UPS input impedance measurement method based on sine wave injection

The invention discloses a UPS input impedance measurement method based on sine wave injection, and the method comprises the following steps of: sequentially injecting AC small signal disturbance voltages with different frequencies into an input port of a tested power supply device in a series connection manner, and respectively extracting voltage and current signals of the input port before and after injection for sampling analysis; calculating the difference voltage and the difference current of the disturbance frequency before and after the disturbance injection, with the ratio of the voltage to the current being the input impedance under the disturbance frequency, thus obtaining the input impedance characteristic of the tested power supply equipment. Compared with the prior art, the method has the advantages that: for the condition that a power supply has harmonic waves, background harmonic voltage and current except excitation voltage and response current can be eliminated through the difference value mea