Online estimation of wideband output impedance and control parameters of single-phase inverters using pseudo-random perturbation

Abstract

The growing deployment of single-phase inverters in residential low-voltage distribution networks poses new challenges to system stability and power quality. Accurate simulation models are essential for analysing these effects and enabling scenario assessment without costly and time-consuming physical testing. Wideband inverter models, in particular, are critical for capturing the inverter’s dynamic behaviour across a broad frequency range. The inverter’s output impedance profile plays a key role in identifying internal parameters, such as filter and control settings, typically not disclosed by manufacturers, and supports impedance-based stability analysis. This paper presents a methodology for online estimating an inverter’s wideband output impedance and internal control parameters. A pseudo-random impulse sequence is injected into the inverter AC terminals in situ to perturb the system, from which the output impedance is estimated. A case study on a standalone single-phase inverter supplying $2.6A_{\text{RMS}}$ demonstrates a strong correlation between the experimentally derived impedance and its analytical counterpart. The inverter’s impedance frequency response and time-domain output signals are further analysed to extract controller parameters using a three-step estimation process based on particle swarm optimisation. The approach is validated through both simulation and experimental results, confirming its accuracy and effectiveness in parameter identification.