Power conversion device

Abstract

To provide a power conversion device in which even when a power source voltage is lowered, occurrence of a surge voltage caused by electric energy stored in the power conversion device can be suppressed.SOLUTION: A power conversion device 51 includes a rectification circuit 11, a capacitor 15 electrically connected in parallel with the rectification circuit 11, a reactor 12 electrically connected in series with the rectification circuit 11 and the capacitor 15, a switching circuit 13 that has a plurality of switching elements SW1 to SW4 and is electrically connected with the rectification circuit 11 via the reactor 12, drive circuits GD1 to GD4 for the plurality of switching elements SW1 to SW4, a drive control unit 40 that generates control signals for controlling the drive circuits GD1 to GD4 and outputs the control signals to the drive circuits GD1 to GD4, and a drive source generation unit 20 that is electrically connected in parallel with the rectification circuit 11 and the capacitor 15 and supplies power supplied from the rectification circuit 11 or the capacitor 15 to the drive circuits GD1 to GD4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power conversion device that controls power supplied from a power source to a load. [Background technology]

[0002] There is known a power conversion device that controls power supplied from a power source to a load. As an example of such a power conversion device, as disclosed in Patent Document 1, a power supply system that supplies power to a moving object that runs while supported on a track is known.

[0003] The power supply system disclosed in Patent Document 1 includes a capacitor connected to a power feeder line, a switch circuit having a switch element that selectively takes an ON state in which a reactor is connected in parallel to the power feeder line and an OFF state in which the reactor is not electrically connected to the power feeder line, and a switch control unit that switches the state of the switch element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-201211 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a power conversion device such as the power supply system described in Patent Document 1, a switch control unit may be operated by power supplied from an external AC power source. Such a switch control unit includes, for example, a drive control unit that generates a control signal for controlling the drive of a switch element (switching element), and a drive circuit that switches the switching element between an on state and an off state.

[0006] When power is supplied to the drive circuit from an external AC power source or the like, if the voltage of the power source (hereinafter referred to as the power source voltage) drops due to a power outage or a failure of a power conversion device, the power supplied to the drive circuit also drops. Therefore, when the power source voltage falls below a predetermined value, the drive circuit cannot be supplied with sufficient power to drive a switching circuit. Therefore, when the power source voltage drops and the power supplied to the drive circuit drops, for example, the switching element remains in the off state.

[0007] Meanwhile, in the circuit of a power conversion device such as the power supply system described in Patent Document 1, electrical energy is stored in elements such as reactors. Therefore, when the power supplied to the drive circuit is reduced and the switching element is turned off as described above, the electrical energy stored in the circuit of the power conversion device is not consumed, and a surge voltage may occur in the circuit of the power conversion device. When the surge voltage occurs, the switching element in the circuit of the power conversion device may be damaged.

[0008] An object of the present invention is to provide a power conversion device capable of suppressing the occurrence of a surge voltage due to electrical energy stored in the power conversion device even when the power supply voltage drops. [Means for solving the problem]

[0009] A power conversion device according to an embodiment of the present invention is a power conversion device that controls power supplied from a power source to a load. The power conversion device includes a rectifier circuit that rectifies an AC current output from the power source, a capacitor electrically connected in parallel to the rectifier circuit, a reactor electrically connected in series to the rectifier circuit and the capacitor, a switching circuit having a plurality of switching elements, electrically connected to the rectifier circuit via the reactor, and supplying power from the rectifier circuit to the load by switching the on-state or off-state of the plurality of switching elements, a drive circuit that switches the on-state or off-state of the plurality of switching elements, a drive control unit that generates a control signal that controls the drive circuit to switch the on-state or off-state of the plurality of switching elements and outputs it to the drive circuit, and a drive power generation unit that is electrically connected in parallel to the rectifier circuit and the capacitor, and supplies the power supplied from the rectifier circuit or the capacitor to the drive circuit (first configuration).

[0010] In the above-mentioned configuration, the drive power supply generating unit supplies the power supplied from the rectifier circuit or the capacitor to the drive circuit. Therefore, even if the power supply voltage drops, the drive circuit can be driven using the power remaining in the circuit of the power conversion device. Therefore, even if the power supply voltage drops, the drive circuit can drive the switching element to pass a current through the circuit of the power conversion device, thereby consuming the electrical energy stored in the power conversion device.

[0011] Therefore, according to the above-mentioned configuration, even if the power supply voltage drops, the driving circuit can drive the switching element, thereby making it possible to consume electrical energy stored in the circuit of the power conversion device and to suppress the occurrence of surge voltage.

[0012] In the first configuration, when the voltage input from the drive power generation unit to the drive circuit drops and reaches a first threshold, the drive control unit generates a control signal to control the drive circuit so that the electrical energy remaining in the reactor is consumed by the switching circuit, and outputs the control signal to the drive circuit (second configuration).

[0013] According to the above-mentioned configuration, even if the voltage input from the drive power supply generating unit to the drive circuit drops and reaches the first threshold, the drive circuit can be controlled so that the electrical energy remaining in the reactor is consumed by the switching circuit, thereby more reliably suppressing the occurrence of surge voltage in the power conversion device.

[0014] In the first configuration, the inverter further includes a control power supply generating unit that supplies the power output from the power supply to the drive control unit, and when the voltage input from the control power supply generating unit to the drive control unit drops and reaches a second threshold, the drive control unit generates a control signal that controls the drive circuit so that the electrical energy remaining in the reactor is consumed by the switching circuit, and outputs the control signal to the drive circuit (third configuration).

[0015] According to the above-mentioned configuration, even if the voltage input from the control power supply generating unit to the drive control unit drops and reaches the second threshold, the drive circuit can be controlled so that the electrical energy remaining in the reactor is consumed by the switching circuit, thereby more reliably suppressing the occurrence of surge voltage in the power conversion device.

[0016] In any one of the first to third configurations, the power supply includes a plurality of power conversion units that include the rectifier circuit, the capacitor, the switching circuit, the drive circuit, and the drive power supply generation unit and control the power supplied from the power supply to the load, the plurality of power conversion units are electrically connected in parallel to each other, and the drive control unit generates a control signal that controls the drive circuit included in at least one of the plurality of power conversion units and outputs it to the drive circuit (fourth configuration).

[0017] According to the above configuration, even if a drop in the power supply voltage occurs in a power conversion device having a plurality of power conversion units, the generation of a surge voltage in the plurality of power conversion units can be suppressed. Effect of the Invention

[0018] A power conversion device according to one embodiment of the present invention includes a drive circuit that switches between the on and off states of a plurality of switching elements, and a drive power generation unit that supplies to the drive circuit either power output from a rectifier circuit that rectifies an AC current output from a power source, or power supplied from a capacitor electrically connected in parallel to the rectifier circuit.

[0019] As a result, even if the power supply voltage drops, the switching element continues to be driven, thereby consuming the electrical energy stored in the circuit of the power conversion device, thereby obtaining a power conversion device capable of suppressing the occurrence of surge voltage. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram illustrating an example of a power supply system including a power conversion device according to a first embodiment and a load. [Diagram 2] FIG. 2 is a diagram illustrating an example of a power supply system including a power conversion device according to the second embodiment. [Diagram 3] FIG. 3 is a diagram illustrating an example of a conventional power conversion device. [Figure 4] FIG. 4 is a diagram showing an example of changes over time in the internal current, the drive power supply voltage, and the control power supply voltage when the voltage of the input power supply drops in the power conversion device according to the second embodiment and in a conventional power conversion device. [Diagram 5] FIG. 5 is a diagram illustrating an example of a power supply system including a power conversion device according to the third embodiment. [Figure 6]FIG. 6 is a diagram showing an example of changes over time in the internal current, the drive power supply voltage, and the control power supply voltage when the voltage of the input power supply drops in the power conversion device according to the third embodiment and in a conventional power conversion device. [Figure 7] FIG. 7 is a diagram illustrating an example of a power supply system including a power conversion device according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and the description thereof will not be repeated.

[0022] <Embodiment 1> 1 is a diagram showing a schematic configuration of a power supply system 1 having a power conversion device 51 and a load 70 according to a first embodiment of the present invention. The power conversion device 51 controls the power supplied from an input power source 60 (power source) to the load 70. The load 70 includes, for example, a track circuit 71 that supplies power to a moving object traveling along a track.

[0023] The power conversion device 51 is electrically connected to a primary side of a transformer 73, while the load 70 is electrically connected to a secondary side of the transformer 73. The power conversion device 51 supplies power to the load 70 via the transformer 73.

[0024] The power conversion device 51 includes a power conversion unit 10, a control power supply generation unit 30, and a drive control unit .

[0025] The power conversion unit 10 includes a rectifier circuit 11, a reactor 12, a chopper switching element SW10, a switching circuit 13, a capacitor 14, a diode 15, drive circuits GD1 to GD4, and a drive power supply generation unit 20.

[0026] The rectifier circuit 11 is electrically connected to the input power source 60. The rectifier circuit 11 rectifies a three-phase AC current output from the input power source 60. The rectifier circuit 11 can be realized, for example, by a plurality of diodes constituting a full-wave rectifier circuit. The rectifier circuit 11 may also be realized by a half-wave rectifier circuit.

[0027] The reactor 12 is electrically connected in series to the rectifier circuit 11 and a capacitor 14 described later. The reactor 12 is also electrically connected in series to the rectifier circuit 11 via a chopper switching element SW10 described later. That is, the reactor 12 is located between the rectifier circuit 11 and a switching circuit 13 described later. The reactor 12 stores electrical energy therein and supplies a constant current to the switching circuit 13.

[0028] The chopper switching element SW10 is located between the reactor 12 and a capacitor 14 described below. The chopper switching element SW10 controls the current supplied to the reactor 12. That is, when the chopper switching element SW10 is in an on state, a current flows from the rectifier circuit 11 or the capacitor 14 to the reactor 12, whereas when the chopper switching element SW10 is in an off state, no current flows from the rectifier circuit 11 or the capacitor 14 to the reactor 12. Although not particularly shown, the chopper switching element SW10 is driven and controlled by a chopper drive circuit.

[0029] The chopper switching element SW10 may be an IGBT (Insulated Gate Bipolar Transistor), a power semiconductor device having another configuration, or a switching element of another configuration as long as it has a configuration capable of interrupting the flow of current.

[0030] The switching circuit 13 is electrically connected to the rectifier circuit 11 via the reactor 12. The switching circuit 13 functions as a current source inverter that converts the current supplied from the rectifier circuit 11 via the reactor 12 into an AC current of a predetermined frequency and outputs the AC current to the load 70. The switching circuit 13 is electrically connected to the output side of the reactor 12. The switching circuit 13 has four switching elements SW1 to SW4 and four diodes D1 to D4. The switching circuit 13 supplies power from the rectifier circuit 11 to the load 70 by switching the multiple switching elements SW1 to SW4 between an on state and an off state.

[0031] Each switching element and each diode are electrically connected in series. The switching elements SW1 and SW2 are electrically connected in series. The switching elements SW3 and SW4 are electrically connected in series. The switching elements SW1 and SW2 electrically connected in series and the switching elements SW3 and SW4 electrically connected in series form a bridge circuit. That is, the midpoint of the switching elements SW1 and SW2 and the midpoint of the switching elements SW3 and SW4 are each electrically connected to the primary side of the transformer 73.

[0032] The switching elements SW1 to SW4 may be IGBTs or power semiconductor devices having other configurations.

[0033] The capacitor 14 is electrically connected in parallel to the rectifier circuit 11 between the rectifier circuit 11 and the switching circuit 13. The capacitor 14 can smooth the current rectified by the rectifier circuit 11.

[0034] The diode 15 is electrically connected to the switching circuit 13 via the reactor 12. Specifically, the anode of the diode 15 is electrically connected to the cathodes of the diodes D2 and D4 of the switching circuit 13, and the cathode of the diode 15 is electrically connected between the reactor 12 and the chopper switching element SW10. As a result, when the chopper switching element SW10 is switched from the on state to the off state, a reflux current from the switching circuit 13 flows through the diode 15.

[0035] The four drive circuits GD1-GD4 respectively switch the four switching elements SW1-SW4 in the switching circuit 13 to an ON or OFF state in response to a control signal output from a drive control unit 40 described below. That is, the four drive circuits GD1-GD4 are gate drivers that drive the gates of the four switching elements SW1-SW4. In Fig. 1, the drive circuits GD1-GD4 are drawn as separate blocks for convenience, but may be mounted on one or more substrates.

[0036] The drive power supply generating unit 20 is electrically connected in parallel to the rectifier circuit 11 and the capacitor 14. The drive power supply generating unit 20 transforms the power supplied from the rectifier circuit 11 or the capacitor 14 by DC / DC conversion, and supplies the transformed power to the drive circuits GD1 to GD4.

[0037] The control power supply generating unit 30 transforms AC power supplied from an input power supply 60 by AC / DC conversion and supplies the transformed power to the drive control unit 40 .

[0038] The drive control unit 40 generates control signals for controlling the drive circuits GD1-GD4 so as to switch the four switching elements SW1-SW4 in a switching circuit 13 (described later) between an on state and an off state, and outputs the control signals to the drive circuits GD1-GD4.

[0039] In the above-mentioned configuration, the driving power supply generating unit 20, which supplies power for driving the driving circuits GD1 to GD4, supplies the power supplied from the rectifier circuit 11 or the capacitor 14 to the driving circuits GD1 to GD4. Therefore, even if the power supply voltage drops, the driving circuits GD1 to GD4 can be driven using the power remaining in the circuit of the power conversion device 51. For example, the driving power supply generating unit 20 can supply power to the driving circuits GD1 to GD4 using the power stored in the capacitor 14 of the power conversion device 51. Therefore, even if the power supply voltage drops, the switching elements SW1 to SW4 are driven by the driving circuits GD1 to GD4 to flow a current in the circuit of the power conversion device 51, thereby consuming the electrical energy stored in the power conversion device 51.

[0040] Therefore, according to the above-mentioned configuration, even if the power supply voltage drops, it is possible to prevent the drive circuits GD1-GD4 from stopping the drive of the switching elements SW1-SW4. This makes it possible to consume the electrical energy stored in the circuit of the power conversion device 51, and to prevent the occurrence of a surge voltage in the power conversion device 51.

[0041] <Embodiment 2> 2 is a diagram showing a schematic configuration of a power supply system 2 including a power conversion device 52 according to embodiment 2. The power conversion device 52 according to embodiment 2 differs from the power conversion device 51 according to embodiment 1 in that the power conversion device 52 according to embodiment 2 performs a stop process in response to a drop in the drive power supply voltage VGDout. In the following, the same components as those in embodiment 1 are denoted by the same reference numerals and their description is omitted, and only the parts different from embodiment 1 will be described.

[0042] (Overall composition) The power conversion device 52 includes a power conversion unit 110 and a drive control unit 240. The power conversion unit 110 includes a current detection unit 16 between the reactor 12 and the switching circuit 13 that detects a current (hereinafter, referred to as an internal current) flowing from the reactor 12 to the switching circuit 13.

[0043] The drive control unit 240 includes a control voltage detection unit 42 , a drive voltage detection unit 43 , and a control signal generation unit 44 .

[0044] The control voltage detector 42 detects the control power supply voltage VGCout, which is the output voltage of the control power supply generator 30 .

[0045] The drive voltage detection unit 43 detects a drive power supply voltage VGDout which is an output voltage of the drive power supply generation unit 20. When the power conversion unit 110 has a voltage detection unit which detects the voltage between the drive power supply generation unit 20 and the drive circuits GD1 to GD4 as the drive power supply voltage VGDout, the drive voltage detection unit 43 may acquire the value of the drive power supply voltage VGDout detected by the voltage detection unit.

[0046] The control signal generating unit 44 controls the stop process using the switching elements SW1 to SW4 in response to a drop in the drive power supply voltage VGDout caused by a voltage drop in the input power supply 60. The control signal generating unit 44 generates a control signal for controlling the stop process, and outputs the generated control signal to the drive circuits GD1 to GD4. As a result, in the stop process, the control signal generating unit 44 controls the switching of the switching elements SW1 to SW4 by the drive circuits GD1 to GD4. The stop process will be described in detail later.

[0047] 3 shows a schematic configuration of a power conversion device 952, which is an example of a conventional power conversion device. The power conversion device 952 has a power conversion section 910, a drive power generation section 920, a control power generation section 30, and a drive control section 940. The drive power generation section 920 converts the voltage of the input power supply 60 from AC to DC and supplies the converted voltage to the drive circuits GD1 to GD4. The drive control section 940 generates control signals for controlling the drive circuits GD1 to GD4 so as to switch the switching elements SW1 to SW4 of the power conversion section 910 between the on state and the off state, and outputs the control signals to the drive circuits GD1 to GD4.

[0048] Fig. 4 shows changes over time of the internal current Isw, the drive power supply voltage VGDout, and the control power supply voltage VGCout when the voltage of the input power supply 60 drops in the power conversion device 52 according to the second embodiment and the conventional power conversion device 952. In Fig. 4, the change over time of the internal current Isw flowing through the circuit of the power conversion unit 110 of the power conversion device 52 according to the second embodiment is shown by a solid line. Also in Fig. 4, the change over time of the internal current Isw flowing through the circuit of the power conversion unit 910 of the conventional power conversion device 952 is shown by a dashed dotted line.

[0049] In a normal operation state, as shown in Fig. 4, an internal current Isw flowing through a circuit of a power conversion unit 910 of a conventional power conversion device 952 is I1. In addition, in the normal operation state, a drive power supply voltage VGDout output by the drive power supply generation unit 920 is V11, and a control power supply voltage VGCout output by the control power supply generation unit 30 is V21.

[0050] After time t1, when the internal current Isw continues to decrease, the drive power supply voltage VGDout and the control power supply voltage VGCout also decrease accordingly. Due to these voltage decreases, for example, the drive power supply voltage VGDout reaches the drive-disabled voltage V12 at time t4, which is a voltage at which the drive power supply generation unit 920 cannot generate power to supply to the drive circuits GD1-GD4 (P91 shown in FIG. 4). On the other hand, the control power supply voltage VGCout at time t4 is higher than the control-disabled voltage V22 at which the control power supply generation unit 30 cannot output control signals to the drive circuits GD1-GD4 (P92 shown in FIG. 4). That is, in the example shown in FIG. 4, the drive power supply voltage VGDout reaches the drive-disabled voltage V12 earlier than the control power supply voltage VGCout reaches the control-disabled voltage V22.

[0051] When the drive power supply voltage VGDout reaches the drive-disabling voltage V12, the drive circuits GD1-GD4 are unable to drive the switching elements SW1-SW4 in the ON state. This causes the switching elements SW1-SW4 to turn OFF, and the internal current Isw flowing through the circuit of the power conversion unit 910 becomes zero (P93 shown in FIG. 4). When the switching elements SW1-SW4 turn OFF, a surge voltage is generated by electrical energy stored in the circuit of the power conversion unit 910 of the power conversion device 952. This may damage, for example, the switching elements SW1-SW4.

[0052] In response to this, the power conversion device 52 according to the second embodiment performs the following stop process in order to suppress the occurrence of the above-mentioned surge voltage.

[0053] (Stop processing) 4 again, the stop processing in the drive control unit 240 of the power conversion device 52 according to the second embodiment will be described. The stop processing is processing for consuming electrical energy stored in the circuit of the power conversion unit 110 of the power conversion device 52 in response to a drop in the drive power supply voltage VGDout.

[0054] The control signal generating unit 44 of the drive control unit 240 determines whether the drive power supply voltage VGDout has dropped to or below a predetermined threshold voltage (first threshold) V13 shown in Fig. 4. The threshold voltage V13 of the drive power supply voltage VGDout can be set arbitrarily between the voltage V11 in the normal operation state and the drive-disabling voltage V12. The threshold voltage V13 is, for example, a voltage higher than the drive-disabling voltage V12 by a predetermined value. Note that the threshold voltage V13 may be the same as the drive-disabling voltage V12.

[0055] When the drive power supply voltage VGDout drops and reaches the threshold voltage V13 (P11 in FIG. 4), the control signal generating unit 44 generates a control signal for controlling the drive circuits GD1-GD4 so that the electrical energy remaining in the reactor 12 is consumed by the switching circuit 13, and outputs the control signal to the drive circuits GD1-GD4. Note that the control signal generating unit 44 may output a control signal to a chopper control unit (not shown) that controls the chopper, such that the chopper switching element SW10 is turned off.

[0056] Specifically, the control signal generating unit 44 outputs a control signal to the driving circuits GD1 and GD2 to turn on the switching elements SW1 and SW2, for example. In response to this, the driving circuits GD1 and GD2 switch the switching elements SW1 and SW2 to the on state. At this time, the chopper switching element SW10 is also in the off state because no power is supplied to the driving circuit (not shown) due to the voltage drop of the input power source 60. As a result, a return current flows through the circuit that flows from the reactor 12 to the switching circuit 13 and the diode 15 and returns to the reactor 12. Therefore, the electrical energy remaining in the reactor 12 is consumed. The chopper switching element SW10 may be switched to the off state by a chopper control unit (not shown) in response to the voltage drop of the input power source 60.

[0057] Therefore, the current flowing within the circuit of the power conversion unit 110 decreases at an earlier timing than in the conventional configuration described above, at time t2 when the drive power supply voltage VGDout reaches the threshold voltage V13 (the internal current Isw at that time is I2).

[0058] Moreover, in the power conversion device 52 according to the second embodiment, power is supplied from the capacitor 14 to the drive power supply generating section 20. This maintains the supply of power necessary to drive the drive circuits GD1 to GD4.

[0059] In this way, the electrical energy remaining in reactor 12 in the circuit of power conversion unit 110 can be consumed (P13 shown in Figure 4) by time t3 (P12 shown in Figure 4) before drive power supply voltage VGDout reaches non-driveable voltage V12.

[0060] When the current detection unit 16 detects that the current has become zero, the control signal generation unit 44 stops outputting the control signals to the drive circuits GD1, GD2, thereby switching the switching elements SW1, SW2 to the OFF state, respectively.

[0061] By performing the above-described stop process, even if the drive power supply voltage VGDout drops and reaches the threshold voltage V13, the drive circuits GD1 to GD4 can be controlled so that the electrical energy remaining in the reactor 12 is consumed by the switching circuit 13. This makes it possible to suppress the occurrence of a surge voltage in the power conversion device 52.

[0062] <Modification of the second embodiment> In the power conversion device 52 having the above configuration, it may be determined whether the voltage drop of the input power source 60 has been resolved after the above-mentioned stop processing. Specifically, the control signal generating unit 44 determines whether the drive power source voltage VGDout has increased to or above the threshold voltage V13 after the above-mentioned stop processing. If the drive power source voltage VGDout has increased to or above the threshold voltage V13, the drive control unit 240 performs the following recovery processing.

[0063] The recovery process may be a process of canceling the above-mentioned stop process and returning the power conversion unit 110 to the normal operation state, or a process of transmitting a recovery possible signal indicating that the voltage drop has been resolved to a higher-level system. The recovery process may also include a step of checking whether the higher-level system is operating normally. This makes it possible to check whether the cause of the voltage drop due to a power outage or the like is also affecting the higher-level system.

[0064] <Embodiment 3> 5 is a diagram showing a schematic configuration of a power supply system 3 including a power conversion device 53 according to embodiment 3. The power conversion device 53 according to embodiment 3 differs from the power conversion device 52 according to embodiment 2 which performs a stop process in response to a drop in the drive power supply voltage VGDout in that the power conversion device 53 according to embodiment 3 performs a stop process in response to a drop in the control power supply voltage VGCout. In the following, the same components as those in embodiment 2 are denoted by the same reference numerals and their description is omitted, and only the parts different from embodiment 2 will be described.

[0065] (Overall composition) The power conversion device 53 includes a power conversion unit 110 and a drive control unit 340. The drive control unit 340 includes a control voltage detection unit 42, a drive voltage detection unit 43, and a control signal generation unit 45. The control signal generation unit 45 controls the stop process in response to a drop in the control power supply voltage VGCout caused by a voltage drop in the input power supply 60. The control signal generation unit 45 generates a control signal for controlling the stop process, and outputs the generated control signal to the drive circuits GD1 to GD4. As a result, in the stop process, the control signal generation unit 45 controls the switching of the switching elements SW1 to SW4 by the drive circuits GD1 to GD4. The stop process will be described in detail later.

[0066] FIG. 6 shows the time changes of the internal current Isw, the drive power supply voltage VGDout, and the control power supply voltage VGCout when the voltage of the input power supply 60 drops in the power conversion device 53 according to the third embodiment and the conventional power conversion device 952. In FIG. 6, the time changes of the internal current Isw flowing through the circuit of the power conversion unit 110 of the power conversion device 53 according to the third embodiment are shown by solid lines. In FIG. 6, similarly to the case of FIG. 4, the time changes of the internal current Isw flowing through the circuit of the power conversion unit 910 of the conventional power conversion device 952 are shown by dashed lines. The meanings of I1, V11, and V12 shown in FIG. 6 are as described with reference to FIG. 4 in the second embodiment.

[0067] As shown in Fig. 6, in the conventional power conversion device 952 shown in Fig. 3, as the internal current Isw decreases, the control power supply voltage VGCout may reach the uncontrollable voltage V22 (P94) before the drive power supply voltage VGDout reaches the undriveable voltage V12 (P95). In this case, the driving of the switching elements SW1 to SW4 cannot be controlled, so the switching elements SW1 to SW4 are turned off. As a result, the internal current Isw flowing through the circuit of the power conversion unit 910 becomes zero (P96 shown in Fig. 6). Therefore, as in the case of the second embodiment, a surge voltage may occur in the power conversion device 952.

[0068] In order to suppress the occurrence of the above-mentioned surge voltage, the power conversion device 53 according to the third embodiment performs the following stop processing.

[0069] (Stop processing) 6 again, the stop processing in the drive control unit 340 of the power conversion device 53 according to the third embodiment will be described. The stop processing is processing for consuming electrical energy stored in the circuit of the power conversion unit 110 of the power conversion device 53 in response to a drop in the control power supply voltage VGCout.

[0070] The control signal generating unit 45 of the drive control unit 340 determines whether the control power supply voltage VGCout has dropped to or below a threshold voltage (second threshold) V23 shown in Fig. 6. The threshold voltage V23 of the control power supply voltage VGCout shown in Fig. 6 can be set arbitrarily between the voltage V21 in the normal operation state and the uncontrollable voltage V22. The threshold voltage V23 is, for example, a voltage higher than the uncontrollable voltage V22 by a predetermined value. Note that the threshold voltage V23 may be the same as the uncontrollable voltage V22.

[0071] When the control power supply voltage VGCout drops and reaches the threshold voltage V23 (P24 in FIG. 6), the control signal generating unit 45 generates a control signal for controlling the drive circuits GD1-GD4 so that the electrical energy remaining in the reactor 12 is consumed by the switching circuit 13, and outputs the control signal to the drive circuits GD1-GD4. Note that the control signal generating unit 45 may generate and output a control signal to a chopper control unit (not shown) to turn off the chopper switching element SW10.

[0072] Specifically, the control signal generating unit 45 outputs a control signal to the driving circuits GD1 and GD2 to turn on the switching elements SW1 and SW2, for example. In response to this, the driving circuits GD1 and GD2 switch the switching elements SW1 and SW2 to the on state. At this time, the chopper switching element SW10 is also in the off state because no power is supplied to the driving circuit (not shown) due to the voltage drop of the input power source 60. As a result, a return current flows through the circuit that flows from the reactor 12 to the switching circuit 13 and the diode 15 and returns to the reactor 12. Therefore, the electrical energy remaining in the reactor 12 is consumed. The chopper switching element SW10 may be switched to the off state by a chopper control unit (not shown) in response to the voltage drop of the input power source 60.

[0073] This makes it possible to consume the electrical energy remaining in reactor 12 within the circuit of power conversion unit 110 (P26 shown in Figure 6) by time t3 (P25 shown in Figure 6) before control power supply voltage VGCout reaches uncontrollable voltage V22.

[0074] When the current detection unit 16 detects that the current has become zero, the control signal generation unit 45 stops outputting the control signals to the drive circuits GD1, GD2, thereby switching the switching elements SW1, SW2 to the OFF state, respectively.

[0075] By performing the above-described stop process, even if the control power supply voltage VGCout drops and reaches the threshold voltage V23, the drive circuits GD1 to GD4 can be controlled so that the electrical energy remaining in the reactor 12 is consumed by the switching circuit 13. This makes it possible to suppress the occurrence of a surge voltage in the power conversion device 53.

[0076] <Modification of the third embodiment> In the power conversion device 53 having the above configuration, it may be determined whether the voltage drop of the input power source 60 has been resolved after the above-mentioned stop processing. Specifically, the control signal generating unit 45 determines whether the control power supply voltage VGCout has risen to or above the threshold voltage V23 after the above-mentioned stop processing. If the control power supply voltage VGCout has risen to or above the threshold voltage V23, the drive control unit 340 performs the above-mentioned recovery processing.

[0077] Moreover, the power electronics device 53 may perform the stop processing of the above-mentioned embodiment 2 in addition to the above-mentioned stop processing.

[0078] <Embodiment 4> 7 is a diagram showing a schematic configuration of a power supply system 4 including a power conversion device 54 according to embodiment 4. The power conversion device 54 according to embodiment 4 differs from the power conversion device 52 according to embodiment 2 in that it has two power conversion units 110A, 110B. In the following, the same components as those in embodiment 2 are denoted by the same reference numerals and description thereof is omitted, and only the parts different from embodiment 2 will be described.

[0079] The power conversion device 54 has circuit breakers 84, 85, 86, and 87. The circuit breaker 84 is located between the power conversion unit 110A and the input power source 60. The circuit breaker 84 electrically connects or disconnects the power conversion unit 110A and the input power source 60. In addition, the circuit breaker 85 is located between the power conversion unit 110B and the input power source 60. The circuit breaker 85 electrically connects or disconnects the power conversion unit 110B and the input power source 60.

[0080] The circuit breaker 86 is located between the power conversion unit 110A and the transformer 73. The circuit breaker 86 electrically connects or disconnects the power conversion unit 110A and the transformer 73. The circuit breaker 87 is located between the power conversion unit 110B and the transformer 73. The circuit breaker 87 electrically connects or disconnects the power conversion unit 110B and the transformer 73.

[0081] The circuit breakers 84, 85, 86 and 87 can be realized by, for example, electromagnetic switches. The opening and closing of the circuit breakers 84 , 85 , 86 and 87 is controlled by a drive control unit 440 .

[0082] The configurations of the two power conversion units 110A, 110B of the power conversion device 54 are basically the same as the configuration of the power conversion unit 110 of the power conversion device 52. For convenience of explanation, Fig. 7 shows a simplified portion of the circuits of the power conversion units 110A, 110B. In Fig. 7, for example, the switching circuit 13 is shown as one block. Also, the drive circuits GD1 to GD4 are shown as one block.

[0083] The drive power generation unit 20 of the power conversion unit 110A supplies drive power to the circuit breaker 86. The drive power generation unit 20 of the power conversion unit 110B supplies drive power to the circuit breaker 87. This makes it possible to drive the circuit breakers 86 and 87 even if a voltage drop occurs in either of the power conversion units.

[0084] The drive control unit 440 may generate control signals for controlling the two power conversion units 110A, 110B so that the current outputs of the two power conversion units 110A, 110B have a desired ratio, and output the control signals to the two power conversion units 110A, 110B.

[0085] (When one power conversion unit is controlled at 100% and the other at 0%) For example, the drive control unit 440 may generate a control signal so that the current output of one of the two power conversion units 110A, 110B is 100% and the current output of the other power conversion unit is 0% in a normal operation state. When the drive power supply voltage VGDout of one of the two power conversion units 110A, 110B that operates at 100% current output drops, the drive control unit 440 may generate a control signal so that the current output of one power conversion unit is 0% and the current output of the other power conversion unit is 100%. When the drive power supply voltage VGDout drops to a threshold voltage V13 or less, the drive control unit 440 may perform the stop processing of the above-mentioned embodiment 2.

[0086] (50% each) Also, for example, the drive control unit 440 may generate a control signal so that the current outputs of the two power conversion units 110A, 110B are 50% each in the normal operation state. Then, when the voltage of the input power source 60 drops, the drive control unit 440 may perform a stop process as described below.

[0087] When the drive power supply voltage VGDout in one of the two power conversion units 110A, 110B drops below the threshold voltage V13 and the control power supply voltage VGCout in both of the two power conversion units 110A, 110B does not drop below the threshold voltage V23, the drive control unit 440 may perform the stop processing of the second embodiment only in the one of the two power conversion units. In this case, since the control power supply voltage VGCout is within the normal range, it is assumed that there is no problem with the input power supply 60. Therefore, it is assumed that the other of the two power conversion units 110A, 110B is in an operable state. For this reason, by performing the stop processing of the second embodiment described above only in the one of the two power conversion units 110A, 110B in which the drive power supply voltage VGDout has dropped, the other power conversion unit can continue to supply power to the load 70.

[0088] Furthermore, in the one power conversion unit for which the stop process has been performed, when the voltage drop of the drive power supply voltage VGDout has been resolved, the drive control unit 440 may perform the above-mentioned restoration process.

[0089] In addition, if the drive power supply voltage VGDout drops below the threshold voltage V13 in both of the two power conversion units 110A, 110B, the drive control unit 440 may perform the stop processing of embodiment 2 for both of the two power conversion units 110A, 110B.

[0090] Then, after performing the above-mentioned stop processing, if the voltage drop in the drive power supply voltage VGDout is resolved in one of the two power conversion units 110A, 110B in which the drive power supply voltage VGDout dropped first, the drive control unit 440 may perform the above-mentioned recovery processing on that one of the power conversion units.

[0091] (When the ratio is other than 0% and one ratio is different from the other ratio) The drive control unit 440 may control the two power conversion units 110A, 110B to operate with current outputs of different ratios other than 0% in a normal operating state.

[0092] For example, the drive control unit 440 may generate a control signal so that the current output of one of the two power conversion units 110A, 110B is 70% and the current output of the other is 30%. Then, when the drive power supply voltage VGDout in at least one of the two power conversion units 110A, 110B drops to or below the threshold voltage V13 and the control power supply voltage VGCout in neither of the two power conversion units 110A, 110B drops to or below the threshold voltage V23, the drive control unit 440 may perform the stop processing of the second embodiment only in one of the two power conversion units.

[0093] After performing the stop process, the drive control unit 440 may perform the above-mentioned restoration process when the drop in the drive power supply voltage VGDout is resolved in the other of the two power conversion units 110A, 110B whose power output is 30%. There is a possibility that the power conversion unit with a smaller power output ratio will consume electrical energy faster. For this reason, by restoring the power conversion unit with a smaller power output ratio and consuming electrical energy faster, the risk of surge voltage occurrence can be reduced.

[0094] <Modification of the fourth embodiment> In the power conversion device 54 having the above configuration, when the control power supply voltage VGCout drops to or below the threshold voltage V23, the drive control section 440 may perform the stop processing of the third embodiment on both of the two power conversion sections 110A, 110B.

[0095] In this case, for example, there is a possibility that an abnormality has occurred in the input power supply 60, and therefore the drive control unit 440 may not be able to normally control either of the two power conversion units 110A, 110B. Therefore, the drive control unit 440 does not need to perform the above-mentioned recovery process after the stop process. Note that, if the drop in the control power supply voltage has been resolved, the drive control unit 440 may perform the above-mentioned recovery process.

[0096] <Other embodiments> Although the embodiment of the present invention has been described above, the above-mentioned embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-mentioned embodiment, and it is possible to carry out the above-mentioned embodiment by appropriately modifying it within the scope of the gist of the present invention.

[0097] In each of the above embodiments, the load 70 includes one track circuit 71. However, the load may include multiple track circuits.

[0098] In the second to fourth embodiments, when the current detection unit 16 detects that the current has become zero, the control signal generation units 44 and 45 stop outputting control signals to the drive circuits GD1 and GD2 to switch the switching elements SW1 and SW2 to the OFF state, respectively. However, the control signal generation units 44 and 45 may also control the drive circuits to switch the switching elements in the ON state to the OFF state when a predetermined time has elapsed.

[0099] In the second to fourth embodiments, the control signal generating units 44 and 45 output control signals to the drive circuits GD1 and GD2 to turn on the switching elements SW1 and SW2. However, the control signal generating units may output control signals to the drive circuits GD3 and GD4 to turn on the switching elements SW3 and SW4.

[0100] In the second to fourth embodiments, the control signal generating units 44 and 45 control the stop process according to the voltage drop of the input power supply 60. However, the control signal generating unit may control the stop process according to the rate of voltage drop of the input power supply. For example, the control signal generating unit may suspend the stop process when the rate of drop of the drive power supply voltage or the control power supply voltage is equal to or lower than a predetermined value. When the rate of drop of the drive power supply voltage or the control power supply voltage is equal to or lower than a predetermined value, the electrical energy stored in the circuit of the power conversion unit may have already been consumed. In such a case, the signal generating unit suspends the stop process, thereby making it possible to avoid unnecessary stop processing.

[0101] In the fourth embodiment, the power conversion device 54 has two power conversion units 110A and 110B. However, the power conversion device may have three or more power conversion units. In this case, the power conversion device may have a smaller number of drive control units than the number of the power conversion units.

[0102] In the fourth embodiment, the circuit breakers 84, 85, 86, and 87 are provided on both the input power source 60 side and the transformer 73 side of the two power conversion units 110A and 110B, respectively. However, the circuit breakers may be provided only on the power source side or the transformer side of the power conversion units. Also, the circuit breakers may be provided only on some of the multiple power conversion units. [Industrial Applicability]

[0103] The present invention can be used in a power conversion device that controls power supplied from a power source to a load. [Explanation of symbols]

[0104] 1, 2, 3, 4 Power Supply System 10, 110, 110A, 110B Power conversion section 11 Rectifier circuit 12 Reactor 13 Switching Circuits 14 Capacitor 15 Diodes 16 Current detection section 20 Drive power generation unit 30 Control power generation unit 40, 240, 340, 440 Drive control unit 42 Control voltage detection section 43 Drive voltage detection unit 44, 45 Control signal generator 51, 52, 53, 54 Power conversion device 60 Input power 70 Load 71 Track circuit 73 Trans 84, 85, 86, 87 Circuit breakers D1, D2, D3, D4 Diodes GD1, GD2, GD3, GD4 drive circuit SW1, SW2, SW3, SW4 switching elements SW10 Chopper switching element

Claims

1. A power conversion device that controls power supplied from a power source to a load, a rectifier circuit that rectifies the AC current output from the power supply; a capacitor electrically connected in parallel to the rectifier circuit; a reactor electrically connected in series to the rectifier circuit and the capacitor; a switching circuit including a plurality of switching elements, electrically connected to the rectifier circuit via the reactor, and configured to supply power from the rectifier circuit to the load by switching the plurality of switching elements between an on state and an off state; a drive circuit that switches the plurality of switching elements between an on state and an off state; a drive control unit that generates a control signal for controlling the drive circuit so as to switch the plurality of switching elements between an on state and an off state, and outputs the control signal to the drive circuit; a drive power supply generating unit electrically connected in parallel to the rectifier circuit and the capacitor, and configured to supply power supplied from the rectifier circuit or the capacitor to the drive circuit; having Power conversion device.

2. The power conversion device according to claim 1, When the voltage input from the drive power supply generation unit to the drive circuit drops and reaches a first threshold, the drive control unit generates a control signal to control the drive circuit so that the electrical energy remaining in the reactor is consumed by the switching circuit, and outputs the control signal to the drive circuit. Power conversion device.

3. The power conversion device according to claim 1, a control power supply generating unit that supplies the power output from the power supply to the drive control unit; When the voltage input from the control power supply generation unit to the drive control unit drops and reaches a second threshold, the drive control unit generates a control signal to control the drive circuit so that the electrical energy remaining in the reactor is consumed by the switching circuit, and outputs the control signal to the drive circuit. Power conversion device.

4. 4. The power conversion device according to claim 1, a plurality of power conversion units including the rectifier circuit, the capacitor, the switching circuit, the drive circuit, and the drive power supply generation unit, and controlling the power supplied from the power supply to the load; the plurality of power conversion units are electrically connected in parallel to one another, the drive control unit generates a control signal for controlling the drive circuit included in at least one of the plurality of power conversion units, and outputs the control signal to the drive circuit; Power conversion device.

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