A Single-Loop Active Disturbance Rejection Control of PMSG for Suppressing Subsynchronous Resonance

Under weak grid, permanent magnetic synchronous generator (PMSG) is prone to occur subsynchronous resonance (SSR), which seriously threatens the security of power systems. First, the mechanism and characteristics of this SSR are analyzed based on the impedance method. As the decrease of grid stiffness, the PMSG will oscillate due to the impedance interaction between the inductive grid impedance and the capacitive PMSG impedance in the low-frequency range. To suppress this SSR, a single-loop active disturbance rejection control (ADRC) of the PMSG grid-side converter (GSC) is proposed, which consists of two different single-loop controllers of the d- and q-axis. Meanwhile, a differential feedforward control is applied to reduce the tracking error of linear extended state observer. Under the proposed control, the impedance of PMSG no longer has capacitive characteristics, which will not cause impedance resonance with the weak grid. Compared with the voltage and current dual loop ADRC, the proposed single-loop ADRC directly adjust dc-side voltage of GSC with considering ac-side current, which can improve the dynamic and steady-state performance of the PMSG. Finally, the effectiveness of the proposed SSR suppression method is verified by the simulation and experimental study.