Hybrid AC/DC distribution networks are promising candidates for future applications due to their rapid advancement in power electronics technology.They use interface converters(IFCs)to link DC and AC distribution netw...Hybrid AC/DC distribution networks are promising candidates for future applications due to their rapid advancement in power electronics technology.They use interface converters(IFCs)to link DC and AC distribution networks.However,the networks possess drawbacks with AC voltage and frequency offsets when transferring from grid-tied to islanding modes.To address these problems,this paper proposes a simple but effective strategy based on the reverse droop method.Initially,the power balance equation of the distribution system is derived,which reveals that the cause of voltage and frequency offsets is the mismatch between the IFC output power and the rated load power.Then,the reverse droop control is introduced into the IFC controller.By using a voltage-active power/frequency-reactive power(U-P/f-Q)reverse droop loop,the IFC output power enables adaptive tracking of the rated load power.Therefore,the AC voltage offset and frequency offset are suppressed during the transfer process of operational modes.In addition,the universal parameter design method is discussed based on the stability limitations of the control system and the voltage quality requirements of AC critical loads.Finally,simulation and experimental results clearly validate the proposed control strategy and parameter design method.展开更多
根据某公司员工自助服务的需求,针对在ERP系统中没有登录账号,仍然需要实现对员工自己相关人事信息提供自助服务的特殊要求,提出了安全可行的企业门户、EP和ERP三系统的集成方案,满足了单点登录的要求。对系统的架构进行了详细设计,论...根据某公司员工自助服务的需求,针对在ERP系统中没有登录账号,仍然需要实现对员工自己相关人事信息提供自助服务的特殊要求,提出了安全可行的企业门户、EP和ERP三系统的集成方案,满足了单点登录的要求。对系统的架构进行了详细设计,论述了权限的控制方案,并对关键部分的程序进行了设计和代码实现。所设计的员工自助服务系统基于B/S运行模式,采用Web Dynpro for Abap技术开发,程序界面的易操作性接近Windows程序,交互性能在Web程序中具有绝对的优势。此外,系统在确保安全可靠、权限控制到位的前提下,实现了不具备ERP账号的员工对自己在ERP系统中的人事信息维护,而且为了促使业务流程的及时流转所采用的保障措施也具备一定的先进性。展开更多
基金This work was supported by the National Key R&D Program of China(2018YFB0904700).
文摘Hybrid AC/DC distribution networks are promising candidates for future applications due to their rapid advancement in power electronics technology.They use interface converters(IFCs)to link DC and AC distribution networks.However,the networks possess drawbacks with AC voltage and frequency offsets when transferring from grid-tied to islanding modes.To address these problems,this paper proposes a simple but effective strategy based on the reverse droop method.Initially,the power balance equation of the distribution system is derived,which reveals that the cause of voltage and frequency offsets is the mismatch between the IFC output power and the rated load power.Then,the reverse droop control is introduced into the IFC controller.By using a voltage-active power/frequency-reactive power(U-P/f-Q)reverse droop loop,the IFC output power enables adaptive tracking of the rated load power.Therefore,the AC voltage offset and frequency offset are suppressed during the transfer process of operational modes.In addition,the universal parameter design method is discussed based on the stability limitations of the control system and the voltage quality requirements of AC critical loads.Finally,simulation and experimental results clearly validate the proposed control strategy and parameter design method.
文摘根据某公司员工自助服务的需求,针对在ERP系统中没有登录账号,仍然需要实现对员工自己相关人事信息提供自助服务的特殊要求,提出了安全可行的企业门户、EP和ERP三系统的集成方案,满足了单点登录的要求。对系统的架构进行了详细设计,论述了权限的控制方案,并对关键部分的程序进行了设计和代码实现。所设计的员工自助服务系统基于B/S运行模式,采用Web Dynpro for Abap技术开发,程序界面的易操作性接近Windows程序,交互性能在Web程序中具有绝对的优势。此外,系统在确保安全可靠、权限控制到位的前提下,实现了不具备ERP账号的员工对自己在ERP系统中的人事信息维护,而且为了促使业务流程的及时流转所采用的保障措施也具备一定的先进性。
