JP2016149213A - Circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit breaker of which the stationary loss is zero at normal time and which is capable of breaking a current path at high speed when an accident occurs.SOLUTION: A circuit breaker 1 comprises: a semiconductor power converter 11 which outputs a predetermined DC current by performing a switching operation of a semiconductor switch that is provided insides in response to a command; a single phase transformer 12 which includes a primary coil 21 including a first external connection terminal Tin one end and a secondary coil 22 that is connected with the semiconductor power converter 11 in series and in which the other end of the primary coil 21 at a side opposite to the first external connection terminal Tis connected to a pair of the secondary coils 22 and the semiconductor power converter 11 that is connected in series with each other; and a mechanical breaker 13 which includes a second external connection terminal Tin one end and in which the other end at a side opposite to the second external connection terminal Tis connected to a connection point between the pair of the secondary coils 22 and the semiconductor power converter 11 that are connected in series with each other, and the primary coil 21, the mechanical breaker 13 being opened to break the current path in accordance with a command.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a circuit breaker that interrupts 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, a large number of future offshore wind power generation systems are assumed, and a multi-terminal DC power transmission system (HVDC: high-voltage direct-current) using a voltage source converter is used. The introduction is expected.

  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. 19 is a circuit diagram illustrating a general hybrid circuit breaker. For example, as shown in FIG. 19, a hybrid circuit breaker 100 includes a current limiting inductor 61, a mechanical circuit breaker (circuit breaker) 62, a commutation auxiliary semiconductor switch 63, a main semiconductor switch 64, an arrester ( The main circuit is composed of the non-linear resistance 65. In normal operation, power is supplied to the load via the current limiting inductor 61, the mechanical circuit breaker 62, and the commutation auxiliary semiconductor switch 63, and the commutation auxiliary semiconductor switch 63 is turned off in the case of an accident such as a ground fault or a short circuit. It commutates to the main semiconductor switch 64. Since the required breakdown voltage of the commutation auxiliary semiconductor switch 63 is about several percent of that of the main semiconductor switch 64, 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 62 that can be opened within 1 [ms], the interruption time is made 2 [ms] or less. Can do.

B. Bachmann, G. Mauthe, E. Ruoss, HP Lips, “500kV wind-cooled high-voltage DC power supply Circuit of Circuit Breaker (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" And current limiter (Solid-State Circuit Breakers and Current Limiters for Medium-Voltage Systems Having Distributed Power Systems) (USA), Institute of Electrical and Electronics Engineers of Japan (EV) 19, no. 5, pp. 1333-1340, September 2004 By M. Steiler, K. Frohlich, W. Holaus, K. Kaltenegger, “New Hybrid Voltage Limiting Circuit Breaker for Medium Voltage: Principle 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 for current interruption (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.

  In addition, the circuit breaker using the semiconductor switch method has a problem in that a steady loss occurs because a constant current 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.

  Moreover, the above-mentioned hybrid circuit breaker has a required breakdown voltage of the commutation auxiliary semiconductor switch of about several percent of that of the main semiconductor switch, so that the steady loss can be reduced compared to the semiconductor switch system. 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.

  Therefore, in view of the above problems, an object of the present invention is to provide a circuit breaker capable of interrupting a current path at a high speed when an accident occurs and a steady loss is zero in a normal state.

  In order to achieve the above object, according to the present invention, the circuit breaker is one or a plurality of semiconductor power converters cascade-connected to each other, and switches a semiconductor switch provided therein according to a command. A semiconductor power converter that outputs a predetermined direct current by operating, a primary winding having a first external connection terminal at one end, and a secondary winding connected in series with the semiconductor power converter, The other end of the primary winding on the side opposite to the first external connection terminal is connected to a set of a secondary winding and a semiconductor power converter connected in series with each other. A pair of a secondary winding and a semiconductor power converter having a second external connection terminal at one end and the other end opposite to the second external connection terminal connected in series to each other Mechanical disconnection connected to the connection point of the primary winding A is, and a mechanical breaker for interrupting the current path by opening in response to a command.

  Here, the semiconductor power converter performs a switching operation of a semiconductor switch provided therein in accordance with a command, thereby obtaining a direct current input from one of the first DC side and the second DC side. A DC / DC converter that converts a DC current of magnitude and polarity and outputs it to the other, and can switch the input / output direction of the DC current bi-directionally between a first DC side and a second DC side Energy connected in parallel to the first DC side to which the DCDC converter and the secondary winding or another semiconductor power converter different from the semiconductor power converter is connected, and the second DC side opposite to the first DC side When the DC voltage applied to the energy storage unit is equal to or lower than a preset voltage, the storage unit and the energy storage unit are connected in parallel. Also And a nonlinear resistance exhibited gastric resistance, may have a.

  The circuit breaker also includes an overcurrent detector that detects whether or not an overcurrent has occurred on the external wiring connected to the circuit breaker, an opening operation for the mechanical breaker, and the power of the semiconductor power converter. A control unit that controls the conversion operation, and in this case, when the overcurrent detection unit detects an overcurrent, the control unit issues an opening command that instructs the mechanical circuit breaker to start the opening operation. A first command means for outputting, and a direct current for converging the current flowing through the mechanical circuit breaker to zero between the time when the opening instruction is output and the time when the opening operation of the mechanical circuit breaker is completed. A second command means for outputting a power conversion command to be output to the converter, and a third command for outputting an off command for turning off the semiconductor switch in the semiconductor power converter when the opening operation of the mechanical circuit breaker is completed. And command means.

  Further, according to the first aspect of the present invention, the terminal on the side opposite to the side to which the primary winding is connected of the set of the secondary winding and the semiconductor power converter connected in series with each other, The first external connection terminal and the second external connection terminal have opposite polarities, or the first ground terminal and the second ground terminal.

  According to the second aspect of the present invention, the set of the secondary winding and the semiconductor power converter connected in series with each other and the mechanical circuit breaker are connected in parallel, and the circuit breaker is A terminal or third ground terminal opposite to the polarity of the first external connection terminal, and a terminal or fourth ground terminal opposite to the polarity of the second external connection terminal are provided.

  Further, in the set of the secondary winding and the semiconductor power converter connected in series to each other, the secondary winding is one of the plurality of semiconductor power converters cascade-connected to each other. Connected in series.

  The circuit breaker may further include an inductor connected in series to the semiconductor power converter or the secondary winding in a set of the secondary winding and the semiconductor power converter connected in series with each other.

  Here, in the set of the secondary winding and the semiconductor power converter connected in series to each other, the inductor is connected in series to any one of the plurality of semiconductor power converters cascade-connected to each other. Connected.

  Further, the above-described semiconductor switch may include a semiconductor switching element that allows current to flow in one direction when turned on, and a feedback diode connected in antiparallel to the semiconductor switching element.

  The mechanical circuit breaker has a fixed contact and 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. When the movable contact moves to the open circuit position, the contact is opened and the current path is interrupted.

  According to the present invention, it is possible to realize a circuit breaker capable of interrupting a current path at a high speed when an accident occurs because a steady loss is zero when normal.

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

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

  In addition, according to the present invention, it is possible to easily achieve a high breakdown voltage of the circuit breaker by simply adjusting the number of cascaded semiconductor power converters.

  Further, according to the present invention, the DC / DC converter in the semiconductor power converter is configured as a bidirectional DC / DC 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 this invention and the 2nd Example. It is a circuit diagram explaining an example of the electrical connection of the secondary winding of the single phase transformer in the circuit breaker by the 1st Example of this invention and the 2nd Example. It is a circuit diagram which shows the modification of the circuit breaker by the 1st Example of this invention. It is a circuit diagram explaining an example of the electrical connection of the secondary winding of the single phase transformer in the modification of the circuit breaker by the 1st Example of this invention, and a 2nd Example. 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 figure which shows the equivalent circuit explaining the normal operation | movement of the circuit breaker by the 1st Example of this invention. It is a figure which shows the equivalent circuit explaining the operation | movement immediately after the occurrence of the accident of the load side of the circuit breaker by the 1st Example of this invention. It is a figure which shows the equivalent circuit explaining operation | movement when the semiconductor power converter in the circuit breaker by the 1st Example of this invention performs power conversion operation | movement. It is a figure which shows the equivalent circuit explaining operation | movement when the semiconductor power converter in the circuit breaker by the 1st Example of this invention complete | finishes power conversion operation | movement. It is a control block diagram explaining the power conversion instruction | command for controlling the converter electric current in the semiconductor power converter in the circuit breaker by the 1st Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the circuit diagram used for the simulation of the circuit breaker by 1st Example of this invention, (A) had a short circuit accident at the near end of the circuit breaker when the RL load was connected to the circuit breaker. (B) shows a circuit diagram when a short circuit accident occurs at the closest end of the circuit breaker when a regenerative load is connected to the circuit breaker. It is a figure explaining the circuit parameter of the simulation circuit diagram shown in FIG. It is a figure which shows the simulation waveform at the time of operating the circuit breaker by the 1st Example of this invention with the simulation circuit of FIG. 13 (A). It is a figure which shows the simulation waveform at the time of operating the circuit breaker by 1st Example of this invention with the simulation circuit of FIG.13 (B). It is a circuit diagram explaining the semiconductor power converter in the circuit breaker by the 2nd example of the present invention. It is a circuit diagram which shows the modification of the circuit breaker by the 2nd Example of this 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 semiconductor power converter, a single phase transformer, and a mechanical circuit breaker. The semiconductor power converter outputs a predetermined direct current by switching a semiconductor switch provided therein in response to a command, and is provided alone or in a state in which a plurality are cascade-connected to each other. . The single-phase transformer has a primary winding having a first external connection terminal at one end thereof, and a secondary winding connected in series with the semiconductor power converter. The other end of the primary winding of the single-phase transformer on the side opposite to the first external connection terminal is connected to a set of a secondary winding and a semiconductor power converter connected in series with each other. . The mechanical circuit breaker is opened in accordance with a command to interrupt the current path, and has a second external connection terminal at one end thereof. The other end of the mechanical circuit breaker on the side opposite to the second external connection terminal is composed of a pair of a single-phase transformer secondary winding and a semiconductor power converter connected in series with each other, and a single-phase It is connected to the connection point of the primary winding of the transformer. Hereinafter, specific circuit configurations will be described in the first and second embodiments.

  FIG. 1 is a circuit diagram showing a circuit breaker according to a first embodiment of the present invention, and FIG. 2 is a semiconductor power converter in the circuit breaker according to the first embodiment and the second embodiment of the present invention. FIG. Hereinafter, components having the same reference numerals in different drawings mean components having the same functions. The circuit breaker 1 according to the embodiment of the present invention includes a semiconductor power converter 11, a single-phase transformer 12, and a mechanical circuit breaker 13. In the example shown in FIG. 1, the circuit breaker 1 includes a pair of the secondary winding 22 of the single-phase transformer 12 and the semiconductor power converter 11 that are connected in series to each other, to which a DC power supply system is applied. Installed in parallel, installed on the DC power supply system so that the primary winding 21 of the single-phase transformer 12 is located on the power source side and the mechanical circuit breaker 13 is located on the load side. The

The semiconductor power converter 11 is cascade-connected singly or plurally on a wiring branched from a connection point P ₁ between a primary winding 21 of a single-phase transformer 12 described later and a mechanical breaker 13 described later. Provided in the state. In this specification, when there is one semiconductor power converter 11, a side to which a secondary winding 22 of a single-phase transformer 12 described later is connected is referred to as a “first DC side”, When the semiconductor power converters 11 are cascade-connected to each other, the side to which another semiconductor power converter 11 different from the semiconductor power converter 11 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 11 are cascade-connected to each other on the first DC side. A high breakdown voltage of the circuit breaker 1 can be easily realized by simply adjusting the number of semiconductor power converters 11 connected in cascade.

  The semiconductor power converter 11 includes a DCDC converter 31, an energy storage unit 32, and a non-linear resistor 33. The semiconductor power converter 11 performs a switching operation on a semiconductor switch provided in the DCDC converter 31 according to a command, thereby performing a predetermined direct current Output current.

  The DCDC converter 31 in the semiconductor power converter 11 is configured as a bidirectional DCDC converter. As an example, in the example shown in FIGS. 1 and 2, the DCDC converter 31 in the semiconductor power converter 11 is configured as a two-quadrant bidirectional DCDC converter (chopper cell). That is, the DCDC converter 31 in the semiconductor power converter 11 converts a 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. The current is converted into current and output to the other, 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 31 in the semiconductor power converter 11 as a bidirectional 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 turned on, and a feedback diode D that is connected in antiparallel to the semiconductor switching element S. 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. As an alternative example, a 4-quadrant bidirectional DCDC converter may be used as the DCDC converter 31 in the semiconductor power converter 11 instead of the 2-quadrant bidirectional DCDC converter shown in FIGS. The four-quadrant bidirectional DCDC converter is equivalent to a general single-phase full-bridge inverter.

  The energy storage unit 32 in the semiconductor power converter 11 is connected in parallel to the second DC side of the DCDC converter 31. An example of the energy storage unit 32 is a DC capacitor. In the case of a DC capacitor, when the circuit breaker 1 is operated, the DCDC converter 31 is operated to perform initial charging.

The non-linear resistance 33 in the semiconductor power converter 11 is connected in parallel to the energy storage unit 32, and a DC voltage applied to the energy storage unit 32 is 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 33, there is MOV (Metal Oxide Variable Resistor) (also referred to as “varistor” or “arrester”). The operating voltage V _R of the nonlinear resistor 33 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 _R of the nonlinear resistor 33 needs to be set to 3.3 [kV] or less.

  Since the DC capacitor 32 and the non-linear resistor 33 are connected in parallel, when the DC capacitor 32 is charged by the accumulated energy of the excitation inductance and leakage inductance of the single-phase transformer 12, the charging voltage of the DC capacitor 32 is When the voltage gradually rises and reaches the operating voltage of the non-linear resistor 33, the charging voltage of the DC capacitor 32 is clamped by the operating voltage of the non-linear resistor 33 and the energy stored in the secondary winding 22 is consumed by the non-linear resistor 33. Is done. The energy storage unit 32 and the nonlinear resistor 33 may be realized by other elements as long as they perform a series of operations of charging the DC capacitor 32 and consuming by the nonlinear resistor 33 as described above. It may be replaced with a secondary battery or an electric double layer capacitor.

  The primary winding 21 and the secondary winding 22 included in the single-phase transformer 12 are arranged close to each other mechanically (physically). The second embodiment is particularly characterized in the electrical connection relationship between the secondary winding 22, the primary winding 21, the semiconductor power converter 11, and the mechanical circuit breaker 13. Hereinafter, the connection relationship of the single-phase transformer 12 will be described. In each of the drawings showing the single-phase transformer 12, the polarities of the primary winding 21 and the secondary winding 22 are represented by black circles “·”.

The single-phase transformer 12 has a first external connection terminal T ₁ at one end of the primary winding 21. A circuit on the power supply side is connected to the first external connection terminal T ₁ . On the other hand, the secondary winding 22 of the single-phase transformer 12 is connected in series with the semiconductor power converter 11. With respect to the polarity of the primary winding 21 represented by the black circle “·”, the secondary winding 22 is wound with a wire so that the polarity is aligned in the direction shown in the figure and electrically connected to each component. . When the number of semiconductor power converters 11 is one, the secondary winding 22 is connected in series to the semiconductor power converter 11, and when a plurality of semiconductor power converters 11 are cascade-connected, a plurality of cascade-connected semiconductor power converters 11 are connected. The semiconductor power converter 11 is connected in series to any one of the semiconductor power converters. As described above, in the single-phase transformer 12, the other ends of the primary winding 21 on the side opposite to the first external connection terminal T ₁ (that is, the connection point P ₁ ) are connected in series with each other. A set consisting of the secondary winding 22 and the semiconductor power converter 11 is connected.

  The electrical connection relationship between the secondary winding 22 of the single-phase transformer 12 and the semiconductor power converter 11 is not limited to that shown in FIG. FIG. 3 is a circuit diagram illustrating an example of the electrical connection of the secondary winding of the single-phase transformer in the circuit breaker according to the first and second embodiments of the present invention. In the single-phase transformer 12, the secondary winding 22 may be electrically connected in series to any one of the plurality of semiconductor power converters 11 cascade-connected, for example, As shown in FIGS. 3A and 3B, the secondary winding 22 of the single-phase transformer 12 is one of the semiconductor power converters 11 of the semiconductor power converters 11 located at both ends of the cascade connection. Installed on the side where the semiconductor power converter 11 is not connected. Further, for example, as shown in FIG. 3C, the secondary windings 22 of the single-phase transformer 12 are respectively installed between the semiconductor power converters 11 adjacent to each other. When there is one semiconductor power converter 11, the secondary winding 22 of the single-phase transformer 12 is simply electrically connected in series to the semiconductor power converter 11. As described above, the secondary winding 22 of the single-phase transformer 12 is either in the case where a plurality of semiconductor power converters 11 are cascade-connected or in the case where only one semiconductor power converter 11 is provided. The semiconductor power converter 11 is electrically connected so as to be provided at any position on the same wiring.

One end of the mechanical circuit breaker 13 is a connection point P ₁ between the primary winding 21 of the single-phase transformer 12 and a set of the secondary winding 22 and the semiconductor power converter 11 connected in series to each other. Connected to. Further, the mechanical circuit breaker 13 is connected to a side (ie, a connection point) of the primary power 21 of the single-phase transformer 12 and the set of the secondary power 22 and the semiconductor power converter 11 connected in series with each other. A second external connection terminal T ₂ is provided on the side opposite to the side where P ₁ is present. Circuit on the load side is connected to the second external connection terminal T _2. The mechanical circuit breaker 13 has a fixed contact, and 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. When the movable contact moves to the open circuit position, the pole is opened and the current path is interrupted. Examples of the mechanical circuit breaker 13 include a vacuum circuit breaker, a gas circuit breaker, or an air blowing circuit breaker.

In the first embodiment of the present invention, the semiconductor power converter 11, the single-phase transformer 12, and the mechanical circuit breaker 13 are connected as described above, so that the secondary winding 22 and the semiconductor power connected in series with each other are connected. A terminal P ₂ on the side opposite to the side to which the primary winding 12 is connected (that is, the side having the connection point P ₁ ) of the set including the converter 11 is the first external connection terminal T ₁ and the second external connection terminal T ₁ . The first ground terminal G ₁ and the second ground terminal G ₂ respectively corresponding to the external connection terminal T ₂ .

In the present embodiment, the case where the circuit breaker 1 operates as a DC circuit breaker has been described. However, the circuit breaker 1 can also operate as an AC circuit breaker, and in this case, secondary circuits connected in series with each other. A terminal P ₂ on the side opposite to the side to which the connection point P ₁ is connected of the set of the winding 22 and the semiconductor power converter 11 is defined as a first external connection terminal T ₁ and a second external connection terminal T. the _second polarity to the terminal G ₁ and G ₂ of the opposite polarity. When the circuit breaker 1 operates as a DC breaker, the DCDC converter 31 in the semiconductor power converter 11 may be configured by either a two-quadrant bidirectional DCDC converter or a four-quadrant bidirectional DCDC converter. When the device 1 operates as an AC circuit breaker, the DCDC converter 31 in the semiconductor power converter 11 is configured as a four-quadrant bidirectional DCDC converter.

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. As a modification, the side including the first external connection terminal T ₁ and the ground terminal G ₁ may be the load side, and the side including the second external connection terminal T ₂ and the ground terminal G ₂ may be the power supply side.

  As a modification of the first embodiment of the present invention described above, the circuit breaker 1 includes a semiconductor power converter or a secondary winding in a set of a secondary winding and a semiconductor power converter connected in series to each other. An inductor for current control connected in series to the line may be further provided. FIG. 4 is a circuit diagram showing a modification of the circuit breaker according to the first embodiment of the present invention. As shown in FIG. 4, the circuit breaker 1 includes a semiconductor power converter 11 or a secondary winding in a set including a secondary winding 22 of a single-phase transformer 12 and a semiconductor power converter 11 connected in series. A current control inductor 14 connected in series to the line 22 is further provided. In the circuit breaker 1 described with reference to FIGS. 1 and 2, the leakage inductance of the secondary winding 22 of the single-phase transformer 12 has a function equivalent to that of the current control inductor 14 in FIG. Have.

  The electrical connection relationship between the inductor 14, the secondary winding 22 and the semiconductor power converter 11 is not limited to that shown in FIG. FIG. 5 is a circuit diagram for explaining an example of electrical connection of inductors in the circuit breakers according to the first and second embodiments of the present invention. In the set of the secondary winding 22 and the semiconductor power converter 11 that are connected in series with each other, the inductor 14 is one of the plurality of semiconductor power converters 11 that are cascade-connected to each other. For example, as shown in FIG. 5A, the inductor 14 includes the semiconductor power converter 11 at the upper end in the figure among the semiconductor power converters 11 located at both ends of the cascade connection. The secondary winding 22 of the single-phase transformer 12 is arranged on the side where the other semiconductor power converter 11 is not connected, and the lower end in the figure of the semiconductor power converter 11 located at both ends of the cascade connection. The semiconductor power converter 11 is arranged on the side where the other semiconductor power converter 11 is not connected. Further, for example, as shown in FIGS. 5B and 5C, the inductor 14 and the secondary winding 22 of the single-phase transformer 12 are placed at arbitrary positions of the semiconductor power converter 11 cascade-connected to each other. Be placed. For example, although not shown here, the inductor 14 and the secondary winding 22 of the single-phase transformer 12 may be connected in series and then connected in series to the semiconductor power converter 11. When there is one semiconductor power converter 11, the inductor 14 and the secondary winding 22 of the single-phase transformer 12 are simply electrically connected in series to the semiconductor power converter 11. As described above, the secondary winding of the inductor 14 and the single-phase transformer 12 is used in any case where a plurality of semiconductor power converters 11 are cascade-connected and only one semiconductor power converter 11 is provided. The line 22 is electrically connected so as to be provided at any position on the same wiring as the semiconductor power converter 11.

Hereinafter, the power supply side DC voltage is represented by V _dc , the load voltage is represented by v _L , and the total voltage of the semiconductor power converters 11 on the side of the N cascade-connected semiconductor power converters 11 is represented by v _HB . Further, the number of turns of the primary winding 21 of the single-phase transformer 12 is represented by N ₁ , the number of turns of the secondary winding 22 is represented by N ₂ , and the voltage appearing at both ends of the primary winding 21 is represented by v _N1 , secondary representing the voltage appearing across the winding 22 at v _N2. Further, voltages of DC capacitors connected in parallel to each of the N semiconductor power converters 11 are represented by v _C1 ,..., V _CN (where N is a natural number). Further, a power supply current flowing from the first external connection terminal T ₁ to the circuit breaker 1 is i _S, and a current flowing from the connection point P ₁ to the second external connection terminal T ₂ is a load current i _L. For the voltage and current in the figure, the direction of the arrow is positive. The polarities of the primary winding 21 and the secondary winding 22 of the single-phase transformer 12 are represented by black circles “·”.

  FIG. 6 is a block diagram illustrating a control system in the circuit breaker according to the first embodiment of the present invention. The control system shown in FIG. 6 can be applied to both the circuit breaker 1 described with reference to FIGS. 1 to 3 and the circuit breaker 1 described with reference to FIGS. 4 and 5. The circuit breaker 1 has an overcurrent detection unit 41 and a control unit 42 as its control system.

The overcurrent detection unit 41 detects whether or not an overcurrent has occurred on the load-side external wiring connected to the second external connection terminal T ₂ of the circuit breaker 1. The detection of overcurrent generation may be realized by a known method. For example, when an accident such as a ground fault or a short circuit occurs, the power source current i _S flowing from the first external connection terminal T ₁ to the circuit breaker 1 increases, so that the current i is detected using a current detector (not shown). _S may be constantly monitored, and it may be determined that “overcurrent has occurred” when the power supply current i _S becomes a predetermined value larger than the rated current. 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 42 controls the opening operation for the mechanical circuit breaker 13 and the power conversion operation of the semiconductor power converter 11. That is, the control unit 42, when the overcurrent detection unit 41 detects an overcurrent, a first command means 51 that outputs an opening command that commands the mechanical circuit breaker 13 to start a opening operation; Electric power that causes the semiconductor power converter 11 to output a DC current that converges the current flowing through the mechanical circuit breaker 13 to zero after the opening command is output and before the opening operation of the mechanical circuit breaker 13 is completed. Second command means 52 that outputs a conversion command and third command means 53 that outputs a command to turn off the semiconductor switch S in the semiconductor power converter 11 when the opening operation of the mechanical circuit breaker 13 is completed. And having.

  The first command means 51, the second command means 52, and the third command means 53 may be constructed, for example, in a software program format, or may be constructed by a combination of various electronic circuits and software programs. For example, when these means are constructed in a software program format, the arithmetic processing unit in the control unit 42 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. 8 to 11 are diagrams showing an equivalent circuit for explaining the operation of the circuit breaker according to the first embodiment of the present invention. Here, L _l represents the leakage inductance of the secondary winding 22 of the single-phase transformer 12. The leakage inductance L _l of the secondary winding 22 is calculated by a known method. In addition, since the leakage inductance of the primary winding 21 of the single phase transformer 12 does not have a big influence on circuit operation | movement, it is not described in FIGS.

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 .

Circuit breaker 1 when the overcurrent has not occurred on the external wiring connected second circuit breaker 1 2 to an external connection terminal T ₂ the load side, performs a normal operation (step S101). That is, in the normal state, as shown in FIG. 8, the mechanical circuit breaker 13 is turned on, and power is supplied from the power source side to the load side via the primary winding 21 of the single-phase transformer 12 and the mechanical circuit breaker 13. Is done. At this time, each diode D in the semiconductor power converter 11 functions, so that the semiconductor power converter 11 itself operates as a diode, the converter current i _HB becomes zero, and the power source current i _S and the load current i _L Are equal. Therefore, the steady loss of the circuit breaker 1 at the normal time is zero.

Further, the DC voltage V _dc on the power supply side and the DC capacitor voltage v _C (= v _C1 = v _CN ) in the semiconductor power converter 11 need to satisfy the relationship of Equation 1. N indicates the number of semiconductor power converters 11 (in other words, the number of DC capacitors).

As shown in FIG. 8, under normal conditions, the load current i _L and the power supply current i _S are equal to each other, that is, “i _L = i _S ”, according to Kirchhoff's current law. Further, in a normal steady state, the magnetic flux in the iron core of the single-phase transformer 12 does not change with time, so that Formula 2 is established.

In step S102, the overcurrent detection unit 41, 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 41 does not detect an overcurrent, the process returns to step S101 and continues normal operation. When the overcurrent detection unit 41 detects an overcurrent, the process proceeds to step S103.

For example the overcurrent detection unit 41 at time t ₀ is assuming that detects the occurrence of an overcurrent, the equivalent circuit of the circuit breaker 1 at time t ₀ is immediately after the accident occurred in the load side is represented as shown in FIG. If the voltage drop in the mechanical circuit breaker 13 is ignored, the circuit equation shown in Equation 3 is established.

At this time, an exciting current that increases in a linear function flows in the power supply current i _S and the load current i _L. The current rate of increase, when the excitation inductance of the single-phase transformer 12 has a L _M, is given by V _dc / L _M. Therefore, by increasing the excitation inductance L _M of the single-phase transformer 12, it is possible to suppress the current increase rate during the accident. Incidentally, the exciting inductance L _M of the single-phase transformer 12, when the magnetic resistance of the single-phase transformer 12 has the R, which is expressed as shown in Equation 4.

When a short circuit or ground fault occurs at time t ₀ , the power supply current i _S increases. Therefore, the overcurrent detection unit 41 constantly monitors the power supply current i _S using a current detector (not shown), and the power supply current i _S When i _S becomes larger than the rated current by a predetermined value (for example, rated current 120%), it is determined that “overcurrent has occurred”. The time when it is determined that this accident has occurred is assumed to be 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 excitation inductance L _M of the single-phase transformer 12, the load, the reference current value, and the like.

In the single-phase transformer 12 between time t ₀ immediately after the occurrence of the load-side accident and time t ₁ at which it is determined that the accident has occurred, the relational expression expressed by Equation 5 holds. However, the influence of the leakage inductance of each winding is ignored.

  When the overcurrent detection unit 41 detects an overcurrent in step S102, the first command means 51 of the control unit 42 instructs the mechanical circuit breaker 13 to start the opening operation in step S103. Outputs a command.

Even if the opening command is given to the mechanical circuit breaker 13, the mechanical circuit breaker 13 does not immediately complete the opening operation, but a delay time due to the mechanical structure of the mechanical circuit breaker 13 occurs. Completes the opening operation after a short delay. 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. Since the mechanical circuit breaker 13 can interrupt the current path only at the time of zero current, it is necessary to make the load current i _L flowing through the mechanical circuit breaker 13 zero. Therefore, in step S104, the second command means 52 of the control unit 42 determines the current flowing through the mechanical circuit breaker 13 after the opening command is output until the opening operation of the mechanical circuit breaker 13 is completed. A power conversion command for causing the semiconductor power converter 11 to output a direct current that converges to zero is output. The semiconductor switching element S of the semiconductor switch in the DCDC converter 31 in the semiconductor power converter 11 performs a PWM switching operation based on the received power conversion command. As a result, as shown in FIG. 10, the semiconductor power converter 11 is equivalent to operating as a control voltage source that outputs v _HB . Therefore, in FIG. 10, a circuit equation like Formula 6 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 7. In Equation 7, K _p denotes a proportional gain, K _I denotes integral gain, i ^* _HB represents 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 Expression 7, the first term, the second term, the third term, and the fourth term on the right side correspond to feedforward control, and the fifth term on the right side corresponds to feedback control (PI). Substituting Equation 7 into Equation 6 yields Equation 8.

As shown in Equation 8, the converter current i _HB responds to the command value i ^* _HB with a second order delay. At this time, if the control value i ^* _HB of the converter current is set to i _S so that the converter current i _HB matches the power supply current i _S flowing in the primary winding of the single-phase transformer 12, The load current i _L can be made zero by Kirchhoff's current law. The time required to make the load current i _L zero (that is, the time required to match the converter current i _HB to the power supply current i _S ) is the carrier frequency, equivalent switching frequency, digital control of the semiconductor power converter 11. Depends on the method. For example, if a high voltage SiC MOSFET capable of realizing a low loss and high switching frequency operation is used, it is sufficiently possible to realize the time required to make the load current i _L zero at 1 [ms] or less.

Here, when the exciting current included in the power source current i _S is i _M , Equation 9 is established from the relationship of the transformer magnetomotive force. However, the influence of the leakage inductance of each winding is ignored.

By substituting “i _S = i _HB ” into Equation 9, Equation 10 is obtained.

  Based on the above, the generation principle of the power conversion command based on Expression 7 will be described as follows. FIG. 12 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. In the control of the converter current, feedback control and feedforward control are used in combination.

As shown in FIG. 12, in the block B1 related to the feedback control, the converter current i _HB detected by the current detector (not shown) and the power source current i _S detected by the current detector (not shown). Deviation (i _HB −i _S ) is suppressed by applying PI control to the difference. On the other hand, in the block B2 related to the feedforward control, the power source side DC voltage v _dc , the voltage v _N1 appearing at both ends of the primary winding 21 of the single-phase transformer 12, the voltage v _N2 appearing at both ends of the secondary winding 22, By using v _f obtained from the voltage L _l d (i _HB ) / dt appearing in the leakage inductance L _l of the secondary winding 22, the current controllability is improved. A voltage sensor (not shown) is used for the power source side DC voltage v _dc , the voltage v _N1 appearing at both ends of the primary winding 21 of the single-phase transformer 12, and the voltage v _N2 appearing at both ends of the secondary winding 22. Can be obtained by direct detection. Further, the voltage L _l d (i _HB ) / dt appearing in the leakage inductance of the secondary winding is obtained by calculating using the value of L _l acquired in advance by a known method and the detected converter current i _HB. Just do it. The v _f divided by the number N of the semiconductor power converter 11 by the block B3, and power conversion command v ^* _j output and is added for each semiconductor power converter 11 and the output of the block B3 of the block B1 is generated The The power conversion command v ^* _j for each semiconductor power converter 11 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 11.

When the DCDC converter 31 in the semiconductor power converter 11 is configured as a two-quadrant bidirectional DCDC converter, a “phase shift PWM method” that shifts the initial phase of the triangular wave carrier used for PWM control by 360 ° / N is used. When applied to control of the DCDC converter 31 of each semiconductor power converter 11, the equivalent switching frequency can be increased. Specifically, if the carrier frequency is f _C , the equivalent switching frequency is Nf _C. Alternatively, when the DCDC converter 31 in the semiconductor power converter 11 is configured as a four-quadrant bidirectional DCDC converter, a “phase shift PWM method” that shifts the initial phase of the triangular wave carrier used for PWM control by 180 ° / N is used. If applied to control of the DCDC converter 31 of the semiconductor power converter 11, 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 leakage inductance L _l of the secondary winding 22.

  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 11 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, for example, a 3.3 [kV] / 1500 [A] SiC power module (SiC MOSFET and SiC SBD (Schottky Barrier Diode)) is used as the semiconductor power converter 11, a 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 11 is increased.

  The output of the power conversion command in step S104 has been described above, but the processing in step S104 may be performed simultaneously with the output of the opening command in step S103.

  Returning to FIG. 7, in step S <b> 105, the mechanical circuit breaker 13 starts the opening operation in response to the opening command from the second command means 52 in the control unit 42. As described above, the mechanical circuit breaker 13 can be operated only at zero current. However, the process of zeroing the current flowing through the mechanical circuit breaker 13 in step S104 is performed after the opening command is output. It is executed in a time sufficiently shorter than the time required to complete the 13 opening operations.

When the opening operation of the mechanical breaker 13 is completed (in this case the time t ₂ is), in step S106, the third command means 53 in the controller 42, all of the semiconductor in the semiconductor power converter 11 A command to turn off the switch S is output. The time “t ₂ −t ₁ ” required from the start of the power conversion operation of the semiconductor power converter 11 to the completion of the opening operation of the mechanical circuit breaker 13 is given after the opening instruction is given to the mechanical circuit breaker 13 It is equal to the delay time until the circuit breaker 13 actually completes the opening operation, and the time is, for example, 2 [ms].

Upon receiving the off command from the third command means 53 in the control unit 42, all the semiconductor switches S in the semiconductor power converter 11 are turned off, and the power conversion operation ends. Thereby, as shown in FIG. 11, only each diode D in the semiconductor power converter 11 functions. In this case, single-phase transformer 12 operates as an inductor, but represented the inductance L _M2 Then equation 11. However, the influence of the leakage inductance of each winding is ignored.

The stored energy of the single-phase transformer 12 including the leakage inductance is released to the DC capacitor 32 and the non-linear resistor 33 through the feedback diode D in the semiconductor power converter 11. Since the DC capacitor 32 and the non-linear resistor 33 in the semiconductor power converter 11 are connected in parallel, after the semiconductor switching element S of the semiconductor switch is turned off (that is, a period after time t ₂ ), a single unit including a leakage inductance is included. The DC capacitor 32 is charged by the energy stored in the phase transformer 12. As a result, the DC capacitor voltage v _C gradually increases and is clamped by the operating voltage V _R of the nonlinear resistor 33. After the DC capacitor 32 is charged to the operating voltage, the stored energy is consumed by the non-linear resistor 33.

  Until the DC capacitor 32 is charged to the operating voltage of the nonlinear resistor 33 by the stored energy of the single-phase transformer 12 including the leakage inductance, the circuit equation shown in Expression 12 is established.

From Equation 12, the voltage v _C and the power source current i _S (= i _HB ) of the DC capacitor 32 can be calculated by solving a second-order constant coefficient linear differential equation.

After the DC capacitor 32 is charged to the operating voltage, the circuit equation shown in Equation 13 is established. In Equation 13, the operating voltage of the nonlinear resistor 33 is V _R.

From Equation 13, the power supply current i _S and the converter current i _HB can be calculated by solving a first-order constant coefficient linear differential equation.

Next, the simulation result of the circuit breaker according to the first embodiment of the present invention will be described. FIG. 13 is a circuit diagram used for the simulation of the circuit breaker according to the first embodiment of the present invention. FIG. 13A is a short circuit accident at the closest end of the circuit breaker when an RL load is connected to the circuit breaker. (B) shows a circuit diagram when a short circuit accident occurs at the closest end of the circuit breaker when a regenerative load is connected to the circuit breaker. However, in FIG. 13B, the regenerative load is simulated by a direct current source. FIG. 14 is a diagram for explaining circuit parameters of the simulation circuit diagram shown in FIG. “PSCAD / EMTDC” was used for the simulation. Assuming application to high-voltage applications, the rated capacity P is 7.5 [MW], the rated DC voltage V _dc is 15 [kV], the rated power supply current I _S is 500 [A], and the rated load current I _L is 500 [A]. ]. The exciting inductance L _M of the single-phase transformer 12 was 10 [mH], and the turns ratio N ₁ / N ₂ was 2. The leakage inductance L _l of the secondary winding 22 used for current control was set to 0.5 [mH]. Further, assuming a 3.3 [kV] breakdown voltage semiconductor switching element, the initial DC capacitor voltage is 1.5 [kV], the number N of each semiconductor power converter 11 is 10, and the carrier frequency f _C is 2 [kHz]. ]. 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 14.

In the simulation, the dead time of the semiconductor switching element was set to zero assuming an analog control system with zero control delay. Further, the reference current value used for determining the generation of current was set to 120% of the rated current. The nonlinear resistor 33 has an operating voltage of 2 [kV], an infinite resistance value when the applied voltage is 2 [kV] or less, and a resistance value of zero when the voltage is 2 [kV] or more. did. The mechanical circuit breaker 13 was simulated as an ideal switch having zero impedance, and the delay time (= t ₂ −t ₁ ) from reception of the opening command to completion of the opening operation was set to 1.5 [ms].

FIG. 15 is a diagram showing simulation waveforms when the circuit breaker according to the first embodiment of the present invention is operated by the simulation circuit of FIG. When a RL load (7.5 [MW]) was connected to the circuit breaker 1, a case where a short circuit accident occurred at the closest end of the circuit breaker 1 at time t ₀ was simulated.

In the semiconductor power converter 11 before the time t ₀ when the short circuit accident occurs, the semiconductor power converter 11 itself operates as a diode by the function of each diode D in the semiconductor power converter 11. In this case, the power source current i _S and the load current i _L are both 500 [A], and the converter current i _HB is 0 [A] from Kirchhoff's current law. Accordingly, the power supply side DC voltage V _dc and the converter voltage v _HB are equal, and both are 15 [kV]. During this time, the voltage (V _dc / N) of the DC capacitor 32 in each semiconductor power converter 11 is charged to 1.5 [kV].

When a short circuit accident occurs at time t ₀ , the power supply current i _S and the load current i _L increase with a slope of 1.5 [kA / ms] (= V _dc / L _M ). From Equation 3, Equation 5, and Equation 6 and the relational expression “N ₁ / N ₂ = 2”, the converter voltage v _HB decreases to V _dc / 2.

At time t ₁ , an opening command is given to the mechanical circuit breaker 13. At the same time, a power conversion command for causing the semiconductor power converter 11 to output a direct current that converges the current flowing through the mechanical circuit breaker 13 to zero is output. Thereby, the semiconductor switching element S of the semiconductor switch in the semiconductor power converter 11 performs a PWM switching operation based on the received power conversion command. In this simulation, the time “t ₂ −t ₁ ” from the start of PWM operation and reception of the opening command to the completion of opening of the mechanical circuit breaker 13 is set to 1.5 [ms]. As shown in FIG. 15, at 0.35 [ms] after application of current control, the load current i _L becomes zero and the power source current i _S and the converter current i _HB become equal. It becomes a state that can be shut off. Equation 10, from the relationship equation "N ₁ / N ₂ = _2", the current increase rate of the power supply current i _S is the current increase rate of the power supply current i _S immediately after the accident _{(t 0 ≦ t ≦ t 1} ) Double (= 3.0 [kA / ms]). Since the converter power p _HB is always positive, the voltages v _C1 and v _C2 of the DC capacitor 32 increase and are finally clamped at 2 [kV] which is the operating voltage V _R of the nonlinear resistor 33.

And opening operation of the mechanical breaker 13 is completed at time t _2, the turning off the semiconductor switching element S of all the semiconductor switches of the semiconductor power converter 11 at the same time. The power supply current i _S and the converter current i _HB decrease linearly and become zero at time t ₃ . According to this simulation result, it can be seen that the required time “t ₃ −t ₀ ” from the occurrence of the short-circuit accident to the completion of current interruption is 4.8 [ms], and the circuit breaker 1 can realize high-speed interruption.

FIG. 16 is a diagram showing simulation waveforms when the circuit breaker according to the first embodiment of the present invention is operated by the simulation circuit of FIG. 13B. When a regenerative load (7.5 [MW]) was connected to the circuit breaker 1, a case where a short circuit accident occurred at the closest end of the circuit breaker 1 at time t ₀ was simulated.

Since a regenerative load is assumed in this simulation, both the power source current i _S and the load current i _L are −500 [A] when normal before time t ₀ when a short circuit accident occurs. The waveform of each part is the same as in FIG. According to this simulation result, the required time “t ₃ −t ₀ ” from the occurrence of the short-circuit accident to the completion of current interruption is 5.4 [ms], and it can be seen that the circuit breaker 1 can realize high-speed interruption.

  Next, a second embodiment of the present invention will be described. FIG. 17 is a circuit diagram illustrating a semiconductor power converter in a circuit breaker according to a second embodiment of the present invention. The circuit breaker 1 according to the first embodiment described above is for a DC power supply system to which a set of the secondary winding 22 of the single-phase transformer 12 and the semiconductor power converter 11 connected in series is applied. However, the circuit breaker 2 according to the second embodiment of the present invention includes the secondary winding 22 of the single-phase transformer 12 and the semiconductor power converter 11 connected in series. The set is installed in series with the DC power supply system. The circuit breaker 2 according to the second embodiment of the present invention includes a semiconductor power converter 11, a single-phase transformer 12, and a mechanical circuit breaker 13, as in the first embodiment. A set of the secondary winding 22 of the single-phase transformer 12 and the semiconductor power converter 11 connected in series with each other and the mechanical circuit breaker 13 are connected in parallel. Each configuration will be described below.

The semiconductor power converter 11 is singly or plurally connected in cascade with each other on the wiring branched from the connection point P ₁ between the primary winding 21 of the single-phase transformer 12 and the mechanical circuit breaker 13. Provided. As in the first embodiment, when the number of the semiconductor power converter 11 is one, the side to which the secondary winding 22 of the single-phase transformer 12 is connected is referred to as a “first DC side”, and a plurality of semiconductors When the power converters 11 are cascade-connected to each other, a side to which another semiconductor power converter 11 different from the semiconductor power converter 11 is connected is also referred to as a “first DC side”. The DC side opposite to the “first DC side” is referred to as a “second DC side”. As an example, FIG. 17 shows a case where a plurality (N, where N is an integer of 2 or more) semiconductor power converters 11 are cascade-connected to each other on the first DC side. A high breakdown voltage of the circuit breaker 1 can be easily realized by simply adjusting the number of semiconductor power converters 11 connected in cascade. The configuration of the semiconductor power converter 11 is the same as that described in the first embodiment. However, when the energy storage unit 32 in the semiconductor power converter 11 is a DC capacitor, the second embodiment is provided with an initial charging circuit (not shown) separately from the case of the first embodiment. There is a need.

The configuration of the single-phase transformer 12 is the same as that described in the first embodiment. That is, the single-phase transformer 12 has the first external connection terminal T ₁ at one end of the primary winding 21. A circuit on the power supply side is connected to the first external connection terminal T _1, and the secondary winding 22 of the single-phase transformer 12 is connected in series with the semiconductor power converter 11. With respect to the polarity of the primary winding 21 represented by the black circle “·”, the secondary winding 22 is wound with a wire so that the polarity is aligned in the direction shown in the figure and electrically connected to each component. . In single-phase transformer 12, the first winding 21, the other end the first external connection terminal T ₁ on the opposite side (i.e. the connection point P _1), 2 windings connected in series to each other 22 And the semiconductor power converter 11 are connected. The electrical connection relationship between the secondary winding 22 of the single-phase transformer 12 and the semiconductor power converter 11 is not limited to that shown in FIG. 17. For example, as shown in FIG. The line 22 may be electrically connected in series to any one of the plurality of semiconductor power converters 11 cascade-connected to each other. In the second embodiment of the present invention, the third ground terminal G ₃ is provided as a terminal opposite to the polarity of the first external connection terminal T ₁ .

One end of the mechanical circuit breaker 13 is connected to the connection point P ₁ so as to be in parallel with a set of the secondary winding 22 of the single-phase transformer 12 and the semiconductor power converter 11 connected in series with each other. It is connected the other end is the connection point P _3. Further, a connection point P ₃ on the opposite side of the mechanical circuit breaker 13 from the side connected to the primary winding 21 of the single-phase transformer 12 (that is, the side having the connection point P ₁ ) is connected to the second external and the connection terminal T _2. Circuit on the load side is connected to the second external connection terminal T _2. The configuration of the mechanical circuit breaker 13 is the same as that described in the first embodiment. Incidentally, in the second embodiment of the present invention, the second polarity external connection terminal T _2, but the fourth ground terminal G ₄ is provided as the opposite side of the terminal, and the third ground terminal G ₃ a No. ₄ ground terminal G ₄ has the same potential.

In the second embodiment of the present invention, by connecting the semiconductor power converter 11, the single-phase transformer 12, and the mechanical circuit breaker 13 as described above, the secondary of the single-phase transformer 12 connected in series with each other. A set of the winding 22 and the semiconductor power converter 11 and the mechanical circuit breaker 13 are connected in parallel. In addition to operating as a DC circuit breaker, the circuit breaker 2 can also operate as an AC circuit breaker. In this case, the terminal G ₃ is a terminal having a polarity opposite to that of the first external connection terminal T _1. The terminal G ₄ is a terminal having a polarity opposite to the polarity of the second external connection terminal T ₂ . As in the first embodiment, when the circuit breaker 2 operates as a DC breaker, the DCDC converter 31 in the semiconductor power converter 11 is configured by either a two-quadrant bidirectional DCDC converter or a four-quadrant bidirectional DCDC converter. However, when the circuit breaker 2 operates as an AC breaker, the DCDC converter 31 in the semiconductor power converter 11 is configured as a four-quadrant bidirectional DCDC converter.

In the example shown in FIG. 17, the side including the first external connection terminal T ₁ and the third ground terminal G ₃ is the power supply side, and the second external connection terminal T ₂ and the fourth ground terminal G ₄ However, as a modified example, the side formed by the first external connection terminal T ₁ and the third ground terminal G ₃ is the load side, and the second external connection terminal T ₂ and the fourth side side consisting of the ground terminal G ₄ may be a power supply side.

  As a modification of the above-described second embodiment of the present invention, the circuit breaker 2 includes a semiconductor power converter or a secondary winding in a set of a secondary winding and a semiconductor power converter connected in series to each other. An inductor for current control connected in series to the line may be further provided. FIG. 18 is a circuit diagram showing a modification of the circuit breaker according to the second embodiment of the present invention. As shown in FIG. 18, the circuit breaker 2 includes a semiconductor power converter 11 or a secondary winding in a set including the secondary winding 22 of the single-phase transformer 12 and the semiconductor power converter 11 connected in series. A current control inductor 14 connected in series to the line 22 is further provided. In the circuit breaker 2 described with reference to FIG. 17, the leakage inductance of the secondary winding 22 of the single-phase transformer 12 has a function equivalent to that of the current control inductor 14 in FIG. 18. The electrical connection relationship between the inductor 14, the secondary winding 22 and the semiconductor power converter 11 is not limited to that shown in FIG. 18. For example, as shown in FIG. 5, they are connected in series to each other. In the set of the secondary winding 22 and the semiconductor power converter 11, the inductor 14 is electrically connected in series to any one of the plurality of semiconductor power converters 11 connected in cascade. It only has to be connected.

Here, the DC voltage on the power supply side is represented by V _dc , the load voltage is represented by v _L , and the total voltage of the semiconductor power converters 11 on the N cascade-connected sides of the semiconductor power converters 11 is represented by v _HB . Further, the number of turns of the primary winding 21 of the single-phase transformer 12 is represented by N ₁ , the number of turns of the secondary winding 22 is represented by N ₂ , and the voltage appearing at both ends of the primary winding 21 is represented by v _N1 , secondary representing the voltage appearing across the winding 22 at v _N2. Moreover, the voltage of the DC capacitor connected in parallel for each of the N semiconductor power converters 11 is represented by v _C1 ,..., V _CN (where N is a natural number). The power supply current flowing from the first external connection terminal T ₁ to the circuit breaker 1 is i _S. In addition, the current flowing from the connection point P ₁ to the connection point P ₃ (that is, the current flowing through the mechanical circuit breaker 13) is expressed as “i _L ”. However, in order to simplify the description, the second embodiment is also used. The current “i _L ” flowing through the mechanical circuit breaker 13 is referred to as “load current”. For the voltage and current in the figure, the direction of the arrow is positive. The polarities of the primary winding 21 and the secondary winding 22 of the single-phase transformer 12 are represented by black circles “·”.

The control system of the circuit breaker 2 according to the second embodiment of the present invention has the same configuration as the control system of the circuit breaker 1 according to the first embodiment described with reference to FIG. Under this control system, the circuit breaker 2 according to the second embodiment of the present invention operates in the same manner as the operation flow of the circuit breaker 1 according to the first embodiment described with reference to FIG. That is, a ground fault or short circuit accident occurs on the load side at time t ₀ , and an overcurrent occurs. At time t ₁ , an opening command is given to the mechanical circuit breaker 13 and at the same time, each semiconductor power converter 11 The power conversion operation of the DCDC converter 31 is started. At the time t ₂ , the opening operation of the mechanical circuit breaker 13 is completed, and at the same time, the semiconductor switching elements S of all the semiconductor switches are turned off. At the time t ₃ , the power source current i _S and the converter current i _HB become zero and the current Blocking is complete. More details are as follows.

The normal operation of the circuit breaker 2 before time t ₀ when the short circuit accident occurs is the same as the operation of the circuit breaker 1 according to the first embodiment. That is, at the normal time, the mechanical circuit breaker 13 is turned on and power is supplied from the power source side to the load side. At this time, each diode D in the semiconductor power converter 11 functions, so that the semiconductor power converter 11 itself operates as a diode. In this case, the converter current i _HB is zero. That is, in a normal state before time t ₀ when a short circuit accident occurs, the power source current i _S flowing from the first external connection terminal T ₁ is the primary winding of the single-phase transformer 12 and the closed mechanical cutoff. It flows out from the second external connection terminal T ₂ via the vessel 13 in sequence. Therefore, at the normal time before the time t ₀ when the short circuit accident occurs, the power supply current i _S and the load current i _L are all the same. As in the first embodiment, the power supply side DC voltage V _dc and the DC capacitor voltage v _C (= v _C1 = v _CN ) in the semiconductor power converter 11 must satisfy the relationship of Equation 1.

The operation of the circuit breaker 2 immediately after the overcurrent detector 41 detects the occurrence of overcurrent at time t ₀ is the same as the operation of the circuit breaker 1 according to the first embodiment. At this time, the power supply current i _S and the load current i _L increase in a linear function with a slope of “V _dc / L _M ”.

The operation of the circuit breaker 2 between time t ₁ and time t ₂ is the same as the operation of the circuit breaker 1 according to the first embodiment. That is, by applying the generation principle of the power conversion command for controlling the converter current described with reference to FIG. 12, the control is performed so that the converter current i _HB matches the power source current i _S , and the load current i _{Let L} be zero.

The operation of the circuit breaker 2 when the opening operation of the mechanical circuit breaker 13 is completed at time t ₂ is the same as the operation of the circuit breaker 1 according to the first embodiment. That is, by turning off all the semiconductor switching elements S in the DCDC converter 31 in the semiconductor power converter 11, the energy stored in the single-phase transformer 12 and the inductor 14 passes through the feedback diode D in the semiconductor power converter 11. To the DC capacitor 32 and the non-linear resistor 33. The voltage equation and current relational expression established during this period are the same as those in the first embodiment.

DESCRIPTION OF SYMBOLS 1, 2 Circuit breaker 11 Semiconductor power converter 12 Single phase transformer 13 Mechanical circuit breaker 14 Inductor 21 Primary winding 22 Secondary winding 31 DCDC converter 32 Energy storage part 33 Nonlinear resistance 41 Overcurrent detection part 42 Control Unit 51 First command means 52 Second command means 53 Third command means D Feedback diode G ₁ First ground terminal G ₂ Second ground terminal G ₃ Third ground terminal G ₄ Fourth ground terminal S semiconductor switching element T ₁ first external connection terminal T ₂ second external connection terminal

Claims (10)

One or a plurality of semiconductor power converters cascade-connected to each other, and a semiconductor power converter that outputs a predetermined direct current by switching a semiconductor switch provided therein according to a command;
A primary winding having a first external connection terminal at one end; and a secondary winding connected in series with the semiconductor power converter; and the first external connection terminal of the primary winding; The other end on the opposite side is connected to a set of the secondary winding and the semiconductor power converter connected in series with each other, a single-phase transformer,
A set having the second external connection terminal at one end and the other end on the opposite side of the second external connection terminal is composed of the secondary winding and the semiconductor power converter connected in series with each other. A mechanical circuit breaker connected to a connection point between the primary winding and the primary winding, the mechanical circuit breaker opening in response to a command to interrupt the current path;
A circuit breaker comprising: The semiconductor power converter is
A DC current input from one of the first DC side and the second DC side is converted into a DC current of a desired magnitude and polarity by switching the semiconductor switch provided inside according to a command. A DCDC converter that outputs to the other side, and is capable of bidirectionally switching a DC current input / output direction between the first DC side and the second DC side;
Energy connected in parallel to the second DC side opposite to the first DC side to which the secondary winding or another semiconductor power converter different from the semiconductor power converter is connected A storage unit;
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. An overcurrent detection unit for detecting whether an overcurrent has occurred on the external wiring connected to the circuit breaker;
A controller for controlling an opening operation for the mechanical circuit breaker and a power conversion operation of the semiconductor power converter;
With
The controller is
First instruction means for outputting an opening command for instructing the mechanical circuit breaker to start an opening operation when the overcurrent detection unit detects an overcurrent;
The semiconductor power converter is caused to output a direct current that converges the current flowing through the mechanical circuit breaker to zero during the period from when the opening instruction is output until the opening operation of the mechanical circuit breaker is completed. Second command means for outputting a power conversion command;
Third 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 or 2.   A terminal on the side opposite to the side to which the primary winding is connected of the set of the secondary winding and the semiconductor power converter connected in series with each other is connected to the first external connection terminal and the second external connection terminal. The circuit breaker according to any one of claims 1 to 3, wherein the circuit breaker is a terminal having a polarity opposite to a polarity of the external connection terminal, or a first ground terminal and a second ground terminal. A set of the secondary winding and the semiconductor power converter connected in series with each other and the mechanical circuit breaker are connected in parallel,
The circuit breaker includes a terminal opposite to the polarity of the first external connection terminal or a third ground terminal, and a terminal opposite to the polarity of the second external connection terminal or a fourth ground terminal. The circuit breaker as described in any one of Claims 1-3 provided with these.   In the set consisting of the secondary winding and the semiconductor power converter connected in series with each other, the secondary winding is a semiconductor power of any one of the plurality of semiconductor power converters cascade-connected to each other. The circuit breaker as described in any one of Claims 1-5 connected in series with a converter.   The set of the secondary winding and the semiconductor power converter connected in series with each other further comprises an inductor connected in series to the semiconductor power converter or the secondary winding. The circuit breaker according to one item.   In the set including the secondary winding and the semiconductor power converter connected in series to each other, the inductor is connected to any one of the plurality of semiconductor power converters cascade-connected to each other. The circuit breaker according to claim 7 connected in series. The semiconductor switch includes a semiconductor switching element that passes a current in one direction when turned on,
A circuit breaker according to any one of claims 1 to 8, further comprising a feedback diode connected in antiparallel to the semiconductor switching element.   The mechanical circuit breaker includes 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. The circuit breaker according to any one of claims 1 to 9, wherein the movable contact is moved to the open circuit position to open a pole and interrupt the current path.

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