Adaptive-saturation-based transient stability enhancement for grid-following inverters

This paper proposes an adaptive saturation module to enhance the transient stability of grid-following inverters after voltage-dip inception and fault-clearance moment. The equal-area criterion reveals that a large acceleration area will be obtained due to the step change of current reference according to grid codes, which may lead to the loss of synchronism with the grid. It is found that the saturation module used with the phase-locked loop can enhance the transient stability performance by reducing the acceleration area. To simultaneously adapt to the two cases (the inception and clearance of the voltage-dip fault), an adaptive saturation module that can automatically adjust the clamping mode is proposed, which is the main contribution of the paper. The selection of the threshold value for the saturation module is also presented. A comprehensive comparison is made between the proposed solution and state-of-art solutions. Finally, the effectiveness of the proposed control strategy is confirmed by the experimental tests.