Stability Analysis and Interaction of VSC Grid-Connected System under Weak Grid Condition

Aiming at the instability problem caused by the reciprocal action between the voltage source converter (VSC) and the weak ties grid, the stability analysis and interaction research of the VSC grid-connected system under the weak ties grid condition are carried out. The stability analysis model of equivalent weak grid and converter cascade system is established, and a quantitative evaluation method of system stability is proposed to clarify the stable boundary of VSC control parameters under weak ties grid. The interaction influence of short-circuit ratio (SCR) and parameters of controller on the stability of grid-connected system is analyzed from two aspects of weak grid side and converter control loop. It is found that with the decrease of the grid condition, the parameter range of system instability will increase, and the influence of current loop proportional parameter is greater than that of integral parameter. Through simulation, the validity of the proposed analyzed method is proved.