| Higher technology requirements are put forward to relay protection and security and stability control system with the development of interconnecting among large-scale power systems in last few years. The analysis from several blackouts of power systems overseas shows that traditional backup protections are prone to misoperate under exceptional running status by the disturbance of system, causing the cascade tripping. With the development of wide-area communication network (WAN) and synchronization measuring equipment based on GPS (Global Positioning System), novel wide-area backup protection (WABP) systems based on wide-area communication network and synchronized phasor measurement have been studied recently. The wide-area backup protection systems can obtain wide-area protection information to be aware of actual running status of power systems. The wide-area backup protection systems using agent technology are studied to solve the problem of traditional relays' working independently. Some basic researcheson WABP multi-agent system have been made, but there are still some problems needed to be studied, such as the architecture of WABP multi-agent system based on IP communication, the corporative strategies and the simulation system for checking up the running performance of WABP multi-agent system. Petri network, as a strict formalization modeling and analysis tool, may be combined with agent to construct the model and analyze the behaviors of WABP multi-agent system.The research situation about WABP algorithms are introduced firstly. The principles of agent and multi-agent are expatiated, as well as the applications of agent on power system and their enlightenment for the study of WABP. The studies of communication simulation modeling on WABP and Petri network applications on power system are also reviewed. The objectives and researched content are proposed.According to the features of WABP system, the working mechanisms of WABP agent are studied, which include the architecture of WABP multi-agent system, internal multi-layer model of protection agent, the state transferring based on finite state machine, equal negotiation mode and robust measures. The information model and wide-area communication model of wide-area backup protection agent based on IEC61850 are proposed.The simulation system for WABP multi-agent system is studied, which includes the simulating design of agent, the models of power system and SDH wide-area communication system and the setting of some kinds of faults. The visual simulation results and exact communication delays can be obtained from the somlation system. The testing experiments and their analyses illuminate that the simulation model is correct and the performance of WABP multi-agent system can be checked up well.The formalization modeling for WABP multi-agent system combined the agent with Petri net is studied. The improved agent-oriented Petri net is put forward. The WABP agent-oriented elementary Petri net (AOEPN) is constructed. According to equal negotiation mode, the agent-oriented colored Petri net (AOCPN) is studied, using the concept of colored Petri net. The respective WABP-AOCPN is also constructed. The dynamic behaviors of WABP agents under some fault situations can be reasoned in the testing examples; the WABP algorithm can be tested as well. The definition and theorem of equal substitution of dynamic behaviors in multi-agent systems are proposed, as well as the operation method. The equal substitution processes of multi-agent systems in WABP-AOCPN are analyzed, which illuminate that the method of equal substitution is correct.The researches which include the working mechanisms of protection agent, simulation modeling and oriented-agent Petri net based formalization modeling for WABP multi-agent system are studied systematically in this paper. As a result, an information model for WABP system is constructed. These works give a well-grounded information support for future study.
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