Abstract:
The grid-current-feedback-active-damping control strategy (GCFAD) has the function to effectively suppress the resonance peak of the LCL-type grid-connected inverter without requiring additional sensors. The GCFAD strategy is often used together with the grid voltage feedforward strategy to improve the quality of the grid current in a weak and disturbing grid. However, it is found that the positive resistance characteristics of the virtual impedance in the middle and low frequency bands under the traditional GCFAD strategy may cause a phase lag of the output impedance in the middle band, which reduces the robustness of the system when the grid voltage feedforward strategy is involved. In order to solve this problem, this paper proposes a high robustness grid-current-feedback-active-damping strategy (HR-GCFAD), which makes the virtual impedance exhibit positive resistance characteristics at high frequencies to suppress the LCL resonance peak and strengthen the stability of the system. It exhibits negative resistance characteristics in the middle and low frequency bands, which improves the robustness of the grid-connected inverter in a weak grid. Theoretical analysis and experimental results fully verify the effectiveness of the proposed strategy.