Research on Adaptive Control Strategies Based on VSG under Unbalanced Grid Voltage Conditions

Under grid voltage imbalance conditions, converters controlled by traditional VSG are prone to issues such as three-phase output current asymmetry and fluctuations in active and reactive power. To enhance the performance of current regulation under unbalanced grid voltage scenarios, this study introduces an improved control approach based on virtual synchronous generator principles. By dynamically coordinating the adjustment of virtual inertia and damping parameters in response to system conditions, the method effectively improves current symmetry during voltage asymmetry disturbances. First, the operational characteristics of VSG under unbalanced voltage conditions and their differences from traditional converter control strategies are analyzed. Subsequently, by establishing a mathematical model of the VSG control system, the effects of virtual inertia J and damping coefficient D on system frequency stability are thoroughly investigated, and based on this, a control strategy for the adaptive coordination of inertia and damping regulation is designed. Finally, the proposed control scheme was validated using a grid-connected converter simulation model with a rated power of 50kW. The simulation results confirm that the proposed strategy effectively improves system stability while ensuring balanced current output, demonstrating its practical applicability and control effectiveness.