Multiagent based protection and control in decentralized electric power systems Arshad Saleem Department of Electrical Engineering Technical University of Denmark asa@elektro.dtu.dk Morten Lind Department of Electrical Engineering Technical University of Denmark mli@elektro.dtu.dk Manuela M. Veloso Computer Science Department Carnegie Mellon University veloso@cs.cmu.edu ABSTRACT Electric power systems are going through a major change both in their physical and control structure. A large num- ber of small and geographically dispersed power generation units (e.g., wind turbines, solar cells, plug-in electric cars) are replacing big centralized power plants. This shift has created interesting possibilities for application of intelligent systems such as multiagent systems for control and automa- tion in electric power systems. This paper describes work on designing a multiagent system for protection and control of electric power distribution networks.It demonstrates how explicit modeling of capabilities, states, roles and role tran- sition in agents can capture the control and automation in electric power systems. We present illustrative results from using our proposed schema in realistic simulations. Categories and Subject Descriptors C.3 [Special-purpose and application-based systems]: Process control systems, Real-time and embedded systems. General Terms Experimentation, Reliability, Security Keywords Multiagent systems, power systems control and protection, industrial application 1. INTRODUCTION Distributed generation, decentralized and local control, self organization and autonomy are evident trends of fu- ture’s electric power systems focusing on innovative control architectures like MicroGrids, Virtual Power Plants, Cell based systems, and plug-in electric vehicles. Realization of these concepts requires that power systems should be of distributed nature - consisting of autonomous components that are able to coordinate, communicate, cooperate, adapt to emerging situations and self organize in an intelligent way. Intelligent Software Agents that are autonomous soft- ware entities have most of these capabilities in their design metaphor and have already proved a potential for providing such capabilities in other fields. In this paper we present our work in devising a multiagent system for protection and control of electric power systems with distributed generation (DG). In the attributed mech- anism, intelligent agents represent different components in electric power distribution grid such as distributed genera- tors, electric power loads and relays. The work demonstrates how explicit modeling of capabilities, states, roles, and role transition in agents can apply to the control and automation in electric power systems. We have tested our new schema for application in the specific problem of protection and con- trol of electric power systems. The aim of such a system is to identify the fault location, isolate it from the network and restore supply of power in rest of the system. This prob- lem is of particular interest in a changed scenario of electric power systems because it requires distributed components to communicate and cooperate with each other and perform a collective decision making. The rest of this paper is orga- nized as follows: Section 2 describes the problem background including how the traditional protection systems work and what challenges are brought by the introduction of DGs. Section 3 presents our new mechanism. It presents in de- tail the decision models of different agents involved, formu- lation of the control plan and assignment of roles to specific agents. Section 4 presents results of using the new mechanism in experiments and section 5 concludes the paper. 2. BACKGROUND The objective of a electric power protection system is to identify and isolate faulted section of the electric power net- work[3]. Traditional protection in electric power systems works on the assumption that whenever a fault occurs, fault current flows from the source of power towards the fault location. This assumption holds because of the fact that flow of power has traditionally been unidirectional, i.e., from large power plants to the loads consuming this power. But with the introduction of distributed generators in low volt- age grids, this assumption no more holds; and whenever there is a fault, a multidirectional fault current flows into the network, leaving the traditional protection systems not effective any more. This problem has been illustrated in figure 1. Electric power utilities have been showing great interest in development and acquisition of new mechanisms to cope with this situation. Most common practice among utilities today is to dis- connect a complete feeder containing any DGs whenever a fault occurs in it. This is primarily because of the inability to locate the exact fault location by traditional protection 83