An In-Field Eigenvalue-Based Stability Assessment Method for Low-Frequency Dynamic Interaction Between Voltage Source Converters and the Grid

Voltage-source converters (VSCs) are essential for renewable energy. However, the oscillatory behavior generated by dynamic interaction between VSCs and the grid is a challenging issue due to the interaction’s intricacy and unknown system details. After introducing VSCs into the power system, stability assessment is often wanted. “Perturbation-based impedance measuring + Middle-Brook criterion” is a well-known approach. However, this approach is rarely adopted due to the need for perturbation devices (PDs). So this article proposes a stability assessment method to obtain the system eigenvalue map. This method does not need PDs, so is in-field adaptive. The eigenvalue map is evaluated from closed-loop frequency responses (FRs) by vector fitting (VF), and the FRs are measured by the VSC itself. To support the method theoretically, a modularized model of the VSC-grid system is derived. The model indicates how each closed-loop FR of the VSC(s) reflects all the eigenvalues of the VSC-grid system. Because the transfer zeros of some FRs reduce the observability of some eigenvalues, weighted combination of VF results from multiple FRs is adopted in the proposed method to guarantee the precision. The accuracy of the proposed assessment method and investigation results is verified by both simulations and experiments.