JP2018206539A - DC blocking device - Google Patents

Abstract

To provide a low loss, simple configuration hybrid DC blocking device in which there is no stationary loss due to main circuit current at steady state, and it is not required to externally supply power for generating a current cancelling the fault current for blocking a mechanical switch.SOLUTION: Multiple capacitors 3a, 3b are connected in parallel between positive and negative electrodes of a DC line between first and second DC systems 10, 20. Resistors 41a, 41b and semiconductor switches 42a, 42b are connected in series with the multiple capacitors 3a, 3b, respectively. The multiple capacitors 3a, 3b are connected in series by a series path. An intermediate semiconductor switch 5 is provided between respective capacitors 3a, 3b of the series path. An inductor 7 is provided in the series path. A first mechanical circuit breaker 1 is connected between a power inverter circuit 6 and the positive or negative electrode of the first DC system 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a DC circuit breaker, and more particularly, to a DC circuit breaker using an auxiliary circuit to interrupt a current of a mechanical circuit breaker.

  Compared with AC systems, DC transmission / distribution systems can avoid problems caused by AC, such as loss, simplification of the system, ease of connection to DC loads, harmonics, three-phase unbalance, synchronization, reactive power, etc. Has gained attention, such as.

  On the other hand, when an accident such as a short circuit or a ground fault occurs, the DC transmission / distribution system has a problem that it is difficult to interrupt the current compared to the AC system. In the AC system, the AC current is zero every half cycle of the power supply frequency, and the accident current can be interrupted relatively easily by opening the circuit breaker at the zero point of the AC current.

  However, in the DC power transmission and distribution system, the current does not become zero every half cycle of the power supply frequency. Therefore, even if the mechanical circuit breaker is opened, an arc is generated between the contacts and cannot be interrupted, or it takes a long time to interrupt. . There is also a problem that the life of the circuit breaker is shortened by the arc.

  There are mainly three types of DC interrupters used in DC power transmission and distribution systems: mechanical, semiconductor, and hybrid of machine and semiconductor.

  The mechanical type mechanically opens the line such as an air circuit breaker, a vacuum circuit breaker, or a gas circuit breaker. Some have an LC resonance circuit or the like to cut off current (for example, FIGS. 1 and 2 of Non-Patent Document 1). Because it is a mechanical contact, there is a feature that steady loss does not occur during normal conduction.

  The semiconductor type is a circuit breaker configured by using a semiconductor switch, and has an advantage that it can be interrupted at high speed without generating an arc (for example, FIG. 3 of Non-Patent Document 1). On the other hand, there is a problem in that steady loss occurs because the current in the transmission and distribution line always flows through the semiconductor switch.

  The hybrid type is a combination of a mechanical circuit breaker and a semiconductor circuit breaker, and has both features. FIG. 19 shows a configuration of a hybrid circuit breaker disclosed in Patent Document 1.

  By turning on the mechanical circuit breaker 101 and the semiconductor switch 104 composed of the semiconductor switching elements in anti-series, a direct current can flow in a steady state. When an overcurrent due to a short circuit or the like is detected, the semiconductor switch 104 is turned off, and at the same time, the commutation circuit 110 configured by connecting a plurality of semiconductor switches 102 in series is turned on. As a result, the fault current is commutated from the path including the mechanical circuit breaker 101 to the commutation circuit 110. When the commutation is completed, the current flowing through the mechanical circuit breaker 101 becomes zero, so that the mechanical circuit breaker 101 can be opened without generating an arc.

  Thereafter, the commutation circuit 110 is turned off to complete the DC interruption. The non-linear resistance element 103 limits the overvoltage generated at both ends of the circuit by turning off the commutation circuit 110 by the energy held by the inductance of the main circuit.

  FIG. 20 shows a configuration of a hybrid circuit breaker disclosed in Patent Document 2. The hybrid circuit breaker of FIG. 20 includes a mechanical circuit breaker 201, a semiconductor switch 202, a power conversion device 210, and a non-linear resistance 203. The power conversion device 210 is configured by connecting one or a plurality of H bridge circuits 204 including semiconductor switching elements and capacitors in series.

  The hybrid circuit breaker of FIG. 20 can flow a direct current during normal operation by turning on the mechanical circuit breaker 201. When an overcurrent due to a short circuit or the like is detected, the semiconductor switch 202 is turned on, and a current is output by the power converter 210 so that the accident current flowing through the mechanical circuit breaker 201 is zero. The circuit can be opened without generating an arc.

EP2502248B1 JP 2014-235834 A

X. Pei, O. Cwikowski, DS Vilchis-Rodriguez, M. Barnes, AC Smith and R. Shuttleworth, "A review of technologies for MVDC circuit breakers," IECON 2016-42nd Annual Conference of the IEEE Industrial Electronics Society, Florence, 2016, pp. 3799-3805.

  However, the mechanical circuit breaker has a problem that an arc is generated in the interruption, which adversely affects the breaking speed and the life of the breaker. There is also a problem that it takes a very long time to shut off. On the other hand, the semiconductor circuit breaker has a problem that steady loss occurs during normal operation.

  The hybrid circuit breaker has both advantages compared to the mechanical type and semiconductor type, and can realize the low loss and high speed circuit breaker required for a DC circuit breaker.

  However, the technique disclosed in Patent Document 1 has a problem in that a steady loss occurs because the main current always passes through the semiconductor switch 104 when the DC system normally operates. Compared with a semiconductor circuit breaker, the withstand voltage of the semiconductor elements constituting the semiconductor switch 104 may be small. Therefore, Patent Document 1 can use a switching element with a small conduction loss, and the steady loss is small. However, there is a demerit that a steady loss occurs compared to a mechanical circuit breaker.

  On the other hand, in the method shown in Patent Document 2, since a current flows only through the mechanical circuit breaker 201 at normal times, the steady loss can be made substantially zero. However, it is necessary to charge the capacitor of the H bridge circuit 204 constituting the power converter 210, and a mechanism for supplying power from the outside is required. In addition, a large number of semiconductor switches are required, and the circuit configuration is complicated.

  As described above, there is no steady loss due to the main circuit current at the time of steady state, and it is not necessary to supply a power supply for generating a current that cancels the accident current to shut off the mechanical switch, and Therefore, it is an object to provide a hybrid direct current circuit breaker with low loss and simple configuration.

  The present invention has been devised in view of the conventional problems, and one aspect thereof includes a plurality of capacitors connected in parallel between a positive electrode and a negative electrode of a DC line between the first and second DC systems. A resistor and a semiconductor switch connected in series to the plurality of capacitors, a series path connecting the plurality of capacitors in series, an intermediate semiconductor switch provided between the capacitors of the series path, A power conversion circuit having an inductor provided in a series path; and a first mechanical circuit breaker connected between the power conversion circuit and a positive electrode or a negative electrode of the first DC system. And

  As one aspect thereof, one end is connected to the negative electrode of the DC line between the first and second DC systems, a first arm switch unit in which a first resistor and a first semiconductor switch are connected in series, and one end is the first. A first capacitor arm having a first capacitor connected to the other end of the arm switch unit and having the other end connected to the positive electrode of the DC line; one end connected to the positive electrode of the DC line; A second arm switch unit in which second semiconductor switches are connected in series; and a second capacitor having one end connected to the other end of the second arm switch unit and the other end connected to the negative electrode of the DC line. A second capacitor arm, a common connection point of the first capacitor and the first arm switch unit, a common connection point of the second capacitor and the second arm switch unit, and the first capacitor And a power converter circuit comprising: a series path connecting the second capacitor in series; an intermediate semiconductor switch connected in series between the capacitors of the series path; and an inductor provided in the series path; And a first mechanical circuit breaker connected between the conversion circuit and the positive or negative electrode of the first DC system.

  Moreover, as another aspect, one end is connected to the negative electrode of the DC line between the first and second DC systems, a first arm switch unit in which a first resistor and a first semiconductor switch are connected in series, and one end is the first A first capacitor arm having a first capacitor connected to the other end of the one-arm switch unit and having the other end connected to the positive electrode of the DC line; and one end connected to the positive electrode of the DC line; A positive electrode arm switch unit having one end connected to the negative electrode of the DC line, a negative electrode arm switch unit having a negative electrode semiconductor switch, and the other end of the positive electrode arm switch unit and the other end of the negative electrode arm switch unit One or a plurality of second to n-1 capacitor arms (n = an integer greater than or equal to 3) having a second to n-1 capacitor connected to the positive electrode of the DC line An n-th arm switch unit having an end connected and an n-th resistor and an n-th semiconductor switch connected in series, one end connected to the other end of the n-th arm switch unit, and the other end connected to the negative electrode of the DC line An nth capacitor arm, a series path connecting the first to nth capacitors in series, an intermediate semiconductor switch provided between the capacitors of the series path, and the series path A power conversion circuit including the provided inductor; and a first mechanical circuit breaker connected between the power conversion circuit and a positive electrode or a negative electrode of the first DC system. .

  Moreover, as another aspect, one end is connected to the negative electrode of the DC line between the first and second DC systems, a first arm switch unit in which a first resistor and a first semiconductor switch are connected in series, and one end is the first A first capacitor arm having a first capacitor connected to the other end of the one-arm switch unit and having the other end connected to the positive electrode of the DC line; one end connected to the positive electrode of the DC line; A second arm switch unit in which a first semiconductor switch and a second semiconductor switch are connected in series; a second capacitor having one end connected to the other end of the second arm switch unit and the other end connected to the negative electrode of the DC line; A resistor and an intermediate capacitor are connected in series between a second capacitor arm having a common connection point of the first resistor and the first semiconductor switch, and a common connection point of the second resistor and the second semiconductor switch. A capacitor arm; a series path connecting the first capacitor, the intermediate capacitor, and the second capacitor in series; and between the first capacitor and the intermediate capacitor in the series path; and the intermediate capacitor and the second capacitor. Connected between the power conversion circuit and the positive or negative electrode of the first DC system, the power conversion circuit including an intermediate semiconductor switch provided between the power supply circuit and the inductor provided in the series path. And a first mechanical circuit breaker.

  Further, as one aspect thereof, a plurality of the intermediate capacitor arms are provided, and an intermediate semiconductor switch is connected between the intermediate capacitors of the plurality of intermediate capacitor arms.

  Moreover, as one aspect thereof, a DC capacitor is provided between the positive and negative electrodes on the first DC system side of the first mechanical circuit breaker.

  As one aspect thereof, when a current flows from the first DC system to the second DC system, and an accident occurs in the second DC system, the semiconductor switch is turned off, and the intermediate semiconductor switch is turned off. It is turned on, and after the current flowing through the first mechanical circuit breaker becomes a predetermined value or less, the first mechanical circuit breaker is opened.

  Moreover, as one aspect thereof, a second mechanical circuit breaker connected between the power conversion circuit and a positive electrode or a negative electrode of the second DC system is provided.

  Moreover, as one aspect thereof, a DC capacitor is provided between the positive and negative electrodes on the second DC system side of the second mechanical circuit breaker.

  According to the present invention, there is almost no steady loss due to the main circuit current at the time of steady state, and it is not necessary to supply a power supply for generating a current that cancels the accident current in order to shut off the mechanical switch, and It is possible to provide a hybrid direct current circuit breaker with low loss and simple configuration.

FIG. 2 is a circuit diagram showing a DC interrupter in Embodiment 1. 3 is a time chart showing a sequence at the time of interruption in the first embodiment. The figure which shows the direct current | flow interruption | blocking apparatus at the time of interruption | blocking in Embodiment 1. FIG. 3 is a time chart showing a sequence at the time of return in the first embodiment. FIG. 5 is a circuit diagram showing a DC interrupter in Embodiment 2. FIG. 5 is a circuit diagram showing a DC interrupter in Embodiment 3. The figure which shows the DC interruption | blocking apparatus at the time of interruption | blocking in Embodiment 3. FIG. 10 is a time chart showing a sequence at the time of shutoff in the third embodiment. FIG. 6 is a circuit diagram showing a DC interrupter in Embodiment 4. FIG. 9 is a circuit diagram showing a DC interrupter in Embodiment 5. The figure which shows the DC interruption | blocking apparatus at the time of interruption | blocking in Embodiment 5. FIG. 10 is a time chart showing a sequence at the time of interruption in the fifth embodiment. 10 is a time chart showing a sequence upon return in the fifth embodiment. FIG. 9 is a circuit diagram showing a DC interrupter in Embodiment 6. FIG. 10 is a circuit diagram showing a DC interrupter in Embodiment 7. 10 is a time chart showing a sequence at the time of interruption in the seventh embodiment. 10 is a time chart showing a sequence upon return in the seventh embodiment. FIG. 10 is a circuit diagram showing a DC interrupt device in an eighth embodiment. The figure which shows an example of the conventional DC interruption | blocking apparatus. The figure which shows the other example of the conventional DC interruption | blocking apparatus.

  Hereinafter, Embodiments 1 to 8 of the direct current circuit breaker according to the present invention will be described in detail with reference to FIGS.

[Embodiment 1]
The configuration of the DC interrupter according to Embodiment 1 is shown in FIG. The first mechanical circuit breaker 1 and the power conversion circuit 6 are inserted into a DC line between the first and second DC systems 10 and 20. The power conversion circuit 6 includes a first capacitor arm 2 a and a second capacitor arm 2 b, an intermediate semiconductor switch 5, and an inductor 7.

  The first capacitor arm 2a is configured by connecting a first capacitor 3a and a first arm switch unit 4a in series between a positive electrode and a negative electrode of a DC line. The first arm switch unit 4a is configured by connecting a first resistor 41a and a first semiconductor switch 42a in series. The first arm switch unit 4a has a function of controlling current in one direction and conducting current in the opposite direction. The connection order of the first resistor 41a and the first semiconductor switch 42a of the first arm switch unit 4a may be any order.

  The second capacitor arm 2b is configured by connecting the second arm switch unit 4b and the second capacitor 3b in series between the positive electrode and the negative electrode of the DC line. In the first capacitor arm 2a and the second capacitor arm 2b, the connection order of the first and second capacitors 3a and 3b and the first and second arm switch units 4a and 4b is relative to the polarity of the two-line DC line. Connected in reverse.

  For example, the first capacitor arm 2a is connected to the first capacitor 3a on the positive side of the DC line, the first arm switch unit 4a is connected to the negative side, and the second capacitor arm 2b is connected to the second arm switch unit 4b on the positive side of the DC line. The second capacitor 3b is connected to the negative electrode side. However, the current direction in which the first and second arm switch units 4a and 4b can control the conduction is the direction from the positive electrode side to the negative electrode side of the DC line.

  Between the first and second capacitors 3a and 3b of the first and second capacitor arms 2a and 2b and the common connection point M of the first and second arm switch sections 4a and 4b, the first capacitor 3a, A series path connecting the second capacitors 3b in series is formed. In this series path, an intermediate semiconductor switch 5 and an inductor 7 are provided. Here, the intermediate semiconductor switch 5 is connected to a polarity (the reverse direction is conductive) in which the current from the second capacitor arm 2b to the first capacitor arm 2a can be controlled.

  The first and second semiconductor switches 42a, 42b and the intermediate semiconductor switch 5 are configured by connecting a switching element that is conductive in one direction and capable of controlling on / off thereof, and a diode in antiparallel to the switching element. Any type of semiconductor switching element may be used as long as it is configured to control the conduction of current in one direction and to conduct current in the opposite direction.

  As the first and second semiconductor switches 42a and 42b and the intermediate semiconductor switch 5, semiconductor switches having a withstand voltage capable of withstanding the maximum voltage between DC lines that can occur in a steady state and a transient state such as a cutoff state are applied. To do. Moreover, the structure may comprise a plurality of semiconductor switching elements in series and in parallel. When a plurality of units are connected in series, an auxiliary circuit that adjusts the voltage balance (for example, a resistor having the same value in parallel with each semiconductor switch) may be provided.

  The first mechanical circuit breaker 1 is connected to the DC line positive side in FIG. The first mechanical circuit breaker 1 has a withstand voltage capable of withstanding the maximum DC voltage generated between the DC lines in an off state, a steady state, a transient state at the time of interruption, an accident, or the like.

  The first and second resistors 41a and 41b, the first and second capacitors 3a and 3b, and the first mechanical circuit breaker 1 may also be composed of a plurality of elements. The capacities of the first and second capacitors 3a and 3b are desirably large enough to cancel the accident current flowing through the first mechanical circuit breaker 1. The first and second resistors 41a and 41b are for charging the first and second capacitors 3a and 3b, and are desirably set to relatively large values.

  Hereinafter, the operation of the DC interrupter in Embodiment 1 will be described. In the first embodiment, a DC voltage source is basically provided on the first DC system 10 side where the first mechanical circuit breaker 1 is located, a load is connected between terminals on the second DC system 20 side, and a short circuit occurs. It is assumed that a ground fault accident occurs on the second DC system 20 side.

  At the time of steady operation in which there is no accident on the DC line, the first mechanical circuit breaker 1 is turned on, and the first and second semiconductor switches 42a and 42b are turned on. Further, the intermediate semiconductor switch 5 is kept off.

  At this time, the direct current flows from the first DC system 10 side to the second DC system 20 side through the first mechanical circuit breaker 1 and the positive and negative DC lines. A current flows through the first and second capacitor arms 2a and 2b via the first and second arm switch portions 4a and 4b and the first and second capacitors 3a and 3b, and the first and second capacitors 3a and 3b. Are charged to be equal to the first system voltage VDC1 (= second system voltage VDC2).

  The operation when a ground fault or short circuit occurs in the DC line will be described with reference to FIGS. A fault current is generated due to a short circuit is detected by a DC current detector (not shown). For example, a current flowing through the first mechanical circuit breaker 1 (hereinafter referred to as a mechanical circuit breaker passing current) i1 is detected, and when it exceeds a threshold value, an accident is determined (time T1 in FIG. 2).

  Accordingly, the first and second semiconductor switches 42a and 42b of the first and second capacitor arms 2a and 2b are turned off (time T1). After the cutoff of the first and second semiconductor switches 42a and 42b is completed, the intermediate semiconductor switch 5 is turned on (time T2).

  As a result, the first and second capacitors 3a and 3b of the first and second capacitor arms 2a and 2b are connected in series between the positive and negative electrodes of the DC line by the intermediate semiconductor switch 5, and the power conversion circuit 6 is maximum. A voltage of 2≡VDC1 is generated between the DC terminals.

  As a result, a resonance current ic in the direction opposite to the fault current is flows through the first mechanical circuit breaker 1, and the mechanical circuit breaker passage current i1 (= is-ic) starts to decrease. The mechanical circuit breaker 1 is opened (time T3), and the current continues to flow between the terminals opened by the arc discharge even after the physical circuit opening operation of the first mechanical circuit breaker 1 is completed (time T4). However, when the resonance current ic increases and becomes equal to the accident current is, the mechanical circuit breaker passing current i1 becomes zero, so that the arc discharge is cut off and the opening of the first mechanical circuit breaker 1 is completed (time T5).

  The timing at which the opening operation of the first mechanical circuit breaker 1 is started may be the timing at which the mechanical circuit breaker passage current i1 is physically opened before reaching zero and the circuit breaker can be sufficiently maintained. Accordingly, in FIG. 2, the opening operation of the first mechanical circuit breaker 1 is started after the time T2 when the intermediate semiconductor switch 5 is turned on, but the circuit breaker is sufficiently cut off before the mechanical circuit breaker passing current i1 reaches zero. Can be maintained before the time T2.

  FIG. 4 shows a sequence for returning after completion of the opening of the circuit when a fault such as a ground fault or a short circuit in the DC line is removed. At time T1, the intermediate semiconductor switch 5 is first turned off, and then at time T2, the first and second semiconductor switches 42a and 42b are turned on. Thereafter, the first mechanical circuit breaker 1 is turned on (time T3 → time T4). As a result, the first and second capacitors 3a and 3b are charged to the first system voltage VDC1, and preparation for performing the next cutoff operation is completed.

As described above, according to the DC interrupting device of the first embodiment, it is possible to eliminate the loss due to the steady-state current in the DC interrupting device. (When resistance loss of the first mechanical circuit breaker 1 is assumed to be zero)
Further, it is not necessary to supply a power source with a current that cancels the accident current is from the outside. Furthermore, it is possible to provide a hybrid type DC circuit breaker having a low loss and a simple configuration.

  Further, when an accident such as a ground fault or a short circuit occurs, the arc of the first mechanical circuit breaker 1 can be quickly extinguished and the first mechanical circuit breaker 1 can be opened by the resonance current ic from the power conversion circuit 6. Become.

[Embodiment 2]
FIG. 5 shows the configuration of the DC interrupter according to the second embodiment. The second embodiment is different from the first embodiment in the configuration of the first embodiment and the power conversion circuit 6.

  The power conversion circuit 6 includes three or more capacitor arms, two or more intermediate semiconductor switches 5, and an inductor 7. Hereinafter, a case where the number of arms is n (n = an integer of 3 or more) will be described.

  The first capacitor arm 2-1 and the nth capacitor arm 2-n arranged at both ends of the power conversion circuit 6 are the same as the first capacitor arm 2a and the second capacitor arm 2b of the first embodiment.

  The second capacitor arm 2-2 to the (n-1) th capacitor arm 2- (n-1) include a positive arm switch unit 4c connected to the positive electrode of the DC line and a negative arm switch unit connected to the negative electrode of the DC line. 4d and the second to n-1th capacitors 3c connected between the positive arm switch unit 4c and the negative arm switch unit 4d.

  The positive arm switch unit 4c includes a resistor 41c and a positive semiconductor switch 42c connected in series. The negative arm switch part 4d includes a resistor 41d and a negative semiconductor switch 42d connected in series.

  The common connection point M between the first capacitor 3a and the first arm switch unit 4a of the first capacitor arm 2-1 and the common of the positive arm switch unit 4c and the second capacitor 3c of the adjacent second capacitor arm 2-2. The connection point M1 is connected by a serial path. An intermediate semiconductor switch 5 and an inductor 7 are provided in the series path.

  The common connection point M2 of the second capacitor 3c and the negative arm switch part 4d of the second capacitor arm 2-2, and the common connection point of the positive arm switch part 4c and the third capacitor 3c of the adjacent third capacitor arm 2-3. M1 is connected by a series path. An intermediate semiconductor switch 5 and an inductor 7 are provided in the series path.

  Similarly, the second capacitor arm 2-2 and the (n-1) th capacitor arm 2- (n-1) are connected by a series path, and the intermediate semiconductor switch 5 and the inductor 7 are provided in the series path. Between the n-1th capacitor arm 2- (n-1) and the nth capacitor arm 2-n, the common connection point M2 of the n-1th capacitor arm 2- (n-1) and the nth capacitor arm 2 -N common connection points M are connected by a series path, and an intermediate semiconductor switch 5 and an inductor 7 are provided in the series path.

  The resistors 41c and 41d of the positive and negative arm switch units 4c and 4d in the second capacitor arm 2-2 to the (n-1) th capacitor arm 2- (n-1) may be provided in the respective arm switch units 4c and 4d. It may be good or may be integrated into one (one arm switch part 4c or 4d). The resistance values of the individual resistors 41c and 41d need not be the same. However, the resistance values of the resistors 41c and 41d for each capacitor arm 2 (the sum of the resistance value of the resistor 41c and the resistance value of the resistor 41d) are desirably the same. Similarly, the inductors 7 connected in series to the intermediate semiconductor switch 5 may be arranged for each intermediate semiconductor switch 5, or may be integrated into one or several.

  The operation and action of the second embodiment will be described. The basic operation / action is the same as in the first embodiment. When a short circuit occurs, the first and second semiconductor switches 42a and 42b, the positive semiconductor switch 42c, and the negative semiconductor switch 42d of all the first to n-th capacitor arms 2-1 to 2-n are turned off, and all the intermediate switches The semiconductor switch 5 is turned on.

  As a result, all the first to n-th capacitors 3a to 3c are connected in series, and a voltage n times as large as the first system voltage VDC1 is generated at both ends of the power conversion circuit 6. The short circuit current of the accident current is flowing through the first mechanical circuit breaker 1 is canceled by the current generated by the voltage source (resonant current by the capacitors 3a to 3c and the inductor 7), and the mechanical circuit breaker passing current i1 is set to zero. By doing so, the arc is cut off. The subsequent operation is the same as in the first embodiment.

  As described above, according to the second embodiment, the same operational effects as those of the first embodiment can be obtained. Further, compared with the first embodiment, the output voltage of the power conversion circuit 6 can be increased, and the resonance current ic can be quickly increased. As a result, the mechanical circuit breaker passage current i1 (= is-ic) can be quickly reduced, so that the arc of the first mechanical circuit breaker 1 is extinguished earlier and the first mechanical circuit breaker 1 is opened. it can.

[Embodiment 3]
FIG. 6 shows the configuration of the DC interrupter according to the third embodiment. In the third embodiment, the first mechanical circuit breaker 1a and the second mechanical circuit breaker 1b are arranged at both ends of the power conversion circuit 6. In FIG. 6, the first and second mechanical circuit breakers 1a and 1b are provided at both ends of the power conversion circuit 6 of the first embodiment, but the first and second machines are provided at both ends of the power conversion circuit 6 of the second embodiment. The type circuit breakers 1a and 1b may be provided.

  Hereinafter, the operation and action of the third embodiment will be described with reference to FIGS. In the third embodiment, the DC voltage source may be provided on either or both of the first DC system 10 side and the second DC system 20 side, and the direction of the accident current is not limited.

  In the initial state, the first mechanical circuit breaker 1a and the second mechanical circuit breaker 1b are in an open circuit state. In addition, it is assumed that both the first and second capacitors 3a and 3b are discharged. At this time, both the first and second semiconductor switches 42a and 42b are turned on. Further, the intermediate semiconductor switch 5 is turned off.

  Next, the first mechanical circuit breaker 1a is closed. As a result, the first and second capacitors 3a and 3b are both charged to the first system voltage VDC1 via the first and second arm switch sections 4a and 4b. When charging is completed, the second mechanical circuit breaker 1b is closed. By the above procedure, the first and second capacitors 3a and 3b can be charged before the first DC system 10 and the second DC system 20 are made conductive. The order of loading the first mechanical circuit breaker 1a and the second mechanical circuit breaker 1b may be reversed.

  Next, the operation when a short circuit occurs on the second DC system 20 side will be described with reference to FIGS. Here, the current passing through the first mechanical circuit breaker 1a is expressed as a first mechanical circuit breaker passing current i1a. The operation in this case is the same as the operation in the first embodiment until the detection of the occurrence of a short circuit. However, it is necessary to detect the direction of the short-circuit current. When the short-circuit current flows from the first DC system 10 side to the second DC system 20 side on the positive side of the DC line, the following operation is performed.

  Both the first and second semiconductor switches 42a and 42b are turned off (time T1), and then the intermediate semiconductor switch 5 is turned on (time T2). The first mechanical circuit breaker 1a is turned off (time T3 to T4). The voltage at both ends of the DC line of the power conversion circuit 6 becomes higher than the first system voltage VDC1, and the resonance current ic that cancels out the accident current is flows. As a result, the first mechanical circuit breaker passage current i1a is reduced, and the first mechanical circuit breaker 1a is cut off by an arc.

  Thereafter, the second mechanical circuit breaker 1b is turned off (time T6 to T7). The first and second mechanical circuit breakers 1a and 1b may be turned off and the first and second semiconductor switches 42a and 42b may be turned on after the intermediate semiconductor switch 5 is turned off. In this case, the energy charged in the first and second capacitors 3a and 3b is released by the first and second resistors 41a and 41b.

  An operation when a short circuit occurs on the first DC system 10 side will be described. When the accident current flows from the second DC system 20 side to the first DC system 10 side on the positive electrode side of the DC line, the following operation is performed. Both the first and second semiconductor switches 42a and 42b are turned off, and then the intermediate semiconductor switch 5 is turned on.

  Further, the second mechanical circuit breaker 1b is turned off. The voltage at both ends of the DC line of the power conversion circuit 6 becomes higher than the second system voltage VDC2, and a resonance current ic that cancels out the accident current is flows. As a result, the second mechanical circuit breaker passage current i1b (= is-ic) is reduced, and the second mechanical circuit breaker 1b is cut off when the arc is cut.

  Thereafter, the first mechanical circuit breaker 1a is turned off. The first and second mechanical circuit breakers 1a and 1b may be turned off to confirm the interruption, and the intermediate semiconductor switch 5 may be turned off, and then the first and second semiconductor switches 42a and 42b may be turned on. In this case, the energy charged in the first and second capacitors 3a and 3b is released by the first and second resistors 41a and 41b.

  The return sequence is the same as the example of the return sequence shown in FIG. 4 of the first embodiment. However, like the initial charging sequence, the first mechanical circuit breaker 1a and the second mechanical circuit breaker 1b perform the operation of shifting the timing.

  The operations of the first and second mechanical circuit breakers 1a and 1b, the first and second semiconductor switches 42a and 42b, and the intermediate semiconductor switch 5 described above are the first and second mechanical circuit breakers compared to the second embodiment. The same applies when 1a and 1b are provided at both ends of the power conversion circuit 6.

  As described above, according to the third embodiment, the same operational effects as those of the first and second embodiments can be obtained. Further, the current can be cut off regardless of the direction of the short circuit current.

  In addition, when the first and second mechanical circuit breakers 1a and 1b are turned on from the initial state, even if a short circuit has already occurred, the capacitors of the power conversion circuit 6 must be connected before both DC lines are closed. Charging becomes possible. As a result, when the first and second mechanical circuit breakers 1a and 1b are completely turned on, the breaking operation can be executed immediately, and the protection performance against accidents is improved.

[Embodiment 4]
FIG. 9 shows the configuration of the DC interrupter according to the fourth embodiment. The fourth embodiment differs from the third embodiment between the positive and negative electrodes on the first DC system 10 side of the first mechanical circuit breaker 1a and between the positive and negative electrodes on the second DC system 20 side of the second mechanical circuit breaker 1b. A DC capacitor 8a and a DC capacitor 8b are provided. The fourth embodiment can be similarly applied to the first mechanical circuit breaker 1a of the first and second embodiments.

  The operation and action of the fourth embodiment will be described. Since the basic circuit opening operation is the same as the operation in the third embodiment, the description thereof is omitted.

  The DC capacitor 8a functions during the shut-off operation. For example, a case where a short circuit occurs on the second DC system 20 side and the first mechanical circuit breaker 1a is interrupted will be described. When the first and second semiconductor switches 42a and 42b of the power conversion circuit 6 are turned off and then the intermediate semiconductor switch 5 is turned on, the power conversion circuit 6 generates a voltage across the positive and negative DC lines.

  At that time, the resonance current passes through the first mechanical circuit breaker 1 a from the positive side of the power conversion circuit 6, is divided into the DC capacitor 8 a and the first DC system 10 side, and flows to the negative side of the power conversion circuit 6. The current on the first DC system 10 side is limited by the impedance including the internal impedance and the inductance of the line.

  On the other hand, the DC capacitor 8a has a transiently low impedance as the voltage of the power conversion circuit 6 changes, so that a large current tends to flow instantaneously. As a result, the current to the power supply or load on the first DC system 10 side can be suppressed, and the resonance current to the first mechanical circuit breaker 1a can be quickly increased.

  As a result, the opening speed of the first mechanical circuit breaker 1a can be increased. Further, after the first mechanical circuit breaker 1a is opened, the DC capacitor 8a absorbs the energy that the line impedance of the power supply or load on the first DC system 10 side can suppress the voltage rise. .

  The above operation / action is the same for the DC capacitor 8b and the second mechanical circuit breaker 1b.

  As described above, according to the fourth embodiment, the same operational effects as those of the first to third embodiments are obtained. Further, the first and second mechanical circuit breakers 1a and 1b are increased by increasing the resonance current flowing from the power conversion circuit 6 faster than the short-circuit current flowing through the first and second mechanical circuit breakers 1a and 1b. Can be cut off faster.

[Embodiment 5]
FIG. 10 shows a DC cutoff device according to the fifth embodiment. In the DC interrupter in Embodiment 5, a power conversion circuit 6 is provided on a DC line between the first and second DC systems 10 and 20. A first mechanical circuit breaker 1 is provided between the power conversion circuit 6 and the first DC system 10. The first mechanical circuit breaker 1 may be inserted into either the positive or negative line.

  The power conversion circuit 6 includes a first capacitor arm 2a, a second capacitor arm 2b, an intermediate capacitor 21, a resistor 22, an intermediate semiconductor switch 5, and an inductor 7.

  The first capacitor arm 2a is configured by connecting a first capacitor 3a and a first arm switch unit 4a in series between a positive electrode and a negative electrode of a DC line between the first and second DC systems 10, 20. The first arm switch unit 4a is configured by connecting a first resistor 41a and a first semiconductor switch 42a in series. The first capacitor 3a has one end connected to the first arm switch unit 4a and the other end connected to the positive or negative electrode of the DC line. In FIG. 10, the other end of the first capacitor 3a is connected to the positive electrode of the DC line.

  The second capacitor arm 2b is configured by connecting a second capacitor 3b and a second arm switch unit 4b in series between the positive and negative electrodes of the DC line between the first and second DC systems 10 and 20. The second arm switch unit 4b is configured by connecting a second resistor 41b and a second semiconductor switch 42b in series. One end of the second capacitor 3b is connected to the second arm switch unit 4b, and the other end is connected to the opposite side of the first arm switch unit 4a of the first arm switch unit 4a on either the positive or negative side of the DC line. In FIG. 10, the other end of the second capacitor 3b is connected to the negative electrode of the DC line.

  An intermediate capacitor arm is connected between the common connection point of the first resistor 41a and the first semiconductor switch 42a and the common connection point of the second resistor 41b and the second semiconductor switch 42b. The intermediate capacitor arm is configured by connecting a resistor 22, an intermediate capacitor 21, and a resistor 22 in series.

  The first capacitor 3a and the intermediate capacitor 21, and the intermediate capacitor 21 and the second capacitor 3b are connected to form a series path that connects the first, intermediate, and second capacitors 3a, 21, and 3b in series. In this series path, an intermediate semiconductor switch 5 and an inductor 7 are provided between the first capacitor 3a and the intermediate capacitor 21 and between the intermediate capacitor 21 and the second capacitor 3b.

  The intermediate semiconductor switch 5 has a function of controlling conduction / interruption of current in one direction and conducting current in the opposite direction. The direction of current that can control the conduction / cutoff of the intermediate semiconductor switch 5 is from the negative side to the positive side of the DC line.

  The current polarity that can control energization / conduction of the first and second semiconductor switches 42a and 42b is from the positive side to the negative side of the DC line.

  The first and second resistors 41a and 41b and the resistor 22 are resistors for charging the first, second and intermediate capacitors 3a, 3b and 21. As the first and second semiconductor switches 42a and 42b, semiconductor switches having a withstand voltage capable of withstanding the assumed maximum DC voltage are applied. The first and second semiconductor switches 42a and 42b may be configured by connecting a plurality of semiconductor switching elements in series or in parallel, and the types of switching elements are not limited to specific ones. The inductors 7 do not have to be provided in series with each intermediate semiconductor switch 5 and may be combined into one inductor as necessary.

  The operation and action in the fifth embodiment will be described. In the fifth embodiment, a DC voltage source is basically provided on the first DC system 10 side where the first mechanical circuit breaker 1 is located, a load is connected between terminals on the second DC system 20 side, and a short circuit occurs. It is assumed that a ground fault accident occurs on the second DC system 20 side.

  The first mechanical circuit breaker 1 is turned on at the time of steady operation where there is no accident on the DC line. Further, the first and second semiconductor switches 42a and 42b are turned on, and the intermediate semiconductor switch 5 is turned off.

  At this time, a direct current flows from the first direct current system 10 side through the first mechanical circuit breaker 1 and the positive and negative direct current lines. When the first and second semiconductor switches 42a and 42b are on and the intermediate semiconductor switch 5 is off, all the first and second capacitors 3a and 3b and the intermediate capacitor 21 are connected between the positive and negative electrodes of the DC line. , The second resistors 41a and 41b, and the resistor 22 are connected in parallel. As a result, all the first and second capacitors 3a and 3b and the intermediate capacitor 21 are connected to the first system voltage VDC1 (= second system). The voltage VDC2) is charged.

  The operation when an accident such as a ground fault or a short circuit occurs in the DC line will be described with reference to FIGS. An excessive accident current is generated due to a short circuit is detected by a DC current detector (not shown). For example, a current detector is provided on the line of the first mechanical circuit breaker 1, the mechanical circuit breaker passing current i1 is monitored, and it is determined that a short circuit has occurred when a current exceeding a certain threshold flows.

  Accordingly, the first and second semiconductor switches 42a and 42b are turned off (time T1), and then all the intermediate semiconductor switches 5 are turned on (time T2). Further, the first mechanical circuit breaker 1 is opened (time T3 to T4).

  As a result, all the first and second capacitors 3a and 3b and the intermediate capacitor 21 are connected in series between the positive and negative electrodes of the DC line, and the power conversion circuit 6 is a voltage obtained by adding the voltages of the three capacitors. (When the voltages of all the first and second capacitors 3a and 3b and the intermediate capacitor 21 are the first system voltage VDC1, 3 × VDC1) are generated between the DC lines.

  As a result, during the period in which “the voltage across the power conversion circuit 6 ≠ the first system voltage VDC1 on the first mechanical circuit breaker 1 side”, the resonance current flows from the power conversion circuit 6 to the first mechanical circuit breaker 1. ic is supplied. The resonance current ic resonates by the first and second capacitors 3a and 3b, the intermediate capacitor 21 and the inductor 7.

  When this resonance current ic becomes equal to the accident current is, a moment occurs when the mechanical circuit breaker passage current i1 (= is-ic) becomes zero, and the arc of the first mechanical circuit breaker 1 generated by the opening operation is generated. Is extinguished and the opening is completed.

  After completion of the circuit opening, the intermediate semiconductor switch 5 and the first and second semiconductor switches 42a and 42b may be turned on. By turning on, the energy of the intermediate capacitor 21 and the inductor 7 can be dissipated by the first and second resistors 41a and 41b.

  Next, the return sequence of the fifth embodiment will be described with reference to FIG. At time T1, the intermediate semiconductor switch 5 is first turned off, and then at time T2, the first and second semiconductor switches 42a and 42b are turned on. Thereafter, the first mechanical circuit breaker 1 is turned on (time T3 → time T4). As a result, the first and second capacitors 3a and 3b and the intermediate capacitor 21 are charged to the first system voltage VDC1, and preparation for performing the next cutoff operation is completed.

As described above, according to the fifth embodiment, it is possible to eliminate a loss due to a steady-state current in the DC interrupter. (Assuming the resistance of the mechanical breaker is zero)
Moreover, the arc of the first mechanical circuit breaker 1 can be quickly extinguished and the first mechanical circuit breaker 1 can be opened by the resonance current of the power conversion circuit 6 [Embodiment 6].
FIG. 14 shows a DC circuit breaker according to the sixth embodiment. The sixth embodiment is different from the fifth embodiment in the configuration of the power conversion circuit 6.

  In the sixth embodiment, a plurality of intermediate capacitor arms each having a resistor 22, an intermediate capacitor 21, and a resistor 22 connected in series are connected in parallel between the first arm switch unit 4a and the second arm switch unit 4b. The total number of the first and second capacitors 3a and 3b and the intermediate capacitors 21 included in the power conversion circuit 6 is four or more.

  An intermediate semiconductor switch 5 and an inductor 7 are provided in the series path between the capacitors 21. The inductor 7 may be provided in each intermediate semiconductor switch 5 or may be combined into one inductor.

  The operation and action in the sixth embodiment will be described. The basic operation / action is the same as in the fifth embodiment.

  The first mechanical circuit breaker 1 is turned on at the time of steady operation where there is no accident on the DC line. Further, the first and second semiconductor switches 42a and 42b of the first and second arm switch sections 4a and 4b are turned on, and all the intermediate semiconductor switches 5 are turned off.

  At this time, DC current flows from the first DC system 10 side through the first mechanical circuit breaker 1 and the positive and negative DC lines. When the first and second semiconductor switches 42a and 42b are turned on and the intermediate semiconductor switch 5 is turned off, all the first and second capacitors 3a and 3b and the intermediate capacitor 21 are placed between the positive electrode and the negative electrode of the DC line. The first and second resistors 41a and 41b and the resistor 22 are connected in parallel, and all the first and second capacitors 3a and 3b and the intermediate capacitor 21 are connected to the first system voltage VDC1 (= second system voltage). VDC2) is charged.

  When a ground fault or short circuit occurs in the DC line, the short circuit current is detected by a DC current detector (not shown). For example, a current detector is provided on the line of the first mechanical circuit breaker 1, the mechanical circuit breaker passing current i1 is monitored, and it is determined that a short circuit has occurred when a current exceeding a certain threshold flows.

  With the determination of the short circuit, the first and second semiconductor switches 42a and 42b of the first and second arm switch portions 4a and 4b are turned off. Thereafter, the intermediate semiconductor switch 5 is turned on. Further, the first mechanical circuit breaker 1 is opened.

  As a result, all the first and second capacitors 3a and 3b and the intermediate capacitor 21 are connected in series between the positive and negative electrodes of the DC line, and the power conversion circuit 6 applies the voltage of all capacitors between the DC lines. The added voltage (when the total number of the first and second capacitors 3a and 3b and the intermediate capacitor 21 is n, and all the voltages of the first and second capacitors 3a and 3b and the intermediate capacitor 21 are VDC1, n × VDC1 ) Between the DC lines.

  As a result, during the period in which “the voltage across the power conversion circuit 6 ≠ the first system voltage VDC1 on the first mechanical circuit breaker 1 side”, the resonance current is supplied from the power conversion circuit 6 to the first mechanical circuit breaker 1. ic is supplied. The resonance current ic resonates by the first and second capacitors 3a and 3b, the intermediate capacitor 21 and the inductor 7.

  When the accident current is and the resonance current ic become equal to each other, the current flowing through the first mechanical circuit breaker 1 is zero, and the arc of the first mechanical circuit breaker 1 generated by the opening operation is extinguished. The opening is completed.

  After completion of the circuit opening, the first and second semiconductor switches 42a and 42b and the intermediate semiconductor switch 5 may be turned on. By turning on, the energy of the first and second capacitors 3a and 3b, the intermediate capacitor 21 and the inductor 7 can be dissipated by the first and second resistors 41a and 41b.

As described above, according to the sixth embodiment, the same effects as those of the fifth embodiment are obtained. Further, the output voltage of the power conversion circuit 6 can be increased with respect to the fifth embodiment, and the resonance current can be quickly increased, so that the arc of the first mechanical circuit breaker 1 can be extinguished earlier, First mechanical circuit breaker 1 can be opened [Embodiment 7]
FIG. 15 shows a DC interrupt device of the seventh embodiment. As shown in FIG. 15, in the seventh embodiment, the first mechanical circuit breaker 1 a and the second mechanical circuit breaker 1 b are arranged at both ends of the power conversion circuit 6 of the fifth embodiment. You may arrange | position the 1st mechanical circuit breaker 1a and the 2nd mechanical circuit breaker 1b in the both ends of the power converter circuit 6 of Embodiment 6. FIG.

  The operation and action of the seventh embodiment will be described with reference to FIG. In the seventh embodiment, the DC voltage source may be present on either the first DC system 10 side, the second DC system 20 side, or both, and the direction of the fault current is is not limited.

  In the initial state, the first mechanical circuit breaker 1a and the second mechanical circuit breaker 1b are turned off. Further, it is assumed that the first and second capacitors 3a and 3b and the intermediate capacitor 21 are all discharged. At this time, both the first and second semiconductor switches 42a and 42b of the first and second arm switch sections 4a and 4b are turned on. All the intermediate semiconductor switches 5 are turned off.

  Next, the first mechanical circuit breaker 1a is closed. As a result, all of the three first and second capacitors 3a and 3b and the intermediate capacitor 21 are charged to the first system voltage VDC1. When charging is completed, the second mechanical circuit breaker 1b is closed.

  By the above procedure, the first and second capacitors 3a and 3b and the intermediate capacitor 21 can be charged before the first DC system 10 side and the second DC system 20 side are made conductive. As a result, if a short circuit occurs immediately after the first and second mechanical circuit breakers 1a and 1b are turned on, or if there is no power source in the DC line and the state in which the short circuit is occurring is unknown, It is possible to suppress the occurrence of overcurrent when the power conversion circuit 6 does not function. The order of loading the first and second mechanical circuit breakers 1a and 1b may be reversed.

  Next, the operation when a short circuit occurs on the second DC system 20 side will be described based on FIG. The operation until the detection of the occurrence of a short circuit is the same as the operation in the fifth embodiment. However, it is necessary to detect the polarity of the short-circuit current. When the short-circuit current flows from the first DC system 10 side to the second DC system 20 side on the positive side of the DC line, the following operation is performed.

  The first and second semiconductor switches 42a and 42b of the first and second arm switch sections 4a and 4b are both turned off (time T1), and then all the intermediate semiconductor switches 5 are turned on (time T2). Moreover, the 1st mechanical circuit breaker 1a is turned off (time T3-T4). The voltage across the DC line of the power conversion circuit 6 becomes higher than the first system voltage VDC1, the resonance current ic that cancels the short-circuit current flows, and the first mechanical circuit breaker passing current i1a decreases. At that time, the arc of the first mechanical circuit breaker 1a is extinguished to be interrupted.

  Thereafter, the second mechanical circuit breaker 1b is turned off. After confirming the off state of both the first and second mechanical circuit breakers 1a and 1b, the first and second semiconductor switches 42a and 42b may be turned on. In this case, the energy charged in the capacitor 21 is released by the first and second resistors 41a and 41b.

  An operation when a short circuit occurs on the first DC system 10 side will be described. When the short-circuit current flows from the second DC system 20 side to the first DC system 10 side on the positive side of the DC line, the following operation is performed. The first and second semiconductor switches 42a and 42b of the first and second arm switch sections 4a and 4b are both turned off, and then the intermediate semiconductor switch 5 is turned on. Further, the second mechanical circuit breaker 1b is turned off. The voltage across the DC line of the power conversion circuit 6 becomes higher than the second system voltage VDC2, a resonance current that cancels the short-circuit current flows, and the second mechanical circuit breaker passage current i1b decreases. At that time, the arc of the second mechanical circuit breaker 1b is extinguished to be interrupted.

  Thereafter, the first mechanical circuit breaker 1a is turned off. After confirming the off state of both the first and second mechanical circuit breakers 1a and 1b, the first and second semiconductor switches 42a and 42b may be turned on. In this case, the energy charged in the first and second capacitors 3a and 3b and the intermediate capacitor 21 is released by the first and second resistors 4a and 4b and the resistor 22.

  Next, the return sequence of the seventh embodiment will be described with reference to FIG. At time T1, the intermediate semiconductor switch 5 is first turned off, and then at time T2, the first and second semiconductor switches 42a and 42b are turned on. Thereafter, the first mechanical circuit breaker 1a is turned on (time T3 → time T4). As a result, the first and second capacitors 3a and 3b are charged to the first system voltage VDC1, and preparation for performing the next cutoff operation is completed. Thereafter, the second mechanical circuit breaker 1b is turned on (time T5 to T6).

  The operations of the first and second mechanical circuit breakers 1a and 1b, the first and second semiconductor switches 42a and 42b, and the intermediate semiconductor switch 5 described above are the first and second mechanical circuit breakers 1a with respect to the sixth embodiment. , 1b is the same when both ends of the power conversion circuit 6 are provided.

  As described above, according to the seventh embodiment, the current can be interrupted regardless of the direction of the short-circuit current.

  In addition, when the first and second mechanical circuit breakers 1a and 1b are turned on from the initial state, even if a short circuit has already occurred, the power conversion circuit 6 is charged before both DC lines are closed. It becomes possible. As a result, when the first and second mechanical circuit breakers 1a and 1b are completely turned on, the breaking operation can be executed immediately, and the protection performance against accidents is improved.

[Embodiment 8]
FIG. 18 shows a DC circuit breaker according to the eighth embodiment. As shown in FIG. 18, the eighth embodiment is different from the seventh embodiment in that a DC capacitor is provided on the first DC system 10 side and the second DC system 20 side of the first and second mechanical circuit breakers 1a and 1b. 8a and 8b are provided. The same applies to the first mechanical circuit breaker 1 of the fifth and sixth embodiments.

  The operation and action of the DC interrupter according to the eighth embodiment will be described. Since the basic circuit opening operation is the same as that in the seventh embodiment, a description thereof will be omitted.

  The DC capacitor 8a functions during the shut-off operation. For example, a case where a short circuit occurs on the second DC system 20 side and the first mechanical circuit breaker 1a is interrupted will be described. By turning off the first and second semiconductor switches 42a and 42b of the first and second arm switch units 4a and 4b and then turning on the intermediate semiconductor switch 5, the power conversion circuit 6 is connected to both ends of the positive and negative DC lines. To generate a voltage.

  At that time, the current passes through the first mechanical circuit breaker 1 a from the positive side of the power conversion circuit 6, is divided into the DC capacitor 8 a and the DC load side of the first DC system 10, and flows to the negative side of the power conversion circuit 6. . The first DC system 10 is limited in current by impedance including internal impedance and line inductance.

  On the other hand, since the DC capacitor 8a becomes a low impedance transiently with the voltage change of the power conversion circuit 6, a large current easily flows instantaneously. As a result, the current to the power supply or load on the first DC system 10 side can be suppressed, and the reverse current to the first mechanical circuit breaker 1a can be quickly increased.

  Thereby, the opening speed of the first mechanical circuit breaker 1a can be increased. In addition, after the first mechanical circuit breaker 1a is opened, the DC capacitor 8a absorbs the energy of the line impedance of the power supply or load on the first DC system 10 side, thereby increasing the voltage of the first DC system 10. Can be suppressed.

  The above operation / action is the same for the DC capacitor 8b and the second mechanical circuit breaker 1b.

  As described above, according to the eighth embodiment, the breaking can be further speeded up by increasing the resonance current generated by the power conversion circuit 6 faster than the mechanical circuit breaker passing current.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Mechanical circuit breaker 2a, 2b ... Capacitor arm 3a, 3b, 3c ... Capacitor 4a, 4b ... Arm switch part 41a, 41b ... Resistor 42a, 42b ... Semiconductor switch 5 ... Intermediate semiconductor switch 6 ... Power conversion circuit 7 ... Inductor 8a, 8b ... DC capacitors

Claims (9)

A plurality of capacitors connected in parallel between the positive and negative electrodes of the DC line between the first and second DC systems;
A resistor and a semiconductor switch connected in series to each of the plurality of capacitors;
A series path connecting the plurality of capacitors in series;
An intermediate semiconductor switch provided between the capacitors of the series path;
An inductor provided in the series path;
A power conversion circuit having
A first mechanical circuit breaker connected between the power conversion circuit and a positive electrode or a negative electrode of the first DC system;
A direct current circuit breaker comprising: One end is connected to the negative electrode of the DC line between the first and second DC systems, a first arm switch unit in which a first resistor and a first semiconductor switch are connected in series, and one end is connected to the other end of the first arm switch unit A first capacitor arm having a first capacitor connected and having the other end connected to the positive electrode of the DC line;
One end is connected to the positive electrode of the DC line, a second arm switch unit in which a second resistor and a second semiconductor switch are connected in series, one end is connected to the other end of the second arm switch unit, and the other end is the DC A second capacitor arm having a second capacitor connected to the negative electrode of the line;
A common connection point of the first capacitor and the first arm switch unit is connected to a common connection point of the second capacitor and the second arm switch unit, and the first capacitor and the second capacitor are connected in series. A series path to
An intermediate semiconductor switch connected in series between the capacitors of the series path;
An inductor provided in the series path;
A power conversion circuit comprising:
A first mechanical circuit breaker connected between the power conversion circuit and a positive electrode or a negative electrode of the first DC system;
A direct current circuit breaker comprising: A first arm switch unit in which one end is connected to the negative electrode of the DC line between the first and second DC systems, a first resistor and a first semiconductor switch are connected in series, and one end is the other end of the first arm switch unit A first capacitor arm having a first capacitor connected to the other end of the DC line and connected to the positive electrode of the DC line;
One end of the DC line is connected to the positive electrode and has a positive electrode arm switch unit having a positive electrode semiconductor switch, and one end of the DC line is connected to the negative electrode of the negative electrode arm switch unit having a negative electrode semiconductor switch and the positive electrode arm switch unit. One or a plurality of second to n-1 th capacitor arms connected between the other end and the other end of the negative arm switch unit, or a plurality of second to n-1 th capacitor arms (n = An integer greater than or equal to 3),
One end is connected to the positive electrode of the DC line, an n-th arm switch unit in which an n-th resistor and an n-th semiconductor switch are connected in series, one end is connected to the other end of the n-th arm switch unit, and the other end is An nth capacitor arm having an nth capacitor connected to the negative electrode of the DC line;
A series path connecting the first to n-th capacitors in series;
An intermediate semiconductor switch provided between the capacitors of the series path;
An inductor provided in the series path;
A power conversion circuit comprising:
A first mechanical circuit breaker connected between the power conversion circuit and a positive electrode or a negative electrode of the first DC system;
A direct current circuit breaker comprising: A first arm switch unit in which one end is connected to the negative electrode of the DC line between the first and second DC systems, a first resistor and a first semiconductor switch are connected in series, and one end is the other end of the first arm switch unit A first capacitor arm having a first capacitor connected to the other end of the DC line and connected to the positive electrode of the DC line;
One end is connected to the positive electrode of the DC line, a second arm switch unit in which a second resistor and a second semiconductor switch are connected in series, one end is connected to the other end of the second arm switch unit, and the other end is A second capacitor arm having a second capacitor connected to the negative electrode of the DC line;
An intermediate capacitor arm in which a resistor and an intermediate capacitor are connected in series between the common connection point of the first resistor and the first semiconductor switch, and the common connection point of the second resistor and the second semiconductor switch;
A series path connecting the first capacitor, the intermediate capacitor, and the second capacitor in series;
An intermediate semiconductor switch provided between the first capacitor and the intermediate capacitor in the series path and between the intermediate capacitor and the second capacitor;
An inductor provided in the series path;
A power conversion circuit comprising:
A first mechanical circuit breaker connected between the power conversion circuit and a positive electrode or a negative electrode of the first DC system;
A direct current circuit breaker comprising:   5. The DC circuit breaker according to claim 4, wherein a plurality of intermediate capacitor arms are provided, and an intermediate semiconductor switch is connected between the intermediate capacitors of the plurality of intermediate capacitor arms.   6. The DC circuit breaker according to claim 2, wherein a DC capacitor is provided between positive and negative electrodes on the first DC system side of the first mechanical circuit breaker.   When a current flows from the first DC system to the second DC system, and an accident occurs in the second DC system, the semiconductor switch is turned off, the intermediate semiconductor switch is turned on, and the first machine The DC circuit breaker according to any one of claims 1 to 6, wherein the first mechanical circuit breaker is opened after a current flowing through the circuit breaker becomes a predetermined value or less.   The DC circuit breaker according to any one of claims 2 to 7, further comprising a second mechanical circuit breaker connected between the power conversion circuit and a positive electrode or a negative electrode of the second DC system. .   9. The DC circuit breaker according to claim 8, wherein a DC capacitor is provided between positive and negative electrodes on the second DC system side of the second mechanical circuit breaker.

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