Applying Vector Fitting for Measurement-based Multiple-Input Multiple-Output Model Identification of a Grid-Forming Converter

This paper presents an approach for applying Vector Fitting (VF) to identify a small-signal state-space model of a power electronic converter represented as a multiple-input multiple-output (MIMO) system. A workflow for the proposed model identification procedure is presented, with focus on aspects related to the processing of data from measurements and on the configuration of the VF algorithm. An example of how a small-signal state-space model can be identified from laboratory measurements on a 50 kW grid-forming converter is presented to demonstrate how VF is suitable for identifying black-box MIMO models of power converters. The identification procedure is applied to the full matrix of transfer functions between the input and output combinations obtained from the laboratory measurements. The accuracy of the resulting state-space model is verified in the frequency-domain and by time-domain simulations. Finally, limitations of the presented approach are discussed.