A Voltage-Power Droop-Based Damping Method for DC-Link Voltage-Synchronized Grid-Forming Converters

DC-link voltage regulation has been integrated with grid-forming (GFM) control in dc-link voltage-synchronized grid-forming (DVS-GFM) converters, which has recently attracted significant attention. However, conventional control is prone to unstable low-frequency oscillations from dc-link constant power/load. This paper firstly analyzes the small-signal stability of DVS-GFM converters under conventional matching control. It is found that matching control lacks a mechanism for implementing damping, leading to low-frequency oscillations on the dc side. To address this issue, a voltage-power droop-based damping method is proposed. It is revealed that the voltage-power droop branch, operating in parallel with the matching control, effectively serves as a mechanism for implementing damping. The proposed damping method can dampen the oscillations and enhance the dynamic response performance of the dc-link voltage. The experimental results validate the effectiveness of the proposed damping method.