Abstract: In an uninterruptible power supply system, control sections of three uninterruptible power supply units are connected to one another by communication cables to configure one integrated control unit. The integrated control unit brings three switches into conduction if a bias feeding mode is selected by one arbitrary operation section and brings three switches into conduction if an inverter feeding mode is selected. Therefore, there is no need to separately provide an operation section and a control section for operating and controlling all of the uninterruptible power supply units.

Abstract: An uninterruptible power supply apparatus includes a cooler cooling a converter/chopper circuit and a cooler cooling a PWM inverter. The converter/chopper circuit and the cooler make up one integrated unit. Accordingly, a smaller apparatus can be achieved, compared with a conventional apparatus in which a cooler is provided for each of a converter and a chopper.

Abstract: A power conversion device includes an inverter for converting DC power to AC power to supply the AC power to a load, a converter for converting AC power from an AC power supply to DC power to supply the DC power to the inverter, a DC voltage converter for converting a voltage value of power stored in a storage battery to supply DC power from the storage battery to the inverter when power supply by the AC power supply is abnormal, and a filter which includes a reactor and a capacitor and removes harmonics generated by the inverter. The inverter includes a three-level circuit constituted of an arm and an AC switch.

Abstract: A power conversion apparatus includes an inverter for converting DC power to AC power for supply to a load, a converter for converting AC power from an AC power supply to DC power for supply to the inverter, and a DC voltage converter for converting a voltage value of power stored in a storage battery and supplying DC power from the storage battery to the inverter when power supply by the AC power supply is abnormal. The converter includes a first three-level circuit which is a multi-level circuit. Similarly, the DC voltage converter includes a second three-level circuit. A control device controls the first and second multi-level circuits to suppress potential fluctuation at a neutral point between first and second capacitors.

Abstract: A power conversion apparatus includes an inverter for converting DC power to AC power for supply to a load, a converter for converting AC power from an AC power supply to DC power for supply to the inverter, a DC voltage converter for converting a voltage value of power stored in a storage battery to supply DC power from the storage battery to the inverter when power supply from the AC power supply is faulty, and a filter including a reactor and a capacitor, for removing harmonics generated by the inverter. The inverter includes a three-level circuit which is a multi-level circuit.

Abstract: In a power conversion device, reactors in an AC input filter absorbing a voltage at a carrier frequency of a PWM converter and reactors in an AC output filter absorbing a voltage at a carrier frequency of a PWM inverter include one six-leg six-phase iron core reactor. Accordingly, the device can be reduced in size when compared with a case where the reactors are composed of two four-leg six-phase iron core reactors.

Abstract: In an uninterruptible power supply apparatus, a common mode current flowing from nodes (N1 to N3) to a line of a ground voltage (GND) through a stray capacitance (41) of a battery (40) is limited by a common mode reactor (34), and the low-level common mode current passing through the common mode reactor (34) is caused to flow to a virtual neutral line (NL) through a common mode capacitor (37). Therefore, the level of noise caused by the common mode current can be reduced.

Abstract: A three-level PWM converter (3) includes first to third fuses (F1R to F3R) having one terminals connected to a DC positive bus (13), a DC negative bus (14) and a DC neutral point bus (15), respectively, first and second IGBT elements (Q1R, Q2R) connected between respective ones of the other terminals of the first and second fuses (F1R, F2R) and an AC line (RL), an AC switch (Q3R, Q4R, D3R, D4R) connected between the AC line (RL) and the other terminal of the third fuse (F3R), first and second diodes (D1R, D2R) connected in anti-parallel to the first and second IGBT elements (Q1R, Q2R) respectively, a first capacitor (C1R) connected between the other terminals of the first and third fuses (F1R, F3R), and a second capacitor (C2R) connected between the other terminals of the second and third fuses (F2R, F3R).

Abstract: A device for controlling output voltage of a converter is provided. The input voltage V.sub.R is detected by means of a voltage detecting device and the phase .PHI. of the input voltage is detected by means of a phase synchronizing circuit. The detected phase is input to an AC sine wave reference oscillating circuit in order to obtain an AC sine wave reference signal having the same phase as input voltage. The output of an amplitude instruction generating circuit is multiplied by an AC sine wave reference signal by means of a multiplier in order to obtain a converter current instruction I.sub.A *. The input current I.sub.R detected by means of a current detecting device is differentiated by means of an approximation differentiator and only the resonance frequency component is detected by means of a band-pass filter. The detected resonance frequency component is multiplied by a gain K by means of a proportion device and the output os subtracted from the converter current instruction I.sub.

Abstract: A control apparatus for controlling a power converter includes a plurality of switching devices and enabling converted AC output to be obtained to supply arbitrary AC outputs to a load. A voltage command value generating device for generating a voltage command value is provided to command voltage to be transmitted from the power converter. A voltage control device is provided for controlling a plurality of switching devices of the power converter in accordance with a command voltage level. An electric current detection device is included for detecting an output electric current to be supplied from the power converter to the load. An electric current limiting device is provided for restricting the command voltage level to be supplied to the voltage control device in accordance with a value detected by the electric current detection device.

Abstract: Disclosed is a parallel power supply system including AC output inverters for controlling instantaneous values of output voltages by causing arms of respective inverters of the AC output inverters to effect switching in respective phases of the output voltages plural times during one cycle. A bus for connecting outputs on the inverters to a load so that a load current is shared by the inverters. A synchronous circuit for synchronizing the respective inverters by outputting common synchronous signals to the inverters. A detection circuit for detecting a cross current component of an electric current flowing between the respective inverters, and a control circuit for controlling the output voltages of the inverters to restrain the cross current component detected by the detection circuit.

Abstract: A parallel inverter system has a plurality of AC output inverters of an instantaneous voltage control type, a bus for connecting outputs of the inverters to a load so as to share the load current, a detection circuit for detecting a cross current component in a current flowing among the inverters, and an instantaneous voltage control circuit for controlling the output voltages of the inverters. In response to a signal in accordance with the detected cross current component from the detection circuit, the voltage control circuit inserts a virtual impedance between the inverters so as to suppress cross current.

Abstract: A method of operating a three-phase converter to produce a signal at an output frequency by decoupling and digitally sampling inverter input signals and load voltage signals and feeding the resultant phase signals back into the inverter. The phase voltages activate switching elements in the inverter to switch signals a plurality of times within one cycle of the output frequency thus changing electrical power at a first frequency, including direct current, to A.C. power at the output frequency.

Abstract: A control circuit for a 3-phase converter which is provided to control the 3-phase converter having an output filter provided with a current minor loop which controls an instantaneous value of the output current on the basis of a feedback signal obtained by converting the output current of the converter to d axis and q axis components by a synchronous revolutional coordinate system and a voltage major loop which controls the instantaneous value of the output voltage on the basis of a feedback signal obtained by converting the output voltage of the output filter to the d axis and q axis components; and realizes protection from overcurrent due to short-circuit of output.

Abstract: Apparatus for correcting a DC component of an output voltage in an inverter, where correction is performed so that DC component contained in AC output voltage of an inverter main circuit is reduced. The apparatus is provided with a current detecting circuit constituted by, for example, a saturable reactor installed within an inverter control circuit to control operation of switching elements constituting the inverter main circuit and connected in parallel to the output terminal side of the inverter main circuit for detecting the current of the AC output of the inverter, and a polarity discrimination circuit for automatically discriminating both positive and negative polarities in the current at the output side of the inverter main circuit detected by the current detecting circuit and for generating a DC component correcting signal in the inverter control circuit.

Abstract: A control circuit for a power conversion apparatus, e.g., inverter and cycloconverter, which produces sinusoidal alternating current (AC) power through multiple switching operations of switching devices within a cycle and supplies the power to a load. The control circuit includes a current control minor loop for controlling the instantaneous value of the output current of the power conversion apparatus in compliance with a current reference value which is determined as the sum of the load current component determined basing on the detected value of load current, and the modification current component produced by a voltage controller to current error of output line voltage of said power conversion apparatus with respect of a sinusoidal voltage reference, whereby the output voltage of the power conversion apparatus is controlled accurately to have less distortion against harmonics of the load.