Power conversion device

Abstract

A power conversion device according to one embodiment of the present invention comprises: a transformation unit which converts power in both directions; a first element unit which is connected to one side of the transformation unit; and a second element unit which is connected to the other side of the transformation unit, wherein the first element unit includes a first inductor, a first capacitor, and a first switching unit which connects or disconnects the first capacitor, and the second element unit includes a second inductor, a second capacitor, and a second switching unit which connects or disconnects the second capacitor.

Description

power conversion device

[0001] The present invention relates to a power conversion device, and more specifically, to a power conversion device comprising a bidirectional LLC circuit.

[0002] Due to recent industrial development and the expansion of renewable energy, research is actively being conducted to improve the efficiency and density of power conversion devices.

[0003] These power conversion devices are used in applications such as microgrid systems, energy storage systems (ESS), electric vehicle OBCs (One Board Chargers) and battery charging / discharging systems, and fuel cell power conversion devices, and power conversion devices with a wide input / output voltage control range are required.

[0004] DC-DC converters, a power conversion device, are undergoing extensive research to improve manufacturing costs, stability, and efficiency. Among these, LLC circuits and CLLLC circuits are being utilized. However, CLLLC circuits face the challenge of achieving high voltage gain under wide input / output range conditions.

[0005] The technical problem to be solved by the present invention is to provide a power conversion device that constitutes a bidirectional LLC circuit.

[0006] In order to solve the above technical problem, a power conversion device according to an embodiment of the present invention includes a transformer for converting power in both directions; a first element unit connected to one side of the transformer unit; and a second element unit connected to the other side of the transformer unit, wherein the first element unit includes a first inductor, a first capacitor, and a first switching unit for connecting or disconnecting the first capacitor, and the second element unit includes a second inductor, a second capacitor, and a second switching unit for connecting or disconnecting the second capacitor.

[0007] Additionally, when the first switching unit connects the first capacitor, the second switching unit can disconnect the second capacitor.

[0008] Additionally, the first switching unit can connect one of the first capacitor or a first bypass path that bypasses the first capacitor.

[0009] Additionally, the second switching unit can connect one of the second capacitor or a second bypass path that bypasses the second capacitor.

[0010] Additionally, when the transformer converts power from one direction to the other, the first switching unit can connect the first capacitor, and the second switching unit can disconnect the second capacitor.

[0011] Additionally, when the transformer converts power from the other side to the one-side direction, the first switching unit can disconnect the first capacitor, and the second switching unit can connect the second capacitor.

[0012] Additionally, the first inductor may be connected to the (-) terminal on one side of the transformer, and the second inductor may be connected to the (-) terminal on the other side of the transformer.

[0013] In addition, the first element unit includes a first bypass path having one end connected to the (+) terminal of one side of the transformer unit, the first capacitor has one end connected to the (+) terminal of the one side of the transformer unit and is connected in parallel with the first bypass path, and the first switching unit has one end connected to one of the other end of the first bypass path or the other end of the first capacitor, and the other end can be connected to the first input / output unit.

[0014] In addition, the first element unit includes a first bypass path having one end connected to the (+) terminal of one side of the transformer unit, the first capacitor has one end connected to a tap terminal between the (+) terminal and the (-) terminal of the one side of the transformer unit, and the first switching unit has one end connected to one of the other end of the first bypass path or the other end of the first capacitor, and the other end can be connected to the first input / output unit.

[0015] In addition, the first element unit includes a first bypass path having one end connected to a tap terminal between the (+) terminal and the (-) terminal of the one side of the transformer unit, the first capacitor has one end connected to the (+) terminal of the one side of the transformer unit, and the first switching unit has one end connected to one of the other end of the first bypass path or the other end of the first capacitor, and the other end can be connected to the first input / output unit.

[0016] In addition, the first element unit may include a first bypass path having one end connected to the (+) terminal of one side of the transformer unit, the first capacitor having one end connected to a tap terminal between the (+) terminal and the (-) terminal of the one side of the transformer unit, and the first switching unit may include a 1-1 switching unit having one end connected to the other end of the first bypass path; and a 1-2 switching unit having one end connected to the other end of the first capacitor and connected in parallel with the 1-1 switching unit.

[0017] In addition, the first element unit may include a first bypass path having one end connected to a tap terminal between the (+) terminal and the (-) terminal of the one side of the transformer unit, the first capacitor having one end connected to the (+) terminal of the one side of the transformer unit, and the first switching unit may include a 1-1 switching unit having one end connected to the other end of the first bypass path; and a 1-2 switching unit having one end connected to the other end of the first capacitor and connected in parallel with the 1-1 switching unit.

[0018] In addition, the first capacitor may have one end connected to the (+) terminal of the one side of the transformer and the other end connected to the first input / output unit, and the first switching unit may have one end connected to the (+) terminal of the one side of the transformer and the other end connected to the first input / output unit, and may be connected in parallel with the first capacitor.

[0019] According to embodiments of the present invention, the circuit of a bidirectional LLC converter can be changed by opening or shorting the resonant capacitor (C) with a relay or semiconductor switch element. The voltage gain can be increased by removing one of the two resonant capacitors. In addition, the turns ratio of the transformer can be changed according to the operating mode by adding a terminal in the middle of the transformer winding and using a relay or semiconductor switch element. Through this, the turns ratio of the forward and backward directions can be configured differently to advantageously improve the voltage gain. An optimized bidirectional LLC can be designed by setting the relay or semiconductor switch element so that the LLC circuit becomes according to the direction in which power is transmitted. In addition, the bidirectional DCDC converter can be configured by minimizing the size and loss of magnetic elements (transformer and inductor) components.

[0020] When the proposed circuit is applied under the same circuit parameter conditions, the voltage gain is formed higher than that of the existing CLLLC, so a design that satisfies the desired wide input / output conditions is possible, and excessively high magnetizing current designed to satisfy a wide input / output voltage range can be suppressed. Since the magnetizing current can be designed to flow less under the same power conditions, the component size and loss of the magnetic element can be minimized, enabling the minimization of the size of the bidirectional DCDC converter product and the implementation of high efficiency.

[0021] FIG. 1 illustrates a power conversion device according to one embodiment of the present invention.

[0022] Figures 2 to 4 are block diagrams of a power conversion device according to an embodiment of the present invention.

[0023] Figure 5 illustrates a circuit of a power conversion device according to a comparative example of the present invention.

[0024] Figure 6 illustrates an example circuit implementation of a power conversion device according to an embodiment of the present invention.

[0025] Figures 7 to 10 illustrate power conversion devices according to various embodiments of the present invention.

[0026] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0027] However, the technical idea of ​​the present invention is not limited to some of the embodiments described, but can be implemented in various different forms, and within the scope of the technical idea of ​​the present invention, one or more of the components between the embodiments can be selectively combined or substituted for use.

[0028] In addition, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as having a meaning that can be generally understood by a person of ordinary skill in the technical field to which the present invention belongs, unless explicitly and specifically defined and described, and terms that are commonly used, such as terms defined in a dictionary, may be interpreted in consideration of the contextual meaning of the relevant technology.

[0029] Additionally, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0030] In this specification, the singular may also include the plural unless specifically stated otherwise in the phrase, and when it is described as “A and / or at least one (or more) of B, C”, it may include one or more of all combinations that can be combined with A, B, C.

[0031] Additionally, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and are not intended to limit the nature, order, or sequence of the components.

[0032] And, when a component is described as being 'connected', 'coupled', or 'connected' to another component, it may include not only cases where the component is 'connected', 'coupled', or 'connected' directly to the other component, but also cases where the component is 'connected', 'coupled', or 'connected' by another component between the component and the other component.

[0033] Additionally, when described as being formed or arranged "above" or "below" each component, "above" or "below" includes not only cases where the two components are in direct contact with each other, but also cases where one or more other components are formed or arranged between the two components. Furthermore, when expressed as "above" or "below," the meaning may include not only the upward direction but also the downward direction based on one component.

[0034] Fig. 1 illustrates a power conversion device according to one embodiment of the present invention. The power conversion device (100) according to one embodiment of the present invention is composed of a transformer (110), a first element (120), and a second element (130), and may include a first input / output unit (141), a first full bridge circuit unit (161), a second full bridge circuit unit (162), a second input / output unit (142), and a control unit (150).

[0035] A power conversion device (100) according to an embodiment of the present invention may be a power conversion device of an electric vehicle charging device. Here, the power conversion device (100) may be mounted on a power module of the electric vehicle charging device. The power module may receive AC power from the grid (50 / 60 Hz), convert it into DC power for charging an electric vehicle battery, and output it. Alternatively, the power module may receive DC power from an energy storage system (ESS), convert it into DC power for charging a battery, and output it. Power may be received from an external power source, such as a solar power generation module.

[0036] The power conversion device (100) according to an embodiment of the present invention may be a resonant converter, and may be a bidirectional LLC resonant converter or a bidirectional CLLLC resonant converter.

[0037] The transformer (110) converts power in both directions. The transformer (110) includes a transformer and may include one side and the other side. Power input to one side may be converted according to the turns ratio and output to the other side, and power input to the other side may be converted according to the turns ratio and output to one side.

[0038] The first element unit (120) is connected to one side of the transformer unit (110). The first element unit (120) can resonate input power and transmit it to one side of the transformer unit (110). The first element unit (120) can include a first inductor (121), a first capacitor (122), and a first switching unit (123). The first inductor (121) and the first capacitor (122) can form an LLC together with a coil on one side of the transformer unit (110) to achieve LLC resonance. The first inductor (121) can be a resonant inductor, and the first capacitor (122) can be a resonant capacitor. The first inductor (121) can be a magnetizing inductor.

[0039] The second element unit (130) is connected to the other side of the transformer unit (110). The second element unit (130) can resonate the input power and transmit it to the other side of the transformer unit (110). The second element unit (130) can include a second inductor (131), a second capacitor (132), and a second switching unit (133). The second inductor (131) and the second capacitor (132) can form an LLC together with the coil on the other side of the transformer unit (110) to achieve LLC resonance. The second inductor (131) can be a resonant inductor, and the second capacitor (132) can be a resonant capacitor. The second inductor (131) can be a magnetizing inductor.

[0040] When power is converted from one side of the transformer (110) to the other side or from the other side to one side, if both the first element (120) and the second element (130) have an LLC form, it can have the form of a CLLLC converter. This can have a form as shown in Fig. 5. It is configured in the form of a first full bridge circuit (23), a first resonant capacitor (22), a first resonant inductor (21), a transformer (10), a second resonant capacitor (32), a second resonant inductor (31), and a second full bridge circuit (33), so that CLLLC resonance can be achieved. It is difficult for a bidirectional CLLLC resonant converter to secure a voltage gain of 1.3 times or more under a wide input / output range condition. When designing to have a voltage gain of 1.3 times or more, a very large magnetizing current is required, which increases the saturation current level, increases the RMS current of the primary side current, and increases the size of the transformer and resonant inductor components.

[0041] A power conversion device (100) according to one embodiment of the present invention includes a CLLLC configuration in the configuration of the first element unit (120) and the second element unit (130), but can operate as an LLC resonant converter depending on the operation of the first switching unit (123) and the second switching unit (133).

[0042] The first switching unit (123) can connect or disconnect the first capacitor (122), and the second switching unit (133) can connect or disconnect the second capacitor (132).

[0043] When the first switching unit (123) connects the first capacitor (122), the second switching unit (133) can disconnect the second capacitor (132). When the transformer (110) converts power from one direction to the other, the first switching unit (123) can connect the first capacitor (122), and the second switching unit (133) can disconnect the second capacitor (132). Through this, the first inductor (121) and the first capacitor (122) on one side, together with the coil on one side of the transformer (110), form an LLC resonant unit, and the connection of the second capacitor (132) on the other side is disconnected, so that resonance does not occur on the other side, which is the output side.

[0044] Conversely, when the second switching unit (133) connects the second capacitor (132), the first switching unit (123) can disconnect the first capacitor (122). When the transformer (110) converts power from the other side to one direction, the second switching unit (133) can connect the second capacitor (132), and the first switching unit (123) can disconnect the first capacitor (122). Through this, the second inductor (131) and the second capacitor (132) on the other side can form an LLC resonance unit together with the coil on the other side of the transformer (110), and the connection of the first capacitor (122) on one side can be disconnected so that resonance does not occur on the one side, which is the output side.

[0045] Through this, it can be operated as a bidirectional LLC resonant converter.

[0046] The first switching unit (123) can connect either the first capacitor (122) or the first bypass path (124) that bypasses the first capacitor (122). The first switching unit (123) can operate so that the first capacitor (122) is connected to the input side when one side becomes the input side, and can bypass the first capacitor (122) when one side becomes the output side. As shown in Fig. 2, when power is input through the first input / output unit (141), the first switching unit (123) can connect the first capacitor (122), and when power is output through the first input / output unit (141), the first switching unit (123) can disconnect the first capacitor (122) and form the first bypass path (124).

[0047] The second switching unit (133) can connect either the second capacitor (132) or the second bypass path (134) that bypasses the second capacitor (132). The second switching unit (133) can operate to connect the second capacitor (132) to the input side when the other side becomes the input side, and can bypass the second capacitor (132) when the other side becomes the output side. As shown in Fig. 2, when power is input through the second input / output unit (142), the second switching unit (133) can connect the second capacitor (132), and when power is output through the second input / output unit (142), the second switching unit (133) can disconnect the second capacitor (132) and form the second bypass path (134).

[0048] The control unit (150) can control the operation of the first switching unit (123) and the second switching unit (133). It can measure the voltage, current, and power of the first input / output unit (141) and the second input / output unit (142), determine the input / output direction, or control the first switching unit (123) and the second switching unit (133) according to a command received from the outside to configure a one-way LLC resonant converter. The control unit (150) can be an MCU.

[0049] The first inductor (121) may be connected to the (-) terminal on one side of the transformer (110), and the second inductor (131) may be connected to the (-) terminal on the other side of the transformer (110). The LLC resonance configuration is configured by whether the first capacitor (122) and the second capacitor (132) are connected, and the first inductor (121) and the second inductor (131) may be connected to the (-) terminals on both sides of the transformer (110), respectively. Alternatively, the first switching unit (123) may connect or disconnect the first inductor (121), and the second switching unit (133) may connect or disconnect the second inductor (131).

[0050] The first switching unit (123) and the first capacitor (122) of the first element unit (120) can be connected to the transformer unit (110) in various embodiments. Various embodiments will be described below.

[0051] The first element unit (120) includes a first bypass path (124) having one end connected to a (+) terminal of one side of the transformer unit (110), the first capacitor (122) has one end connected to a (+) terminal of one side of the transformer unit (110) and is connected in parallel with the first bypass path (124), and the first switching unit (123) has one end connected to either the other end of the first bypass path (124) or the other end of the first capacitor (122), and the other end can be connected to the first input / output unit (141). As shown in Fig. 2, the first capacitor (122) and the first bypass path (124) can be connected in parallel to one side of the transformer unit (110), and the first switching unit (123) can be connected to one of them to form a path.

[0052] The first element unit (120) includes a first bypass path (124) whose end is connected to the (+) terminal of one side of the transformer unit (110), and the first capacitor (122) may have one end connected to a tap terminal between the (+) terminal and the (-) terminal of one side of the transformer unit (110). Here, the tap terminal is a terminal formed by branching the winding of the transformer unit (110) in the middle, and the first capacitor (122) may be connected to the tap terminal. The first switching unit (123) may have one end connected to either the other end of the first bypass path (124) or the other end of the first capacitor (122), and the other end connected to the first input / output unit (141). When the first capacitor (122) is connected, it is connected to one side of the transformer (110) through the tap terminal of the transformer (110), so the number of turns of the input side winding decreases depending on the branch position of the tap terminal, and thus the turns ratio may increase. In this case, when power is applied to the other side of the transformer (110), the first capacitor (122) is not connected, and the first bypass path (124) is connected. In this case, all the windings of the transformer (110) are connected, so that the turns ratio may vary depending on the direction of power conversion. Through this, the turns ratios in the forward direction and the backward direction may be configured differently to optimize the voltage gain.

[0053] The first element (120) includes a first bypass path (124) whose end is connected to a tap terminal between the (+) terminal and the (-) terminal of one side of the transformer (110), the first capacitor (122) whose end is connected to the (+) terminal of one side of the transformer (110), and the first switching unit (123) whose end is connected to one of the other end of the first bypass path (124) or the other end of the first capacitor (122), and whose other end can be connected to the first input / output unit (141). In this case, when the first capacitor (122) is connected, it is connected to one side of the transformer (110) through the entire winding of the transformer (110), and when power is applied to the other side of the transformer (110), the first capacitor (122) is not connected, and the first bypass path (124) is connected, so that the number of turns of the output side winding is reduced depending on the branch position of the tap terminal, and thus the turns ratio can be reduced. In other words, the turns ratio can vary depending on the conversion direction of the power.

[0054] The first element unit (120) includes a first bypass path (124) whose end is connected to a (+) terminal of one side of the transformer unit (110), a first capacitor (122) whose end is connected to a tap terminal between a (+) terminal and a (-) terminal of one side of the transformer unit (110), and a first switching unit (123) which may include a 1-1 switching unit (125) whose end is connected to the other end of the first bypass path (124) and a 1-2 switching unit (126) whose end is connected to the other end of the first capacitor (122) and which is connected in parallel with the 1-1 switching unit (125). The first capacitor (122) is connected to the tap terminal, so that the turns ratio may vary depending on the input / output direction. The first switching unit (123) may be composed of a 1-1 switching unit (125) and a 1-2 switching unit (126), as shown in FIG. 3.

[0055] When the first switching unit (123) is connected to either the first capacitor (122) or the first bypass path (124) as shown in Fig. 2, the first switching unit (123) may be configured as a relay with a circuit in which the contact points change. When the first switching unit (123) includes the 1-1 switching unit (125) and the 1-2 switching unit (126) as shown in Fig. 3, the 1-1 switching unit (125) and the 1-2 switching unit (126) perform on / off operations, and may be configured as semiconductor switches such as MOSFETs as well as relays. In addition, various switching elements may be included.

[0056] The first element unit (120) includes a first bypass path (124) having one end connected to a tap terminal between the (+) terminal and the (-) terminal of one side of the transformer unit (110), the first capacitor (122) having one end connected to the (+) terminal of the one side of the transformer unit (110), and the first switching unit (123) may include a 1-1 switching unit (125) having one end connected to the other end of the first bypass path (124) and a 1-2 switching unit (126) having one end connected to the other end of the first capacitor (122) and connected in parallel with the 1-1 switching unit (125). The first bypass path (124) is connected to the tap terminal, so that the turns ratio may vary depending on the input / output direction. The first switching unit (123) may be composed of a first-first switching unit (125) and a first-second switching unit (126), as shown in FIG. 3.

[0057] The first capacitor (122) has one end connected to the (+) terminal of one side of the transformer (110) and the other end connected to the first input / output unit (141), and the first switching unit (123) has one end connected to the (+) terminal of the one side of the transformer (110) and the other end connected to the first input / output unit (141), and can be connected in parallel with the first capacitor (122). As shown in Fig. 4, the first switching unit (123) can form a bypass path without a separate first bypass path (124) connected in parallel with the first capacitor (122). When the first switching unit (123) is turned on to form a bypass path, the first capacitor (122) connected in parallel with the first switching unit (123) does not operate, so that the circuit can be configured as if the first capacitor (122) is not connected.

[0058] The second switching unit (133) and the second capacitor (132) of the second element unit (130) may be connected to the transformer unit (110) in various embodiments. The configuration of the second element unit (130) may be configured to correspond to one of the configurations of the first element unit (120) according to the various embodiments described above.

[0059] At this time, the configuration of the second element unit (130) may correspond to the configuration of the first element unit (120), or may be configured according to another embodiment of the first element unit (120). As shown in Fig. 6, the first element unit (120) includes a first bypass path (124) whose end is connected to a (+) terminal on one side of the transformer unit (110), a first capacitor (122) whose end is connected to a (+) terminal on one side of the transformer unit (110) and is connected in parallel with the first bypass path (124), and a first switching unit (123) whose end is connected to one of the other end of the first bypass path (124) or the other end of the first capacitor (122), and whose other end may be connected to the first input / output unit (141). The second element unit (130) includes a second bypass path (134) having one end connected to the (+) terminal of the other side of the transformer unit (110), the second capacitor (132) may have one end connected to a tap terminal between the (+) terminal and the (-) terminal of the other side of the transformer unit (110), and the second switching unit (133) may have one end connected to either the other end of the second bypass path (134) or the other end of the second capacitor (132), and the other end connected to the second input / output unit (142). A first full bridge circuit unit (161) may be connected to the first input / output unit (141), and a second full bridge circuit unit (162) may be connected to the second input / output unit (142). The first full bridge circuit unit (161) and the second full bridge circuit unit (162) are configured as a full bridge and can supply power to the first element unit (120) or the second element unit (130) that forms an LLC resonant unit through a switching operation.

[0060] As described above, the first element unit (120) can be configured in various embodiments, as shown in FIGS. 7 and 8, depending on the connection relationship between the first capacitor (122) and the first bypass path (124), the connection relationship with the transformer (110) of the first capacitor (122) or the first bypass path (124), the connection relationship with the first switching unit (123) of the first capacitor (122) or the first bypass path (124), and the type and number of the first switching unit (123).

[0061] The second element (130) may also be configured in various embodiments, as shown in FIGS. 9 and 10, depending on the connection relationship between the second capacitor (132) and the second bypass path (134), the connection relationship with the transformer (110) of the second capacitor (132) or the second bypass path (134), the connection relationship with the second switching unit (133) of the second capacitor (132) or the second bypass path (134), and the type and number of the second switching unit (133), corresponding to the first element (120).

[0062] A power conversion device (100) according to an embodiment of the present invention can configure a bidirectional LLC converter by combining a first element (120) of one of the embodiments of FIGS. 7 and 8 and a second element (130) of one of the embodiments of FIGS. 9 and 10. For example, 710+910, 710+920, 710+930, 710+940, 710+950, ​​710+960, 720+910, 720+920, 720+930, 720+940, 720+950, ​​720+960, 730+910, 730+920, 730+930, 730+940, 730+950, ​​730+960, 740+910, 740+920, 740+930, 740+940, 740+950, ​​740+960, 750+910, 750+920, It can be composed of one of the following combinations: 750+930, 750+940, 750+950, ​​750+960, 760+910, 760+920, 760+930, 760+940, 760+950, ​​760+960.

[0063] As described above, a bidirectional LLC converter can be implemented by connecting only one of the first capacitor (122) and the second capacitor (132), which are resonant capacitors, according to the power conversion direction. That is, the circuit of the bidirectional LLC converter can be changed by opening or shorting the resonant capacitor (C) with a relay or semiconductor switch element, and the voltage gain can be increased by removing one of the two resonant capacitors. In addition, a terminal can be added in the middle of the transformer winding and the turns ratio of the transformer can be changed according to the operating mode by using a relay or semiconductor switch element. Through this, the turns ratios of the forward and backward directions can be configured differently to advantageously improve the voltage gain. An optimized bidirectional LLC can be designed by setting the relay or semiconductor switch element so that the LLC circuit is configured according to the direction in which the power is transmitted. In addition, the bidirectional DCDC converter can be configured by minimizing the size and loss of the magnetic elements (transformer and inductor) components.

[0064] When the proposed circuit is applied under the same circuit parameter conditions, the voltage gain is formed higher than that of the existing CLLLC, so a design that satisfies the desired wide input / output conditions is possible, and excessively high magnetizing current designed to satisfy a wide input / output voltage range can be suppressed. Since the magnetizing current can be designed to flow less under the same power conditions, the component size and loss of the magnetic element can be minimized, enabling the minimization of the size of the bidirectional DCDC converter product and the implementation of high efficiency.

[0065] Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from the essential characteristics of the above-described description. Therefore, the disclosed methods should be considered illustrative rather than restrictive. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. A transformer that converts power in both directions; A first element connected to one side of the above transformer; and Including a second element connected to the other side of the above transformer, The above first component, It comprises a first inductor, a first capacitor, and a first switching unit for connecting or disconnecting the first capacitor, The above second component, A power conversion device comprising a second inductor, a second capacitor, and a second switching unit for connecting or disconnecting the second capacitor.

2. In paragraph 1, A power conversion device in which, when the first switching unit connects the first capacitor, the second switching unit disconnects the second capacitor.

3. In paragraph 1, The above first switching unit, A power conversion device connecting one of the first capacitor or a first bypass path bypassing the first capacitor.

4. In paragraph 1, The above second switching unit, A power conversion device connecting one of the second capacitors or a second bypass path bypassing the second capacitor.

5. In paragraph 1, When the above transformer converts power from one side to the other direction, A power conversion device in which the first switching unit connects the first capacitor and the second switching unit disconnects the second capacitor.

6. In paragraph 1, When the above transformer converts power from the other side to the one side, A power conversion device in which the first switching unit disconnects the first capacitor and the second switching unit connects the second capacitor.

7. In paragraph 1, The above first inductor is connected to the (-) terminal on one side of the above transformer, A power conversion device in which the second inductor is connected to the (-) terminal on the other side of the transformer.

8. In paragraph 1, The above first component, Including a first bypass path having one end connected to the (+) terminal of the one side of the above transformer, The above first capacitor, First, it is connected to the (+) terminal of the above-mentioned one side of the above-mentioned transformer and is connected in parallel with the first bypass path, A power conversion device in which one end of the first switching unit is connected to the other end of the first bypass path or the other end of the first capacitor, and the other end is connected to the first input / output unit.

9. In paragraph 1, The above first component, Including a first bypass path having one end connected to the (+) terminal of the one side of the above transformer, The above first capacitor has one end connected to a tap terminal between the (+) terminal and the (-) terminal of the one side of the transformer, A power conversion device in which one end of the first switching unit is connected to the other end of the first bypass path or the other end of the first capacitor, and the other end is connected to the first input / output unit.

10. In paragraph 1, The above first component, The above transformer includes a first bypass path having one end connected to a tap terminal between the (+) terminal and the (-) terminal of the one end, The first capacitor has one end connected to the (+) terminal of one side of the transformer, A power conversion device in which one end of the first switching unit is connected to the other end of the first bypass path or the other end of the first capacitor, and the other end is connected to the first input / output unit.

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