**5. Conclusions**

In this paper, a hierarchical control has been proposed for multiple ESs tied to a microgrid; it relies on the droop control as secondary control and on the power decoupling control as primary control. The issues of the existing solutions for operation of multiple ESs have been analyzed first, referring to the version-2 ES as the power compensation device. Proper setting of the reference value for the PCC voltages of the nodes with a tied ES has been done by the droop control technique, which has been instrumental in obtaining the coordinated operation of multiple ESs. In order to ge<sup>t</sup> fast and smooth ES dynamics, the performance of the power decoupling control has been improved by implementing an inner, closed-loop control of the ES output voltage, toughened with an active damping obtained by feedbacking the current flow in the ES output capacitor. To verify the effectiveness of the proposed hierarchical control together with the novel algorithms developed for its implementation, simulations are conducted to test the operation of single and multiple ESs. They have demonstrated that both node voltage and microgrid frequency are accurately and promptly regulated by the proposed control of multiple ESs with the proposed control. It should be noted that *vG* is difficult to measure at PCC side due to the transmission line in between. Besides, the battery managemen<sup>t</sup> system on the ES is not focused either in this paper. Both aspects will be part of future work.

**Author Contributions:** Conceptualization, Q.W. and W.Z.; methodology, Q.W.; software, W.Z.; validation, W.Z., Q.W.; formal analysis, F.D.; investigation, W.Z.; resources, Q.W.; data curation, Q.W.; writing—original draft preparation, W.Z., Q.W.; writing—review and editing, Q.W., G.B.; visualization, F.D.; supervision, M.C.; project administration, Q.W.; funding acquisition, Q.W.

**Funding:** This work was supported by the Natural Science Foundation of Jiangsu Province under project BK20170675, and by the National Natural Science Foundation of China under project 51877040.

**Acknowledgments:** In this section you can acknowledge any support given which is not covered by the author contribution or funding sections. This may include administrative and technical support, or donations in kind (e.g., materials used for experiments).

**Conflicts of Interest:** The authors declare no conflict of interest.
