Identification Method of Weak Links Based on Grid Strength Assessment

The modern power grid features the high penetration of renewable energy resources and power electronic devices, which aggravates the coupling effect both between power electronic devices and the power grid and between different devices, and hence increases the risk of oscillation and small-signal instability. Therefore, it is urgent to discriminate the weak links of buses and AC lines in the power grid, and then carry out targeted operation control. This paper explores the method of identifying power system weak links by using the generalized short-circuit ratio (gSCR) index from the perspective of small-signal stability. We establish the characteristic equation of the multi-infeed power electronic system and analyze the small-signal stability based on the gSCR index, i.e., the evaluation index of power grid strength. According to the sensitivity of the gSCR to the control parameters of power electronic devices and the admittance parameters of AC lines, we find that links with the maximum sensitivity are the weakest links of buses and AC lines in the power grid. Finally, the weak link identification method proposed in this paper is validated through the eigenvalue analysis of a 5-infeed power electronic system.