FRA-based DQ Impedance Measurement for Three-Phase Power Electronic Systems

This paper proposes a dq impedance or an admittance measurement method based on the series voltage method for a three-phase power electronic system (PES). The measuring system consists of a digital signal processor (DSP) and a frequency response analyzer (FRA) for signal generation and processing. A perturbation sinusoidal signal of FRA is utilized as the excitation voltage signal for d or q axis, and it is converted into phase-domain signals which are applied to a PES under test. Measured response currents in phase domain are converted into dq domain again by DSP and are sent to the FRA. Admittance characteristics are processed by the FRA as a ratio between the excitation voltage and the response current signals in dq domain. The proposed measurement method is validated by comparison between analytical and experimental results.