Confidence analysis on identification results of three-phase voltage source inverters d-q impedance from transient response to load steps

Stability assessment of three-phase AC distributed power systems can be carried out using d-q impedance and admittance models of the load and source subsystems. To do so, an impedance identification technique of three-phase voltage source inverters, based on the transient response to reactive and active power steps, have been recently reported. However, in the reported work, no method to evaluate the accuracy of the identification results, in frequency domain, has been described. In this paper, a method to determine the bandwidth where the model can be confidently identified, as well as the identification accuracy within such a bandwidth, is proposed. This method is based on a spectral analysis of the transient waveforms. It is illustrated and discussed using a simulation case study.