June-Hee Lee and Kyo-Beum Lee, "Optimal Phase Shifted Method to Reduce Current Ripples for Parallel Grid-connected Voltage Source Inverter under Unequal DC-link Voltages," in Proc. ECCE Conf., Oct. 2017, pp. 4589–4594. > Paper

This paper proposes optimal switching period phase-shifted method for slave inverter to reduce grid current ripples in synchronized

two parallel three-phase grid-connected voltage-source inverters (VSI). In parallel operation, a 180 degree phase shifted method

generally takes of advantage of reducing grid current ripples in same DC-link voltage for each grid-connected VSI. However, in case

of unequal DC-link voltage, the grid current ripples have increased using a 180 degree phase shifted method because a dwelling

time between two inverters is changed by the different modulation index (MI) of each inverter. To overcome these drawbacks, the

proposed method applies the phase angle for reducing grid current ripples to the slave inverter through the calculation of dwelling

time. Using the proposed method, it is possible to increase the quality of grid current without any additional device or re-designing

of the filter. The performances of the proposed phase-shifted method are studied via PSIM simulation.