An Enhanced Phase-Locked Loop with Extended State Observer

This paper aims at enhancing the robustness and the disturbance rejection ability of a Phase-Locked Loop (PLL). An Extended State Observer (ESO)-based controller is implemented into the loop filter for this purpose. Firstly, the total unpredictable disturbances (phase jumps, frequency variations, nonlinear dynamics, etc.) are estimated by the ESO. Then, the observed generalized disturbances are actively compensated into the closed-loop dynamics in real-time, and the dynamic behaviours and its robustness are thus enhanced. Besides, the proposed strategy is simple to design and implement for practical engineers. Simulations and experimental results are both provided to verify its effectiveness.