Research on the Power Sharing of the Parallel Inverters without Control Interconnection Basing on Droop Characteristic

In the distributed AC supply system without control interconnection, the parameters unbalance because of nonuniformity between the unit inverters is inevitable. The supplier unit is difficult to share power properly. Based on the digital control inverter with instantaneous capacitor-current feedback, the affection to power sharing of the filter inductance and equivalent line impedance are analyzed. Theory and simulation prove that the active power can be shared averagely, the phase-shift between the units changes along with the load variation, the reactive power cannot be shared properly when the parameters are unbalanced, the sharing effect is affected by the load variation. Basing on the analysis, the strategy to reduce the unbalance of the power sharing is presented