Analysis and Suppression Strategy of Synchronous Frequency Resonance for Grid-Connected Converters With Power-Synchronous Control Method

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

“…A recognized low-frequency resonance issue of GFM control is SR [15], [11], [27], [12], [51], [16], [52], where the resonance frequency of output power or voltage magnitude of GFM-VSC closely aligns with the fundamental frequency (in fact slightly below [15], [16]). SR arises from the GFM control plant of the outer loops, such as the plant of PSC [15].…”

“…Based on the frequency range of interest, the power coupling can be categorized into two types: 1) static coupling [56], [62], [63] and 2) dynamic coupling [26], [64], [27], [51]. The static coupling is derived from the quasi-static model of the plant [63], where it characterizes the static gain of the transfer functions.…”

“…14, where the cross-coupling loops are eliminated. The studies in [26], [27], [51] present the detailed transfer functions of the decoupling controllers. The method can effectively improve the dynamic performances.…”

“…Thus, the stability margin is significantly enhanced, and a fast power control is achieved. Yet, the main issue of [27], [51] lies in the strong dependency of the decoupling controllers on the grid resistance and the grid inductance . Hence, the accurate estimation of and is critical for the PDC, which poses a challenge, particularly under stiff grid conditions, where and values are small.…”

“…This method effectively enhances the accuracy and performance of power decoupling when connected to stiff grids. The work in [26] is capable of integrating into PDC due to its adoption of the open-loop VVC, whereas the works in [27], [51] adopt closed-loop VVC in Fig. 1(b).…”