Robust Synchronization Control for Grid-Forming Converters with Regulated DC-Link Dynamics

Abstract

<p>For grid-forming (GFM) converters, the dc-link voltage control (DVC) can directly generate the frequency that is used for the grid synchronization. However, this method suffers from low-frequency oscillations (LFO). To tackle this challenge, this paper proposes a robust synchronization control for GFM converters. In the approach, the DVC and the <em>q</em>-axis voltage feedforward control loops are connected in parallel for the synchronization purpose. Compared with the conventional single-loop DVC scheme, the proposed synchronization approach can dampen the LFO. Compared with conventional cascaded or paralleled DVC and active power control schemes, the proposed synchronization approach can avoid the trade-off between LFO and synchronous resonance issues. Experimental tests of GFM converters are performed in rectifier and inverter modes. The results confirm the effectiveness of theoretical analysis and the performance of the proposed control approach. </p>