Micro-grid smooth switchover between different operation modes is important for steady operation and reliable power supply of micro-grid. In order to reduce the transient fluctuation of voltage and frequency during sw...Micro-grid smooth switchover between different operation modes is important for steady operation and reliable power supply of micro-grid. In order to reduce the transient fluctuation of voltage and frequency during switchover, this paper proposed a new switchover method based on controller state following. When transferring to island mode, the control method for inverter of storage device changed from PQ control to V/f control. Before switchover, the output of V/f controller is always following the output of PQ controller. So that the sudden change of output is avoided at the moment of switchover. A micro-grid model with photovoltaic and battery is built on DIgSILENT Power Factory simulation software, to simulate micro-grid switchover from grid-connected mode to island mode. Results show this method can effectively suppress the transient fluctuation of voltage and frequency, and reduce the influence of transient process on power grid. This conclusion has important practical significance on micro-grid smooth switchover from grid-con- nected mode to island mode.展开更多
An aliphatic epoxy monomer＂polypropyleneglycol-diglycidylether（PPGDGE,YF878）＂is loaded in the epoxy resins（EP）to evaluate the influence of epoxy structure on the blowing-out effect,which is caused by 9,10-dihydr...An aliphatic epoxy monomer＂polypropyleneglycol-diglycidylether（PPGDGE,YF878）＂is loaded in the epoxy resins（EP）to evaluate the influence of epoxy structure on the blowing-out effect,which is caused by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide（DOPO）and octaphenyl silsesquioxane（OPS）.The flame retarding properties of these EP composites were tested using the LOI and UL-94 procedures.The pyrolytic gases produced and the thermal stability of the EP composites with different flame retardants were detected by TGA-FTIR in air.The negative effect of YF878 was detected from the TTI,HRR,and p-HRR results after the cone calorimeter test.The char produced by the EP composites after the cone calorimeter test was investigated by FTIR.It is proposed that the aliphatic chain of the YF878 is easy to break down and produce combustible gases,so it does not easily form a crosslinked structure in the condensed phase.These results are very helpful for investigation of the conditions under which the blowing-out effect in epoxy resins can be caused by synergy of phosphorous and silicon.展开更多
储能系统作为微网的功率/能量缓冲环节,对微网的稳定控制、电能质量改善和不间断供电起着重要作用,是微网安全可靠运行的关键。首先分析了微网中储能系统常用的3种控制策略,讨论了其在微网不同运行控制模式中的应用;进而设计了一种针对...储能系统作为微网的功率/能量缓冲环节,对微网的稳定控制、电能质量改善和不间断供电起着重要作用,是微网安全可靠运行的关键。首先分析了微网中储能系统常用的3种控制策略,讨论了其在微网不同运行控制模式中的应用;进而设计了一种针对电池储能系统(battery energy storage system,BESS)逆变器外环控制器的综合控制策略,能够兼具PQ控制、V/f控制和下垂控制功能,从而既可以用于主从控制的微网,也能用于对等控制的微网;同时还考虑了微网从孤岛转入并网和并网转入孤岛的双向切换过程,对设计的BESS综合控制策略进行了改进,实现了双向的平滑切换。算例结果验证了提出的综合控制策略的有效性。展开更多
文摘Micro-grid smooth switchover between different operation modes is important for steady operation and reliable power supply of micro-grid. In order to reduce the transient fluctuation of voltage and frequency during switchover, this paper proposed a new switchover method based on controller state following. When transferring to island mode, the control method for inverter of storage device changed from PQ control to V/f control. Before switchover, the output of V/f controller is always following the output of PQ controller. So that the sudden change of output is avoided at the moment of switchover. A micro-grid model with photovoltaic and battery is built on DIgSILENT Power Factory simulation software, to simulate micro-grid switchover from grid-connected mode to island mode. Results show this method can effectively suppress the transient fluctuation of voltage and frequency, and reduce the influence of transient process on power grid. This conclusion has important practical significance on micro-grid smooth switchover from grid-con- nected mode to island mode.
基金Supported by the National Natural Science Foundation of China(51273023)China Postdoctoral Science Foundation(2014M550023)
文摘An aliphatic epoxy monomer＂polypropyleneglycol-diglycidylether（PPGDGE,YF878）＂is loaded in the epoxy resins（EP）to evaluate the influence of epoxy structure on the blowing-out effect,which is caused by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide（DOPO）and octaphenyl silsesquioxane（OPS）.The flame retarding properties of these EP composites were tested using the LOI and UL-94 procedures.The pyrolytic gases produced and the thermal stability of the EP composites with different flame retardants were detected by TGA-FTIR in air.The negative effect of YF878 was detected from the TTI,HRR,and p-HRR results after the cone calorimeter test.The char produced by the EP composites after the cone calorimeter test was investigated by FTIR.It is proposed that the aliphatic chain of the YF878 is easy to break down and produce combustible gases,so it does not easily form a crosslinked structure in the condensed phase.These results are very helpful for investigation of the conditions under which the blowing-out effect in epoxy resins can be caused by synergy of phosphorous and silicon.
文摘储能系统作为微网的功率/能量缓冲环节,对微网的稳定控制、电能质量改善和不间断供电起着重要作用,是微网安全可靠运行的关键。首先分析了微网中储能系统常用的3种控制策略,讨论了其在微网不同运行控制模式中的应用;进而设计了一种针对电池储能系统(battery energy storage system,BESS)逆变器外环控制器的综合控制策略,能够兼具PQ控制、V/f控制和下垂控制功能,从而既可以用于主从控制的微网,也能用于对等控制的微网;同时还考虑了微网从孤岛转入并网和并网转入孤岛的双向切换过程,对设计的BESS综合控制策略进行了改进,实现了双向的平滑切换。算例结果验证了提出的综合控制策略的有效性。
