A mathematical model of an AC/DC/AC power converter with an energy storage device has been developed on the basis of a bridge-element concept, that can be employed in the design phase for power quality and conducted emission analysis of micro grids. A prototype of a 5 kW AC/DC/AC power converter is built and a mockup of electric energy trading system is realized. Measurements conducted for three operating modes emulating electric energy transfer and power consumption in trading conditions have revealed a low voltage total harmonic distortion, not exceeding 1.3% for the tested cases.