JP7703993B2 - Short circuit protection device for power conversion equipment - Google Patents

Description

The present invention relates to a short-circuit protection device for a power conversion device.

In a power conversion device that drives a load such as a motor, an excessive current may flow through the semiconductor switching elements that make up the power conversion device. If such an excessive current flows for a long period of time, there is a risk that the semiconductor switching elements will be destroyed. Therefore, a short-circuit protection device is provided in the power conversion device to detect excessive current flowing through the semiconductor switching elements and stop the power conversion device.

In the technology disclosed in Patent Document 1, a current detector is provided for each of a number of arms, each of which includes a voltage-driven semiconductor element, to detect the current flowing through each arm. When the arm current of the voltage-driven semiconductor element driven by each of the current detectors exceeds a predetermined value, short-circuit protection is performed by turning off the gate pulse output by the gate drive means.

JP 2008-236907 A

However, in order to increase capacity in power conversion devices, multiple switching elements may be connected in parallel to form individual arms. In this case, a current detector is required for each switching element, which raises concerns about increased costs and larger equipment.

This invention was made in consideration of the problems described above, and aims to reduce the increase in cost and size of a power conversion device that occurs for short circuit protection when multiple switching elements are connected in parallel.

The short-circuit protection device for a power conversion device according to the present invention is a short-circuit protection device for a power conversion device that supplies power to a load via a plurality of switching element units connected in parallel, and includes Ma=M-1 current detectors, one less than the number M of the plurality of switching element units, each including Ma Rogowski coils that surround the current paths of two or more switching element units in the plurality of switching element units, and a short-circuit determination unit that determines that a short-circuit fault has occurred in the plurality of switching element units based on detection signals obtained from the Ma current detectors and outputs a cut-off instruction signal to stop the on-off drive of the plurality of switching element units, and the Nth (N is an integer from 1 to Ma) current detector in the Ma current detectors detects the sum of currents flowing in all switching element units other than the Nth switching element unit among the 1st to Mth switching element units, and the short-circuit determination unit detects the sum of currents flowing in the Mth switching element unit when all of the current detection values by the Ma current detectors exceed a threshold value. It is determined that a short circuit has occurred in the switching element part that is not the target of current detection in the one current detector when the current detection value of one of the Ma current detectors does not exceed the threshold value and the current detection value of the other Ma-1 current detectors exceeds the threshold value, and it is determined that a short circuit has occurred in the switching element part that is not the target of current detection in that one current detector, and the Ma is 3 or more, the Ma Rogowski coils are mounted on a multilayer printed circuit board, and the multilayer printed circuit board has an overlapping portion in which the Ma Rogowski coils are lined up in the depth direction, and the return wire of the Rogowski coil on the top layer side of the multilayer printed circuit board is positioned on the top layer side of the central axis of the Rogowski coil, and the return wire of the Rogowski coil on the bottom layer side of the multilayer printed circuit board is positioned on the bottom layer side of the central axis of the Rogowski coil, thereby forming an area in the overlapping portion where the distance between the return wires of adjacent Rogowski coils in the depth direction is longer than the distance between the central axes of the adjacent Rogowski coils.

According to this invention, it is possible to detect short-circuit failures of current detectors using a number of current detectors that is less than the number of switching element units, and to identify the switching element unit in which a short-circuit failure has occurred, thereby reducing the increase in cost and size of the power conversion device that occurs for short-circuit protection when multiple switching element units are connected in parallel. Also, in the overlapping portion where Ma Rogowski coils are lined up in the depth direction, a region is formed in the overlapping portion where the distance between the return wires of adjacent Rogowski coils in the depth direction is longer than the distance between the central axes of the adjacent Rogowski coils, so that when a current flows through one return wire, the effect of that current on other return wires adjacent to that return wire can be reduced, and the accuracy of current measurement can be improved.

1 is a circuit diagram showing a configuration of a power conversion device including a short-circuit protection device according to an embodiment of the present invention. 2 is a block diagram showing an example of the configuration of a short-circuit determination unit of the short-circuit protection device; FIG. FIG. 4 is a waveform diagram showing an operation example of the embodiment. FIG. 4 is a waveform diagram showing an operation example of the embodiment. FIG. 4 is a waveform diagram showing an operation example of the embodiment. FIG. 4 is a waveform diagram showing an operation example of the embodiment. 2 is a perspective view showing an example of mounting three Rogowski coils in the short circuit protection device. FIG. FIG. 2 is a plan view showing an example of the configuration of the Rogowski coil. FIG. 13 is a perspective view showing an example of mounting the overlapping portions of the three Rogowski coils. FIG. 13 is an abstract diagram of the implementation example. 2 is a plan view showing an example of mounting four Rogowski coils in the short circuit protection device. FIG. FIG. 2 is an abstract view of a first embodiment of the four Royski coils. FIG. 13 is an abstract view of a second embodiment of the four Royski coils.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 is a circuit diagram showing the configuration of a power conversion device 100 including a short-circuit protection device 50 according to an embodiment of the present invention. The power conversion device 100 includes a control unit 1 that controls each part of the power conversion device 100 in accordance with commands from a higher-level device 200, and drive units 2a and 2b that convert power.

In this embodiment, the power conversion device 100 is a device equivalent to one phase of an inverter. FIG. 1 shows the driving units 2a and 2b for one phase of this inverter. The driving unit 2a is connected between a high-potential power line 101 connected to the positive pole of a DC power source (not shown) and an output terminal 103 connected to a load (not shown). The driving unit 2b is connected between a low-potential power line 102 connected to the negative pole of the DC power source and the output terminal 103. The power conversion device 100 configures an inverter by connecting the driving units 2a and 2b for multiple phases in parallel between the high-potential power line 101 and the low-potential power line 102.

The internal structure of drive unit 2a will be described below. The internal structure of drive unit 2b is basically the same as drive unit 2a, so a description of it will be omitted.

The drive unit 2a includes a plurality of switching element units 20_1, 20_2, 20_3, and 20_4 connected in parallel, a drive control unit 24, and a short-circuit protection device 50.

Each of the switching element units 20_1, 20_2, 20_3, and 20_4 includes a power switching element 27. This power switching element 27 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and is composed of a wide-gap semiconductor element such as SiC or GaN. A diode 28 is connected in inverse parallel to the power switching element 27. Like the driving unit 2a, the driving unit 2b also includes multiple switching element units connected in parallel. The power conversion device 100 supplies power to a load connected to the output terminal 103 via multiple switching element units connected in parallel in each of the driving units 2a and 2b.

The drive control unit 24 outputs a drive signal Son/off that switches the power switching elements 27 of the switching element units 20_1, 20_2, 20_3, and 20_4 from off to on or from on to off based on the control signal Sm1 supplied from the control unit 1. In addition, when a cut-off instruction signal Fx is output from the short-circuit protection device 50, the drive control unit 24 outputs a drive signal Son/off that turns off the power switching elements 27 of the switching element units 20_1, 20_2, 20_3, and 20_4.

The short-circuit protection device 50 detects the occurrence of a short-circuit failure in the parallel-connected switching element units 20_1, 20_2, 20_3, and 20_4, and protects the switching element units 20_1, 20_2, 20_3, and 20_4 from the short-circuit failure. As shown in FIG. 1, the short-circuit protection device 50 includes Rogowski coils 21_1, 21_2, and 21_3, integrators 22_1, 22_2, and 22_3, and a short-circuit determination unit 23. Possible short-circuit failures in the switching element units 20_1 and the like include false on or short-circuit failure of the power switching element 27, and short-circuit failure of the diode 28.

The Rogowski coils 21_1, 21_2, and 21_3 are Ma current detectors, which is one less than the number M (M=4 in this example) of the multiple switching element units connected in parallel, specifically Ma=M-1=3, and are Ma current detectors that detect the sum of currents flowing through two or more switching element units in the multiple switching element units and output a detection signal indicating the detection result. The Ma Rogowski coils of the Ma current detectors each surround the current paths of two or more switching element units in the M switching element units. In this embodiment, the Rogowski coils 21_1, 21_2, and 21_3 are provided in the current paths on the source side of the power switching elements 27 of the switching element units 20_1, 20_2, 20_3, and 20_4.

In this embodiment, the Nth current detector (N is an integer from 1 to Ma) among the Ma current detectors detects the sum of the currents flowing through all switching element units other than the Nth switching element unit among the 1st to Mth switching element units.

Specifically, in this embodiment, the first switching element unit is switching element unit 20_1, the second switching element unit is switching element unit 20_2, the third switching element unit is switching element unit 20_3, and the fourth switching element unit is switching element unit 20_4. The first current detector is Rogowski coil 21_1, the second current detector is Rogowski coil 21_2, and the third current detector is Rogowski coil 21_3.

The Rogowski coil 21_1, which is the first current detector, surrounds the current paths 20_2a, 20_3a, and 20_4a of the switching element units 20_2, 20_3, and 20_4 other than the first switching element unit 10_1, detects the sum of the currents flowing through these current paths, and outputs a detection signal Vi1 indicating the detection result to the integrator 22_1. This detection signal Vi1 indicates the time derivative of the sum of the currents flowing through the switching element units 20_2, 20_3, and 20_4. The integrator 22_1 integrates the detection signal Vi1 to generate a current detection value Si1 indicating the sum of the currents flowing through the switching element units 20_2, 20_3, and 20_4, and outputs it to the short circuit determination unit 23.

The Rogowski coil 21_2, which is the second current detector, surrounds the current paths 20_1a, 20_3a, and 20_4a of the other switching element units 20_1, 20_3, and 20_4 except for the second switching element unit 20_2, detects the sum of the currents flowing through these current paths, and outputs a detection signal Vi2 indicating the detection result to the integrator 22_2. This detection signal Vi2 indicates the time derivative of the sum of the currents flowing through the switching element units 20_1, 20_3, and 20_4. The integrator 22_2 integrates the detection signal Vi2 to generate a current detection value Si2 indicating the sum of the currents flowing through the switching element units 20_1, 20_3, and 20_4, and outputs it to the short circuit determination unit 23.

The Rogowski coil 21_3, which is the third current detector, surrounds the current paths 20_1a, 20_2a, and 20_4a of the other switching element units 20_1, 20_2, and 20_4 except for the third switching element unit 20_3, detects the sum of the currents flowing through these current paths, and outputs a detection signal Vi3 indicating the detection result to the integrator 22_3. This detection signal Vi3 indicates the time derivative of the sum of the currents flowing through the switching element units 20_1, 20_2, and 20_4. The integrator 22_3 integrates the detection signal Vi3 to generate a current detection value Si3 indicating the sum of the currents flowing through the switching element units 20_1, 20_2, and 20_4, and outputs it to the short circuit determination unit 23.

The short circuit determination unit 23 performs a determination regarding the short circuit failure of the switching element units 20_1, 20_2, 20_3, and 20_4 based on the current detection values Si1, Si2, and Si3. The short circuit determination unit 23 outputs a short circuit failure signal F1 when it determines that a short circuit failure has occurred in the switching element unit 20_1, a short circuit failure signal F2 when it determines that a short circuit failure has occurred in the switching element unit 20_2, a short circuit failure signal F3 when it determines that a short circuit failure has occurred in the switching element unit 20_3, and a short circuit failure signal F4 when it determines that a short circuit failure has occurred in the switching element unit 20_4 to the control unit 1. The control unit 1 transmits the short circuit failure signal F1, F2, F3, or F4 to the upper device 200. As a result, the upper device 200 performs a process such as displaying information identifying the switching element unit 20_1, 20_2, 20_3, or 20_4 in which the short circuit failure has occurred on a display unit, for example. In addition, when the short circuit determination unit 23 determines that a short circuit has occurred in any of the switching element units 20_1, 20_2, 20_3, or 20_4, it outputs a cutoff instruction signal Fx to the drive control unit 24. This causes the drive control unit 24 to stop turning on and off the power switching elements 27 of the switching element units 20_1, 20_2, 20_3, and 20_4.

Figure 2 is a block diagram showing an example of the configuration of the short circuit determination unit 23. As shown in Figure 2, the short circuit determination unit 23 has comparators 301, 302, and 303, NOT operators 311, 312, and 313, AND operators 321, 322, 323, and 324, on-delay operators 331, 332, 333, and 334, and OR operator 340. The on-delay operators 331, 332, 333, and 334 are operators that delay the change of the input signal from an inactive level to an active level to each of them for a predetermined time and output the signal, and play a role in stabilizing the operation of the short circuit determination unit 23.

The comparator 301 sets the output signal to an inactive level when the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4 does not exceed the short-circuit current judgment threshold th, and sets the output signal to an active level when it does exceed the short-circuit current judgment threshold th. The comparator 302 sets the output signal to an inactive level when the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4 does not exceed the short-circuit current judgment threshold th, and sets the output signal to an active level when it does exceed the short-circuit current judgment threshold th. The comparator 303 sets the output signal to an inactive level when the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 does not exceed the short-circuit current judgment threshold th, and sets the output signal to an active level when it does exceed the short-circuit current judgment threshold th. In this case, the short-circuit current judgment threshold th may be, for example, 300% of the rated power switching element current.

The NOT operator 311 inverts the level of the output signal of the comparator 301 and outputs the inverted signal. The NOT operator 312 inverts the level of the output signal of the comparator 302 and outputs the inverted signal. The NOT operator 313 inverts the level of the output signal of the comparator 303 and outputs the inverted signal.

When at least one of the output signals of the comparators 301, 302, and 303 is at an active level, that is, when at least one of the sum of the currents of the switching element units 20_2, 20_3, and 20_4, the sum of the currents of the switching element units 20_1, 20_3, and 20_4, and the sum of the currents of the switching element units 20_1, 20_2, and 20_4 exceeds the short-circuit current determination threshold th, the OR operator 340 determines that a short-circuit fault has occurred in any of the switching element units 20_1, 20_2, 20_3, or 20_4, and outputs a cut-off instruction signal Fx to the drive control unit 24.

When the output signal of the NOT operator 311 is at an active level and the output signals of the comparators 302 and 303 are at an active level, i.e., when the sum of the currents of the switching element units 20_2, 20_3 and 20_4 does not exceed the short-circuit current judgment threshold th and both the sum of the currents of the switching element units 20_1, 20_3 and 20_4 and the sum of the currents of the switching element units 20_1, 20_2 and 20_4 exceed the short-circuit current judgment threshold th, the AND operator 321 determines that a short-circuit fault has occurred in the switching element unit 20_1 and outputs a short-circuit fault signal F1 to the control unit 1 via the on-delay operator 331. In this way, if the current detection value of one of the Ma current detectors (in this example, the current detection value Si1 obtained by the Rogowski coil 21_1) does not exceed the threshold value, and the current detection values of the other Ma-1 current detectors (in this example, the current detection values Si2 and Si3 obtained by the Rogowski coils 21_2 and 21_3) exceed the threshold value, the AND operator 321 determines that a short circuit has occurred in the switching element unit (in this example, the switching element unit 20_1) that is not the target of current detection in that one current detector.

When the output signal of the NOT operator 312 is at an active level and the output signals of the comparators 301 and 303 are at an active level, i.e., when the sum of the currents of the switching element units 20_1, 20_3 and 20_4 does not exceed the short-circuit current judgment threshold th and both the sum of the currents of the switching element units 20_2, 20_3 and 20_4 and the sum of the currents of the switching element units 20_1, 20_2 and 20_4 exceed the short-circuit current judgment threshold th, the AND operator 322 determines that a short-circuit fault has occurred in the switching element unit 20_2 and outputs a short-circuit fault signal F2 to the control unit 1 via the on-delay operator 332. In this way, if the current detection value of one of the Ma current detectors (in this example, the current detection value Si2 obtained by the Rogowski coil 21_2) does not exceed the threshold value, and the current detection values of the other Ma-1 current detectors (in this example, the current detection values Si1 and Si3 obtained by the Rogowski coils 21_1 and 21_3) exceed the threshold value, the AND operator 322 determines that a short circuit has occurred in the switching element unit (in this example, the switching element unit 20_2) that is not the target of current detection in that one current detector.

When the output signal of the NOT operator 313 is at an active level and the output signals of the comparators 301 and 302 are at an active level, i.e., when the sum of the currents of the switching element units 20_1, 20_2 and 20_4 does not exceed the short-circuit current judgment threshold th and both the sum of the currents of the switching element units 20_2, 20_3 and 20_4 and the sum of the currents of the switching element units 20_1, 20_3 and 20_4 exceed the short-circuit current judgment threshold th, the AND operator 323 determines that a short-circuit fault has occurred in the switching element unit 20_3 and outputs a short-circuit fault signal F3 to the control unit 1 via the on-delay operator 333. In this way, if the current detection value of one of the Ma current detectors (in this example, the current detection value Si3 obtained by the Rogowski coil 21_3) does not exceed the threshold value, and the current detection values of the other Ma-1 current detectors (in this example, the current detection values Si1 and Si2 obtained by the Rogowski coils 21_1 and 21_2) exceed the threshold value, the AND operator 323 determines that a short circuit has occurred in the switching element unit (in this example, the switching element unit 20_3) that is not the target of current detection in that one current detector.

When all the output signals of the comparators 301, 302, and 303 are at the active level, that is, when the sum of the currents of the switching element units 20_2, 20_3, and 20_4, the sum of the currents of the switching element units 20_1, 20_3, and 20_4, and the sum of the currents of the switching element units 20_1, 20_2, and 20_4 all exceed the short-circuit current determination threshold th, the AND operator 324 determines that a short-circuit fault has occurred in the switching element unit 20_4, and outputs a short-circuit fault signal F4 to the control unit 1 via the on-delay operator 334. In this way, when all the current detection values by the Ma current detectors (current detection values Si1, Si2, and Si3 obtained by the Rogowski coils 21_1, 20_2, and 21_3 in this example) exceed the threshold th, the AND operator 324 determines that a short-circuit fault has occurred in the Mth switching element unit (switching element unit 20_4 in this example).

Figures 3 to 6 are waveform diagrams showing examples of operation when a short circuit fault is detected in this embodiment. Below, the operation of this embodiment will be explained with reference to these figures.

In the operation example shown in FIG. 3, a short circuit fault occurs in switching element unit 20_1. During normal operation before the short circuit fault occurs, current detection value Si1 indicating the sum of the currents of switching element units 20_2, 20_3, and 20_4 is lower than short circuit current determination threshold th. Current detection value Si2 indicating the sum of the currents of switching element units 20_1, 20_3, and 20_4 is also lower than short circuit current determination threshold th. Current detection value Si3 indicating the sum of the currents of switching element units 20_1, 20_2, and 20_4 is also lower than short circuit current determination threshold th.

When a short circuit fault occurs in the switching element unit 20_1, the current flowing through the switching element unit 20_1 becomes larger than normal. In this case, the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4 and the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 exceed the short circuit current determination threshold th, while the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4 does not exceed the short circuit current determination threshold th. Therefore, the cutoff instruction signal Fx and the short circuit fault signal F1 identifying the switching element unit 20_1 as the short circuit fault location become active levels.

In the operation example shown in FIG. 4, a short circuit fault occurs in the switching element unit 20_2. The normal operation before the short circuit fault occurs is the same as the operation example in FIG. 3.

When a short circuit fault occurs in the switching element unit 20_2, the current flowing through the switching element unit 20_2 becomes larger than normal. In this case, the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4 and the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 exceed the short circuit current determination threshold th, while the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4 does not exceed the short circuit current determination threshold th. Therefore, the cutoff instruction signal Fx and the short circuit fault signal F2 identifying the switching element unit 20_2 as the short circuit fault location become active levels.

In the operation example shown in FIG. 5, a short circuit fault occurs in the switching element unit 20_3. The normal operation before the short circuit fault occurs is the same as the operation example in FIG. 3.

When a short circuit fault occurs in the switching element unit 20_3, the current flowing through the switching element unit 20_3 becomes larger than normal. In this case, the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4 and the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4 exceed the short circuit current determination threshold th, while the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 does not exceed the short circuit current determination threshold th. Therefore, the cutoff instruction signal Fx and the short circuit fault signal F3 identifying the switching element unit 20_3 as the short circuit fault location become active levels.

In the operation example shown in FIG. 6, a short circuit fault occurs in the switching element unit 20_4. The normal operation before the short circuit fault occurs is the same as the operation example in FIG. 3.

When a short circuit fault occurs in the switching element unit 20_4, the current flowing through the switching element unit 20_4 becomes larger than normal. In this case, the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4, the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4, and the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 all exceed the short circuit current determination threshold th. As a result, the cutoff instruction signal Fx and the short circuit fault signal F4 identifying the switching element unit 20_4 as the short circuit fault location become active levels.

As described above, according to this embodiment, the three Rogowski coils 21_1, 21_2, and 21_3, which is one less than the number of parallel switching element units 20_1, 20_2, 20_3, and 20_4 (four), can detect short-circuit failures in each switching element unit, stop driving the switching element units 20_1, 20_2, 20_3, and 20_4, and identify the switching element unit that is the short-circuit failure location. Therefore, it is possible to reduce the increase in cost and size of the power conversion device 100 that occurs for short-circuit protection when multiple switching element units are connected in parallel. In addition, in this embodiment, the three Rogowski coils 21_1, 21_2, and 21_3 all detect the sum of the currents of the three switching element units. Therefore, the current detection accuracy of each Rogowski coil can be made the same, and the short-circuit failure of each switching element unit can be accurately determined.

Next, an example of a Rogowski coil suitable for this embodiment will be described. FIG. 7 is a perspective view illustrating Rogowski coils 21_1, 21_2, and 21_3 mounted on a substrate 400. In this example, Rogowski coils 21_1, 21_2, and 21_3 are mounted on the substrate 400 in an overlapping state at the overlapping portion OV.

In this substrate 400, the current path 20_1a of the switching element unit 20_1 is inserted into the region surrounded by the Rogowski coils 21_2 and 20_3, but not surrounded by the Rogowski coil 21_1. In addition, in the substrate 400, the current path 20_2a of the switching element unit 20_2 is inserted into the region surrounded by the Rogowski coils 21_1 and 21_3, but not surrounded by the Rogowski coil 21_2. In addition, in the substrate 400, the current path 20_3a of the switching element unit 20_3 is inserted into the region surrounded by the Rogowski coils 21_1 and 21_2, but not surrounded by the Rogowski coil 21_3. In addition, in the substrate 400, the current path 20_4a of the switching element unit 20_4 is inserted into the region surrounded by all of the Rogowski coils 21_1, 21_2, and 21_3. In this case, the overlapping portions OV where the three Rogowski coils 21_1, 21_2, and 21_3 overlap in the depth direction of the substrate 400 are generated below the current paths 20_2a, 20_3a, and 20_4a, to the right of the current path 20_4a, and above the current path 20_4a in FIG. 7.

The Rogowski coil 21_1 surrounds the current paths 20_2a, 20_3a, and 20_4a, and detects the sum of the currents of the switching element units 20_2, 20_3, and 20_4 that flow through these current paths. The Rogowski coil 21_2 surrounds the current paths 20_1a, 20_3a, and 20_4a, and detects the sum of the currents of the switching element units 20_1, 20_3, and 20_4 that flow through these current paths. The Rogowski coil 21_3 surrounds the current paths 20_1a, 20_2a, and 20_4a, and detects the sum of the currents of the switching element units 20_1, 20_2, and 20_4 that flow through these current paths.

Figure 8 is a plan view illustrating Rogowski coil 21_1. As shown in Figure 8, Rogowski coil 21_1 has coil 21_1_C extending in a spiral shape and return line 21_1_R that runs through coil 21_1_C from the end point of coil 21_1_C back to the start point. Although not shown in the figure, Rogowski coils 21_2 and 21_3 have the same configuration as Rogowski coil 21_1.

Figure 9 is a perspective view showing an example of mounting Rogowski coils 21_1, 21_2, and 21_3 in the overlapping portion OV of Figure 7. In Figure 9, Rogowski coils 21_1, 21_2, and 21_3 are mounted on a multilayer printed circuit board 400a.

The lower horizontal portion of coil 21_3_C of Rogowski coil 21_3 is formed on the first layer L1 of multilayer printed circuit board 400a. The return wire 21_3_R of Rogowski coil 21_3 is formed on the second layer L2 above the first layer L1. The upper horizontal portion of coil 21_3_C of Rogowski coil 21_3 is formed on the third layer L3 above the second layer L2. A vertical portion is formed connecting the upper and lower horizontal portions of coil 21_3_C using through hole TH3-1 that connects the third layer L3 and first layer L1.

The lower horizontal portion of coil 21_2_C of Rogowski coil 21_2 is formed on the fourth layer L4 above the third layer L3. The return wire 21_2_R of Rogowski coil 21_2 is formed on the fifth layer L5 above the fourth layer L4. The upper horizontal portion of coil 21_2_C of Rogowski coil 21_2 is formed on the sixth layer L6 above the fifth layer L5. Then, a vertical portion is formed connecting the upper and lower horizontal portions of coil 21_2_C using through hole TH6-4 that connects the sixth layer L6 and the fourth layer L4.

The lower horizontal portion of coil 21_1_C of Rogowski coil 21_1 is formed on the seventh layer L7, which is the layer above the sixth layer L6. The return wire 21_1_R of Rogowski coil 21_1 is formed on the eighth layer L8, which is the layer above the seventh layer L7. The upper horizontal portion of coil 21_1_C of Rogowski coil 21_1 is formed on the ninth layer L9, which is the layer above the eighth layer L8. Then, a vertical portion is formed that connects the upper and lower horizontal portions of coil 21_1_C, using through hole TH9-7 that connects the ninth layer L9 and the seventh layer L7.

Figure 10 is an abstract view of the Rogowski coils 21_1, 21_2, and 21_3 shown in Figure 9. In each layer of the multilayer printed circuit board 400a shown in Figure 9, the ninth layer L9 is the top layer, and the first layer L1 is the bottom layer. Therefore, in the Rogowski coils 21_1, 21_2, and 21_3 shown in Figure 10, the Rogowski coil 21_1 is the top layer Rogowski coil, the Rogowski coil 21_3 is the bottom layer Rogowski coil, and the Rogowski coil 21_2 is the intermediate layer between the top layer and the bottom layer.

In this implementation example, the Rogowski coils 21_1, 21_2, and 21_3 have the same size in the depth direction (the vertical direction in FIG. 10). In addition, the distance d between the central axis M1 of the Rogowski coil 21_1 and the central axis M2 of the Rogowski coil 21_2 is the same as the distance d between the central axis M2 of the Rogowski coil 21_2 and the central axis M3 of the Rogowski coil 21_3.

In this implementation example, the return wire 21_1_R of the Rogowski coil 21_1 on the top layer side is positioned closer to the top layer than the central axis M1 of the Rogowski coil 21_1, and the return wire 21_3_R of the Rogowski coil 21_3 on the bottom layer side is positioned closer to the bottom layer than the central axis M3 of the Rogowski coil 21_3, forming an area in the overlapping portion OV where the distance between the return wires of adjacent Rogowski coils is longer than the distance between the central axes of the Rogowski coils. Specifically, in this implementation example, the return wire 21_2_R of the Rogowski coil 21_2 on the middle layer is positioned on the central axis M2 of the Rogowski coil 21_2, and the distance between the return wires 21_1_R and 21_2_R of adjacent Rogowski coils and the distance between the return wires 21_2_R and 21_3_R of adjacent Rogowski coils are longer than the distance d between the central axes of adjacent Rogowski coils.

In this implementation example, the return wire 21_1_R of the Rogowski coil 21_1, the return wire 21_2_R of the Rogowski coil 21_2, and the return wire 21_3_R of the Rogowski coil 21_3 run in parallel over the entire length of the overlapping portion OV. Therefore, if the return wires 21_1_R and 21_2_R are close to each other and the return wires 21_2_R and 21_3_R are close to each other, when a magnetic field is generated around one of these return wires due to a current flowing through that return wire, a current that generates a magnetic field that cancels out this magnetic field may be induced in the other adjacent return wires, which may interfere with current measurement. However, in this implementation example, the return wires 21_1_R and 21_2_R are far away from each other, and the return wires 21_2_R and 21_3_R are also far away from each other, so that each return wire is less susceptible to the current flowing through the other adjacent return wires. This allows highly accurate current measurement using Rogowski coils 21_1, 21_2, and 21_3.

In the embodiment described above, the number M of switching element parts connected in parallel is 4, and the number Ma = M-1 of Rogowski coils is 3. In the embodiment described below, the number M of switching element parts connected in parallel is 5, and the number Ma = M-1 of Rogowski coils is 4. Figure 11 is a plan view illustrating Rogowski coils 21_1, 21_2, 21_3, and 21_4 mounted on multilayer printed circuit board 400A in this embodiment.

In the multilayer printed circuit board 400A, the current path 20_1a of the first switching element unit is inserted into the area surrounded by the Rogowski coils 21_2, 21_3, and 20_4, but not surrounded by the Rogowski coil 21_1. In the multilayer printed circuit board 400A, the current path 20_2a of the second switching element unit is inserted into the area surrounded by the Rogowski coils 21_1, 21_3, and 21_4, but not surrounded by the Rogowski coil 21_2. In the multilayer printed circuit board 400A, the current path 20_3a of the third switching element unit is inserted into the area surrounded by the Rogowski coils 21_1, 21_2, and 21_4, but not surrounded by the Rogowski coil 21_3. In addition, in the multilayer printed circuit board 400A, the current path 20_4a of the fourth switching element unit is inserted into the area surrounded by the Rogowski coils 21_1, 21_2, and 21_3, but not surrounded by the Rogowski coil 21_4. In addition, in the multilayer printed circuit board 400A, the current path 20_5a of the fifth switching element unit is inserted into the area surrounded by all of the Rogowski coils 21_1, 21_2, 21_3, and 21_4. In this case, an overlapping portion OV where the four Rogowski coils 21_1, 21_2, 21_3, and 21_4 are arranged in the depth direction of the multilayer printed circuit board 400A is generated above the current paths 20_2a, 20_3a, 20_4a, and 20_5, to the right of the current path 20_5a, and below the current path 20_5a in FIG. 11.

The Rogowski coil 21_1 surrounds the current paths 20_2a, 20_3a, 20_4a, and 20_5a, and detects the sum of the currents flowing through these current paths. The Rogowski coil 21_2 surrounds the current paths 20_1a, 20_3a, 20_4a, and 20_5a, and detects the sum of the currents flowing through these current paths. The Rogowski coil 21_3 surrounds the current paths 20_1a, 20_2a, 20_4a, and 20_5a, and detects the sum of the currents flowing through these current paths. The Rogowski coil 21_4 surrounds the current paths 20_1a, 20_2a, 20_3a, and 20_5a, and detects the sum of the currents flowing through these current paths.

In this embodiment, two implementation modes of the Rogowski coils 21_1, 21_2, 21_3, and 21_4 are considered. Figure 12 is an abstract diagram showing the Rogowski coils 21_1, 21_2, 21_3, and 21_4 arranged in the depth direction of the multilayer printed circuit board 400A in the first implementation mode.

In the Rogowski coils 21_1, 21_2, 21_3, and 21_4 shown in FIG. 12, the Rogowski coil 21_1 is the Rogowski coil on the top layer side, the Rogowski coil 21_4 is the Rogowski coil on the bottom layer side, and the Rogowski coils 21_2 and 21_3 are the Rogowski coils in the intermediate layers between the top layer and the bottom layer.

Even in this embodiment, the Rogowski coils 21_1, 21_2, 21_3, and 21_4 have the same size in the depth direction (the vertical direction in FIG. 12). In addition, the distance d between the central axis M1 of the Rogowski coil 21_1 and the central axis M2 of the Rogowski coil 21_2, the distance d between the central axis M2 of the Rogowski coil 21_2 and the central axis M3 of the Rogowski coil 21_3, and the distance d between the central axis M3 of the Rogowski coil 21_3 and the central axis M4 of the Rogowski coil 21_4 are the same.

Also in the first aspect, the return wire 21_1_R of the Rogowski coil 21_1 on the top layer side is positioned closer to the top layer than the central axis M1 of the Rogowski coil 21_1, and the return wire 21_4_R of the Rogowski coil 21_4 on the bottom layer side is positioned closer to the bottom layer than the central axis M4 of the Rogowski coil 21_4, thereby forming an area in the overlapping portion OV where the distance between the return wires of adjacent Rogowski coils is longer than the distance d between the central axes of adjacent Rogowski coils. Specifically, in this embodiment, the return wire 21_2_R of the Rogowski coil 21_2 in the middle layer is positioned on the central axis M2 of the Rogowski coil 21_2, and the return wire 21_3_R of the Rogowski coil 21_3 in the middle layer is positioned on the central axis M3 of the Rogowski coil 21_3, so that the distance between the return wires 21_1_R and 21_2_R of adjacent Rogowski coils and the distance between the return wires 21_3_R and 21_4_R of adjacent Rogowski coils are longer than the distance d between the central axes of the adjacent Rogowski coils. Therefore, according to this embodiment, the influence of the current flowing through one return wire on the other return wire between the return wires 21_1_R and 21_2_R and between the return wires 21_3_R and 21_4_R is reduced, and the accuracy of current measurement can be improved.

Figure 13 is an abstract diagram of Rogowski coils 21_1, 21_2, 21_3, and 21_4 arranged in the depth direction of multilayer printed circuit board 400A in the second embodiment.

In FIG. 13, Rogowski coil 21_1 is the Rogowski coil on the top layer side, Rogowski coil 21_4 is the Rogowski coil on the bottom layer side, and Rogowski coils 21_2 and 21_3 are Rogowski coils in the intermediate layers between the top layer and the bottom layer. Furthermore, each Rogowski coil has the same size in the depth direction, and the distance d between the central axis M1 of Rogowski coil 21_1 and the central axis M2 of Rogowski coil 21_2, the distance d between the central axis M2 of Rogowski coil 21_2 and the central axis M3 of Rogowski coil 21_3, and the distance d between the central axis M3 of Rogowski coil 21_3 and the central axis M4 of Rogowski coil 21_4 are the same.

In this second embodiment, the return wire 21_1_R of the Rogowski coil 21_1 on the top layer side is positioned closer to the top layer than the central axis M1 of the Rogowski coil 21_1, and the return wire 21_4_R of the Rogowski coil 21_4 on the bottom layer side is positioned closer to the bottom layer than the central axis M4 of the Rogowski coil 21_4. In the second embodiment, the return wire 21_2_R of the Rogowski coil 21_2 in the middle layer and the return wire 21_3_R of the Rogowski coil 21_3 in the middle layer are positioned at two positions that divide the section D between the return wire 21_4_R of the Rogowski coil 21_4 on the bottom layer side and the return wire 21_4_R of the Rogowski coil 21_4 on the bottom layer side into two equal parts Ma-1, i.e., three. According to this embodiment, the distance between adjacent return lines 21_1_R and 21_2_R, the distance between adjacent return lines 21_2_R and 21_3_R, and the distance between adjacent return lines 21_3_R and 21_4_R can all be maximized and made longer than the distance d between adjacent central axes. Therefore, according to this embodiment, between the return lines 21_1_R and 21_2_R, between the return lines 21_2_R and 21_3_R, and between the return lines 21_3_R and 21_4_R, the influence of the current flowing through one return line on the other return line can be reduced, and the accuracy of current measurement can be improved. Therefore, the accuracy of current measurement using four Rogowski coils can be improved.

<Other embodiments>
Although one embodiment of the present invention has been described above, other embodiments of the present invention are also possible. For example, the following embodiments are possible.

(1) In the above embodiment, a Rogowski coil is provided in the current path on the source side of the power switching elements connected in parallel, but a Rogowski coil may also be provided in the current path on the drain side of the power switching elements.

(2) In the above embodiment, the detection signal obtained from the Rogowski coil is integrated to obtain a current detection value, and the current detection value is compared with a threshold value th to determine whether a short circuit fault has occurred. However, instead of doing so, the detection signal obtained from the Rogowski coil may be compared with a threshold value to determine whether a short circuit fault has occurred.

(3) This invention may be applied to power conversion devices other than inverters, such as DC/DC converters.

(4) In the above embodiment, a MOSFET is given as an example of a power switching element, but the power switching element is not limited to this and may be another power switching element such as an IGBT (Insulated Gate Bipolar Transistor).

100...power conversion device, 200...upper device, 2a, 2b...drive unit, 1...control unit, 20_1, 20_2, 20_3, 20_4...switching element unit, 27...power switching element, 28...diode, 24...drive control unit, 50...short circuit protection device, 21_1, 21_2, 21_3, 21_4...Rogowski coil, 21_1_C, 21_2_C, 21_3_C...coil, 21_1_R, 21_2_R, 21_ 3_R, 21_4_R...return line, 22_1, 22_2, 22_3...integrator, 23...short circuit determination section, 301, 302, 303...comparator, 340...OR operator, 311, 312, 313, 314...NOT operator, 321, 322, 323, 324...AND operator, 331, 332, 333, 334...on-delay operator, 400...substrate, 400a...multilayer printed circuit board, M1, M2, M3, M4...center axis.

Claims (4)

2. A short-circuit protection device for a power conversion device that supplies power to a load via a plurality of switching element units connected in parallel,
a number Ma=M-1 current detectors, the number Ma being one less than the number M of the plurality of switching element units, each of the Ma current detectors including a number Ma Rogowski coils surrounding current paths of two or more switching element units in the plurality of switching element units;
a short circuit determination unit that determines that a short circuit has occurred in the plurality of switching element units based on detection signals obtained from the Ma current detectors, and outputs a cutoff instruction signal to stop on/off driving of the plurality of switching element units,
an N-th current detector (N is an integer from 1 to Ma) among the Ma current detectors detects a sum of currents flowing through all switching element units other than the N-th switching element unit among the 1st to Mth switching element units;
the short circuit determination unit determines that a short circuit has occurred in the Mth switching element unit when all of the current detection values by the Ma current detectors exceed a threshold value, and determines that a short circuit has occurred in a switching element unit that is not the subject of current detection in the one current detector when the current detection value of one of the Ma current detectors does not exceed the threshold value and the current detection values of the other Ma-1 current detectors exceed the threshold value;
The Ma is 3 or more,
The Ma Rogowski coils are mounted on a multi-layer printed circuit board,
The multilayer printed circuit board has an overlapping portion in which the Ma Rogowski coils are aligned in a depth direction,
A short circuit protection device characterized in that the return wire of the Rogowski coil on the top layer side of the multilayer printed circuit board is positioned closer to the top layer than the central axis of the Rogowski coil, and the return wire of the Rogowski coil on the bottom layer side of the multilayer printed circuit board is positioned closer to the bottom layer than the central axis of the Rogowski coil, thereby forming an area in the overlapping portion in which the distance between the return wires of adjacent Rogowski coils in the depth direction is longer than the distance between the central axes of the adjacent Rogowski coils. The short circuit protection device according to claim 1, characterized in that the return wire of the Rogowski coil in the intermediate layer between the top layer and the bottom layer is located at the same position as the central axis of the Rogowski coil. The short circuit protection device of claim 1, characterized in that the return wire of the Rogowski coil in the intermediate layer between the top layer and the bottom layer is located at a position that divides the section between the return wire of the Rogowski coil on the top layer side and the return wire of the Rogowski coil on the bottom layer side into Ma-1 equal parts. The short circuit protection device according to any one of claims 1 to 3, wherein the switching element section includes a wide gap semiconductor element.

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