因此对故障保护系统的快速性和可靠性要求极高。通过比较线路上限流电感电压值在故障前后的变化,提出一种利用限流电感两端电压比值实现线路故障识别的方法。在PSCAD/EMTDC仿真平台建立四端模块化多电平换流器型柔性直流输电(modular multilevel converter high voltage direct current,MMC-HVDC)电网模型,对所提出的方法进行故障启动、类型识别和极线选择验证。在故障被正确识别后,相应的直流断路器(DC circuit breaker,DCCB)能够正确动作并隔离故障。此外,还对系统的性能指标以及故障过渡电阻值、故障后系统的噪声、故障距离和通信误差方面因素进行可行性分析。研究结果表明,所提出的故障保护方案能够准确识别并且快速隔离故障,从而保障电网安全稳定运行。
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.
