Versatile Measurement Method for Three-Phase Impedance in a Two-Phase Domain

This paper proposes a new impedance measurement method based on the series voltage excitation and the shunt current injection approaches in a two-axis domain for a three-phase AC system. The proposed method consists of three steps. First a perturbation of a frequency response analyzer (FRA) is given as a two-axis domain signal, and this signal is inversely converted into a three-phase signal by a digital signal processor (DSP) and applied to the actual system as an excitation series voltage or shunt current. Secondly the response three-phase current or voltage for the excitation is measured, and it is reconverted into the original two-axis domain signal by the DSP. Finally, the impedance or admittance characteristics are obtained by the FRA from the ratio between the excitation and response signals. The proposed measurement method is validated by comparison of analytical solutions with simulation and experiment results.