A renewable energy hybrid power plant, fed by photovoltaic (PV), wind turbine (WT), and fuel cell (FC) sources with a supercapacitor (SC) storage device and suitable for distributed cogeneration applications, is proposed herein. The PV, the WT, and the FC are used as the main source; and the SC functions as an auxiliary source and a short-term storage system for supplying the deficiency power (transient and steady-state) from the main sources. Based on the flatness property for dc grid voltage stabilization, we propose a simple solution to the fast response and stabilization problems in the power system. This is the innovative contribution of this paper. The prototype small-scale power plant implemented was composed of a PEMFC system (1.2 kW, 46 A), a PV array (0.8 kW), a WT (1 kW), and an SC module (100 F, 32 V). Experimental results validate the excellent control algorithm during load cycles.