JP2017130391A - Circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a circuit breaker which is capable of high voltage breaking and reduces cost, the circuit breaker being configured to make a stationary loss into zero at a normal time and to cut off a current path if an accident occurs.SOLUTION: A circuit breaker 1 comprises: a first inductor 11 including a first external connection terminal T; a switch 12 connected in series to the first inductor 11 and consisting of a mechanical breaker 24, a snubber circuit 25 connected in parallel thereto and a mechanical disconnector 26 connected in series to a parallel circuit consisting of the mechanical breaker 24 and the snubber circuit 25; a semiconductor power converter 13 provided on wiring branched from wiring connecting the first inductor 11 and the switch 12, and configured to output a predetermined DC current by performing a switching operation of an internal semiconductor switch; and a second inductor 14 connected in series to the semiconductor power converter 13. A unit that is configured by positioning the semiconductor power converter 13 and the second inductor 14 on the same wiring is connected in parallel to the switch 12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a circuit breaker that cuts off a current path when an accident such as a ground fault or a short circuit occurs, and more particularly to a hybrid circuit breaker that uses both a mechanical switch system and a semiconductor switch system.

  In recent years, power supply systems using direct current have attracted attention. The DC power supply system has an advantage that the converter loss, power transmission loss, and installation cost can be reduced as compared with the existing AC power supply system. In Japan, for example, a DC power supply system of DC 380 [V], converter capacity 500 [kW] class, trams (600 [V], 750 [V]) and DC trains (1000 [V], 1500 [V]) ) DC power supply system has been put into practical use. In high voltage applications of several tens [kV] or more, for example, assuming the introduction of a future large-scale offshore wind power generation system, a multi-terminal DC power transmission system (HVDC: high-voltage direct-current) using a voltage source converter is used. Is expected to be introduced.

  When a ground fault or short circuit accident occurs in a DC power supply system, an overcurrent occurs. The rate of increase in current from the occurrence of an accident ([A / s]) is inversely proportional to the DC inductance of the DC power supply system. For example, when a DC voltage is generated using a voltage source converter, since a DC inductance is small, an overcurrent may occur. Therefore, it is necessary to install a DC circuit breaker that can operate at high speed.

  DC circuit breakers can be classified into three types: mechanical switch system, semiconductor switch system, and hybrid system.

  Among these, the mechanical switch system cuts off the current by using a mechanical circuit breaker (circuit breaker) such as a vacuum circuit breaker, a gas circuit breaker or an air blowing circuit breaker and an LC resonance circuit. (For example, refer nonpatent literature 1.). In the mechanical switch system, no steady loss occurs because no power device is used.

  Moreover, the semiconductor switch system implement | achieves a high interruption | blocking time (1 [ms] or less) by comprising a circuit breaker using a power device (power semiconductor element) (for example, refer nonpatent literature 2). .

  In addition, the hybrid system has a feature in that both high-speed current interruption and loss reduction are achieved by using a mechanical circuit breaker capable of high-speed operation and a power device, and various circuits have been proposed (for example, (Refer nonpatent literature 3.). FIG. 15 is a circuit diagram illustrating a general hybrid circuit breaker. For example, as shown in FIG. 15, a hybrid circuit breaker 100 includes a current limiting inductor 151, a mechanical circuit breaker (circuit breaker) 152, a commutation auxiliary semiconductor switch 153, a main semiconductor switch 154, an arrester ( The main circuit is composed of 155 (non-linear resistance). In normal operation, power is supplied to the load via the current limiting inductor 151, the mechanical circuit breaker 152, and the commutation auxiliary semiconductor switch 153, and the commutation auxiliary semiconductor switch 153 is turned off in the event of an accident such as a ground fault or a short circuit. Commutates to the main semiconductor switch 154. Since the required withstand voltage of the commutation auxiliary semiconductor switch 153 is about several percent of that of the main semiconductor switch 154, there is an advantage that steady loss can be reduced as compared with the semiconductor switch system. Further, the time required for commutation is 0.2 [ms] or less, and by using the mechanical circuit breaker 152 that can be opened within 1 [ms], the interruption time is set to 2 [ms] or less. Can do.

B. Bachmann, G. Mauthe, E. Ruoss, HP Lips, “500kV wind-cooled high-voltage DC power supply Circuit of Device (Development of a 500 kV Airblast HVDC Circuit Breaker), (USA), Institute of Electrical and Electronics Engineers (IEEE Transactions), Electrical Equipment and Systems (Power Apparatus and Systems, 104) 9, pp. 2460-2466, September 1985 By C. Meyer, S. Schroder, RW De Donker, "Solid state circuit interruption for medium voltage systems with distributed power systems" Devices and Current Limiters (Solid-State Circuit Breakers and Current Limiters for Medium-Voltage Systems Having Distributed Power Systems) (USA), Institute of Electrical and Electronics Engineers (IEV) 19, no. 5, pp. 1333-1340, September 2004 "New medium voltage hybrid current limiting circuit breaker: Principle" by M. Steiler, K. Frohlich, W. Holaus, K. Kaltenegger And test results (A Novel Hybrid Current-Limiting Circuit Breaker For Medium Voltage: Principle and Test Results) (USA), Institute of Electrical and Electronics Engineers of Japan (IEEE Transactions), Power Del. pp. 460-467, April 2003

  Although the circuit breaker using the mechanical switch system has an advantage that no steady loss occurs because a power device is not used, the time required until the current is interrupted (opening time) is as long as 30 to 100 [ms]. Although it can be applied to a large current source converter, application to a voltage source converter is difficult.

  Further, the circuit breaker using the semiconductor switch method has a problem in that a steady loss occurs because a current constantly flows through the internal semiconductor switch. Further, since a high voltage higher than the direct current voltage is applied to the internal semiconductor switch when the current is interrupted, it is necessary to increase the breakdown voltage by connecting a plurality of power devices in series. In this case, an increase in the on-voltage of the semiconductor switch becomes a problem. For example, in the case of direct current 320 [kV], the ON voltage of the semiconductor switch is 100 [V] or more. Since current constantly flows through the semiconductor switch, it is a problem to reduce loss due to the on-voltage.

  In addition, the hybrid circuit breaker described above can reduce the steady loss compared to the semiconductor switch method because the required withstand voltage of the commutation auxiliary semiconductor switch is about several percent of that of the main semiconductor switch. Even if it compares, there exists an advantage which can shorten interruption | blocking time. However, since a steady current still flows through the commutation auxiliary semiconductor switch in a normal state, the steady loss cannot be made zero.

  In addition, with the expansion of the application range of future high-voltage DC power supply systems, it is desired to develop a low-cost DC interruption system capable of interrupting DC high voltage.

  Therefore, in view of the above problems, an object of the present invention is to provide a low-cost circuit breaker capable of interrupting a DC high voltage, in which a steady loss is zero in a normal state and a current path can be interrupted at a high speed when an accident occurs. There is.

  In order to achieve the above object, according to the present invention, a circuit breaker is connected in series to a first inductor having a first external connection terminal and the first inductor, and the first inductor is connected. A switch having a second external connection terminal on the side opposite to the connected side, and a mechanical circuit breaker that opens in response to a command and interrupts the current path, in parallel with the mechanical circuit breaker A switch comprising: a snubber circuit to be connected; and a mechanical disconnector connected in series to a parallel circuit including a mechanical circuit breaker and a snubber circuit, and opening the current according to a command to interrupt a current path; One or more semiconductor power converters cascade-connected to each other provided on a wiring branched from a wiring connecting the first inductor and the switch, and commanding a semiconductor switch provided therein According to switching A semiconductor power converter that outputs a predetermined direct current and a second inductor connected in series to the semiconductor power converter, the semiconductor power converter and the second inductor being the same A unit located on the wiring is connected in parallel to the switch.

  Here, the semiconductor power converter is connected to the first DC side to which the second inductor or another semiconductor power converter different from the semiconductor power converter is connected by the switching operation of the semiconductor switch, and the first DC. A DCDC converter that converts a DC current input from one of the second DC sides opposite to the DC side into a DC current of a desired magnitude and polarity and outputs the DC current to the other, A DCDC converter capable of switching the output direction bi-directionally between the first DC side and the second DC side; an energy storage unit connected in parallel to the second DC side of the DCDC converter; and an energy storage unit The DC voltage applied to the energy storage unit is in parallel when the DC voltage is lower than the preset voltage, and shows a predetermined resistance value. Otherwise, the resistance value is lower than the predetermined resistance value. And a nonlinear resistor shown, may have a.

  The energy storage unit may include a capacitor and a reverse blocking diode connected in series to the capacitor and blocking a charging current flowing into the capacitor.

  The energy storage unit includes a first capacitor connected in parallel to the non-linear resistance, a capacitance larger than the capacitance of the first capacitor, and a charging voltage lower than the charging voltage of the first capacitor. A second capacitor, and a reverse blocking diode connected in series to the second capacitor and blocking a charging current flowing into the second capacitor, and comprising the second capacitor and the reverse blocking diode A series circuit may be connected in parallel to the first capacitor.

  Further, the second inductor may be connected in series to any one of the plurality of semiconductor power converters cascade-connected to each other.

  The circuit breaker includes an overcurrent detection unit that detects whether an overcurrent has occurred on the external wiring connected to the first external connection terminal or the second external connection terminal, a mechanical circuit breaker, A control unit that controls the opening operation for the mechanical disconnector and the power conversion operation of the semiconductor power converter, and the control unit opens the mechanical circuit breaker after the overcurrent is detected by the overcurrent detection unit. A first command means for outputting a mechanical breaker opening command for instructing the start of a pole operation; and after detecting an overcurrent by the overcurrent detector, opening the mechanical breaker based on the opening command for the mechanical breaker A second command means for outputting a power conversion command for causing the semiconductor power converter to output a direct current that causes the current flowing through the mechanical circuit breaker to converge to substantially zero until the pole operation is completed; and for the mechanical circuit breaker Predetermined after the opening command is output After the elapse of time, the third command means for outputting a mechanical disconnector opening command for instructing the mechanical disconnector to start the opening operation, and when the opening operation of the mechanical breaker is completed, the semiconductor And fourth command means for outputting an off command for turning off the semiconductor switch in the power converter.

  The snubber circuit described above may be formed of a series circuit of a snubber capacitor and a snubber resistor.

  In addition, the semiconductor switch may include a semiconductor switching element that allows current to flow in one direction when it is on, and a feedback diode that is connected in reverse parallel to the semiconductor switching element.

  The mechanical circuit breaker may include a fixed contact and a movable contact that is movable between a closed position that contacts the fixed contact and an open position that is separated from the fixed contact. .

  According to the present invention, it is possible to realize a low-cost circuit interruption device capable of interrupting a DC high voltage, in which a steady loss is zero in a normal state and a current path can be interrupted at a high speed when an accident occurs.

  The circuit breaker according to the present invention is a so-called hybrid circuit breaker including a mechanical circuit breaker, a mechanical disconnector, and a semiconductor power converter. However, in a normal state, the mechanical circuit breaker and the mechanical disconnector are turned on and the power source side Since power is supplied from the power source to the load side and the semiconductor power converter only operates as a diode, the steady loss of the circuit breaker in a normal state can be made zero.

  Further, according to the present invention, when an overcurrent occurs due to a ground fault or a short-circuit accident, the current path can be changed at high speed by appropriately controlling the operation of the mechanical breaker, the mechanical disconnector, and the semiconductor power converter. Can be blocked.

  Further, according to the present invention, the combination of the mechanical circuit breaker, the mechanical disconnection circuit, and the snubber circuit is used as the mechanical circuit breaker for the current path, so that both the mechanical circuit breaker and the mechanical disconnection circuit are opened. In the state, the voltage applied between the mechanical contacts of the mechanical breaker with the snubber circuit connected in parallel is smaller than the voltage applied between the mechanical contacts of the mechanical disconnector. That is, according to the present invention, most of the voltage applied to the switch at the time of circuit interruption is applied to a mechanical disconnector with low cost, so a low-cost circuit interruption device capable of interrupting high DC voltage is provided. Can be realized.

  Further, according to the present invention, it is possible to increase the withstand voltage of the circuit breaker by appropriately adjusting the number of semiconductor power converters connected in cascade.

  Further, according to the present invention, the DCDC converter in the semiconductor power converter is configured as a four-quadrant DCDC converter, so that the current path can be interrupted regardless of the amplitude and polarity of the direct current.

1 is a circuit diagram showing a circuit breaker according to a first embodiment of the present invention. It is a circuit diagram explaining the semiconductor power converter in the circuit breaker by the 1st example of the present invention. FIG. 3 is a circuit diagram (part 1) for explaining an arrangement example of a second inductor in the circuit breaker according to the first embodiment of the present invention. FIG. 6 is a circuit diagram (part 2) for explaining an arrangement example of the second inductor in the circuit breaker according to the first embodiment of the present invention. FIG. 6 is a circuit diagram (No. 3) for explaining an arrangement example of the second inductor in the circuit breaker according to the first embodiment of the present invention. It is a block diagram explaining the control system in the circuit breaker by the 1st example of the present invention. It is a flowchart which shows the operation | movement flow of the circuit breaker by the 1st Example of this invention. It is a control block diagram explaining the power conversion command for controlling the converter electric current in the semiconductor power converter in the circuit breaker by the 1st example of the present invention. It is a figure explaining the circuit parameter used for simulation and experiment. It is a figure which shows the experimental waveform of the circuit breaker by the 1st Example of this invention. It is a figure which shows the enlarged waveform (waveform before and behind opening a mechanical circuit breaker and a mechanical disconnector) of FIG. It is a figure which shows the simulation waveform of the circuit breaker by the 1st Example of this invention. It is a figure which shows the enlarged waveform (waveform before and behind opening a mechanical circuit breaker and a mechanical disconnector) of FIG. It is a circuit diagram explaining the circuit breaker by the 2nd example of the present invention. It is a circuit diagram which illustrates a general circuit breaker of a hybrid system.

  The circuit breaker according to the present invention includes a first inductor, a mechanical breaker, a semiconductor power converter, and a second inductor. The first inductor has a first external connection terminal at one end. The mechanical circuit breaker is opened in response to a command to interrupt the current path, and is connected in series to the first inductor, and is connected to the side opposite to the side to which the first inductor is connected. 2 external connection terminals. The semiconductor power converter outputs a predetermined direct current by switching a semiconductor switch provided therein in accordance with a command, and branches from a wiring connecting the first inductor and the mechanical circuit breaker. These wirings are provided alone or in a state where a plurality of them are cascade-connected to each other. The second inductor is connected in series with the semiconductor power converter or mechanical breaker. One of the first inductor and the second inductor is an accident current limiting inductor, and the other is a current control inductor. Hereinafter, specific circuit configurations will be described in the first to third embodiments.

  FIG. 1 is a circuit diagram illustrating a circuit breaker according to a first embodiment of the present invention, and FIG. 2 is a circuit diagram illustrating a semiconductor power converter in the circuit breaker according to the first embodiment of the present invention. is there. Hereinafter, components having the same reference numerals in different drawings mean components having the same functions.

  The circuit breaker 1 according to the first embodiment of the present invention includes a first inductor 11, a switch 12, a semiconductor power converter 13, and a second inductor 14. The circuit breaker 1 according to the first embodiment of the present invention is installed such that the semiconductor power converter 13 is in series with the applied DC power supply system. In this embodiment, the case where the circuit breaker 1 operates as a DC breaker will be described. In this case, the circuit breaker 1 is installed on the DC power supply system so that the first inductor 11 is on the power supply side and the switch 12 is on the load side.

The first inductor 11 has a first external connection terminal T ₁ at one end. A circuit on the power supply side is connected to the first external connection terminal T ₁ .

The switch 12 is connected in series to the first inductor 11 and has a second external connection terminal T ₂ on the side opposite to the side to which the first inductor 11 is connected. Circuit on the load side is connected to the second external connection terminal T _2. The switch 12 includes a mechanical breaker 24, a snubber circuit 25, and a mechanical disconnector 26.

  The mechanical circuit breaker 24 is opened in accordance with the mechanical circuit breaker command to interrupt the current path. The mechanical circuit breaker 24 has a fixed contact, a movable contact that can move between a closed position that contacts the fixed contact and an open position that is separated from the fixed contact, and is movable in response to a command. The contact is separated from the stationary contact and opened to interrupt the current path. Examples of the mechanical circuit breaker 24 include a vacuum circuit breaker, a gas circuit breaker, or an air blowing circuit breaker.

The snubber circuit 25 is connected in parallel to the mechanical circuit breaker 24. In this embodiment, the snubber circuit 25 is constituted by an RC snubber circuit in which a snubber capacitor 51 (capacitance C _S ) and a snubber resistor 52 (resistance value R _S ) are connected in series. A snubber circuit may be realized with this. When the snubber circuit 25 is an RC snubber circuit, each circuit parameter may be appropriately set by simulation or experiment. For example, the capacitance C _S of the snubber capacitor 51 is 9.6 [nF], and the snubber circuit 25 is a snubber circuit. The resistance value R _S of the resistor 52 is set to 1560 [Ω].

  The mechanical disconnector 26 is opened in accordance with the mechanical disconnector command to interrupt the current path. Unlike the mechanical circuit breaker 24, the mechanical disconnector 26 does not have an arc extinguishing capability, and does not open and close when current is flowing through the current path, and opens and closes the current path in a no-load state. . The mechanical disconnector 26 is also referred to as DS or DISCON.

  Thus, in the present invention, the mechanical circuit breaker 24 and the mechanical circuit breaker 26 are used in combination as current path interruption means in the switch 12. With this configuration, the voltage applied to the switch 12 as a whole is divided into a voltage applied to the mechanical circuit breaker 24 and a voltage applied to the mechanical disconnector 26. . In a state where both the mechanical circuit breaker 24 and the mechanical disconnector 26 are open, the voltage applied between the mechanical contacts of the mechanical circuit breaker 24 to which the snubber circuit 25 is connected in parallel is the mechanical disconnector 26. It becomes smaller than the voltage applied between the mechanical contacts. In general, the price of the mechanical disconnector 26 is significantly lower than the price of the mechanical circuit breaker 24. Therefore, the circuit breaker 1 according to the present invention that applies most of the voltage applied to the switch 12 at the time of circuit breakage to the inexpensive mechanical disconnector 26 is used when the DC voltage is very high (for example, 250 [ kV]).

  The semiconductor power converter 13 is provided on a wiring branched from the wiring connecting the first inductor 11 and the switch 12 singly or in a state where a plurality thereof are cascade-connected to each other. In the present specification, when the number of semiconductor power converters 13 is one, the side to which the second inductor 14 is connected is referred to as a “first DC side”, and a plurality of semiconductor power converters 13 are cascaded together. In the case of connection, the side to which another semiconductor power converter 13 different from the semiconductor power converter 13 is connected is also referred to as “first DC side”. The DC side opposite to the “first DC side” is referred to as a “second DC side”. As an example, FIG. 1 shows a case where a plurality (N, where N is an integer of 2 or more) semiconductor power converters 13 are cascade-connected to each other on the first DC side. By simply adjusting the number of semiconductor power converters 13 connected in cascade, the circuit breaker 1 can be easily increased in breakdown voltage.

  The semiconductor power converter 13 includes a DCDC converter 21, an energy storage unit 22, and a non-linear resistor 23. The semiconductor power converter 13 performs a switching operation according to a command on a semiconductor switch provided in the DCDC converter 21, and thereby performs a predetermined operation. Outputs direct current.

  The DCDC converter 21 in the semiconductor power converter 13 is configured as a so-called four-quadrant DCDC converter. That is, the DCDC converter 21 converts the direct current input from one of the first direct current side and the second direct current side into a direct current having a desired magnitude and polarity by the switching operation of the semiconductor switch S. It outputs to one side, and the input / output direction of the direct current can be switched bidirectionally between the first direct current side and the second direct current side. By configuring the DCDC converter 21 in the semiconductor power converter 13 as a four-quadrant DCDC converter, the current path can be interrupted regardless of the amplitude and polarity of the direct current. The semiconductor switch includes a semiconductor switching element S that allows current to flow in one direction when it is turned on, and a feedback diode D that is connected to the semiconductor switching element S in antiparallel. Examples of the semiconductor switching element S include an IGBT, a thyristor, a GTO (Gate Turn-OFF thyristor), a transistor, and the like, but the type of the switching element itself does not limit the present invention, and other semiconductors. It may be an element.

  The energy storage unit 22 in the semiconductor power converter 13 is connected in parallel to the second DC side of the DCDC converter 21. In the present embodiment, the energy storage unit 22 includes a series circuit including a DC capacitor 53 and a reverse blocking diode 54 that is connected in series to the DC capacitor 53 and blocks a charging current flowing into the DC capacitor 53. In order to initially charge the DC capacitor 53, it is necessary to separately provide an initial charging circuit, but the illustration is omitted here.

The non-linear resistance 23 in the semiconductor power converter 13 is connected in parallel to the energy storage unit 22, and a DC voltage applied to the energy storage unit 22 is set to a preset voltage (hereinafter referred to as “operation voltage”). In the following cases, the element has a predetermined resistance value, and in other cases, the element has a resistance value lower than the predetermined resistance value. As an example of the non-linear resistance 23, there is MOV (Metal Oxide Variable Resistor) (also referred to as “varistor” or “arrester”). The operating voltage of the nonlinear resistor 23 is limited to the voltage rating of the power device used. For example, when a power device having a breakdown voltage of 3.3 [kV] is used, the operating voltage V _Clamp of the nonlinear resistor 23 needs to be set to 3.3 [kV] or less.

  Since the DC capacitor 22 and the non-linear resistor 23 are connected in parallel, when the DC capacitor 22 is charged by the energy accumulated in the first inductor 11 and the second inductor 14, the DC capacitor 22 is charged. When the voltage gradually increases and reaches the operating voltage of the non-linear resistor 23, the charging voltage of the DC capacitor 22 is clamped by the operating voltage of the non-linear resistor 23 and then accumulated in the first inductor 11 and the second inductor 14. The consumed energy is consumed by the non-linear resistance 23. The energy storage unit 22 and the non-linear resistor 23 may be realized by other elements as long as they perform a series of operations of charging the DC capacitor 22 and consuming by the non-linear resistor 23 as described above. It may be replaced with a secondary battery or an electric double layer capacitor.

  The second inductor 14 is connected in series with the semiconductor power converter 13. When the plurality of semiconductor power converters 13 are cascade-connected to each other, the second inductor 14 is connected in series to any one of the plurality of semiconductor power converters 13 cascade-connected to each other. Connected. 3 to 5 are circuit diagrams for explaining an arrangement example of the second inductor in the circuit breaker according to the first embodiment of the present invention. For example, as shown in FIG. 3 and FIG. 4, the second inductor 14 includes the semiconductor power converter 13 of any one of the semiconductor power converters 13 located at both ends of the cascade connection. Installed on the unconnected side. Further, for example, as shown in FIG. 5, the second inductor 14 is installed between the semiconductor power converters 13 adjacent to each other.

  When there is one semiconductor power converter 13, the second inductor 14 is simply connected in series to the semiconductor power converter 13.

  In either case where a plurality of semiconductor power converters 13 are cascade-connected or where there is one semiconductor power converter 13, the semiconductor power converter 13 and the second inductor 14 are on the same wiring. The unit located is connected in parallel to the switch 12. That is, the unit in which the semiconductor power converter 13 and the second inductor 14 are located on the same wiring is connected to the connection point A between the first inductor 11 and the switch 12.

In the first embodiment of the present invention, the first inductor 11, the switch 12, the semiconductor power converter 13, and the second inductor 14 are connected as described above. Ground terminals G ₁ and G ₂ are provided corresponding to the first external connection terminal T ₁ and the second external connection terminal T _2, respectively.

In this embodiment, the case where the circuit breaker 1 operates as a DC circuit breaker has been described. However, the circuit breaker 2 can operate as an AC circuit breaker in addition to operating as a DC circuit breaker. The terminals G ₁ and G ₂ are terminals having polarities opposite to those of the first external connection terminal T ₁ and the second external connection terminal T ₂ . When the circuit breaker 1 operates as an AC circuit breaker, the DCDC converter 21 in the semiconductor power converter 13 operates as a DCAC converter (DC AC converter). In this case, the DC side of the DCAC converter corresponds to the “second DC side” described above, and the AC side corresponds to the “first DC side” described above.

In the example shown in FIG. 1, the side consisting of the first external connection terminal T ₁ and the ground terminal G ₁ is the power supply side, and the side consisting of the second external connection terminal T ₂ and the ground terminal G ₂ is the load side. Accordingly, the first inductor 11 functions as an accident current limiting inductor, and the second inductor 14 functions as a current control inductor.

Thereafter, the power source side DC voltage is V _dc , the load voltage is v _L , the voltage appearing at both ends of the mechanical breaker 24 is v _CB , the voltage appearing at both ends of the mechanical disconnector 26 is v _DS , and the semiconductor power converter 13. The total voltage of the semiconductor power converters 13 on the cascade-connected side is represented by v _HB . Moreover, the voltage of the DC capacitor connected in parallel to each semiconductor power converter 13 is represented by v _C1 ,..., V _CN (where N is a natural number). A voltage appearing at both ends of the nonlinear resistor 23 is represented by v _MOV . Further, the current flowing from the first external connection terminal T ₁ to the connection point A is the power supply current i _S , the current flowing from the connection point A to the second external connection terminal T ₂ is the load current i _CB , and the connection point A The current flowing to the semiconductor power converter 13 is defined as a converter current i _Con . For the voltage and current in the figure, the direction of the arrow is positive.

  FIG. 6 is a block diagram illustrating a control system in the circuit breaker according to the first embodiment of the present invention. The circuit breaker 1 has an overcurrent detection unit 31 and a control unit 32 as its control system.

Overcurrent detection unit 31, the overcurrent is detected whether or not generated in the second external connection terminal T ₂ connected to a load side of the external wiring. In this embodiment, since the side composed of the second external connection terminal T ₂ and the ground terminal G ₂ is the load side, the overcurrent detection unit 31 is connected to the load side connected to the _second external connection terminal T ₂ . Although the presence or absence of the occurrence of overcurrent on the external wiring is detected, when the side including the first external connection terminal T ₁ and the ground terminal G ₁ is the load side, the overcurrent detection unit 31 The occurrence of overcurrent on the external wiring on the load side connected to _one external connection terminal T ₁ may be detected. The detection of overcurrent generation by the overcurrent detection unit 31 may be realized by a known method. For example, if an accident such as a ground fault or a short circuit occurs, the power supply current i _S increases. Therefore, the power supply current i _S is constantly monitored using a current detector (not shown), and the power supply current i _S is determined from the rated current. It is determined that “overcurrent has occurred” when the value becomes larger. What is necessary is just to set the reference current value used for judgment of overcurrent generation suitably as needed, such as setting to the rated current 120%.

  The control unit 32 controls the opening operation for the mechanical circuit breaker 24 and the mechanical disconnector 26 in the switch 12 and the power conversion operation of the semiconductor power converter 13. That is, after the overcurrent detection unit 31 detects an overcurrent, the control unit 32 outputs a mechanical circuit breaker opening command for instructing the mechanical circuit breaker 24 to start the opening operation. 41 and the current flowing through the mechanical circuit breaker 24 between the detection of the overcurrent by the overcurrent detection unit 31 and the completion of the opening operation of the mechanical circuit breaker 24 based on the opening command for the mechanical circuit breaker. A second command means 42 for outputting a power conversion command for causing the semiconductor power converter 13 to output a direct current that converges to zero, and a mechanical breaker opening command is output after a predetermined period of time has elapsed. The third command means 43 for outputting a mechanical disconnector opening command for instructing the disconnector 26 to start the opening operation, and when the opening operation of the mechanical breaker 24 is completed, the semiconductor power converter Finger to turn off the semiconductor switch S in 13 A fourth command means 44 for outputting, with a.

  The first command means 41, the second command means 42, the third command means 43, and the fourth command means 44 may be constructed in a software program format, for example, or a combination of various electronic circuits and software programs It may be built with. For example, when these means are constructed in a software program format, the arithmetic processing unit in the control unit 32 operates according to this software program, thereby realizing the functions of the above-described means.

FIG. 7 is a flowchart showing an operation flow of the circuit breaker according to the first embodiment of the present invention. Here, as an example, let us consider a case where an overcurrent occurs due to a ground fault or short circuit accident on the load side at time t ₀ .

The circuit breaker 1 performs normal operation when no overcurrent is generated on the load side (step S101). That is, at the normal time, the mechanical circuit breaker 24 and the mechanical disconnector 26 in the switch 12 are turned on, and power is supplied from the power source side to the load side. At this time, when each diode D in the semiconductor power converter 13 functions, the semiconductor power converter 13 itself operates as a diode, and the converter current i _Con becomes zero. Therefore, the steady loss of the circuit breaker 1 at the normal time is zero. Note that the capacitor C in the semiconductor power converter 13 is initially charged.

Under normal conditions, according to Kirchhoff's current law, the load current i _CB and the power supply current i _S are equal, that is, “i _CB = i _S ”. In addition, since the voltage drop in the first inductor L ₁ is zero under normal conditions, the load voltage v _L and the power supply side DC voltage V _dc are equal, that is, “v _L = V _dc ”.

In step S102, the overcurrent detection unit 31, the overcurrent is detected whether or not generated in the second external connection terminal T ₂ connected to a load side of the external wiring. When the overcurrent detector 31 does not detect an overcurrent, the process returns to step S101 and continues normal operation. When the overcurrent detection unit 31 detects an overcurrent, the process proceeds to step S103.

For example, it is assumed that the overcurrent detection unit 31 detects the occurrence of an overcurrent at time t ₁ . At this time, if the voltage drop in the switch 12 is ignored for the circuit breaker 1, the circuit equation shown in Equation 1 is established.

From Expression 1, the power supply current i _S and the load current i _CB are expressed as Expression 2. However, in Equation 2, I ₀ represents the current at time t ₀ .

As can be seen from Equation 2, the power supply current i _S and the load current i _CB increase in a linear function with a slope of “V _dc / L ₁ ”. That is, if the inductance L ₁ of the first inductor 11 is increased, the current increase rate at the time of the accident can be suppressed. Since the power supply current i _S increases when a short circuit or ground fault occurs, the overcurrent detection unit 31 constantly monitors the power supply current i _S using a current detector (not shown), and the power supply current i _S is rated. When it becomes larger than the current by a predetermined value (for example, rated current 120%), it is determined that “overcurrent has occurred” (time t ₁ ). The time “t ₁ −t ₀ ” required from the occurrence of the accident to the judgment of the accident depends on the power source side DC voltage V _dc , the inductance L ₁ of the first inductor, the load, the reference current value, and the like.

  When the overcurrent detection unit 31 detects an overcurrent in step S102, in step S103, the second command means 42 of the control unit 32 starts the opening operation of the mechanical circuit breaker 24 after the opening command is output. A power conversion command for causing the semiconductor power converter 13 to output a direct current that converges the current flowing through the mechanical circuit breaker 24 to substantially zero until completion is output.

  When the overcurrent detection unit 31 detects an overcurrent in step S102, the first command means 41 of the control unit 32 commands the mechanical circuit breaker 24 to start the opening operation in step S103. Outputs opening command for mechanical circuit breaker.

  Note that the process in step S103 and the process in step S104 may be executed simultaneously, or alternatively, the order of the processes in step S103 and step S104 may be changed.

When a mechanical circuit breaker opening command is given to the mechanical circuit breaker 24 in step S104, the mechanical circuit breaker 24 starts the opening operation (step S105). However, the opening operation is not immediately completed. A delay time due to the mechanical structure of the mechanical circuit breaker 24 occurs, and the mechanical circuit breaker 24 actually opens the operation with a slight delay from the output of the mechanical circuit breaker opening command by the first command means 41. To complete. For example, a delay time of about 1 [ms] or less occurs when the DC voltage is several tens [kV] class and about 2 [ms] when several tens [kV] class. As described above, the mechanical circuit breaker 24 can break the current path when the current is a very small value (for example, several [mA] to several tens [mA]). It is necessary to make the flowing load current i _CB as zero as possible. Therefore, in step S103, the second command means 42 of the control unit 32 determines the current flowing through the mechanical circuit breaker 24 after the opening command is output until the opening operation of the mechanical circuit breaker 24 is completed. A power conversion command for causing the semiconductor power converter 13 to output a direct current that converges to substantially zero is output. The semiconductor switching element S of the semiconductor switch in the DCDC converter 21 in the semiconductor power converter 13 performs a PWM switching operation based on the received power conversion command. Thus, the semiconductor power converter 13 is equivalent to operating as a control voltage source that outputs the voltage v _HB . At this time, a circuit equation like Formula 3 is established.

In the first embodiment of the present invention, the control voltage source is realized by PI control as an example, and v _HB is given by Equation 4. In Formula 4, K _p denotes a proportional gain, K _I denotes integral gain, i ^* _Con indicates a command value of the converter current. In this embodiment, PI control is applied, but current control other than PI control may be applied.

  In Equation 4, the right side corresponds to feedback control (PI). Substituting Equation 4 into Equation 3 yields Equation 5.

As shown in Equation 5, the converter current i _Con responds to the command value i ^* _Con with a second order delay. At this time, the load current i _CB can be made zero by setting the converter current command value i ^* _Con to i _S and controlling the converter current i _Con to match the power supply current i _S. The time required to make the load current i _CB zero (that is, the time required to match the converter current i _Con to the power supply current i _S ) is the carrier frequency, equivalent switching frequency, digital control of the semiconductor power converter 13. Depends on the method. For example, if a high-voltage SiC MOSFET capable of realizing low loss and high switching frequency operation is used, it is sufficiently possible to realize the time required to make the load current i _CB zero at 1 [ms] or less.

Based on the above, the generation principle of the power conversion command based on Equation 4 will be described as follows. FIG. 8 is a control block diagram for explaining a power conversion command for controlling the converter current in the semiconductor power converter in the circuit breaker according to the first embodiment of the present invention. In the control of the converter current, feedback control is used. In block B1 related to feedback control, PI control is applied to the difference between the converter current i _Con detected by the current detector (not shown) and the power source current i _S detected by the current detector (not shown). This suppresses the deviation “i _Con −i _S ”. A power conversion command v ^* _j for each semiconductor power converter 13 is generated from the output of the block B1. The power conversion command v ^* _j for each semiconductor power converter 13 is standardized with a DC capacitor voltage v _Cj (where j = 1 to N) in block B4 _j , and then a general PWM modulation method (triangular wave comparison) Is applied to the semiconductor switch S in each semiconductor power converter 13. Here, by applying “phase shift PWM” that shifts the initial phase of the triangular wave carrier used for PWM control of each semiconductor power converter 13 by 180 ° / N, the equivalent switching frequency can be increased. Specifically, assuming that the carrier frequency is f _C , the equivalent switching frequency is 2Nf _C. By setting the equivalent switching frequency high, it is possible to improve the current control system and reduce the inductance of the second inductor 14 as a current control inductor.

  Generally, the switching frequency of a semiconductor power converter for high voltage applications is set to several hundreds [Hz] from the viewpoint of reducing switching loss. On the other hand, since the semiconductor power converter 13 in the circuit breaker 1 according to the first embodiment of the present invention performs the PWM operation only when an accident occurs, an increase in switching loss is not a problem. When the semiconductor power converter 13 is, for example, a 3.3 [kV] / 1500 [A] SiC power module (SiC MOSFET and SiC SBD (Schottky Barrier Diode)), the carrier frequency of several [kHz] is used for PWM modulation. Application is expected, and improvement of current controllability can be expected. Assuming the same carrier frequency, current controllability is improved in high voltage applications where the number of cascades of the semiconductor power converter 13 is increased.

  Returning to FIG. 5, in step S <b> 105, the mechanical circuit breaker 24 starts the opening operation in response to the opening command from the second command means 42 in the control unit 32. As described above, the mechanical circuit breaker 24 can interrupt the current path when the current is a very small value (for example, several [mA] to several tens [mA]). The process of making the current flowing through 24 substantially zero is executed in a time sufficiently shorter than the time required for the opening operation of the mechanical circuit breaker 24 to be completed after the opening command for the mechanical circuit breaker is output.

After the opening operation of the mechanical circuit breaker 24 is completed (that is, after a predetermined period of time has elapsed since the first command means 41 outputs a mechanical circuit breaker opening command), a third command in the control unit 32 is provided. In step S106, the means 43 outputs a mechanical disconnector opening command for instructing the mechanical disconnector 26 to start the opening operation (time t ₂ ). The time required for the opening operation to be completed after the mechanical circuit breaker 24 receives the opening instruction for the mechanical circuit breaker can be known from experiments, the specifications of the mechanical circuit breaker 24, etc. The timing for outputting the mechanical disconnector opening command by the third command means 43 takes into account the time, and after a predetermined period has elapsed since the first command means 41 outputs the mechanical breaker opening command. You only have to set it.

  In step S <b> 107, the mechanical disconnector 26 starts the opening operation in response to the mechanical disconnector opening command from the third command means 43.

After the opening operation of the mechanical disconnector 26 is completed, in step S108, the fourth command means 44 in the control unit 32 outputs a command to turn off all the semiconductor switches S in the semiconductor power converter 13. (Time t ₃ ). Upon receiving the off command from the third command means 43 in the control unit 32, all the semiconductor switches S in the semiconductor power converter 13 are turned off, and the power conversion operation ends. Thereby, only each diode D in the semiconductor power converter 13 functions. At this time, the stored energy of the first inductor 11 and the second inductor 14 is released to the DC capacitor 22 and the non-linear resistance 23 via the feedback diode D. Since the DC capacitor 22 and the non-linear resistor 23 are connected in parallel, after the semiconductor switch S is turned off (that is, after the time t ₃ ), the direct current is accumulated by the accumulated energy of the first inductor 11 and the second inductor 14. is charged capacitor 22, the voltage v _c, after gradually increased, it is clamped in the operating voltage V _clamp nonlinear resistor 23. After the DC capacitor 22 is charged to the operating voltage, the stored energy is consumed by the non-linear resistance 23.

  Until the DC capacitor 22 is charged to the operating voltage of the nonlinear resistor 23 by the stored energy, the circuit equation shown in Equation 6 holds.

From Equation 6, the voltage v _C of the DC capacitor 22 and the power supply current i _S (= i _Con ) can be calculated by solving a second-order constant coefficient linear differential equation.

After the DC capacitor 22 is charged to the operating voltage, the circuit equation shown in Equation 7 is established. In Equation 7, the operating voltage of the nonlinear resistor 23 is V _Clamp .

From Equation 7, the power supply current i _S and the converter current i _Con can be calculated by solving a first-order constant coefficient linear differential equation.

Next, simulation results and experimental results of the circuit breaker according to the first embodiment of the present invention will be described. FIG. 9 is a diagram for explaining circuit parameters used for simulation and experiment. “PSCAD / EMTDC” was used for the simulation. The rated DC power supply voltage V _dc was 300 [V], the rated power supply current _IS was 150 [A], and the load R was 2 [Ω]. The inductance L ₁ of the first inductor (accident current limiting inductor) was set to 6 [mH] so that the current increase rate V _dc / L ₁ was 50 [A / ms]. The number N of the semiconductor power converters 13 is three. A phase shift PWM is applied to the triangular wave carrier of the semiconductor power converter 13. An IGBT was used for the semiconductor switching element of the semiconductor power converter 13. The unit electrostatic constant H is a value (unit: [s]) obtained by normalizing the total electrostatic energy of the DC capacitor by the converter capacity, and can be expressed by Expression 8. In Equation 8, P is a rated capacity (unit: [W]).

The dead time of the semiconductor switching element was 4 [μs]. The reference current value used for determining the occurrence of an accident was set at a rated current of 120%. The non-linear resistance 23 has an operating voltage V _Clamp of 300 [V] and exhibits an infinite resistance value when the applied voltage is 300 [V] or less, and a resistance value of zero when the voltage is 300 [V] or more. As shown.

FIG. 10 is a diagram showing experimental waveforms of the circuit breaker according to the first embodiment of the present invention. Moreover, FIG. 11 is a figure which shows the enlarged waveform (waveform before and behind opening a mechanical circuit breaker and a mechanical disconnecting switch) of FIG. 10 and FIG. 12 described later, the load current i _CB flowing from the connection point A to the second external connection terminal T ₂ , the converter current i _Con flowing from the connection point A to the semiconductor power converter 13, and the mechanical circuit breaker 24 The voltage v _CB appearing at both ends of the voltage and the voltage v _DS appearing at both ends of the mechanical disconnector 26 are shown. 11 and FIG. 13 described later, the load current i _CB flowing from the connection point A to the second external connection terminal T ₂ , the voltage v _CB appearing at both ends of the mechanical circuit breaker 24, and appearing at both ends of the mechanical disconnector 26 The voltage v _DS is shown. Consider a case where a short-circuit accident occurs at the closest end of the circuit breaker 1 at time t ₀ when a resistance load (2 [Ω]) is connected to the circuit breaker 1.

In the semiconductor power converter 13 before time t ₀ when the short circuit accident occurs, the semiconductor power converter 13 itself operates as a diode by the function of each diode D in the semiconductor power converter 13. In this case, the load current i _CB is 150 [A], which is the same as the power supply current i _S, and the converter current i _Con is 0 [A] from Kirchhoff's current law.

When a short circuit accident occurs at time t ₀ , a power conversion command is output for causing the semiconductor power converter 13 to output a direct current that converges the current flowing through the switch 12 to zero. Thereby, the semiconductor switch S in the semiconductor power converter 13 performs a PWM switching operation based on the received power conversion command, and the converter current i _Con increases.

As shown in FIGS. 10 and 11, when the mechanical circuit breaker 24 is opened at time t ₁ , a surge voltage is generated in the mechanical circuit breaker 24, but a snubber circuit connected in parallel to the mechanical circuit breaker 24 is used. 25, the surge voltage can be suppressed to −40 [V]. Since the semiconductor power converter 13 continues the power conversion operation after time t ₂ , the load current i _L flows through the snubber circuit 25. Since the current flowing through the snubber circuit 25 includes the snubber capacitor 51, the direct current component does not flow and only the alternating current component flows. The value of the peak-to-zero of the alternating current is about 1.5 [A]. The load current i _{CB at} time t ₂ is 0 [A], and the mechanical disconnector 26 is opened without generating a surge voltage. The required time “t ₄ −t ₀ ” from the start of the power conversion operation to the current interruption of the semiconductor power converter 13 is 6.8 [ms], and it can be seen that the circuit interruption device 1 can realize high-speed interruption.

FIG. 12 is a diagram showing simulation waveforms of the circuit breaker according to the first embodiment of the present invention. Moreover, FIG. 13 is a figure which shows the enlarged waveform (waveform before and behind a mechanical circuit breaker and a mechanical disconnector open) of FIG. In the simulation, the same circuit parameters as those used in the experiment described with reference to FIGS. 10 and 11 were used. When the experimental results shown in FIGS. 10 and 11 are compared with the simulation results shown in FIGS. 12 and 13, the gradient of the converter current i _Con is continuous in the simulation, but discontinuously changes in the experiment. You can see that The reason is the influence of the non-linear magnetic saturation characteristics of the iron core used for the second inductor 14. More specifically, the inductance value of the second inductor 14 decreases as the converter current i _Con increases. The influence of the non-linearity of the second inductor 14 also appears in the converter voltage v _CB and the load current i _CB . Comparing the experimental result shown in FIG. 11 and the simulation result shown in FIG. 13, the amplitude of the converter voltage v _CB and the load current i _CB is larger in the experiment. The peak value of the surge voltage generated when the mechanical circuit breaker 24 is opened increases as the current value at the time of opening increases. As can be seen from FIG. 13, in the experiment, a surge voltage is generated in the voltage v _DS appearing at both ends of the mechanical disconnector 26 at the time t ₃ when the power conversion operation is finished (all semiconductor switching elements are turned off). . This is due to the internal inductance of the IGBT module of the semiconductor power converter 13 used in the experiment and the wiring inductance accompanying circuit mounting. In the simulation, since these inductances are not taken into consideration, no surge voltage is generated.

  FIG. 21 is a circuit diagram for explaining a circuit breaker according to the second embodiment of the present invention.

  In the circuit breaker 2 according to the second embodiment of the present invention, the energy storage unit 22 includes a first capacitor 55 connected in parallel to the non-linear resistor 23 and an electrostatic capacity greater than the capacitance of the first capacitor 55. A second capacitor 56 having a capacity and a charging voltage lower than the charging voltage of the first capacitor 55 is connected in series to the second capacitor 56 and prevents charging current flowing into the second capacitor 56. Reverse blocking diode 54. A series circuit composed of the second capacitor 56 and the reverse blocking diode 54 is connected in parallel to the first capacitor 55. The first capacitor 55 functions as a snubber capacitor and functions as a second capacitor 56 discharge capacitor.

As described above, the second embodiment is different from the DC capacitor 53 and the reverse blocking diode 54 in the energy storage unit 22 in the first embodiment shown in FIG. The first capacitor 55 is connected in parallel to the blocking diode 54). As a result, the capacitance C ₁ of the first capacitor 55 functioning as a snubber capacitor is inherently reduced by surge voltage regardless of the capacitance C ₂ of the second capacitor 56 functioning as a discharge capacitor. It becomes possible to limit to a function, and it can be made significantly smaller than the energy storage unit 22 in the embodiment shown in FIG. As an example, the second capacitor 56 functioning as a discharging capacitor has a capacitance C _{2 set} to 0.2 [F] and a charging voltage set to 40 [V], and functions as a snubber capacitor. The capacitance C ₁ of the capacitor 55 can be set to 0.1 [μF].

The operation of the circuit breaker 2 according to the second embodiment of the present invention will be described as follows. The first capacitor 55 and the second capacitor 56 in the energy storage unit 22 in the semiconductor power converter 13 are charged in advance by an initial charging circuit (not shown). In the normal circuit breaker 2 before the time t ₀ when the short circuit accident occurs, the mechanical breaker 24 and the mechanical disconnector 26 in the switch 12 are turned on to supply power from the power source side to the load side. . At this time, since each diode D in the semiconductor power converter 13 functions, the semiconductor power converter 13 itself operates as a diode, the converter current i _Con becomes zero, and the power source current i _S and the load current i _CB are It will be the same. At this time, the voltages of the first capacitor 55 and the second capacitor 56 are both values precharged by the initial charging circuit.

Immediately after the overcurrent detection unit 31 detects the occurrence of overcurrent at time t ₀ , the power source current i _S and the load current i _CB are linearly functional with a slope of “V _dc / L ₁ ” as shown in Equation 2. To increase. The overcurrent detection unit 31 determines that “overcurrent has occurred” when the power supply current i _S is only a predetermined value larger than the rated current (for example, a rated current of 120%). Then, the first command means 41 of the control unit 32 outputs a mechanical circuit breaker opening command for instructing the mechanical circuit breaker 24 to start the opening operation. As described above, even if a mechanical circuit breaker opening command is given to the mechanical circuit breaker 24, the mechanical circuit breaker 24 does not immediately complete the opening operation, but actually completes the opening operation with a slight delay. To do.

The second command means 42 of the control unit 32 substantially reduces the current flowing through the mechanical circuit breaker 24 after the mechanical circuit breaker opening command is output until the opening operation of the mechanical circuit breaker 24 is completed. A power conversion command for causing the semiconductor power converter 13 to output a direct current that converges to zero is output. The semiconductor switching element S of the semiconductor switch in the DCDC converter 21 in the semiconductor power converter 13 performs a PWM switching operation based on the received power conversion command. As a result, the energy stored in the second capacitor 56 in the energy storage unit 22 is converted by the DCDC converter 21 and the current flowing from the semiconductor power converter 13 to the mechanical circuit breaker 24 is converged to substantially zero. Current is output. After the opening operation of the mechanical circuit breaker 24 is completed (that is, after a predetermined period of time has elapsed since the first command means 41 outputs a mechanical circuit breaker opening command), a third command in the control unit 32 is provided. The means 43 outputs a mechanical disconnector opening command for instructing the mechanical disconnector 26 to start the opening operation. As a result, the mechanical disconnector 26 starts the opening operation in response to the mechanical disconnector opening command from the third command means 43. When the opening operation of the mechanical disconnector 26 is completed, the fourth command means 44 in the control unit 32 outputs a command to turn off all the semiconductor switches S in the semiconductor power converter 13. The semiconductor device S in the semiconductor power converter 13 is turned off by receiving the off command from the fourth command means 44 in the control unit 32, and the power conversion operation is completed. Thereby, only each diode D in the semiconductor power converter 13 functions. At this time, the stored energy of the first inductor 11 and the second inductor 14 is released to the first capacitor 55 via the feedback diode D, and the voltage of the first capacitor 55 gradually increases. When the voltage of the first capacitor 55 becomes larger than the voltage of the second capacitor 56, the reverse blocking diode 54 prevents the charging current from flowing into the second capacitor 56, so that the second capacitor 56 is connected to the DCDC converter 21. Can be electrically disconnected from the second DC side. Since the capacitance C ₁ of the first capacitor 55 is smaller than the capacitance C ₂ of the second capacitor 56, the voltage of the first capacitor 55 rises rapidly. When the voltage of the first capacitor 55 rises and reaches the operating voltage V _Clamp of the nonlinear resistor 23, the stored energy of the first inductor 11 and the second inductor 14 is consumed by the nonlinear resistor 23. As described above, since the voltage of the first capacitor 55 rises rapidly, the time to reach the operating voltage V _Clamp of the non-linear resistor 23 can be greatly shortened compared to the case of the first embodiment of FIG. As a result, it is possible to greatly shorten the shut-off time. Since the circuit configuration and operation other than those described above are the same as those in the first embodiment shown in FIG.

DESCRIPTION OF SYMBOLS 1, 2 Circuit breaker 11 1st inductor 12 Switch 13 Semiconductor power converter 14 2nd inductor T1 _1st external connection terminal T2 _2nd external connection terminal 21 DCDC converter 22 Energy storage part 23 Nonlinear resistance 24 mechanical circuit breaker 25 snubber circuit 26 mechanical disconnector 31 overcurrent detection unit 32 control unit 41 first command unit 42 second command unit 43 third command unit 44 fourth command unit 51 snubber capacitor 52 Snubber resistor 53 DC capacitor 54 Reverse blocking diode 55 First capacitor 56 Second capacitor

Claims (9)

A first inductor having a first external connection terminal;
A switch connected in series to the first inductor and having a second external connection terminal on the side opposite to the side to which the first inductor is connected, and is opened according to a command. A mechanical circuit breaker that interrupts a current path; a snubber circuit connected in parallel to the mechanical circuit breaker; and a parallel circuit composed of the mechanical circuit breaker and the snubber circuit; A switch composed of a mechanical disconnector that opens a pole in response to a command and interrupts the current path;
One or a plurality of semiconductor power converters cascade-connected to each other provided on a wiring branched from a wiring connecting the first inductor and the switch, the semiconductor switch provided inside A semiconductor power converter that outputs a predetermined direct current by performing a switching operation according to a command;
A second inductor connected in series with the semiconductor power converter;
With
A circuit breaker characterized in that a unit in which the semiconductor power converter and the second inductor are located on the same wiring is connected in parallel to the switch. The semiconductor power converter is
Due to the switching operation of the semiconductor switch, the first DC side to which the second inductor or another semiconductor power converter different from the semiconductor power converter is connected is opposite to the first DC side. A DCDC converter for converting a direct current input from one of the second direct current sides into a direct current of a desired magnitude and polarity and outputting the direct current to the other, wherein the input / output direction of the direct current is the first DC input / output direction. A DC / DC converter switchable in both directions between the direct current side and the second direct current side;
An energy storage unit connected in parallel to the second DC side of the DCDC converter;
The DC voltage connected in parallel to the energy storage unit and applied to the energy storage unit indicates a predetermined resistance value when the voltage is equal to or lower than a preset voltage, and in other cases than the predetermined resistance value A non-linear resistance exhibiting a low resistance value;
The circuit breaker according to claim 1, comprising:   The circuit breaker according to claim 1, wherein the energy storage unit includes a capacitor and a reverse blocking diode that is connected in series with the capacitor and blocks a charging current flowing into the capacitor. The energy storage unit
A first capacitor connected in parallel to the nonlinear resistor;
A second capacitor having a capacitance greater than the capacitance of the first capacitor and a charge voltage lower than the charge voltage of the first capacitor;
A reverse blocking diode connected in series with the second capacitor and blocking a charging current flowing into the second capacitor;
Have
The circuit breaker according to claim 1 or 2, wherein a series circuit composed of the second capacitor and the reverse blocking diode is connected in parallel to the first capacitor.   5. The second inductor according to claim 1, wherein the second inductor is connected in series to any one of the plurality of semiconductor power converters cascade-connected to each other. 6. Circuit breaker. An overcurrent detector that detects whether or not an overcurrent has occurred on the external wiring connected to the first external connection terminal or the second external connection terminal;
A control unit for controlling an opening operation for the mechanical circuit breaker and the mechanical disconnector and a power conversion operation of the semiconductor power converter;
With
The controller is
A first command means for outputting a mechanical circuit breaker opening command for instructing the mechanical circuit breaker to start a opening operation after detecting an overcurrent by the overcurrent detection unit;
After the overcurrent is detected by the overcurrent detection unit, the current flowing through the mechanical circuit breaker is substantially zero until the opening operation of the mechanical circuit breaker is completed based on the opening command for the mechanical circuit breaker. Second command means for outputting a power conversion command for causing the semiconductor power converter to output a DC current to be converged;
Third command means for outputting a mechanical disconnector opening command for instructing the mechanical disconnector to start the opening operation after a predetermined period has elapsed since the mechanical breaker opening command is output. When,
Fourth command means for outputting an off command to turn off the semiconductor switch in the semiconductor power converter when the opening operation of the mechanical circuit breaker is completed;
The circuit breaker according to claim 1, comprising:   The circuit breaker according to any one of claims 1 to 6, wherein the snubber circuit includes a series circuit of a snubber capacitor and a snubber resistor. The semiconductor switch is
A semiconductor switching element that allows current to flow in one direction when on,
A return diode connected in antiparallel to the semiconductor switching element;
The circuit breaker according to claim 1, comprising: The mechanical circuit breaker is
A stationary contact;
A movable contact that is movable between a closed position that contacts the fixed contact and an open position that is separated from the fixed contact;
The circuit breaker according to claim 1, comprising:

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