Harmonic Power Sharing Control Strategy of Microgrid Dominated by Grid-Forming and Grid-Following Inverters Under Nonlinear Loads

Harmonic currents will be generated due to the connection of nonlinear loads in the microgrid. Besides, the differences in line impedance can result in the unreasonable distribution of harmonic power of the inverter, even causing the inverter to be overloaded. Based on virtual harmonic impedance and harmonic droop control, this paper proposes a harmonic power proportional distribution strategy applicable to the coordinated control of grid-forming (GFM) and grid-following (GFL) inverters. Firstly, the dual second-order generalized integrator (DSOGI) is used to extract the fundamental and main low-order harmonic components in the output current and voltage. Secondly, the instantaneous value of the harmonic power is calculated and information interaction is established with other inverters. Based on the distribution error between each harmonic power, the voltage compensation amounts are finally obtained through the Proportional-Integral (PI) controller. After being accumulated with the harmonic voltage reference values obtained by the harmonic droop, they are respectively sent to the voltage loop of the GFM and the inverse droop control loop of the GFL to realize the compensation of the harmonic voltage drops of each order. Finally, the correctness and effectiveness of the proposed strategy are verified in MATLAB / Simulink.