Virtual Impedance-based Grid Synchronization for Converters Connected Through Long Cables

Abstract

This paper proposes a synchronization scheme for grid-connected Voltage Source Inverters (VSI) without physical interface inductors, voltage sensing or conventional PLL algorithms. Especially, issues with converters connected trough long cables are addressed. These cables present non-negligible LC characteristics that can lead to resonance peaks degrading current or voltage waveforms. A virtual impedance is used as grid coupling element, providing a virtualized synchronization point within software using only already available current-sensor information. Also, virtual resistance is used to actively dampen resonance peaks caused by cable characteristics. Theoretical analysis and simulation results are presented to verify the proposed strategy.