Real-time identification method of power grid impedance based on intermittent harmonic injection

This paper proposes a real-time identification method of power grid impedance based on intermittent harmonic injection. This method intermittently injects harmonic current and uses Fourier transform to extract the harmonic amplitudes and phases of the common coupling point (PCC) voltage and current, achieving high-precision impedance detection while ensuring that the harmonic distortion rate meets the grid connection requirements. The detection accuracy of the intermittent harmonic injection method was verified from the simulation perspective. A comparative analysis was conducted between the intermittent harmonic injection method and the conventional harmonic injection method. The performance of the two methods in terms of their influence on the harmonic distortion rate (THD) value of the grid-connected current of the inverter was verified, providing high-precision parameter basis for the adaptive control and impedance reshaping of the inverter in a weak power grid environment.