Estimation Of Grid Inertia And Of The Weakening Of Power Grid Inertia Caused By Incorporating Wind Farms During Normal Operation

At present,wind power generation is already one of the most promising and dynamic renewable energy sources.China’s large-scale wind power base of 10 million kilowatts is gradually connected to the grid.As the penetration of wind power gradually increases,the inertia of the power grid will continue to weaken and seriously deteriorate the dynamic frequency characteristics of the grid.The synthetic inertia control is an effective means to solve the problem of weakened power system inertia and deterioration of dynamic frequency characteristics,but the existing methods lack the interface between theoretical research and engineering applications,resulting in a low application rate in wind farms.The study of effective methods to measure the inertia weakening of the power grid is of great significance to ensure the continued safe and stable operation of the power grid.In this paper,the quantitative study of grid inertia weakening caused by grid-connected wind farms is carried out from the following two aspects.(1)The quantitative estimation of grid inertia weakening caused by grid-connected wind farms bases on the estimation method of grid inertia under normal conditions.In this paper,we analyze the characteristics of the grid frequency response model under transient disturbances and ambient noise disturbances,and propose a method to identify the grid inertia based on the output error model.A processing method of data segmentation and moving data window is adopted,and the output error model order selected by different ranges.The outliers are eliminated to obtain sufficient inertia estimation samples and average value to reduce identification errors caused by random disturbances.the accuracy and effectiveness of this method were verified under normal data through simulation.(2)Considering the low inertia characteristics of wind farms connected to the grid,an expression for the inertia weakening of the grid when wind power is connected to the grid is proposed.The stability of the subspace method is verified by comparing the results of the system identification methods under transient disturbances.The subspace method is adopted to estimate the inertia weakening of the wind power grid under normal conditions.the accuracy and validity of the proposed method is verified by simulation under the change of operation mode.It would provide a solid theoretical basis and an important reference for the responsibility sharing of wind farms that are connected to the grid leading to inertia weakening.