Phase-Locked Loop Small-Signal Disturbance Compensation Control for Three-Phase LCL-Type Grid-Connected Converter under Weak Grid

For LCL-type grid-connected converter, the grid current control interacts with phase-locked loop (PLL) under weak grid, via point of common coupling (PCC) voltage. And PLL disturbance has negative effect on the grid current control. Thus, the grid current control renders undesired performance, even instability. To mitigate this problem, a simple small-signal disturbance compensation control method is proposed for three-phase LCL-type grid-connected converter. Under the proposed method, the negative small-signal disturbance effect of PLL dynamic on the grid current control can be reduced under weak grid, without changing the PLL parameters and structure. The current control performance and its robustness to the grid impedance changes are significantly improved. Moreover, the method is not influenced by the circuit parameters variation. Finally, the proposed method is validated by experiment.