DC power supply unit

Abstract

The control unit of the DC power supply device is configured to: after simultaneously performing control to disconnect the series switching element and the conduction switching element, perform control to disconnect the semiconductor switching element, or perform control to disconnect the series switching element, the conduction switching element, and the semiconductor switching element in this order.

Description

Technical Field

[0001] The present invention relates to a DC power supply device, and in particular to a DC power supply device having a current cutoff portion for cutting off a high voltage current at high speed. Background Art

[0002] As protection against accident current in the output of a DC power supply device, protection is generally provided by a fuse or a mechanical DC disconnector. However, the conventional mechanical DC disconnector takes a long time to cut off the current tolerance of power semiconductors such as IGBTs used in DC power supply devices, so that it is not possible to protect the semiconductor components in time, and the impact of the accident may be amplified. Therefore, as a conventional solution, a power supply device having a current cutoff unit that cuts off high-voltage current at high speed is known. Such a DC power supply device is described, for example, in Japanese Patent Publication No. 2019-36405.

[0003] In the above-mentioned Japanese Patent Publication No. 2019-36405, a power supply device is disclosed, which includes a main circuit switch (thyristor or mechanical switch) arranged between the power supply and the load, and a capacitor connected in parallel with the main circuit switch. In the above-mentioned power supply device, it is configured that when a fault current flows through the main circuit switch, a superimposed current flows from the above-mentioned capacitor to the main circuit switch. The above-mentioned superimposed current flows through the main circuit switch in a direction opposite to the above-mentioned fault current. As a result, the above-mentioned fault current is offset by the above-mentioned superimposed current, so that the main circuit switch can be cut off at a high speed. In addition, in the case of using a mechanical switch as the main circuit switch, the arc generated at the main circuit contact when disconnected is also suppressed, so that the main circuit switch can be cut off at a high speed, and the increase in conduction loss can be suppressed.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-36405 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, in the above-mentioned Japanese Patent Publication No. 2019-36405, in order to pass the superimposed current to the main circuit switch, a commutation capacitor needs to be provided. Here, the commutation capacitor is a relatively large component, so there is a case where the power supply device is large-scaled. Therefore, a DC power supply device that can cut off the accident current at a high speed and can be miniaturized is desired.

[0009] The present invention is made to solve the above-mentioned problems, and one of the objects of the present invention is to provide a DC power supply device that can cut off a fault current at a high speed while suppressing an increase in conduction loss and can reduce the size of the DC power supply device.

[0010] Solutions for solving problems

[0011] In order to achieve the above-mentioned object, a DC power supply device according to one aspect of the present invention comprises: a rectifier, which converts an AC input voltage supplied from an AC voltage source into a DC voltage; a current cutoff unit, which performs electrical connection and electrical cutoff between the rectifier and a load; and a control unit, which controls the rectifier and the current cutoff unit, wherein the current cutoff unit includes: a series circuit, which has a series switch element with a withstand voltage greater than the rated voltage of the DC voltage and a self-arc extinguishing conduction switching element with a withstand voltage less than the rated voltage, the conduction switching element being connected in series with the series switch element on the load side; and a self-arc extinguishing semiconductor switch element with a withstand voltage greater than the rated voltage, which is connected in parallel with the series circuit, the conduction loss of each of the series switch element and the conduction switching element being smaller than the conduction loss of the semiconductor switch element, and the control unit is configured to: after simultaneously performing control to disconnect the series switch element and control to disconnect the conduction switching element, control to disconnect the semiconductor switch element is performed, or control to disconnect the series switch element, the conduction switching element, and the semiconductor switch element in this order, thereby controlling to disconnect the current cutoff unit. Furthermore, the series switching element includes not only semiconductor elements but also mechanical switches.

[0012] In a DC power supply device based on one aspect of the present invention, as described above, after the control of disconnecting the series switch element and the control of disconnecting the conduction switching element are simultaneously performed, the semiconductor switch element is disconnected, or the series switch element, the conduction switching element, and the semiconductor switch element are disconnected in this order. As a result, the current that is to flow to the series switch element and the conduction switching element is diverted to the semiconductor switch element, so the semiconductor switch element can be disconnected in a state where all the current flows to the semiconductor switch element. Here, since the semiconductor switch element does not generate an arc when it is disconnected, it is not necessary to use the charging energy of the capacitor to flow a superimposed current to the semiconductor switch element in order to quickly set the semiconductor switch element to an off state. Therefore, by controlling as described above, the fault current can be cut off at a high speed by the semiconductor switch element without using a capacitor. As a result, the DC power supply device can be miniaturized while cutting off the fault current at a high speed.

[0013] In addition, a series circuit of a series switch element and a conduction switching element having a relatively small conduction loss compared to a semiconductor switch element is connected in parallel with the semiconductor switch element, thereby making it possible to allow at least a portion of the current to flow through the series circuit side having a relatively small conduction loss, unlike a case where only a semiconductor switch element is provided. As a result, conduction loss (power consumption) can be suppressed compared to a case where only a semiconductor switch element is provided. As a result, the accident current can be cut off at a high speed while suppressing an increase in conduction loss, and the DC power supply device can be miniaturized.

[0014] In addition, the current that is to flow to the series switch element and the conduction switching element is diverted to the semiconductor switch element, thereby enabling the semiconductor switch element to be disconnected in a state where no current flows through the series switch element and the conduction switching element. Thus, when the semiconductor switch element is set to the disconnected state, the semiconductor switch element and the series switch element bear the rated voltage of the DC power supply device. On the other hand, since the series switch element provided at the front stage of the conduction switching element is in the disconnected state, the voltage borne by the conduction switching element is substantially zero. As a result, it is possible to suppress the conduction switching element from bearing a voltage (rated voltage) above the withstand voltage, thereby suppressing the conduction switching element from being destroyed. In addition, since the withstand voltages of the series switch element and the conduction switching element are each above the rated voltage, the series switch element and the conduction switching element will not be destroyed. Thus, it is possible to suppress the element (conduction switching element) of the current cutoff portion from being destroyed.

[0015] In a DC power supply device based on one aspect described above, it is preferred that the control unit is configured to: after simultaneously performing control to disconnect the series switch element and control to disconnect the conduction switching element, control to disconnect the semiconductor switch element is performed, thereby performing control to disconnect the current cutoff unit. Here, in the case where there is a time difference between the control to disconnect the series switch element and the control to disconnect the conduction switching element, the control to disconnect the semiconductor switch element is delayed according to the above time difference, so the time for the current to flow to the semiconductor switch element increases. By simultaneously performing control to disconnect the series switch element and control to disconnect the conduction switching element, it is possible to suppress the delay in the control to disconnect the semiconductor switch element, and to suppress the increase in the time for the current to flow to the semiconductor switch element. Here, the size of the semiconductor switch element depends on the time that can be energized. Therefore, by suppressing the increase in the time that the current flows to the semiconductor switch element, an element with a relatively short energization time can be used as the semiconductor switch element. As a result, it is possible to suppress the size of the semiconductor switch element.

[0016] In the DC power supply device based on one aspect described above, it is preferred that the control unit is configured to control the current cut-off unit to be cut off in the following manner: the conduction switching element is controlled to be cut off so that the current flowing through the series circuit of the series switch element and the conduction switching element is diverted to the semiconductor switch element side, and after the current no longer flows through the series switch element, the semiconductor switch element is controlled to be cut off. With such a configuration, it is possible to prevent the semiconductor switch element from being cut off while current is still flowing in the series circuit of the series switch element and the conduction switching element. As a result, the series switch element can be reliably set to the off state when the semiconductor switch element is cut off. As a result, it is possible to more reliably prevent the conduction switching element from being subjected to a high voltage (rated voltage).

[0017] In this case, the conduction switching element is configured to be able to switch faster than the series switch element, and the control unit is configured to control the semiconductor switch element to be turned off after a predetermined time greater than the turn-off time of the series switch element has passed since the conduction switching element was controlled to be turned off, thereby controlling the current cutoff unit to be turned off. With this configuration, it is possible to more reliably control the semiconductor switch element to be turned off after the current no longer flows in the series switch element.

[0018] In the DC power supply device according to the above aspect, it is preferred that the control unit is configured to control the series connection switch element and the conduction switching element to be turned on after the semiconductor switch element is turned on, thereby controlling the current cutoff unit to be turned on. With this configuration, it is possible to suppress the series connection switch element and the conduction switching element from being turned on during the period when the semiconductor switch element is turned off, thereby suppressing the conduction switching element from being applied with a high voltage (rated voltage of the DC power supply device).

[0019] In this case, the control unit is configured to control the series connection switch element and the conduction switching element to be turned on after the semiconductor switch element is turned on so that the output voltage of the current cutoff unit increases and the increase in the output voltage stops, thereby controlling the current cutoff unit to be turned on. Here, the voltage to which the semiconductor switch element is subjected decreases in accordance with the increase in the output voltage of the current cutoff unit. Therefore, after the increase in the output voltage of the current cutoff unit stops, the series connection switch element and the conduction switching element are controlled to be turned on, thereby enabling the series connection switch element and the conduction switching element to be turned on after the voltage to which the semiconductor switch element is subjected becomes minimum. As a result, since the conduction switching element connected in parallel with the semiconductor switch element also withstands a voltage of the same magnitude as the voltage to which the semiconductor switch element is subjected, it is possible to suppress the conduction switching element from being applied with a high voltage.

[0020] In the DC power supply device based on the above aspect, it is preferred that the current cutoff unit includes a diode element connected in parallel with the series circuit and in series with the semiconductor switch element, and the total value of the on-voltage of the diode element and the on-voltage of the semiconductor switch element is greater than the total value of the on-voltage of the series switch element and the on-voltage of the conduction switching element. With this configuration, the current flowing in the series circuit of the diode element and the semiconductor switch element, whose total on-voltage value is relatively large, can be relatively small. As a result, the heat generation of the diode element and the semiconductor switch element can be relatively small.

[0021] In addition, since the conduction loss of the series switch element and the conduction switching element is smaller than the conduction loss of the semiconductor switch element, the on-resistance of the series switch element and the conduction switching element is smaller than the on-resistance of the semiconductor switch element. Therefore, by passing a current larger than the current flowing through the series circuit of the diode element and the semiconductor switch element through the series switch element and the conduction switching element, which have relatively small on-resistance, it is possible to minimize the increase in the heat generated by the series switch element and the conduction switching element. As a result, it is possible to suppress the increase in the heat generated by the current cutoff portion as a whole.

[0022] In the DC power supply device according to one aspect above, it is preferred that the device further comprises a power storage unit for storing the DC power converted by the rectifier, and the control unit is configured to: when the DC power of the power storage unit is supplied to the load, after simultaneously performing control to disconnect the series switch element and the conduction switching element, perform control to disconnect the semiconductor switch element, or perform control to disconnect the series switch element, the conduction switching element, and the semiconductor switch element in this order, thereby performing control to disconnect the current flowing from the power storage unit to the load by the current cut-off unit. With this configuration, it is possible to suppress the increase of conduction loss when the current is conducted while suppressing the destruction of the elements of the current cut-off unit.

[0023] In the DC power supply device based on one aspect above, it is preferred that the series switch element, the conduction switching element and the semiconductor switch element include thyristors, MOSFETs and IGBTs, respectively. With such a configuration, since the on-voltage of the thyristor is relatively low, by using the thyristor as the series switch element, the conduction loss increase when the current is turned on (during normal operation of the DC power supply device) can be effectively suppressed. In addition, since the IGBT switches at a relatively high speed and has a high withstand voltage, by using the IGBT as the semiconductor switch element, the current can be cut off at a high speed, and even if the semiconductor switch element is subjected to a high voltage (rated voltage), the semiconductor switch element can be suppressed from being destroyed. In addition, since the conduction loss of the MOSFET is relatively low, by using the MOSFET as the conduction switching element, the conduction loss increase when the current is turned on (during normal operation of the DC power supply device) can be more effectively suppressed. In addition, since the MOSFET switches at a relatively high speed, the current flowing to the DC circuit of the series switch element and the conduction switching element can be relatively quickly diverted to the semiconductor switch element side when the current is cut off. As a result, the time required for the current cut-off unit to cut off the current can be shortened.

[0024] Effects of the Invention

[0025] According to the present invention, as described above, the fault current can be interrupted at a high speed while suppressing an increase in conduction loss, and the DC power supply device can be miniaturized. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a diagram showing the structure of a DC power supply device according to one embodiment.

[0027] Figure 2 It is a diagram showing gate signals and current values ​​of respective elements of a current interruption unit according to one embodiment.

[0028] Figure 3 This is a diagram showing the flow of current when the IGBT is turned on and conduction control is started (period A) in the current cutoff unit according to one embodiment.

[0029] Figure 4 This is a diagram showing the flow of current when the thyristor and the MOSFET are turned on (period B) in the current cutoff section according to one embodiment when the thyristor and the MOSFET are turned on at the time of conduction.

[0030] Figure 5 This is a diagram showing the flow of current when the thyristor and the MOSFET are turned off and current cutoff control is started (period C) in the current cutoff section according to one embodiment.

[0031] Figure 6This is a diagram showing the state of the current cutoff unit when the IGBT according to one embodiment is turned off and the current cutoff control is completed (period D). DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0033] [Present Embodiment]

[0034] Reference Figure 1 to Figure 6 The structure of the DC power supply device 100 according to this embodiment will be described.

[0035] (Structure of DC power supply device)

[0036] like Figure 1 As shown, the DC power supply device 100 includes a rectifier 1, a power storage unit 2, a current sensor 3, a current cutoff unit 4, a control unit 5, a drive unit 6, and a voltage sensor 7. The DC power supply device 100 is used in a solar power generation system, for example.

[0037] The rectifier 1 is configured to convert an AC input voltage input from an external system 101 into a DC voltage. An AC disconnector 102 is provided outside the DC power supply device 100 for switching the current between the system 101 and the DC power supply device 100 between conduction and disconnection. In addition, the system 101 is an example of an "AC voltage source" in the present invention.

[0038] The power storage unit 2 is configured to store the DC power converted by the rectifier 1. When power is not supplied from the grid 101 (at the time of a power outage, etc.), the power storage unit 2 supplies power to the load 103 as a power source.

[0039] The current sensor 3 is configured to detect the value of the current flowing between the rectifier 1 (power storage unit 2 ) and the current interruption unit 4 .

[0040] The current cut-off unit 4 is configured to perform electrical connection and electrical cut-off between the rectifier 1 (power storage unit 2) and the load 103. Specifically, the current cut-off unit 4 includes a thyristor 40 and a self-arc extinguishing MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor: Metal Oxide Semiconductor Field Effect Transistor) 41 connected in series with the thyristor 40. The MOSFET 41 is connected in series with the thyristor 40 on the load 103 side relative to the thyristor 40. In addition, the thyristor 40 and the MOSFET 41 are examples of the "series switching element" and the "conduction switching element" in the present invention, respectively.

[0041] In addition, the current cutoff unit 4 includes a diode element 42 and a self-arc extinguishing IGBT (Insulated Gate Bipolar Transistor: Insulated Gate Bipolar Transistor) 43. The IGBT 43 is connected in series with the diode element 42 on the load 103 side relative to the diode element 42. As the IGBT 43, an RB (Reverse Blocking: Reverse Blocking)-IGBT and an RC (Reverse Conducting: Reverse Conducting)-IGBT can be used. In addition, the IGBT 43 is an example of a "semiconductor switching element" in the present invention.

[0042] Furthermore, a series circuit of the thyristor 40 and the MOSFET 41 and a series circuit of the diode element 42 and the IGBT 43 are connected in parallel.

[0043] In addition, the withstand voltage of the thyristor 40 (e.g., 1600 V) is greater than the rated voltage (e.g., 750 V) of the DC voltage used in the DC power supply device 100. In addition, the withstand voltage of the MOSFET 41 (e.g., 10 V to 20 V) is smaller than the above-mentioned rated voltage. In addition, the withstand voltage of the IGBT 43 (e.g., 1600 V) is greater than the above-mentioned rated voltage.

[0044] In addition, the conduction loss of each of the thyristor 40 and the MOSFET 41 is smaller than the conduction loss of the IGBT 43 (when the current of the same magnitude as that of the thyristor 40 and the MOSFET 41 flows). In addition, the MOSFET 41 and the IGBT 43 are each configured to be able to switch at a higher speed than the thyristor 40. In addition, the MOSFET 41 is configured to be able to switch at a higher speed than the IGBT 43.

[0045] In addition, the current cut-off unit 4 performs current cut-off by a relatively small number of elements (four elements, namely, the thyristor 40, the MOSFET 41, the diode element 42, and the IGBT 43). In contrast, in a structure in which, for example, a discharge current from a capacitor is used to flow a counteracting current to a switch, a relatively large number of elements (components) such as a resistor, a reactor, a thyristor, and a diode are required in addition to a switch and a capacitor. Therefore, by constituting the current cut-off unit 4 with a relatively small number of elements, it is possible to suppress an increase in the failure rate of the current cut-off unit 4 (suppress a decrease in reliability).

[0046] The control unit 5 is configured to control the rectifier 1 and the current cutoff unit 4. Specifically, the control unit 5 controls the operation of the rectifier 1 by sending a gate signal to a switching element (not shown) provided in the rectifier 1. The control unit 5 is configured to send a command signal for controlling the current cutoff unit 4 to the drive unit 6.

[0047] Specifically, the drive unit 6 is configured to transmit a gate signal for turning on or off the thyristor 40 , the MOSFET 41 , and the IGBT 43 of the current cutoff unit 4 based on a command signal from the control unit 5 .

[0048] In addition, the voltage sensor 7 is configured to detect the output voltage of the current interruption unit 4 (the voltage between the current interruption unit 4 and the load 103 ).

[0049] (Operation of DC power supply device)

[0050] Next, refer to Figure 2 to Figure 6 The operation of the DC power supply device 100 will be described.

[0051] First, a case where the rectifier 1 starts operating to supply power to the load 103 when the DC power supply device 100 is started will be described.

[0052] like Figure 2 As shown in (a) of FIG. 1 , by sending a gate signal to IGBT 43, IGBT 43 is turned on (turned on). Figure 3 As shown, during the period I from when the gate signal is sent to the IGBT 43 to when the gate signal is sent to the MOSFET 41 and the thyristor 40 (see Figure 2 ), the current from rectifier 1 (refer to Figure 3 The dotted line) flows through the diode element 42 and the IGBT 43 to the load 103 side. Figure 2 As shown in (d) and (f) of FIG. 1 , by turning on the IGBT 43, the value of the output current of the current cutoff unit 4 (see Figure 2 (d)) and the value of the current flowing through the IGBT 43 (refer to Figure 2 (f)) are increased to the specified size.

[0053] In this embodiment, if Figure 2 As shown in (b) and (c) of FIG. 1 , the control unit 5 is configured to control the thyristor 40 and the MOSFET 41 to be turned on after controlling the IGBT 43 to be turned on, thereby controlling the current cutoff unit 4 to be turned on.

[0054] Here, the output voltage of the current cutoff unit 4 increases due to the turning on of the IGBT 43. In the present embodiment, the control unit 5 is configured to control the current cutoff unit 4 to be turned on by turning on the thyristor 40 and the MOSFET 41 after the increase in the output voltage of the current cutoff unit 4 stops.

[0055] Specifically, when the voltage value detected by the voltage sensor 7 rises to a predetermined maximum voltage, a signal is sent from the voltage sensor 7 to the control unit 5. When receiving the above signal from the voltage sensor 7, the control unit 5 provides a command signal to the drive unit 6 to send a gate signal for turning on the thyristor 40 and the MOSFET 41. Figure 2 Period B begins.

[0056] In detail, the thyristor 40 and the MOSFET 41 are turned on by sending a gate signal to the thyristor 40 and the MOSFET 41. Figure 4 As shown, during period B (refer to Figure 2 ), the current from rectifier 1 (refer to Figure 4 The current is branched by the dotted line (shown in FIG. 1 ) to flow to the series circuit of the diode element 42 and the IGBT 43 and the series circuit of the thyristor 40 and the MOSFET 41, and then flows to the load 103 side.

[0057] like Figure 2 As shown in (e), since the thyristor 40 is turned on, the value of the current flowing through the thyristor 40 increases to a predetermined value. In addition, the current that originally flows only to the series circuit side of the diode element 42 and the IGBT 43 during the period I also flows to the series circuit side of the thyristor 40 and the MOSFET 41 during the period B, so the value of the current flowing through the IGBT 43 during the period B is reduced compared to the value of the current during the period I.

[0058] Here, in the present embodiment, the on-state voltage (forward voltage) V of the diode element 42 is F The total value of the on-state voltage (collector-emitter saturation voltage) Vce of the IGBT 43 is greater than the on-state voltage (forward voltage) Vth of the thyristor 40 and the on-state voltage (drain-source voltage) Vth of the MOSFET 41. DS The total value of is large. Specifically, it becomes (V F +Vce)>>(Vth+V DS ). The ratio of the value of the current flowing through the series circuit of the thyristor 40 and the MOSFET 41 to the value of the current flowing through the series circuit of the diode element 42 and the IGBT 43 is determined by the on-voltage of the above four elements. By making the total value of the on-voltage to be in the above-mentioned relationship, the value of the current flowing through the series circuit of the thyristor 40 and the MOSFET 41 is made larger than the value of the current flowing through the series circuit of the diode element 42 and the IGBT 43. The value of the current flowing through the series circuit of the thyristor 40 and the MOSFET 41 is, for example, about 20 times the value of the current flowing through the series circuit of the diode element 42 and the IGBT 43.

[0059] Thus, a relatively small current flows through the diode element 42 and the IGBT 43, so the heat generated by the diode element 42 and the IGBT 43 can be relatively small. In addition, by configuring an element with a low drain-source resistance as the MOSFET 41, the heat generated by the MOSFET 41 can be reduced. Thus, the heat generated by the components other than the thyristor 40 can be reduced. As a result, the heat sink (not shown) for dissipating heat from the current cutoff unit 4 can be designed by considering only the heat generated by the thyristor 40 (without considering the heat generated by the MOSFET 41, the IGBT 43, and the diode element 42), and the heat sink can be miniaturized.

[0060] Next, the operation of the DC power supply device 100 when the power supply to the load 103 is stopped will be described.

[0061] First, when the current value detected by the current sensor 3 exceeds a preset range, the current sensor 3 sends a signal to the control unit 5. Then, the control unit 5 notified of the signal sends a command signal for shutting off the current cutoff unit 4 to the drive unit 6. This will be described in detail below.

[0062] In this embodiment, if Figure 2 As shown in (a) to (c) of FIG. 1 , the control unit 5 is configured to control the IGBT 43 to be turned off after simultaneously controlling the thyristor 40 to be turned off (turned off) and controlling the MOSFET 41 to be turned off. Specifically, a gate signal for turning off the thyristor 40 and the MOSFET 41 is simultaneously sent to the thyristor 40 and the MOSFET 41. Thus, the period C starts. Thereafter, a gate signal for turning off the IGBT 43 is sent to the IGBT 43, and the period C ends.

[0063] Therefore, if Figure 2 As shown in (d) to (f), the value of the current flowing through the thyristor 40 during the period C is smaller than the value of the current flowing through the thyristor 40 during the period B (see Figure 2 In addition, the value of the current flowing through the IGBT 43 during the period C is greater than the value of the current flowing through the IGBT 43 during the period B (see Figure 2 This is because, if Figure 5 As shown, since MOSFET 41 is turned off, no current flows through the series circuit of thyristor 40 and MOSFET 41, and thus the current (refer to Figure 4 ) during period C and flows to the IGBT 43. In addition, since the IGBT 43 is in the energized state when the MOSFET 41 is turned off, the MOSFET 41 does not receive a high voltage (rated voltage).

[0064] In addition, although the thyristor 40 has a characteristic of continuing the on state as long as the current (holding current) flows even if the gate is turned off, since the current flowing through the thyristor 40 is diverted to the IGBT 43 side by turning off the MOSFET 41, the current flowing through the thyristor 40 is zero and the thyristor 40 is in the off state. Therefore, even if a circuit for forcibly turning off the thyristor 40 by passing a counteracting current through the thyristor 40 is not provided, for example, the thyristor 40 can be turned off.

[0065] In addition, in the present embodiment, the control unit 5 is configured to control the IGBT 43 to be turned off after the current flowing through the series circuit of the thyristor 40 and the MOSFET 41 is diverted to the IGBT 43 side by controlling the MOSFET 41 to be turned off, thereby stopping the current flowing through the thyristor 40, and then controlling the IGBT 43 to be turned off, thereby controlling the current cutoff unit 4 to be cut off. Specifically, the control unit 5 is configured to control the IGBT 43 to be turned off after the value of the current flowing through the thyristor 40 becomes zero.

[0066] In detail, Figure 2 As shown in FIG. 1 , the control unit 5 is configured to control the IGBT 43 to be turned off after a time t equal to or longer than the turn-off time of the thyristor 40 has passed since the control to turn off the MOSFET 41 was performed, thereby controlling the current cutoff unit 4 to be cut off. Specifically, after a time t has passed since the gate cutoff signal was sent to the MOSFET 41 and the thyristor 40, respectively, the gate cutoff signal is sent to the IGBT 43. In addition, when the turn-off time of the thyristor 40 is, for example, 0.5 ms to 1 ms, it is preferable to set the time t to about twice the turn-off time of the thyristor 40, that is, about 1 ms to 2 ms.

[0067] Moreover, if Figure 6 As shown in FIG. 1 , during the period D after the IGBT 43 is turned off, no current flows through the IGBT 43. Figure 2 As shown in (d) to (f), during period D, the output current of the current cut-off unit 4 (refer to Figure 2 (d)), the current flowing through the thyristor 40 (refer to Figure 2 (e)) and the current flowing through the IGBT 43 (refer to Figure 2 (f)) are zero. Thus, the current cutoff control by the current cutoff unit 4 is completed. When the IGBT 43 is turned off, the IGBT 43 and the thyristor 40 are subjected to the rated voltage, respectively, while the MOSFET 41 is subjected to almost no voltage.

[0068] In addition, when power is not supplied from the system 101 during a power outage or the like, the DC power of the power storage unit 2 is supplied to the load 103. In this case, the control unit 5 is configured to control the current flowing from the power storage unit 2 to be turned on and off by the current cutoff unit 4. The control method for turning on and off the current from the power storage unit 2 is similar to the above-mentioned method for turning on and off the current from the rectifier 1 (see Figure 2 )Similarly, detailed description is omitted.

[0069] Furthermore, since the current flowing through the current cutoff portion 4 is cut off by turning off the IGBT 43 as a semiconductor switching element, no arc is generated, unlike when the current is cut off by a mechanical switch alone. Therefore, there is no need to provide a separate structure for forcibly eliminating the arc, and the current can be cut off at a high speed.

[0070] Furthermore, when a mechanical switch is used, it is generally more difficult to extinguish a DC arc than an AC arc, so the switches that can be selected are limited. Therefore, by using the IGBT 43 as a semiconductor switching element to cut off the current, the problem of limited selection of elements (switches) can be solved.

[0071] In addition, unlike the case where the conduction state continues for a certain period of time due to arcing of a mechanical switch, there is no need to provide a fuse component etc. for overcurrent protection. Thus, the labor and time of replacing the fuse component etc. when it deteriorates over the years can be saved.

[0072] [Effects of this embodiment]

[0073] In this embodiment, the following effects can be obtained.

[0074] In the present embodiment, as described above, the current cut-off unit 4 includes: a series circuit having a thyristor 40 having a withstand voltage greater than the rated voltage of the DC voltage and a self-extinguishing MOSFET 41 having a withstand voltage less than the rated voltage, the MOSFET 41 being connected in series with the thyristor 40 on the load 103 side; and a self-extinguishing IGBT 43 having a withstand voltage greater than the rated voltage, connected in parallel with the series circuit. In addition, the conduction loss of each of the thyristor 40 and the MOSFET 41 is smaller than the conduction loss of the IGBT 43. Furthermore, the DC power supply device 100 is configured as follows: the control unit 5 performs control to turn off the IGBT 43 after simultaneously performing control to turn off the thyristor 40 and control to turn off the MOSFET 41.

[0075] As a result, the current that was supposed to flow to the thyristor 40 and the MOSFET 41 is diverted to the IGBT 43, so the IGBT 43 can be turned off in a state where all the current flows to the IGBT 43. Here, since the IGBT 43 does not generate an arc when it is turned off, it is not necessary to use the charging energy of the capacitor to flow a superimposed current to the IGBT 43 in order to quickly turn the IGBT 43 off. Therefore, by performing control as described above, the fault current can be cut off at a high speed by the IGBT 43 without using a capacitor. As a result, the DC power supply device 100 can be miniaturized while cutting off the fault current at a high speed.

[0076] In addition, by connecting the series circuit of the thyristor 40 and the MOSFET 41, which have a relatively small conduction loss compared to the IGBT 43, to the IGBT 43 in parallel, at least a part of the current can also flow through the series circuit side having a relatively small conduction loss, unlike the case where only the IGBT 43 is provided. As a result, the conduction loss (power consumption) can be suppressed compared to the case where only the IGBT 43 is provided. As a result, the accident current can be cut off at a high speed while suppressing the increase of the conduction loss, and the DC power supply device 100 can be miniaturized.

[0077] In addition, the current that is to flow to the thyristor 40 and the MOSFET 41 is diverted to the IGBT 43, thereby enabling the IGBT 43 to be turned off in a state where no current flows through the thyristor 40 and the MOSFET 41. Thus, when the IGBT 43 is set to the off state, the IGBT 43 and the thyristor 40 are subjected to the rated voltage of the DC power supply device 100, while on the other hand, since the thyristor 40 provided at the front stage of the MOSFET 41 is in the off state, the voltage borne by the MOSFET 41 is substantially zero. As a result, it is possible to suppress the MOSFET 41 from being subjected to a voltage (rated voltage) above the withstand voltage, thereby suppressing the MOSFET 41 from being destroyed. In addition, since the withstand voltages of the thyristor 40 and the MOSFET 41 are each above the rated voltage, neither the thyristor 40 nor the MOSFET 41 is destroyed. Thus, it is possible to suppress the destruction of the element of the current cutoff unit 4 (MOSFET 41).

[0078] Here, when there is a time difference between the control of turning off the thyristor 40 and the control of turning off the MOSFET 41, the control of turning off the IGBT 43 is delayed according to the time difference, so the time for the current to flow to the IGBT 43 is increased. By performing the control of turning off the thyristor 40 and the control of turning off the MOSFET 41 at the same time, the delay in the control of turning off the IGBT 43 can be suppressed, and the increase in the time for the current to flow to the IGBT 43 can be suppressed. Here, the size of the IGBT 43 is determined by the energizable time. Therefore, by suppressing the increase in the time for the current to flow to the IGBT 43, the size of the IGBT 43 can be suppressed.

[0079] In addition, in the present embodiment, as described above, the DC power supply device 100 is configured as follows: the control unit 5 performs control to cut off the current cutoff unit 4 as follows: the control to cut off the MOSFET 41 is performed so that the current flowing through the series circuit of the thyristor 40 and the MOSFET 41 is diverted to the IGBT 43 side, and after the current no longer flows through the thyristor 40, the control to cut off the IGBT 43 is performed. As a result, it is possible to prevent the IGBT 43 from being cut off while the current is still flowing in the series circuit of the thyristor 40 and the MOSFET 41. As a result, the thyristor 40 can be reliably set to the cutoff state when the IGBT 43 is cut off. As a result, it is possible to more reliably prevent the MOSFET 41 from being subjected to a high voltage (rated voltage).

[0080] In addition, in the present embodiment, as described above, the DC power supply device 100 is configured as follows: the control unit 5 controls the IGBT 43 to be turned off after a time t equal to or longer than the turn-off time of the thyristor 40 has elapsed since the control to turn off the MOSFET 41 was performed, thereby controlling the current cutoff unit 4 to be turned off. As a result, the control to turn off the IGBT 43 can be performed more reliably after the current no longer flows through the thyristor 40.

[0081] In addition, in the present embodiment, as described above, the DC power supply device 100 is configured as follows: the control unit 5 controls the thyristor 40 and the MOSFET 41 to turn on after controlling the IGBT 43 to turn on, thereby controlling the current cutoff unit 4 to turn on. As a result, it is possible to suppress the thyristor 40 and the MOSFET 41 from turning on during the period when the IGBT 43 is turned off, and thus it is possible to suppress the high voltage (rated voltage of the DC power supply device 100) from being applied to the MOSFET 41.

[0082] In addition, in the present embodiment, as described above, the control unit 5 is configured to control the current cutoff unit 4 to be turned on by turning on the thyristor 40 and the MOSFET 41 after the IGBT 43 is turned on and the output voltage of the current cutoff unit 4 increases, and after the increase in the output voltage stops, thereby controlling the current cutoff unit 4 to be turned on. Here, the voltage received by the IGBT 43 decreases in accordance with the increase in the output voltage of the current cutoff unit 4. Therefore, after the increase in the output voltage of the current cutoff unit 4 stops, the thyristor 40 and the MOSFET 41 are controlled to be turned on, and the thyristor 40 and the MOSFET 41 can be turned on after the voltage received by the IGBT 43 becomes minimum. As a result, since the MOSFET 41 connected in parallel with the IGBT 43 also receives a voltage of the same magnitude as the voltage received by the IGBT 43, it is possible to suppress the MOSFET 41 from being applied with a high voltage.

[0083] In addition, in the present embodiment, as described above, the DC power supply device 100 is configured as follows: the on-state voltage V F The total value of the on-voltage Vth of the thyristor 40 and the on-voltage Vce of the IGBT 43 is greater than the on-voltage Vth of the thyristor 40 and the on-voltage V DS As a result, the current flowing through the series circuit of the diode element 42 and the IGBT 43, which have a relatively large total value of the on-state voltage, can be relatively small. As a result, the heat generated by the diode element 42 and the IGBT 43 can be relatively small.

[0084] In addition, since the conduction loss of each of the thyristor 40 and the MOSFET 41 is smaller than the conduction loss of the IGBT 43, the on-resistance of each of the thyristor 40 and the MOSFET 41 is smaller than the on-resistance of the IGBT 43. Therefore, by passing a current larger than the current flowing through the series circuit of the diode element 42 and the IGBT 43 through the thyristor 40 and the MOSFET 41 having relatively small on-resistance, an increase in the heat generated by the thyristor 40 and the MOSFET 41 can be suppressed as much as possible. As a result, an increase in the heat generated by the current interruption unit 4 as a whole can be suppressed.

[0085] In addition, in the present embodiment, as described above, the DC power supply device 100 is configured in such a manner that, when the DC power of the power storage unit 2 is supplied to the load 103, the control unit 5 simultaneously controls the thyristor 40 to be turned off and the MOSFET 41 to be turned off, and then controls the IGBT 43 to be turned off. Thus, it is possible to suppress the increase in conduction loss when the current is conducted and suppress the destruction of the elements of the current cutoff unit 4.

[0086] In addition, in the present embodiment, as described above, the DC power supply device 100 is configured as follows: the elements of the current cutoff portion 4 include the thyristor 40, the MOSFET 41, and the IGBT 43. Therefore, since the on-voltage of the thyristor is relatively low, by using the thyristor 40 as the thyristor 40, the increase in conduction loss when the current is turned on (during normal operation of the DC power supply device 100) can be effectively suppressed. In addition, since the IGBT switches at a relatively high speed and has a high withstand voltage, by using the IGBT 43 as the IGBT 43, the current can be cut off at a high speed, and even when the IGBT 43 is subjected to a high voltage (rated voltage), the destruction of the IGBT 43 can be suppressed. In addition, since the conduction loss of the MOSFET is relatively low, by using the MOSFET 41 as the MOSFET 41, the increase in conduction loss when the current is turned on (during normal operation of the DC power supply device) can be more effectively suppressed. In addition, since MOSFET switches at a relatively high speed, the current flowing in the DC circuit of thyristor 40 and MOSFET 41 can be relatively quickly diverted to IGBT 43 when current is cut off. As a result, the time required for current cutoff unit 4 to cut off the current can be shortened.

[0087] [Modifications]

[0088] In addition, all aspects of the embodiments disclosed this time should be considered to be illustrative rather than restrictive. The scope of the present invention is not shown by the description of the above embodiments but by the claims, and the scope of the present invention also includes all changes (modifications) within the meaning and scope equivalent to the claims.

[0089] For example, in the above embodiment, an example is shown in which the control of turning off the IGBT 43 (semiconductor switching element) is performed after the control of turning off the thyristor 40 (series switching element) and the control of turning off the MOSFET 41 (conduction switching element) are performed at the same time, but the present invention is not limited to this. For example, the control unit 5 may control the thyristor 40, the MOSFET 41, and the IGBT 43 to turn off in this order, thereby performing the control of cutting off the current cutoff unit 4. In addition, when the load 103 is powered by the power of the power storage unit 2, the control of turning off the thyristor 40, the MOSFET 41, and the IGBT 43 in this order may also be performed.

[0090] In addition, in the above-mentioned embodiment, an example of providing a thyristor 40 as a switching element is shown, but the present invention is not limited to this. For example, a mechanical switch may be provided instead of the thyristor 40. In this case, the current is commutated by turning off the MOSFET 41, thereby making it easy to make the current flowing through the mechanical switch zero, so that the arc generated by the mechanical switch when the mechanical switch is turned off can be suppressed. As a result, when a mechanical switch is used, the increase in the time required for current cutting can also be suppressed. In addition, a bipolar transistor may be provided instead of the thyristor 40. In addition, the selection of a mechanical switch instead of the thyristor 40 can further reduce power consumption.

[0091] In addition, in the above embodiment, the control unit 5 performs control to turn on the thyristor 40 (series switching element) and the MOSFET 41 (conduction switching element) after the increase of the output voltage of the current cutoff unit 4 stops, but the present invention is not limited to this. For example, the control unit 5 may also perform control to turn on the thyristor 40 and the MOSFET 41 when the output voltage has become larger than a predetermined threshold value even though the output voltage is in the middle of increasing.

[0092] In addition, in the above embodiment, an example in which the MOSFET 41 is provided as the conduction switching element is shown, but the present invention is not limited to this. For example, a mechanical switch may be provided instead of the MOSFET 41.

[0093] In the above embodiment, an example in which the IGBT 43 is provided as a switching element is shown, but the present invention is not limited to this. For example, a SiC-MOSFET may be provided instead of the IGBT 43 .

[0094] Description of Reference Numerals

[0095] 1: rectifier; 2: power storage unit; 4: current cut-off unit; 5: control unit; 40: thyristor (series switch element); 41: MOSFET (conduction switch element); 42: diode element; 43: IGBT (semiconductor switch element); 100: DC power supply device; 101: system (AC voltage source); 103: load; t: time (specified time); Vce: turn-on voltage (turn-on voltage of semiconductor switch element); V DS : On-voltage (the on-voltage of the conducting switching element); V F V: On-state voltage (on-state voltage of diode element); Vth: On-state voltage (on-state voltage of switch element).

Claims

1. A DC power supply device, comprising: a rectifier which converts an AC input voltage supplied from an AC voltage source into a DC voltage; a current cutoff unit for performing electrical connection and electrical cutoff between the rectifier and a load; as well as a control unit that controls the rectifier and the current cutoff unit, in, The current cut-off unit includes: a series circuit including a series switch element having a withstand voltage greater than a rated voltage of the DC voltage and a self-arc extinguishing conduction switching element having a withstand voltage less than the rated voltage, the conduction switching element being connected in series with the series switch element on the load side; as well as A self-arc extinguishing semiconductor switching element having a withstand voltage greater than the rated voltage is connected in parallel with the series circuit, The conduction loss of each of the series switch element and the conduction switching element is smaller than the conduction loss of the semiconductor switch element. The control unit is configured to control the series switch element to be disconnected and then control the conduction switching element to be disconnected, or to control the series switch element, the conduction switching element, and the semiconductor switch element to be disconnected in this order, thereby controlling the current cutoff unit to be cut off. The current cutoff unit includes a diode element connected in parallel with the series circuit and connected in series with the semiconductor switch element. The total value of the on-state voltage of the diode element and the on-state voltage of the semiconductor switch element is greater than the total value of the on-state voltage of the series switch element and the on-state voltage of the conduction switching element. As a result, the current value flowing through the diode element and the semiconductor switch element is smaller than the current value flowing through the series switch element and the conduction switching element.

2. The DC power supply device according to claim 1, wherein: The control unit is configured to control the series switching element to be turned off and the conduction switching element to be turned off at the same time, and then control the semiconductor switching element to be turned off, thereby controlling the current cutoff unit to be cut off.

3. The DC power supply device according to claim 1 or 2, wherein: The control unit is configured to control the cutting off of the current cut-off unit in the following manner: the conduction switching element is controlled to be disconnected so that the current flowing through the series circuit of the series switch element and the conduction switching element is diverted to the semiconductor switch element side, and after the current no longer flows through the series switch element, the semiconductor switch element is controlled to be disconnected.

4. The DC power supply device according to claim 3, wherein: The conduction switching element is configured to be capable of switching at a higher speed than the series switching element. The control unit is configured to control the semiconductor switch element to turn off after a predetermined time equal to or longer than an off time of the series switch element has elapsed since control is performed to turn off the conduction switching element, thereby controlling the current cutoff unit to be cut off.

5. The DC power supply device according to claim 1 or 2, wherein: The control unit is configured to control the series switching element and the conduction switching element to be turned on after performing control to turn on the semiconductor switching element, thereby performing control to turn on the current interruption unit.

6. The DC power supply device according to claim 5, wherein: The control unit is configured to control the series switching element and the conduction switching element to be turned on, thereby controlling the current cutoff unit to be turned on, after the semiconductor switching element is turned on to increase the output voltage of the current cutoff unit and the increase in the output voltage stops.

7. The DC power supply device according to claim 1 or 2, wherein: further comprising a power storage unit for storing the DC power converted by the rectifier, The control unit is configured to, when supplying DC power of the storage unit to the load, control to disconnect the semiconductor switch element after simultaneously controlling to disconnect the series switch element and the conduction switching element, or control to disconnect the series switch element, the conduction switching element, and the semiconductor switch element in this order, thereby controlling to cut off the current flowing from the storage unit to the load using the current cutoff unit.

8. The DC power supply device according to claim 1 or 2, wherein: The series switching element, the conduction switching element, and the semiconductor switching element include a thyristor, a MOSFET, and an IGBT, respectively.

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