Synchronization-Damping Stabilization of DVSC-Based Grid-Forming PV Systems Across Varying Grid Strengths and Power Levels

DC-link voltage synchronization control (DVSC), or matching control, offers a simple grid-forming (GFM) solution for two-stage photovoltaic (PV) systems by linking the DC-link voltage to converter frequency. However, its low-frequency damping is sensitive to grid strength and power-transfer level. This paper investigates the damping and synchronization characteristics of DVSC-based grid-forming PV systems under varying operating conditions. A reduced-order small-signal model is developed to decompose the contributions of the DVSC loop, electrical network, and terminal-voltage regulation. The analysis reveals that the basic DVSC loop provides no inherent damping, while the interaction between voltage regulation, grid impedance, and transferred power may introduce negative damping or reduce the synchronizing margin. The operating-condition-dependent limitations of lead-phase correction and q-axis voltage feedforward are then identified. To supplement these methods, DC-link-voltage-feedback d- and q-axis voltage stabilizers are designed and integrated with DVSC reshaping in a composite stabilization scheme. Eigenvalue analysis and OPAL-RT real-time simulations demonstrate the complementary damping characteristics of the four stabilizing paths.