Power Conversion Device

Abstract

To provide a power conversion device that is capable of detecting the occurrence of failures of a plurality of switching elements having a predetermined resistance value.SOLUTION: A power conversion device comprises: a main circuit unit that performs conversion of electric power by switching a plurality of switch parts; and a control device that controls the conversion of electric power by the main circuit part. Each of the plurality of switch parts includes a plurality of switching elements connected in series. The control device identifies a switch part containing a switching element in which a failure with a predetermined resistance value has occurred, by detecting that a failure with the predetermined resistance value is occurring in any of the plurality of switching elements if a period representing that a forward voltage of any of a plurality of forward voltage signals is being applied overlaps with a period representing that a reverse voltage of any of a plurality of reverse voltage signals is being applied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a power conversion device. [Background technology]

[0002] A power conversion device is known that includes a main circuit unit that performs at least one of converting AC power to DC power and converting DC power to AC power, and a control device that controls the operation of the main circuit unit. The main circuit unit has multiple switch units in which multiple switching elements are connected in series, and performs power conversion by switching the multiple switch units. The control device transmits multiple control signals corresponding to the multiple switch units to the main circuit unit and controls the switching of the multiple switch units, thereby controlling the power conversion by the main circuit unit.

[0003] A plurality of switching elements may experience a short circuit failure due to various factors. In a main circuit section in which a plurality of switching elements are connected in series, even if a short circuit occurs in several of the switching elements included in the switch section, operation can be continued using the remaining switching elements.

[0004] On the other hand, multiple switching elements may fail without completely shorting out and while maintaining a certain resistance value. In this case, the control device or a higher-level device that controls the operation of the control device may determine that the main circuit is malfunctioning and may stop operation of the main circuit even if only one switching element is malfunctioning. For example, if the multiple switching elements are thyristors, the control device or higher-level device may determine that a thyristor commutation failure has occurred and may stop operation of the main circuit.

[0005] When a failure with a specified resistance value occurs in one of multiple switching elements, if the control device or higher-level device detects an abnormal operation of the main circuit section and stops the operation of the main circuit section, it may take time to identify the cause of the operation stoppage, and recovery may take time.

[0006] For this reason, in a power conversion device that has multiple switch sections in which multiple switching elements are connected in series and converts power by switching the multiple switch sections, it is desirable to be able to detect the occurrence of a fault in the multiple switching elements with a specified resistance value. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2018-137878 Summary of the Invention [Problem to be solved by the invention]

[0008] The embodiment provides a power conversion device that has multiple switch sections in which multiple switching elements are connected in series, converts power by switching the multiple switch sections, and can detect the occurrence of a fault in the multiple switching elements with a predetermined resistance value. [Means for solving the problem]

[0009] According to this embodiment, Each has multiple switching elements connected in series a main circuit unit having a plurality of switch units and performing at least one of conversion from AC power to DC power and conversion from DC power to AC power by switching the plurality of switch units; and a control device that controls the power conversion by the main circuit unit, A plurality of switches provided in the plurality of switches A forward voltage is applied to the switching element a signal indicating a period during which a forward voltage is not applied and a signal indicating a period during which a forward voltage is not applied; A forward voltage signal and a reverse voltage are applied. period of and a signal indicating a period during which a reverse voltage is not applied. Reverse voltage signal and Get , the acquired plurality of forward voltage signals and the acquired plurality of reverse voltage signals to the control device; The control device determines, by a logical OR operation of the plurality of forward voltage signals, a forward voltage logical OR signal including a signal indicating a period during which a forward voltage is applied to any of the plurality of switching elements and a signal indicating a period during which a forward voltage is not applied to any of the plurality of switching elements, and determines, by a logical OR operation of the plurality of reverse voltage signals, a reverse voltage logical OR signal including a signal indicating a period during which a reverse voltage is applied to any of the plurality of switching elements and a signal indicating a period during which a reverse voltage is not applied to any of the plurality of switching elements, and detects the switch unit in which the period during which a forward voltage is applied and the period during which a reverse voltage is applied overlap as the switch unit including the switching element having a predetermined resistance value in which a fault has occurred, based on the signal indicating the period during which the forward voltage is applied of the forward voltage logical OR signal and the signal indicating the period during which the reverse voltage is applied of the reverse voltage logical OR signal. A power converter is provided. [Effects of the Invention]

[0010] In this embodiment, a power conversion device is provided that has a plurality of switch sections in which a plurality of switching elements are connected in series, and that converts power by switching the plurality of switch sections and can detect the occurrence of a fault in a plurality of switching elements with a predetermined resistance value. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram schematically illustrating a power conversion device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram schematically illustrating a switch unit according to the first embodiment. [Figure 3] FIG. 2 is a block diagram schematically illustrating a part of a control device according to the first embodiment. [Figure 4] 3 is a waveform diagram schematically illustrating an example of the operation of the power conversion device according to the first embodiment. FIG. [Figure 5] 3 is a waveform diagram schematically illustrating an example of the operation of the power conversion device according to the first embodiment. FIG. [Figure 6] FIG. 10 is a block diagram schematically illustrating a part of a control device according to a second embodiment. [Figure 7] FIG. 10 is a block diagram schematically illustrating a power conversion device according to a third embodiment. [Figure 8] FIG. 10 is a block diagram schematically illustrating a control device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention 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 size ratio between parts, etc. are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In the present specification and the drawings, 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.

[0013] (First embodiment) FIG. 1 is a block diagram schematically illustrating a power conversion device according to a first embodiment. As shown in FIG. 1, the power conversion device 10 includes a main circuit unit 12 and a control device 14.

[0014] The main circuit unit 12 has a plurality of switch units 20. The main circuit unit 12 converts power by switching the plurality of switch units 20. The plurality of switch units 20 are, for example, bridge-connected. In this example, the main circuit unit 12 has two bridge circuits each consisting of six switch units 20 connected in a three-phase bridge configuration, and is a 12-phase converter in which the two bridge circuits are connected in series. The switch unit 20 is, for example, a part that constitutes one arm of the bridge circuit. The main circuit unit 12 converts AC power to DC power by, for example, switching the plurality of switch units 20.

[0015] However, the configuration of the main circuit unit 12 is not limited to a 12-phase converter, and may be a three-phase converter consisting of six switch units 20 connected in a three-phase bridge, or a single-phase converter consisting of four switch units 20 connected in a single-phase bridge. The main circuit unit 12 may be, for example, a multilevel converter such as a three-level converter. The main circuit unit 12 may be configured in any manner that allows power conversion by switching multiple switch units 20. Furthermore, the power conversion by the main circuit unit 12 is not limited to conversion from AC power to DC power, and may also be conversion from DC power to AC power, or conversion from AC power to another AC power. The power conversion by the main circuit unit 12 may be any conversion that converts at least one of AC power to DC power and DC power to AC power.

[0016] FIG. 2 is a block diagram schematically illustrating a switch unit according to the first embodiment. 2, each of the multiple switch units 20 includes multiple switching elements 22, multiple snubber circuits 24, and multiple voltage detectors 26. The multiple switching elements 22 are connected in series. This allows the main circuit unit 12 to share the voltage applied across the switch unit 20 among the multiple switching elements 22. This prevents the multiple switching elements 22 from needing to withstand high voltages, and allows power conversion at a relatively high voltage.

[0017] The multiple switching elements 22 are, for example, thyristors. The multiple switch units 20 are, for example, thyristor valves. The multiple switching elements 22 have, for example, a pair of main terminals and a control terminal. The multiple switching elements 22 have an on state and an off state. The on state is a state in which current flows between the pair of main terminals. The off state is a state in which current flow between the pair of main terminals is blocked. Note that the off state is not limited to a state in which no current flows between the pair of main terminals, but may also be a state in which a weak current flows between the pair of main terminals within a range that does not affect the operation of the main circuit unit 12. The multiple switching elements 22 switch between the on state and the off state depending on the voltage between the pair of main terminals and the voltage of the control terminal.

[0018] However, the multiple switching elements 22 are not limited to thyristors, and may be other separately excited switching elements or self-excited switching elements such as GTO, MOSFET, IGBT, etc. The multiple switching elements 22 may be any switching elements that can switch between an on state and an off state according to the voltage between a pair of main terminals and the voltage at a control terminal.

[0019] Each of the plurality of snubber circuits 24 is connected in parallel with each of the plurality of switching elements 22. The snubber circuits 24 suppress a transient high voltage that occurs when the switching elements 22 are turned off.

[0020] The snubber circuit 24 includes, for example, a series connection of a resistor 24a and a capacitor 24b. The resistor 24a is provided between a pair of main terminals of the switching element 22. The capacitor 24b is provided between the resistor 24a and one of the main terminals of the switching element 22.

[0021] In this example, the snubber circuit 24 is a so-called RC snubber circuit. However, the configuration of the snubber circuit 24 is not limited to an RC snubber circuit, and may be any configuration that is connected in parallel to the switching element 22 and can suppress a transient high voltage that occurs when the switching element 22 is turned off.

[0022] Each of the plurality of voltage detectors 26 is provided for each of the plurality of switching elements 22. The plurality of voltage detectors 26 detects the voltage between a pair of main terminals of each of the plurality of switching elements 22.

[0023] Returning to Figure 1, the control device 14 controls the power conversion by the main circuit unit 12 by transmitting multiple control signals GP corresponding to each of the multiple switch units 20 to the main circuit unit 12 and controlling the switching of the multiple switch units 20.

[0024] The control device 14 communicates with the upper device 2. The upper device 2 is, for example, a higher-level controller that controls the operation of the power conversion device 10. The control device 14 generates a plurality of control signals GP based on instructions from the upper device 2 and transmits the generated control signals GP to the main circuit unit 12.

[0025] However, the control device 14 does not necessarily have to communicate with the higher-level device 2. The control device 14 may be configured to control the operation of the main circuit unit 12 based on, for example, preset information. The control device 14 may be configured to have, for example, an operation unit for receiving input of operation instructions from an administrator of the power conversion device 10, and to control the operation of the main circuit unit 12 based on information input via the operation unit.

[0026] The main circuit unit 12 converts power by driving the switching of the multiple switch units 20 based on multiple control signals GP received from the control device 14. The main circuit unit 12 also acquires multiple forward voltage signals FV and multiple reverse voltage signals RV of the multiple switching elements 22 for each of the multiple switch units 20.

[0027] The forward voltage signal FV is a signal that indicates that a forward voltage is being applied to the switching element 22. The reverse voltage signal RV is a signal that indicates that a reverse voltage is being applied to the switching element 22. More specifically, the forward voltage signal FV is a signal that indicates that a forward voltage is being applied across a pair of main terminals of the switching element 22, and the reverse voltage signal RV is a signal that indicates that a reverse voltage is being applied across a pair of main terminals of the switching element 22.

[0028] The main circuit unit 12 detects the voltage across the switching element 22 using a voltage detector 26, for example, to obtain the forward voltage signal FV and the reverse voltage signal RV.

[0029] The main circuit unit 12, for example, acquires a plurality of forward voltage signals FV corresponding to each of the plurality of switching elements 22 of the plurality of switch units 20. Meanwhile, the main circuit unit 12, for example, acquires a predetermined number of reverse voltage signals RV corresponding to a predetermined number of representative switching elements 22 from among the plurality of switching elements 22 for each of the plurality of switch units 20.

[0030] However, the main circuit unit 12 may obtain a predetermined number of forward voltage signals FV corresponding to a predetermined number of representative switching elements 22 of the multiple switching elements 22 for each of the multiple switch units 20. The main circuit unit 12 may obtain a plurality of reverse voltage signals RV corresponding to the multiple switching elements 22 of the multiple switch units 20, respectively.

[0031] The number of forward voltage signals FV acquired by the main circuit unit 12 may be the same as or different from the number of reverse voltage signals RV acquired. In one switch unit 20, the switching element 22 that acquires the forward voltage signals FV may be the same as or different from the switching element 22 that acquires the reverse voltage signals RV. The number of forward voltage signals FV and the number of reverse voltage signals RV acquired by the main circuit unit 12 may be any number.

[0032] The main circuit unit 12 transmits the acquired forward voltage signals FV and reverse voltage signals RV to the control device 14.

[0033] The control device 14 receives the plurality of forward voltage signals FV and the plurality of reverse voltage signals RV of the plurality of switch units 20 from the main circuit unit 12. The control device 14 transmits the received plurality of forward voltage signals FV and the plurality of reverse voltage signals RV to the higher-level device 2. The control device 14 controls the operation of the main circuit unit 12 by generating a plurality of control signals GP based on, for example, a command from the higher-level device 2, the received plurality of forward voltage signals FV, ​​and the received plurality of reverse voltage signals RV.

[0034] Furthermore, the control device 14 and the higher-level device 2 detect an abnormality in the main circuit unit 12 based on the received multiple forward voltage signals FV and multiple reverse voltage signals RV. When an abnormality in the main circuit unit 12 is detected, the control device 14 and the higher-level device 2 stop the operation of the main circuit unit 12.

[0035] The control device 14 acquires multiple forward voltage signals FV corresponding to all of the switching elements 22 included in the multiple switch units 20. This allows for appropriate detection of an abnormality in the main circuit unit 12. The control device 14 acquires a predetermined number of reverse voltage signals RV corresponding to a predetermined number of representative switching elements 22 among the switching elements 22. This improves the accuracy of detecting an abnormality in the main circuit unit 12 while minimizing the complexity of the configuration of the main circuit unit 12 and the control device 14 and the increase in the number of components, such as the voltage detector 26 for acquiring the reverse voltage signals RV and communication equipment for communicating the reverse voltage signals RV. For example, this prevents the main circuit unit 12 and the control device 14 from becoming larger and the manufacturing costs from increasing. However, as with the main circuit unit 12, the number of forward voltage signals FV and the number of reverse voltage signals RV acquired by the control device 14 may be any number.

[0036] FIG. 3 is a block diagram schematically illustrating a part of the control device according to the first embodiment. 3, the control device 14 has OR circuits 30 and 32. In other words, the OR circuits 30 and 32 are logical sum circuits. Although the illustration is simplified in FIG. 3, the control device 14 has, for example, a plurality of OR circuits 30 corresponding to each of the plurality of switch units 20 in the main circuit unit 12, and a plurality of OR circuits 32 corresponding to each of the plurality of switch units 20 in the main circuit unit 12.

[0037] The OR circuit 30 calculates the logical sum of the multiple forward voltage signals FV of a corresponding switch section 20 and outputs a logical sum signal FVOR of the forward voltages. The control device 14 uses the multiple OR circuits 30 to calculate multiple logical sum signals FVOR corresponding to the multiple switch sections 20, respectively.

[0038] The OR circuit 32 calculates the logical sum of the reverse voltage signals RV of a corresponding switch section 20 and outputs a logical sum signal RVOR of the reverse voltages. The control device 14 uses the multiple OR circuits 32 to calculate the logical sum signals RVOR corresponding to the multiple switch sections 20, respectively.

[0039] 3 shows an example in which, for example, when 40 switching elements 22 are connected in series in one switch section 20, the logical sum of four reverse voltage signals RV corresponding to the 10th, 20th, 30th, and 40th switching elements 22 is calculated. However, the number of reverse voltage signals RV to be acquired is not limited to four and may be any number. The switching elements 22 from which the reverse voltage signal RV is acquired are not limited to the 10th, 20th, 30th, and 40th switching elements 22 and may be any switching element 22.

[0040] The control device 14 generates a plurality of control signals GP based on, for example, a command from the higher-level device 2, a logical sum signal FVOR of forward voltages, and a logical sum signal RVOR of reverse voltages, thereby making it possible to appropriately control the operation of the main circuit unit 12 in accordance with the state of the main circuit unit 12 (the state of the voltage applied across each switching element 22).

[0041] FIG. 4 is a waveform diagram schematically illustrating an example of the operation of the power conversion device according to the first embodiment. 4 schematically shows an example of the AC voltage applied across one switch section 20, the AC voltage vt1 applied across the first switching element 22, the forward voltage signal FV1 of the first switching element 22, the AC voltages vt2 to vt(n) applied across the second to n-th switching elements 22, the forward voltage signals FV2 to FV(n) of the second to n-th switching elements 22, the logical sum signal FVOR of the forward voltages, and the logical sum signal RVOR of the reverse voltages. Also, FIG. 4 schematically shows an example of each signal when each of the multiple switching elements 22 included in one switch section 20 is normal.

[0042] 4, the forward voltage signal FV (FV1 to FV(n)) is a pulse signal that is, for example, Hi (high voltage state) when a forward voltage is applied to the switching element 22 and Lo (low voltage state) when no forward voltage is applied to the switching element 22. In other words, the forward voltage signal FV is a digital signal that is, for example, "1" when a forward voltage is applied to the switching element 22 and "0" when no forward voltage is applied to the switching element 22.

[0043] In one switch section 20, the multiple switching elements 22 are connected in series. Therefore, when each of the multiple switching elements 22 is normal, as shown in Fig. 4, an AC voltage substantially synchronized with the AC voltage applied across the switch section 20 is applied to each of the multiple switching elements 22, and the multiple forward voltage signals FV1 to FV(n) are substantially the same signal.

[0044] The logical sum signal FVOR obtained by calculating the logical sum of the multiple forward voltage signals FV1 to FV(n) is "0" when all of the multiple forward voltage signals FV1 to FV(n) are "0," and is "1" when any of the multiple forward voltage signals FV1 to FV(n) is "1." In other words, the logical sum signal FVOR of the forward voltages is "1" when a forward voltage is applied to any of the multiple switching elements 22, and is "0" when a forward voltage is not applied to any of the multiple switching elements 22.

[0045] As described above, the forward voltage signals FV1 to FV(n) are substantially the same signal when each of the switching elements 22 is normal. Therefore, when each of the switching elements 22 is normal, the logical sum signal FVOR of the forward voltages is also substantially the same signal as the forward voltage signals FV1 to FV(n).

[0046] The reverse voltage signal RV is a pulse-like signal that is, for example, Hi when a reverse voltage is applied to the switching element 22 and Lo when no reverse voltage is applied to the switching element 22. The reverse voltage signal RV is, for example, a signal obtained by inverting the forward voltage signal FV of the same switching element 22. Therefore, when each of the multiple switching elements 22 is normal, the multiple reverse voltage signals RV of one switch section 20 are also substantially the same signal. The reverse voltage logical sum signal RVOR is also substantially the same signal as the multiple reverse voltage signals RV. When each of the multiple switching elements 22 is normal, the reverse voltage logical sum signal RVOR is, for example, a signal obtained by inverting the forward voltage logical sum signal FVOR.

[0047] In this way, when the multiple switching elements 22 are normal, for example, the reverse voltage logical sum signal RVOR is a signal obtained by inverting the forward voltage logical sum signal FVOR, and the period during which the reverse voltage logical sum signal RVOR is "1" does not overlap with the period during which the forward voltage logical sum signal FVOR is "1." In other words, the period during which the reverse voltage logical sum signal RVOR indicates that a reverse voltage is being applied does not overlap with the period during which the forward voltage logical sum signal FVOR indicates that a forward voltage is being applied.

[0048] The forward voltage signal FV and the reverse voltage signal RV are not limited to those described above. The forward voltage signal FV may be any signal having a period indicating that a forward voltage is being applied to the corresponding switching element 22 and a period indicating that a forward voltage is not being applied to the corresponding switching element 22. The reverse voltage signal RV may be any signal having a period indicating that a reverse voltage is being applied to the corresponding switching element 22 and a period indicating that a reverse voltage is not being applied to the corresponding switching element 22.

[0049] Furthermore, the logical sum signal FVOR of the forward voltages may be any signal having a period indicating that a forward voltage is being applied to any of the multiple switching elements 22 and a period indicating that a forward voltage is not being applied to any of the multiple switching elements 22. The logical sum signal RVOR of the reverse voltages may be any signal having a period indicating that a reverse voltage is being applied to any of the multiple switching elements 22 and a period indicating that a reverse voltage is not being applied to any of the multiple switching elements 22.

[0050] FIG. 5 is a waveform diagram schematically illustrating an example of the operation of the power conversion device according to the first embodiment. FIG. 5 shows a schematic example of the same signals as those shown in FIG. 3 when a fault with a predetermined resistance value occurs in the first switching element 22 among the multiple switching elements 22 included in one switch section 20.

[0051] If the switching element 22 has a short-circuit failure, the voltage between the pair of main terminals of the switching element 22 becomes substantially zero, and therefore the forward voltage signal FV always indicates a period in which no forward voltage is applied to the switching element 22. Similarly, if the switching element 22 has a short-circuit failure, the reverse voltage signal RV always indicates a period in which no reverse voltage is applied to the switching element 22.

[0052] Therefore, when the forward voltage signal FV and the reverse voltage signal RV do not change and a period indicating that a forward voltage and a reverse voltage are not being applied continues, the control device 14 and the higher-level device 2 detect that a short-circuit fault has occurred in the switching element 22. In other words, the control device 14 and the higher-level device 2 detect that a short-circuit fault has occurred in the switching element 22 when a period indicating that a forward voltage and a reverse voltage are not being applied continues even during a period that should indicate that a forward voltage and a reverse voltage are being applied.

[0053] In a switch unit 20 in which multiple switching elements 22 are connected in series, even if some of the multiple switching elements 22 connected in series suffer a short-circuit failure, operation can continue using the remaining switching elements 22. The control device 14 and the higher-level device 2 count the number of switching elements 22 that have suffered a short-circuit failure, and if the number of switching elements 22 that have suffered a short-circuit failure is less than a predetermined number, they continue operation of the main circuit unit 12, but if the number of switching elements 22 that have suffered a short-circuit failure exceeds the predetermined number, they stop operation of the main circuit unit 12. This makes it possible, for example, to increase the stability of operation of the main circuit unit 12 while suppressing widespread failure of the remaining healthy switching elements 22.

[0054] 4 and 5, for ease of explanation, examples of voltage waveforms and signals when the multiple switching elements 22 are in the OFF state are shown in schematic form. When the main circuit unit 12 is operating, the voltages (AC voltages vt1 to vt(n)) across the switching elements 22 become substantially zero when the switching elements 22 are switched to the ON state. Therefore, when the switching elements 22 are switched from the OFF state to the ON state, the forward voltage signal FV switches from a period indicating that a forward voltage is being applied to a period indicating that a forward voltage is not being applied.

[0055] On the other hand, when the switching element 22 is in a fault state with a predetermined resistance value, a period in which a forward voltage is applied to the switching element 22 and a period in which a reverse voltage is applied are generated depending on the resistance value of the switching element 22 and the AC voltage applied to both ends of the switching element 22.

[0056] In this case, as shown in FIG. 5 , the AC voltage applied across the faulty switching element 22 having a predetermined resistance value is an AC voltage that is out of phase with the AC voltage applied across the switch unit 20 and the AC voltage applied across the other normal switching elements 22. This is due to the influence of the snubber circuit 24 connected in parallel with the switching element 22. For example, if the snubber circuit 24 includes a capacitor 24b, the AC voltage applied across the faulty switching element 22 having a predetermined resistance value is an AC voltage that leads in phase with the AC voltage applied across the switch unit 20 and the AC voltage applied across the other normal switching elements 22. For example, FIG. 5 shows an example in which the phase of the AC voltage applied across the faulty switching element 22 having a predetermined resistance value leads the phase of the AC voltage applied across the switch unit 20 by 80°.

[0057] For this reason, the forward voltage signal FV of the faulty switching element 22 having a predetermined resistance value is a signal different from the forward voltage signals FV of the other normal switching elements 22. The period indicating that the forward voltage of the forward voltage signal FV of the faulty switching element 22 having a predetermined resistance value is being applied differs in timing from the period indicating that the forward voltage of the forward voltage signal FV of the other normal switching elements 22 is being applied.

[0058] Therefore, the logical sum signal FVOR obtained by calculating the logical sum of the multiple forward voltage signals FV1 to FV(n) changes by the amount of the timing shift of the forward voltage signal FV of the faulty switching element 22 having a predetermined resistance value. The logical sum signal FVOR has a longer period indicating that a forward voltage is being applied to any of the multiple switching elements 22 by the amount of the timing shift, compared to when each of the multiple switching elements 22 is normal.

[0059] Furthermore, for example, if a fault with a predetermined resistance value occurs in the switching element 22 that acquires the reverse voltage signal RV, the period during which the reverse voltage logical sum signal RVOR indicates that a reverse voltage is being applied to any of the multiple switching elements 22 will be longer by the amount of the timing shift, just as with the forward voltage logical sum signal FVOR.

[0060] In this way, when each of the multiple switching elements 22 is normal, the period indicating that the reverse voltage of the logical OR signal RVOR of the reverse voltages is being applied does not overlap with the period indicating that the forward voltage of the logical OR signal FVOR of the forward voltages is being applied. When a failure with a predetermined resistance value occurs in any of the multiple switching elements 22, there occurs a period in which the period indicating that the reverse voltage of the logical OR signal RVOR of the reverse voltages is being applied overlaps with the period indicating that the forward voltage of the logical OR signal FVOR of the forward voltages is being applied.

[0061] Based on the plurality of forward voltage signals FV and the plurality of reverse voltage signals RV, the control device 14 detects the occurrence of a fault with a predetermined resistance value in the plurality of switching elements 22. When the period in which each of the plurality of forward voltage signals FV indicates that a forward voltage is being applied does not overlap with the period in which each of the plurality of reverse voltage signals RV indicates that a reverse voltage is being applied, the control device 14 detects that no fault with a predetermined resistance value has occurred in any of the plurality of switching elements 22.

[0062] When a period indicating that a forward voltage of any of the plurality of forward voltage signals FV is being applied overlaps with a period indicating that a reverse voltage of any of the plurality of reverse voltage signals RV is being applied, the control device 14 detects that a fault with a predetermined resistance value has occurred in any of the plurality of switching elements 22. By detecting that a fault with a predetermined resistance value has occurred in any of the plurality of switching elements 22, the control device 14 identifies the switch section 20 including the switching element 22 with the predetermined resistance value in which the fault has occurred.

[0063] In this example, the control device 14 calculates a logical sum signal FVOR by calculating the logical sum of a plurality of forward voltage signals FV, ​​and a logical sum signal RVOR by calculating the logical sum of a plurality of reverse voltage signals RV.

[0064] The control device 14 determines that the periods representing the application of the forward voltages of the forward voltage logical sum signal FVOR do not overlap with the periods representing the application of the reverse voltages of the reverse voltage logical sum signal RVOR, when the periods representing the application of the forward voltages of the forward voltage logical sum signal FVOR do not overlap with the periods representing the application of the reverse voltages of the reverse voltage logical sum signal RVOR. In other words, the control device 14 detects that a fault having a predetermined resistance value has not occurred in any of the switching elements 22, when the periods representing the application of the forward voltages of the forward voltage logical sum signal FVOR do not overlap with the periods representing the application of the reverse voltages of the reverse voltage logical sum signal RVOR.

[0065] Then, when a period indicating that a forward voltage of the forward voltage logical sum signal FVOR is being applied overlaps with a period indicating that a reverse voltage of the reverse voltage logical sum signal RVOR is being applied, the control device 14 determines that a period indicating that a forward voltage of any of the plurality of forward voltage signals FV is being applied overlaps with a period indicating that a reverse voltage of any of the plurality of reverse voltage signals RV is being applied. In other words, when a period indicating that a forward voltage of the forward voltage logical sum signal FVOR is being applied overlaps with a period indicating that a reverse voltage of the reverse voltage logical sum signal RVOR is being applied, the control device 14 detects that a fault with a predetermined resistance value has occurred in one of the plurality of switching elements 22.

[0066] In this way, the control device 14 detects the occurrence of a fault with a predetermined resistance value in the multiple switching elements 22, for example, based on the logical sum signal FVOR of the forward voltages and the logical sum signal RVOR of the reverse voltages. This reduces the calculation load on the control device 14 compared to, for example, comparing multiple forward voltage signals FV with multiple reverse voltage signals RV. A fault with a predetermined resistance value in the multiple switching elements 22 can be detected with a simpler configuration.

[0067] When the control device 14 detects that a fault with a predetermined resistance value has occurred in any of the switching elements 22, it stops the operation of the main circuit unit 12, for example, thereby preventing the expansion of the fault in the remaining healthy switching elements 22.

[0068] In addition, a fault with a predetermined resistance value of multiple switching elements 22 may be detected by the upper device 2 by transmitting multiple forward voltage signals FV and multiple reverse voltage signals RV to the upper device 2.

[0069] As described above, according to this embodiment, it is possible to provide a power conversion device 10 that has a plurality of switch sections 20 in which a plurality of switching elements 22 are connected in series, converts power by switching the plurality of switch sections 20, and is capable of detecting the occurrence of a fault with a predetermined resistance value in the plurality of switching elements 22.

[0070] For example, when a fault with a predetermined resistance value occurs in any of the multiple switching elements 22, the forward voltage signal FV of the faulty switching element 22 enters a period indicating that a forward voltage is being applied at a timing different from normal, so the control device 14 or the higher-level device 2 may determine that this is an operational abnormality in the main circuit unit 12 (for example, a commutation failure of a thyristor element) and stop the operation of the main circuit unit 12. In this configuration, it may take time to identify the cause of the operational stop, which may result in a long recovery time.

[0071] In contrast, in the power conversion device 10 according to the present embodiment, the control device 14 detects that a fault with a predetermined resistance value has occurred in one of the plurality of switching elements 22, and identifies the switch unit 20 including the faulty switching element 22 with the predetermined resistance value. Therefore, in the power conversion device 10, for example, after stopping the operation of the main circuit unit 12, the plurality of switching elements 22 included in the identified switch unit 20 may be inspected, and the faulty switching element 22 may be identified and replaced. This facilitates the restoration of the main circuit unit 12 in the power conversion device 10 compared to, for example, a case in which all switching elements 22 included in the plurality of switch units 20 must be inspected. For example, the time required for restoration may be shortened.

[0072] (Second embodiment) FIG. 6 is a block diagram schematically illustrating a part of a control device according to the second embodiment. As shown in Fig. 6, the control device 14a in this example has a plurality of AND circuits 40, a plurality of NOT gates 42, a plurality of AND circuits 44, and an OR circuit 46. Note that components that are substantially the same in function and configuration as those in the first embodiment are given the same reference numerals, and detailed description thereof will be omitted. Also, Fig. 6 shows only a portion of the control device 14a that corresponds to one switch unit 20. The plurality of AND circuits 40, the plurality of NOT gates 42, the plurality of AND circuits 44, and the OR circuit 46 are provided, for example, for each of the plurality of switch units 20.

[0073] The multiple AND circuits 40, the multiple NOT gates 42, and the multiple AND circuits 44 are provided corresponding to the multiple switching elements 22 included in one switch section 20. In other words, the AND circuits 40 and the AND circuits 44 are logical product circuits.

[0074] The control device 14a inputs the forward voltage signals FV of the multiple switching elements 22 to multiple AND circuits 40, respectively, and inputs the reverse voltage logical sum signal RVOR to the multiple AND circuits 40. The reverse voltage logical sum signal RVOR can use the output of the OR circuit 32 described with reference to FIG. 3. The control device 14a further includes, for example, an OR circuit 32 (not shown). The reverse voltage logical sum signal RVOR can be the same as that described with reference to the first embodiment.

[0075] The AND circuit 40 calculates the logical product of the input forward voltage signal FV and the logical sum signal RVOR of one switching element 22. The control device 14a uses the multiple AND circuits 40 to calculate the logical product of each of the multiple forward voltage signals FV corresponding to each of the multiple switching elements 22 and the logical sum signal RVOR of the reverse voltage.

[0076] The output of the AND circuit 40 is "1" when the forward voltage signal FV and the logical sum signal RVOR are both "1", and is "0" otherwise. That is, the output of the AND circuit 40 is "1" during a period in which the forward voltage signal FV indicates that a forward voltage is being applied to the switching element 22 and during a period in which the logical sum signal RVOR indicates that a reverse voltage is being applied to any of the multiple switching elements 22, and is "0" otherwise.

[0077] As described above, when the switching element 22 is normal, the period of the forward voltage signal FV indicating that a forward voltage is being applied to the switching element 22 does not overlap with the period of the OR signal RVOR indicating that a reverse voltage is being applied. Therefore, it can be considered that the output of the AND circuit 40 becomes "1" when a fault with a predetermined resistance value occurs in the corresponding switching element 22.

[0078] When the output of the AND circuit 40 becomes "1", the control device 14a detects a failure of the corresponding switching element 22. The control device 14a counts the number of faulty switching elements 22 having a predetermined resistance value based on the outputs of the multiple AND circuits 40. When the number of faulty switching elements 22 having a predetermined resistance value in one switch section 20 is less than a predetermined number, the control device 14a continues the operation of the main circuit section 12. When the number of faulty switching elements 22 having a predetermined resistance value in one switch section 20 is equal to or greater than the predetermined number, the control device 14a stops the operation of the main circuit section 12.

[0079] In addition, the control device 14a may further include a latch circuit that, once the output of the AND circuit 40 becomes "1," fixes the output of the AND circuit 40 at "1" until the corresponding switching element 22 is inspected, for example.

[0080] The AND circuit 40 also inputs the result of the logical AND operation to a NOT gate 42. The NOT gate 42 inverts the result of the logical AND operation of the AND circuit 40 and inputs it to an AND circuit 44. The AND circuit 44 receives the output of the NOT gate 42 and also receives a forward voltage signal FV of one switching element 22. The AND circuit 44 performs a logical AND operation on the forward voltage signal FV and the output of the NOT gate 42, and inputs the result of the logical AND operation to an OR circuit 46.

[0081] The OR circuit 46 calculates the logical sum of the results of the logical products calculated by the multiple AND circuits 44, and outputs a logical sum signal FVOR of the forward voltage. The control device 14a calculates, for example, multiple logical sum signals FVOR corresponding to the multiple switch sections 20 using the multiple OR circuits 46.

[0082] When the switching element 22 is normal, the output of the AND circuit 40 is "0." Therefore, when the switching element 22 is normal, the output of the AND circuit 40 is inverted by the NOT gate 42, resulting in "1," which is input to one input terminal of the AND circuit 44. As a result, the output of the AND circuit 44 is determined according to the forward voltage signal FV input to the other input terminal of the AND circuit 44. When the switching element 22 is normal, the output of the AND circuit 44 is "0" when the forward voltage signal FV is "0," and is "1" when the forward voltage signal FV is "1."

[0083] On the other hand, if a fault with a predetermined resistance value occurs in a switching element 22, the output of the AND circuit 40 is inverted by the NOT gate 42 to "0," which is input to one input terminal of the AND circuit 44. Therefore, the output of the AND circuit 44 is "0" regardless of the state of the forward voltage signal FV. This makes it possible to exclude the forward voltage signal FV of the switching element 22 with a predetermined resistance value that has occurred from the calculation of the forward voltage logical sum signal FVOR. As a result, if the number of switching elements 22 with a predetermined resistance value that have occurred that have occurred in one switch section 20 is less than a predetermined number, the forward voltage signal FV of the failed switching element 22 can be excluded from the calculation of the forward voltage logical sum signal FVOR.

[0084] The control device 14a generates a plurality of control signals GP based on, for example, a command from the higher-level device 2, the logical sum signal FVOR of the forward voltages, and the logical sum signal RVOR of the reverse voltages. In this case, as described above, the logical sum signal FVOR of the forward voltages is calculated while excluding the forward voltage signal FV of the failed switching element 22, thereby making it possible to properly calculate the logical sum signal FVOR of the forward voltages. As a result, when the number of failed switching elements 22 having a predetermined resistance value in one switch unit 20 is less than a predetermined number, the control devices GP can be properly generated, thereby enabling the main circuit unit 12 to continue operating properly.

[0085] In this way, the control device 14a according to this embodiment identifies which of the multiple switching elements 22 has a fault with a predetermined resistance value by comparing the period representing the application of each forward voltage of the multiple forward voltage signals FV with the period representing the application of each reverse voltage of the multiple reverse voltage signals RV.

[0086] Therefore, in this embodiment, after stopping the operation of the main circuit unit 12, the switching element 22 in which the occurrence of the failure has been identified can be inspected and work such as replacing the failed switching element 22 can be performed. This makes it easier to restore the main circuit unit 12. For example, the time required for restoration can be further reduced.

[0087] The control device 14a identifies which of the multiple switching elements 22 has a fault with a predetermined resistance value by, for example, comparing the period indicating that each of the multiple forward voltage signals FV is being applied with the period indicating that the reverse voltage of the reverse voltage OR signal RVOR is being applied. This reduces the calculation load on the control device 14 compared to, for example, comparing each of the multiple forward voltage signals FV with each of the multiple reverse voltage signals RV.

[0088] In this example, a comparison is made between the period indicating that a forward voltage is being applied from each of the plurality of forward voltage signals FV and the period indicating that a reverse voltage is being applied from the reverse voltage OR signal RVOR by the plurality of AND circuits 40. The configuration for comparing the two is not limited to the above, and any configuration may be used that can appropriately identify a faulty switching element 22 having a predetermined resistance value.

[0089] Furthermore, when the number of faulty switching elements 22 having a predetermined resistance value in one switch section 20 is less than a predetermined number, the control device 14a continues operation of the main circuit section 12. This prevents unintended stoppage of operation of the main circuit section 12 due to a fault in a switching element 22, and further improves the stability of operation of the main circuit section 12.

[0090] (Third embodiment) FIG. 7 is a block diagram schematically illustrating a power conversion device according to the third embodiment. 7, in the power conversion device 10b, the main circuit unit 12b further includes a plurality of voltage detectors 50. The plurality of voltage detectors 50 are provided corresponding to the plurality of switch units 20, respectively. The plurality of voltage detectors 50 detect AC voltages applied across both ends of each of the plurality of switch units 20.

[0091] The main circuit unit 12b transmits a plurality of forward voltage signals FV and a plurality of reverse voltage signals RV to the control device 14b, and also transmits detection results of the plurality of voltage detectors 50 to the control device 14b. In this way, the main circuit unit 12b acquires the forward voltage signal FV indicating that a forward voltage is being applied to the switching element 22 for each of the plurality of switching elements 22, thereby acquiring the plurality of forward voltage signals FV and acquiring the AC voltages applied across each of the plurality of switch units 20, and transmits the acquired plurality of forward voltage signals FV and plurality of AC voltages to the control device 14b.

[0092] The control device 14b identifies which of the multiple switching elements 22 has a fault with a predetermined resistance value by comparing the periods indicating that each of the multiple forward voltage signals FV is being applied with the AC voltage applied to both ends of the switch section 20 detected by the voltage detector 50.

[0093] 4 and 5 , when the switching element 22 is normal, the forward voltage signal FV is a signal that is substantially synchronized with the AC voltage applied across the switch unit 20. When the switching element 22 is normal, the period of the forward voltage signal FV that indicates that a forward voltage is being applied to the switching element 22 overlaps only with the positive-side period of the AC voltage applied across the switch unit 20, and does not overlap with the negative-side period of the AC voltage applied across the switch unit 20. On the other hand, when a fault with a predetermined resistance value occurs in the switching element 22, the timing of the forward voltage signal FV is shifted, and the period of the forward voltage signal FV of that switching element 22 that indicates that a forward voltage is being applied to the switching element 22 overlaps with the negative-side period of the AC voltage applied across the switch unit 20.

[0094] Therefore, in one switch section 20, the control device 14b detects that the switching element 22 is normal when the period of the forward voltage signal FV indicating that a forward voltage is being applied to the switching element 22 does not overlap with the negative period of the AC voltage applied across the switch section 20. Then, in one switch section 20, the control device 14b detects that a fault with a predetermined resistance value has occurred in the switching element 22 when the period of the forward voltage signal FV indicating that a forward voltage is being applied to the switching element 22 overlaps with the negative period of the AC voltage applied across the switch section 20. Furthermore, by detecting that a fault with a predetermined resistance value has occurred in the switching element 22, the control device 14b identifies which of the multiple switching elements 22 has occurred in the fault with a predetermined resistance value.

[0095] In this way, it is not limited to comparing the periods indicating that the forward voltages of the plurality of forward voltage signals FV are being applied with the periods indicating that the reverse voltages of the plurality of reverse voltage signals RV are being applied, but it is also possible to identify which of the plurality of switching elements 22 has a fault with a predetermined resistance value by comparing the periods indicating that the forward voltages of the plurality of forward voltage signals FV are being applied with the AC voltage applied across the switch section 20. In this case, too, it is possible to obtain the same effect as in the second embodiment.

[0096] (Fourth embodiment) FIG. 8 is a block diagram schematically illustrating a control device according to the fourth embodiment. 8, the control device 14c includes a comparison circuit 60. The control device 14c inputs each of the multiple forward voltage signals FV received from the main circuit unit 12 to the comparison circuit 60. The comparison circuit 60 compares the timing of the periods indicating that a forward voltage is being applied for each of the multiple forward voltage signals FV.

[0097] As explained with reference to Figures 4 and 5, the timing of each period in the forward voltage signal FV of a faulty switching element 22 having a predetermined resistance value, which indicates that a forward voltage is being applied to the switching element 22, and the timing of each period in the forward voltage signal FV of a normal switching element 22, differs from the timing of each period in the forward voltage signal FV of a normal switching element 22.

[0098] For this reason, the control device 14c compares the timing of the periods indicating that a forward voltage is being applied for each of the multiple forward voltage signals FV in one switch section 20, and if there is a forward voltage signal FV with a different timing of the period indicating that a forward voltage is being applied compared to the other forward voltage signals FV, ​​it detects that a fault with a predetermined resistance value has occurred in the switching element 22 corresponding to that forward voltage signal FV, thereby identifying which of the multiple switching elements 22 has occurred in the fault with a predetermined resistance value.

[0099] In this way, by comparing the timing of the periods indicating that the forward voltages of the plurality of forward voltage signals FV are being applied, it is possible to identify which of the plurality of switching elements 22 has a fault with a predetermined resistance value. In this case, the same effects as those of the second and third embodiments can be obtained.

[0100] Although several embodiments of the present invention have been described above, 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 spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. [Explanation of symbols]

[0101] 2...High-level device, 10, 10b...Power conversion device, 12, 12b...Main circuit section, 14, 14a, 14b, 14c...Control device, 20...Switch section, 22...Switching element, 24...Snubber circuit, 24a...Resistor, 24b...Capacitor, 26...Voltage detector, 30, 32...OR circuit, 40...AND circuit, 42...NOT gate, 44...AND circuit, 46...OR circuit, 50...Voltage detector, 60...Comparator circuit

Claims

[Claim 1] A main circuit section having a plurality of switch sections each having a plurality of switching elements connected in series, and performing at least one of conversion from AC power to DC power and conversion from DC power to AC power by switching the plurality of switch sections; a control device that controls the power conversion by the main circuit unit; Equipped with The main circuit section includes: a plurality of forward voltage signals including a signal indicating a period during which a forward voltage is applied to a plurality of switching elements included in the plurality of switch units and a signal indicating a period during which a forward voltage is not applied, and a plurality of reverse voltage signals including a signal indicating a period during which a reverse voltage is applied to a plurality of switching elements included in the plurality of switch units, transmitting the acquired plurality of forward voltage signals and the acquired plurality of reverse voltage signals to the control device; The control device a forward voltage logical sum signal including a signal indicating a period during which a forward voltage is applied to any of the plurality of switching elements and a signal indicating a period during which a forward voltage is not applied to any of the plurality of switching elements is obtained by logical sum calculation of the plurality of forward voltage signals; a reverse voltage logical sum signal including a signal indicating a period during which a reverse voltage is applied to any of the plurality of switching elements and a signal indicating a period during which a reverse voltage is not applied to any of the plurality of switching elements is obtained by logical sum calculation of the plurality of reverse voltage signals; Based on a signal indicating a period during which the forward voltage is applied of the forward voltage logical sum signal and a signal indicating a period during which the reverse voltage is applied of the reverse voltage logical sum signal, the switch unit in which a period during which the forward voltage is applied and a period during which the reverse voltage is applied overlap is detected as the switch unit including the switching element having a predetermined resistance value in which a failure has occurred. Power conversion device.

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