JP7645840B2 - Power Conversion Equipment - Google Patents

Description

An embodiment of the present invention relates to a power conversion device.

There is a power conversion device that includes multiple power conversion circuits whose primary sides are connected in series, and multiple charge storage elements provided on the primary sides of each of the multiple power conversion circuits. The primary sides of the multiple power conversion circuits are connected in series and are connected to a DC power source at both ends of the series connection. The secondary sides of the multiple power conversion circuits are connected to another power source, a load, or the like. The multiple power conversion circuits convert the DC power on the primary side supplied from the DC power source into another power corresponding to the secondary side, and supply the converted power to the secondary side.

In such a power conversion device, the primary sides of multiple power conversion circuits are connected in series, allowing the DC voltage of a DC power source to be shared among multiple power conversion circuits, and the rated voltage of elements used in the multiple power conversion circuits can be reduced. Such power conversion devices are used in power systems that handle relatively high DC voltages, such as power feeding systems for railway vehicles.

In such a power conversion device, when a short circuit occurs on the primary side of any of the multiple power conversion circuits, the operation of the multiple power conversion circuits is stopped. However, if the operation of the multiple power conversion circuits is suddenly stopped while power is being supplied from the primary side to the secondary side of the multiple power conversion circuits, the voltage of healthy charge storage elements provided in the power conversion circuits that are not short-circuited among the multiple charge storage elements may increase, which may lead to an expanded failure of the healthy charge storage elements.

As a countermeasure, it has been proposed to increase the capacity of the multiple charge storage elements or to provide an overvoltage protection circuit that suppresses the overvoltage of the multiple charge storage elements. However, there are concerns that these countermeasures will lead to an increase in the size and cost of the device. For this reason, it is desirable to have a power conversion device that can suppress escalating failures with a simpler configuration.

JP 2018-98834 A

An embodiment of the present invention provides a power conversion device that can suppress escalating failures with a simpler configuration.

According to an embodiment of the present invention, a power conversion circuit includes a plurality of power conversion circuits having primary sides connected in series, a plurality of charge storage elements provided on the primary sides of each of the plurality of power conversion circuits, and a control unit that controls the operation of each of the plurality of power conversion circuits, the primary sides of the plurality of power conversion circuits are connected in series and are connected to a DC power source at both ends of the series connection, the plurality of power conversion circuits convert DC power of the primary side supplied from the DC power source into another power corresponding to the secondary side and supply the converted power to the secondary side, and the control unit controls the operation of each of the plurality of power conversion circuits and controls the supply of power from the primary side to the secondary side to be controlled by the plurality of power conversion circuits. and when a short-circuit fault on the primary side of any of the plurality of power conversion circuits is detected, operation of the power conversion circuit among the plurality of power conversion circuits in which a short-circuit fault on the primary side has been detected is stopped, and for the power conversion circuits in which a short-circuit fault on the primary side has not been detected, an operation is performed to gradually reduce the magnitude of the current flowing in the primary side circuit of the plurality of power conversion circuits based on the magnitude of the current flowing in the primary side circuit of the detected plurality of power conversion circuits, and the operation is terminated in response to the magnitude of the current flowing in the primary side circuit becoming equal to or less than a predetermined value .

A power conversion device is provided that can suppress escalating failures with a simpler configuration.

1 is a circuit diagram illustrating a power conversion device according to an embodiment of the present invention;

Each embodiment will be described below with reference to the drawings.
In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed descriptions thereof will be omitted as appropriate.

FIG. 1 is a circuit diagram illustrating a power conversion device according to an embodiment.
As shown in FIG. 1 , the power conversion device 10 includes a plurality of power conversion circuits 11 and 12 , a plurality of charge storage elements 21 and 22 , and a control unit 30 .

The primary sides of the multiple power conversion circuits 11, 12 are connected in series. The multiple charge storage elements 21, 22 are provided on the primary side of each of the multiple power conversion circuits 11, 12. In this example, the power conversion device 10 includes two power conversion circuits 11, 12 and two charge storage elements 21, 22 corresponding to each of the two power conversion circuits 11, 12. However, the number of power conversion circuits and the number of charge storage elements provided in the power conversion device 10 are not limited to two and may be three or more. The number of power conversion circuits and the number of charge storage elements may be any number.

The primary sides of the power conversion circuits 11 and 12 are connected in series and are connected to the DC power source 2 at both ends of the series connection. The power conversion circuit 11 has a pair of primary side terminals 11a and 11b. Similarly, the power conversion circuit 12 has a pair of primary side terminals 12a and 12b. One terminal 11a of the power conversion circuit 11 is connected to the positive electrode of the DC power source 2. The other terminal 11b of the power conversion circuit 11 is connected to one terminal 12a of the power conversion circuit 12. The other terminal 12b of the power conversion circuit 12 is connected to the negative electrode of the DC power source 2. In this way, the primary sides of the two power conversion circuits 11 and 12 are connected in series and are connected to the DC power source 2 at both ends of the series connection.

In this way, by connecting the primary sides of the power conversion circuits 11 and 12 in series and connecting both ends of the series connection to the DC power source 2, the DC voltage of the DC power source 2 can be shared by the power conversion circuits 11 and 12. In this example, the DC voltage applied to the primary sides of each of the power conversion circuits 11 and 12 can be half the DC voltage of the DC power source 2. This allows the rated voltage of the elements used in the power conversion circuits 11 and 12 to be reduced.

The charge storage element 21 is provided between a pair of primary side terminals 11a, 11b of the power conversion circuit 11. The charge storage element 22 is provided between a pair of primary side terminals 12a, 12b of the power conversion circuit 12. As a result, the charge storage elements 21, 22 stabilize, for example, the DC voltage applied to the primary sides of the power conversion circuits 11, 12. The charge storage elements 21, 22 suppress, for example, noise superimposed on the DC voltage applied to the primary sides of the power conversion circuits 11, 12. The charge storage elements 21, 22 are, for example, capacitors.

The secondary side of the power conversion circuits 11 and 12 is connected to another power source, a load, etc. The power conversion circuits 11 and 12 convert the DC power on the primary side supplied from the DC power source 2 into another power corresponding to the secondary side, and supply the converted power to the secondary side. The power conversion circuits 11 and 12 have, for example, multiple switching elements, and perform power conversion by switching the multiple switching elements. However, the configuration of the power conversion circuits 11 and 12 may be any configuration that can appropriately convert the DC power on the primary side into another power corresponding to the secondary side.

When the power conversion circuits 11 and 12 have multiple switching elements, the rated voltage of the multiple switching elements can be lowered by connecting the primary sides of the power conversion circuits 11 and 12 in series. In this way, by using switching elements with a low rated voltage, it is possible to reduce switching losses that occur when the switching elements are switched. This makes it possible, for example, to suppress heat generation by the switching elements and suppress the increase in size of the device caused by heat dissipation measures for the switching elements.

The power conversion device 10 is used, for example, in a power feeding system for railway vehicles. In this case, the DC power source 2 is, for example, a DC overhead line. The secondary sides of the power conversion circuits 11 and 12 are connected to a power storage device using, for example, a storage battery. In this case, the secondary sides of the power conversion circuits 11 and 12 are connected to each other in parallel. In other words, the secondary sides of the power conversion circuits 11 and 12 are each connected to both poles of the power storage device.

The power conversion circuits 11 and 12 convert the primary side DC power supplied from the DC power source 2 (overhead line) into another DC power corresponding to the storage device, and supply the converted DC power to the storage device. The DC voltage of the overhead line is, for example, 1500V. The maximum voltage of the storage device is, for example, 750V. In this way, the power conversion device 10 supplies DC power to the storage device based on the DC power of the overhead line, and charges the storage device, thereby suppressing an increase in the overhead line voltage due to, for example, surplus regenerative power. In this case, the power conversion circuits 11 and 12 further have the function of converting the secondary side DC power of the storage device into another DC power corresponding to the overhead line, and supplying the converted DC power to the overhead line. This makes it possible to suppress a drop in the overhead line voltage due to, for example, the operation of a railway vehicle.

When the power conversion circuits 11 and 12 output DC power to the secondary side, the power conversion circuit 11 has a pair of secondary side terminals 11c and 11d. Similarly, the power conversion circuit 12 has a pair of secondary side terminals 12c and 12d. One terminal 11c and 12c of each of the power conversion circuits 11 and 12 is connected to the positive electrode of the power storage device. The other terminal 11d and 12d of each of the power conversion circuits 11 and 12 is connected to the negative electrode of the power storage device. In this way, the secondary sides of the power conversion circuits 11 and 12 are connected in parallel to each other and to the power storage device.

When the power conversion circuits 11 and 12 output DC power to the secondary side, the power conversion device 10 further includes, for example, charge storage elements 23 and 24. The charge storage elements 23 and 24 are provided on the secondary side of each of the power conversion circuits 11 and 12. The charge storage element 23 is provided between a pair of secondary side terminals 11c and 11d of the power conversion circuit 11. The charge storage element 24 is provided between a pair of secondary side terminals 12c and 12d of the power conversion circuit 12. As a result, the charge storage elements 23 and 24 stabilize the DC voltage supplied to the secondary side of the power conversion circuits 11 and 12, for example. The charge storage elements 23 and 24 suppress, for example, noise superimposed on the DC voltage supplied to the secondary side of the power conversion circuits 11 and 12.

However, the power conversion device 10 is not limited to those used in railway vehicle power feeding systems. Furthermore, the power supplied to the secondary side is not limited to DC power, and may be AC power, etc. The power supplied to the secondary side may be any power corresponding to the secondary side. The power conversion circuits 11 and 12 do not necessarily have to have the function of supplying power from the secondary side to the primary side. The configuration of the power conversion circuits 11 and 12 may be any configuration that can at least convert the DC power on the primary side supplied from the DC power source 2 into another power corresponding to the secondary side and supply the converted power to the secondary side.

The control unit 30 controls the operation of each of the multiple power conversion circuits 11 and 12. The control unit 30 controls the operation of each of the multiple power conversion circuits 11 and 12, and detects a short circuit failure on the primary side of the multiple power conversion circuits 11 and 12 when the multiple power conversion circuits 11 and 12 are supplying power from the primary side to the secondary side. The control unit 30 detects, for example, a short circuit failure of the charge storage elements 21 and 22 as a short circuit failure on the primary side of the power conversion circuits 11 and 12. However, the short circuit failure on the primary side of the power conversion circuits 11 and 12 is not limited to a short circuit failure of the charge storage elements 21 and 22, but may be a short circuit failure caused by an internal circuit such as a switching element provided in the power conversion circuits 11 and 12. The short circuit failure on the primary side of the power conversion circuits 11 and 12 may be, for example, a short circuit failure caused by a conductive foreign object mixed between the terminals 11a and 11b and between the terminals 12a and 12b on the primary side.

The control unit 30 detects a short circuit fault on the primary side of the power conversion circuits 11 and 12, for example, by detecting the voltage between the terminals 11a and 11b on the primary side and the voltage between the terminals 12a and 12b using a voltage detector (not shown). The control unit 30 detects that the primary side of the power conversion circuit 11 has a short circuit fault when the voltage between the terminals 11a and 11b becomes equal to or lower than a predetermined value, and detects that the primary side of the power conversion circuit 12 has a short circuit fault when the voltage between the terminals 12a and 12b becomes equal to or lower than a predetermined value. However, the method of detecting a short circuit fault on the primary side of the power conversion circuits 11 and 12 by the control unit 30 is not limited to the above. The control unit 30 may detect a short circuit fault on the primary side of the power conversion circuits 11 and 12, for example, by receiving a detection signal for a short circuit fault on the primary side of the power conversion circuits 11 and 12 from a higher-level controller or the like. The method for detecting a short circuit fault on the primary side of the power conversion circuits 11 and 12 may be any method that allows the control unit 30 to appropriately detect a short circuit fault on the primary side of the power conversion circuits 11 and 12.

When the control unit 30 detects a short-circuit fault on the primary side of any of the multiple power conversion circuits 11, 12 while the multiple power conversion circuits 11, 12 are supplying power from the primary side to the secondary side, the control unit 30 stops the operation of the power conversion circuit among the multiple power conversion circuits 11, 12 in which the short-circuit fault on the primary side has been detected in response to the detection of the short-circuit fault. For example, the control unit 30 immediately stops the operation of the power conversion circuit in which the short-circuit fault on the primary side has been detected in response to the detection of the short-circuit fault.

The control unit 30 stops the operation of the power conversion circuit by, for example, turning off multiple switching elements of the power conversion circuit in which a short circuit fault on the primary side has been detected. The control unit 30 stops the operation of the power conversion circuit by performing so-called gate blocking. However, the method of stopping the operation of the power conversion circuit is not limited to the above, and any method that can appropriately stop the operation of the power conversion circuit may be used.

On the other hand, when the control unit 30 detects a short-circuit fault on the primary side of any of the multiple power conversion circuits 11, 12 while the control unit 30 is causing the multiple power conversion circuits 11, 12 to supply power from the primary side to the secondary side, the control unit 30 causes the power conversion circuits among the multiple power conversion circuits 11, 12 that have not detected a short-circuit fault on the primary side to perform the operation that occurs when a fault is detected, and stops the operation after the operation that occurs when the fault is detected is completed.

For example, suppose that a short circuit occurs in the primary side of the power conversion circuit 11 (e.g., the charge storage element 21) when multiple power conversion circuits 11, 12 are supplying power from the primary side to the secondary side. In this case, the control unit 30 stops the operation of the power conversion circuit 11 in response to detection of a short circuit failure on the primary side of the power conversion circuit 11, and causes the power conversion circuit 12 to perform the operation performed when the failure was detected. Then, the control unit 30 stops the operation of the power conversion circuit 12 after the operation performed when the failure was detected is completed.

When the power conversion circuits 11 and 12 are supplying power from the primary side to the secondary side, if a short circuit occurs on the primary side of the power conversion circuit 11, and the operation of the power conversion circuits 11 and 12 is suddenly stopped, the voltage of the charge storage element 22 will rise, and there is a possibility that a healthy charge storage element 22 will also suffer an extensive failure.

When the power conversion circuits 11 and 12 are supplying power from the primary side to the secondary side, the charge storage elements 21 and 22 share the DC voltage of the DC power supply 2. In this state, if a short circuit occurs on the primary side of the power conversion circuit 11, the DC voltage of the charge storage element 21 is also applied to the charge storage element 22. In other words, in this example, if a short circuit occurs on the primary side of the power conversion circuit 11, the DC voltage applied to the charge storage element 22 becomes double (the DC voltage of the DC power supply 2).

Therefore, it is conceivable to set the voltage tolerance of the charge storage elements so that the charge storage elements provided in the remaining power conversion circuits of the power conversion circuits 11 and 12 can bear the DC voltage of the DC power source 2 even when a short circuit occurs on the primary side of any one of the power conversion circuits 11 and 12. In this example, the voltage tolerance of the charge storage elements 21 and 22 is set to be equal to or greater than the DC voltage of the DC power source 2. For example, when the number of the charge storage elements (the number of power conversion circuits connected in series) is four, the voltage tolerance of the charge storage elements is set to be equal to or greater than one-third of the DC voltage of the DC power source 2 so that the charge storage elements provided in the remaining three power conversion circuits can bear the DC voltage of the DC power source 2 even when a short circuit occurs on the primary side of one power conversion circuit. That is, when the voltage tolerance of each of the charge storage elements is Vc, the DC voltage of the DC power source 2 is Ve, and the number of the charge storage elements is n, the voltage tolerance Vc of each of the charge storage elements is set to satisfy the following formula.
Vc≧Ve/(n-1)

However, when the power conversion circuits 11, 12 are supplying power from the primary side to the secondary side, if a short circuit occurs on the primary side of one of the multiple power conversion circuits 11, 12 and the operation of the power conversion circuits 11, 12 is suddenly stopped, even if the voltage tolerance of each of the multiple charge storage elements is set as described above, the voltage of the remaining charge storage elements may become higher than the set voltage tolerance, and the remaining healthy charge storage elements may also suffer an extended failure.

After careful consideration, the inventors of the present application found that the voltage rise of the multiple charge storage elements is due to the energy stored in the inductance component on the primary side circuit of the power conversion circuits 11 and 12. If the operation of the power conversion circuits 11 and 12 is suddenly stopped in a state in which energy is stored in the inductance component on the primary side circuit of the power conversion circuits 11 and 12, the energy stored in the inductance component may flow into the remaining healthy charge storage elements, and the DC voltage of the remaining healthy charge storage elements may rise above the voltage tolerance set as described above. In this example, when the charge storage element 21 causes a short circuit failure, the DC voltage of the charge storage element 22 may become higher than the DC voltage of the DC power source 2. The inductance component may be, for example, a parasitic inductance component present on the wiring path connecting the primary side of the power conversion circuits 11 and 12 and the DC power source 2, or an inductance component of a DC reactor provided between the primary side of the power conversion circuits 11 and 12 and the DC power source 2.

For this reason, in the power conversion device 10 according to this embodiment, when the control unit 30 detects a short-circuit fault on the primary side of any of the multiple power conversion circuits 11, 12 while the multiple power conversion circuits 11, 12 are supplying power from the primary side to the secondary side, the control unit 30 causes the power conversion circuits among the multiple power conversion circuits 11, 12 that have not detected a short-circuit fault on the primary side to perform the operation that occurs when a fault is detected, and stops the operation after the operation that occurs when the fault is detected is completed.

In other words, when a short circuit occurs on the primary side of any of the multiple power conversion circuits 11, 12, the control unit 30 provides an escape route for the energy stored in the inductance components on the primary side circuit by continuing to operate healthy charge storage elements and power conversion circuits. Then, when the energy stored in the inductance components on the primary side circuit has sufficiently decreased, the operation of all power conversion circuits is stopped.

This allows the energy stored in the inductance component on the primary circuit to flow to the secondary side, suppressing the rise in voltage of healthy charge storage elements. Therefore, it is possible to suppress widespread failure of healthy charge storage elements. In the power conversion device 10, there is no need to increase the capacity of the multiple charge storage elements 21, 22 or to provide an overvoltage protection circuit that suppresses overvoltage of the multiple charge storage elements 21, 22, and widespread failure of healthy charge storage elements can be suppressed with a simpler configuration.

In the power conversion device 10, the voltage tolerance of the multiple charge storage elements 21, 22 is set so that even if a short circuit occurs on the primary side of any one of the multiple power conversion circuits 11, 12, the charge storage elements provided in the remaining power conversion circuits of the multiple power conversion circuits 11, 12 can bear the DC voltage of the DC power source 2. This makes it possible to appropriately suppress the expansion of failures in the remaining charge storage elements due to a voltage rise borne by the charge storage element provided in the power conversion circuit whose primary side has a short circuit failure.

More specifically, the voltage withstand capability here refers to the voltage characteristic of the multiple charge storage elements that allows healthy, unfaulted charge storage elements to bear the DC voltage of the DC power source 2 during the relatively short time from when a short circuit fault occurs on the primary side of one of the multiple power conversion circuits 11, 12 until the fault detection operation is performed and the operation of all power conversion circuits 11, 12 is stopped. The voltage withstand capability may be, for example, the rated voltage of the multiple charge storage elements. However, the multiple charge storage elements do not necessarily need to be able to steadily bear the voltage rise of a short circuit faulted charge storage element, but only need to be able to bear the voltage rise during at least the relatively short time mentioned above.

The control unit 30 detects the magnitude of the current flowing through the primary circuit of the power conversion circuits 11 and 12, for example, by using a current detector (not shown), and executes an operation to gradually reduce the magnitude of the current flowing through the primary circuit as an operation to detect a fault. This gradually reduces the energy stored in the inductance component on the primary circuit, and appropriately suppresses the voltage rise of the charge storage element caused by the energy stored in the inductance component. Then, the control unit 30 ends the operation to detect a fault when, for example, the magnitude of the current flowing through the primary circuit falls below a predetermined value, and stops the operation of the healthy power conversion circuit. The control unit 30 ends the operation to detect a fault when, for example, the magnitude of the current flowing through the primary circuit becomes substantially zero.

However, the operation when a fault is detected is not limited to the above. The control unit 30 may, for example, detect the magnitude of the voltage of the charge storage element using a voltage detector (not shown) and execute an operation of gradually reducing the magnitude of the voltage of the charge storage element as the operation when a fault is detected. In this case, the control unit 30 may, for example, terminate the operation when a fault is detected when the magnitude of the voltage of the charge storage element falls below a predetermined value, and stop the operation of a healthy power conversion circuit.

For example, if the amount of energy stored in the inductance component on the primary circuit can be predicted, it is not necessary to detect the amount of current flowing through the primary circuit or the voltage of the charge storage element. For example, a predetermined operation that gradually reduces the amount of predicted energy without detecting the current or voltage may be executed as the operation at the time of fault detection. The operation at the time of fault detection is not limited to the above, and may be any operation that flows the energy stored in the inductance component on the primary circuit to the secondary side and appropriately suppresses the rise in voltage of healthy charge storage elements.

In addition, in the above embodiment, the secondary sides of the power conversion circuits 11 and 12 are connected in parallel. The configuration of the secondary sides of the power conversion circuits 11 and 12 is not limited to parallel connection, and may be any configuration that allows the energy stored in the inductance component on the primary side circuit to flow to the secondary side.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

2: DC power supply; 10: power conversion device; 11, 12: power conversion circuit; 21 to 24: charge storage element; 30: control unit

Claims (3)

A plurality of power conversion circuits having primary sides connected in series;
A plurality of charge storage elements provided on a primary side of each of the plurality of power conversion circuits;
A control unit that controls the operation of each of the plurality of power conversion circuits;
Equipped with
the primary sides of the plurality of power conversion circuits are connected in series and connected to a DC power source at both ends of the series connection;
The plurality of power conversion circuits convert the DC power on the primary side supplied from the DC power source into another power corresponding to a secondary side, and supply the converted power to the secondary side;
The control unit controls the operation of each of the multiple power conversion circuits, and detects a short-circuit fault on the primary side of the multiple power conversion circuits while causing the multiple power conversion circuits to supply power from the primary side to the secondary side. When a short-circuit fault on the primary side of any of the multiple power conversion circuits is detected, the control unit stops operation of the power conversion circuit among the multiple power conversion circuits in which the primary side short-circuit fault was detected, and for the power conversion circuits in which the primary side short-circuit fault was not detected, performs an operation of gradually reducing the magnitude of the current flowing in the primary side circuit based on the magnitude of the current flowing in the primary side circuit of the multiple power conversion circuits that was detected, and terminates the operation in response to the magnitude of the current flowing in the primary side circuit becoming equal to or less than a predetermined value . A plurality of power conversion circuits having primary sides connected in series;
A plurality of charge storage elements provided on a primary side of each of the plurality of power conversion circuits;
A control unit that controls the operation of each of the plurality of power conversion circuits;
Equipped with
the primary sides of the plurality of power conversion circuits are connected in series and connected to a DC power source at both ends of the series connection;
The plurality of power conversion circuits convert the DC power on the primary side supplied from the DC power source into another power corresponding to a secondary side, and supply the converted power to the secondary side;
The control unit controls the operation of each of the multiple power conversion circuits, and detects a short-circuit fault on the primary side of the multiple power conversion circuits while causing the multiple power conversion circuits to supply power from the primary side to the secondary side.When a short-circuit fault on the primary side of any of the multiple power conversion circuits is detected, the control unit stops operation of the power conversion circuit among the multiple power conversion circuits in which a short-circuit fault on the primary side has been detected, and for the power conversion circuits in which a short-circuit fault on the primary side has not been detected, performs an operation of gradually reducing the magnitude of the voltage of the charge storage element based on the detected magnitude of the voltage of the charge storage element, and terminates the operation in response to the magnitude of the voltage of the charge storage element becoming equal to or lower than a predetermined value. 3. The power conversion device according to claim 1, wherein the voltage withstand capability of the plurality of charge storage elements is set so that, even if a short-circuit fault occurs in the primary side of any one of the plurality of power conversion circuits, the charge storage elements provided in the remaining power conversion circuits of the plurality of power conversion circuits can bear the DC voltage of the DC power supply.

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