In this paper, we propose the dynamic simulation of a hybrid generator that integrates a fuel cell as the main source and a supercapacitor as the secondary source. We interface the proposed generator to the load using elementary power-conditioning units, and it is connected to a 36 V bus for DC applications. The powertrain simulator builds on the energetic macroscopic representation (EMR), and incorporates models deduced from measurements on a Bahia proton exchange membrane fuel cell (PEMFC) and a Maxwell (R) supercapacitor bank. A semi-empirical electrochemical model predicts the steady-state PEMFC behavior, and circuit-equivalent models estimate the dynamics of the sources. We apply a rule-based power management system, where a low-pass filter splits the power between the sources, and an EMR controller block based on the inverse-model regulates the bus voltage. We focus on the trade-off between simplicity and phenomenological PEMFC considerations, which enable us to predict PEMFC electric dynamics, and we analyze the benefits of the energy management with respect to the oxygen-starvation prevention and reduction of startups and shutdowns. We evaluate the power distribution control under vehicular solicitations at a reduced scale of 1 kW, and then under a pulsed current train. We discuss the influence of the cutoff frequency value. The results prove the efficacy with which it reduces abrupt changes in the fuel cell, and demonstrates that this source will deliver until it reaches 80% of the required power.