Experimental Analysis of Grid-Forming Frequency Control Strategies for Load Sharing in Low Voltage Islanded Microgrids

The increasing penetration of distributed generation units in the distribution grid may lead locally to a generation surplus. Along with the presence of inverter-interfaced battery storages (IIBS) with grid-forming capability an islanded microgrid operation becomes possible. In Germany distributed generation units have to adjust their active power infeed in case of deviations from the nominal frequency. This behavior opens the possibility to control the active power balance in islanded microgrids using frequency-active power control strategies. In this paper, with the aim of a prolonged temporary islanded microgrid operation, two frequency control strategies-f-P characteristic and iterative control - are implemented and analyzed for an IIBS in an islanded microgrid in laboratory scale. The results show that the f-P characteristic reaches a stable operation faster, but cannot reduce the active power output of the grid-forming unit to zero in comparison with the iterative control.