Abstract: A power supply system composed by inverters (105, 110, 115) connected in parallel, applicable mainly in uninterruptible power suppliers (UPS). The parallelism provides the capacity of increasing power through the connection of new inverters to the system; and reliability, once defective inverters can be removed of the system without interrupting the power supply, since the total capacity of the remaining inverters is not less than the capacity required by the loads. In a parallelism scenario, one of the inverters assumes the master role, operating as a voltage source, while the other inverters assume the slave role, operating as current sources. The master informs the reference current of each phase to the slaves through a communication bus (150) between inverters (105, 110, 115). The reference is informed as a relative value to master nominal power, allowing the use of inverters with different power in the system and a load distribution proportional to the nominal power of each inverter (105, 110, 115).