Research on splitting criterion of the power system with wind-storage system integrated

Abstract

As the last defense line of the power system, splitting control is of great significance to the safety and stability of power grid. However, with the increasing penetration of wind power, photovoltaic, energy storage and other power electronic power sources in the grid, the transient stability of the power system is seriously affected. Meanwhile, the operation characteristics of power electronic power source are very different from that of traditional synchronous generator. The integration of power electronic power source affects the characteristics about out-of-step oscillation, and ultimately affects the safe implementation of splitting control. In order to split the power system more adaptably, a new splitting control method is proposed in this paper. Firstly, the equivalent external characteristic model of the wind-storage system is derived, and the influence of the wind-storage system on the out-of-step center is analyzed. Secondly, according to the out-of-step oscillation characteristics when the wind-storage system is integrated, line weak-connection index(LWcI) is proposed to evaluate the stability margin of the branch. Thirdly, according to the trajectory difference about LWcI-Δθ in all branches when it is unstable and stable, we propose the splitting control criterion based on LWcI-Δθ and the phase angle of voltage about the branch. Finally, the effectiveness and adaptability of the splitting criterion proposed in this paper are verified by simulation analysis of the improved IEEE-39 system.