Robustness Investigation of Grid-Connected Inverter in Weak Grid and Optimization Based on an Improved Grid Voltage Feedforward Path

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For grid-connected inverter, phase-locked loop (PLL) and the grid voltage feedforward scheme are generally employed. While, both of them may deteriorate the system stability in weak grid. In view of this, the weighted grid voltage feedforward is adopted to make a trade-off between the system stability and the harmonics rejection ability, and this strategy has an optimized effect on PLL concurrently. Faced with larger grid impedance, an additional feedforward path is proposed for stabilizing the inverter. The results show that the inverter with the improved feedforward path can maintain good robustness against the wide grid impedance variation.