With the development of power system, the level of short circuit current will increase accordingly. In general, the influence of the HVDC system and the new energy source is not considered in the calculation of the sh...With the development of power system, the level of short circuit current will increase accordingly. In general, the influence of the HVDC system and the new energy source is not considered in the calculation of the short circuit current. For the power grid that short circuit current level closes to the interrupting capacity of circuit breaker, it’s necessary to fully consider all kinds of influence factors, careful checking, so as to obtain more accurate calculation results of short circuit current. In 2018, two ±800 kV high-power Ultra High Voltage Direct Current (UHVDC) transmission projects will be connected with Shaanxi power grid, accompanied by a lot of concomitant fossil-fuel generating plants as power resource, and also a large number of new energy source, includes wind power generation and photovoltaic power generation. Around one of the UHVDC converter stations, short circuit current may exceed the withstand limit of some certain circuit breakers. In order to get more accurate short circuit current calculation results, three measures are used: 1) contrastive calculation and analysis by algorithm based on schemes and algorithm based on power flow;2) analysis the influence of UHVDC by electromagnetic transient and electromechanical transient hybrid simulation;3) considered a detailed model of Doubly Fed Induction Generator (DFIG) with low voltage ride through characteristics. The calculation results shows that: in the typical operation mode of Shaanxi power grid of 2018, the original calculation results by conventional calculation method are coincident with the results by considering the influence of algorithms, UHVDC and DFIG in large, in which: the results of the algorithm based on power flow are smaller than that of the algorithm based on schemes about 2 - 8 kA;the steady values of the short circuit current provided by UHVDC converterstation (includes rectifiers and smoothing capacitors) are about 0 - 3 kA;the steady values of the short circuit current provided by DFIG are about 0 - 5 kA. The calculation results can provide reference for the selection of the circuit breaker, and it can be verified by fault recording data in the future.展开更多
At present the detecting of ultra high voltage direct current (UHVDC) earth electrode frequently uses manual inspection. This method can't get the real-time operational data of the earth electrodes, and meanwhile,...At present the detecting of ultra high voltage direct current (UHVDC) earth electrode frequently uses manual inspection. This method can't get the real-time operational data of the earth electrodes, and meanwhile, the labor cost is very high. In order to satisfy the security needs of UHVDC, this paper designs an on-line monitoring system for UHVDC earth electrode. By 3G wireless communication-technologies, the system can monitor remotely many kinds of data such as the value of the grounding current, water level of the observation well, soil temperature and humidity near the earth electrode, the micro-climate around the earth electrode site, video data, etc. Through analyzing the datum, the system has broad prospect on fault detection and life evaluation of the UHVDC earth electrode.展开更多
对于风电和特高压直流(ultra-high voltage direct current,UHVDC)可靠性建模,已有很多独立研究。但针对含风电AC/UHVDC电力系统,同时考虑双馈异步风力发电机(doubly-fed induction generator,DFIG)结构、风电状态转移模型、交直流设备...对于风电和特高压直流(ultra-high voltage direct current,UHVDC)可靠性建模,已有很多独立研究。但针对含风电AC/UHVDC电力系统,同时考虑双馈异步风力发电机(doubly-fed induction generator,DFIG)结构、风电状态转移模型、交直流设备随机故障的研究不多,且往往基于简化DFIG结构和简化UHVDC可靠性模型。考虑上述因素,对系统进行可靠性评估和灵敏度分析。对DFIG多状态转移模型,从2种视角考虑风电出力与出力转移特性。引入直流功率调整以确定换流站控制方式。采用解析枚举、概率加权法,计算可靠性指标。提出可靠性指标对直流功率、DFIG有功出力灵敏度的解析表达。算例分析验证了所提算法的有效性和应用价值。展开更多
特高压直流(ultra-high voltage direct current,UHVDC)线路传输容量大,其可靠性对电网安全极为重要。现有UHVDC系统可靠性研究只考虑长期可靠性,不能反映元件故障后可靠性短时变化。基于UHVDC换流站结构、瞬时状态概率和稳态等值算法,...特高压直流(ultra-high voltage direct current,UHVDC)线路传输容量大,其可靠性对电网安全极为重要。现有UHVDC系统可靠性研究只考虑长期可靠性,不能反映元件故障后可靠性短时变化。基于UHVDC换流站结构、瞬时状态概率和稳态等值算法,提出了暂态分层等值算法以建立换流站瞬时状态空间等值模型,同时提出了具有时变特性的双极可用率和双极停运率等可靠性指标。引入平均概率算法,计算换流站状态概率和可靠性指标在一段时间内的均值。所提模型拓展了现有UHVDC系统可靠性评估算法和指标,有利于量化其短期运行风险。通过与瞬时状态概率算法作比较,验证了所提暂态分层等值算法的正确性。结果表明UHVDC换流站瞬时状态概率与其稳态值存在差异,从不同初始状态向稳态值收敛。展开更多
特高压直流输电(ultra high voltage direct current,简称UHVDC)已在电力系统广泛应用.针对哈—郑UHVDC线路送端无功储备不足导致换流站直流功率波动的问题,提出在送端安装大容量新型调相机,将其作为动态无功补偿设备.分析大容量新型调...特高压直流输电(ultra high voltage direct current,简称UHVDC)已在电力系统广泛应用.针对哈—郑UHVDC线路送端无功储备不足导致换流站直流功率波动的问题,提出在送端安装大容量新型调相机,将其作为动态无功补偿设备.分析大容量新型调相机运行机理及无功功率特性.建立UHVDC数学模型,分析得到影响直流功率波动的因素,提出改善功率波动的方法.在Simulink平台上搭建哈—郑UHVDC线路仿真模型,仿真结果表明大容量新型调相机能降低送、受端有功功率波动的幅度,缩短故障发生后功率恢复的时间,为系统提供无功功率支撑.展开更多
文摘With the development of power system, the level of short circuit current will increase accordingly. In general, the influence of the HVDC system and the new energy source is not considered in the calculation of the short circuit current. For the power grid that short circuit current level closes to the interrupting capacity of circuit breaker, it’s necessary to fully consider all kinds of influence factors, careful checking, so as to obtain more accurate calculation results of short circuit current. In 2018, two ±800 kV high-power Ultra High Voltage Direct Current (UHVDC) transmission projects will be connected with Shaanxi power grid, accompanied by a lot of concomitant fossil-fuel generating plants as power resource, and also a large number of new energy source, includes wind power generation and photovoltaic power generation. Around one of the UHVDC converter stations, short circuit current may exceed the withstand limit of some certain circuit breakers. In order to get more accurate short circuit current calculation results, three measures are used: 1) contrastive calculation and analysis by algorithm based on schemes and algorithm based on power flow;2) analysis the influence of UHVDC by electromagnetic transient and electromechanical transient hybrid simulation;3) considered a detailed model of Doubly Fed Induction Generator (DFIG) with low voltage ride through characteristics. The calculation results shows that: in the typical operation mode of Shaanxi power grid of 2018, the original calculation results by conventional calculation method are coincident with the results by considering the influence of algorithms, UHVDC and DFIG in large, in which: the results of the algorithm based on power flow are smaller than that of the algorithm based on schemes about 2 - 8 kA;the steady values of the short circuit current provided by UHVDC converterstation (includes rectifiers and smoothing capacitors) are about 0 - 3 kA;the steady values of the short circuit current provided by DFIG are about 0 - 5 kA. The calculation results can provide reference for the selection of the circuit breaker, and it can be verified by fault recording data in the future.
文摘At present the detecting of ultra high voltage direct current (UHVDC) earth electrode frequently uses manual inspection. This method can't get the real-time operational data of the earth electrodes, and meanwhile, the labor cost is very high. In order to satisfy the security needs of UHVDC, this paper designs an on-line monitoring system for UHVDC earth electrode. By 3G wireless communication-technologies, the system can monitor remotely many kinds of data such as the value of the grounding current, water level of the observation well, soil temperature and humidity near the earth electrode, the micro-climate around the earth electrode site, video data, etc. Through analyzing the datum, the system has broad prospect on fault detection and life evaluation of the UHVDC earth electrode.
文摘对于风电和特高压直流(ultra-high voltage direct current,UHVDC)可靠性建模,已有很多独立研究。但针对含风电AC/UHVDC电力系统,同时考虑双馈异步风力发电机(doubly-fed induction generator,DFIG)结构、风电状态转移模型、交直流设备随机故障的研究不多,且往往基于简化DFIG结构和简化UHVDC可靠性模型。考虑上述因素,对系统进行可靠性评估和灵敏度分析。对DFIG多状态转移模型,从2种视角考虑风电出力与出力转移特性。引入直流功率调整以确定换流站控制方式。采用解析枚举、概率加权法,计算可靠性指标。提出可靠性指标对直流功率、DFIG有功出力灵敏度的解析表达。算例分析验证了所提算法的有效性和应用价值。
文摘特高压直流(ultra-high voltage direct current,UHVDC)线路传输容量大,其可靠性对电网安全极为重要。现有UHVDC系统可靠性研究只考虑长期可靠性,不能反映元件故障后可靠性短时变化。基于UHVDC换流站结构、瞬时状态概率和稳态等值算法,提出了暂态分层等值算法以建立换流站瞬时状态空间等值模型,同时提出了具有时变特性的双极可用率和双极停运率等可靠性指标。引入平均概率算法,计算换流站状态概率和可靠性指标在一段时间内的均值。所提模型拓展了现有UHVDC系统可靠性评估算法和指标,有利于量化其短期运行风险。通过与瞬时状态概率算法作比较,验证了所提暂态分层等值算法的正确性。结果表明UHVDC换流站瞬时状态概率与其稳态值存在差异,从不同初始状态向稳态值收敛。
文摘特高压直流输电(ultra high voltage direct current,简称UHVDC)已在电力系统广泛应用.针对哈—郑UHVDC线路送端无功储备不足导致换流站直流功率波动的问题,提出在送端安装大容量新型调相机,将其作为动态无功补偿设备.分析大容量新型调相机运行机理及无功功率特性.建立UHVDC数学模型,分析得到影响直流功率波动的因素,提出改善功率波动的方法.在Simulink平台上搭建哈—郑UHVDC线路仿真模型,仿真结果表明大容量新型调相机能降低送、受端有功功率波动的幅度,缩短故障发生后功率恢复的时间,为系统提供无功功率支撑.
