DC circuit breaker

Abstract

To provide a DC circuit breaker that does not require precharging of a storage circuit connected to a main switch.SOLUTION: A DC circuit breaker includes a main switch and a series circuit connected in parallel to the main switch and including a power storage circuit and a commutation switch. After the main switch is opened, the commutation switch is set to a closed state, thereby commutating the discharge current of the main switch to the power storage circuit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a DC circuit breaker.

Background Art

[0002] Patent Document 1 below discloses a commutation type DC circuit breaker. As shown in FIG. 1 of Patent Document 1 and the like, this commutation type DC circuit breaker includes a main circuit having a main switch for connecting between a DC power supply and a load to turn on and off the main circuit current, a commutation circuit having a commutation capacitor connected in parallel to the main circuit so that a commutation current can be superimposed, a current direction detection unit for detecting the direction in which an accident current flows, a commutation direction switching switch for switching the circuit so that the first half wave of the commutation current flows in a direction to cancel the accident current according to the detection result of the current direction detection unit, and a control unit for controlling the main switch to open its poles when the absolute value of the accident current exceeds a predetermined value.

[0003] When such a commutation type DC circuit breaker has an accident and opens the main switch, a commutation current is injected from the commutation capacitor into the main circuit by connecting the pre-charged commutation capacitor in parallel to the main circuit having a saturable reactor. In this commutation type DC circuit breaker, the arc generated between the electrodes of the main switch is extinguished by the commutation current.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, the above background art extinguishes an arc by transferring a transfer current from a commutation capacitor functioning as a power storage circuit to a main circuit, and it is necessary to pre-charge (pre-charge) the commutation capacitor (power storage circuit). That is, the above background art has an essential component of a charging circuit for pre-charging the power storage circuit.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a DC circuit breaker that does not require pre-charging of a power storage circuit connected to a main switch.

Means for Solving the Problems

[0007] In order to achieve the above object, in the present invention, as a first solution means related to a DC circuit breaker, a main switch and a series circuit connected in parallel with the main switch and including a power storage circuit and a commutation switch are provided, and after opening the main switch, the commutation switch is set to a closed state, thereby transferring the discharge current of the main switch to the power storage circuit.

[0008] In the present invention, as a second solution means related to a DC circuit breaker, in the above first solution means, a unidirectional coupling circuit is further provided, one end of which is connected to the input side of the main switch, the other end of which is connected to one end of the series circuit, and which allows the current to flow from the main switch to the series circuit and blocks the current from flowing from the series circuit to the main switch.

[0009] In the present invention, as a third solution means related to a DC circuit breaker, in the above first or second solution means, a discharge circuit for discharging the charge of the power storage circuit is further provided.

[0010] In the present invention, as a fourth solution means related to a DC circuit breaker, in any of the above first to third solution means, an overvoltage protection circuit for protecting the power storage circuit from overvoltage is further provided.

[0011] In the present invention, as a fifth solution means related to a DC circuit breaker, in any of the first to fourth solution means, a means of further providing a current-limiting reactor between the DC circuit breaker and an external DC power source is adopted.

[0012] In the present invention, as a sixth solution means related to a DC circuit breaker, in any of the first to fifth solution means, a means of adopting that the commutation switch is a semiconductor switch circuit is adopted.

[0013] In the present invention, as a seventh solution means related to a DC circuit breaker, in any of the first to sixth solution means, a means of further providing a current-limiting circuit for limiting the energizing current of the main switch is adopted.

[0014] In the present invention, as an eighth solution means related to a DC circuit breaker, in any of the first to seventh solution means, a control device for controlling the main switch and the commutation switch is further provided, and the control device adopts a means of setting the commutation switch to a closed state after opening the main switch.

[0015] In the present invention, as a ninth solution means related to a DC circuit breaker, in the eighth solution means, the control device adopts a means of opening the main switch when a ground fault detection signal indicating a ground fault occurrence at the power supply destination of the DC power is input, and setting the commutation switch to a closed state when a predetermined time has elapsed since the opening.

[0016] In the present invention, as a tenth solution means related to a DC circuit breaker, in the first or second solution means, a means of adopting that the series circuit includes a commutation promotion circuit for promoting the commutation of the discharge current to the power storage circuit is adopted.

[0017] In the present invention, as an eleventh solution means related to a DC circuit breaker, in the tenth solution means, a means of adopting that the commutation promotion circuit promotes the commutation of the discharge current to the power storage circuit by increasing the terminal voltage of the power storage circuit is adopted.

[0018] In the present invention, as a twelfth solution means related to a DC circuit breaker, in the eleventh solution means, the commutation promotion circuit adopts a means of increasing the voltage between the terminals of the power storage circuit by charging the auxiliary power storage circuit with a polarity opposite to that of the DC power to be interrupted.

[0019] In the present invention, as a thirteenth solution means related to a DC circuit breaker, in the twelfth solution means, the commutation promotion circuit adopts a means of charging the auxiliary power storage circuit with a reverse polarity using the DC power.

[0020] In the present invention, as a fourteenth solution means related to a DC circuit breaker, in the tenth solution means, the series circuit adopts a means of including the power storage circuit, the commutation switch, and the commutation promotion circuit, and a plurality of second series circuits connected in parallel to each other.

[0021] In the present invention, as a fifteenth solution means related to a DC circuit breaker, in the first or second solution means, the series circuit adopts a means of including a plurality of the power storage circuits connected in parallel to each other.

Advantages of the Invention

[0022] According to the present invention, it is possible to provide a DC circuit breaker that does not require pre-charging of a power storage circuit connected to a main switch.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings. 〔First Embodiment〕 First, the first embodiment of the present invention will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, the capacitor commutation current-limiting DC circuit breaker A according to the first embodiment is a DC circuit breaker used for high-voltage direct current transmission (HVDC: High Voltage Direct Current), and is provided between a high-voltage DC power supply V and a load. Hereinafter, the name "capacitor commutation current-limiting DC circuit breaker A" will be abbreviated as "DC circuit breaker A".

[0025] The high-voltage DC power supply V is a series circuit of a voltage source E and a current-limiting reactor L as shown in the figure. The voltage source E is a power generation device that generates DC power of a predetermined voltage, for example, a solar cell panel. The negative electrode of this voltage source E is grounded, and the positive electrode is connected to one end of the current-limiting reactor L. The current-limiting reactor L has one end connected to the positive electrode of the voltage source E and the other end connected to the input terminal of the DC circuit breaker A. This current-limiting reactor L is a passive element that represents the output impedance of the high-voltage DC power supply V.

[0026] The load is the power supply destination of the DC power in the high-voltage DC power supply V. The DC power output from the high-voltage DC power supply V is supplied to this load via the DC circuit breaker A. When a fault detection signal is input from the outside, the DC circuit breaker A according to the first embodiment cuts off the transmission of high-voltage DC power from the high-voltage DC power supply V to the load. The above fault detection signal is an electrical signal indicating the occurrence of a fault in the load.

[0027] As shown in FIG. 2, the DC circuit breaker A includes a main switch 1, a breaking section current-limiting device 2, a commutation current-limiting capacitor 3, a transistor 4, a bias resistor 5, a diode 6, a discharge resistor 7, a discharge switch 8, a varistor 9, and a control device 10. The DC circuit breaker A also includes an input terminal IN, an output terminal OUT, and a control terminal CNT.

[0028] First, the three terminals will be described. The input terminal IN is connected to the output terminal of the high-voltage DC power supply V outside the DC circuit breaker A, that is, the other end of the current-limiting reactor L. Also, the input terminal IN is connected to the breaking section current-limiting device 2 and the diode 6 inside the DC circuit breaker A. High-voltage DC power is input to this input terminal IN from the high-voltage DC power supply V.

[0029] The output terminal OUT is connected to the input end of the load outside the DC circuit breaker A. Also, the output terminal OUT is connected to the main switch 1 and the transistor 4 inside the DC circuit breaker A. The control terminal CNT is connected to the fault detection device outside the DC circuit breaker A and is connected to the control device 10 inside the DC circuit breaker A. A fault detection signal is input to this control terminal CNT from the fault detection device.

[0030] The main switch 1 is provided between the high-voltage DC power supply V and the load together with the interrupting section current-limiting device 2. That is, one contact of the main switch 1 is connected to one end of the interrupting section current-limiting device 2, the other contact is connected to the output terminal OUT and the emitter terminal of the transistor 4, and the control terminal is connected to the first output terminal in the control device 10. The main switch 1 is a mechanical switching device having sufficient energization performance in the closed state and closes or opens based on the main control signal input to the control terminal from the control device 10.

[0031] That is, when a main control signal instructing the main switch 1 to close is input from the control device 10, the main switch 1 closes to connect the input terminal IN and the output terminal OUT. Also, when a main control signal instructing the main switch 1 to open is input from the control device 10, the main switch 1 opens to disconnect the connection between the input terminal IN and the output terminal OUT.

[0032] The interrupting section current-limiting device 2 is connected in series with the main switch 1. One end of this interrupting section current-limiting device 2 is connected to one contact of the main switch 1, and the other end is connected to the input terminal IN and the anode terminal of the diode 6. The interrupting section current-limiting device 2 limits the energization current between the input terminal IN and the output terminal OUT via the main switch 1. This interrupting section current-limiting device 2 corresponds to the current-limiting circuit of the present invention. However, when sufficient arc voltage is generated to divert the arc current when arc discharge occurs in the main switch 1, the arc discharge serves the function of the interrupting section current-limiting device 2.

[0033] The commutation current-limiting capacitor 3 has a predetermined capacitance. One end thereof is connected to one end of the bias resistor 5, one end of the discharge resistor 7, one end of the varistor 9, and the cathode terminal of the diode 6, and the other end is connected to the collector terminal of the transistor 4, the other end of the bias resistor 5, one contact of the discharge switch 8, and the other end of the varistor 9.

[0034] This commutation current-limiting capacitor 3, together with the transistor 4 and the bias resistor 5, forms a series circuit 11. As shown in the figure, this series circuit 11 is connected in parallel to the main switch 1. The commutation current-limiting capacitor 3 is charged by the current (commutation current It) commuted from the main switch 1 via the diode 6. Note that the commutation current It will be described in detail in the operation explanation below. Such a commutation current-limiting capacitor 3 corresponds to the power storage circuit of the present invention.

[0035] The transistor 4 is an NPN bipolar transistor as shown in the figure. The collector terminal of this transistor 4 is connected to the other end of the commutation current-limiting capacitor 3, the other end of the bias resistor 5, one contact of the discharge switch 8, and the other end of the varistor 9, and the emitter terminal is connected to the other contact of the main switch 1 and the output terminal OUT. Also, the base terminal of the transistor 4 is connected to the second output end of the control device 10.

[0036] This transistor 4 is connected in series to the commutation current-limiting capacitor 3. Also, this transistor 4, together with the commutation current-limiting capacitor 3 and the bias resistor 5, forms a series circuit 11. Such a transistor 4 is set to the ON state (conducting state) / OFF state (non-conducting state) based on the on / off control signal input to the base terminal from the control device 10.

[0037] This transistor 4 has a bias resistor 5 for DC bias connected between the collector terminal and the input terminal IN to which high-voltage DC power is supplied from the outside, and functions as a semiconductor switch. When a high (H)-level on-off control signal is input from the control device 10, the transistor 4 turns on (conducts), and sets the commutation current-limiting capacitor 3 to a state where charging based on the commutation current It described above is possible.

[0038] Also, when a low (L)-level on-off control signal is input from the control device 10, the transistor 4 turns off (non-conducts), and sets the commutation current-limiting capacitor 3 to a state where charging based on the commutation current It is impossible. Such a transistor 4, together with the bias resistor 5, constitutes a semiconductor switch circuit. This semiconductor switch circuit corresponds to the commutation switch of the present invention.

[0039] One end of the bias resistor 5 is connected to the anode terminal of the diode 6, one end of the commutation current-limiting capacitor 3, one end of the discharge resistor 7, and one end of the varistor 9, and the other end is connected to the collector terminal of the transistor 4, the other end of the commutation current-limiting capacitor 3, one of the contacts in the discharge switch 8, and the other end of the varistor 9. This bias resistor 5 is a DC load in the transistor 4, and together with the transistor 4, constitutes the commutation switch of the present invention.

[0040] The anode terminal of the diode 6 is connected to the input terminal IN and the other end of the cut-off portion current-limiting device 2, and the cathode terminal is connected to one end of the commutation current-limiting capacitor 3, one end of the bias resistor 5, one end of the discharge resistor 7, and one end of the varistor 9. That is, the diode 6 is a semiconductor element whose anode terminal (one end) is connected to the input side of the main switch 1, the cathode terminal (the other end) is connected to one end of the series circuit 11, allows the current to flow from the main switch 1 to the series circuit 11, and blocks the current from flowing from the series circuit 11 to the main switch 1. Such a diode 6 corresponds to the unidirectional coupling circuit of the present invention.

[0041] The discharge resistor 7 has a predetermined resistance value (discharge resistance value), one end of which is connected to one end of the commutation current-limiting capacitor 3, one end of the bias resistor 5, the cathode terminal of the diode 6, and one end of the varistor 9, and the other end is connected to the other contact in the discharge switch 8. This discharge resistor 7 constitutes a discharge circuit 12 together with the discharge switch 8.

[0042] One contact of the discharge switch 8 is connected to the other end of the commutation current-limiting capacitor 3, the collector terminal of the transistor 4, the other end of the bias resistor 5, and the other end of the varistor 9, the other contact is connected to the other end of the discharge resistor 7, and the control terminal is connected to the third output terminal in the control device 10. The discharge switch 8 constitutes a discharge circuit 12 together with the discharge resistor 7.

[0043] The discharge switch 8 is a mechanical switch whose open / closed state is set based on a discharge control signal input from the control device 10. That is, the discharge switch 8 is set to the open state when a discharge control signal instructing the open state is input from the control device 10. Also, the discharge switch 8 is set to the closed state when a discharge control signal instructing the closed state is input from the control device 10.

[0044] The discharge circuit 12 provided with such a discharge resistor 7 and a discharge switch 8 is provided to forcibly discharge the charge of the commutation current-limiting capacitor 3 charged by the commutation current It). That is, the discharge switch 8 is set to the open state by the discharge control signal in the steady state, but is set to the closed state by the discharge control signal when forcibly discharging the commutation current-limiting capacitor 3. As a result, the charge of the commutation current-limiting capacitor 3 is discharged and consumed by the discharge resistor 7.

[0045] One end of the varistor 9 is connected to one end of the commutation current-limiting capacitor 3, one end of the bias resistor 5, the cathode terminal of the diode 6, and one end of the discharge resistor 7, and the other end is connected to the other end of the commutation current-limiting capacitor 3, the collector terminal of the transistor 4, the other end of the bias resistor 5, and one contact in the discharge switch 8.

[0046] This varistor 9 is connected in parallel to the commutation current-limiting capacitor 3, the bias resistor 5, and the discharge circuit 12, and protects the commutation current-limiting capacitor 3, the bias resistor 5, and the discharge circuit 12 from overvoltage caused by the inductance of the current-limiting reactor L. Such a varistor 9 corresponds to the overvoltage protection circuit of the present invention.

[0047] The control device 10 has one input terminal and three output terminals. The input terminal of the control device 10 is connected to the control terminal CNT, the first output terminal is connected to the control terminal of the main switch 1, the second output terminal is connected to the base terminal of the transistor 4, and the third output terminal is connected to the control terminal of the discharge switch 8.

[0048] A fault detection signal is input to this control device 10 from the control terminal CNT. The control device 10 generates a main control signal based on the fault detection signal and outputs it from the first output terminal to the control terminal of the main switch 1. Also, the control device 10 generates an opening / closing control signal based on the fault detection signal and outputs it from the second output terminal to the base terminal of the transistor 4. Furthermore, the control device 10 generates a discharge control signal based on the fault detection signal and outputs it from the third output terminal to the control terminal of the discharge switch 8.

[0049] Although details will be described later, when a ground fault detection signal is input to the control device 10 from the control terminal CNT, the control device 10 opens the main switch 1 in advance, and when a predetermined time has elapsed since the opening of the main switch 1, it sets the transistor 4 to the ON state (conducting state), that is, closes the commutation switch, thereby extinguishing the arc discharge in the main switch 1.

[0050] Next, the operation of the DC circuit breaker A according to the first embodiment will be described in detail with reference to FIGS. 3 and 4.

[0051] Figures 3 and 4 show the operation of the DC circuit breaker A during the period from the occurrence of a fault to the interruption of power transmission to the high-voltage DC power load (interruption period). Figure 3 shows the simulation results in an ideal circuit indicating the changes in the current flowing between the input terminal IN and the output terminal OUT (energization current) and the voltage at the input terminal IN (input terminal voltage) during this interruption period. In this Figure 3, the solid line indicates the change in the energization current, and the dashed line indicates the change in the input terminal voltage.

[0052] This Figure 3 is a simulation result with the input terminal voltage, which is a simulation parameter as an example, set to 5 kV (kilovolts) and the energization current, which is also a parameter, set to 6 kA (kiloamperes). Also, Figure 4 shows an enlarged view of the input terminal voltage when the transistor 4 is switched from the OFF state (non-conducting state) to the ON state (conducting state) during the interruption period.

[0053] The steady state in the DC circuit breaker A is a state where the high-voltage DC power input from the high-voltage DC power supply V to the input terminal IN is output to the output terminal OUT and transmitted to the load. That is, in the steady state, the control device 10 sets the main switch 1 to the closed state, sets the transistor 4 to the OFF state (non-conducting state), and sets the discharge switch 8 to the open state. Also, the commutation current-limiting capacitor 3 is set to a discharged state where it has not been pre-charged by the discharge circuit 12.

[0054] In such a steady state, as shown in Figures 3 and 4, for example, when a fault occurs at time t0, the occurrence of the fault is detected by an external fault detection device, and a fault detection signal is input to the control terminal CNT. When the control device 10 receives the fault detection signal from the control terminal CNT, it promptly switches the main switch 1 from the closed state to the open state. In Figure 3, the opening of the main switch 1 is shown at time t1.

[0055] Here, as shown in FIG. 3, during the period from time t0 to time t1, due to the occurrence of a fault, the input terminal voltage drops to near the ground potential, and as this input terminal voltage drops, the energization current increases rapidly. Further, when the main switch 1 is switched from the closed state to the open state, arc discharge occurs between a pair of contacts in the main switch 1. This arc discharge has a discharge voltage of, for example, 130 V (volts).

[0056] That is, after time t1, the arc current due to the arc discharge is energized to the main switch 1. Therefore, when the main switch 1 is switched from the closed state to the open state, since arc discharge occurs between a pair of contacts in the main switch 1, the input terminal voltage is set to the discharge voltage of 130 V (volts), and the energization current continues to increase.

[0057] When the control device 10 switches the main switch 1 from the closed state to the open state, it then switches the transistor 4 from the OFF state (non-conducting state) to the ON state (conducting state). In FIGS. 3 and 4, the conduction of the transistor 4 is shown as time t2. When the transistor 4 conducts, the current-commutating current-limiting capacitor 3 is set to a state equivalent to being connected in parallel with the main switch 1.

[0058] As a result, the arc current flowing through the main switch 1 commutates to the current-commutating current-limiting capacitor 3. That is, the current-commutating current-limiting capacitor 3 is set to a discharged state in advance by the discharge circuit 12, and when the transistor 4 conducts, the input terminal voltage temporarily drops from 130 V (volts) to, for example, about 30 V (volts) as shown in FIG. 4, so that the arc current commutates from between a pair of contacts in the main switch 1 to the current-commutating current-limiting capacitor 3. Thereby, the arc discharge disappears.

[0059] When a period T elapses from the occurrence of the commutation of the arc current (time t2), as shown in FIG. 3, the energizing current converges near 0 (A). In FIG. 3, the time when the energizing current converges near 0 (A) is shown as t3. After that, the transistor 4 is switched to the OFF state (non-conducting state), and the current interruption is completed. After the current is interrupted, the discharge circuit 12 sets the commutation current-limiting capacitor 3 to the discharged state to prepare for re-energization.

[0060] Here, as shown in FIGS. 3 and 4, the input terminal voltage rises from the start of commutation to the commutation current-limiting capacitor 3 of the arc current (time t2). The rising speed of this input terminal voltage mainly depends on the magnitude of the capacitance in the commutation current-limiting capacitor 3 and the magnitude of the inductance in the current-limiting reactor L. That is, the rising speed of the input terminal voltage becomes lower as the capacitance of the commutation current-limiting capacitor 3 is larger.

[0061] According to the first embodiment, a main switch 1, a series circuit 11 including a commutation switch composed of a commutation current-limiting capacitor 3 (power storage circuit), a transistor 4, and a bias resistor 5 connected in parallel to the main switch 1, and after opening the main switch 1, setting the commutation switch to the closed state, the arc current (discharge current) of the main switch 1 is commutated to the commutation current-limiting capacitor 3 (power storage circuit), so it is possible to provide a DC circuit breaker A that does not require pre-charging of the commutation current-limiting capacitor 3 (power storage circuit) connected to the main switch 1.

[0062] 〔Second Embodiment〕 Subsequently, a second embodiment of the present invention will be described with reference to FIGS. 5 to 9. In FIGS. 5 to 7, the same components as those in FIG. 2 are denoted by the same reference numerals. Also, in FIGS. 6 and 7, the control device 10 and the discharge circuit 12 are omitted for convenience.

[0063] As shown in Fig. 5, the DC circuit breaker A1 according to the second embodiment includes a series circuit composed of a bias block B, a current-commutating switch 4A, and a capacitor current-limiting block C. That is, the series circuit in the second embodiment is connected in parallel to the main switch 1 and includes a bias block B in addition to the current-commutating switch 4A and the capacitor current-limiting block C that functions as a power storage circuit. Note that the current-commutating switch 4A and the capacitor current-limiting block C constitute a second series circuit D.

[0064] Regarding the capacitor current-limiting block C, this capacitor current-limiting block C is a parallel connection circuit of the current-commutating capacitor 3, the bias resistor 5, and the varistor 9 in the first embodiment. One end is connected to one contact of the main switch 1 and the input terminal IN, and the other end is connected to one contact of the current-commutating switch 4A.

[0065] The current-commutating switch 4A is a mechanical on-off switch. One contact of this current-commutating switch 4A is connected to the other end of the capacitor current-limiting block C, the other contact is connected to one end of the bias block B, and the control end is connected to the second output end of the control device 10. This current-commutating switch 4A closes or opens based on an on-off control signal input to the control end from the control device 10.

[0066] As shown in the figure, the bias block B is a parallel connection circuit of an auxiliary capacitor 13, an auxiliary diode 14, and a voltage source 15. One end is connected to the other contact of the current-commutating switch 4A, and the other end is connected to the other contact of the main switch 1 and the output terminal OUT.

[0067] In this bias block B, the auxiliary capacitor 13 has a predetermined capacitance. One end is connected to the anode terminal of the auxiliary diode 14 and the negative electrode of the voltage source 15, and the other end is connected to the cathode terminal of the auxiliary diode 14 and the positive electrode of the voltage source 15. This auxiliary capacitor 13 is charged with a polarity (negative polarity) opposite to the polarity (positive polarity) of the DC power supplied from the voltage source E of the high-voltage DC power supply V to the input terminal IN by the voltage source 15 connected in parallel.

[0068] The auxiliary diode 14 has its anode terminal connected to one end of the auxiliary capacitor 13 and the negative electrode of the voltage source 15, and its cathode terminal connected to the other end of the auxiliary capacitor 13 and the positive electrode of the voltage source 15. Although the details of the operation of the auxiliary diode 14 will be described later, this auxiliary diode 14 is provided to bypass the commutation current from the auxiliary capacitor 13.

[0069] The voltage source 15 has its negative electrode connected to one end of the auxiliary capacitor 13 and the anode terminal of the auxiliary diode 14, and its positive electrode connected to the other end of the auxiliary capacitor 13 and the cathode terminal of the auxiliary diode 14. This voltage source 15 charges the auxiliary capacitor 13 with a polarity opposite to the DC power of the voltage source E by outputting a predetermined negative voltage from the negative electrode.

[0070] Although the details will be described later, the bias block B in the second embodiment corresponds to the commutation promotion circuit of the present invention. Also, the auxiliary capacitor 13 in this bias block B corresponds to the auxiliary power storage circuit of the present invention. The bias block B has a function of promoting the commutation of the arc current (discharge current) of the main switch 1 to the commutation current limiting capacitor 3 (power storage circuit).

[0071] As shown in FIG. 6(a), in the DC circuit breaker A1 provided with such a bias block B, in the steady state, the main switch 1 is set to the closed state and the commutation switch 4A is set to the open state. In this state, a normal current Is flows between the input terminal IN and the output terminal OUT via the main switch 1.

[0072] When a fault detection signal is input to the control terminal CNT, as shown in FIG. 6(b), the main switch 1 is switched from the closed state to the open state, and the commutation switch 4A is switched from the open state to the closed state. By being switched from the closed state to the open state, an arc discharge occurs in the main switch 1, and a current Ia flows between the pair of electrodes.

[0073] When the commutation switch 4A is set to the closed state, the current Ia flows from the main switch 1 to the commutation current-limiting capacitor 3 and the auxiliary capacitor 13. That is, as shown in FIG. 7, a commutation current It obtained by commuting the current Ia of the main switch 1 flows through the series circuit including the commutation current-limiting capacitor 3, the commutation switch 4A, and the auxiliary capacitor 13.

[0074] Here, when the commutation switch 4A is set to the closed state, one end of the auxiliary capacitor 13 is connected to the other end of the commutation current-limiting capacitor 3. Since this auxiliary capacitor 13 is pre-charged by the voltage source 15 with a polarity opposite to the DC power of the voltage source E, a negative voltage is applied to the other end of the commutation current-limiting capacitor 3 by one end of the auxiliary capacitor 13.

[0075] As a result, the voltage across the terminals of the commutation current-limiting capacitor 3 when the commutation switch 4A is closed increases compared to the case where the auxiliary capacitor 13 is not provided, for example, the capacitor commutation current-limiting type DC circuit breaker A according to the first embodiment. That is, the voltage across the terminals of the commutation current-limiting capacitor 3 increases by the voltage across the terminals of the auxiliary capacitor 13 charged with the opposite polarity.

[0076] According to such a second embodiment, by charging the auxiliary capacitor 13 (auxiliary power storage circuit) with a polarity opposite to the DC power of the voltage source E to be interrupted, the voltage across the terminals of the commutation current-limiting capacitor 3 (power storage circuit) is increased. Therefore, it is possible to promote the commutation of the current Ia of the main switch 1 to the commutation current-limiting capacitor 3 more than in the first embodiment.

[0077] Note that the auxiliary capacitor 13 is gradually charged and restored with a polarity opposite to the DC power of the voltage source E, that is, the initial polarity, as time passes by the commutation current It, and the voltage at one end gradually rises. When the voltage at one end of the auxiliary capacitor 13 rises to the ON voltage of the auxiliary diode 14, the auxiliary diode 14 transitions from the OFF state to the ON state. As a result, the commutation current It flows through the auxiliary diode 14 instead of the auxiliary capacitor 13.

[0078] Figure 8(a) shows the first simulation result for the DC circuit breaker A1. The first simulation result shows the current waveform of the main switch 1 when a short-circuit fault occurs in the load at time 0 ms.

[0079] In the first simulation, the inductance of the current-limiting reactor L is set to 10 mH, the capacitance of the commutation current-limiting capacitor 3 is set to 20 μF, the capacitance of the auxiliary capacitor 13 is set to 20 μF, the parasitic inductance of the main switch 1 is set to 10 μH, the parasitic inductance of the capacitor current-limiting block C is set to 10 μH, the output voltage (power supply voltage) of the voltage source E is set to 20 kV, and the charging voltage (bias voltage) of the auxiliary capacitor 13 is set to 15 kV.

[0080] The first simulation result shows that when the main switch 1 is not opened and the commutation switch 4A is switched from the open state to the closed state at time 4 ms, a current zero occurs in the current Ia flowing through the main switch 1. That is, according to the DC circuit breaker A1 according to the second embodiment, when the main switch 1 is opened, the arc discharge can be extinguished at the first current zero in the current Ia.

[0081] Figure 8(b) shows the second simulation result for the DC circuit breaker A1. The second simulation result shows the current waveform (solid line) and voltage waveform (dashed line) of the main switch 1 when a transient voltage adjustment circuit is added in parallel with the main switch 1, the main switch 1 is opened at 2 ms, the commutation switch 4A is closed at 4 ms, and the arc discharge of the main switch 1 is extinguished at the first current zero.

[0082] In the second simulation, the inductance of the current-limiting reactor L was set to 10 mH, the capacitance of the commutation current-limiting capacitor 3 was set to 20 μF, the capacitance of the auxiliary capacitor 13 was set to 20 μF, the parasitic inductance of the main switch 1 was set to 10 μH, the parasitic inductance of the capacitor current-limiting block C was set to 10 μH, the capacitance of the transient voltage regulating circuit was set to 0.5 μF, the resistance value of the transient voltage regulating circuit was set to 10 Ω, the output voltage (power supply voltage) of the voltage source E was set to 20 kV, the charging voltage (bias voltage) of the auxiliary capacitor 13 was set to 15 kV, and the limiting voltage of the varistor 9 was set to 30 kV.

[0083] Such results of the second simulation indicate that when the main switch 1 opens, a negative-polarity voltage is generated due to the residual charge of the bias block B. Also, the results of the second simulation indicate that after the generation of the negative-polarity voltage, a positive-polarity voltage rise occurs due to the energization of the capacitor current-limiting block C.

[0084] Fig. 9(a) shows the results of the third simulation regarding the DC circuit breaker A1. In Fig. 9(a), the output current of the voltage source E is shown by a solid line, and the voltage generated in the DC circuit breaker A1 is shown by a dashed line. In the third simulation, a transient voltage regulating capacitor is added in parallel with the main switch 1.

[0085] In the third simulation, the inductance of the current-limiting reactor L was set to 10 mH, the capacitance of the commutation current-limiting capacitor 3 was set to 20 μF, the capacitance of the auxiliary capacitor 13 was set to 20 μF, the parasitic inductance of the main switch 1 was set to 10 μH, the parasitic inductance of the capacitor current-limiting block C was set to 10 μH, the capacitance of the transient voltage regulating capacitor was set to 0.5 μF, the output voltage (power supply voltage) of the voltage source E was set to 20 kV, the charging voltage (bias voltage) of the auxiliary capacitor 13 was set to 15 kV, and the limiting voltage of the varistor 9 was set to 30 kV.

[0086] The third simulation result shows that the arc discharge of the main switch 1 extinguishes at approximately 4.01 ms, and all the current supplied from the voltage source E flows into the capacitor current limiting block C. Also, the third simulation result shows that the commutation current It is limited by the voltage rise of the commutation current limiting capacitor 3, rises to a peak of 8 kA, then turns from increase to decrease, and is eventually interrupted.

[0087] Also, the third simulation result shows that the upper limit of the generated voltage in the DC circuit breaker A1 is limited to approximately 30 kV by the varistor 9. Furthermore, the third simulation result shows that after current interruption, voltage fluctuations occur due to the resonance between the current limiting reactor L and the transient voltage regulating capacitor, and eventually converge to the power supply voltage (20 kV).

[0088] Figure 9(b) shows the fourth simulation result regarding the DC circuit breaker A1. In Figure 9(b), the commutation current It flowing through the capacitor current limiting block C is shown by a solid line, and the voltage generated in the DC circuit breaker A1 is shown by a dashed line. In the fourth simulation, similar to the above-mentioned third simulation, a transient voltage regulating capacitor is added in parallel with the main switch 1.

[0089] In the fourth simulation, similar to the above-mentioned third simulation, the inductance of the current limiting reactor L is set to 10 mH, the capacitance of the commutation current limiting capacitor 3 is set to 20 μF, the capacitance of the auxiliary capacitor 13 is set to 20 μF, the parasitic inductance of the main switch 1 is set to 10 μH, the parasitic inductance of the capacitor current limiting block C is set to 10 μH, the capacitance of the transient voltage regulating capacitor is set to 0.5 μF, the output voltage (power supply voltage) of the voltage source E is set to 20 kV, the charging voltage (bias voltage) of the auxiliary capacitor 13 is set to 15 kV, and the limiting voltage of the varistor 9 is set to 30 kV.

[0090] The fourth simulation result shows that the arc discharge of the main switch 1 disappears at about 4.01 ms, and all the current supplied from the voltage source E flows into the capacitor current limiting block C. Also, the third simulation result shows that the commutation current It is limited by the voltage rise of the commutation capacitor 3, rises to a peak of 8 kA and then turns from increase to decrease, and is interrupted at the current zero point.

[0091] Here, the commutation current It is naturally interrupted depending on the type of the commutation switch 4A. That is, when the commutation switch 4A is a mechanical on-off switch with vacuum contacts or a thyristor, etc., the commutation current It is naturally interrupted. On the other hand, when the commutation switch 4A is an IGBT (insulated gate bipolar transistor) or a field effect transistor, etc., an operation for interruption is performed near the current zero point of the commutation current It.

[0092] 〔Third Embodiment〕 Next, the third embodiment of the present invention will be described with reference to FIG. 10. In FIG. 10, the same components as those in FIGS. 2 and 5 are denoted by the same reference numerals.

[0093] As shown in FIG. 10, the DC circuit breaker A2 according to the third embodiment includes two commutation switches 4A and bias blocks B in parallel with those in the DC circuit breaker A1 according to the second embodiment. That is, this DC circuit breaker A2 includes a first commutation switch 4A1, a second commutation switch 4A2, a first bias block B1, and a second bias block B2 instead of the commutation switch 4A and the bias block B in the DC circuit breaker A1.

[0094] That is, the DC circuit in this DC circuit breaker A2 includes two (a plurality of) second DC circuits D1 and D2 connected in parallel to each other. One of the second DC circuits D1 includes a first commutation switch 4A1 and a first bias block B1 (commutation promotion circuit). The other second DC circuit D2 includes a second commutation switch 4A2 and a second bias block B2 (commutation promotion circuit).

[0095] In addition, this DC circuit breaker A2 is provided with a control device 10A instead of the control device 10 in the DC circuit breaker A1. This control device 10A is provided with a fourth output terminal in addition to the above-described first to third output terminals. The control device 10A controls the first current-commutating switch 4A1 by outputting a first opening / closing control signal from the second output terminal to the control terminal of the first current-commutating switch 4A1. Further, the control device 10A controls the second current-commutating switch 4A2 by outputting a second opening / closing control signal from the fourth output terminal to the control terminal of the second current-commutating switch 4A2.

[0096] The first current-commutating switch 4A1 and the first bias block B1 are connected in series, and are also connected in series to the capacitor current-limiting block C. Further, the second current-commutating switch 4A2 and the second bias block B2 are connected in series, and are also connected in series to the capacitor current-limiting block C.

[0097] That is, a first series circuit composed of the first current-commutating switch 4A1 and the first bias block B1 and a second series circuit composed of the second current-commutating switch 4A2 and the second bias block B2 are connected in parallel with each other and are connected in series to the capacitor current-limiting block C.

[0098] The first bias block B1 and the second bias block B2 are configured identically. That is, the first bias block B1 is a parallel connection circuit of an auxiliary capacitor 13, an auxiliary diode 14, and a voltage source 15. The second bias block B2 is a parallel connection circuit of a second auxiliary capacitor 16, a second auxiliary diode 17, and a second voltage source 18.

[0099] The first current-commutating switch 4A1 is a mechanical opening / closing switch similar to the current-commutating switch 4A in the second embodiment. One contact is connected to the other end of the capacitor current-limiting block C, the other contact is connected to one end of the first bias block B1, and the control terminal is connected to the second output terminal in the control device 10A. The first current-commutating switch 4A1 closes or opens based on the first opening / closing control signal input to the control terminal from the control device 10A.

[0100] The second commutation switch 4A2 is a mechanical on-off switch similar to the commutation switch 4A of the second embodiment. One contact is connected to the other end of the capacitor current-limiting block C, the other contact is connected to one end of the second bias block B2, and the control end is connected to the fourth output end in the control device 10A. The second commutation switch 4A2 closes or opens based on the second on-off control signal input to the control end from the control device 10A.

[0101] One end of the first bias block B1 is connected to the other contact of the first commutation switch 4A1, and the other end is connected to the other contact of the main switch 1, the output terminal OUT, and the other end of the second bias block B2. One end of the second bias block B2 is connected to the other contact of the second commutation switch 4A2, and the other end is connected to the other contact of the main switch 1, the output terminal OUT, and the other end of the first bias block B1.

[0102] The second auxiliary capacitor 16 is the same circuit element as the auxiliary capacitor 13. One end of this second auxiliary capacitor 16 is connected to the other contact of the second commutation switch 4A2, and the other end is connected to the other contact of the main switch 1, the output terminal OUT, and the other end of the first bias block B1.

[0103] The second auxiliary diode 17 is the same circuit element as the auxiliary diode 14. One end of this second auxiliary diode 17 is connected to the other contact of the second commutation switch 4A2, and the other end is connected to the other contact of the main switch 1, the output terminal OUT, and the other end of the first bias block B1.

[0104] Also, the second voltage source 18 is the same circuit element as the voltage source 15. One end of this second voltage source 18 is connected to the other contact of the second commutation switch 4A2, and the other end is connected to the other contact of the main switch 1, the output terminal OUT, and the other end of the first bias block B1.

[0105] In such a DC circuit breaker A2, the first current-commutating switch 4A1 and the second current-commutating switch 4A2 are individually controlled by the control device 10A. That is, the control device 10A closes the first current-commutating switch 4A1 at a predetermined timing by outputting a first opening / closing control signal to the control terminal of the first current-commutating switch 4A1, and closes the second current-commutating switch 4A2 at a timing different from that of the first current-commutating switch 4A1 by outputting a second opening / closing control signal to the control terminal of the second current-commutating switch 4A2.

[0106] According to such a DC circuit breaker A2, for example, when interrupting a forward current, the first current-commutating switch 4A1 is closed, and when interrupting a reverse current, the second current-commutating switch 4A2 is closed, whereby the current can be interrupted.

[0107] 〔Fourth Embodiment〕 Subsequently, a fourth embodiment of the present invention will be described with reference to FIG. 11. In FIG. 11, the same components as those in FIGS. 2, 5, and 10 are denoted by the same reference numerals.

[0108] As shown in FIG. 11, a DC circuit breaker A3 according to the fourth embodiment includes a first automatic bias block B1a and a second automatic bias block B2a instead of the first bias block B1 and the second bias block B2 in the DC circuit breaker A2 according to the third embodiment.

[0109] The first automatic bias block B1a includes a first diode 19, a first capacitor 20, and a first resistor 21 instead of the voltage source 15 in the third embodiment. The second automatic bias block B2a includes a second diode 22, a second capacitor 23, and a second resistor 23 instead of the second voltage source 18 in the third embodiment.

[0110] The anode terminal of the first diode 19 is connected to the other contact in the first current-commutating switch 4A1, one end of the auxiliary capacitor 13, and the anode terminal of the auxiliary diode 14, and the cathode terminal is connected to one end of the first capacitor 20.

[0111] The first capacitor 20 has a predetermined capacitance. One end thereof is connected to the cathode terminal of the first diode 19, and the other end is connected to one end of the first resistor 21. The first resistor 21 has a predetermined resistance value. One end thereof is connected to the other end of the first capacitor 20, and the other end is grounded.

[0112] The anode terminal of the second diode 22 is connected to the other contact in the second commutation switch 4A2, one end of the second auxiliary capacitor 16, and the anode terminal of the second auxiliary diode 17. The cathode terminal is connected to one end of the second capacitor 23.

[0113] One end of the second capacitor 23 is connected to the cathode terminal of the second diode 22, and the other end is connected to one end of the second resistor 23. The second resistor 23 has a predetermined resistance value. One end thereof is connected to the other end of the second capacitor 23, and the other end is grounded.

[0114] That is, in this DC circuit breaker A3, one second DC circuit is constituted by the first commutation switch 4A1 and the first automatic bias block B1a (commutation promotion circuit). Also, in this DC circuit breaker A3, the other second DC circuit is constituted by the second commutation switch 4A2 and the second automatic bias block B2a (commutation promotion circuit).

[0115] The first automatic bias block B1a and the second automatic bias block B2a in the DC circuit breaker A3 automatically charge the auxiliary capacitor 13 and the second auxiliary capacitor 16 in reverse polarity by using the DC power to be interrupted in the steady state where the main switch 1 is set to the closed state and the first commutation switch 4A1 and the second commutation switch 4A2 are set to the open state.

[0116] That is, in the steady state, DC power is supplied from other contacts in the main switch 1 to the other end of the auxiliary capacitor 13. In the auxiliary capacitor 13, a charging current flows through the path of the auxiliary capacitor 13 → the first diode 19 → the first capacitor 20 → the first resistor 21 by this DC power. This charging current charges the auxiliary capacitor 13 so that it has the opposite polarity to the DC power supplied from the high-voltage DC power supply V to the input terminal IN, similar to the voltage source 15 in the third embodiment.

[0117] Also, in the steady state, DC power is supplied from other contacts in the main switch 1 to the other end of the second auxiliary capacitor 16 in the same manner as the auxiliary capacitor 13. In the second auxiliary capacitor 16, a charging current flows through the path of the second auxiliary capacitor 16 → the second diode 22 → the second capacitor 23 → the second resistor 24 by this DC power.

[0118] This charging current charges the auxiliary capacitor 13 so that it has the opposite polarity to the DC power supplied from the high-voltage DC power supply V to the input terminal IN, similar to the second voltage source 18 in the third embodiment. That is, the DC circuit breaker A3 according to the fourth embodiment automatically charges the auxiliary capacitor 13 and the second auxiliary capacitor 16 with the opposite polarity to the DC power using the DC power of the high-voltage DC power supply V to be interrupted.

[0119] According to such a fourth embodiment, since the auxiliary capacitor 13 and the second auxiliary capacitor 16 are automatically charged with the opposite polarity by the DC power of the high-voltage DC power supply V, the relatively expensive voltage source 15 and the second voltage source 18 can be reduced. Therefore, according to the fourth embodiment, it is possible to provide a DC circuit breaker A3 with a reduced device cost compared to the DC circuit breaker A2 according to the third embodiment.

[0120] 〔Fifth Embodiment〕 Finally, the fifth embodiment of the present invention will be described with reference to FIG. 12. In FIG. 12, the same components as those in FIGS. 2, 5, 10, and 11 are denoted by the same reference numerals.

[0121] As shown in Fig. 11, the DC circuit breaker A4 according to the fifth embodiment is obtained by replacing the capacitor current-limiting block C of the DC circuit breaker A3 according to the fourth embodiment with a plurality (n) of capacitor current-limiting blocks C1 to Cn. That is, the series circuit in the DC circuit breaker A4 includes a plurality (n) of capacitor current-limiting blocks C1 to Cn connected in series with each other.

[0122] In such a DC circuit breaker A4, since the voltage applied to the n capacitor current-limiting blocks C1 to Cn is divided among the n capacitor current-limiting blocks C1 to Cn, it is possible to increase the voltage of the DC power that can be interrupted by the DC circuit breaker A4. Therefore, according to the fifth embodiment, it is possible to interrupt DC power at a higher voltage than the DC circuit breaker A3 according to the fourth embodiment.

[0123] Note that the present invention is not limited to the above embodiments, and for example, the following modifications are conceivable. (1) The DC circuit breaker A (capacitor commutation current-limiting type DC circuit breaker) according to the first embodiment includes the main switch 1, the interruption part current-limiting device 2, the commutation current-limiting capacitor 3, the transistor 4, the bias resistor 5, the diode 6, the discharge resistor 7, the discharge switch 8, the varistor 9, and the control device 10, but the present invention is not limited thereto.

[0124] The interruption part current-limiting device 2, the diode 6, the discharge resistor 7, the discharge switch 8, the varistor 9, and the control device 10 are not essential components and may be deleted as necessary. That is, a DC circuit breaker may be configured using the main switch 1 and a series circuit 11 connected in parallel to the main switch 1 and including the commutation current-limiting capacitor 3 and the commutation switch (the transistor 4 and the bias resistor 5).

[0125] (2) In the first embodiment, the commutation switch of the present invention is configured as a semiconductor switch circuit including a transistor 4 and a bias resistor 5, but the present invention is not limited thereto. For example, the commutation switch of the present invention may be configured by a mechanical on-off switch. Further, when a semiconductor switch circuit is adopted as the commutation switch, a power semiconductor element in a form other than an NPN bipolar transistor, such as a thyristor or a field effect transistor, may be used.

[0126] For example, when a semiconductor switch circuit is configured by a thyristor and a bias resistor 5, the anode terminal of the thyristor is connected to the other end of the commutation current limiting capacitor 3, the other end of the bias resistor 5, one contact in the discharge switch 8, and the other end of the varistor 9, and the cathode terminal is connected to the other contact in the main switch 1 and the output terminal OUT. Further, the gate terminal of the thyristor is connected to the second output terminal of the control device 10.

[0127] That is, the thyristor is connected in series with the commutation current limiting capacitor 3. Further, this thyristor constitutes a series circuit 11 together with the commutation current limiting capacitor 3 and the bias resistor 5. Such a thyristor is set to an ON state (conducting state) / OFF state (non-conducting state) based on an on-off control signal input to the gate terminal from the control device 10.

[0128] (3) In the first embodiment, a single commutation current limiting capacitor 3 is adopted as the power storage circuit of the present invention, but the present invention is not limited thereto. For example, a capacitor block in which a plurality of capacitors are connected in series and / or in parallel may be adopted as the power storage circuit.

[0129] (4) In the first embodiment, a single diode 6 is adopted as the unidirectional coupling circuit of the present invention, but the present invention is not limited thereto. For example, a diode block in which a plurality of diodes are connected in series and / or in parallel may be adopted as the unidirectional coupling circuit.

[0130] (5) In the first embodiment, the control device 10 is used as a component, but the present invention is not limited to this. The control device 10 may be separated from the DC breaker A and used as a separate device. Also, in the above embodiment, the fault detection device is an external device of the DC breaker A, but the present invention is not limited to this. The function of the fault detection device may be incorporated into the DC breaker A.

[0131] (6) In the first embodiment, the basis for current interruption is a fault occurrence, but the present invention is not limited to this. Power supply to and interruption of the load may be performed according to an artificial intention. Also, the control device 10 may have a function of being able to perform opening and closing operations intentionally.

[0132] (7) In the first embodiment, the power supply voltage that can be interrupted by a single DC breaker A is limited. To solve such a problem, it is conceivable to connect a plurality of DC breakers A in series.

[0133] (8) In the third to fifth embodiments, the number (parallel number) of the second series circuits is two, but the present invention is not limited to this. That is, the number (parallel number) of the second series circuits may be three or more.

[0134] (9) As a modification of the fifth embodiment, an auxiliary reactor may be provided between n capacitor current-limiting blocks C1 to Cn and the discharge circuit 12 and the main switch 1. That is, this auxiliary reactor has a predetermined inductance, one end is connected to one contact of the main switch 1, and the other end is connected to one end of the capacitor current-limiting block C1 located at the uppermost stage and one end of the discharge resistor 7.

Description of Reference Numerals

[0135] A Capacitor Commutating Current-Limiting DC Breaker (DC Breaker) B Bias Block (Commutation Promotion Circuit) C Capacitor Current-Limiting Block IN Input Terminal OUT Output Terminal CNT Control Terminal 1 Main Switch 2 Interruption part current limiting device (current limiting circuit) 3 Current transfer capacitor for current limiting (energy storage circuit) 4 Transistor (current transfer switch) 5 Bias resistor (current transfer switch) 6 Diode (unidirectional coupling circuit) 7 Discharge resistor 8 Discharge switch 9 Varistor (overvoltage protection circuit) 10 Control device 11 Series circuit 12 Discharge circuit 13 Auxiliary capacitor (auxiliary energy storage circuit)

Claims

1. A main switch, a series circuit that is connected in parallel with the main switch and includes a power storage circuit and a commutation switch, a DC circuit breaker that commutates the discharge current of the main switch to the power storage circuit by setting the commutation switch to a closed state after opening the main switch.

2. A DC circuit breaker according to claim 1, further comprising a unidirectional coupling circuit having one end connected to the input side of the main switch and the other end connected to one end of the series circuit, allowing the current to flow from the main switch to the series circuit and blocking the current from flowing from the series circuit to the main switch.

3. The DC circuit breaker according to claim 1 or 2, further comprising a discharge circuit for discharging the charge of the power storage circuit.

4. The DC circuit breaker according to claim 1 or 2, further comprising an overvoltage protection circuit for protecting the power storage circuit from overvoltage.

5. The DC circuit breaker according to claim 1 or 2, further comprising a current limiting reactor between the DC circuit breaker and an external DC power source.

6. The DC circuit breaker according to claim 1 or 2, wherein the commutation switch is a semiconductor switch circuit.

7. The DC circuit breaker according to claim 1 or 2, further comprising a current limiting circuit for limiting the energizing current of the main switch.

8. The DC circuit breaker according to claim 1 or 2, further comprising a control device for controlling the main switch and the commutation switch, wherein the control device sets the commutation switch to a closed state after opening the main switch.

9. The DC circuit breaker according to claim 8, wherein the control device opens the main switch when a ground fault detection signal indicating a ground fault at the power supply destination of the DC power is input, and sets the commutation switch to a closed state after a predetermined time has elapsed since the opening.

10. The DC circuit breaker according to claim 1 or 2, wherein the series circuit includes a commutation promotion circuit for promoting the commutation of the discharge current to the power storage circuit.

11. The DC circuit breaker according to claim 10, wherein the commutation promotion circuit promotes the commutation of the discharge current to the power storage circuit by increasing the voltage between the terminals of the power storage circuit.

12. The DC circuit breaker according to claim 11, wherein the commutation promotion circuit increases the voltage between the terminals of the power storage circuit by charging an auxiliary power storage circuit with a polarity opposite to that of the DC power to be interrupted.

13. The DC circuit breaker according to claim 12, wherein the commutation promotion circuit charges the auxiliary power storage circuit with a reverse polarity using the DC power.

14. The series circuit according to claim 10 of the DC circuit breaker includes the power storage circuit, the commutation switch, and the commutation promotion circuit, and a plurality of second series circuits connected in parallel with each other.

15. The series circuit of the DC circuit breaker according to claim 10 includes a plurality of the power storage circuits connected in parallel with each other.

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