JP2019106784A - Power conversion device - Google Patents

Abstract

To provide a voltage type power conversion device capable of easily detecting short-circuit of a charge storage element.SOLUTION: According to one embodiment, there is provided a power conversion device comprising a voltage type main circuit part, a magnetic flux sensor, and a control part. The main circuit part has a plurality of switching elements and a charge storage element, and performs AC-DC conversion by switching of the plurality of switching elements. The magnetic flux sensor detects short-circuit of the charge storage element by variation of a magnetic-flux amount of a space in association with operation of the main circuit part. The control part controls operation of the AC-DC conversion of the main circuit part and performs protection operation of the main circuit part according to detection of the short-circuit by the magnetic flux sensor.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a power converter.

  There is known a power converter (for example, a voltage type inverter) including a voltage type main circuit unit having a charge storage element (for example, a direct current capacitor) and a plurality of switching elements. In such a voltage type power converter, it is practiced to provide a short circuit detection circuit for detecting a short circuit (DC short circuit) of the charge storage element. The short circuit detection circuit has a short circuit detection capacitor having a capacitance smaller than that of the main charge storage element of the main circuit portion and a current sensor, and the current flowing out of the short circuit detection capacitor when the main charge storage element is shorted is a current sensor A short circuit is detected by detecting (see, for example, Patent Document 1).

  However, when the short circuit detection circuit is provided, the number of parts is increased, resulting in an increase in size and cost of the power conversion device. In addition, since the short circuit detection circuit has the same potential as the main charge storage element, it is necessary to consider insulation from the surroundings, and the structure of the insulation is complicated. Furthermore, although the short circuit current flowing to the main charge storage element and the short circuit current flowing to the short circuit detection capacitor are determined by the capacitance ratio of each element, in fact, the current flowing to the short circuit detection capacitor It is affected by the switching of elements and the like, and the design is complicated. In addition, the difference between the steady state current and the short circuit current is small, and labor is required to ensure protection coordination.

  Therefore, in a voltage type power converter, it is desirable to be able to easily detect a short circuit of the charge storage element.

JP, 2016-19336, A

  Embodiments of the present invention provide a voltage type power converter capable of easily detecting a short circuit of a charge storage element.

  According to an embodiment of the present invention, there is provided a power converter including a voltage type main circuit unit, a magnetic flux sensor, and a control unit. The main circuit unit includes a plurality of switching elements and a charge storage element, and performs AC / DC conversion by switching the plurality of switching elements. The magnetic flux sensor detects a short circuit of the charge storage element based on a change in the amount of magnetic flux in the space due to the operation of the main circuit unit. The control unit controls the operation of the AC / DC conversion of the main circuit unit, and performs a protection operation of the main circuit unit according to the detection of the short circuit by the magnetic flux sensor.

  A voltage type power converter capable of easily detecting a short circuit of a charge storage element is provided.

It is a block diagram showing the power converter concerning a 1st embodiment typically. It is a block diagram showing the power converter concerning a 2nd embodiment typically. Fig.3 (a) and FIG.3 (b) are block diagrams which represent typically a part of power converter device which concerns on 2nd Embodiment. FIG. 4A and FIG. 4B are a plan view and a cross-sectional view schematically showing a part of the power conversion device according to the second embodiment. It is a block diagram showing the power converter concerning a 3rd embodiment typically.

Hereinafter, each embodiment will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of sizes between parts, and the like are not necessarily the same as the actual ones. In addition, even in the case of representing the same portion, the dimensions and ratios may be different from one another depending on the drawings.
In the specification of the present application and the drawings, the same elements as those described above with reference to the drawings are denoted by the same reference numerals, and the detailed description will be appropriately omitted.

First Embodiment
FIG. 1 is a block diagram schematically illustrating the power conversion device according to the first embodiment.
As shown in FIG. 1, the power conversion device 10 includes a main circuit unit 12, a magnetic flux sensor 14, and a control unit 16.

  The main circuit unit 12 includes a first converter 21 and a second converter 22. The first converter 21 has two AC terminals 21a and 21b and three DC terminals 21p, 21n and 21c. Each of the AC terminals 21a and 21b is connected to an AC power supply 2 via, for example, a transformer 4. Thereby, the alternating current power from the alternating current power supply 2 is supplied to the first converter 21.

  The AC power supply 2 is, for example, various power generation devices, a commercial power grid, or the like. The AC power supplied from the AC power supply 2 is, for example, single-phase AC power. The AC power of the AC power supply 2 is not limited to single-phase AC power, and may be three-phase AC power or the like. Transformer 4 may be provided in power conversion device 10 or may be provided separately from power conversion device 10.

  The first converter 21 converts the input AC power (first AC power) into DC power having three levels of a positive potential P, a negative potential N, and a neutral point potential O. Hereinafter, each of the direct current terminals 21p, 21n, and 21c is referred to as a positive potential terminal 21p, a negative potential terminal 21n, and a neutral point terminal 21c, respectively.

The first converter 21 sets the positive potential terminal 21 p to the positive potential P, sets the negative potential terminal 21 n to the negative potential N, and sets the neutral point terminal 21 c to the neutral point potential O. The neutral point potential O is an intermediate potential between the positive potential P and the negative potential N. Thereby, the first converter 21 generates a DC voltage V _PO (first DC voltage) between the positive potential terminal 21p and the neutral point terminal 21c, and the first converter 21 generates the DC voltage VPO between the neutral point terminal 21c and the negative potential terminal 21n. In the meantime, a DC voltage V _ON (second DC voltage) is generated. Therefore, the DC voltage V _DC between the positive potential terminal 21 p and the negative potential terminal 21 n is V _DC = V _PO + V _ON .

  The second converter 22 is connected to each of the DC terminals 21p, 21n, 21c, and is also connected to the AC load 8 via the transformer 6. The AC load 8 is, for example, a power system different from the AC power supply 2. The second converter 22 converts the DC power input from the first converter 21 into AC power (second AC power) of a desired frequency and voltage value according to the AC load 8, and AC power is converted into AC power. The load 8 is supplied.

  As described above, the power conversion device 10 once converts the AC power of the AC power supply 2 into DC power, converts the DC power into another AC power, and supplies the AC power to the AC load 8. The power converter 10 is used, for example, in a grid-connected facility of a BTB (Back to Back) method. The first converter 21 is a so-called three-level converter. The second converter 22 is a three-level inverter. The first converter 21 may be a two-level converter. The second converter 22 may be a two-level inverter. The first converter 21 and the second converter 22 may be multilevel converters of three or more levels.

  Further, in the power conversion device 10, the AC power on the AC load 8 side can be converted into AC power corresponding to the AC power supply 2 and supplied to the AC power supply 2. In this case, the first converter 21 functions as an inverter, and the second converter 22 functions as a converter.

  The AC load 8 is not limited to the power system, and may be, for example, an induction motor. Power converter 10 may be used for drive control of an induction motor, etc.

  The first converter 21 includes a plurality of switching elements 41, a plurality of rectifying elements 42 and 43, and a plurality of charge storage elements 44 and 45. In this example, the first converter 21 includes eight switching devices 41, eight rectifying devices 42, four rectifying devices 43, two charge storage devices 44, and two charge storage devices And 45. Each switching element 41 is bridged. Each rectification element 42 is connected in antiparallel to each switching element 41.

  The switching element 41 has a pair of main terminals and a control terminal. The control terminal is used to switch between an on state in which current flows between the respective main terminals and an off state in which no current substantially flows between the respective main terminals. For the switching element 41, for example, a self arc extinguishing element such as a gate turn off thyristor (GTO) or an insulated gate bipolar transistor (IGBT) is used. The control terminal is, for example, a gate terminal.

Each charge storage element 44 is provided between the positive potential terminal 21p and the neutral point terminal 21c. Each charge storage element 44 is electrically connected between the positive potential terminal 21p and the neutral point terminal 21c. Each charge storage element 45 is provided between the neutral point terminal 21c and the negative potential terminal 21n. Each charge storage element 45 is electrically connected between the neutral point terminal 21c and the negative potential terminal 21n. Each charge storage element 44, 45 smoothes the DC voltage V _PO , V _ON . Each charge storage element 44, 45 is, in other words, a smoothing capacitor or a direct current capacitor.

  The first converter 21 is a single-phase bridge-connected voltage converter and has four arms AA, AB, AX, AY. The configurations of the arms AA, AB, AX, AY of the respective phases connected to the respective AC terminals 21a, 21b are substantially the same. Therefore, here, two arms AA and AX connected to the AC terminal 21a will be described as an example.

  An upper arm AA on the positive side includes two switching elements SA1 and SA2 connected in series, rectifying elements DA1 and DA2 connected in antiparallel to the switching elements SA1 and SA2, and each switching element SA1, Charge storage connected between the rectifying element DA3 connected between the series connection point of SA2 and the neutral point terminal 21c, the connecting point of the switching element SA1 and the positive potential terminal 21p, and the neutral point terminal 21c And an element CA1.

  The lower arm AX on the negative side includes two switching elements SX1 and SX2 connected in series, rectifying elements DX1 and DX2 connected in antiparallel to the switching elements SX1 and SX2, and each switching element SX1, A charge storage element connected between a connection point between the series connection point of SX2 and the neutral point terminal 21c and a connection point between the switching element SX2 and the negative potential terminal 21n and the neutral point terminal 21c And an element CA2.

  The upper arm AA and the lower arm AX are connected in series between the positive potential terminal 21p and the negative potential terminal 21n, and the series connection point of the upper arm AA and the lower arm AX is connected to the AC terminal 21a. The potential at the series connection point of the switching elements SA1 and SA2 is clamped to the neutral point potential O via the rectifying element DA3. Similarly, the potential at the series connection point of the switching elements SX1 and SX2 is clamped to the neutral point potential O via the rectifying element DX3. The rectifying elements DA1, DA2, DX1, DX2 (each rectifying element 42) are so-called reflux diodes. The rectifying elements DA3 and DX3 (respective rectifying elements 43) are so-called clamp diodes.

  The configuration of the upper arm AB is substantially the same as the configuration of the upper arm AA. The configuration of the lower arm AY is substantially the same as the configuration of the lower arm AX. Thereby, according to the switching of each switching element 41, the potentials of AC terminals 21a and 21b are clamped at any of three levels of positive potential terminal 21p, negative potential terminal 21n and neutral point terminal 21c. . The first converter 21 is a so-called neutral-point-clamped (NPC) converter (converter).

  The second converter 22 includes a plurality of switching elements 51, a plurality of rectifying elements 52, 53, and a plurality of charge storage elements 54, 55. The second converter 22 is, like the first converter 21, a neutral point clamp converter (inverter). The configuration of the second converter 22 is substantially the same as the configuration of the first converter 21, and thus the detailed description is omitted. In the second converter 22, the side connected to the positive potential terminal 21p, the negative potential terminal 21n, and the neutral point terminal 21c is the DC side, and the side connected to the AC load 8 is the AC side (AC terminals 22a, 22b) Become.

  As described above, the main circuit unit 12 includes a plurality of switching elements 41 and 51 and a plurality of charge storage elements 44 45 45 55, and performs AC / DC conversion by switching the plurality of switching elements 41 51. I do. In this example, the main circuit unit 12 includes a plurality of charge storage elements 44, 45, 54, 55. For example, when the main circuit unit 12 is a two-level inverter or the like, the number of charge storage elements may be one.

  The magnetic flux sensor 14 is provided side by side with the main circuit unit 12. The magnetic flux sensor 14 is disposed, for example, in proximity to the main circuit unit 12. The magnetic flux sensor 14 detects a short circuit of the charge storage elements 44, 45, 54, 55 based on a change in the amount of magnetic flux in the space caused by the operation of the main circuit unit 12. The magnetic flux sensor 14 detects, for example, a change in the amount of magnetic flux in space due to a change in current flowing through the entire main circuit unit 12. The magnetic flux sensor 14 is connected to the control unit 16. The magnetic flux sensor 14 inputs the detection result to the control unit 16.

  For example, a Hall element or a magnetic impedance element is used for the magnetic flux sensor 14. The magnetic flux sensor 14 is a non-penetrating sensor that does not have a through hole or the like for inserting a conductor. The magnetic flux sensor 14 is different from, for example, a penetrating sensor such as a penetrating CT (Current Transformer).

  The control unit 16 controls the AC / DC conversion operation of the main circuit unit 12. The control unit 16 is connected to control terminals of the switching elements 41 and 51 of the main circuit unit 12. Thereby, the control unit 16 controls the switching of each of the switching elements 41 and 51, and controls the operation of the AC-DC conversion of the main circuit unit 12.

  Further, the control unit 16 controls the AC / DC conversion operation of the main circuit unit 12 and performs a protection operation of the main circuit unit 12 according to the detection of the short circuit by the magnetic flux sensor 14. When the amount of magnetic flux detected by the magnetic flux sensor 14 becomes equal to or greater than a predetermined value, the control unit 16 determines that any one of the charge storage elements 44, 45, 54, 55 has a short circuit. The control of the operation of the AC / DC conversion shifts to the control of the protection operation of the main circuit unit 12.

  The protection operation of the main circuit unit 12 is, for example, stopping of the main circuit unit 12. For example, in response to the detection of the short circuit by the magnetic flux sensor 14, the control unit 16 stops the protection operation of the main circuit unit 12. Thereby, for example, the expansion of the failure of each switching element 41, 51 can be suppressed.

  The protection operation of the main circuit unit 12 may be, for example, a decrease in output voltage of each of the converters 21 and 22 or a decrease in active power of the second AC power output from the second converter 22.

  As described above, in the power conversion device 10 according to the present embodiment, the protection operation of the main circuit unit 12 is performed according to the detection of the short circuit of the charge storage elements 44, 45, 54, 55 by the magnetic flux sensor 14. Thus, in the power conversion device 10, for example, the volume of the additional circuit can be reduced compared to the case where the short circuit detection circuit using the short circuit detection capacitor or the like is provided. In the power conversion device 10, it is possible to suppress an increase in the size and cost of the device due to the increase in the number of parts.

  In the case of using a short circuit detection circuit, it was necessary to consider insulation from the surroundings, but in the power conversion device 10, the magnetic flux sensor 14 can be installed at a position spatially separated from the main circuit portion 12. , Structural isolation design can be facilitated.

  In addition, when a short circuit detection circuit is used, the current flowing through the short circuit detection circuit is affected by the parasitic inductance of the circuit and the switching of the switching element, and the design is complicated. Furthermore, the difference between the steady state and the short circuited current is small, and labor is required to ensure protection coordination. On the other hand, in the power conversion device 10, “the amount of magnetic flux B (= μH) / the current I in the vicinity” is obtained. It will be a difference. Since the current difference between the main circuit 12 at the time of regular operation and short circuit is large, for example, about 10 times to 100 times, protection coordination can be ensured without adjusting the detection level severely, which facilitates design. Can.

  Thus, in the power conversion device 10 according to the present embodiment, the short circuit of the charge storage elements 44, 45, 54, 55 can be easily detected.

Second Embodiment
FIG. 2 is a block diagram schematically showing a power conversion device according to a second embodiment.
As shown in FIG. 2, the power conversion device 10 a includes a plurality of magnetic flux sensors 14 a and 14 b. The same reference numerals are given to components substantially the same in function and configuration as the first embodiment, and detailed description will be omitted.

  Magnetic flux sensor 14a is provided corresponding to charge storage element CA1 for upper arm AA. The magnetic flux sensor 14 b is provided corresponding to the charge storage element CA 2 for the lower arm AX. As described above, in the power conversion device 10a, a plurality of magnetic flux sensors 14 are provided corresponding to each of the charge storage element CA1 for the upper arm AA and the charge storage element CA2 for the lower arm AX.

Fig.3 (a) and FIG.3 (b) are block diagrams which represent typically a part of power converter device which concerns on 2nd Embodiment.
For example, when the switching elements SA1, SA2 and SX1 are simultaneously turned on due to a failure or the like, as shown in FIG. 3A, the charge storage element CA1 of the upper arm AA is shorted, and the switching element SA1, A short circuit current IS1 flows through SA2, SX1 and the rectifying element DX3.

  Further, for example, when the switching elements SA2, SX1, and SX2 are simultaneously turned on, as illustrated in FIG. 3B, the charge storage element CA2 of the lower arm AX is short-circuited, and the rectifying element DA3 and the switching A short circuit current IS2 flows through the elements SA2, SX1, and SX2.

  The magnetic flux sensor 14a is provided side by side with the wiring 61 through which the short circuit current IS1 flows when the charge storage element CA1 is shorted, and detects a change in the amount of magnetic flux in the space due to a change in current flowing through the wiring 61.

  Similarly, the magnetic flux sensor 14b is provided in line with the wiring 62 through which the short circuit current IS2 flows when the charge storage element CA2 is shorted, and detects a change in the amount of magnetic flux in the space due to a change in current flowing through the wiring 62.

  The magnetic flux sensors 14 a and 14 b are connected to the control unit 16. The magnetic flux sensors 14 a and 14 b input the detection result to the control unit 16. The control unit 16 performs a protection operation of the main circuit unit 12 in response to the detection of the short circuit by any of the plurality of magnetic flux sensors 14a and 14b.

FIG. 4A and FIG. 4B are a plan view and a cross-sectional view schematically showing a part of the power conversion device according to the second embodiment.
As shown in FIGS. 4A and 4B, in this example, the wiring 61 is a conductor plate 70 having a predetermined width. The conductor plate 70 includes, for example, a first insulating portion 72a, a first conductive portion 74a provided on the first insulating portion 72a, and a second insulating portion 72b provided on the first conductive portion 74a. A second conductive portion 74b provided on the second insulating portion 72b and a third insulating portion 72c provided on the second conductive portion 74b.

  The first conductive portion 74a is connected to one main terminal 41a of the switching element SA1. The second conductive portion 74b is connected to the other main terminal 41b of the switching element SA1. Thus, by using the conductor plate 70 as the wiring 61, the electrical resistance of the wiring 61 can be reduced. Further, by laminating the first conductive portion 74 a and the second conductive portion 74 b, the parasitic inductance of the wiring 61 can be reduced. The conductor plate 70 is, for example, a parallel flat laminated bus bar.

  The magnetic flux sensor 14 a is provided to face the conductor plate 70. The magnetic flux sensor 14a is provided, for example, on the third insulating portion 72c. The magnetic flux sensor 14a may be provided, for example, on the first insulating portion 72a side. The magnetic flux sensor 14 a may be disposed in contact with the surface of the conductor plate 70 or may be disposed apart from the surface of the conductor plate 70.

  Moreover, although illustration is abbreviate | omitted, the wiring 62 is also the conductor board 70 similarly to the wiring 61. FIG. The magnetic flux sensor 14 b is provided to face the conductor plate 70 in the same manner as the magnetic flux sensor 14 b.

  As described above, in the power conversion device 10a according to this embodiment, a plurality of magnetic flux sensors 14 are provided corresponding to each of the charge storage element CA1 for the upper arm AA and the charge storage element CA2 for the lower arm AX. Be Thereby, for example, a short circuit of the charge storage elements 44, 45, 54, 55 can be detected more reliably.

  In the power converter 10a, the magnetic flux sensor 14a detects a change in the amount of magnetic flux in the space due to a change in the current flowing through the wire 61, and the magnetic flux sensor 14b detects the amount of magnetic flux in the space due to the change in the current flowing through the wire 62 To detect changes in Thereby, for example, a short circuit of the charge storage elements 44, 45, 54, 55 can be detected more reliably.

  On the other hand, as described in the first embodiment, when the change in the amount of magnetic flux in the space caused by the change in the current flowing through the entire main circuit unit 12 is detected by one magnetic flux sensor 14, it is simpler. The short circuit of the charge storage elements 44, 45, 54, 55 can be detected with the above configuration.

  In addition, for example, it is difficult to insert a penetrating CT or the like into the conductor plate 70. On the other hand, in the power conversion device 10a, the non-penetrating magnetic flux sensors 14a and 14b are provided opposite to the conductor plate 70 to detect the change in the amount of magnetic flux in the space due to the change in the current flowing through the conductor plate 70. can do. Therefore, even when the wires 61 and 62 are the conductive plate 70, a short circuit of the charge storage elements 44, 45, 54 and 55 can be reliably detected with a simple configuration.

Third Embodiment
FIG. 5 is a block diagram schematically showing a power conversion device according to a third embodiment.
As shown in FIG. 5, in the power conversion device 10b, the magnetic flux sensor 14 is provided side by side with the wiring 63 connected to the neutral point terminal 21c. The wiring 63 is, for example, a conductor plate. Similar to the magnetic flux sensors 14 a and 14 b of the second embodiment, the magnetic flux sensor 14 is provided to face the wiring 63 which is a conductor plate.

  Both the short circuit current IS1 at the time of the short circuit of the charge storage element CA1 and the short circuit current IS2 at the short circuit of the charge storage element CA2 flow in the wiring 63 (see FIGS. 3A and 3B). Therefore, the magnetic flux sensor 14 detects a change in the amount of magnetic flux in the space due to a change in the current flowing through the wiring 63. Thereby, in the power conversion device 10b, one magnetic flux sensor 14 can detect a short circuit of the charge storage element CA1 of the upper arm AA and a short circuit of the charge storage element CA2 of the lower arm AX. Therefore, in the power conversion device 10b, a short circuit of the charge storage elements 44, 45, 54, 55 can be detected with a simpler configuration.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

  DESCRIPTION OF SYMBOLS 2 ... AC power supply 4, 6 ... Transformers 8: AC load 10, 10a, 10b Power conversion device 12 Main circuit part 14, 14a, 14b Flux sensor 16 Control part 21st 1 converter, 21a, 21b: AC terminal, 21c, 21p, 21n: DC terminal, 22: second converter, 41, 51: switching element 42, 43, 52, 53: rectifying element, 44, 45, 54 , 55: charge storage element, 61 to 63: wiring, 70: conductor plate, 72a: first insulating portion, 72b: second insulating portion, 72c: third insulating portion, 74a: first conductive portion, 74b: second Conductive part, AA, AB, AX, AY ... arm

Claims (5)

A voltage type main circuit unit having a plurality of switching elements and a charge storage element, and performing AC / DC conversion by switching the plurality of switching elements;
A magnetic flux sensor that detects a short circuit of the charge storage element based on a change in the amount of magnetic flux in the space due to the operation of the main circuit unit;
A control unit that controls the operation of the AC / DC conversion of the main circuit unit and performs a protection operation of the main circuit unit according to the detection of a short circuit by the magnetic flux sensor;
Power converter equipped with.   The power conversion device according to claim 1, wherein the magnetic flux sensor is provided side by side with a wire through which a short circuit current flows when the charge storage element is shorted, and detects a change in an amount of magnetic flux in space due to a change in current flowing through the wire. The wiring is a conductor plate,
The power conversion device according to claim 2, wherein the magnetic flux sensor is provided to face the conductor plate. The main circuit unit includes the charge storage element for the upper arm and the charge storage element for the lower arm,
The power conversion device according to any one of claims 1 to 3, wherein a plurality of the magnetic flux sensors are provided corresponding to each of the charge storage element for the upper arm and the charge storage element for the lower arm. The main circuit portion has three DC terminals of a positive potential terminal, a negative potential terminal, and a neutral point terminal, and a plurality of AC terminals, and the AC power supplied from the plurality of AC terminals is positive. It can be converted to DC power with three levels: potential, negative potential, and neutral point potential,
The power conversion device according to claim 2, wherein the magnetic flux sensor is provided side by side with the wiring connected to the neutral point terminal.

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