A Novel Voltage based Synchronization Method for Maximum Power Factor Injection of Grid-Tied Converter in Extremely Weak Grid

As the penetration of power electronic converter-based resources in the power system increases, the robustness of the grid weakens. In a weak grid with relatively high equivalent system impedance, the voltage magnitude at the point of common coupling (PCC) fluctuates significantly due to voltage drop when injecting active power. This reduces the stability of the phase-locked loop (PLL) used for synchronizing grid-connected converters with the power grid and decreases the power factor that the grid can accommodate. This paper analyzes the transient stability of grid-connected converters using V-δ curve and proposes a method for ensuring stable synchronization with the weak grid while injecting power at the maximum power factor, even under extremely weak grid conditions.