Stability of voltage and frequency control in distributed generation based on parallel-connected converters feeding constant power loads

In this paper stability and dynamic properties of voltage and frequency droop control of power electronic converters are investigated for a distributed generation system. Droop control is utilized to share active and reactive power among the source converters. The voltage and frequency controllers are designed so that stand-alone converter operation feeding constant power loads performs satisfactory. These controllers are adapted to mimic the behaviour of present rotating generators connected directly to the power system, for seam-less transfer between island and grid-connected modes of operation. Small-signal and switch-mode, time-domain simulation results of a three-converter distributed generation system facilitating stand-alone operation verify the operation. Experimental results of a three-converter stand-alone system are also included for verification.