Background CH<sub>4</sub> concentration and seasonal variations measured at Zhongshan Station (69°22'2''S, 76°21'49''E, 18.5 m) in Antarctica from 2008 through 2013 are pr...Background CH<sub>4</sub> concentration and seasonal variations measured at Zhongshan Station (69°22'2''S, 76°21'49''E, 18.5 m) in Antarctica from 2008 through 2013 are presented and discussed. From 2008-2013 CH<sub>4</sub> was measured in weekly<sub> </sub>flask samples and started on line measurement by Picarro CO<sub>2</sub>/CH<sub>4</sub>/H<sub>2</sub>O analyzer from March, 2010-2013. These CH<sub>4</sub> measurements show the expected growth period of CH<sub>4</sub> concentration during February (Antarctic spring) with a peak in September (fall). Irrespective of wind direction, CH<sub>4</sub> concentrations distribute evenly after the removal of polluted air from station operations, accounting for 1% of the data. The mean daily cycle of CH<sub>4</sub> concentration in all four seasons is small. The monthly mean CH<sub>4</sub> concentration at Zhongshan station is similar to those at other stations in Antarctica showing that CH<sub>4</sub> observed in Antarctica is fully mixed in the atmosphere as it is transported from the northern through the southern hemisphere. The annual CH<sub>4</sub> increase in recent years at Zhongshan station is 4.8 ppb·yr<sup>-1</sup>.展开更多
新能源场站的次/超同步振荡给电力系统的安全稳定运行造成威胁,调相机可以在一定程度上抑制次/超同步振荡。为进一步发挥调相机抑制振荡的能力,提出一种基于储能型双馈调相机的多通道附加阻尼控制策略。首先,设计针对特定频段振荡的附...新能源场站的次/超同步振荡给电力系统的安全稳定运行造成威胁,调相机可以在一定程度上抑制次/超同步振荡。为进一步发挥调相机抑制振荡的能力,提出一种基于储能型双馈调相机的多通道附加阻尼控制策略。首先,设计针对特定频段振荡的附加阻尼控制器,公共耦合点(point of common coupling,PCC)的电流信号经过附加阻尼控制器调制后被输出到机侧控制系统,调节调相机的无功输出实现对系统振荡的有效抑制;其次,根据移相环节的相位补偿偏差将控制器划分为多个通道,每个通道针对特定频段进行振荡抑制;然后,使用Prony算法提取功率振荡信号进行阻尼比计算,评估多通道附加阻尼控制器的振荡抑制效果;最后,在单机系统及新能源场站系统中进行仿真,结果表明多通道附加阻尼控制策略能够显著提高储能型双馈调相机对次/超同步振荡的抑制能力。该策略提高了新能源场站的小干扰稳定性,有利于新能源发电的长期可持续发展。展开更多
文摘Background CH<sub>4</sub> concentration and seasonal variations measured at Zhongshan Station (69°22'2''S, 76°21'49''E, 18.5 m) in Antarctica from 2008 through 2013 are presented and discussed. From 2008-2013 CH<sub>4</sub> was measured in weekly<sub> </sub>flask samples and started on line measurement by Picarro CO<sub>2</sub>/CH<sub>4</sub>/H<sub>2</sub>O analyzer from March, 2010-2013. These CH<sub>4</sub> measurements show the expected growth period of CH<sub>4</sub> concentration during February (Antarctic spring) with a peak in September (fall). Irrespective of wind direction, CH<sub>4</sub> concentrations distribute evenly after the removal of polluted air from station operations, accounting for 1% of the data. The mean daily cycle of CH<sub>4</sub> concentration in all four seasons is small. The monthly mean CH<sub>4</sub> concentration at Zhongshan station is similar to those at other stations in Antarctica showing that CH<sub>4</sub> observed in Antarctica is fully mixed in the atmosphere as it is transported from the northern through the southern hemisphere. The annual CH<sub>4</sub> increase in recent years at Zhongshan station is 4.8 ppb·yr<sup>-1</sup>.
文摘新能源场站的次/超同步振荡给电力系统的安全稳定运行造成威胁,调相机可以在一定程度上抑制次/超同步振荡。为进一步发挥调相机抑制振荡的能力,提出一种基于储能型双馈调相机的多通道附加阻尼控制策略。首先,设计针对特定频段振荡的附加阻尼控制器,公共耦合点(point of common coupling,PCC)的电流信号经过附加阻尼控制器调制后被输出到机侧控制系统,调节调相机的无功输出实现对系统振荡的有效抑制;其次,根据移相环节的相位补偿偏差将控制器划分为多个通道,每个通道针对特定频段进行振荡抑制;然后,使用Prony算法提取功率振荡信号进行阻尼比计算,评估多通道附加阻尼控制器的振荡抑制效果;最后,在单机系统及新能源场站系统中进行仿真,结果表明多通道附加阻尼控制策略能够显著提高储能型双馈调相机对次/超同步振荡的抑制能力。该策略提高了新能源场站的小干扰稳定性,有利于新能源发电的长期可持续发展。
