Finite-gain-current repetitive controller for synchronverters with harmonic-sharing capabilities

Power electronics interfaces are commonly used for renewable energy integration in microgrids and their control as synchronverters represents an alternative to typical control configurations. This control technique introduces many advantages, but several issues need to be properly addressed including power quality and harmonic current sharing. In this paper, a method to deal with the current harmonics distribution in microgrids based on synchronverters is introduced. A Finite-Gain Repetitive Controller (FRC) is added to the control system of a current-controlled synchronverter. It is shown that the use of this alternative controller allows current harmonics to be shared between the Ditributed Generators (DGs) feeding a non-linear load. In addition, it is shown that the FRC represents a robust solution against the frequency variations typically occurring in microgrids. All the harmonic sharing improvements of the control system are tested on a prototype microgrid consisting of two 15 kVA synchronverters and a non-linear load connected via electrical distribution lines.