Finite-gain repetitive controller for harmonic sharing improvement in a VSM microgrid

Abstract

Electronic power interfaces are commonly used for renewable energy integration in microgrids and their control as Virtual Synchronous Machines (VSMs) represents an attractive alternative to typical control configurations. This control technique has many advantages, but several issues still need to be properly addressed, including power quality and harmonic current sharing. In this paper, a method to deal with current harmonic distribution in microgrids based on VSMs is introduced. A Finite-Gain Repetitive Controller (FGRC) is added to the main control system of a current-controlled VSM and it is shown that the use of this alternative controller allows current harmonics to be shared between the Distributed Generators (DGs) feeding a non-linear load. Stability, transient performance, and performance under frequency variations are studied analytically. All control system improvements were tested on a prototype microgrid consisting of two 15 kVA VSMs and a non-linear load connected via electrical distribution lines. Enviado para su evaluación al IEEE Transactions on Smart Grids (August 2018) .