## 2 Power and Energy Systems Simulation
### Simulation of Heterogeneous Systems  
In the literature, it is possible to find only a few solutions capable of enabling heterogeneous systems' interoperability, in the area of power and energy systems. For instance, the Electric Power and Communication Synchronizing Simulator (EPOCHS) [47] is a pioneering MAS that combines the results of several simulators by using realistic scenarios, to solve network communication problems in the laboratory, avoiding potential costs and damages. Another similar tool is the Global Event-Driven Co-Simulation framework (GECO) [48], which aims to model and simulate the monitoring, protection and control schemes of the power systems and communication network. For these two tools, although they allow the co-simulation of several tools, their area of operation is restricted to power systems and communication network. The Mosaik system [49; 50] aims to allow the simulation of heterogeneous components of the SG, providing different models that allow one to simulate producers, consumers, prosumers, electric vehicles and other elements of the network. This system addresses many of the challenges of interoperability in the area and has a similar proposal to TOOCC. However, similarly to the previous tools, it also does not have an extended domain as is desired, since it focuses on the simulation of scenarios related to SG. Furthermore, according to the authors' understanding, Mosaik is only able to perform static simulations, which were previously configured and programmed. If it is intended to add a new system to the simulation, it must be restructured, and it is necessary to carry out new configuration programming work.  
Although there are several MAS dedicated to the study of the energy sector, they are oriented towards solving problems in specific domains, for private use, limited to systems already incorporated (do not allow the connection to external systems), do not take advantage of the formal exchange of knowledge, or only support interoperability in already configured static simulations. When these systems are able to communicate with each other and to exchange knowledge, by combining their individual capacities, it is possible to solve problems that cover more comprehensive and complex domains in a more flexible way. Thus, the interoperability between systems allows the simulation of scenarios that support the growing complexity of this area, where its stakeholders are in a constant process of interaction and negotiation with each other, and there is a need for careful management of resources. The multi-agent technology has particularities that facilitate the increase of interoperability between systems [51]. However, the interoperability among systems is highly complex due to their heterogeneity. Since they are distinct tools, they may also have different domains, concept definitions, programming languages, temporal resolutions, event handling and others. It is necessary to establish a mechanism for communication between these systems, which initially would be incompatible. For MAS to be able to communicate with each other in order to overcome their individual limitations, it is necessary to use mechanisms that allow the sharing of information and knowledge that at the same time provides the necessary flexibility to deal with the execution of several processes at the same time. For this purpose, standard communication formats and protocols must exist, which ensure that the involved entities assign the same meaning to different terms [52; 53].