This study examines whether power systems using 100% phase-locked loop (PLL)-synchronized voltage-source converters (VSCs) can operate independently. While grid-forming (GFM) technology lacks a unified definition

independent operation remains its core requirement. Current views incorrectly associate PLL synchronization solely with grid-following (GFL) control

assuming that PLL-based equipment requires support from synchronous generators or GFM devices. We challenge this by revealing three essential conditions for independent operation in fully PLL-synchronized systems: stable device synchronization

controllable node voltages

and adjustable system frequency. Through detailed analysis and tests

we prove these requirements can be met in 100% VSC systems using PLL synchronization. This discovery breaks the traditional link between operational independence and synchronization methods. Our findings offer new insights for developing renewable-dominated grids. The above three conditions have been proven to be achievable in a 100% PLL-synchronized VSC system.