I E E E E l e c t r i f i c ati o n M agaz ine / MARCH 2014 Supervisory Control Iin + - GPFC (s ) δvt Voltage Secondary Control ∗ vMG i Gsec (s ) δvs + - vMGs Iout Power Flow Control MGi + + αi m Participation Factor αi 1 Figure 9. The hierarchical control structure for multibus dc microgrids. ∗ Iout, 3 ∗ Iout, 2 ∗ Iout, 1 - + ∗ vMG i - + ∗ vMG i + Communication Rdm Droop Control + Vref - MGi + 1 - Primary Control Vdcm Voltage Control Current Control - + iref Gc (s ) Gv (s ) Rd 1 Droop Control vref Primary Control Vdc1 Voltage Control Current Control - iref + Gv (s ) Gc (s ) Communication MGi -1 PWM Generator PWM Generator dc−dc dc Source m dc−dc dc Source 1 io Vdcm io Vdc1 MGi Bus dc−dc 380 Vdc Buses dc−dc tiei, i -1 dc−dc tiei, i +1 64 To LowVoltage Bus To LowVoltage Bus To LowVoltage Bus