Large-Signal Strength Assessment of Grid Connecting Assets Using Contraction Analysis

This paper analytically investigates the key properties of large-signal strength at the grid connection point of generation/storage technologies, focusing on their capability to maintain grid synchronism following severe disturbances. We define conditions where the technology can maintain 1) its terminal voltage magnitude, 2) synchronism, and 3) its power exchange with the grid within its power transfer limit. These conditions are represented by boundaries related to a proper voltage-behind-an-impedance (VBAI) response. Specifically, we first identify variables that represent the generation/storage technology’s dynamic behavior in relation to each key VBAI property. We employ contraction analysis to derive explicit boundary conditions for the perturbed variables, guaranteeing exponential convergence between trajectories. Simulation results for a synchronous generator validate the proposed method performance, confirming that remaining within the derived region ensures exponential convergence to the steady-state point following large disturbances, while results for a grid-following inverter provide insights into the importance of the phase-locked-loop control coefficient values. The derived conditions serve as a proxy for system operators in identifying stable operational regions for connecting new assets.