A Robust Method for Controlling Grid-Connected Inverters in Weak Grids

Stable operation of grid-connected converters with the LCL filter is essential. Variations grid impedance and consequently, variations resonance frequency, can push system toward instability. Also, delay that comes from sampling PWM, could worsen stability condition. Thus, control should be designed by considering these non-ideal factors. To fill in this gap, brief presents an effective but simple method based on biquad filter, which enhances robustness guarantees a varying Besides, suggested technique free employing any active damping mechanism, turn, increases reliability reduces cost. Finally, experimental results are provided to show accuracy analysis verify proposed method.