Abstract: Parallel inverters without any communication buses and the controlling method thereof are provided. The parallel inverters are controlled by an instant voltage. Each inverter includes an output voltage waveform controller and a load-sharing controller. The output voltage waveform controller is connected to an output terminal of the inverter to control the waveform of an output voltage of the inverter. The load-sharing controller is connected to the output voltage waveform controller to control the load-sharing of the inverter and to make each inverter have the same phase, active power and reactive power without communications.

Abstract: A method of controlling an uninterruptible power supply apparatus (UPS) is provided. The UPS apparatus includes at least an AC input voltage, a DC input voltage and a single-phase AC/AC converter. The single-phase AC/AC converter includes an AC inductor, a bus capacitor, a boost arm, a common arm and a buck arm. The method includes steps of: controlling the bus voltage to have a DC component and full-wave rectifying component, and setting a bus voltage parameter K so that the bus voltage approaches to a full-wave rectifying voltage when K approaches to 1, wherein 0?K?1.

Abstract: An integrated converter having three-phase power factor correction is provided. The integrated converter includes two PFC circuits. Two DC/DC converters are controlled and switched by the integrated converter in accordance with a three-phase AC power source so as to convert the AC power source into a DC power source. The use of the elements in the integrated converter is efficient.

Abstract: A converting device with PFC and dc/dc converting functions is provided. The converting device includes a power source providing a dc voltage, an inverter having an input terminal electrically connected to the power source and an output terminal, a transformer having a primary winding electrically connected to the output terminal of the inverter and a secondary winding, a rectifier/filter circuit having an input terminal electrically connected to the secondary winding of the transformer and an output terminal, and a PFC converter coupled to the output terminal of the rectifier/filter circuit and having an input terminal receiving an ac input voltage. The converting device converts the ac input voltage into an ac output voltage when the ac input voltage is normal, and converts the dc voltage to output the ac output voltage with the cooperation of the inverter, the transformer, the rectifier/filter circuit and the PFC converter when the ac input voltage is abnormal.