Admittance Modeling and Stability Analysis of Grid-Connected Inverter With LADRC-PLL

It tends to cause system oscillation when the inverter with a phase-locked loop based on proportional integral controller (PI-PLL) is connected weak grid. To improve suppression ability of grid-connected inverter, linear active disturbance rejection applied PLL (LADRC-PLL). Considering influence extended state observer, voltage outer-loop, current inner-loop, and frequency coupling, admittance model LADRC-PLL established. Based established generalized Nyquist criterion, stabilities inverters PI-PLL are compared. The comparison results indicate that has better adaptability grid shows certain suppress sub supersynchronous oscillation. Then, control parameters stability studied. found keeps stable parameter changed in relatively wide range, which indicates good robustness. Furthermore, dynamic performances analyzed. revealed performance. Finally, correctness analysis verified by experiments.