S Loop 3 Machinery C WH A Fisk Substation (12.47 kV) Facilities Figure 2. The location of the Keating Nanogrid in the IIT Microgrid. N Vandercook I B I E E E E l e c t r i f i c ati o n M agaz ine / j un e 2017 Vandercook II D C SB KH Keating Nanogrid Loop 1 E Eng1 E LS Bailey D Loop 2 C B Carman A A AM HH B PH MTCC ComEd Main MM Loop 5 F E Library SH Loop 4 FF North South EE Pershing Substation (12.47 kV) B A A A D CR SSV PKP SPE DTD A A BB C C D D Farr Kappa ASA Grad Lewis Fowler East Gunsaulus Cunningham ComEd AA ERB E LSR LS D D B C ASP PKS TRI TN Power Plant Plant Heat Plant BB TBC Loop 6 C C TS TC T Parking Loop 7 C C D D Wind Turbine Energy Storage Gas Turbine Solar Panel Charging Station Tower 38 with storage devices to serve its building loads. Figure 3 shows its complete architecture. This nanogrid is a hybrid of an ac and dc power distribution system, as opposed to the more common nanogrid architecture based on dc technologies alone. Two sets of rooftop photovoltaic (PV) arrays that harvest solar energy are connected to ac and dc subsystems separately. Batteries that store dc power are utilized in each subsystem to level off the variability in the output power of PV arrays. AC loads (e.g., swimming pool pump) and dc loads (e.g., light-emitting diode [LED] lighting) are included in the respective ac and dc subsystems. Accordingly, the dc power generated by PV arrays can directly serve dc loads in the dc subsystem with a simple and cost-efficient structure that will not require the traditional (dc-ac and then ac-dc) conversion. The dc bus features a nominal 48 Vdc, and the ac bus is configured in a four-wire, three-phase wye connection with the nominal singlephase voltage (120 Vac). The ac subsystem is connected to the rest of the IIT Microgrid, allowing t h e Ke a t i n g N a n o g r i d t o exchange power with the IIT Microgrid when there is a power imbalance in the nanogrid. Power converters will manipulate voltages to interface generation sources, energy storage, and loads to the Keating Nanogrid. DC-dc buck converters interface one set of PV arrays with the dc subsystem because PV arrays produce a higher dc voltage than the operating voltage of the dc subsystem. The other set of PV arrays is connected to the ac subsystem via dc-ac inverters. The ac and dc buses are interlinked through bidirectional ac-dc converters that transfer power between the two subsystems and regulate the bus voltage magnitudes. Since each