Mitsubishi Electric Corporation

Nagaoka University of Technology

Yu Kawai

Takeshi Amimoto

Kikuo Izumi

Takahiro Kato

Yuki Itogawa

Tatsuya Okuda

Yusuke Higaki

Tomoaki Kimura

Kenji Fujiwara

Hirokazu Nakabayashi

Hidehito Yoshida

Jun-ichi Itoh

Hoai Nam Le

A first capacitor and a second capacitor are connected in series through a neutral point on the DC side of an inverter. A first converter receives an input voltage from a power source and outputs a first DC voltage to the first capacitor. A second converter receives a common input voltage and outputs a second DC voltage to the second capacitor. A control circuit controls the first converter such that the first DC voltage is controlled in accordance with a preset first voltage command value and controls the second converter such that the second DC voltage is controlled in accordance with a second voltage command value set equivalent to the first voltage command value.

Parallel conversion units without an output balancing circuit

An insulating transformer includes a plurality of sub-insulating transformers connected in series. Polarity directions of all sub-windings are identical. When a current I flows from a first main terminal to a third main terminal through the first sub-winding, an interphase capacitance, and the second sub-winding, excitation inductance of the first sub-winding and excitation inductance of the second sub-winding are configured to have opposite polarities.

Insulating transformer and power conversion device equipped with same

A power conversion device includes an inverter that generates an inverter voltage, a filter that receives the inverter voltage and outputs an output voltage, a detector that detects a DC component of the output voltage, a feedback controller that receives an AC voltage command and the DC component and determines an inverter voltage command such that the DC component is equal to a target value which is zero or a value corresponding to an offset error of the detector, and a PWM controller that receives the inverter voltage command and performs pulse width modulation control of the inverter. The feedback controller computes a compensation amount for compensating for the DC component and determines, as the inverter voltage command, the AC voltage command on which a product of an absolute value of a sine wave synchronized with a period of the AC voltage command and the compensation amount is superimposed.

Power conversion device

A power conversion device includes: a switching circuit; a signal generator to generate a switching signal of a switching element based on a first instruction value; a current controller to generate a second instruction value based on a deviation between a current target value and the current flowing through the switching circuit such that the current flowing through the switching circuit approaches the current target value; an operation mode detector to detect an operation mode based on the first instruction value; and a compensator to adjust the second instruction value so as to compensate a gain between the deviation and an amount of a change in the current of the switching circuit. The compensator adjusts the second instruction value so as to suppress a change in the gain based on the operation mode, and outputs the first instruction value.

In a DC/DC converter, in first power transmission in which power is transmitted from a first DC power source to a second DC power source, on/off drive of a positive electrode-side switching element and a negative electrode-side switching element is stopped in a third bridge circuit on the power-receiving side. When a power transmission amount by the first power transmission is smaller than a first reference value, a control circuit lowers the switching frequency of the switching elements of a first bridge circuit and a second bridge circuit on the power-transmitting side and a fourth bridge circuit on the power-receiving side, compared with when the power transmission amount is equal to or greater than the first reference value.

DC/DC converter and power conversion device

A first leg includes a first switch circuit disposed between a first node to which a positive electrode of a DC power supply is connected and a second node and a second switch circuit disposed between the second node and a third node. A first filter circuit includes a first capacitor. A bridge circuit includes a second leg and a third leg that are disposed in parallel between the first node and the third node. A clamp circuit includes a bidirectional switch disposed between a fourth node that is a midpoint of the second leg and a fifth node that is a midpoint of the third leg. A second filter circuit includes a first reactor and a second reactor.

Three-level power conversion device

The connection distance between a first snubber circuit and the positive electrode of a first semiconductor element is shorter than the connection distance between the first snubber circuit and the positive electrode of a third semiconductor element. The connection distance between the first snubber circuit and the negative electrode of a fourth semiconductor element is shorter than the connection distance between the first snubber circuit and the negative electrode of a second semiconductor element. The connection distance between a second snubber circuit and the positive electrode of the third semiconductor element is shorter than the wiring distance between the second snubber circuit and the positive electrode of the first semiconductor element, and the connection distance between the second snubber circuit and the negative electrode of the second semiconductor element is shorter than the wiring distance between the second snubber circuit and the negative electrode of the fourth semiconductor element.

A PWM control unit generates signals for controlling switching elements in respective legs based on the magnitude relationship between individual Duty commands for the respective legs and triangular wave carriers having different initial phases and having a common cycle, a current estimation unit acquires detected values from a current detector at a sampling cycle different from the carrier cycle and estimates the phase currents, and a current control unit adjusts Duty commands so that the estimated phase currents coincide with target values for the phase currents.

When an inverter and a converter are merely operated with their carrier waves synchronized with each other, current ripple of a smoothing capacitor connected therebetween might be increased. Accordingly, bipolar modulation PWM control is performed on the inverter, PWM control is performed on the converter, and the phase of the carrier wave for the inverter or the converter is shifted on the basis of AC output, whereby timings of currents flowing into the smoothing capacitor are made different from each other.

A parallel power supply device according to the present invention includes: a plurality of DC/DC converters connected in parallel to perform power conversion between a DC power supply and a common load; a voltage detector to detect a voltage of the common load; and a plurality of control circuits each to control a corresponding one of the plurality of DC/DC converters, wherein during parallel operation of the plurality of DC/DC converters, the plurality of control circuits control the plurality of DC/DC converters by proportional control using a same target voltage value and a same proportional gain, based on a voltage value of the common load detected by the voltage detector. Therefore, in the parallel power supply device in which the plurality of DC/DC converters are connected in parallel, the individual DC/DC converters can supply electric power to the load independently and equally.

Parallel power supply device

A power conversion device which reduces switching losses and stabilizes the output power. A switching-mode changer generates a reference signal for switching a mode of operation of the full-bridge circuit to a first switching mode or a second switching mode. In the first switching mode, an upper arm and a lower arm are switched synchronously, and a lower arm and an upper arm are non-conducting. In the second switching mode, the lower arm and the upper arm are switched synchronously, and the upper arm and the lower arm are non-conducting. The switching-mode changer adjusts the phase of the reference signal so that the reactive power is reduced.

A power conversion device is configured with a plurality of power conversion units multiplexed in parallel each having a power converter for converting a power between a power source and a common load. At least one of the power conversion units is provided with an operation manager for managing the operation of the power converter. The operation manager changes the proportional gain of a voltage adjuster that performs a proportional control by inputting the steady-state offset between a target voltage and a voltage to the load, to determine, by comparing a change in the steady-state offset with a change in the proportional gain, whether the at least one power conversion unit is in a single operation in which the other power conversion units are in no operation.

Power conversion device, power conversion system, and power conversion device operation method

In an electrical power conversion apparatus including DC power sources, electric power converter units, and an electric power sharing regulator for regulating electric power on a basis of individual electric power converter units, when the plurality of electric power converter units connects thereto a plurality of DC power sources on their input sides, and is connected in parallel with one another on their output sides, three threshold values of rated electric power, electric power of the highest efficiency, and electric power of allowable efficiency receive attention from an efficiency characteristic of each of the electric power converter units, and the adjustment of electric power shared by each of the electric power converter units is performed by the electric power sharing regulator so that better efficiency is achieved when the apparatus is viewed in its entirety.

Power conversion apparatus

In a control unit for drive-controlling a switching element unit of each power conversion device, a voltage correction amount calculation unit calculates a correction amount corresponding to voltage drop due to impedance between the switching element unit and filter reactor. A voltage command correcting unit corrects a voltage command generated by the voltage command generation unit, using the correction amount. Thus, for a power conversion devicethat has a small output impedance, correction is performed so as to increase the output impedance, and a PLL unit changes the frequency in accordance with active power calculated from output voltage and output current of the power conversion device, so as to uniform power allocations.

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Chiyoda-ku, Japan

Yu Kawai