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This article presents a stability analysis of photovoltaic (PV) clusters forming a dc microgrid with a distributed power reserve capability. The PV clusters feature flexible PV power generation under fluctuating ambient conditions via the distributed power reserve control. The PV set-points are adjusted based on grid operator command that is accomplished in a decentralized manner. Stability analysis of the PV clusters has been carried out to determine the safe operation regions of the PV units with respect to operation set-point adjustments. The proposed stability analysis approach considers all the characteristics of the PV subsystems. The stability analysis demonstrates that the PV cluster architecture is stable as far as the dc bus stray resistance has a finite value. Also, the grid-interfacing converter must operate in input current control mode (CCM) instead of input voltage control mode (VCM) for better stability margin. Several case studies are emulated on an IEEE 5-Bus system using real-time controller hardware in the loop (C-HIL) to verify the stability and the theoretical expectations of the proposed system.