US-12620913-B2 - Power conversion device including a plurality of converter units and a bidirectional DC/DC converter connected between two dc outputs of a plurality of dc outputs of the plurality of converter units

Abstract

A power conversion device charges a plurality of storage devices and includes a plurality of converter units that receives AC power and outputs DC power, and a bidirectional DC/DC converter connected between two DC outputs of a plurality of DC outputs of the plurality of converter units. The bidirectional DC/DC converter transmits at least a part of output power of the converter unit at one DC output from the one DC output to the other DC output of the two DC outputs according to required power of the plurality of storage devices.

Inventors

• Abhijit Choudhury
• Takae Shimada

Assignees

• HITACHI, LTD.

Dates

Publication Date

20260505

Application Date

20231012

Priority Date

20221109

Claims (12)

1. 1 . A power conversion device configured to charge a plurality of storage devices, the power conversion device comprising: a plurality of converter units each configured to receive AC power and output DC power; and a bidirectional DC/DC converter connected between two DC outputs of a plurality of DC outputs of the plurality of converter units, wherein the bidirectional DC/DC converter transmits at least a part of output power of the converter unit at one DC output from the one DC output to another DC output of the two DC outputs according to required power of the plurality of storage devices, and the power conversion device includes N (N≥3) converter units, and only N−1 bidirectional DC/DC converters.
2. 2 . The power conversion device according to claim 1 , wherein the output power from each of the plurality of DC outputs is equal.
3. 3 . The power conversion device according to claim 2 , wherein a value of the output power is an average value of the required power of the plurality of storage devices.
4. 4 . The power conversion device according to claim 3 , wherein a value of the required power of the storage device connected to the other DC output is larger than the average value.
5. 5 . The power conversion device according to claim 2 , wherein a rated power capacity of the bidirectional DC/DC converter is 50% or more of a rated power capacity of the converter unit and is smaller than the rated power capacity of the converter unit.
6. 6 . The power conversion device according to claim 1 , wherein the bidirectional DC/DC converter is of an isolated type.
7. 7 . The power conversion device according to claim 1 , wherein the part of the output power is transmitted by a plurality of the bidirectional DC/DC converters of the N−1 bidirectional DC/DC converters.
8. 8 . The power conversion device according to claim 1 , wherein AC inputs of the plurality of converter units are connected in series to each other, and the AC input and the DC output of each of the plurality of converter units is electrically isolated from each other.
9. 9 . The power conversion device according to claim 1 , wherein the plurality of storage devices are charged at different charging speeds.
10. 10 . The power conversion device according to claim 1 , wherein the plurality of storage devices are charged and discharged with each other by the bidirectional DC/DC converter.
11. 11 . The power conversion device according to claim 1 , wherein DC power of the plurality of storage devices is further supplied to a power supply side configured to supply the AC power via the plurality of converter units.
12. 12 . A method of controlling a power conversion device configured to charge a plurality of storage devices, the power conversion device comprising: a plurality of converter units that each receive AC power and output DC power; and a bidirectional DC/DC converter connected between two DC outputs of a plurality of DC outputs of the plurality of converter units, the method comprising: calculating an average value of required power of the plurality of storage devices; and controlling output power of the bidirectional DC/DC converter based on the required power and the average value, wherein the power conversion device includes N (N≥3) converter units, and N−1 bidirectional DC/DC converters.

Description

CLAIM OF PRIORITY The present application claims priority from Japanese application serial no. 2022-179453, filed on Nov. 9, 2022, the content of which is hereby incorporated by reference into this application. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device including a plurality of outputs. 2. Description of the Related Art With the spread of renewable energy sources in a power system and progress of development of charging facilities for electric vehicles, a middle-to-high voltage isolated AC/DC converter is becoming commonly used as a power conversion device for interconnecting a high-voltage AC power supply and a low-voltage DC bus. In a case where outputting DC power to a plurality of loads (for example, electric vehicles), the isolated AC/DC converter includes a plurality of converter cells each including an isolated AC/DC converter circuit. As a conventional technique related to such an isolated AC/DC converter, a technique described in WO 2019/234988 is known. In the technique described in WO 2019/234988 A, AC inputs of the plurality of converter cells each including the isolated AC/DC converter circuit are connected in series to each other. The AC input connected in series is directly connected to a high-voltage AC power supply system without passing through a transformer. Each converter cell includes an AC/DC conversion circuit having an AC input, a smoothing capacitor connected to a DC side of the AC/DC conversion circuit, a DC/AC conversion circuit having an AC side connected to a DC side of the AC/DC conversion circuit, a radio frequency transformer having a primary winding connected to an AC side of the DC/AC conversion circuit, and an AC/DC conversion circuit having a DC side connected to a secondary winding of the radio frequency transformer and having an AC output. DC outputs of the plurality of converter cells are connected to a plurality of input ports of a switch, respectively. In the switch, open/close units are connected in a matrix form between the plurality of input ports and a plurality of output ports. Therefore, by operating the open/close unit, the DC output of each converter cell is connected to any output port. In addition, any number of input ports are connected to the output port to which the load is connected according to the power required by the load. Each converter cell supplies DC power to a storage battery of the electric vehicle as the load connected to the output port to charge the storage battery. SUMMARY OF THE INVENTION In the above-described conventional technique, there is a problem that an installation space of a switch to which the open/close units are connected in a matrix is required, and a power loss increases due to operating power of the switch. Therefore, the present invention provides a power conversion device capable of charging a plurality of storage devices according to required power without using a switch, and a method of controlling the power conversion device. In order to solve the above problems, a power conversion device according to the present invention charges a plurality of storage devices, the power conversion device including a plurality of converter units that receives AC power and outputs DC power, and a bidirectional DC/DC converter connected between two DC outputs of a plurality of DC outputs of the plurality of converter units. The bidirectional DC/DC converter transmits at least a part of output power of the converter unit at one DC output from the one DC output to the other DC output of the two DC outputs according to required power of the plurality of storage devices. In order to solve the above problems, a method of controlling a power conversion device according to the present invention is a method of controlling a power conversion device that charges a plurality of storage devices, the power conversion device including a plurality of converter units that receives AC power and outputs DC power; and a bidirectional DC/DC converter connected between two DC outputs of a plurality of DC outputs of the plurality of converter units. The method calculates an average value of required power of the plurality of storage devices, controls output power of the plurality of storage devices based on the average value, and controls output power of the bidirectional DC/DC converter based on the required power and the average value. According to the present invention, by providing a bidirectional DC/DC converter, a plurality of storage devices can be charged according to required power. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagram illustrating a configuration of a power conversion device for charging an electric vehicle according to an embodiment; FIG. 2 is a schematic functional block diagram illustrating a flow of power in t