Abstract:

To address the challenges of current over-limitation and limited voltage support capability in grid-forming energy storage converters during low-voltage ride-through (LVRT) under grid fault-induced voltage sags, this study proposes a reactive power coordination control strategy for a hybrid Virtual Synchronous Generator (VSG) and Static Var Generator (SVG) system incorporating an LVRT current limiting strategy. Initially, the typical control methodology of VSG is presented, followed by a transient characteristic analysis of its power-angle curve under various grid voltage dip scenarios. Subsequently, an improved q-axis priority current limiting strategy is developed, where the active power reference value is proportionally reduced according to the diminished d-axis current, resulting in an adaptive active power reference q-axis priority current limiting approach. Furthermore, to overcome the restricted voltage support capacity of standalone VSG during severe grid voltage sags, a collaborative control framework integrating SVG with VSG is established, accompanied by a reactive power allocation strategy. The effectiveness of the proposed methodology is conclusively validated through SIMULINK simulation results. The experimental results demonstrate that the proposed current-limiting strategy effectively restricts the output current, while the hybrid system control methodology significantly enhances voltage recovery performance during grid voltage sags.

Key words:

low-voltage ride-through, current-limiting, virtual synchronous generator, static var generator;

coordinated reactive power control