Island detection method for impedance measurement of DC power system with multi-photovoltaic power supply and grid

The invention belongs to the technical field of power system analysis, in particular to an island detection method for impedance measurement of a DC power system with multi-photovoltaic power supply and a grid, which comprises the following steps of: using an intermittent blocking DC/DC converter sub module to inject high-frequency harmonic disturbances with specific frequencies into the DC systemat a fixed time interval. PCC point voltage and current signals are collected in the time period of harmonic injection, the information of injection frequency is extracted by Fourier algorithm, and the harmonic reactance is calculated and measured. The island is judged according to the change of reactance amplitude. The high-frequency reactance is selected as the characteristic quantity to amplify the characteristic difference before and after island while reducing the effect of DC load variation on the protective action threshold. The effect of low duty cycle intermittent injection on powerquality is reduced. The me