Partial contraction analysis for droop controlled inverters

Droop control techniques are widely used in power systems for the synchronization of inverters connected to the grid. The amplitude and the frequency of the voltage generated by the inverter are determined by local measurements of active and reactive powers. It has been shown in the literature that for some values of the droop control parameters the system can exhibit an unstable behavior. In this paper the partial contraction theory is exploited to analyze conditions for the closeness of solutions between the dynamic model of the droop controlled inverter connected to the grid and a suitable reduced-order system, whose stability can be simpler analyzed. The numerical simulations demonstrate the effectiveness of the proposed technique also for large signal operating conditions.