The present invention concerns a method and a device for controlling the voltage of a catenary supplying electric power to rolling stocks. The first rolling stock: —detects a traction command or a regeneration command of a second rolling stock in the neighborhood of first rolling stock, —increases the electric power supplied by the first rolling stock to means for heating, ventilation and air conditioning when a regeneration command of the second rolling stock is detected, —decreases the electric power supplied by the first rolling stock to the means for heating, ventilation and air conditioning when a traction command of the second rolling stock is detected.