Small-Signal Stability of Multi-Converter Infeed Power Grids with Symmetry

Traditional power systems have been gradually shifting to power-electronic-based ones, with more electronic devices (including converters) incorporated recently. Faced much complicated dynamics, it is a great challenge uncover its physical mechanisms for system stability and/or instability (oscillation). In this paper, we first establish nonlinear model of multi-converter within the DC-link voltage timescale, from principle. Then, obtain linearized associated characteristic matrix, whose eigenvalues determine stability, and finally get independent subsystems by using symmetry approximation conditions under assumptions that all converters’ parameters their susceptance infinite bus (Bg) are identical. Based on these mathematical analyses, find whole can be decomposed into several equivalent single-converter small-signal solely determined simple converter connected an same Bg. These results large-scale analysis help understand such as renewable energy integration. As well, they expected stimulate broad interests among researchers in fields network dynamics theory applications.