Comparative Analysis of Grid Impedance Estimation Methods for Online Stability Control of Renewable Energy

In the field of grid connected converter (GCC) stability analysis, there are several problems with grid impedance estimation. Firstly, due to time variant of grid network, traditional offline grid impedance measurement can no longer meet the adaptive control of GCC. Second, the traditional frequency sweeping method takes a long time, and the impedance obtained is in the frequency domain. If the realistic values of the inductance and resistance of the grid impedance can be directly obtained, it will be more convenient for evaluating the stability of the converter network system. Lastly, when injecting multi sine disturbances into the grid through converter, the disturbance peak may be large after the superposition of multiple harmonics, and the GCC may have problems such as overmodulation and harmonic pollution. Therefore, how to quickly and accurately measure grid impedance is the primary problem that needs to be solved in converter system stability analysis.