A static transverter, of the type in which semi-conductor controlled rectifiers (thyristors) provide the commutation and in which variation of the direct current link circuit is used to control the output frequency, is provided with a buffer system connected to the direct current link circuit for keeping the transverter in operation during short power failures. Buffer capacitance is distributed in a series of capacitors respectively charged to different voltages by a separate source. These capacitors are connected in parallel to the direct current link circuit through diodes.