Power conversion device

Abstract

The present disclosure relates to a power conversion device. The three switching elements of the upper arm and the three switching elements of the lower arm of the first inverter are composed of first semiconductor switching elements, the three switching elements of the upper arm and the switching elements for line connection of the second inverter are composed of three switching elements of the lower arm of the second inverter are composed of second semiconductor switching elements different from the first semiconductor switching elements. A semiconductor switching element having superior conduction characteristics than the second semiconductor switching element is used as the first semiconductor switching element.

Description

Technical Field

[0001] The present disclosure relates to a power conversion device, and more particularly, to a power conversion device having two inverters for driving an open-winding motor. Background Art

[0002] In the past, as such a power conversion device, a power conversion device has been proposed, which includes: a first inverter connected to a power line connected to a battery and connected to each phase of an open-circuit winding motor; a second inverter connected to the power line and connected to each phase of the open-circuit winding motor; and two switches installed on the positive and negative sides of the power line between the first inverter and the second inverter (for example, refer to Japanese Patent Application Laid-Open No. 2018-014829). The power conversion device switches between star connection drive in which star control is performed when the two switches are open and delta connection drive in which delta control is performed when the two switches are closed. Summary of the invention

[0003] However, in the above-mentioned power conversion device, the upper arm or the lower arm of the switch or the second inverter is always set to the on state during star connection driving, so that power loss occurs due to the conduction resistance of the switching element that is always in the on state, or the switching element overheats, etc.

[0004] A main object of the power conversion device of the present disclosure is to suppress power loss when an open winding motor is driven in star connection.

[0005] The power conversion device of the present disclosure adopts the following means to achieve the above-mentioned main object.

[0006] The power conversion device disclosed in the present invention is connected to a power storage device and a three-phase open-circuit winding motor, and is characterized in that the power conversion device comprises:

[0007] a first inverter connected to a power line connected to the power storage device and connected to each phase of the open winding motor;

[0008] a second inverter connected to the power line and to each phase of the open winding motor; and

[0009] a line connection switching element installed on a positive-electrode side line of the power line between the first inverter and the second inverter,

[0010] The three switching elements of the upper arm and the three switching elements of the lower arm of the first inverter, the three switching elements of the upper arm of the second inverter, and the line connection switching element are constituted by the first semiconductor switching element.

[0011] The three switching elements of the lower arm of the second inverter are constituted by a second semiconductor switching element different from the first semiconductor switching element,

[0012] As the first semiconductor switch element, a semiconductor switch element having a better conduction characteristic than the second semiconductor switch element is used.

[0013] The power conversion device disclosed in the present invention comprises: a first inverter connected to a power line connected to a power storage device and connected to each phase of an open-circuit winding motor; a second inverter connected to the power line and connected to each phase of the open-circuit winding motor; and a line connection switch element installed on the positive side line of the power line between the first inverter and the second inverter. Moreover, the three switch elements of the upper arm and the three switch elements of the lower arm of the first inverter, the three switch elements of the upper arm of the second inverter, and the line connection switch element are constituted by the first semiconductor switch element. The three switch elements of the lower arm of the second inverter are constituted by the second semiconductor switch element different from the first semiconductor switch element. As the first semiconductor switch element, a semiconductor switch element having a better conduction characteristic than the second semiconductor switch element is used. When the line connection switching element is turned off, the three switching elements of the upper arm of the second inverter are turned on, and the three switching elements of the lower arm of the second inverter are turned off, the switching elements of the first inverter are switched on, and when the open winding motor is driven in star connection, the first semiconductor switching element with excellent conduction characteristics is used as the three switching elements of the upper arm of the second inverter. As a result, compared with the case where the second semiconductor switching element is used as the three switching elements of the upper arm of the second inverter, power loss can be suppressed. In addition, when the line connection switching element is turned on, the switching elements of the first inverter are switched on, and the switching elements of the second inverter are switched on, and when the open winding motor is driven in delta connection, the first semiconductor switching element with excellent conduction characteristics is used as the line connection switching element. As a result, compared with the case where the second semiconductor switching element is used as the line connection switching element, power loss can be suppressed. It should be noted that the second semiconductor switching element is usually cheaper than the first semiconductor switching element with excellent conduction characteristics. Therefore, by configuring the three switching elements of the lower arm of the second inverter with the second semiconductor switching elements, the power conversion device can be made cheaper than when the three switching elements of the lower arm of the second inverter are also configured with the first semiconductor switching elements.

[0014] In addition, the power conversion device of the present disclosure is a power conversion device connected to a power storage device and a three-phase open winding motor, and the power conversion device includes:

[0015] a first inverter connected to a power line connected to the power storage device and connected to each phase of the open winding motor;

[0016] a second inverter connected to the power line and to each phase of the open winding motor; and

[0017] a line connection switching element installed on a negative-electrode line of the power line between the first inverter and the second inverter,

[0018] The three switching elements of the upper arm and the three switching elements of the lower arm of the first inverter, the three switching elements of the lower arm of the second inverter, and the line connection switching element are constituted by the first semiconductor switching element.

[0019] The three switching elements of the upper arm of the second inverter are constituted by a second semiconductor switching element different from the first semiconductor switching element,

[0020] As the first semiconductor switch element, a semiconductor switch element having a better conduction characteristic than the second semiconductor switch element is used.

[0021] In addition, the power conversion device disclosed in the present invention includes: a first inverter connected to a power line connected to a power storage device and connected to each phase of an open-circuit winding motor; a second inverter connected to the power line and connected to each phase of the open-circuit winding motor; and a line connection switching element installed on the positive side line of the power line between the first inverter and the second inverter. Moreover, the three switching elements of the upper arm and the three switching elements of the lower arm of the first inverter, the three switching elements of the lower arm of the second inverter, and the line connection switching element are constituted by the first semiconductor switching element. The three switching elements of the upper arm of the second inverter are constituted by a second semiconductor switching element different from the first semiconductor switching element. As the first semiconductor switching element, a semiconductor switching element having a better conduction characteristic than the second semiconductor switching element is used. When the line connection switching element is turned off, the three switching elements of the lower arm of the second inverter are turned on, and the three switching elements of the upper arm of the second inverter are turned off, the switching elements of the first inverter are switched on, and when the open winding motor is driven in star connection, the first semiconductor switching element with excellent conduction characteristics is used as the three switching elements of the lower arm of the second inverter. As a result, compared with the case where the second semiconductor switching element is used as the three switching elements of the lower arm of the second inverter, power loss can be suppressed. In addition, when the line connection switching element is turned on, the switching elements of the first inverter are switched on, and the switching elements of the second inverter are switched on, and when the open winding motor is driven in delta connection, the first semiconductor switching element with excellent conduction characteristics is used as the line connection switching element. As a result, compared with the case where the second semiconductor switching element is used as the line connection switching element, power loss can be suppressed. It should be noted that in this case, the second semiconductor switching element is usually cheaper than the first semiconductor switching element with excellent conduction characteristics. Therefore, by configuring the three switching elements of the lower arm of the second inverter with the second semiconductor switching elements, the power conversion device can be made cheaper than when the three switching elements of the lower arm of the second inverter are also configured with the first semiconductor switching elements.

[0022] In the power conversion device disclosed in the present invention, the first semiconductor switch element may also be a switch element based on a wide bandgap semiconductor using gallium nitride (GaN) or silicon carbide (SiC). The second semiconductor switch element may also be a switch element based on a semiconductor using silicon (Si). In this case, the first semiconductor switch element may also be a SiC-MOSFET (Si C-Metal Oxide Semiconductor Field Effect Transistor). The second semiconductor switch element may also be a Si-IGBT (Si-Insulated Gate Bipolar Transistor). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0024] Figure 1 1 is a schematic structural diagram showing a structure of a drive device 20 including a power conversion device 30 as one embodiment of the present disclosure;

[0025] Figure 2 is an explanatory diagram showing an example of the on-off state of the switching element and the flow of current when the open winding motor 40 is driven in star connection by the power conversion device 30; and

[0026] Figure 3 1 is a schematic structural diagram showing the structure of a drive device 20B including a power conversion device 30B according to a modified example. DETAILED DESCRIPTION

[0027] Next, a mode (embodiment) for carrying out the present disclosure will be described. Figure 1 1 is a schematic structural diagram showing a structure of a drive device 20 including a power conversion device 30 as one embodiment of the present disclosure. The drive device 20 includes a battery 22 , a power conversion device 30 , and an open winding motor 40 .

[0028] Battery 22 is configured as a lithium ion secondary battery or a nickel-metal hydride secondary battery, and has a positive terminal and a negative terminal connected to positive power line 24p and negative power line 24n. Smoothing capacitors 26 are installed on positive power line 24p and negative power line 24n.

[0029] The power conversion device 30 includes a first inverter 32 , a second inverter 34 , and a connection switch 36 .

[0030] The first inverter 32 is connected to the positive-side power line 24p and the negative-side power line 24n connected to the battery 22. The first inverter 32 has six transistors T11 to T16 as switching elements and six diodes D11 to D16 connected in parallel to the six transistors T11 to T16, respectively. The transistors T11 to T16 are each composed of SiC-MOSFET (SiC-Metal Oxide Semiconductor Field Effect Transistor). Each pair of two transistors (transistor T11 and transistor T14, transistor T12 and transistor T15, transistor T13 and transistor T16) among the transistors T11 to T16 is configured so as to be located on the source side and the drain side relative to the positive-side power line 24p and the negative-side power line 24n. Furthermore, connection points of the two transistors forming a pair of transistors T11 to T16 are connected to one end side of the three-phase coils (u-phase, v-phase, and w-phase coils) of the open winding motor 40 .

[0031] The second inverter 34 is connected to the positive-side power line 24p and the negative-side power line 24n connected to the battery 22 in such a manner that the second inverter 34 and the battery 22 sandwich the first inverter 32. The second inverter 34 has six transistors T21 to T26 as switching elements and six diodes D21 to D26 connected in parallel to the six transistors T21 to T26, respectively. The transistors T21 to T23 constituting the upper arm of the second inverter 34 are constituted by SiC-MOSFETs in the same manner as the transistors T11 to T16 of the first inverter 32. The transistors T24 to T26 constituting the lower arm of the second inverter 34 are constituted by Si-IGBTs (Si-Insulated Gate Bipolar Transistors). Each pair of two transistors (transistors T21 and T24, transistors T22 and T25, transistors T23 and T26) of the transistors T21 to T26 is arranged so as to be located on the source side and the drain side with respect to the positive-side power line 24p and the negative-side power line 24n. In addition, each connection point of the connection points of the two transistors in the pair of transistors T21 to T26 is connected to the other end side of the three-phase coil (coil of u-phase, v-phase, and w-phase) of the open winding motor 40.

[0032] The connection switch 36 is installed between the first inverter 32 and the second inverter 34 on the positive side power line 24p. The connection switch 36 is formed of SiC-MOSFETs like the transistors T11 to T16 of the first inverter 32 and the transistors T21 to T23 forming the upper arm of the second inverter 34.

[0033] The open-circuit winding motor 40 is a generator motor in which both ends of each winding of the three phases u phase, v phase, and w phase are configured as connection terminals. Three connection points of two transistors in pairs of the first inverter 32 are connected to one end side of each winding of the three phases u phase, v phase, and w phase. Three connection points of two transistors in pairs of the second inverter 34 are connected to the other end side of each winding of the three phases u phase, v phase, and w phase.

[0034] In the power conversion device 30 of the embodiment, the transistors T11 to T16 of the first inverter 32 are switched under the condition that the connection switch 36 is turned off, the transistors T21 to T23 of the upper arm of the second inverter 34 are turned on, and the transistors T24 to T26 of the lower arm are turned off. As a result, the open winding motor 40 can be driven in star connection. That is, by turning off the connection switch 36 and turning on the transistors T21 to T23 of the upper arm of the second inverter 34, the u-phase, v-phase, and w-phase of the open winding motor 40 are set as the neutral point by the turned-on transistors T21 to T23, and the open winding motor 40 is driven as a star-connected motor by the first inverter 32. As an example of driving the open winding motor 40 as a star-connected motor by the first inverter 32, Figure 2 2 shows the current flowing through the driving device 20 when the transistors T11 and T16 are turned on and the transistors T12, T13, T14, and T15 are turned off. Figure 2 , the current flow is indicated by the thick solid arrow. The transistors T21 to T23 of the upper arm of the second inverter 34 are always in the on state during the star connection driving. However, since the transistors T21 to T23 are composed of SiC-MOSFETs having excellent conduction characteristics compared to Si-IGBTs, the power loss during the star connection driving can be suppressed compared to the case where the transistors T21 to T23 are composed of Si-IGBTs.

[0035] It should be noted that in the power conversion device 30 of the embodiment, the transistors T11 to T16 of the first inverter 32 are switched and controlled while the connection switch 36 is turned on, and the transistors T21 to T26 of the second inverter 34 are switched and controlled. Thus, the open winding motor 40 can be driven in a delta connection. At this time, the connection switch 36 is always in an on state, but since the connection switch 36 is composed of a SiC-MOSFET having excellent conduction characteristics, the power loss during the delta connection drive can be suppressed.

[0036] In the power conversion device 30 of the embodiment described above, the six transistors T11 to T16 of the first inverter 32, the connection switch 36, and the transistors T21 to T23 constituting the upper arm of the second inverter 34 are constituted by SiC-MOSFETs having excellent conduction characteristics. As a result, the power loss during star connection driving and the power loss during delta connection driving can be suppressed. In addition, in general, Si-IGBT is cheaper than SiC-MOSFET. Therefore, compared with the case where the transistors T24 to T26 constituting the lower arm of the second inverter 34 are constituted by SiC-MOSFETs, the power conversion device 30 can be made cheaper.

[0037] In the power conversion device 30 of the embodiment, the six transistors T11 to T16 of the first inverter 32, the connection switch 36 installed on the positive-side power line 24p, and the transistors T21 to T23 constituting the upper arm of the second inverter 34 are composed of SiC-MOSFETs with excellent conduction characteristics. The transistors T24 to T26 constituting the lower arm of the second inverter 34 are composed of Si-IGBTs with poorer conduction characteristics than SiC-MOSFETs. However, as Figure 3 As shown in the power conversion device 30B of the drive device 20B of the modified example, the six transistors T11 to T16 of the first inverter 32, the connection switch 36B installed on the negative side power line 24n, and the transistors T34 to T36 constituting the lower arm of the second inverter 34B can also be composed of SiC-MOSFETs with excellent conduction characteristics. The transistors T31 to T33 constituting the upper arm of the second inverter 34B can also be composed of Si-IGBTs with poor conduction characteristics compared with SiC-MOSFETs. In this case, the transistors T11 to T16 of the first inverter 32 are switched under the condition that the connection switch 36B is turned off, the transistors T34 to T36 of the lower arm of the second inverter 34 are turned on, and the transistors T31 to T33 of the upper arm are turned off. In this way, the open winding motor 40 can be driven in star connection. In addition, the transistors T11 to T16 of the first inverter 32 are switched and controlled while the connection switch 36 is turned on, and the transistors T31 to T36 of the second inverter 34B are switched and controlled. Thus, the open winding motor 40 can be driven in a delta connection. In the power conversion device 30 of this modified example, the power loss during star connection driving and the power loss during delta connection driving can also be suppressed.

[0038] In the power conversion device 30 of the embodiment, the six transistors T11 to T16 of the first inverter 32, the connection switch 36, and the transistors T21 to T23 constituting the upper arm of the second inverter 34 are constituted by SiC-MOSFETs having excellent conduction characteristics. However, any semiconductor element having excellent conduction characteristics may be used, so the six transistors T11 to T16 of the first inverter 32, the connection switch 36, and the transistors T21 to T23 constituting the upper arm of the second inverter 34 may be constituted by switching elements based on wide-bandgap semiconductors. The switching elements based on wide-bandgap semiconductors may be, for example, switching elements based on wide-bandgap semiconductors using gallium nitride (GaN).

[0039] The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of the specific embodiment is explained. In the embodiment, the battery 22 is equivalent to the "power storage device". The open winding motor 40 is equivalent to the "open winding motor". The first inverter 32 is equivalent to the "first inverter". The second inverter 34 is equivalent to the "second inverter". The connection switch 36 is equivalent to the "line connection switching element".

[0040] It should be noted that the correspondence between the main elements of the embodiment and the main elements of the invention recorded in the column of the specific embodiment is an example of a way to specifically explain the embodiment for implementing the invention recorded in the column of the specific embodiment. Therefore, the elements of the invention recorded in the column of the specific embodiment are not limited. That is, the interpretation of the invention recorded in the column of the specific embodiment should be based on the description in the column, and the embodiment is only a specific example of the invention recorded in the column of the specific embodiment.

[0041] As mentioned above, although this disclosure was demonstrated using embodiment, this disclosure is not limited to such embodiment at all, It is a matter of course that this disclosure can be implemented in various forms within the range which does not deviate from the summary of this disclosure.

[0042] The present disclosure can be utilized in the manufacturing industry of power conversion devices and the like.

Claims

1. A power conversion device connected to a power storage device and a three-phase open-winding motor, characterized in that: The power conversion device comprises: a first inverter connected to a power line connected to the power storage device and connected to each phase of the open winding motor; a second inverter connected to the power line and to each phase of the open winding motor; as well as a line connection switching element mounted on a positive-electrode line of the power line between the first inverter and the second inverter, The three switching elements of the upper arm and the three switching elements of the lower arm of the first inverter, the three switching elements of the upper arm of the second inverter, and the line connection switching element are constituted by the first semiconductor switching element. The three switching elements of the lower arm of the second inverter are constituted by a second semiconductor switching element different from the first semiconductor switching element, As the first semiconductor switch element, a semiconductor switch element having a better conduction characteristic than the second semiconductor switch element is used.

2. A power conversion device connected to a power storage device and a three-phase open-winding motor, characterized in that: The power conversion device comprises: a first inverter connected to a power line connected to the power storage device and connected to each phase of the open winding motor; a second inverter connected to the power line and to each phase of the open winding motor; as well as a line connection switching element installed on a negative-electrode line of the power line between the first inverter and the second inverter, The three switching elements of the upper arm and the three switching elements of the lower arm of the first inverter, the three switching elements of the lower arm of the second inverter, and the line connection switching element are constituted by the first semiconductor switching element. The three switching elements of the upper arm of the second inverter are constituted by a second semiconductor switching element different from the first semiconductor switching element, As the first semiconductor switch element, a semiconductor switch element having a better conduction characteristic than the second semiconductor switch element is used.

3. The power conversion device according to claim 1 or 2, wherein: The first semiconductor switch element is a switch element based on a wide bandgap semiconductor using gallium nitride GaN or silicon carbide SiC. The second semiconductor switching element is a switching element based on a semiconductor using silicon Si.

4. The power conversion device according to claim 3, wherein: The first semiconductor switch element is a SiC-MOSFET, The second semiconductor switch element is a Si-IGBT.

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