# Internet of Things for Modern Energy Systems: State-of-the-Art, Challenges, and Open Issues
## 1 Introduction  
One of the main challenges in reliable operation and control of a given system is managing information produced by its components. This includes data collecting, transmitting, and processing. By introducing more useful information to data processing systems, more appropriate decision can be made based on the knowledge pool. The new concept of the Internet of Things (IoT) is introduced for systems in which the components are connected via the Internet [1]. This system of interrelated physical systems and computing devices introduces many opportunities as every object in the system can communicate with related objects of the system by using two-way communications. Specifically talking about energy systems, IoT could offer advanced connectivity of heterogeneous objects to form a single system [2]. However, there are some challenges in seamless integration of different domains once various services have to be offered beyond machine-to-machine (M2M) communications. The situation gets worse as a number of systems such as power systems, control systems, and communication systems are integrated into a bigger system while each is following its unique set of objectives. Although a great effort can be found in the literature about every issue of energy systems, integration of subsystems is a hot research topic at this time [1; 2; 3]. In this regard, a deep perception of every aspect of energy systems and their rightful assortment is of high importance. Figure 1 shows a categorization of energy systems in a general aspect. As can be seen, compared to the traditional energy systems, modern energy systems are designed in a full grid sensor layout with automatic monitoring and recovery capabilities, which enable distributed energy generation. This architecture becomes bolder as Microgrids (MGs) are introduced into energy systems. MGs are the integration of some distributed generations (DGs) and loads that are capable of running in grid-connected or island mode [4]. MGs are defined in many ways, considering who are dealing with and how they are using it. For instance, a mobile phone can be defined as an MG, while a wind farm can be defined in the same respect. With this in mind, there is no standard mentioning directlyMGs, while there are some standards such as IEC 61850, which define DGs as key players [5]. Based on these standards, many efforts about stability, reliability, control, etc. on MGs can be found in the literature [4; 6]. A general review of many features such as reliability, resiliency, and Power Quality (PQ) in some aspects like protection control, communications, and economics of MGs can be found in [7]. A great effort has been done on IEC/ISO 62264 regarding communication structure of MGs represented in a five-level architecture. In this hierarchical structure, in which higher level has a priority to the lower one, a common standard for communication of Distribution Energy Resources (DERs) is considered. On the other hand, in IoT-enabled energy systems, communication infrastructure is a key part that has to be well-established at each level of the system starting from a wide-area network down to a building unit [8; 9]. In addition, to design a communication system for a given energy system, there are some factors like system size, installation and maintenance costs, flexibility of the system for future expansions, etc., which need to be considered [8]. More importantly, security of the system should be considered in every step of designing a communication system [10]. Based on what is needed from the system, different communication technologies may also be used in the system. For example, when a wired system like Power Line Carrier (PLC) is accessible, it is logical to use this facility. In contrast, for using synchronous communication in large power systems, wireless networks such as Wide Area Measurement Systems (WAMS) will be a good choice [9; 11]. With all this in mind, to study an energy system properly, a good comprehension of the system's components is not a recommendation, but a requirement.