On the basis of the theoretical analysis of a single-machine infinite-bus （SMIB）, using the modified linearized Phil- lips-Heffron model installed with unified power flow controller （UPFC）, the potential of the UP...On the basis of the theoretical analysis of a single-machine infinite-bus （SMIB）, using the modified linearized Phil- lips-Heffron model installed with unified power flow controller （UPFC）, the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition （SVD） analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm （GSA） that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems （FACTS） controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.展开更多
文摘背景与目的术后持续性肺漏气是肺部手术后最常见的并发症之一。数字化胸腔引流系统(digital drainage system,DDS)被认为具有准确、客观、舒适、患者耐受性好、经济等优点。本研究旨在总结DDS用于肺部手术后难治性持续性大量漏气的临床疗效。方法术后5天和7天分别是胸腔镜和开胸术后持续性肺漏气(prolonged air leak,PAL)的界限;本研究将难治性持续性大量漏气定义为达到PAL时间2倍及以上且漏气持续达2度以上,可伴有明显皮下气肿或纵隔气肿等相关并发症。2016年1月-2016年12月间,应用数字化胸腔引流系统结合胸膜固定术治疗符合上述标准的病例共8例,收集相关临床资料并总结分析。结果本组病例中肺叶切除术6例,肺段切除2例。平均术后持续漏气(17.3±5.1)d,DDS平均使用时间(5.6±3.7)d。平均术后引流量(3,550.6±1,881.1)mL。应用DDS前后的平均引流量为(2,615.6±1,741.2)mL和(935.0±242.7)mL。平均住院时间(18.1±5.0)d。结论数字化胸腔引流系统用于肺部手术后难治性持续性大量漏气安全可行,可提供更大的负压吸引值,从而促使患肺复张为后继的胸膜固定术创造条件,并缩短引流天数和住院时间。
文摘On the basis of the theoretical analysis of a single-machine infinite-bus （SMIB）, using the modified linearized Phil- lips-Heffron model installed with unified power flow controller （UPFC）, the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition （SVD） analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm （GSA） that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems （FACTS） controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.
