Performance evaluation of wideband binary identification of grid impedance using grid-connected inverters

The application of the pseudo random binary sequence (PRBS) estimation technique for wideband grid impedance estimation using grid-connected inverters has gained more attention recently because of its several advantages. This includes its simple implementation in the control loop of the inverters and the small disturbance amplitude produced. In this context, this paper aims to evaluate the performance influences of the PRBS design parameters bit length, frequency resolution, and disturbance amplitude. This goal is achieved by exploring their effects on the grid impedance estimation accuracy and the produced total distortion (THD%+PRBS noise) of the inverter output current. A 3-phase balanced inverter system is simulated and investigated using MATLAB/Simulink based on a discrete-time model to show the trade-off of a real implementation such as the PRBS disturbance amplitude and the sampling frequency of the analog-to-digital converters. Simulation results show the trade-off between the investigated PRBS parameters and the accuracy and frequency range of the estimated grid impedance as well as the total distortion.