## 3 Energy Management System in Islanded Microgrids under Communication Constraints
### Energy Hybrid Method with Different Sleep Modes Depths  
Sleep modes were proposed as a technology to achieve energy efficient consumption in wireless access networks [27]. For the improvement and optimization of the grid operation time, new savings policies are developed in this research to achieve a better overall performance.  
The proposed modifications refer to the communication load aiming to optimize and maximize the efficient energy operation. The communication network, considered before as a priority load, now  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Operation Mode** & **Priority** & **Supplied Loads** \\ \hline \multirow{3}{*}{Critical} & \multirow{3}{*}{High} & Health Services \\  & & Transportation \\  & & Facilities \\ \hline \multirow{3}{*}{Emergency} & \multirow{3}{*}{Medium} & Industrial \\  & & Commercial \\ \cline{1-1}  & & Health Services \\ \cline{1-1}  & & Transportation Facilities \\ \hline \multirow{3}{*}{Normal} & \multirow{3}{*}{Low} & Residential \\  & & Industrial \\ \cline{1-1}  & & Commercial \\ \cline{1-1}  & & Health Services \\ \cline{1-1}  & & Transportation \\ \cline{1-1}  & & Facilities \\ \hline \hline \end{tabular}
\end{table}
Table 2: Loads scheduled according to microgrid operation state.  
assumes different status according to the microgrid state operation. Instead of being active all the time, the MGCC controls grid operation sending its information to the EMS, and it automatically activates or deactivates the communication network when necessary. These controls rules are based on sleep mode techniques. Different deepness policies are considered here to optimize the BS power consumption and improve microgrid operation. These policies are implemented in the EMS and are summarized in Table 3.  
Table 3 shows how the EMS control takes its action. An example of the manager control can be described as: if the controller enters the emergency mode, low priority loads are switched off, and the communication network in charge for that group is deactivated. While in medium priority groups, the BSs are forced to enter in long sleep mode and high priority groups in soft sleep mode.  
In soft sleep mode, the base station power amplifier turns off, and in long sleep mode, most devices are completely turned off, such as the power amplifier, air cooling, signal processing, and baseband processing, with only a few devices remaining turned on for network synchronization. In the deactivated mode, the whole base station is turned off. The off time periods will impact the communication system performance affecting the microgrid reliability; for this sake, the grid reliability is evaluated. Table 4 illustrates the sleep mode deepness features.  
In Table 4, variables like wake-up time, affected functionalities, and latency trade-off are described for each sleep mode deepness. Analyzing Table 4, the trade-off between applying different sleep modes deepness and the impact in communication applications is evident. For instance, using a soft sleep mode into BS affects low latency applications, e.g. protection systems, as the BS wake up time is longer than the time to take the protection action.