Visualisation and Analysis of Super-Synchronous Interactions of Grid Assets using Wavelet Transform

This contribution proposes an approach for the visualisation and analysis of interactions of grid assets in both the time and frequency domains simultaneously, using the Wavelet transform. The Wavelet transform enables a detailed analysis of any signal in the time domain, providing insights into the occurrence and evolution of individual frequency components over time. Hence, this approach bridges the gap between classical small-signal stability analysis in the frequency domain, with its drawbacks due to linearisation, and Electromagnetic Transient (EMT) simulation and analysis, which lacks detailed information about the participating frequency components. The method is demonstrated on simulation results of a high-voltage direct-current converter and its response to a three-phase fault. Here, the analysis reveals an additional frequency component at 250 Hz. In particular, consideration of the derived time and frequency dependent converter impedance supports a more detailed analysis of this frequency component and its behaviour over time.