Power conversion device

Abstract

To provide a power conversion device which can supply power to a drive circuit with a simpler configuration while suppressing restriction in switching operation.SOLUTION: A power conversion device includes: a plurality of switching elements; a plurality of drive circuits which is provided correspondingly to the plurality of switching elements, drives the plurality of switching elements and converts power by switching of the plurality of switching elements; and a plurality of feeder circuits which is provided correspondingly to the plurality of drive circuits, generates drive power supply for operating the drive circuits and supplies the generated drive power supply to the corresponding drive circuits. Each of the switching elements includes a pair of main terminals and a control terminal. Each of the feeder circuits is provided in parallel with a pair of main terminals of each of the switching elements, and generates drive power supply with power between the pair of main terminals as power supply.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a power conversion device.

Background Art

[0002] There is a power conversion device including a plurality of switching elements and a drive circuit that drives the plurality of switching elements, and performs power conversion by switching the plurality of switching elements. The drive circuit operates by receiving power supply from a dedicated power source.

[0003] For example, in a drive circuit of a high-voltage power conversion device that handles a high voltage such as several hundred volts or more, the potential on the output side of the drive circuit fluctuates by several hundred volts each time switching occurs, and the potential on the output side of the drive circuit becomes a high potential compared to the control power source equivalent to the ground potential that is the power source of the drive circuit. Therefore, in the power source of the drive circuit, power is supplied to the drive circuit in a state insulated from the output side of the drive circuit via a transformer or the like. In this case, a transformer or the like is required, and the device becomes large-sized.

[0004] Also, it has been proposed to adopt main circuit power supply that obtains power from the DC circuit side of the power conversion device. Also in this case, since power is supplied with insulation using a flyback transformer, a high-voltage transformer is required. Also, a high-voltage switching element is required for the power supply circuit.

[0005] Furthermore, as a method that does not use a transformer, a method using a bootstrap circuit has also been proposed. However, in this case, there is a possibility that restrictions will occur in the switching operation. For example, in the method using a bootstrap circuit, power can be supplied to the drive circuit only when the opposing arm is on. Therefore, when applying a negative bias to the switching element to turn it off, there is a possibility that the upper and lower arms cannot be turned off simultaneously.

[0006] Therefore, in a power conversion device, it is desirable to be able to supply power to a drive circuit with a simpler configuration while suppressing the occurrence of constraints in the switching operation.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] Embodiments of the present invention provide a power conversion device that can supply power to a drive circuit with a simpler configuration while suppressing the occurrence of constraints in the switching operation.

Means for Solving the Problems

[0009] According to an embodiment of the present invention, each having a control terminal and a pair of main terminals a plurality of switching elements, a plurality of drive circuits provided corresponding to each of the plurality of switching elements, driving the plurality of switching elements, and performing power conversion by switching the plurality of switching elements, and a plurality of power supply circuits provided corresponding to each of the plurality of drive circuits, generating a drive power supply for operating the drive circuit, and supplying the generated drive power supply to the corresponding drive circuit, a control device that generates a plurality of drive signals for driving the plurality of switching elements, and controls power conversion by switching of the plurality of switching elements by inputting the generated plurality of drive signals to the plurality of drive circuits; are provided , the each of the plurality of power supply circuits is the is provided in parallel with respect to the pair of main terminals of each of the plurality of switching elements while , a step-down circuit that steps down the voltage between the pair of main terminals of the switching element to a predetermined voltage for generating the drive power supply, and a charge storage element that stores charges by being charged by the voltage after being stepped down by the step-down circuit, generates the drive power supply based on the charges stored in the charge storage element, and the control device temporarily turns off the switching element at a predetermined timing before the voltage of the charge storage element of the power supply circuit becomes lower than a predetermined voltage when the on state of any one of the plurality of switching elements continues. a power conversion device is provided.

Effects of the Invention

[0010] A power conversion device is provided that can supply power to a drive circuit with a simpler configuration while suppressing constraints on the switching operation.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

[0012] Hereinafter, each embodiment will be described with reference to the drawings. Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes between parts, etc. are not necessarily the same as the actual ones. Also, even when representing the same part, the dimensions and ratios may be represented differently in the drawings. In the present specification and each figure, the same reference numerals are given to the same elements as those described above with respect to the previously shown figures, and detailed descriptions are omitted as appropriate.

[0013] FIG. 1 is a block diagram schematically showing a power conversion device according to an embodiment. As shown in FIG. 1, the power conversion device 10 includes a plurality of switching elements 12, a plurality of drive circuits 14, a plurality of power supply circuits 16, and a control device 18.

[0014] The power conversion device 10 performs power conversion by switching a plurality of switching elements 12. The plurality of switching elements 12 are, for example, bridge-connected. The plurality of switching elements 12 include an upper-arm switching element 12 and a lower-arm switching element 12.

[0015] The plurality of switching elements 12 are self-excited switching elements such as MOSFETs or IGBTs, for example. The plurality of switching elements 12 have a pair of main terminals 12a, 12b and a control terminal 12c. The main terminal 12a is, for example, a drain. The main terminal 12b is, for example, a source. The control terminal 12c is, for example, a gate.

[0016] The plurality of drive circuits 14 are provided corresponding to each of the plurality of switching elements 12. The plurality of drive circuits 14 receive an input of a drive signal from the control device 18 and drive the plurality of switching elements 12 based on the input drive signal.

[0017] In other words, the plurality of drive circuits 14 switch between the on state and the off state of the switching element 12 based on the drive signal. In other words, the plurality of drive circuits 14 drive the power conversion by the power conversion device 10 based on the drive signal. The power conversion device 10 switches between the on state and the off state of the plurality of switching elements 12 by driving the plurality of drive circuits 14 and performs power conversion.

[0018] The control device 18 generates a plurality of drive signals for driving the plurality of switching elements 12 based on, for example, command values input from a higher-level controller or the like, and inputs the generated plurality of drive signals to the plurality of drive circuits 14, thereby controlling the power conversion by the switching of the plurality of switching elements 12.

[0019] The power conversion device 10 is a power conversion device having a multi-series configuration in which two switching elements 12 are connected in series to one arm. In FIG. 1, only two switching elements 12 constituting the upper arm of one leg of the power conversion device 10, two switching elements 12 constituting the lower arm, and four drive circuits 14 corresponding to each switching element 12 are shown for convenience.

[0020] The power conversion device 10 is, for example, a two-level three-phase inverter in which 12 switching elements 12 are connected in a three-phase bridge. In the power conversion device 10, the connection point between the switching element 12 of the upper arm and the switching element 12 of the lower arm becomes an AC connection point. Also, in the power conversion device 10, both ends of each switching element 12 of one leg become DC connection points. The power conversion device 10 is connected to an AC power system, an AC load, etc. via the AC connection point, and is connected to a DC power supply, a DC load, etc. via the DC connection point.

[0021] The power conversion device 10 performs at least one of conversions such as conversion from DC power to AC power and conversion from AC power to DC power by switching the plurality of switching elements 12.

[0022] The voltage between a pair of DC connection points of the power conversion device 10 is, for example, several thousand volts. The voltage between a pair of DC connection points is, for example, 1000 V or more. Thus, the power conversion device 10 is a high-voltage power conversion device that handles a relatively high voltage.

[0023] However, the configuration of the power conversion device 10 is not limited to this. The power conversion device 10 may be, for example, a single-phase inverter or the like. Also, the power conversion device 10 does not necessarily have to be a high-voltage power conversion device. The voltage between a pair of DC connection points may be any voltage without being limited to the above.

[0024] Also, in this example, it represents a power conversion device 10 having a multi-series configuration in which two switching elements 12 are connected in series to one arm. The number of switching elements 12 provided in one arm is not limited to two, and may be three or more. Also, the number of switching elements 12 provided in one arm may be one. The configuration of the power conversion device 10 does not necessarily have to be a multi-series configuration.

[0025] The plurality of power supply circuits 16 are provided corresponding to each of the plurality of drive circuits 14. The power supply circuit 16 generates a drive power source for operating the drive circuit 14, and supplies the generated drive power source to the corresponding drive circuit 14. The drive circuit 14 operates based on the drive power source supplied from the power supply circuit 16.

[0026] Each of the plurality of power supply circuits 16 is provided in parallel with respect to a pair of main terminals 12a and 12b of each of the plurality of switching elements 12. Thereby, the power supply circuit 16 generates a drive power source using the power between the pair of main terminals 12a and 12b of the switching element 12 as a power source.

[0027] Each power supply circuit 16 has, for example, a step-down circuit 21, a charge storage element 22, a rectifying element 23, and a voltage conversion circuit 24.

[0028] The step-down circuit 21 steps down the voltage between the pair of main terminals 12a and 12b of the switching element 12 to a predetermined voltage for generating a drive power source. The step-down circuit 21 steps down, for example, a voltage of several hundreds V between the pair of main terminals 12a and 12b of the switching element 12 to a voltage of about several tens V. The step-down circuit 21 steps down a high voltage between the pair of main terminals 12a and 12b of the switching element 12 to a relatively low voltage. The high voltage is, for example, a voltage of 100 V or more. The low voltage is, for example, a voltage of less than 100 V.

[0029] The step-down circuit 21 has, for example, a resistance element 31, a capacitor 32, and a resistance element 33.

[0030] One end of the resistance element 31 is connected to the high-potential-side main terminal 12a of the switching element 12. The other end of the resistance element 31 is connected to one end of the capacitor 32. The other end of the capacitor 32 is connected to the low-potential-side main terminal 12b of the switching element 12. In this way, the capacitor 32 is connected in series with the resistance element 31. The series connection body of the resistance element 31 and the capacitor 32 is connected in parallel with respect to the pair of main terminals 12a and 12b of the switching element 12.

[0031] One end of the resistor element 33 is connected to the connection point between the resistor element 31 and the capacitor 32. The other end of the resistor element 33 is connected to the low-potential main terminal 12b of the switching element 12. The resistor element 33 is connected in parallel with the capacitor 32.

[0032] The step-down circuit 21 steps down the voltage between the pair of main terminals 12a and 12b of the switching element 12 by voltage division by the resistor elements 31 and 33. In other words, the step-down circuit 21 is a voltage division circuit.

[0033] Also, the step-down circuit 21 functions as a voltage balance circuit for adjusting so that the voltages applied to each of the plurality of switching elements 12 provided in one arm are equal in the power conversion device 10 having a multi-series configuration. In each step-down circuit 21 of the plurality of power supply circuits 16, the resistance values of the resistor elements 31 and 33 and the capacitance value of the capacitor 32 are adjusted. Thereby, the voltages applied to each of the plurality of switching elements 12 provided in one arm can be made substantially the same.

[0034] However, the configuration of the step-down circuit 21 is not limited to the configuration by voltage division of the resistor elements 31 and 33. The configuration of the step-down circuit 21 may be any configuration capable of stepping down the voltage between the pair of main terminals 12a and 12b of the switching element 12 to a predetermined voltage for generating a drive power supply.

[0035] The charge storage element 22 is provided on the output side of the step-down circuit 21. One end of the charge storage element 22 is connected to, for example, the resistor element 33. The other end of the charge storage element 22 is connected to, for example, the low-potential main terminal 12b of the switching element 12. The charge storage element 22 stores charge by being charged by the voltage stepped down by the step-down circuit 21.

[0036] When the switching element 12 corresponding to the power supply circuit 16 is in the off state, the power between the pair of main terminals 12a and 12b of the switching element 12 is supplied to the power supply circuit 16. When the switching element 12 corresponding to the power supply circuit 16 is in the off state, the charge storage element 22 is charged based on the power between the pair of main terminals 12a and 12b of the switching element 12.

[0037] On the other hand, when the switching element 12 corresponding to the power supply circuit 16 is in the on state, since the pair of main terminals 12a and 12b of the switching element 12 are conducting, the supply of power to the power supply circuit 16 is stopped. The power supply circuit 16 charges the charge storage element 22 when the switching element 12 is in the off state, so that even when the switching element 12 is in the on state, the generation of the drive power supply can be continued based on the charge stored in the charge storage element 22.

[0038] Therefore, the magnitude of the capacitance of the charge storage element 22 is determined according to the amount of energy supplied to the drive circuit 14 required when the switching element 12 is in the on state. The magnitude of the capacitance of the charge storage element 22 is set to a magnitude that can continue to generate the drive power supply even when the switching element 12 is in the on state.

[0039] The rectifying element 23 is provided between the step-down circuit 21 and the charge storage element 22, and rectifies the flow of current in the direction from the step-down circuit 21 to the charge storage element 22. Thereby, the rectifying element 23 suppresses the charge stored in the charge storage element 22 from being discharged to the switching element 12 side when the switching element 12 becomes in the on state.

[0040] The input side of the voltage conversion circuit 24 is connected in parallel with the charge storage element 22. As a result, the voltage across both ends of the charge storage element 22 is input to the voltage conversion circuit 24. The output side of the voltage conversion circuit 24 is connected to the drive circuit 14. The voltage conversion circuit 24 generates a drive power supply for the drive circuit 14 by converting the voltage input from the charge storage element 22 into a voltage corresponding to the drive circuit 14, and supplies the generated drive power supply to the drive circuit 14. The voltage conversion circuit 24 converts the voltage of the charge storage element 22, which is, for example, several tens of volts to several hundreds of volts, into a voltage of several volts to several tens of volts. The voltage conversion circuit 24 is, for example, a step-down conversion circuit. Thereby, the drive power supply can be supplied to the drive circuit 14 using the power between the pair of main terminals 12a and 12b of the switching element 12 as a power source.

[0041] The voltage conversion circuit 24 is, for example, a DC / DC converter. The voltage conversion circuit 24 may also be a three-terminal regulator or the like. In this way, by converting the voltage of the charge storage element 22 with the voltage conversion circuit 24 to generate a drive power supply, a drive power supply with a stable voltage can be supplied to the drive circuit 14. The configuration of the voltage conversion circuit 24 is not limited to the above, and any configuration capable of supplying a drive power supply with a stable voltage to the drive circuit 14 may be used.

[0042] Note that the configuration of the power supply circuit 16 is not limited to the above. For example, when the drive circuit 14 has a function of stabilizing the input voltage, the voltage conversion circuit 24 may be omitted, and the voltage of the charge storage element 22 may be supplied to the drive circuit 14. In other words, the voltage conversion circuit 24 may be provided in the drive circuit 14. The power supply circuit 16 generates a drive power supply, for example, based on the charge stored in the charge storage element 22. The configuration of the power supply circuit 16 may be any configuration capable of generating a drive power supply for the drive circuit 14 using the power between the pair of main terminals 12a and 12b of the switching element 12 as a power source.

[0043] As described above, in the power conversion device 10 according to the present embodiment, the power supply circuit 16 generates the drive power supply of the drive circuit 14 using the power between the pair of main terminals 12a and 12b of the switching element 12 as a power source. Therefore, in the power conversion device 10 according to the present embodiment, it is not necessary to provide a high-voltage transformer, a high-voltage switching element, etc. in the power supply circuit 16, and when supplying the drive power supply to the drive circuit 14 via a transformer or the like, or when supplying the drive power supply to the drive circuit 14 by a power supply circuit using a flyback transformer, etc., the configuration of the power supply circuit 16 can be simplified. Thereby, for example, cost reduction, miniaturization, high reliability, etc. of the power conversion device 10 can be achieved.

[0044] And in the power conversion device 10 according to the present embodiment, when the switching element 12 is in the off state, the charge storage element 22 is charged, and the drive power supply of the drive circuit 14 is generated based on the charge stored in the charge storage element 22. Therefore, it is possible to suppress the occurrence of restrictions on the switching operation compared to the case of using a bootstrap circuit. For example, even when a negative bias is applied to the switching element 12 to turn it off, the upper and lower arms can be turned off simultaneously.

[0045] Therefore, it is possible to provide a power conversion device 10 that can supply power to the drive circuit 14 with a simpler configuration while suppressing the occurrence of restrictions on the switching operation.

[0046] Further, the power conversion device 10 is configured in a multi-series configuration in which a plurality of switching elements 12 are connected in series to one arm. In such a multi-series configuration power conversion device, a resistor element 31, 33 and a capacitor 32 are provided as a voltage balance circuit. In the power conversion device 10 according to the present embodiment, the step-down circuit 21 also functions as a voltage balance circuit. Thereby, an increase in the number of components in the power supply circuit 16 can be suppressed. In other words, by using the voltage balance circuit as the step-down circuit 21 (voltage dividing resistor), an increase in the number of components can be suppressed, and the power supply circuit 16 can be realized with a simpler configuration.

[0047] In the power conversion device 10, the power supply circuit 16 includes a voltage conversion circuit 24. Even in this case, the voltage input to the voltage conversion circuit 24 is a low voltage after being stepped down by the step-down circuit 21, and the voltage conversion circuit 24 can also be a low-voltage circuit. The reference potential of the voltage conversion circuit 24 is the same potential as the reference potential of the drive circuit 14 (the potential of the low-potential-side main terminal 12b), and a non-insulated type conversion circuit can be applied to the voltage conversion circuit 24. There is no need to provide a high-voltage transformer or the like in the voltage conversion circuit 24. Therefore, even if the voltage conversion circuit 24 is provided, an increase in cost, an increase in the size of the device, and a decrease in reliability due to the voltage conversion circuit 24 can be suppressed as compared with the case of providing a high-voltage circuit.

[0048] For example, when the power conversion device 10 is applied to a converter that outputs a DC output or a low-frequency output, there is a possibility that the on-state of any of the plurality of switching elements 12 may continue for a relatively long time. In such a case, the charge storage element 22 cannot be charged, and there is a possibility that the supply of the drive power supply to the drive circuit 14 may stop.

[0049] Therefore, when the on-state of any of the plurality of switching elements 12 continues in this way, the control device 18 performs control to temporarily switch the switching element 12 to the off-state at a predetermined timing before the voltage of the charge storage element 22 becomes lower than a predetermined voltage.

[0050] The predetermined voltage is, for example, the minimum operating voltage of the voltage conversion circuit 24. When the voltage of the charge storage element 22 is directly supplied to the drive circuit 14, the predetermined voltage may be the minimum operating voltage of the drive circuit 14.

[0051] The control device 18, for example, temporarily switches the switching element 12 to the off-state when the voltage of the charge storage element 22 reaches the predetermined voltage. The control device 18 may, for example, temporarily switch the switching element 12 to the off-state when a predetermined time has elapsed from the timing when the switching element 12 is switched to the on-state.

[0052] The time for temporarily turning off the switching element 12 is preferably a relatively short time that can, for example, appropriately charge the charge storage element 22 and suppress the possibility of affecting the operation of the power conversion. The control device 18, for example, returns the switching element 12 to the on state when a predetermined time has elapsed since the timing at which the switching element 12 was switched to the off state. The control device 18 may, for example, return the switching element 12 to the on state when the voltage of the charge storage element 22 becomes equal to or higher than a predetermined threshold value after the switching element 12 has been switched to the off state.

[0053] In this way, when the on state of any of the plurality of switching elements 12 continues, the control device 18 temporarily switches the switching element 12 to the off state at a predetermined timing before the voltage of the charge storage element 22 becomes lower than a predetermined voltage. Thereby, even when the on state of the switching element 12 continues, it is possible to suppress the charge storage element 22 from not being charged and the supply of the drive power source to the drive circuit 14 from stopping.

[0054] FIG. 2 is a block diagram schematically showing a modification of the power conversion device according to the embodiment. As shown in FIG. 2, the power conversion device 10a further includes a pair of charge storage elements 51 and 52, and a pair of rectifying elements 53 and 54. Note that components that are substantially the same in function and configuration as those in the above embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0055] One end of the charge storage element 51 is connected to the DC connection point on the high potential side. The other end of the charge storage element 51 is connected to one end of the charge storage element 52. The other end of the charge storage element 52 is connected to the DC connection point on the low potential side.

[0056] One end of the rectifying element 53 is connected to the series connection point of the two switching elements 12 of the upper arm. The other end of the rectifying element 53 is connected to one end of the rectifying element 54. The other end of the rectifying element 54 is connected to the series connection point of the two switching elements 12 of the lower arm. Also, the series connection point of the rectifying elements 53 and 54 is connected to the series connection point of the charge storage elements 51 and 52.

[0057] The power conversion device 10a is a neutral point clamped type three-level inverter. The plurality of switching elements 12 are switching elements that constitute a neutral point clamped type three-level inverter. Also in the power conversion device 10a of the three-level inverter, the power supply circuit 16 generates the drive power supply of the drive circuit 14 using the power between the pair of main terminals 12a and 12b of the switching element 12 as a power source, so that, similar to the above-described embodiment, while suppressing the occurrence of restrictions in the switching operation, the drive circuit 14 can be supplied with power with a simpler configuration.

[0058] In the power conversion device 10a, when the switching element 12 on the neutral point side among the two switching elements 12 of the upper arm is the switching element U1 and the switching element 12 on the DC connection point side is the switching element U2, and the switching element 12 on the neutral point side among the two switching elements 12 of the lower arm is the switching element X1 and the switching element 12 on the DC connection point side is the switching element X2, the on-time of the switching elements U1 and X1 on the neutral point side tends to be longer than the on-time of the switching elements U2 and X2 on the DC connection point side.

[0059] In such a case, it is preferable to make the capacitance of the charge storage element 22 of the power supply circuit 16 corresponding to the switching elements U1 and X1 on the neutral point side larger than the capacitance of the charge storage element 22 of the power supply circuit 16 corresponding to the switching elements U2 and X2 on the DC connection point side.

[0060] As a result, even when the on-time of the switching elements U1 and X1 on the neutral point side is longer than the on-time of the switching elements U2 and X2 on the DC connection point side, the voltage of the charge storage element 22 can be prevented from decreasing, and the supply of the drive power source to the drive circuit 14 corresponding to the switching elements U1 and X1 on the neutral point side can be suppressed from stopping.

[0061] Thus, the power conversion device according to the present embodiment may be, for example, a multilevel inverter such as a three-level inverter. The power conversion device according to the present embodiment may be applied to each converter of a power conversion device having a multi-stage configuration in which a plurality of converters (unit cells) are connected in series, such as an MMC (Modular Multilevel Converter) type power conversion device.

[0062] The configuration of the power conversion device may be any configuration that performs power conversion by switching a plurality of switching elements 12. The power conversion by the power conversion device may be, for example, conversion from AC power to another AC power having a different voltage or frequency, or conversion from DC power to another DC power having a different voltage. The power conversion by the power conversion device may be any conversion to another power.

[0063] The present embodiment includes the following aspects. (Appendix 1) A plurality of switching elements, A plurality of drive circuits provided corresponding to each of the plurality of switching elements, driving the plurality of switching elements, and performing power conversion by switching the plurality of switching elements, A plurality of power supply circuits provided corresponding to each of the plurality of drive circuits, generating a drive power source for operating the drive circuit, and supplying the generated drive power source to the corresponding drive circuit, Comprising, The plurality of switching elements have a pair of main terminals and a control terminal, Each of the plurality of power supply circuits is provided in parallel with respect to the pair of main terminals of each of the plurality of switching elements, and is a power conversion device that generates the drive power supply using the power between the pair of main terminals as a power source. (Appendix 2) Each of the plurality of power supply circuits a step-down circuit that steps down the voltage between the pair of main terminals of the switching element to a predetermined voltage for generating the drive power supply; a charge storage element that accumulates charges by being charged by the voltage stepped down by the step-down circuit; The power conversion device according to Appendix 1, which has and generates the drive power supply based on the charges accumulated in the charge storage element. (Appendix 3) Each of the plurality of power supply circuits is provided between the step-down circuit and the charge storage element, and rectifies the flow of current in the direction from the step-down circuit toward the charge storage element, so that when the corresponding switching element is in the on state, the charges accumulated in the charge storage element are prevented from being discharged to the corresponding switching element side. The power conversion device according to Appendix 2, further comprising a rectifying element. (Appendix 4) The step-down circuit has a resistance element, and the power conversion device according to Appendix 2 or 3, which steps down the voltage between the pair of main terminals of the switching element by voltage division by the resistance element. (Appendix 5) The plurality of switching elements include an upper-arm switching element and a lower-arm switching element, and are configured in a multi-series configuration in which a plurality of the switching elements are connected in series to one arm. The power conversion device according to Appendix 4, wherein the step-down circuit also functions as a voltage balance circuit for adjusting so that the voltages applied to each of the plurality of switching elements provided in one arm become equal. (Appendix 6) A control device is further provided for generating a plurality of drive signals for driving the plurality of switching elements, and controlling power conversion by switching of the plurality of switching elements by inputting the generated plurality of drive signals into the plurality of drive circuits. The control device performs control to temporarily turn off the switching element at a predetermined timing before the voltage of the charge storage element of the power supply circuit becomes lower than a predetermined voltage when the on-state of any one of the plurality of switching elements continues. The power conversion device according to any one of Supplementary Notes 2 to 5. (Supplementary Note 7) The plurality of switching elements are switching elements constituting a neutral point clamped three-level inverter. The capacitance of the charge storage element of the power supply circuit corresponding to the switching element on the neutral point side is larger than the capacitance of the charge storage element of the power supply circuit corresponding to the switching element on the DC connection point side. The power conversion device according to any one of Supplementary Notes 2 to 6.

[0064] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0065] 10, 10a... Power conversion device, 12... Switching element, 14... Drive circuit, 16... Power supply circuit, 18... Control device, 21... Step-down circuit, 22... Charge storage element, 23... Rectifying element, 24... Voltage conversion circuit, 31... Resistance element, 32... Capacitor, 33... Resistance element, 51, 52... Charge storage elements, 53, 54... Rectifying elements

Claims

Claim 1. A plurality of switching elements each having a control terminal and a pair of main terminals, a plurality of drive circuits provided corresponding to each of the plurality of switching elements, driving the plurality of switching elements, and performing power conversion by switching the plurality of switching elements; a plurality of power supply circuits provided corresponding to each of the plurality of drive circuits, generating a drive power supply for operating the drive circuit, and supplying the generated drive power supply to the corresponding drive circuit; a control device that generates a plurality of drive signals for driving the plurality of switching elements, and controls power conversion by switching of the plurality of switching elements by inputting the generated plurality of drive signals to the plurality of drive circuits; comprising: each of the plurality of power supply circuits is provided in parallel with the pair of main terminals of each of the plurality of switching elements, and has a step-down circuit that steps down the voltage between the pair of main terminals of the switching element to a predetermined voltage for generating the drive power supply, and a charge storage element that accumulates charges by being charged by the voltage stepped down by the step-down circuit, and generates the drive power supply based on the charges accumulated in the charge storage element; the control device performs control to temporarily switch the switching element to an off state at a predetermined timing before the voltage of the charge storage element of the power supply circuit becomes lower than a predetermined voltage when the on state of any one of the plurality of switching elements continues. A power conversion device. Claim 2. Each of the plurality of power supply circuits is provided between the step-down circuit and the charge storage element, and rectifies the flow of current in the direction from the step-down circuit toward the charge storage element, so that when the corresponding switching element is in the on state, The power conversion device according to claim 1, further comprising a rectifying element that suppresses the charge accumulated in the charge storage element from being discharged to the corresponding switching element side. Claim 3. The step-down circuit has a resistance element, and the power conversion device according to claim 1 or 2, wherein the voltage between the pair of main terminals of the switching element is stepped down by voltage division by the resistance element. Claim 4. The plurality of switching elements include an upper-arm switching element and a lower-arm switching element, and are configured in a multi-series configuration in which a plurality of the switching elements are connected in series to one arm. The power conversion device according to claim 3, wherein the step-down circuit also functions as a voltage balance circuit for adjusting so that voltages applied to respective ones of the plurality of switching elements provided in one arm become equal.

5. The plurality of switching elements are switching elements that constitute a neutral-point clamped three-level inverter. The power conversion device according to claim 1, wherein a capacitance of the charge storage element of the power supply circuit corresponding to the switching element on the neutral point side is larger than a capacitance of the charge storage element of the power supply circuit corresponding to the switching element on the DC connection point side.

Images