The DSOGI-PLL with the repetitive control internal model suppresses the SSO in the PV system

The interaction between PV system and inductive grid impedance under weak grid is easy to cause sub-/super-synchronous oscillation (SSO). The coupling phenomenon between grid impedance and PLL cannot be ignored. In this paper, the influence of output phase of PLL on coordinate transformation is analyzed, and a mathematical model of PV inverter considering oscillation phase is established. By establishing and analyzing the mathematical model, the mechanism of SSO disturbance of photovoltaic inverter is expounded, and the disturbance can be divided into error disturbance and grid disturbance. According to the mechanism of the disturbance, a scheme combining DSOGI-PLL (Dual Second Order Generalized Integrator) and repetitive control internal model is proposed to suppress the SSO. For grid disturbance, the designed repetitive control internal model can eliminate the harmonics in the system. For error disturbance, DSOGI-PLL can eliminate the error of PLL output phase caused by grid voltage oscillation, and accurately lock the phase. The performance and robustness of the presented scheme are proved in time-domain simulations.