# Hybrid Energy Routing Approach for Energy Internet
## 2 Implementation of Energy Internet with Energy Routers
### Energy Router Architecture and Functions  
ER is regarded as the primary networking unit for the implementation of the EI. It is proposed to achieve a better utilization of renewable energy sources, with an efficient transmission of energy flows. The ER has comprehensive functions such as an energy exchange, communication and energy management [35]. The study of ERs is in its preliminary stage at present, and various researchers have suggested different ER designs, such as the works in [20; 35; 36; 37]. The common functionalities between the different suggested designs are: the integration of renewable energy sources; the control of power and communication flows; and the regulation of power quality and voltage/frequency conversion.  
The first design of ER was based on solid-state transformers (SSTs) and proposed by The Future Renewable Electric Energy Delivery and Management (FREEDM) [38]. As shown in Figure 3, the SST-based ER is composed of an energy management module and power electronic conversion module SST [6; 37]. First, the energy management modules  
Figure 2: Energy Internet model.  
can realize the communication, power routing and management using power flow, while the power electronic conversion module (SST) can convert multiple energy forms and voltage levels, as well as compensate for reactive power. It has a three-stage topology: the high-voltage AC/DC stage, the middle DC/DC stage and the low-voltage DC/AC inverter stage. The high-voltage AC/DC stage rectifies the power frequency from High Voltage Alternating Current (HVAC) to Medium Voltage Direct Current (MVDC), the bidirectional middle DC/DC stage transforms the the MVDC to a regulated Low Voltage Direct Current (LVDC), while the low-voltage DC/AC inverters generate a LVAC. The SST provides multiple plug-and-play interfaces that allow loads, storage systems, renewable energy, micro-grids (MGs), utility grid and other ERs to be connected. Every interface can connect various energy systems or devices, provided that the total power connected to the interface does not surpass its capacity limits.  
Using ER controlled by information can improve the efficiency of energy transmission and energy allocation. For an efficient energy management, these ERs need to be equipped with efficient dynamic energy routing protocols to respond to changes in energy information, system topology and the regular connection/disconnection of the system devices. For this, in our proposed network architecture, we assume that every ER broadcasts its energy information, its connections (ERs, devices and power links) with their energy information to all other ERs in the system. Whenever the system topology or energy information change, the connected ER broadcasts this information to all the others. Thus, each ER accumulates all the necessary energy information and topology of power system and stores them in two different energy information tables, as shown in Tables 2 and 3. These tables represent the energy information of the proposed EI in Figure 1 where \(eff\) represents the power conversion efficiency of the corresponding ER converter.  
Figure 3: SST-based ER architecture.