JP6529040B2 - Power converter and control method thereof - Google Patents

Description

  Embodiments of the present invention relate to a power converter and a control method thereof.

  There is a multistage power converter in which a plurality of converters are connected in series. Each converter includes a plurality of switching elements. Further, the multistage power converter includes a control panel connected to each switching element. The control panel inputs a control signal to each switching element and controls on / off of each switching element to convert AC or DC input power into AC power different from input power. In the multistage power conversion device, the level of the output voltage can be changed according to the number of converters connected in series to suppress the harmonic component of the output power. It is possible to realize so-called multilevel power conversion.

  In the multi-stage power converter, each converter is provided with a short circuit. A short is connected in parallel to the converter to short the output of the converter when in the on state. If a short circuit is not provided, no current flows in the path in which each converter is connected in series when one of the converters connected in series fails, making it difficult to continue the operation. Become. If a short circuit is provided, the short circuit connected in parallel to the failed converter is turned on when one of the series connected converters fails, and the broken converter is turned on. Short circuit. As a result, even if the converter fails, current flows in the path in which each converter is connected in series, and operation can be continued with the remaining converters.

  However, providing a short circuit for each converter makes it difficult to miniaturize the power converter. For this reason, in the multistage power conversion device, it is desirable to be able to continue the operation even when a failure occurs in the converter while suppressing the hindrance to the miniaturization.

JP, 2013-27260, A

  An embodiment of the present invention provides a power conversion device capable of continuing operation even when a failure occurs in a converter while suppressing an obstacle to miniaturization, and a control method thereof.

According to an embodiment of the present invention, a power conversion device is provided that includes an inverter circuit, a control panel, a plurality of failure detection units, and a control unit. The inverter circuit is connected to a power supply and an AC load, converts input power input from the power supply into AC output power different from the input power, and supplies the output power to the AC load. The inverter circuit includes a converter unit in which a plurality of converters are connected in series. Each of the plurality of converters includes a first switching element including a pair of main terminals and a control terminal, a pair of main terminals and a control terminal, and is connected in series to the first switching element. A second switching element, a charge storage element connected in parallel to the first switching element and the second switching element, and a first connected between the first switching element and the second switching element It includes a connection terminal and a second connection terminal connected to the main terminal on the opposite side of the main terminal connected to the second switching element of the first switching element. The control panel generates, for each of the plurality of converters, a control signal for controlling on / off of the first switching element and the second switching element, and the control signal of the plurality of converters. By inputting to each, conversion of the electric power by the said inverter circuit is controlled. The plurality of failure detection units are provided in the inverter circuit corresponding to each of the plurality of converters, detect a failure of the first switching element and the second switching element, and detect the failure. Output a detection signal indicating The control unit switches on and off of the first switching element and the second switching element based on the detection signal, thereby establishing a conductive state between the first connection terminal and the second connection terminal. Do. The failure mode of the first switching element and the second switching element is a short circuit failure. Each of the first switching element and the second switching element includes a first electrode, a second electrode, a semiconductor chip provided between the first electrode and the second electrode, and the first electrode And a case for holding the second electrode and the semiconductor chip. When at least one of the first switching element and the second switching element has a short circuit failure, the current square product of the current flowing in the at least one of the first switching element and the second switching element is equal to or less than the energy resistance of the case. It is.

  There is provided a power conversion device and a control method thereof that can continue operation even when a failure occurs in a converter while suppressing an obstacle to miniaturization.

It is a block diagram showing the power converter concerning a 1st embodiment typically. It is a block diagram showing the converter concerning a 1st embodiment typically. FIG. 3A and FIG. 3B are schematic views of the switching element according to the first embodiment. FIG. 4A to FIG. 4C are graphs schematically showing the characteristics of the switching element according to the first embodiment. It is a flow chart which expresses operation of a power converter concerning a 1st embodiment typically. It is a block diagram which represents typically another converter which concerns on 1st Embodiment. It is a block diagram showing the power converter concerning a 2nd embodiment typically. It is a block diagram showing the converter concerning a 2nd embodiment typically. It is a block diagram which represents typically another converter which concerns on 2nd Embodiment.

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

First Embodiment
FIG. 1 is a block diagram schematically illustrating the power conversion device according to the first embodiment.
As shown in FIG. 1, the power conversion device 10 includes an inverter circuit 12 and a control board 14.

  The inverter circuit 12 is connected to the power supply 2 and the AC load 4. The inverter circuit 12 converts the input power input from the power supply 2 into an AC output power different from the input power, and supplies the output power to the AC load 4. In this example, the input power is three-phase AC power. The inverter circuit 12 converts, for example, three-phase AC input power into three-phase AC output power having different effective values. The inverter circuit 12 converts, for example, input power into output power of an effective value corresponding to the AC load 4.

  The input power and the output power may be, for example, single-phase alternating current or two-phase alternating current. The inverter circuit 12 may also convert, for example, three-phase AC input power into single-phase AC or two-phase AC output power.

  The AC load 4 is, for example, an electronic device such as a three-phase AC motor. In this case, the inverter circuit 12 drives the AC load 4 by supplying the output power to the AC load 4. The AC load 4 may be, for example, a power system such as a transmission line that supplies power to a power receiving facility of a consumer. In this case, the inverter circuit 12 performs so-called reverse power flow, which supplies output power to the power system.

  In this example, power converter 10 further includes a transformer 16. The inverter circuit 12 is connected to the power supply 2 via the transformer 16. The transformer 16 includes a primary winding 16a connected to the power supply 2, and a plurality of secondary windings 16b magnetically coupled to the primary winding 16a. The inverter circuit 12 is connected to each of the secondary windings 16b. In this example, the transformer 16 is a three-phase transformer.

  In the specification of the present application, “connection” includes, in addition to the case of direct contact and connection, the case of being electrically connected via another conductive member or the like. In addition, the case where they are magnetically coupled via a transformer or the like is also included in "connection".

  The control board 14 is connected to the inverter circuit 12. The control panel 14 controls the conversion of power by the inverter circuit 12. The control panel 14 includes, for example, a processor such as a CPU or an MPU. The control board 14 controls the operation of the inverter circuit 12 by, for example, reading a predetermined program from a memory (not shown) and sequentially processing the program. The memory storing the program may be provided in the control board 14 or may be provided separately from the control board 14 and connected to the control board 14.

  The inverter circuit 12 includes a converter unit 20 in which a plurality of converters 22 are connected in series. The converter unit 20 is provided corresponding to the phase of the output power. Therefore, in this example, three converter units 20 corresponding to each phase of three-phase alternating current are provided in the inverter circuit 12. For example, if the output power is a single phase alternating current, the number of converter units 20 may be one.

  In this example, one end of each converter unit 20 is connected to each other, and the other end of each converter unit 20 is connected to the AC load 4. That is, in this example, each converter unit 20 is Y-connected. The connection of each converter unit 20 may be, for example, a delta connection. That is, the alternating current load 4 may be connected to both ends of each converter unit 20. For example, two sets of converter units 20 may be V-connected. In the inverter circuit 12, at least one end of the converter unit 20 is an AC output point. In the inverter circuit 12, output power is supplied from the converter unit 20 to the AC load 4.

  In this example, each transducer unit 20 includes three transducers 22 connected in series. The number of converters 22 provided in each converter unit 20 may be three or more. For example, in the inverter circuit 12 for high voltage, about 100 to about 120 converters 22 are connected in series in each of the converter units 20. The number of converters 22 provided in each converter unit 20 is substantially the same. For example, when a large number of converters 22 are connected, the number of converters 22 provided in each converter unit 20 may be different within a range that does not affect the operation of the inverter circuit 12. For example, when one converter unit 20 is provided with 100 converters 22, the number of converters 22 provided in another converter unit 20 may be different from one to two.

  Each of the converters 22 is connected to each of the secondary windings 16 b of the transformer 16. Thereby, the input power of the power supply 2 is supplied to each converter 22 through the transformer 16. For example, power obtained by transforming the input power of the power source 2 by the transformer 16 is supplied to each converter 22. In this example, three-phase AC power is supplied to each converter 22. The number of secondary windings 16 b is substantially the same as the number of converters 22. Thus, in this example, nine secondary windings 16 b are provided in the transformer 16. The number of secondary windings 16 b provided in the transformer 16 may be equal to or greater than the number of converters 22 provided in the inverter circuit 12.

FIG. 2 is a block diagram schematically showing the converter according to the first embodiment.
As shown in FIG. 2, the converter 22 includes a first connection terminal 22 a, a second connection terminal 22 b, a first switching element 31, a second switching element 32, a third switching element 33, and a fourth. It includes a switching element 34, a charge storage element 35, a resistance element 36, an inductor 37, a rectification circuit 38, a drive circuit 40, and a failure detection unit 42.

  Each of the switching elements 31 to 34 includes a pair of main terminals and a control terminal. The control terminal controls the current flowing between the pair of main terminals. For each of the switching elements 31 to 34, for example, a self arc extinguishing element such as an IGBT is used. The pair of main terminals is, for example, an emitter and a collector, and the control terminal is, for example, a gate. Further, as each of the switching elements 31 to 34, a normally-off type element is used.

  The pair of main terminals (current paths) of the second switching element 32 is connected in series to the pair of main terminals of the first switching element 31. The pair of main terminals of the fourth switching element 34 is connected in series to the pair of main terminals of the third switching element 33. The third switching element 33 and the fourth switching element 34 are connected in parallel to the first switching element 31 and the second switching element 32.

  The first connection terminal 22 a is connected between the first switching element 31 and the second switching element 32. The second connection terminal 22 b is connected between the third switching element 33 and the fourth switching element 34. In this example, the second connection terminal 22 b is connected to the main terminal on the opposite side to the main terminal connected to the second switching element 32 of the first switching element 31 via the third switching element 33.

  In the converter 22, each connection terminal 22a, 22b becomes an alternating current output point. That is, in this example, the converter 22 configures a full bridge circuit by the switching elements 31 to 34. The first switching element 31 and the third switching element 33 are so-called low side switches, and the second switching element 32 and the fourth switching element 34 are so-called high side switches.

  The converters 22 included in the converter unit 20 are connected in series with one another through the connection terminals 22a and 22b. That is, the first connection terminal 22 a of one converter 22 is connected to the second connection terminal 22 b of another converter 22.

  Further, a diode 51 is connected to the first switching element 31 in antiparallel to the pair of main terminals. The forward direction of the diode 51 is reverse to the direction of the current flowing between the pair of main terminals of the first switching element 31. Similarly, in the second switching element 32, a diode 52 is connected in antiparallel to the pair of main terminals. In the third switching element 33, a diode 53 is connected in antiparallel to the pair of main terminals. A diode 54 is connected to the fourth switching element 34 in antiparallel to the pair of main terminals. Each of the diodes 51 to 54 is a so-called reflux diode.

  The charge storage element 35 is connected in parallel to the first switching element 31 and the second switching element 32, and is connected in parallel to the third switching element 33 and the fourth switching element 34. The converter 22 may include, for example, a plurality of charge storage elements 35 connected in series. For example, a capacitor or a storage battery is used for the charge storage element 35. The charge storage element 35 may be any element capable of storing charge.

  The resistive element 36 is provided between the charge storage element 35 and each of the switching elements 32 and 34 on the high side. The resistance element 36 is, for example, at least one of an internal resistance of the charge storage element 35 and a wiring resistance between the charge storage element 35 and each of the switching elements 32 and 34 on the high side.

  The inductor 37 is provided between the charge storage element 35 and each of the switching elements 32 and 34 on the high side. The inductor 37 is, for example, a wiring inductance between the charge storage element 35 and each of the switching elements 32 and 34 on the high side. Thus, the resistive element 36 and the inductor 37 are, for example, a resistor and an inductor that are generated secondarily in the circuit by wiring or the like. The resistive element 36 and the inductor 37 may be provided as physical elements, for example.

FIG. 3A and FIG. 3B are schematic views of the switching element according to the first embodiment. FIG. 3A is a plan view schematically showing the first switching element 31, and FIG. 3B is a side view schematically showing the first switching element 31.
As shown in FIGS. 3A and 3B, the first switching element 31 includes the semiconductor chip 60, the first electrode 61, the second electrode 62, the wiring 63, and the case 64. Including.

  The semiconductor chip 60 includes a pair of main terminals and a control terminal. For the semiconductor chip 60, for example, a vertical chip such as an IGBT is used. The first electrode 61 is connected to one of the main terminals. The second electrode 62 is connected to the other main terminal. The wiring 63 is connected to the control terminal. The semiconductor chip 60 is provided between the first electrode 61 and the second electrode 62. The semiconductor chip 60 is, for example, in pressure contact with the first electrode 61 and the second electrode 62. For the first electrode 61 and the second electrode 62, for example, a metal material having high electrical conductivity and thermal conductivity such as copper is used.

  The case 64 is, for example, cylindrical. The case 64 holds the semiconductor chip 60, the first electrode 61, the second electrode 62, and the wiring 63 in an internal space. The semiconductor chip 60 is pressure-welded between the first electrode 61 and the second electrode 62 in the case 64. For the case 64, an insulating material such as ceramic or resin is used, for example.

  That is, the first switching element 31 is a so-called pressure contact type semiconductor element. The failure mode for the overcurrent or overvoltage of the first switching element 31 is a short circuit failure. In the first switching element 31, when an overcurrent or an overvoltage occurs between the first electrode 61 and the second electrode 62, the first electrode 61 and the second electrode 62 conduct.

  Elements substantially the same as the first switching element 31 are used for the second switching element 32 to the fourth switching element 34. For the second switching element 32 to the fourth switching element 34, pressure-contact type semiconductor elements are used. The failure mode for the overcurrent or overvoltage of the second switching element 32 to the fourth switching element 34 is a short circuit failure. Therefore, the detailed description about the 2nd switching element 32-the 4th switching element 34 is abbreviate | omitted.

FIG. 4A to FIG. 4C are graphs schematically showing the characteristics of the switching element according to the first embodiment.
FIG. 4A shows an example of a short circuit current flowing to the first switching element 31 based on the voltage of the charge storage element 35 when the first switching element 31 has a short circuit failure.
FIG. 4B illustrates an example of the voltage of the charge storage element 35 when the first switching element 31 has a short circuit failure.
FIG. 4C shows an example of a current square product (an integral value of squares of the short circuit current) of the short circuit current shown in FIG. 4A. Further, in FIG. 4C, the energy tolerance of the case 64 of the first switching element 31 is indicated by a broken line.

  As shown in FIGS. 4A to 4C, in the converter 22, the current square product of the short circuit current is equal to or less than the energy tolerance of the case 64. When the first switching element 31 has a short circuit failure, the energy applied to the first switching element 31 is proportional to the square of the short circuit current. If the energy applied to the first switching element 31 exceeds the energy tolerance of the case 64, for example, the current may be concentrated at the broken part of the element, and the influence may be expanded to the case 64. That is, there is a possibility that the first switching element 31 may become an open failure from a short circuit failure.

  Therefore, the current squared product of the short circuit current is made equal to or less than the energy tolerance of case 64. Thereby, for example, the failure mode of the first switching element 31 can be appropriately made short circuit failure. As described above, elements substantially the same as the first switching element 31 are used for the second switching element 32 to the fourth switching element 34. Therefore, also in the second switching element 32 to the fourth switching element 34, the current square product of the short circuit current is equal to or less than the energy tolerance of the case 64, similarly to the first switching element 31.

  The current squared product of the short circuit current is adjusted, for example, by the capacity and voltage of the charge storage element 35. That is, the total energy applied to the first switching element 31 at the time of failure is adjusted by the capacity and voltage of the charge storage element 35.

  Further, the rise of the short circuit current flowing to the element at the time of failure is adjusted, for example, by the constant of the resistance element 36 and the inductor 37. If the rise of the short circuit current is early, the current squared product of the short circuit current tends to exceed the energy tolerance of the case 64 at the rise of the short circuit current. Therefore, by adjusting the resistance value of the resistance element 36 and the inductance value of the inductor 37, the rising of the short circuit current is delayed. For example, the rising of the short circuit current can be delayed by relatively increasing the inductance value of the inductor 37. The inductance value of the inductor 37 can be increased, for example, by lengthening a wire (for example, a bus bar) between the charge storage element 35 and each of the switching elements 32 and 34 on the high side.

  Thus, the total energy applied to the first switching element 31 at the time of failure and the rise of the short circuit current are adjusted. Thereby, the current square product of the short circuit current can be made equal to or less than the energy tolerance of case 64.

  Returning to FIG. 2, the rectifier circuit 38 is connected in parallel to the charge storage element 35. The rectifier circuit 38 is connected to the secondary winding 16 b of the transformer 16. In this example, the rectifier circuit 38 is a three-phase bridge circuit. The rectifier circuit 38 converts three-phase AC power supplied from the secondary winding 16b into rectified power (eg, pulsating power).

  The charge storage element 35 converts the rectified power into DC power by smoothing the rectified power output from the rectifier circuit 38. That is, the charge storage element 35 is a so-called smoothing capacitor. Here, the voltage of the DC power output from the charge storage element 35 is referred to as a voltage Vc.

  In the converter 22, when the second switching element 32 and the third switching element 33 are turned on and the first switching element 31 and the fourth switching element 34 are turned off, + Vc is applied between the connection terminals 22a and 22b. It is output.

  When the first switching element 31 and the fourth switching element 34 are turned on and the second switching element 32 and the third switching element 33 are turned off, -Vc is output between the connection terminals 22a and 22b.

  Then, when the first switching element 31 and the third switching element 33 are turned on and the second switching element 32 and the fourth switching element 34 are turned off, or the second switching element 32 and the fourth switching element 34 are When the first switching element 31 and the third switching element 33 are turned off in the on state, 0 V is output between the connection terminals 22a and 22b.

  Thus, the converter 22 can output three levels of power of + Vc, 0, and -Vc by the combination of the switching elements 31 to 34 that are turned on and off. The converter 22 may be called, for example, a power cell.

  In the inverter circuit 12, the output voltage of each converter unit 20 is a voltage obtained by adding the output voltage of each converter 22. That is, the output voltage of each converter unit 20 changes to seven levels of + 3Vc, + 2Vc, + Vc, 0, -Vc, -2Vc, and -3Vc. The power converter 10 is a so-called MV (medium voltage) type power converter.

  The drive circuit 40 is connected to the control board 14 via a signal line 23. The control board 14 transmits a control signal for controlling on / off of each of the switching elements 31 to 34 to the drive circuit 40 via the signal line 23. The drive circuit 40 switches on / off of the switching elements 31 to 34 based on the input control signal. Thus, on / off of each of the switching elements 31 to 34 is controlled according to the control signal from the control panel 14. The control panel 14 generates a control signal for each converter 22 and controls on / off of each switching element 31 to 34 of each converter 22. Thus, the control panel 14 controls the conversion of power by the inverter circuit 12.

  The failure detection unit 42 detects a failure of each of the switching elements 31 to 34. When the failure detection unit 42 detects a failure in each of the switching elements 31 to 34, the failure detection unit 42 outputs a detection signal indicating a detection result of the failure in each of the switching elements 31 to 34. In this example, the failure detection unit 42 is connected to the control board 14 via the signal line 24. When the failure detection unit 42 detects a failure, the failure detection unit 42 outputs a detection signal to the control board 14.

  In this example, transmission and reception of signals between the control panel 14 and the converter 22 are performed using two signal lines 23 and 24. The transmission and reception of signals between the control board 14 and the converter 22 may be performed by, for example, one signal line without being limited thereto. That is, the control signal input from the control panel 14 to the drive circuit 40 and the detection signal input from the failure detection unit 42 to the control panel 14 may be transmitted and received via the same signal line.

  The failure detection unit 42 is connected to each of the connection terminals 22a and 22b. The failure detection unit 42 detects a failure of each of the switching elements 31 to 34, for example, based on the voltage between the connection terminals 22a and 22b when the switching elements 31 to 34 are turned off.

  When the switching elements 31 to 34 are normal, the voltage of the charge storage element 35 appears between the connection terminals 22 a and 22 b. More specifically, a negative bias voltage in which the potential of the second connection terminal 22b is higher than the potential of the first connection terminal 22a appears between the connection terminals 22a and 22b.

  On the other hand, when one of the switching elements 31 to 34 fails and is shorted, the voltage of the charge storage element 35 is also applied between the connection terminals 22a and 22b even when the switching elements 31 to 34 are turned off. It will not appear.

  Therefore, when the voltage is detected when the switching elements 31 to 34 are turned off, the failure detection unit 42 determines that the switching elements 31 to 34 are normal, and no voltage is detected. In the case, it is determined that one of the switching elements 31 to 34 is broken. That is, the failure detection unit 42 detects a failure of each of the switching elements 31 to 34 and outputs a detection signal when no voltage is detected. As described above, in this example, the failure detection unit 42 generates a detection signal indicating that any one of the switching elements 31 to 34 is broken, and outputs the detection signal to the control panel 14.

  The control panel 14 is provided with a control unit 26. When a detection signal is input from the failure detection unit 42 of the predetermined converter 22, the control unit 26 inputs a control signal at the time of failure detection to the drive circuit 40 of the converter 22 in which the failure is detected.

  When receiving the control signal at the time of failure detection, the drive circuit 40 brings the connection terminals 22a and 22b into conduction by turning on and off the switching elements 31 to 34. That is, in accordance with the detection signal of the failure detection unit 42, the control unit 26 brings the connection terminals 22a and 22b into conduction.

  The drive circuit 40 turns each of the first switching element 31 and the third switching element 33 on the low side into the on state, and turns the second switching element 32 and the fourth switching element 34 on the high side into the off state, for example. The connection terminals 22a and 22b are made conductive. For example, the drive circuit 40 turns on the second switching element 32 and the fourth switching element 34 on the high side, and turns off the first switching element 31 and the third switching element 33 on the low side, for example. The connection terminals 22a and 22b may be in a conductive state. At this time, since the failure mode of each of the switching elements 31 to 34 is a short circuit failure as described above, the failed switching element does not interfere with the setting of the conduction state.

  Here, the "conductive state" is a state in which the switching elements 31 to 34 are selectively turned on to allow current to flow between the connection terminals 22a and 22b. In other words, the connection terminals 22a and 22b are shorted. On the other hand, the "non-conduction state" is a state in which the switching elements 31 to 34 are turned off so that substantially no current flows between the connection terminals 22a and 22b. The “non-conduction state” may be, for example, a state in which a weak current in a range not affecting the operation of the converter 22 flows between the connection terminals 22 a and 22 b.

  The control signal at the time of failure detection may be a control signal (gate signal) itself input to the control terminal of each of the switching elements 31 to 34, or may be a signal instructing the drive circuit 40 to control each of the switching elements 31 to 34.

  Further, the control panel 14 determines, based on the detection signals from the converters 22, whether or not the number of converters 22 that have detected a failure in each of the switching elements 31 to 34 has reached a predetermined number. For example, the control panel 14 determines, for each converter unit 20, whether or not the number of converters 22 that have detected a failure has reached a predetermined number. For example, with respect to the number of converters 22 included in the converter unit, it is determined whether the number of converters 22 in which a failure is detected has reached a predetermined number.

  When it is determined that the control board 14 has reached the predetermined number, the operation of the inverter circuit 12 is stopped. The control panel 14 stops the operation of the inverter circuit 12 by, for example, stopping the input of the control signal to each converter 22 and turning off the switching elements 31 to 34. That is, the output of the power from the inverter circuit 12 is stopped. For example, when 120 converters 22 are connected in series to the converter unit 20, the control panel 14 determines that the predetermined number has been reached when a fault is detected by about 6 converters 22. Then, the operation of the inverter circuit 12 is stopped.

  The control panel 14 may determine, for example, based on the total number of the converters 22 included in the inverter circuit 12, whether or not the predetermined number has been reached. That is, it may be determined whether the number of converters 22 that have detected a failure has reached a predetermined number with respect to the total number of converters 22. For example, both the determination for each converter unit 20 and the determination for the total number may be performed.

FIG. 5 is a flowchart schematically illustrating the operation of the power conversion device according to the first embodiment.
Next, based on the flowchart shown in FIG. 5, the operation of the power conversion device 10 will be described. When the control panel 14 of the power conversion device 10 starts operation, it generates a control signal for each converter 22 and transmits the control signal to each converter 22. The control signal is input to the drive circuit 40 via the signal line 23. The drive circuit 40 controls on / off of each of the switching elements 31 to 34 based on the input control signal. Thereby, the input power of the power source 2 is converted into an AC output power corresponding to the AC load 4, and the output power is supplied to the AC load 4.

  After starting the operation, the failure detection unit 42 of each converter 22 detects a failure of each of the switching elements 31 to 34 (step S1 in FIG. 5). When the failure detection unit 42 detects a failure in each of the switching elements 31 to 34, the failure detection unit 42 inputs a detection signal to the control panel 14.

  The failure detection may be performed, for example, at an arbitrary timing at which each of the switching elements 31 to 34 is turned off. The timing at which the failure detection is performed may be different for each converter 22, for example. For example, the switching elements 31 to 34 of the converters 22 may be simultaneously turned off, and failure detection may be performed at each of the converters 22 substantially simultaneously. For example, the power conversion device 10 may be provided with a failure detection operation mode for turning off the switching elements 31 to 34 of the converters 22 separately from the normal operation mode for performing power conversion.

  When a detection signal is input from the failure detection unit 42 of the predetermined converter 22, the control unit 26 of the control board 14 inputs a control signal at the time of failure detection to the drive circuit 40 of the converter 22 in which the failure is detected. Do. The drive circuit 40 switches on / off of the switching elements 31 to 34 as described above according to the input of the command signal, and brings the connection terminals 22a and 22b into conduction (step S2 in FIG. 5).

  Control panel 14 determines whether or not the number of converters 22 that have detected a failure in each of switching elements 31 to 34 has reached a predetermined number based on the detection signal from each converter 22 (step in FIG. 5) S3). If the control board 14 determines that the number is smaller than the predetermined number, the control board 14 continues transmitting the control signal to each converter 22. That is, when it is determined that the control board 14 is less than the predetermined number, the operation of the inverter circuit 12 is continued.

  On the other hand, when it is determined that the control board 14 has reached the predetermined number, the control board 14 stops transmitting the control signal to each converter 22 and stops the operation of the inverter circuit 12 (step S4 in FIG. 5).

  As described above, each of the switching elements 31 to 34 is a normally off type. For this reason, for example, when one of the switching elements 31 to 34 fails and switching between on and off can not be performed, there is a possibility that the connection terminals 22 a and 22 b may be in a non-conductive state. In any of the converters 22 included in the converter unit 20, when the connection terminals 22a and 22b are in a non-conductive state, no current flows in the converter unit 20 itself. That is, continuation of the operation of the inverter circuit 12 becomes difficult.

  On the other hand, in the power conversion device 10 according to the present embodiment, when the failure detection unit 42 of each converter 22 detects a failure in each of the switching elements 31 to 34, the connection terminals 22a and 22b are electrically connected. Put in a state. Thus, even when an abnormality occurs in the control signal, current can be supplied to the converter unit 20. In other words, the converter 22 in which the abnormality has occurred can be bypassed.

  Therefore, in the power conversion device 10, even when a failure occurs in each of the switching elements 31 to 34 in any of the converters 22, the operation of the inverter circuit 12 can be continued. Further, in the power conversion device 10, it is not necessary to provide a short circuit or the like corresponding to each of the converters 22. Therefore, there is no hindrance to downsizing of the power conversion device 10. For example, an increase in the number of parts of the power conversion device 10 can also be suppressed. For example, the increase in the manufacturing cost of the power converter 10 can be suppressed. As described above, in the power conversion device 10, the operation of the inverter circuit 12 can be continued even when a failure occurs in the converter 22 while suppressing the hindrance to the miniaturization.

  In power converter 10, control panel 14 determines whether the number of converters 22 that have detected a failure has reached a predetermined number, and stops operation of inverter circuit 12 when the number has reached the predetermined number. Let Thereby, for example, it is possible to suppress an excessive load on each of the remaining transducers 22 that operate normally. Operation of power converter 10 can be stabilized more.

  When the control panel 14 determines that it is less than the predetermined number and continues the operation of the inverter circuit 12, for example, the output voltage of each converter unit 20 is biased due to the difference in the number of converters 22 operating normally. Do not occur. The control panel 14 adjusts the output voltage of each converter 22 for each converter unit 20 according to, for example, the number of converters 22 operating normally.

  For example, when a failure is detected, the output voltage of each remaining converter 22 of the same converter unit 20 as the converter 22 which detects the failure is increased. For example, the output voltage of the converter 22 that has detected a failure is equally divided by the remaining converters 22. That is, even when a failure is detected in the converter 22, the output voltage of the converter unit 20 is made substantially the same as in the normal state. Thereby, for example, even when the converter 22 that has detected a failure is bypassed, an appropriate output power can be obtained. The predetermined number of converters 22 determined by the control panel 14 may be set, for example, to a number that makes it difficult to adjust the output voltage of each converter unit 20.

  In each of the above-described embodiments, the failure detection unit 42 is provided in each converter 22. Without being limited to this, the failure detection unit 42 may be provided separately from the converter 22. The failure detection unit 42 may be provided in the inverter circuit 12 and may detect a failure in each of the switching elements 31 to 34.

  In the said embodiment, the failure detection of each switching element 31-34 is performed based on the voltage between each connection terminal 22a, 22b. The method of detecting the failure of each of the switching elements 31 to 34 is not limited to this, and any method capable of detecting the failure of each of the switching elements 31 to 34 may be used.

  For example, a plurality of failure detection units 42 are provided corresponding to each of the switching elements 31 to 34 so that each failure of each of the switching elements 31 to 34 can be individually detected based on the voltage between the main terminals and the like. May be In this case, the failure detection unit 42 generates a detection signal representing a failed element among the switching elements 31 to 34, and outputs the detection signal.

  When the control unit 26 receives a detection signal capable of identifying the failed element, the control unit 26 determines an element necessary for bringing the connection terminals 22a and 22b into conduction, and performs control to turn the element on. Input a signal.

  For example, when a failure of the first switching element 31 is detected, the control unit 26 generates a control signal for turning on the third switching element 33, and inputs the control signal to the drive circuit 40. For example, when a failure of the second switching element 32 is detected, the control unit 26 generates a control signal for turning on the fourth switching element 34, and inputs the control signal to the drive circuit 40. As a result, for example, the connection terminals 22a and 22b can be efficiently conducted between the connection terminals 22a and 22b by using the short-circuited element.

  In the above embodiment, the failure detection unit 42 detects a failure in each of the switching elements 31 to 34 and inputs a detection signal to the control unit 26. The detection signal is not limited to this, and may be input to the control unit 26 from, for example, an external device. Furthermore, a worker who performs maintenance on the power conversion device 10 may be able to manually input a detection signal to the control unit 26 via an input unit such as a keyboard or a mouse.

FIG. 6 is a block diagram schematically showing another converter according to the first embodiment.
FIG. 6 schematically illustrates another converter 28 used in place of the converter 22 of the above embodiment. In addition, about a thing substantially the same in function and structure as the said embodiment, a same sign is attached | subjected and detailed description is abbreviate | omitted.

  As shown in FIG. 6, the converter 28 further includes a control unit 26. In this example, when the failure detection unit 42 detects a failure in each of the switching elements 31 to 34, the failure detection unit 42 outputs a detection signal to the control unit 26 provided in the converter 28. When the detection signal is input from the failure detection unit 42, the control unit 26 inputs a control signal at the time of failure detection to the drive circuit 40. When receiving the control signal at the time of failure detection, the drive circuit 40 brings the connection terminals 22a and 22b into conduction by turning on and off the switching elements 31 to 34. Thus, the control unit 26 may be provided for each of the converters 28.

Second Embodiment
FIG. 7 is a block diagram schematically showing a power conversion device according to a second embodiment.
As shown in FIG. 7, the inverter circuit 112 of the power conversion device 100 includes a pair of input terminals 80 a and 80 b and first to sixth six arm portions 81 a to 81 f.

  The pair of input terminals 80 a and 80 b are connected to the power supply 2. In this example, the power supply 2 is a DC power supply. The input power supplied from the power supply 2 is DC power. The input terminal 80 a is connected to the anode of the power supply 2, and the input terminal 80 b is connected to the negative electrode of the power supply 2. The power source 2 is, for example, a rectifier that converts AC power supplied from a commercial power source or the like into DC power. The power source 2 may be any power source capable of supplying DC power.

  The first arm portion 81a is connected to the input terminal 80a. The second arm 81b is connected between the first arm 81a and the input terminal 80b. That is, the first arm 81 a and the second arm 81 b are connected in series to the power supply 2.

  The third arm portion 81c is connected to the input terminal 80a. The fourth arm 81 d is connected between the third arm 81 c and the input terminal 80 b. That is, the third arm portion 81c and the fourth arm portion 81d are connected in parallel to the first arm portion 81a and the second arm portion 81b.

  The fifth arm 81e is connected to the input terminal 80a. The sixth arm portion 81 f is connected between the fifth arm portion 81 e and the input terminal 80 b. That is, the fifth arm portion 81e and the sixth arm portion 81f are connected in parallel to the first arm portion 81a and the second arm portion 81b, and are connected to the third arm portion 81c and the fourth arm portion 81d. Connected in parallel.

  In the inverter circuit 112, a first leg LG1 is configured by the first arm portion 81a and the second arm portion 81b, a second leg LG2 is configured by the third arm portion 81c and the fourth arm portion 81d, and a fifth arm portion 81e The third leg LG3 is configured by the sixth arm portion 81f. That is, in this example, the inverter circuit 112 is a three-leg, six-arm three-phase inverter. The inverter circuit 112 may be, for example, a two-leg, four-arm single-phase inverter. That is, the inverter circuit 112 should just contain at least the 1st arm part 81a-the 4th arm part 81d.

  Each of the arm units 81a to 81f includes a plurality of transducers 82 connected in series. That is, in the inverter circuit 112, each of the arm units 81a to 81f includes the converter unit 20. In this example, power converter 100 is a so-called MMC (Modular Multilevel Converter) type power converter.

  In the inverter circuit 112, a connection point of the first arm 81a and the second arm 81b, a connection point of the third arm 81c and the fourth arm 81d, and a fifth arm 81e and a sixth arm 81f. Each of the connection points with is an AC output point. Accordingly, in the inverter circuit 112, the AC load 4 is connected to each connection point of each of the arm portions 81a to 81f.

FIG. 8 is a block diagram schematically showing a converter according to the second embodiment.
As shown in FIG. 8, the converter 82 includes a first connection terminal 82 a, a second connection terminal 82 b, a first switching element 31, a second switching element 32, a charge storage element 35, and a resistance element 36. , An inductor 37, and a failure detection unit 42.

  The pair of main terminals of the second switching element 32 is connected in series to the pair of main terminals of the first switching element 31. The charge storage element 35 is connected in parallel to the first switching element 31 and the second switching element 32. The first connection terminal 82 a is connected between the first switching element 31 and the second switching element 32. The second connection terminal 82 b is connected to the main terminal opposite to the main terminal connected to the second switching element 32 of the first switching element 31. The resistive element 36 is provided between the charge storage element 35 and the second switching element 32. The inductor 37 is provided between the charge storage element 35 and the second switching element 32.

  In the converter 82, the rectifier circuit 38 is omitted. The supply of power to the converter 82 takes place via the respective connection terminals 82a, 82b. In this example, the converter 82 is a so-called bi-directional chopper. The first switching element 31 is a so-called low side switch, and the second switching element 32 is a so-called high side switch.

  The failure detection unit 42 of the converter 82 detects, for example, a failure of each of the switching elements 31 and 32, and outputs a detection signal to the control unit 26 of the control panel 14. When the detection signal is input from the failure detection unit 42, the control unit 26 inputs a control signal at the time of failure detection to the drive circuit 40. When receiving the control signal at the time of failure detection, the drive circuit 40 turns on the first switching element 31 and turns off the second switching element 32 to turn on the connection terminals 22 a and 22 b. .

  Thereby, also in power converter 100, converter 82 which abnormality has generated can be bypassed. Therefore, in the power conversion device 100 as well as the power conversion device 10 of the first embodiment, the operation of the inverter circuit 112 is continued even when an abnormality in the control signal occurs in any of the converters 82. It can be done. Also in the power conversion device 100 according to the present embodiment, the operation of the inverter circuit 12 can be continued even when a failure occurs in the converter 22 while suppressing the hindrance to downsizing. The control unit 26 may be provided in the converter 82.

  In the converter 82, when the first switching element 31 has a short circuit failure, the connection terminals 22a and 22b are already in a conducting state by the first switching element 31 having the short circuit failure. Therefore, for example, when detecting the failure of each of the switching elements 31 and 32 separately, even when the failure of the first switching element 31, the control signal at the time of failure detection is not input from the control unit 26 to the drive circuit 40. Good.

FIG. 9 is a block diagram schematically showing another converter according to the second embodiment.
As shown in FIG. 9, the converter 84 further includes a third switching element 33 and a fourth switching element 34. The pair of main terminals of the fourth switching element 34 is connected in series to the pair of main terminals of the third switching element 33. The third switching element 33 and the fourth switching element 34 are connected in parallel to the first switching element 31 and the second switching element 32. The charge storage element 35 is connected in parallel to the first switching element 31 and the second switching element 32, and is connected in parallel to the third switching element 33 and the fourth switching element 34.

  The first connection terminal 84 a of the converter 84 is connected between the first switching element 31 and the second switching element 32. The second connection terminal 84 b is connected between the third switching element 33 and the fourth switching element 34. In this example, the second connection terminal 84 b is connected to the main terminal on the opposite side to the main terminal connected to the second switching element 32 of the first switching element 31 via the third switching element 33. That is, in this example, the converter 84 is a full bridge circuit.

  When receiving the control signal at the time of failure detection, the drive circuit 40 of the converter 84 turns on the first switching element 31 and the third switching element 33 on the low side as in the first embodiment, thereby turning the high side By turning off the second switching element 32 and the fourth switching element 34 on the side, the connection terminals 84 a and 84 b are brought into conduction. Alternatively, the second switching element 32 and the fourth switching element 34 on the high side are turned on, and the first switching element 31 and the third switching element 33 on the low side are turned off. Make the connection between them.

  Thereby, also in the converter 84, the converter 84 in which the abnormality has occurred can be bypassed. Even when the converter 84 is used, the operation of the inverter circuit 12 can be continued even when a failure occurs in the converter 22 while suppressing an obstacle to miniaturization as in the above embodiment. . Thus, the converter 84 used for the MMC type power converter 100 may be a full bridge circuit.

  In each of the above-mentioned embodiments, the MV type power converter 10 and the MMC type power converter 100 are shown. The power converter is not limited to this, and may be another power converter in which a plurality of converters are connected in series.

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

  DESCRIPTION OF SYMBOLS 2 ... Power supply, 4 ... AC load, 10, 100 ... Power converter device, 12, 112 ... Inverter circuit, 14 ... Control board, 16 ... Transformer, 20 ... Converter unit, 22, 28 ... Converter, 23, 24 ... Signal line 26 control unit 31 first switching element 32 second switching element 33 third switching element 34 fourth switching element 35 charge storage element 36 resistance element 38 rectification Circuit 40 40 Drive circuit 42 Fault detection unit 51 to 54 Diode 60 Semiconductor chip 61 First electrode 62 Second electrode 63 Wiring 64 Case Case 81a to 81f Arm portion , 82, 84 ... converter

Claims (4)

An inverter circuit connected to a power source and an AC load, which converts input power input from the power source into AC output power different from the input power, and supplies the output power to the AC load,
Including a converter unit in which a plurality of converters are connected in series;
Each of the plurality of transducers is
A first switching element including a pair of main terminals and a control terminal;
A second switching element including a pair of main terminals and a control terminal, and connected in series to the first switching element;
A charge storage element connected in parallel to the first switching element and the second switching element;
A first connection terminal connected between the first switching element and the second switching element;
A second connection terminal connected to the main terminal opposite to the main terminal connected to the second switching element of the first switching element;
An inverter circuit, including
A control signal for controlling on / off of the first switching element and the second switching element is generated for each of the plurality of converters, and the control signal is input to each of the plurality of converters. A control panel for controlling the conversion of power by the inverter circuit;
A plurality of switches provided in the inverter circuit corresponding to each of the plurality of converters, detecting a failure of the first switching element and the second switching element, and outputting a detection signal indicating a detection result of the failure Failure detection unit of the
A control unit that brings the first connection terminal and the second connection terminal into a conduction state by switching on and off the first switching element and the second switching element based on the detection signal;
Equipped with
The failure mode of the first switching element and the second switching element is a short circuit failure,
Each of the first switching element and the second switching element is
A first electrode,
A second electrode,
A semiconductor chip provided between the first electrode and the second electrode;
A case for holding the first electrode, the second electrode, and the semiconductor chip;
Including
When at least one of the first switching element and the second switching element has a short circuit failure, the current square product of the current flowing in the at least one of the first switching element and the second switching element is equal to or less than the energy resistance of the case. Power converter that is . The transformer further includes a primary winding connected to the power supply, and a plurality of secondary windings magnetically coupled to the primary winding,
The input power is alternating current power,
Each of the plurality of transducers is
It is connected in parallel to the charge storage element, and is connected to the secondary winding of the transformer, converts alternating current power supplied from the secondary winding into rectified power, and converts the rectified power into the charge A rectifier circuit for supplying the storage element;
A third switching element including a pair of main terminals and a control terminal;
A fourth switching element including a pair of main terminals and a control terminal, and connected in series to the third switching element;
Further,
The third switching element and the fourth switching element are connected in parallel to the first switching element and the second switching element,
The second connection terminal is connected between the third switching element and the fourth switching element, and is a main terminal connected to the second switching element of the first switching element via the third switching element The power conversion device according to claim 1 , wherein the power conversion device is connected to a main terminal on the opposite side of The inverter circuit is
A pair of input terminals connected to the power supply;
A first arm connected to one of the input terminals;
A second arm connected between the first arm and the other of the input terminals;
A third arm connected to the one of the input terminals;
A fourth arm connected between the third arm and the other of the input terminals;
A plurality of the converter units provided on each of the first arm unit, the second arm unit, the third arm unit, and the fourth arm unit;
The power converter according to claim 1 , comprising An inverter circuit connected to a power source and an AC load, which converts input power input from the power source into AC output power different from the input power and supplying the output power to the AC load, comprising a plurality of inverter circuits The converter includes a converter unit connected in series, and each of the plurality of converters includes a first switching element including a pair of main terminals and a control terminal, a pair of main terminals and a control terminal. A second switching element connected in series to the first switching element, a charge storage element connected in parallel to the first switching element and the second switching element, and the first switching element A first connection terminal connected to the second switching element, and a main terminal on the opposite side to a main terminal connected to the second switching element of the first switching element An inverter circuit including a second connection terminal connected to the child, and
A control signal for controlling on / off of the first switching element and the second switching element is generated for each of the plurality of converters, and the control signal is input to each of the plurality of converters. A control panel for controlling the conversion of power by the inverter circuit;
A control method of a power converter including:
The failure mode of the first switching element and the second switching element is a short circuit failure,
Each of the first switching element and the second switching element is
A first electrode,
A second electrode,
A semiconductor chip provided between the first electrode and the second electrode;
A case for holding the first electrode, the second electrode, and the semiconductor chip;
Including
When at least one of the first switching element and the second switching element has a short circuit failure, the current square product of the current flowing in the at least one of the first switching element and the second switching element is equal to or less than the energy resistance of the case. And
Detecting a failure of the first switching element and the second switching element of each of the plurality of converters;
A step of making the first connection terminal and the second connection terminal conductive by switching on / off the first switching element and the second switching element when the failure is detected;
Control method of a power converter provided with

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