Estimation of the Weakening of Power Grid Inertia Caused by Incorporating Wind Farms in Normal Operation

Large-scale integration of wind power into a power grid can reduce the grid's inertia, causing the grid's dynamic frequency characteristics to deteriorate. Precise and quantitative estimates of these grid-inertia weakening effects could enable the responsible development of wind-derived energy-sharing methods. Furthermore, these data provide a reliable empirical basis for a theoretical understanding of the factors involved, which is needed to facilitate the gradual implementation of synthetic inertia control technology. In this study, we report developing and testing a method for obtaining accurate estimates of grid-inertia weakening caused by incorporating wind farm inputs during normal operation. Briefly, active power-frequency ambient noise information from random disturbances was extracted under normal conditions, and the Time-Varying Forgetting Factor Recursive Least Squares (VFF-RLS) method of system identification was used to estimate grid inertia when wind farms were grid-connected versus off-grid, respectively. The difference between these two parameters was then used to obtain the weakening of grid inertia caused by wind farms. Analysis of the IEEE 39-bus system verified that the proposed method could continuously and effectively estimate grid inertia weakening, with accurate and reliable estimates of grid inertia when wind farms were grid-connected versus off-grid.