Research on Active Control Strategy of Grid Connected Harmonic Current Based on Hierarchical Control for Microgrid

Abstract

The micro grid connected in parallel with the traditional droop controlled voltage source inverter is easily affected by the disturbance of the harmonic component of the grid and the dot voltage when the equivalent output impedance is smaller. The total harmonic distortion rate of the grid connected current is raised. An active lifting control strategy for grid connected current power quality based on layered control is proposed. First, the Park transform is used to transform the error voltage between the node and the micro grid AC bus to the rotating coordinate system, and the error voltage compensation loop is added to the two layer control of the original microgrid, and the parallel connection in the compensation loop is used. The multiple resonant controller calculates the error voltage, obtains the harmonic voltage compensation of the underlying voltage source inverter, and uses the proportional integral and resonant hybrid controller based on the rotating coordinate system in the voltage and current inner loop of the inverter to improve the tracking ability of the inverter to the harmonic voltage compensation, and then reduce the micro grid. The harmonic voltage difference between the AC bus and the parallel node reduces the harmonic current injected into the grid by the microgrid. The analysis shows that the control strategy described in this paper can not only reduce the steady-state harmonic current injected into the power grid, but also reduce the harmonic current impact of the grid to the micro grid because of the closing of the grid switch. Finally, the effectiveness of the proposed control strategy is verified by simulation and experiments.