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A polymer electrolyte membrane (PEM) fuel cell power system is a low voltage and high current power source that needs a DC/DC converter to boost the output voltage of the fuel cell system for high efficiency and better performance. The fuel cell power system can be connected, in parallel, to a grid via a voltage impressed pulse width modulation (PWM) converter that forms the DC source into a sinusoidal AC current and voltage. The system can be extended to supply not only active power, but also compensate reactive power by exploiting the energy stored in the capacitor. The paper proposes an integrated dynamic model for a PEM fuel cell system with a DC/DC PWM converter and the associated controls that can be used as a power source for a multifunctional compensator. Simulations are carried out to analyse the interactive effects of load currents on the components of the fuel cell power system. The electric load currents applied for the DC converter are obtained from the instantaneous power balance between the DC and the AC side of the AC/DC converter, where the AC currents generated are different currents derived by using a power theory from typical three-phase square waveforms on a grid. Included are also effects of the DC capacitance on the DC voltage variation at load currents applied. Integrated approach reveals a variety of possibilities to analyse and study interacting effects of electric loads on parameters of the fuel cell system components.