考虑光伏功率动态特性与电网强度适应性的构网型光伏系统直流链路电压同步控制增强方法

The integration of large-scale photovoltaics induces significant challenges of low inertia and weak damping within power grids. To effectively address these issues, grid-forming (GFM) strategies have been adopted in photovoltaic systems (PV). In such systems, the front-stage converter is tasked with maximum power tracking, while the back-stage adopts dc-link voltage-synchronized control. However, conventional modeling of the photovoltaic and front-stage dynamics via a constant power source (CPS) model tends to neglect the intrinsic impedance of the front-stage converter, leading to inaccuracies in stability identification. To rectify this oversight, this paper introduces an equivalent circuit model of the PV front-stage converter, which features a power source combined with parallel impedance (PPI), precisely capturing the PV front-stage dynamics and facilitating the stability analysis of the back-stage converter. Furthermore, to address the issue of the low-frequency oscillation induced by the conventional matching control, an enhanced dc-link voltage synchronization strategy is proposed in this paper. This strategy integrates a proportional loop in parallel with a low-pass filter loop. The dc-link voltage regulation, grid strength adaptability, and grid support capability of the PV-GFM system with the proposed strategy are quantified analytically and verified by case studies.