Optimal control strategy of three level STATCOM in weak power grid

The line distance under weak power grid is long, the system capacity is large, and the grid impedance increases when the grid operation state changes, which leads to the instability and even shutdown of STATCOM. Therefore, this paper proposes an optimal control strategy for neutral point clamped (NPC) three-level STATCOM with fast response to line impedance. On the one hand, through the establishment of the mathematical model of the system, the operating characteristics of the system are analyzed; On the other hand, by introducing the disturbance term of PLL with line impedance, a system model suitable for weak power grid is established to study the influence of line impedance on the system, and a filter differential controller is used to quickly respond to line impedance to improve the robustness of the system. Finally, the effectiveness of the method is verified by simulation and experiment.