Uninhabited electric vehicle typically utilize batteries as an exclusive power source. In order to remedy the limited energy density and thus operation time of the battery-powered unmanned vehicles, fuel based range extenders are often utilized. The operation strategy for the range extender is to maximize the mission endurance therefore it should operate at minimum specific fuel consumption point. Furthermore, the source and load voltage level may differ, hence non-inverting Buck-Boost converter (NBC) is conjoint them while keeping the desire operation point. This paper proposes a fuel cell (FC) based range extender, interfaced to the main power bus by cascade output power regulation strategy for NBC. The NBC is based on unique modulator that produces switching sequence for both converter legs. The modulator receive single control input from the dual loop regulator, inner inductor current loop and outer output power loop, which is common for energy management strategies of hybrid energy sources. System design commences with regulator design based on small signal analysis of NBC, and then it is shown that the suggested control architecture allows tight output power control throughout the entire operating range despite various plants. Finally a case study is presented, in which the converter operates as power processing interface of a fuel cell, operating as range extender in an all-electrical aircraft. The revealed findings are well-supported by simulation and experimental results.