Online Prediction Nadir Point in Primary Frequency Response of Power System Containing Converter-Based Generation

In low-inertia power systems, the primary frequency response is of great interest. Based on the frequency nadir, the frequency response can be quickly analyzed to see whether it will disrupt the stable operation of the grid, so this paper proposes an online prediction method for the frequency nadir. Firstly, a detailed frequency response model containing converter-based generation to provide frequency support is established, and the model structure is simplified according to the common features of the complex control loops. The simplified model can easily achieve the analytical expression of the frequency nadir so that the frequency nadir prediction can be performed by parameter calculation. In the derived frequency nadir expression, the system parameters that are strongly frequency-dependent, such as inertia, and the simplified frequency regulation parameters are retained. In order to enhance the fit between the frequency nadir prediction and the actual system, these parameters are obtained through online information, where the system parameters are based on online estimation, and the simplified frequency regulation parameters are obtained through parameter identification. Case tests demonstrate the effectiveness of the proposed method and are easy to implement.