Viability of Synchronous Reference Frame Phase Locked Loop Inverter Control in an All Inverter Grid

State of the art bulk power system connected inverter based resources make use of a variant of a synchronous reference frame (SRF) phase locked loop (PLL) in order to track the phase angle of the grid and subsequently inject current into the grid. Successful and speedy tracking of this angle is considered to be a requirement for stable operation of the inverter in grid connected mode. However, it has been postulated in literature that in 100% inverter grids, conventional SRF-PLL based inverter controls will be unable to operate in a stable manner as they follow a grid voltage. In this paper, it will be shown that there could be certain loading levels and system topologies for which an SRF-PLL based 100% inverter system can be operated in a stable manner and thus, a blanket statement that it would not be able to operate could be misleading to a transmission planner. Simulation results shown in this paper were conducted in electromagnetic transient domain.