Parameter identification of PLL for grid-connected inverter based on parameter sensitivity analysis

Under the condition of weak grid, the phase-locked loop (PLL) is one of the main reasons for the sub-synchronous oscillation of the grid-connected inverter. Therefore, it is necessary to identify the PLL parameters of the grid-connected inverter for the analysis of the inverter operating performance. This paper uses the sequence impedance model and measured impedance data of grid-connected inverter to construct the identification function for parameter identification of PLL, and the function is calculated by particle swarm optimization algorithm to overcome the nonlinear problem of sequence impedance model. In addition, the identification frequency band is selected based on PLL parameter sensitivity to improve the parameter identification accuracy under the same impedance measurement error. At different frequencies, the positive correlation between the sensitivity of the PLL parameters and the identification accuracy is proven to determine the definite frequency band for PLL parameter identification of grid-connected inverter. Finally, the feasibility and effectiveness of the above research are verified by simulation and semi-physical experiments.