We have developed an alternative method to characterize inverters through impedance by using only a few sets of time-series data. This data is then analyzed through Eigensystem Realization Algorithm (ERA) to find the frequency-domain models. In other words, step responses are used to find the dq-frame impedance or admittance models via ERA. The results show that the frequency responses of the impedances identified show a close match to the actual impedances measured. This technology can be useful for impedance-based stability analysis or in general where measured impedance plays a role in maintaining proper functions of machinery in the power industry.
Comparison of Impedance Bode Plots When Uniformly Distributed Zero Mean 0.2 Variance Noise is Used