A Robust Circuit and Controller ParametersIdentification Method of Grid-Connected VoltageSource Converters Using Vector Fitting Algorithm

Abstract

This article presents a vector fitting (VF) algorithmbased robust circuit and controller parameters identification method for grid-connected voltage source converters (VSCs). The dq-domain impedance frequency responses (IFRs) of the VSCs are first measured using frequency scanning method, based on which the corresponding measured phasor-domain IFRs are calculated. Then, polynomial transfer functions are generated by applying the VF algorithm on the measured phasor-domain IFRs, from which the circuit and controller parameters, i.e., LCL filter parameters, digital sampling time, current controller parameters, and phase-locked loop parameters, are identified. Influence of measurement noise on parameters identification accuracy and corresponding countermeasure to mitigate the adverse influence are also theoretically investigated. The proposed method is able to identify the circuit and controller parameters, when detailed parameters are missing due to industrial secrecy or parameters variation caused by operating condition change, temperature fluctuation, or aging. Effectiveness of the proposed circuit and controller parameters identification method is validated by theoretical demonstration, OPAL-RT-based real-time simulation, and experimental validation. Index Terms—Impedance frequency responses, parameters identification, polynomial transfer function, vector fitting algorithm, voltage source converter.