JP6706834B2 - Circuit breaker - Google Patents

Description

The present invention relates to a circuit breaker that breaks 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 combines a mechanical switch method and a semiconductor switch method.

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

When a ground fault or short circuit occurs in the DC power supply system, overcurrent occurs. The rate of increase in current ([A/s]) from the occurrence of an accident is inversely proportional to the DC inductance of the DC power supply system. For example, when a DC voltage is generated by using a voltage source converter, since the DC inductance is small and an overcurrent may occur, 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 type, semiconductor switch type, and hybrid type.

Of these, the mechanical switch system is one that interrupts the current using a mechanical breaker (circuit breaker: Circuit Breaker) such as a vacuum breaker, a gas breaker, or an air blower breaker, and an LC resonance circuit. (See, for example, Non-Patent Document 1). The mechanical switch method does not use power devices, so steady loss does not occur.

Further, in the semiconductor switching method, a high-speed breaking time (1 [ms] or less) is realized by configuring a circuit breaker using a power device (power semiconductor element) (for example, see Non-Patent Document 2). ..

In addition, the hybrid system is characterized in that it uses both a mechanical breaker capable of high-speed operation and a power device in combination to achieve both high-speed current interruption and loss reduction, and various circuits have been proposed (for example, See Non-Patent Document 3.). FIG. 15 is a circuit diagram illustrating a general hybrid circuit breaker. For example, as shown in FIG. 15, a hybrid type circuit breaker 100 includes a current limiting inductor 151, a mechanical breaker (circuit breaker) 152, a commutation auxiliary semiconductor switch 153, a main semiconductor switch 154, and an arrester (circuit breaker). The non-linear resistance) 155 constitutes the main circuit. Power is supplied to the load through the current limiting inductor 151, the mechanical circuit breaker 152, and the commutation auxiliary semiconductor switch 153 during normal operation, and the commutation auxiliary semiconductor switch 153 is turned off during an accident such as a ground fault or short circuit. Commutated 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 the 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 the breaking time is 2 [ms] or less by using the mechanical breaker 152 capable of opening the contact within 1 [ms]. You can

B. Bachmann, G. Mauthe, E. Ruoss, H.P. Lips, "500 kV wind-cooled high-voltage DC power supply" Circuit breaker (Deployment of a 500 kV Airblast HVDC Circuit Breaker), (United States), Institute of Electrical and Electronics Engineers (IEEE Transactions), electrical equipment and systems (Power Apparatus and No. Systems, 104, Systems. 9, pp. 2460-2466, September 1985 C. Meyer, S. Schroder, RW De Doncker, "Solid State Circuit Breaker for Medium Voltage Systems with Distributed Power Systems" Devices and Current Limiters (Solid-State Circuit Breakers and Current Limiters For Medium-Voltage Systems Having Hauling Distributed Power Systems, United States), E-Electrical Electronic Transactions (I-E). 19, No. 5, pp. 1333-1340, September 2004 M. Steuer, K. Frorich, W. Holaus, K. Kaltenegger, "New Hybrid Current Limiting Circuit Breaker for Medium Voltage: Principle And test results (A Novel Hybrid Current-Limiting Circuit Breaker for Medium Voltage: Principle and Test Results", (United States), Institute of Electrical and Electronics Engineers, No. 2 (IEEE)Transaction, Power Delivery (Die. pp.460-467, April 2003

The circuit breaker using the mechanical switch method has the advantage that steady loss does not occur because it does not use a power device, but since the time required to break the current (opening time) is as long as 30 to 100 [ms], the DC inductance is Although it can be applied to a large current source converter, it is difficult to apply it to a voltage source converter.

In addition, the circuit breaker using the semiconductor switch method has a problem that a steady loss occurs because a current constantly flows through the internal semiconductor switch. Further, since a high voltage equal to or higher than the DC voltage is applied to the internal semiconductor switch when the current is cut off, 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, when the direct current is 320 [kV], the on-voltage of the semiconductor switch is 100 [V] or more. Since a current constantly flows through the semiconductor switch, reducing the loss due to the on-voltage is an issue.

Further, the hybrid circuit breaker described above can reduce the steady loss as compared with the semiconductor switch system because the required withstand voltage of the commutation auxiliary semiconductor switch is about several% of the main semiconductor switch, and it is also different from the mechanical switch system. Even if compared, there is an advantage that the interruption time can be shortened. However, since a steady-state current still flows through the commutation auxiliary semiconductor switch during normal operation, the steady-state loss cannot be zero.

Further, with the expansion of the application range of the high-voltage DC power supply system in the future, it is desired to develop a low-cost DC interruption system capable of interrupting the 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, which has a steady loss of zero in a normal state and can interrupt a current path at high speed when an accident occurs. Especially.

In order to achieve the above object, in the present invention, a circuit breaker is connected in series with a first inductor having a first external connection terminal, and the first inductor is connected. A switch having a second external connection terminal on the side opposite to the side that is opened, the mechanical breaker opening in response to a command to cut off the current path, and the mechanical breaker in parallel. A switch composed of a snubber circuit to be connected and a mechanical circuit breaker which is connected in series to a parallel circuit composed of a mechanical circuit breaker and a snubber circuit and which opens a circuit in accordance with a command to cut off a current path. , A semiconductor power converter provided on a wiring branched from a wiring connecting the first inductor and the switch, or a plurality of semiconductor power converters cascade-connected to each other. And a second inductor connected in series to the semiconductor power converter, the semiconductor power converter outputting a predetermined direct current by performing a switching operation in accordance with the semiconductor power converter and the second power converter. Units whose inductors are located on the same wiring are connected in parallel to the switch.

Here, the semiconductor power converter includes 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 side. A DC/DC converter that converts a DC current input from one of a second DC side on the side opposite to the side to a DC current of a desired magnitude and polarity and outputs the DC current to the other side. A DCDC converter capable of bidirectionally switching the output direction between a first DC side and a second DC side, an energy storage section connected in parallel to the second DC side of the DCDC converter, and an energy storage section Connected in parallel with the DC voltage applied to the energy storage unit is less than or equal to a preset voltage, and exhibits a predetermined resistance value; otherwise, a non-linearity that exhibits a resistance value lower than the predetermined resistance value. And a resistor.

Further, the energy storage unit may include 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 has a first capacitor connected in parallel with the non-linear resistance, an electrostatic capacitance larger than the electrostatic 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 that is connected in series to the second capacitor and blocks a charging current flowing into the second capacitor, and includes a second capacitor and a reverse blocking diode. The series circuit may be connected in parallel to the first capacitor.

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

In addition, 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, and A control unit for controlling the opening operation of the mechanical disconnector and the power conversion operation of the semiconductor power converter, and the control unit opens the mechanical breaker after the overcurrent is detected by the overcurrent detection unit. First command means for outputting a mechanical circuit breaker opening command for commanding the start of the pole operation, and opening of the mechanical circuit breaker based on the mechanical circuit breaker opening command after the overcurrent is detected by the overcurrent detection unit. Second command means for outputting a power conversion command for causing the semiconductor power converter to output a DC current that converges the current flowing through the mechanical breaker to substantially zero until the pole operation is completed, and for mechanical breaker Third command means for outputting a mechanical disconnector opening command for instructing the mechanical disconnector to start an opening operation after a predetermined period has elapsed since the opening command was output, and a mechanical circuit breaker. And a fourth command means for outputting an off command for turning off the semiconductor switch in the semiconductor power converter when the contact opening operation is completed.

Further, the above snubber circuit may be composed of a series circuit of a snubber capacitor and a snubber resistor.

Further, the semiconductor switch may include a semiconductor switching element that passes a current in one direction when turned on, and a return diode that is connected in antiparallel to the semiconductor switching element.

Further, the mechanical breaker may have a fixed contact and a movable contact movable between a closed position in contact with the fixed contact and an open position separated from the fixed contact. ..

According to the present invention, it is possible to realize a low-cost circuit breaker capable of interrupting a DC high voltage, which has a steady loss of zero in a normal state and can interrupt a current path at 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 circuit breaker, and a semiconductor power converter, but in a normal state, the mechanical circuit breaker and the mechanical circuit breaker are turned on and the power source side is turned on. Since the power is supplied to the load side from the semiconductor power converter and the semiconductor power converter only operates as a diode, it is possible to reduce the steady loss of the circuit breaker in a normal state to zero.

Further, according to the present invention, when an overcurrent occurs due to a ground fault accident or a short circuit accident, the current path can be quickly switched by appropriately controlling the operations of the mechanical breaker, the mechanical disconnector, and the semiconductor power converter. Can be shut off.

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

Further, according to the present invention, the breakdown voltage of the circuit breaker can be increased by appropriately adjusting the number of semiconductor power converters connected in cascade.

Further, according to the present invention, by configuring the DCDC converter in the semiconductor power converter as a four-quadrant DCDC converter, the current path can be cut off regardless of the amplitude and polarity of the DC current.

1 is a circuit diagram showing a circuit breaker according to a first exemplary embodiment of the present invention. It is a circuit diagram explaining the semiconductor power converter in the circuit breaker by the 1st Example of this invention. It is a circuit diagram (the 1) explaining the example of arrangement of the 2nd inductor in the circuit breaker by the 1st example of the present invention. It is a circuit diagram (the 2) explaining the example of arrangement of the 2nd inductor in the circuit breaker by the 1st example of the present invention. It is a circuit diagram (the 3) explaining the example of arrangement of the 2nd inductor in the circuit interrupting device by the 1st example 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 electric power conversion command for controlling the converter electric current in the semiconductor power converter in the circuit breaker by the 1st Example of this 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 expanded waveform (waveform before and behind opening of a mechanical 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 expanded waveform (waveform before and behind opening of a mechanical breaker and a mechanical disconnector) of FIG. It is a circuit diagram explaining the circuit breaker by the 2nd Example of this invention. It is a circuit diagram which illustrates a general hybrid type circuit breaker.

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 opens the pole in response to a command and breaks the current path, 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. It has two external connection terminals. The semiconductor power converter outputs a predetermined DC current by performing a switching operation of a semiconductor switch provided inside according to a command, and branches from a wiring connecting the first inductor and the mechanical breaker. These wirings are provided individually or in a state where a plurality of them are connected in cascade. The second inductor is connected in series with the semiconductor power converter or the mechanical breaker. One of the first inductor and the second inductor is the fault current limiting inductor, and the other is the current controlling inductor. Hereinafter, specific circuit configurations will be described in the first to third embodiments.

1 is a circuit diagram showing 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 a first embodiment of the present invention. is there. Hereinafter, components having the same reference numeral in different drawings mean that the components have the same function.

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 DC power supply system to which it is applied. In this embodiment, a 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 such 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. A circuit on the load side is connected to the second external connection terminal T ₂ . The switch 12 includes a mechanical breaker (Circuit Breaker) 24, a snubber circuit 25, and a mechanical disconnector (Disconnecting Switch) 26.

The mechanical breaker 24 opens in accordance with the mechanical breaker command to break the current path. The mechanical breaker 24 has a fixed contact and a movable contact that can move between a closed position in contact with the fixed contact and an open position separated from the fixed contact, and is movable according to a command. The contactor separates from the fixed contact and opens the contact, interrupting the current path. Examples of the mechanical circuit breaker 24 include a vacuum circuit breaker, a gas circuit breaker or an air blow circuit breaker.

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

The mechanical disconnector 26 is opened in response to a mechanical disconnector command to interrupt the current path. Unlike the mechanical circuit breaker 24, the mechanical disconnector 26 does not have an arc extinguishing ability, does not open and close when a current is flowing in 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.

As described above, in the present invention, the mechanical circuit breaker 24 and the mechanical circuit breaker 26 are used in combination as the current circuit breaking means in the switch 12. With such a configuration, the voltage applied to the switch 12 as a whole is divided into the voltage applied to the mechanical breaker 24 and the voltage applied to the mechanical disconnector 26. .. When the mechanical breaker 24 and the mechanical disconnector 26 are both open, the voltage applied between the mechanical contacts of the mechanical breaker 24 to which the snubber circuit 25 is connected in parallel is equal to the mechanical breaker 26. Is less than the voltage applied across the mechanical contacts of. Also, the price of the mechanical disconnector 26 is generally much lower than the price of the mechanical breaker 24. Therefore, the circuit breaker 1 according to the present invention in which most of the voltage applied to the switch 12 at the time of circuit breakage is applied to the mechanical breaker 26 that is inexpensive, when the DC voltage is extremely high (for example, 250[ kV]) can also be supported.

The semiconductor power converter 13 is provided alone or in a state where a plurality of semiconductor power converters 13 are cascade-connected to each other on a wiring branched from a wiring connecting the first inductor 11 and the switch 12. 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 “first DC side”, and a plurality of semiconductor power converters 13 are cascaded with each other. When connected, 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”. Further, the DC side opposite to the "first DC side" is referred to as "second DC side". As an example, FIG. 1 shows a case where a plurality of (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. The high breakdown voltage of the circuit breaker 1 can be easily realized simply by appropriately adjusting the number of the semiconductor power converters 13 connected in cascade.

The semiconductor power converter 13 includes a DCDC converter 21, an energy storage unit 22, and a non-linear resistance 23, and a semiconductor switch provided inside the DCDC converter 21 performs a switching operation in response to a command to perform a predetermined operation. Outputs DC 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 DC current input from one of the first DC side and the second DC side into a DC current having a desired magnitude and polarity by the switching operation of the semiconductor switch S. The output is 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 cut off regardless of the amplitude and polarity of the DC current. The semiconductor switch includes a semiconductor switching element S that passes a current in one direction when turned on, and a return 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), and a transistor, 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 this embodiment, the energy storage unit 22 includes a series circuit of 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. An initial charging circuit needs to be additionally provided to initially charge the DC capacitor 53, but is not shown here.

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

Since the DC capacitor 22 and the non-linear resistance 23 are connected in parallel, when the DC capacitor 22 is charged by the energy stored in the first inductor 11 and the second inductor 14, the DC capacitor 22 is charged. When the voltage gradually rises and reaches the operating voltage of the non-linear resistance 23, the charging voltage of the DC capacitor 22 is thereafter clamped by the operating voltage of the non-linear resistance 23 and accumulated in the first inductor 11 and the second inductor 14. The generated energy is consumed by the non-linear resistance 23. The energy storage unit 22 and the non-linear resistance 23 may be realized by other elements as long as they perform a series of operations of charging the DC capacitor 22 and consuming the non-linear resistance 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 to any one of the plurality of semiconductor power converters 13 cascade-connected to each other in series. Connected. 3 to 5 are circuit diagrams illustrating 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 FIGS. 3 and 4, the second inductor 14 is the semiconductor power converter 13 of any one of the semiconductor power converters 13 located at both ends of the cascade connection. Is installed on the side not connected. 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 the number of semiconductor power converters 13 is one, the second inductor 14 is simply connected to the semiconductor power converter 13 in series.

Regardless of whether a plurality of semiconductor power converters 13 are cascade-connected or one semiconductor power converter 13, the semiconductor power converter 13 and the second inductor 14 are on the same wiring. The located units are 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.

Although the circuit breaker 1 operates as a DC breaker in this embodiment, the circuit breaker 2 can operate as an AC breaker as well as a DC breaker. In this case, , G ₁ and G ₂ are terminals having polarities opposite to the polarities of the first external connecting terminal T ₁ and the second external connecting 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 above-mentioned "second DC side", and the AC side corresponds to the above-mentioned "first DC side".

In the example shown in FIG. 1, the side formed by the first external connection terminal T ₁ and the ground terminal G ₁ is the power supply side, and the side formed by the second external connection terminal T ₂ and the ground terminal G ₂ is the load side. Therefore, the first inductor 11 functions as a fault current limiting inductor, and the second inductor 14 functions as a current controlling inductor.

Thereafter, the DC voltage on the power source side 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 , the semiconductor power converter 13 The total voltage of the semiconductor power converters 13 on the side connected in cascade is represented by v _HB . Further, 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). The voltage appearing across the nonlinear resistor 23 is represented by v _MOV . Also, 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 is The current flowing to the semiconductor power converter 13 is referred to as converter current i _Con . Regarding the voltage and current in the figure, the direction of each 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 detector 31 and a controller 32 as its control system.

The overcurrent detection unit 31 detects whether an overcurrent has occurred on the load-side external wiring connected to the second external connection terminal T ₂ . In the present embodiment, the side composed of the second external connection terminal T ₂ and the ground terminal G ₂ is set as the load side. Therefore, the overcurrent detection unit 31 includes the load side connected to the _second external connection terminal T ₂ . Although the presence or absence of overcurrent on the external wiring is detected, if the side composed of the first external connection terminal T ₁ and the ground terminal G ₁ is the load side, the overcurrent detection unit 31 detects The presence or absence of overcurrent on the load-side external wiring connected to the external connection terminal T ₁ of _{No. 1} may be detected. The detection of overcurrent generation by the overcurrent detection unit 31 may be realized by a known method. For example, when 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 higher than the rated current. When the value becomes larger than, it is determined that "overcurrent has occurred". The reference current value used to determine the occurrence of overcurrent may be appropriately set as necessary, for example, set to a rated current of 120%.

The controller 32 controls the opening operation of the mechanical breaker 24 and the mechanical disconnector 26 in the switch 12, and the power conversion operation of the semiconductor power converter 13. That is, the control unit 32 outputs the mechanical circuit breaker opening command for instructing the mechanical circuit breaker 24 to start the opening operation after the overcurrent detection unit 31 detects the overcurrent. 41 and the current flowing through the mechanical breaker 24 after the overcurrent is detected by the overcurrent detector 31 until the opening operation of the mechanical breaker 24 is completed based on the mechanical breaker opening command. Second command means 42 that outputs a power conversion command that causes the DC power to be converged to zero to be output to the semiconductor power converter 13, and a predetermined period after the mechanical circuit breaker opening command is output. When the opening operation of the mechanical circuit breaker 24 and the third command means 43 for outputting the opening command of the mechanical disconnector for instructing the disconnector 26 to start the opening operation, the semiconductor power converter is completed. And a fourth command means 44 for outputting a command to turn off the semiconductor switch S in 13.

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, for example, a software program format, or a combination of various electronic circuits and software programs. May be built with. For example, when these means are constructed in the software program format, the arithmetic processing unit in the control unit 32 operates according to this software program to realize the functions of the respective means described above.

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

The circuit breaker 1 operates normally when no overcurrent is generated on the load side (step S101). That is, in a normal state, the mechanical breaker 24 and the mechanical disconnector 26 in the switch 12 are turned on and power is supplied from the power supply side to the load side. At this time, each diode D in the semiconductor power converter 13 functions so that 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 under normal conditions is zero. It is assumed 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 to each other, that is, “i _CB =i _S ”. Further, the voltage drop in the first inductor L ₁ is zero in a normal state, so that 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 detects whether an overcurrent has occurred on the load-side external wiring connected to the second external connection terminal T ₂ . When the overcurrent detection unit 31 does not detect the overcurrent, the process returns to step S101 to continue the normal operation. When the overcurrent detection unit 31 detects the overcurrent, the process proceeds to step S103.

For example, assume that the overcurrent detection unit 31 detects the occurrence of overcurrent at time t ₁ . At this time, in the circuit breaker 1, if the voltage drop in the switch 12 is ignored, the circuit equation shown in Expression 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 linearly increase with the 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 an accident can be suppressed. Since the power supply current i _S increases when a short circuit or a 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. If increased by a predetermined value than the current (e.g., rated current 120%) determined in the "overcurrent" (time t _1). The time required from the accident in the accident determination "t ₁ -t _0" the power supply-side DC voltage V _dc, the inductance L ₁ of the first inductor, the load, which depends on the reference current value.

When the overcurrent detection unit 31 detects the overcurrent in step S102, the second command means 42 of the control unit 32 performs the opening operation of the mechanical breaker 24 after the opening command is output in step S103. By the time it is completed, it outputs a power conversion command that causes the semiconductor power converter 13 to output a DC current that causes the current flowing through the mechanical breaker 24 to converge to substantially zero.

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

The process in step S103 and the process in step S104 may be executed simultaneously, or the order of the processes in step S103 and step S104 may be exchanged.

When the mechanical circuit breaker 24 opening command for mechanical circuit breaker is given to the mechanical circuit breaker 24 in step S104, the mechanical circuit breaker 24 starts the electrode opening operation (step S105). However, the mechanical circuit breaker 24 does not immediately complete the electrode opening operation. A delay time occurs due to the mechanical structure of the mechanical circuit breaker 24, and in actuality, the mechanical circuit breaker 24 performs an opening operation a little after 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 10 [kV] class, and about 2 [ms] when the DC voltage is several 100 [kV] class. As described above, the mechanical breaker 24 can break the current path when the current has a very small value (for example, several [mA] to several tens [mA]). The flowing load current i _CB needs to be zero as much as possible. Therefore, in step S103, the second command means 42 of the control unit 32 causes the current flowing through the mechanical circuit breaker 24 from the output of the opening command until the completion of the opening operation of the mechanical circuit breaker 24. Is output to the semiconductor power converter 13 as a power conversion command that causes the DC power to converge to approximately zero. The semiconductor switching element S of the semiconductor switch in the DCDC converter 21 in the semiconductor power converter 13 performs PWM switching operation based on the received power conversion command. This is equivalent to the semiconductor power converter 13 operating as a control voltage source that outputs the voltage v _HB . At this time, a circuit equation such as Equation 3 holds.

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 Equation 4, K _p represents a proportional gain, K _I represents an integral gain, and i ^* _Con represents a command value of the converter current. Although PI control is applied in this embodiment, current control other than PI control may be applied.

In Expression 4, the right side corresponds to the 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. In this case, by performing control to the converter current command value i ^* _Con a i _S set by the converter current i _Con to match the source current i _S, the load current i _CB can be made zero. The time required to reduce the load current i _CB to zero (that is, the time required to match the converter current i _Con with the power supply current i _S ) is the carrier frequency of the semiconductor power converter 13, the equivalent switching frequency, and the digital control. It depends on the method. For example, if a high-voltage SiC MOSFET that can realize low loss and high switching frequency operation is used, it is sufficiently possible to realize the time required to reduce the load current i _CB to 1 [ms] or less.

Based on the above, the principle of generating the power conversion command based on Equation 4 will be described as follows. FIG. 8 is a control block diagram illustrating 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. Feedback control is used to control the converter current. In the block B1 relating to feedback control, PI control is applied to the difference between the converter current i _Con detected by a current detector (not shown) and the power supply current i _S detected by a current detector (not shown). By doing so, the deviation “i _Con −i _S ”is suppressed. 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 to each semiconductor power converter 13 is standardized by the DC capacitor voltage v _Cj (where j=1 to N) in block B4 _j , and then the general PWM modulation method (triangular wave comparison). Is applied to the semiconductor switch S in each semiconductor power converter 13. The equivalent switching frequency can be increased 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. Specifically, when 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 the current control inductor.

Generally, the switching frequency of a semiconductor power converter for high voltage applications is set to several hundred [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, the increase in switching loss does not pose a problem. For example, when a 3.3 [kV]/1500 [A] SiC power module (SiC MOSFET and SiC SBD (Schottky Barrier Diode)) is used as the semiconductor power converter 13, a carrier frequency of several [kHz] is used for PWM modulation. Application is expected, and improvement in current controllability can be expected. If the same carrier frequency is assumed, the current controllability is improved in high voltage applications where the number of cascades of the semiconductor power converter 13 increases.

Returning to FIG. 5, in step S105, the mechanical 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 breaker 24 can break the current path when the current has a very small value (for example, several [mA] to several tens [mA]). However, the mechanical breaker in step S103. The process of making the current flowing through 24 substantially zero is executed in a time sufficiently shorter than the time required from the output of the mechanical circuit breaker opening command to the completion of the mechanical circuit breaker 24 opening operation.

After completion of the opening operation of the mechanical circuit breaker 24 (that is, after a lapse of a predetermined period from the output of the mechanical circuit breaker opening command by the first command means 41), a third command in the control unit 32 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 mechanical circuit breaker 24 to complete the opening operation after receiving the mechanical circuit breaker opening command can be known from experiments and specifications of the mechanical circuit breaker 24. The timing for outputting the mechanical disconnecting switch opening command by the commanding means 43 of No. 3 is, after considering the time, after a predetermined period has elapsed since the mechanical circuit breaker opening command was output by the first commanding means 41. Just set it.

In step S107, 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 controller 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 controller 32, all the semiconductor switches S in the semiconductor power converter 13 are turned off, and the power conversion operation ends. As a result, 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 return diode D. Since the DC capacitor 22 and the non-linear resistance 23 are connected in parallel, after the semiconductor switch S is turned off (that is, the period after time t ₃ ), the direct current is generated by the stored energy of the first inductor 11 and the second inductor 14. The capacitor 22 is charged, the voltage v _c gradually rises, and then is clamped by the operating voltage V _Clamp of the non-linear resistor 23. After the DC capacitor 22 is charged to the operating voltage, the stored energy is consumed by the non-linear resistance 23.

The circuit equation shown in Expression 6 is established until the DC capacitor 22 is charged to the operating voltage of the non-linear resistance 23 by the stored energy.

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

After the DC capacitor 22 is charged to the operating voltage, the circuit equation shown in Expression 7 holds. In Expression 7, the operating voltage of the non-linear 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 the linear differential coefficient first-order coefficient 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 illustrating circuit parameters used in the simulation and the experiment. "PSCAD/EMTDC" was used for the simulation. The rated DC power supply voltage V _dc was 300 [V], the rated power supply current I _S was 150 [A], and the load R was 2 [Ω]. The inductance L ₁ of the first inductor (current limiting inductor during an accident) was set to 6 [mH] so that the current increase rate V _dc /L ₁ was 50 [A/ms]. The number N of semiconductor power converters 13 is three. Phase shift PWM is applied to the triangular wave carrier of the semiconductor power converter 13. An IGBT is used as a 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 Equation 8. In Expression 8, P is a rated capacity (unit is [W]).

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

FIG. 10 is a diagram showing experimental waveforms of the circuit breaker according to the first embodiment of the present invention. Further, FIG. 11 is a diagram showing an enlarged waveform of FIG. 10 (waveforms before and after opening of the mechanical breaker and the mechanical disconnector). 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 breaker 24. The voltage v _CB appearing across the switch and the voltage v _DS appearing across 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 breaker 24, and the both ends of the mechanical disconnector 26 appearing. 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 resistive load (2 [Ω]) is connected to the circuit breaker 1.

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

When a short-circuit accident occurs at time t ₀ , a power conversion command that causes the semiconductor power converter 13 to output a DC current that causes the current flowing through the switch 12 to converge to zero is output. Thereby, the semiconductor switch S in the semiconductor power converter 13 performs the 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 opens 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. 25, the surge voltage can be suppressed to -40 [V]. Since the semiconductor power converter 13 continues the power conversion operation even after the time t ₂ , the load current i _L flows through the snubber circuit 25. Since there is the snubber capacitor 51, the current flowing through the snubber circuit 25 does not flow a DC component but only an AC component. 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 open without generating a surge voltage. The required time “t ₄ −t ₀ ”from the start of the power conversion operation of the semiconductor power converter 13 to the interruption of the current is 6.8 [ms], which shows that the circuit interruption device 1 can realize the high-speed interruption.

FIG. 12 is a diagram showing a simulation waveform of the circuit breaker according to the first embodiment of the present invention. Further, FIG. 13 is a diagram showing an enlarged waveform of FIG. 12 (waveforms before and after opening of the mechanical breaker and the mechanical disconnector). In the simulation, the same circuit parameters as those used in the experiment described with reference to FIGS. 10 and 11 were used. Comparing the experimental results shown in FIGS. 10 and 11 with the simulation results shown in FIGS. 12 and 13, the converter current i _Con has a continuous slope in the simulation, but changes discontinuously in the experiment. You can see that The reason for this is the influence of the nonlinear magnetic saturation characteristic of the iron core used for the second inductor 14. More specifically, as the converter current i _Con increases, the inductance value of the second inductor 14 decreases. 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 results shown in FIG. 11 with the simulation results shown in FIG. 13, the amplitudes of the converter voltage v _CB and the load current i _CB are larger in the experiment. The peak value of the surge voltage generated when the mechanical breaker 24 is opened becomes larger as the current value at the opening becomes larger. As can be seen from FIG. 13, in the experiment, a surge voltage is generated in the voltage v _DS appearing across the mechanical disconnector 26 at time t ₃ when the power conversion operation is completed (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 the circuit mounting. In the simulation, the surge voltage does not occur because these inductances are not taken into consideration.

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

In the circuit breaker 2 according to the second exemplary embodiment of the present invention, the energy storage unit 22 includes a first capacitor 55 connected in parallel with the non-linear resistance 23 and an electrostatic capacitance larger than the electrostatic 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 and a second capacitor 56 connected in series to block a charging current flowing into the second capacitor 56. And a reverse blocking diode 54. A series circuit including 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 the second capacitor 56 functions as a discharging 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. 1 (the second capacitor 56 and the reverse blocking diode in FIG. 14). The first capacitor 55 is connected in parallel to the blocking diode 54). As a result, the electrostatic capacitance C ₁ of the first capacitor 55 that functions as a snubber capacitor is essentially the same as that of suppressing surge voltage, regardless of the electrostatic capacitance C ₂ of the second capacitor 56 that functions as a discharging capacitor. It becomes possible to limit the functions, and it is possible to make the size much smaller than the energy storage unit 22 in the embodiment shown in FIG. To give an example, the capacitance C ₂ of the second capacitor 56 that functions as a discharging capacitor is set to 0.2 [F], the charging voltage is set to 40 [V], and the first capacitor that functions as a snubber capacitor is set. 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 below. 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 time t ₀ when a short-circuit accident occurs, the mechanical breaker 24 and the mechanical disconnector 26 in the switch 12 are turned on and power is supplied from the power supply side to the load side. .. At this time, each diode D in the semiconductor power converter 13 functions so that the semiconductor power converter 13 itself operates as a diode, the converter current i _Con becomes zero, and the power supply current i _S and the load current i _{CB become} Will be the same. At this time, the voltages of the first capacitor 55 and the second capacitor 56 both have values pre-charged by the initial charging circuit.

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

The second command means 42 of the control unit 32 substantially eliminates the current flowing through the mechanical breaker 24 after the mechanical circuit breaker opening command is output until the opening operation of the mechanical breaker 24 is completed. A power conversion command that causes the semiconductor power converter 13 to output a DC 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 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 breaker 24 is converged to substantially zero DC. Current is output. After completion of the opening operation of the mechanical circuit breaker 24 (that is, after a lapse of a predetermined period from the output of the mechanical circuit breaker opening command by the first command means 41), a third command in the control unit 32 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 contact 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 controller 32 outputs a command to turn off all the semiconductor switches S in the semiconductor power converter 13. Upon receiving the OFF command from the fourth command means 44 in the control unit 32, all the semiconductor switches S in the semiconductor power converter 13 are turned off, and the power conversion operation is completed. Thereby, only each diode D in the semiconductor power converter 13 will function. At this time, the energy stored in the first inductor 11 and the second inductor 14 is released to the first capacitor 55 via the return diode D, and the voltage of the first capacitor 55 gradually rises. When the voltage of the first capacitor 55 becomes higher than the voltage of the second capacitor 56, the reverse blocking diode 54 blocks 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 of the. Since the electrostatic capacitance C ₁ of the first capacitor 55 is smaller than the electrostatic 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 non-linear resistance 23, the energy stored in the first inductor 11 and the second inductor 14 is consumed in the non-linear resistance 23. As described above, since the voltage of the first capacitor 55 rises rapidly, the time required to reach the operating voltage V _Clamp of the non-linear resistor 23 can be greatly shortened as compared with the case of the first embodiment of FIG. As a result, it is possible to significantly reduce the interruption time. The circuit configuration and operation other than those described above are the same as those in the first embodiment shown in FIG.

1, 2 Circuit Breaker 11 First Inductor 12 Switch 13 Semiconductor Power Converter 14 Second Inductor T ₁ First External Connection Terminal T ₂ Second External Connection Terminal 21 DCDC Converter 22 Energy Storage 23 Nonlinear Resistance 24 mechanical breaker 25 snubber circuit 26 mechanical disconnector 31 overcurrent detection unit 32 control unit 41 first command means 42 second command means 43 third command means 44 fourth command means 51 snubber capacitor 52 Snubber resistor 53 DC capacitor 54 Reverse blocking diode 55 First capacitor 56 Second capacitor

Claims (8)

A first inductor having a first external connection terminal;
A switch which is connected in series to the first inductor and has a second external connection terminal on the side opposite to the side to which the first inductor is connected, the switch being opened in response to a command. A mechanical circuit breaker for breaking a current path, a snubber circuit connected in parallel to the mechanical circuit breaker, and a series circuit connected to a parallel circuit composed of the mechanical circuit breaker and the snubber circuit, A switch consisting of a mechanical disconnector that opens the contact in response to a command to interrupt the current path,
What is claimed is: 1. One or a plurality of semiconductor power converters, which are provided on a wiring branched from a wiring that connects the first inductor and the switch, and which are cascade-connected to each other. 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 to the semiconductor power converter;
Equipped with
The semiconductor power converter,
Due to the switching operation of the semiconductor switch, a first DC side to which the second inductor or another semiconductor power converter different from the semiconductor power converter is connected and a side opposite to the first DC side. A DC/DC converter that converts a DC current input from one of a second DC side into a DC current of a desired magnitude and polarity and outputs the DC current to the other, wherein the input/output direction of the DC current is the first direction. A DC/DC converter capable of bidirectionally switching between the DC side and the second DC side of
An energy storage unit connected in parallel to the second DC side of the DCDC converter;
The direct current voltage connected to the energy storage unit in parallel and applied to the energy storage unit exhibits a predetermined resistance value when the voltage is equal to or lower than a preset voltage, and is higher than the predetermined resistance value in other cases. A non-linear resistance showing a low resistance value,
Have
A circuit breaker, wherein 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 circuit breaker according to claim 1, wherein the energy storage unit includes a capacitor and a reverse blocking diode that is connected in series to the capacitor and blocks a charging current flowing into the capacitor. The energy storage unit is
A first capacitor connected in parallel with the non-linear resistance;
A second capacitor having a capacitance larger than that of the first capacitor and a charging voltage lower than the charging voltage of the first capacitor;
A reverse blocking diode connected in series to the second capacitor to block a charging current flowing into the second capacitor;
Have
The circuit breaker according to claim 1, wherein a series circuit including the second capacitor and the reverse blocking diode is connected in parallel to the first capacitor. The second inductor is connected in series to one of the semiconductor power converter of a plurality of said semiconductor power converter cascaded with each other, according to any one of claims 1 to 3 Circuit breaker. An overcurrent detection unit for detecting 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 that controls an opening operation for the mechanical breaker and the mechanical disconnector and a power conversion operation of the semiconductor power converter;
Equipped with
The control unit is
First command means for outputting a mechanical circuit breaker opening command for commanding the mechanical circuit breaker to start an opening operation after the overcurrent is detected by the overcurrent detector.
After detecting the overcurrent by the overcurrent detection unit, the current flowing through the mechanical breaker is made substantially zero until the opening operation of the mechanical breaker is completed based on the opening command for the mechanical breaker. Second command means for outputting a power conversion command for causing the semiconductor power converter to output the DC current to be converged,
Third command means for outputting a mechanical disconnector opening command for instructing the mechanical disconnector to start an opening operation after a lapse of a predetermined period from the output of the mechanical circuit breaker opening command When,
Fourth command means for outputting an off command for turning off the semiconductor switch in the semiconductor power converter when the opening operation of the mechanical breaker is completed,
The a circuit breaker apparatus according to any one of claims 1-4. The snubber circuit includes a series circuit of a snubber capacitor and a snubber resistor, the circuit breaker apparatus according to any one of claims 1-5. The semiconductor switch is
A semiconductor switching element that passes current in one direction when turned on,
A return diode connected in anti-parallel to the semiconductor switching element,
The a circuit breaker apparatus according to any one of claims 1-6. The mechanical circuit breaker is
Fixed contactor,
A movable contact movable between a closed position in contact with the fixed contact and an open position separated from the fixed contact;
The a circuit breaker apparatus according to any one of claims 1-7.

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