WO2024116410A1

WO2024116410A1 - Current detection device and power conversion device

Info

Publication number: WO2024116410A1
Application number: PCT/JP2022/044604
Authority: WO
Inventors: 剛加藤
Original assignee: 日立Astemo株式会社
Priority date: 2022-12-02
Filing date: 2022-12-02
Publication date: 2024-06-06

Abstract

Provided is a current detection device comprising: a plurality of conductors connected to a plurality of power conversion circuits; a plurality of detectors that detect currents flowing through the respective conductors on the basis of magnetic fluxes generated by the currents flowing through the respective conductors; a plurality of first shield members that surround at least a part of the detectors and conductors for magnetic shielding thereof; and a second shield member that is placed opposite to the plurality of first shield members and covers the entire region of projection of the plurality of first shield members in a direction orthogonal to the direction of arrangement of the plurality of first shield members.

Description

Current detection device and power conversion device

The present invention relates to a current detection device and a power conversion device.

A conductor is connected to a power conversion circuit that converts between direct current and alternating current, and a detector is provided that detects the current flowing through the conductor. The detector detects the current based on the magnetic flux generated by the current flowing through the conductor. In a configuration that includes multiple power conversion circuits, a current detection device is provided that includes a detector for each system corresponding to each power conversion circuit. For example, two power conversion circuits are provided to control two motors, and two detectors for each system are provided corresponding to the conductors connected to each power conversion circuit. In this case, it is necessary to ensure that the magnetic flux generated in the conductor due to the operation of one power conversion circuit does not affect the detector corresponding to the other power conversion circuit. In particular, in a power conversion device for a vehicle that requires high reliability, high detection accuracy is required for the current detection device.

Patent Document 1 discloses a sensor unit (current detection device) that has multiple bus bars (conductors) connected to multiple switch modules (power conversion circuits), a terminal block that integrally connects these, and multiple magnetoelectric conversion units (detectors) that detect the current flowing through the bus bars.

Japanese Patent Publication No. 2021-2903

In the device described in Patent Document 1, the magnetic flux generated in the conductor by the operation of one power conversion circuit affects the detector corresponding to the other power conversion circuit, reducing the detection accuracy of the current detection device.

A current detection device according to a first aspect of the present invention comprises a plurality of conductors connected to a plurality of power conversion circuits, a plurality of detectors that detect a current flowing in the conductors based on a magnetic flux generated by a current flowing in the conductors, a plurality of first shielding members that surround the detectors and at least a portion of the conductors and magnetically shield the detectors and the conductors, and a second shielding member that is arranged opposite the plurality of first shielding members and covers the entire area of the projection areas of the plurality of first shielding members in a direction perpendicular to the arrangement direction of the plurality of first shielding members.
A power conversion device according to a second aspect of the present invention includes a current detection device and a housing that houses the plurality of power conversion circuits, one surface of the housing forming the second shield member.

The present invention reduces the effect of magnetic flux generated in a conductor due to the operation of one power conversion circuit on a detector corresponding to the other power conversion circuit, improving the detection accuracy of the current detection device.

FIG. 1 is a circuit configuration diagram of a power conversion device according to an embodiment of the present invention. FIG. 2 is a perspective view showing the appearance of the current detection device according to the present embodiment. FIG. 3A is a cross-sectional view of the current detection device according to this embodiment, and FIG. 3B is a top view of the current detection device according to this embodiment. FIG. 4 is a diagram showing the flow of magnetic flux in the current detection device according to the present embodiment. FIG. 5 is a diagram showing the flow of magnetic flux in a current detection device in a comparative example. FIG. 6 is a cross-sectional view showing a first modified example of the current detection device according to the present embodiment. FIG. 7 is a cross-sectional view showing a second modified example of the current detection device according to the present embodiment. FIG. 8 is a diagram showing a third modified example of the current detection device according to the present embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some parts have been omitted or simplified as appropriate for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

FIG. 1 is a circuit configuration diagram of a power conversion device 1000 according to an embodiment of the present invention.
The power conversion device 1000 includes a power conversion circuit 100 and a current detection device 200. DC power is applied to the power conversion circuit 100 from a DC power source (not shown) to a positive terminal P-T and a negative terminal N-T. In this embodiment, the power conversion circuit 100 includes two power conversion circuits. Specifically, the power conversion circuit 100 includes a smoothing capacitor 103 connected between a positive line P from the positive terminal P-T and a negative line N from the negative terminal N-T, and a first power conversion circuit 101 and a second power conversion circuit 102 connected in parallel to the positive line P and the negative line N.

The first power conversion circuit 101 and the second power conversion circuit 102 are each composed of an inverter, and convert DC current into AC current and vice versa. Conductors 1BU, 1BV, and 1BW are connected to the output side of the first power conversion circuit 101. Conductors 2BU, 2BV, and 2BW are connected to the output side of the second power conversion circuit 102. The three-phase AC current converted by the first power conversion circuit 101 is output via conductors 1BU, 1BV, and 1BW to the windings of a three-phase first motor (not shown) connected to

terminals

1U, 1V, and 1W, driving the first motor. The three-phase AC current converted by the second power conversion circuit 102 is output via conductors 2BU, 2BV, and 2BW to the windings of a three-phase second motor (not shown) connected to

terminals

2U, 2V, and 2W, driving the second motor. The first motor and the second motor function as generators during regeneration, and the AC current generated during regeneration is converted to DC current by the first power conversion circuit 101 and the second power conversion circuit 102, which charges the DC power source consisting of a secondary battery.

The current detection device 200 includes a first current detection device 201 and a second current detection device 202 corresponding to two systems of power conversion circuits, that is, the first power conversion circuit 101 and the second power conversion circuit 102, respectively.
The first current detection device 201 includes detectors 1DU, 1DV, 1DW that detect the respective currents based on the magnetic flux generated by the currents flowing through the conductors 1BU, 1BV, 1BW, and outputs the detected currents 1IU, 1IV, 1IW to a control unit not shown.

The second current detection device 202 is equipped with detectors 2DU, 2DV, 2DW that detect each current based on the magnetic flux generated by the current flowing in each of the conductors 2BU, 2BV, 2BW, and outputs the detected currents 2IU, 2IV, 2IW to a control unit not shown.
The current detection device 200 is configured by incorporating detectors 1DU, 1DV, 1DW and detectors 2DU, 2DV, 2DW, the details of which will be described later.

The power conversion device 1000 includes a control unit (not shown) that controls the inverters of the first power conversion circuit 101 and the second power conversion circuit 102. This control unit refers to the currents 1IU, 1IV, 1IW, 2IU, 2IV, and 2IW detected by the first current detection device 201 and the second current detection device 202 and the rotational positions of the first and second motors to calculate a voltage command value according to a torque command from a higher-level control device (not shown). Then, the inverters of the first power conversion circuit 101 and the second power conversion circuit 102 are controlled by a gate signal generated from the voltage command value and a carrier wave. In this way, the control unit controls the inverters by referring to the currents flowing through the conductors 1BU, 1BV, and 1BW and the conductors 2BU, 2BV, and 2BW, respectively. Therefore, in order to perform this control accurately, the current detection device 200 is required to have high detection accuracy.

FIG. 2 is a perspective view showing the appearance of a current detection device 200 according to the present embodiment.
The current detection device 200 includes two systems: a first current detection device 201 corresponding to the first power conversion circuit 101 and a second current detection device 202 corresponding to the second power conversion circuit 102 .

Detectors 1DU, 1DV, 1DW and detectors 2DU, 2DV, 2DW are arranged on substrate 211 corresponding to conductors 1BU, 1BV, 1BW and conductors 2BU, 2BV, 2BW. Detectors 1DU, 1DV, 1DW and detectors 2DU, 2DV, 2DW are, for example, coreless current sensors. A coreless current sensor is a device without a magnetic core that uses a magnetic sensor to detect the current flowing through conductors 1BU, 1BV, 1BW and conductors 2BU, 2BV, 2BW and generates a signal proportional to the amount of current using the output of the magnetic sensor.

The substrate 211 has the detectors 1DU, 1DV, 1DW, and 2DU, 2DV, and 2DW, as well as the peripheral circuit components, and a wiring pattern that electrically connects these. It also fixes the detectors 1DU, 1DV, 1DW, and 2DU, 2DV, and 2DW, and the first shield member 210 in specified positions.

The first shield member 210 is a plate-shaped magnetic material formed in a U-shape surrounding each of the detectors 1DU, 1DV, 1DW, 2DU, 2DV, 2DW and the corresponding conductors 1BU, 1BV, 1BW, 2BU, 2BV, 2BW. For example, the first shield member 210 surrounding the detector 1DU and the conductor 1BU surrounds at least a portion of the detector 1DU and the conductor 1BU, and magnetically shields the detector 1DU and the conductor 1BU. The first shield member 210 surrounding other detectors and corresponding conductors has a similar configuration. The first shield member 210 confines the magnetic flux generated around the conductor due to the current flowing through the conductor in the portion surrounded by the first shield member 210 in the inner space of the first shield member 210. It also shields magnetic flux (magnetic field disturbance) from adjacent detectors and their corresponding conductors. The first shield member 210 is not limited to a U-shape, and may be configured to surround at least a portion of the detector and the corresponding conductor. Each first shield member 210 is arranged linearly in a direction perpendicular to the direction in which each conductor extends.

The second shielding members 220 are arranged opposite each of the first shielding members 210 and are plate-shaped magnetic bodies arranged along the arrangement direction of the first shielding members 210. The second shielding members 220 are arranged with a predetermined gap between them and the first shielding members 210, and magnetically shield magnetic flux leaking from the first shielding members 210. Details of the second shielding members 220 will be described later.

FIG. 3(A) is a cross-sectional view of the current detection device 200 in this embodiment, and FIG. 3(B) is a top view of the current detection device 200 in this embodiment. The cross-sectional view shown in FIG. 3(A) is a cross-section taken along line X-X in FIG. 2. The top view shown in FIG. 3(B) shows the top surface of the second shield member 220, with conductors 1BU, 1BV, 1BW, 2BU, 2BV, and 2BW omitted.

As shown in FIG. 3A, the second shielding member 220 is formed with a protrusion 220X that protrudes by a length L from the first shielding members 210 located at both ends of the arrangement direction of the multiple first shielding members 210.

As shown in FIG. 3B, the width of the second shielding member 220 is greater at both ends by the length N than the width of the first shielding member in a direction perpendicular to the arrangement direction of the multiple first shielding members 210.

3(A) and 3(B) show an example in which the second shield member 220 is longer and wider than the entire area 210Z including the projection area of each of the first shield members 210 in a direction perpendicular to the arrangement direction of the first shield members 210. However, either the length or the width may be larger, or may be the same as the entire area 210Z including the projection area of each of the first shield members 210. In other words, the second shield member 220 may be arranged opposite the first shield members 210 and may be large enough to cover the entire area 210Z of the projection area of the first shield members 210 in a direction perpendicular to the arrangement direction of the first shield members 210. The current detection device 200 is not limited to cases in which it corresponds to two power conversion circuits 100, but is also similar when the current detection device 200 corresponds to three or more power conversion circuits 100. This can reduce the influence of the magnetic flux generated in the conductor due to the operation of one power conversion circuit on the detector corresponding to the other power conversion circuit, as described later.

4 is a diagram showing the flow of magnetic flux in the current detection device 200 according to this embodiment, in which a magnetic flux flow M is additionally shown in a cross-sectional view similar to that of FIG.
As an example, the following describes the effect that the magnetic flux has on detectors 1DU, 1DV, and 1DW when the second power conversion circuit 102 is operating and a large current flows through the conductors 2BU, 2BV, and 2BW.

The magnetic flux caused by the current flowing through the conductors 2BU, 2BV, and 2BW is detected by the detectors 2DU, 2DV, and 2DW, respectively. The magnetic flux M that passes through the first shield member 210 is collected in the second shield member 220, which has a low magnetic resistance, as shown by the black arrow in FIG. 4. Then, it passes through the protrusions 220X at both ends of the length of the second shield member 220 and is released into the air from the ends. If the protrusions 220X are provided on the second shield member 220, the effect of the magnetic flux M on the detectors 1DU, 1DV, and 1DW can be further reduced, but even if the protrusions 220X are not provided, the effect can be reduced by releasing the magnetic flux M into the air from the ends of the second shield member 220. The same applies to the width direction of the second shield member 220. That is, since the second shield member 220 is large enough to cover the entire area 210Z of the projection area of the multiple first shield members 210, the effect of the magnetic flux M that passes through the first shield member 210 due to the current flowing through the conductors 2BU, 2BV, and 2BW on the detectors 1DU, 1DV, and 1DW can be reduced.

According to this embodiment, the current detection accuracy can be improved even when using a coreless current sensor that does not require a core as a detector and can be made smaller. This improvement makes it possible to control the inverter more accurately, and when the inverter and motor are used to drive a vehicle, it is expected that the vehicle's driving range will be improved and energy savings will be achieved.

FIG. 5 is a diagram showing the flow of magnetic flux in a current detection device 200' in a comparative example. This comparative example is an example to which this embodiment is not applied, and is intended to deepen understanding of this embodiment by comparing it with this embodiment.

In this comparative example, the second shielding member 220 shown in FIG. 4 is divided into two, a third shielding member 223 and a fourth shielding member 224. The third shielding member 223 corresponds to the detectors 1DU, 1DV, 1DW and the conductors 1BU, 1BV, 1BW, and the fourth shielding member 224 corresponds to the detectors 2DU, 2DV, 2DW and the conductors 2BU, 2BV, 2BW.

As an example, the second power conversion circuit 102 is operating, a large current flows through the conductors 2BU, 2BV, and 2BW, and the effect of this magnetic flux on the detectors 1DU, 1DV, and 1DW is described below.

The magnetic flux due to the current flowing through the conductors 2BU, 2BV, and 2BW is detected by the detectors 2DU, 2DV, and 2DW, respectively. The magnetic flux M that passes through the first shield member 210 is collected in the fourth shield member 224, which has a small magnetic resistance, as shown by the black arrow in FIG. 5. Then, it is released into the air from both ends of the fourth shield member 224 in the length direction. The magnetic flux M released into the air from the end of the fourth shield member 224 located between the third shield member 223 reaches the detector 1DW, partly through the third shield member 223 and partly through the first shield member 210. Therefore, the detector 1DW cannot accurately detect the current flowing through the conductor 1BW because the magnetic flux M released into the air from the end of the fourth shield member 224 is added to the magnetic flux due to the current flowing through the conductor 1BW. In this comparative example, an example in which the second shield member 220 shown in FIG. 4 is divided into two is shown. Not limited to this comparative example, if the second shield member 220 shown in FIG. 4 is not large enough to cover the entire area 210Z of the projection area of the multiple first shield members 210, the magnetic flux M emitted from its end into the air will affect the detector.

FIG. 6 is a cross-sectional view showing modified example 1 of the current detection device 200 in this embodiment. This cross-sectional view corresponds to the cross-section of line X-X in FIG. 2. The same reference numerals are used to designate the same parts as in the cross-sectional view shown in FIG. 3(A) and their explanation will be simplified.

As shown in FIG. 6, the second shielding member 220 is formed to protrude longer than the first shielding members 210 located at both ends of the arrangement direction of the multiple first shielding members 210. The second shielding member 220 protrudes in the direction Y away from the first shielding member 210 located at the end of the arrangement direction. The magnetic flux emitted into the air from the end of the second shielding member 220 is directed away from the first shielding member 210, so its influence can be further reduced.

FIG. 7 is a cross-sectional view showing modified example 2 of the current detection device 200 in this embodiment. This cross-sectional view corresponds to the cross-section of line X-X in FIG. 2. The same reference numerals are used to designate the same parts as in the cross-sectional view shown in FIG. 3(A) and their explanation will be simplified.

As shown in FIG. 7, the second shield member 220 is formed by connecting two

separate members

225 and 226. The two

members

225 and 226 are connected by gluing, screws, or the like, as long as the magnetic resistance is low so that magnetic flux can flow between the

connected members

225 and 226. When the second shield member 220 is formed by connecting two or more members, each member is small, so the mold can also be made smaller, reducing costs.

FIG. 8 is a diagram showing a third modified example of the current detection device 200 in this embodiment. In FIG. 8, the power conversion device 1000 is also shown as a cross-sectional view. This cross-sectional view corresponds to the cross-section of line X-X in FIG. 2. The same reference numerals are used to designate the same parts as in the cross-sectional view shown in FIG. 3(A), and their explanation will be simplified.

The power conversion device 1000 houses the current detection device 200 and the power conversion circuit 100 in its housing 1100. The power conversion circuit 100 includes a first power conversion circuit 101 and a second power conversion circuit 102 (see FIG. 1), each of which is composed of an inverter (not shown), and is housed in a housing 110.

One surface of the housing 110 housing the first power conversion circuit 101 and the second power conversion circuit 102, i.e., the surface facing the current detection device 200, is formed of a plate-shaped magnetic material and constitutes the second shielding member 220. As already mentioned, in this case, the second shielding member 220 is large enough to cover the entire area 210Z (see FIG. 3(B)) of the projection area of the multiple first shielding members 210 in a direction perpendicular to the arrangement direction of the multiple first shielding members 210. By using the second shielding member 220 as one surface of the housing 110, the power conversion device 1000 can be made smaller and costs can be reduced.

According to the embodiment described above, the following advantageous effects can be obtained.
(1) The current detection device 200 includes a plurality of conductors 1BU-1BW, 2BU-2BW connected to a plurality of power conversion circuits 100, a plurality of detectors 1DU-1DW, 2DU-2DW that detect a current flowing in the conductors 1BU-1BW, 2BU-2BW based on a magnetic flux generated by a current flowing in the conductors 1BU-1BW, 2BU-2BW, a plurality of first shield members 210 that surround at least a portion of the detectors 1DU-1DW, 2DU-2DW and the conductors 1BU-1BW, 2BU-2BW and magnetically shield the detectors 1DU-1DW, 2DU-2DW and the conductors 1BU-1BW, 2BU-2BW, and a second shield member 220 that is arranged opposite the plurality of first shield members 210 and covers an entire area 210Z of a projection area of the plurality of first shield members 210 in a direction perpendicular to the arrangement direction of the plurality of first shield members 210. This reduces the influence of magnetic flux generated in a conductor due to the operation of one power conversion circuit on the detector corresponding to the other power conversion circuit, improving the detection accuracy of the current detection device.

The present invention is not limited to the above-described embodiment, and other forms that are conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention, so long as they do not impair the characteristics of the present invention. In addition, a configuration that combines the above-described embodiment with multiple modified examples may also be used.

100: power conversion circuit, 101: first power conversion circuit, 102: second power conversion circuit, 103: smoothing capacitor, 110: housing of power conversion circuit, 200: current detection device, 201: first current detection device, 202: second current detection device, 210: first shielding member, 210Z: entire area of the projection area of the first shielding members, 211: substrate, 220: second shielding member, 220X: protrusion, 223: third shielding member, 224: fourth shielding member, 1000: power conversion device, 1100: housing of power conversion device, 1BU, 1BV, 1BW, 2BU, 2BV, 2BW: conductor, 1DU, 1DV, 1DW, 2DU, 2DV, 2DW: detector, Y: separation direction, M: magnetic flux.

Claims

A plurality of conductors connected to a plurality of power conversion circuits;
a plurality of detectors for detecting a current flowing through the conductor based on a magnetic flux generated by the current flowing through the conductor;
a plurality of first shield members surrounding at least a portion of the detector and the conductor and magnetically shielding the detector and the conductor;
A current detection device comprising a second shielding member arranged opposite the multiple first shielding members and covering the entire area of the projection areas of the multiple first shielding members in a direction perpendicular to the arrangement direction of the multiple first shielding members.
2. The current detection device according to claim 1,
The second shield member is formed with a protrusion that protrudes from a first shield member that is located at an end of the plurality of first shield members in the arrangement direction.
2. The current detection device according to claim 1,
The second shield member protrudes away from the first shield member located at the end of the arrangement direction.
2. The current detection device according to claim 1,
The second shield member is a current detection device formed by connecting a plurality of divided members.
The current detection device according to any one of claims 1 to 4,
The detector is a coreless current sensor.
The current detection device according to any one of claims 1 to 4,
A current detection device in which the second shield member has a width greater than a width of the first shield member in a direction perpendicular to the arrangement direction of the plurality of first shield members.
The current detection device according to any one of claims 1 to 4,
The second shield member of the current detection device is formed of a plate-shaped magnetic material.
A current detection device according to any one of claims 1 to 4,
a housing that houses the plurality of power conversion circuits,
One surface of the housing is a power conversion device that constitutes the second shield member.