Impacts of Grid Structure on PLL-Synchronization Stability of Converter-Integrated Power Systems

Abstract

Small-signal instability of grid-connected power converters may arise when the converters use phase-locked loops (PLLs) to synchronize with a weak grid, i.e., operating in grid-following mode. Commonly, this stability problem (referred to as PLL-synchronization stability in this paper) was studied by employing a single-converter system connected to an infinite bus, which, however, omits the impacts of the power grid structure and the interactions among multiple converters. Motivated by this, we investigate how the grid structure affects the PLL-synchronization stability of multi-converter systems. Moreover, we provide guidelines on how to improve the PLL-synchronization stability of multi-converter systems by PLL-retuning, proper placement of converters, or enhancing some weak connections in the network. Finally, we validate our findings with simulation results based on a 39-bus test system. Copyright (C) 2022 The Authors.