The hybrid cascaded high-voltage direct current(HVDC)transmission system has various operation modes,and some operation modes have sharply increasing requirements for protection rapidity,while the traditional pilot di...The hybrid cascaded high-voltage direct current(HVDC)transmission system has various operation modes,and some operation modes have sharply increasing requirements for protection rapidity,while the traditional pilot differential protection(PDP)has poor rapidity,and even refuses to operate when faults occur on the DC line.Therefore,a novel pilot protection scheme based on traveling wave characteristics is proposed.First,the adaptability of the traditional PDP applied in engineering is analyzed for different operation modes.Then,the expressions of the forward traveling wave(FTW)and backward traveling wave(BTW)on the rectifier side and the inverter side are derived for different fault locations.From the theoretical derivation,the difference between the BTW and FTW on the rectifier side is less than zero,and the same is true on the inverter side.However,in the event of an external fault of DC line,the difference between the BTW and FTW at nearfault terminal protection installation point is greater than zero.Therefore,by summing over the product of the difference between BTW and FTW of the rectifier side and that of the inverter side,the fault identification criterion is constructed.The simulation results show that the proposed pilot protection scheme can quickly and reliably identify the short-circuit faults of DC line in different operation modes.展开更多
在电力高压站高压隔离开关动作时,产生的特快速暂态过电压(very fast transient overvoltage,VFTO)耦合到二次电缆传输信号中,会造成测量的不准确和设备的误动作。以提高继电保护抗干扰能力为目的,建立并分析“接地网-二次电缆-智能组...在电力高压站高压隔离开关动作时,产生的特快速暂态过电压(very fast transient overvoltage,VFTO)耦合到二次电缆传输信号中,会造成测量的不准确和设备的误动作。以提高继电保护抗干扰能力为目的,建立并分析“接地网-二次电缆-智能组件”的耦合路径,根据电力系统理想采样点的信号特征,提出应对接地网电位差干扰的算法,采用启动元件和判定元件快速判断采样值是否为干扰信号,根据高压隔离开关动作引起的接地网电位差干扰信号幅值高、上升时间短和频带范围宽的暂态特性,采用小波变换作为滤波算法。仿真实验结果表明,此滤波算法能够有效地滤除隔离开关动作引起的接地网电位差干扰信号,均方根误差减少91.6%,信噪比提高138.5%,保证了继电保护数据测量的准确性,提高了电力系统继电保护的可靠性。展开更多
The recent in-depth development of hybrid highvoltage direct current(HVDC) transmission systems poses looming adaptability challenges to protection. The various and disparate direct current(DC) transmission topologies...The recent in-depth development of hybrid highvoltage direct current(HVDC) transmission systems poses looming adaptability challenges to protection. The various and disparate direct current(DC) transmission topologies can profoundly affect the operating characteristics of DC transmission networks, which result in the lack of performance of conventional DC protection schemes in such topologies. This significantly limits the application of hybrid HVDC technologies. This paper proposes a single-end protection scheme based on the transient power waveshape for fast and sensitive detection and classification of different types of DC faults in hybrid HVDC transmission lines. The fault characteristics and their causes under different fault conditions are analyzed in detail with a pre-introduced linearized transient model of a hybrid HVDC transmission system, demonstrating that the formation of the fluctuation characteristics of local measurements is mainly determined by the buffering and absorption effects of lumped-parameter reactors on transient traveling-wave(TW) energy. Simulation results verify the sensitivity, rapidity, reliability, and anti-interference ability of the proposed scheme when applied to hybrid HVDC transmission lines. Furthermore, it is confirmed that the proposed scheme is adaptable to symmetric voltage-sourced converter(VSC) and conventional line-commutated converter(LCC) based HVDC transmission lines.展开更多
基金supported in part by the National Natural Science Foundation of China(No.51977183)。
文摘The hybrid cascaded high-voltage direct current(HVDC)transmission system has various operation modes,and some operation modes have sharply increasing requirements for protection rapidity,while the traditional pilot differential protection(PDP)has poor rapidity,and even refuses to operate when faults occur on the DC line.Therefore,a novel pilot protection scheme based on traveling wave characteristics is proposed.First,the adaptability of the traditional PDP applied in engineering is analyzed for different operation modes.Then,the expressions of the forward traveling wave(FTW)and backward traveling wave(BTW)on the rectifier side and the inverter side are derived for different fault locations.From the theoretical derivation,the difference between the BTW and FTW on the rectifier side is less than zero,and the same is true on the inverter side.However,in the event of an external fault of DC line,the difference between the BTW and FTW at nearfault terminal protection installation point is greater than zero.Therefore,by summing over the product of the difference between BTW and FTW of the rectifier side and that of the inverter side,the fault identification criterion is constructed.The simulation results show that the proposed pilot protection scheme can quickly and reliably identify the short-circuit faults of DC line in different operation modes.
文摘在电力高压站高压隔离开关动作时,产生的特快速暂态过电压(very fast transient overvoltage,VFTO)耦合到二次电缆传输信号中,会造成测量的不准确和设备的误动作。以提高继电保护抗干扰能力为目的,建立并分析“接地网-二次电缆-智能组件”的耦合路径,根据电力系统理想采样点的信号特征,提出应对接地网电位差干扰的算法,采用启动元件和判定元件快速判断采样值是否为干扰信号,根据高压隔离开关动作引起的接地网电位差干扰信号幅值高、上升时间短和频带范围宽的暂态特性,采用小波变换作为滤波算法。仿真实验结果表明,此滤波算法能够有效地滤除隔离开关动作引起的接地网电位差干扰信号,均方根误差减少91.6%,信噪比提高138.5%,保证了继电保护数据测量的准确性,提高了电力系统继电保护的可靠性。
基金supported by the Science and Technology Project of State Grid Corporation of China “Research on ultra-high-speed protection and fault isolation technology of transmission lines in DC power grid with different structures”(No. 5100-202155030A-0-0-00)。
文摘The recent in-depth development of hybrid highvoltage direct current(HVDC) transmission systems poses looming adaptability challenges to protection. The various and disparate direct current(DC) transmission topologies can profoundly affect the operating characteristics of DC transmission networks, which result in the lack of performance of conventional DC protection schemes in such topologies. This significantly limits the application of hybrid HVDC technologies. This paper proposes a single-end protection scheme based on the transient power waveshape for fast and sensitive detection and classification of different types of DC faults in hybrid HVDC transmission lines. The fault characteristics and their causes under different fault conditions are analyzed in detail with a pre-introduced linearized transient model of a hybrid HVDC transmission system, demonstrating that the formation of the fluctuation characteristics of local measurements is mainly determined by the buffering and absorption effects of lumped-parameter reactors on transient traveling-wave(TW) energy. Simulation results verify the sensitivity, rapidity, reliability, and anti-interference ability of the proposed scheme when applied to hybrid HVDC transmission lines. Furthermore, it is confirmed that the proposed scheme is adaptable to symmetric voltage-sourced converter(VSC) and conventional line-commutated converter(LCC) based HVDC transmission lines.
