State Space Model for a Droop Control Strategy with Fault Ride-Through in UPS Parallel Inverters

Abstract

A droop control strategy with fault ride-through capability to overcome overload and short circuit operation in UPS applications is proposed in this work. This strategy is based on multiple resonant controllers designed to comply with performance specifications given by IEC62040-3. An state-space model is proposed to explore the stability limits of the parallel-connected inverters and design the virtual impedance loop. Experimental results obtained using two parallel-connected UPS inverters are presented to validate the proposal.