Design and Analysis of High-Frequency Phase Compensation Strategies for CCF-Controlled LCL Filter-Based Grid-Connected Converter

High frequency phase compensation algorithm (HFPC) is proposed in this paper to improve the stability margin of LCL filter-based grid-connected converters under converter current feedback control (CCF). To reveal the impact of different state feedback on the system’s operational characteristics, a discrete state-space model considering digital control delay has been established. On this basis, the stability range of CCF control has been determined. Accordingly, a linear predictor (LP)-based compensation method is proposed to improve the stability margin of the CCF system, and its operation mechanism and limitations are both studied as well. HFPC, including improved phase compensation (IPC) and current reconstruction (CR), is employed to further enhance the phase compensation performance of LP. Specifically, IPC is implemented to alleviate the high frequency open-loop gain caused by traditional methods such as LP, thus expanding the gain margin. CR can push the critical crossover frequency to a higher frequency band, thereby enhancing the system’s stability margin and improving current quality. The experimental results clearly validate the correctness and feasibility of the proposed method.