**6. Conclusions**

The results presented in this paper show that the droop control relationship for a source in a DC microgrid can be optimized to meet a given objective. An example microgrid was simulated and demonstrated through HIL, and the results show that a droop control relationship can be chosen to allow the power supplied by a source to match the power available from the solar PV resource.

This control method retains the advantages of traditional droop control, and does not require a communication link between the system components. It also allows all of the power available from solar PV resource to be utilized, which is an improvement over traditional droop control, and over high dimension droop control using a plane. The droop control surface is optimized for general operation of the system—it is not necessary to know the expected solar irradiance and load profiles in order to determine the surface shape.

**Author Contributions:** Conceptualization, K.J.B., M.D.C., W.W.W. and G.G.P.; Formal analysis, K.J.B.; Investigation, K.J.B. and M.D.C.; Methodology, K.J.B., M.D.C., W.W.W. and G.G.P.; Supervision, W.W.W.; Writing—original draft, K.J.B.; Writing—review & editing, M.D.C., W.W.W. and G.G.P.

**Funding:** This work was supported by a National Science Foundation Graduate Research Fellowship (DGE-1051031), and the Army Research Laboratory (W911NF-13-2-0024).

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