# Internet of Things for Modern Energy Systems: State-of-the-Art, Challenges, and Open Issues
## 2 Key Features in the Energy Internet
### Energy Management Systems in IoT framework  
One of the main motivations for developing integrated energy systems and what is called energy internet is to manage energy in an optimal way. To make it clear, assume an IoT-based energy system including Electric Vehicles (EVs) [75]. In this attempt, each EV tries to maximize its objective (paying less money), while an energy retailer tries to maximize its own objective (earning more money). Both sides act smart and try to maximize their own profit, which in this case their objective is in conflict. A solution to find an optimum point, in which both sides satisfy with their profit, is to hire IoT infrastructure (e.g., WiFi or WiMAX systems and sensors to collect information from EVs). To do so, many efforts have been done to improve EMS considering different objectives such as reducing energy losses, minimizing the costs or even some technical objectives like minimizingvoltage deviation [33; 76; 77]. In the new paradigm of energy systems, customers of energy may produce and inject energy (also known as prosumers) to an upper level, which may be a distribution system. The role of prosumers energy management systems is highlighted in the literature as their role in peak demand management [78]. In this regard, not only electrical systems should be reconfigured, but also communication systems have to change fundamentally. Moreover, prosumers can not only exchange energy, but also data with the system using bi-directional connections [76]. In this regard, control objectives and settings of the EMSs have to be reconfigured as well. In [77], a dynamic control strategy is introduced and limitations of the communication system are considered as a drawback that makes challenges in a fast response of the designed control system. On the other hand, with the growing trend in the use of internet in smart buildings and cities, it is a must to design an energy-efficient, cost-effective, secure, and reliable IoT-based platform for energy management purposes [79]. IoT solutions for EMS are developed in regards of either reduce or shift energy consumption by applying incentive offers or optimize utilization of energy sources. Generally, there are two types of energy/power management strategies, used in smart energy applications, named as passive schemes based on self-autonomy, and interactive schemes, based on information sharing mechanisms. In a given interactive power/energy management system (IP/EMS), local and global system information (such as line currents, nodal voltages, frequency and powers) is communicated in the system and exchanged between corresponding nodes in order to determine operation point of each controllable DG or consumption unit. These strategies also benefit from a sort of intelligence in the integration of the computing and communications technologies, which help them to define and develop the communication structure based on the computation burden of each node and other related system's objectives and constraints. In this regard, three different communication schemes can be realized for an IP/EMS: centralized, decentralized, and hybrid. In centralized EMS, a centralized decision-maker is used to find the optimum point for the objective of the system based on the information of every component [80; 81]. In this manner, mostly energy sources and end-users have no authority to manage the energy unless the decision maker (centralized controller) decide for an action. In [80], a centralized EMS using model predictive control is designed for isolated MGs. In this regard, lack or loss of information can significantly affect the mentioned method. In centralized control scheme, not only a centralized controller controls system features like frequency and voltage, but also it is responsible for some challenges like harmonic mitigation [81]. In a decentralized EMS, every player in the system decides individually to optimally manage its energy production/consumption level [82; 83]. A decentralized system is more reliable, as every sub-system decide independently.