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Self-synchronizing Series-connected Inverters

This paper describes a virtual oscillator based approach to synchronize series-connected single-phase inverters. Each inverter controller includes a digital implementation of a Van der Pol oscillator. When connected in series, such inverters synchronize automatically, without the need for a central controller, communication channels, phase locked loops, or additional hardware such as powerline communication. A linearization-based analysis is used to prove system stability of the synchronized state. The approach is experimentally verified on a 180 W system consisting of three 60 W inverters.