Improvement Control Scheme and Stability Analysis of VSG Under Asymmetrical Grid Conditions

Virtual synchronous generator (VSG) can be widely used in distributed generations because of its unique advantages. The control method and law of VSG under ideal working conditions are not suitable for the situation of asymmetrical grid voltage where cause problems such as output current imbalance and power oscillation. Thus, a new control strategy is proposed in this paper after analyzing the operation mechanism and response characteristics of VSG under asymmetric conditions. By discarding the negative sequence component of voltage and controlling the negative sequence component of current, this method can solve the problems of current imbalance and power oscillation simultaneously. In addition, a grid voltage feedforward control method is proposed to suppress the impulse current. After that, the parameter setting and stability analysis are carried out by establishing the mathematical model of the system. Finally, the accuracy of the proposed control strategy is verified through detailed simulation results.