dc Sources dc Loads dc Loads 24 Vdc/48 Vdc/Other DS DS Battery 760 Vdc 380 Vdc 380 Vdc ARDA dc/dc Energy Converters DS dc Loads 380 Vdc/760 Vdc ARDA dc/dc Battery Converters DM DS Energy Converter DS DS Grid-Tie Inverter Inverter Uninterruptible ac Loads ac Source ac Sources ac Grid Legend: DM -ARDA Distributed Master Controller Interruptible ac Loads Uninterruptible ac Loads ac Loads DS -ARDA Distributed Slave Controller Figure 5. The ARDA dc microgrid concept. Vdc sp + (From Sustaining Function Algorithm) - dc Bus Volt Controller ESS Power Command + - ESS Power Controller PESS Converter Plant (S) dc Bus Plant (S) IESS VESS dc Bus Voltage Figure 6. A block diagram for regulating function in energy storage. in the system so that the components are not pushed to extreme operating conditions where they cannot respond to changes in demand or generation. Examples of sustaining functions include battery- and energymanagement algorithms. The power sources and loads use the average measured dc bus voltage to gain information about what the energy manager is commanding 42 I E E E E l e c t r i f i c ati o n M agaz ine / j un e 2016 and respond following internal algorithms to change their power generated or consumed appropriately. Since all the components are connected to the dc bus and the operation of the microgrid depends on it, the dc-busbased communication has a high reliability and a low cost. It makes sense to locate sustaining functions in the energy-storage devices since they have all the