# Smart Inverters for Microgrid Applications: A Review
## Discussion
One measure of autonomy is the ability to control the active and reactive power sharing among them with minimum required communication. The droop control methodsempower this characteristic by controlling each DGs power flow according to its rated values, by mostly using local measurements to minimizing communication requirements. Another aspect that has been considered here is when the working mode of the microgrid changes from islanded to grid-connected or vice versa. Naturally, in that case, the role of most inverters is required to be changed as well, since in islanded mode the inverters are mostly controlled as grid forming, in contrast to a grid-connected mode when they transform to grid feeding or grid supporting modes. These transformations are required to be done automatically, and each of the inverters should be equipped with suitable control structures to make these mode switching accompanied by unavoidable transient responses seamless and smooth. * The last concept covered has been cooperativeness. By definition, this means the smartness that an inverter requires to be able to function in accordance and alongside with other inverters in a grid. All the inverters are required to take some responsibility to regulate and compensate for unbalances and disturbances present in the system. In addition, their operation and behavior should be in alignment with other neighboring components. Otherwise, further disturbances will be introduced to the system. Active, reactive and harmonics current sharing is the most important characteristic fitting in this definition. In contrast to some of the characteristics discussed before the requirement of communication can be sensed for cooperativeness. As a brief summary of the concepts addressed above it can be stated that smartness of an inverter in a microgrid, mostly refers to minimizing communication requirements for its normal operation. However, according to the current literature, this requirement is still present and cannot be omitted altogether. Currently, different communication protocols are used for this application, as well as other M2M communication applications, but each of them have their own drawbacks and are far from perfect. Therefore, there is a broad area of research and development available to fill this gap. One possible idea is the use of the Internet infrastructure which sounds perfect according to its worldwide availability and its great storage and computational potentials based on the cloud concept. Nevertheless, here, the most important consideration is not the internet platform itself. On the contrary, the main aspect is to propose an architecture to connect the components to the cloud. Such an architecture is required to present these qualities:  
* Reliable; no data can be lost or misinterpreted. * Fast, thresholds for delays are very limited. * Secure, immune from unregistered intervention. * Globally available and compatible. * Low energy consumption. * Robustness. * Bidirectional. * Economically feasible, in terms of implementation, operational costs and maintenance. Containing these characteristics, a structure based on a wireless communication protocol can be proposed for inverters communication to improve microgrids performance and control. In spite of that, it should always be remembered that every communication structure, no matter how carefully engineered and well established it is, still contain deficiencies such as delays, by nature. Therefore, the research and development of control structures centered on the goal of reducing the communication requirement should continue further more. **Author Contributions:** [PERSON] carried out the literature review and wrote the paper; [PERSON] supervised and provided critical reviews. [PERSON] and [PERSON] coordinated and reviewed the final work. **Funding:** This research was funded by the Aalborg University Talent Programme 2016 with the research project: The Energy Internet-Integrating Internet of Things into the Smart Grid.