This paper focuses on the way to manage the fuel cell (FC) produced energy toward the electrical grid. Two different topologies are described and analysed. The first one associates a DC/DC converter and a PWM inverter. The second one is a hybrid system: an ultracapacitor bank, connected to the DC bus through a chopper, is used in addition to the FC system and acts as a buffer peak power source. The paper describes the models of the FC system, the converters and the grid. Then control laws are laid on in order to optimise the active and reactive power transfers. Concerning the connection to the grid, the three-phase DC/AC converter includes two control loops; the inner current control loop is optimised using a resonant corrector, the outer loop is based on a power flow transfer control. The presented results deal with the dynamic and static behaviours as well as with the interaction between the generator and the grid. The generated harmonics are also analysed.