Research On A Micro-grid Control System Based On EtherCAT

In recent years, the worldwide natural disasters and continuous power accidentshave fully exposed the vulnerability of large power. Distributed generation powergeneration is flexible, and can be compatible with the environment, but for largepower grid, the distributed power generation system is not controllable. In order tocoordinate the contradiction between the large grid and distributed power, theconcept of micro-grid is proposed.The penetration of micro-grid has increased rapidly and gradually reachedsignificant levels. But some problems concerning micro-grid still need to be solved.One of these issues is control strategies which are mainly determined based on theadopted distributed generation technologies, load requirements, and the expectedoperation scenarios. And another issue is the communication. This thesis takes aproject for example, specify describing these two aspects contents.First, after analyzing the micro-grid system structure and internal componentsproperties, an optimized hierarchical structure is proposed in order to make thecontrol objects more clearly. Secondly, the micro-grid system has different operatingcharacteristics when it is in different mode. So U/f control method is used inisolated mode and P/Q control method is adopted in combine mode for designingcontrol strategies, what is more, the power balance calculation is added to ensure thestable operation of the grid. The micro-grid control strategy is based on the localinformation collection and exchange, therefore, a fast and reliable communicationmethod is the basis factor for ensure the micro-grid runs normally, By comparing thecurrent popular industrial Ethernet technology, a fast EtherCAT industrial Ethernettechnology is chased as the micro-grid control system communication platform. Inaddition, according to the EtherCAT communication theory, EtherCAT should workin master-slave mode. Beckhoff’s TwinCAT is taken for master station, EtherCATASIC ET1100is as the slave station, and AT89S52is used for the application layercommunication. The data from underlying devices can be transformed to the masterstation through this communication platform.Finally, the experiments have verified that the EtherCAT communicationstechnology is real-time and reliability. Based on the technology, the appropriatecontrol strategies is adopted to complete the switch experiments for micro-grid.Method described in this article enables micro-grid system switch smoothly within 300ms. This experiment proved that the design of micro-grid control strategy isreasonable. what is more, it shows that EtherCAT communication can greatlyimprove the micro-grid system reliability and stability.by comparing with theCAN-bus, EtherNET and other existing communications technology.