Augmenting load flow software for reliable steady-state voltage stability studies

For decades, researchers and practitioners have developed improvements for Newton-Raphson (N-R) load flow to overcome some of its limitations. In this paper, we present a novel method to solve those inherent iterative algorithm limitations. It is based on N-R combined with a supplementary algorithm that uses the discrete Fourier transform (DFT) and robust Padé approximants (PAs) and it is suitable for planning and simulation studies. This novel method analyses bus behaviour from the loading perspective where plain N-R may not converge to the correct results. Thus, avoiding possible performance deficiencies when bus loading approaches the stability limit or when starting point is not close enough to the actual operating value. The proposed method samples voltages in the complex domain to attain superior convergence properties, guaranteeing high accuracy within the bus-voltage stability limits (VSLs). Additionally, as a by-product of the proposed method, load buses can be classified according to their criticality. The presented method will suit existing N-R-based systems with minor modifications, allowing practitioners to preserve their investment in load flow software. Results and performance comparisons with the conventional N-R, holomorphic embedding load flow method (HELM), and continuation power flow (CPF) are presented to demonstrate the robustness of the proposed method.