Active damping and harmonic suppression strategy of LCL Grid-tied inverters based on single inverter-side inductor current feedback considering sampling delay

Abstract

Most existing inverter-side active damping methods neglect the 1.5 sampling cycle delay in digital control, degrading stability under weak grids. This paper establishes a virtual equivalent impedance model considering sampling delay and quantitatively derives the relation between grid inductance and optimal damping gain. A single inverter-side inductor current feedback active damping strategy combined with PR and multi-order harmonic compensator (HC) is proposed. The scheme only uses one inverter-side current sensor, eliminates passive damping loss, and widens the stable operation range under weak grids. Simulations demonstrate that the grid current THD of the proposed method is 0.7% lower than that of traditional dual-current feedback schemes, with superior resonance and harmonic suppression capacity.