Design and analysis of a system consisting of a variable-speed synchronous generator that supplies an active dc load (inverter) through a three-phase diode rectifier requires adequate modeling in both time and frequency domain. In particular, the system's control-loops, responsible for stability and proper impedance matching between generator and load, are difficult to design without an accurate small-signal model. A particularity of the described system is strong non-ideal operation of the diode rectifier, a consequence of the large value of generator's synchronous impedance. This non-ideal behavior influences both steady state and transient performance. This thesis presents a new, average model of the system. The average model accounts, in a detailed manner, for dynamics of generator and load, and for effects of the non-ideal operation of diode rectifier. The model is non-linear, but time continuous, and can be used for large- and small-signal analysis. The developed model was verified on a 150 kW generator set with inverter output, whose dc-link voltage control-loop design was successfully carried out based on the average model. / Master of Science