Research On Real-Time Communication Of Ethernet-based Substation

At present, there are some problems existing in the power system, for example the level of digitalization and informatization is low, resource can't be shared and utilized fully, and so on. The issue of IEC 61850 and mature of Ethernet technology bring a chance and innovation. IEC 61850 provides the comprehensive and uniform standards for all of substation and prescribes Ethernet as the basic communication network of substation. But Ethernet, which is originally designed for commercial and office areas, can not meet the real-time requirement of the substation communication, especially when the system runs with the heavy load. Aiming to the problem, this paper researches the network implementation of substation communication based on Ethernet, which can improve the real-time performance of the substation communication. The significant achievements are as follows:(1) Based on analyzing the information flows of substation, this paper logically divides the entire substation network into many separate broadcasting domains and designs the network topology for substation using VLAN (Virtual Local Area Network) and layer 3 switch. The comparison with the other two network topologies indicates that the designed topology can improve the real-time and security performance and reach the highest cost performance. The simulation results using OPENT also prove that the VLAN is an advanced technology.(2) Based on analyzing the principles of the VLAN protocol (IEEE 802.1Q) and the priority protocol (IEEE 802.1P) which are realized inside the switch currently, this paper proposes the method implementing the two protocols inside IED (Intelligent Electronic Device). In the proposed method, two priority mechanisms running in the IED and the switch are taken into account together, which can decrease the overhead. The proposed method allows that the IED set the different priorities according to the different messages instead of the current fact that the same IED can only set a priority to its all messages. It meets the requirement of composite development of IED in the digital substation. Take the messages in process level for example, the paper simulates the two implementation method using OPNET. The simulation results indicate that the proposed method can enhance the real-time performance of substation communication, especially under heavy load.(3)At present, most of research on the publish/subscribe(P/S) communication model recommended by IEC 61850 pays little attention to the particularity of substation communication.To improve the real-time performance of substation communication, a P/S communication model based on GMRP (GARP Multicast Registration Protocol) running in the link layer is designed. This model is proposed by analyzing current multicast technologies and can suit for the special situation that the GOOSE message and the SAV message are directly mapped into the link layer from the presentation layer in IEC 61850. Functions of its modules are presented. Moreover, an illustration of system configuration, subscribe and publish process when sending the GOOSE message is provided to detail the work process of this model. And then the designed P/S model is realized in the embedded system, based on the analysis of GMRP protocol adequately. The analyses of many typical program implementation processes prove that the designed model is feasible completely. Finally, the comparison among three transmission forms of P/S (unicast, broadcast and GMRP multicast), which is based on analysis of experimental data, indicates that this model can not only support the real-time requirements of substation communication but also enhance the real-time performance under heavy traffic.