电网故障下构网型逆变器动态限流控制策略

In order to deal with the problem that the increase of new energy power generation leads to the weakening of the inertia of traditional power grids, the grid-forming (GFM) control is proposed recently. In this paper, a mathematical model of typical GFM control is established and the mechanism of providing support for the system is analyzed. To solve the overcurrent problem under the grid voltage sags, the shortcomings of the traditional virtual impedance scheme are analyzed. Combined with the P-δ curve under the faults, a dynamic current-limiting control strategy with virtual impedance and power limitation is proposed. The adopted control scheme can dynamically limit the reference value of the power outer loop according to the degree of voltage sags. In this way, there is always an intersection between the power reference and the power angle curve of the system, which can effectively avoid the problem of outer loop saturation in the traditional current limiting method. The proposed control strategy is able to limit the current amplitude at various voltage sag depths, and effectively improve the dynamic response of the system during severe voltage sags. Finally, the feasibility and effectiveness of the proposed strategy are verified by simulations and experiments.