JP6456154B2 - Circuit breaker - Google Patents

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. 17 is a circuit diagram illustrating a general hybrid circuit breaker. For example, as shown in FIG. 17, 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 set to 2 [ms] or less. Can do.

B. Bachmann, G. Mauthe, E. Ruoss, HP Lips, “500kV wind-cooled high-voltage DC power supply Circuit of 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, in the present invention, a circuit breaker includes a first inductor having a first external connection terminal, one or a plurality of semiconductor power converters cascade-connected to each other, A current control inductor connected in series to the semiconductor power converter; and a first unit connected to a terminal opposite to the first external connection terminal of the first inductor. A second unit comprising one unit, one or a plurality of semiconductor power converters cascade-connected to each other, and a current control inductor connected in series to the semiconductor power converter, A second unit having one end connected to the first external connection terminal, a mechanical circuit breaker having one end connected to a connection point between the first inductor and the first unit, and a second unit of the first unit A second inductor connected between a terminal opposite to the side to which the inductor is connected and a terminal opposite to the side to which the first external connection terminal of the second unit is connected; .

  According to the first aspect of the present invention, the first inductor and the first unit set connected in series with each other, and the second inductor and the second unit set connected in series with each other, A terminal connected in parallel and opposite to the side to which the first inductor of the first unit is connected is a terminal having a polarity opposite to the polarity of the first external connection terminal or a first ground terminal, The terminal opposite to the side to which the first inductor and the first unit of the mechanical circuit breaker are connected is defined as a second external connection terminal, and the connection point between the second unit and the second inductor is defined as: A terminal having a polarity opposite to that of the second external connection terminal or a second ground terminal is used.

  Further, according to the second aspect of the present invention, a set of the first inductor and the second unit connected in series with each other, a set of the first unit and the second inductor connected in series with each other, and the machine The circuit breaker is connected in parallel, and the connection point between the first unit and the second inductor is the third external connection terminal, and the circuit breaker is opposite to the polarity of the first external connection terminal Terminal or third ground terminal, and a terminal or fourth ground terminal opposite to the polarity of the third external connection terminal.

  In the first and second aspects described above, in the first unit and the second unit, the current control inductor is one of a plurality of semiconductor power converters cascade-connected to each other. You may make it connect in series with a semiconductor power converter.

  In addition, the semiconductor power converter performs a switching operation of a semiconductor switch provided therein in accordance with a command, thereby causing a direct current input from one of the first DC side and the second DC side to have a desired magnitude. DCDC converter which converts the current into a direct current of the same polarity and outputs it to the other, and is capable of switching the input / output direction of the direct current bidirectionally between the first direct current side and the second direct current side Energy storage connected in parallel to the second DC side opposite to the first DC side to which the converter and the second inductor or another semiconductor power converter different from the semiconductor power converter are connected When the DC voltage applied to the energy storage unit is equal to or lower than a preset voltage, a predetermined resistance value is indicated. And a nonlinear resistor showing a remote low resistance, may have a.

  In addition, the circuit breaker includes an overcurrent detection unit 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 a semiconductor power converter. A control unit that controls the power conversion operation, and the control unit outputs an opening command that instructs the mechanical circuit breaker to start the opening operation when the overcurrent detection unit detects an overcurrent. A first command means, and a direct current that converges the current flowing through the mechanical circuit breaker to zero after the opening command is output until the opening operation of the mechanical circuit breaker is completed. And a second 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 circuit breaker is completed. And having.

  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 the example of arrangement | positioning of the inductor for current control in the circuit breaker by the 1st Example of this invention and the 2nd Example. It is a circuit diagram explaining the modification of the 1st inductor and the 2nd inductor in the circuit breaker by the 1st Example and 2nd Example of this 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 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 command for controlling the converter electric current in the semiconductor power converter in the circuit breaker by the 1st example of the present invention, and (A) flows through the 1st unit. It is a figure explaining the power conversion command for controlling a converter current, and (B) is a figure explaining the power conversion command for controlling the converter current which flows through the 2nd unit. 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 1st Example of this invention with the simulation circuit of FIG. 12 (A). 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.12 (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 illustrates a general circuit breaker of a hybrid system.

  The circuit breaker according to the present invention includes a first inductor, a first unit, a second unit, a mechanical circuit breaker, and a second inductor. The first inductor has a first external connection terminal. The first unit includes one or a plurality of semiconductor power converters cascade-connected to each other and a current control inductor connected in series to the semiconductor power converter. The terminal is connected to the terminal opposite to the first external connection terminal. The second unit includes one or a plurality of semiconductor power converters cascade-connected to each other, and a current control inductor connected in series to the semiconductor power converter, and the first external connection One end is connected to the terminal. The semiconductor power converters in the first unit and the second unit output a predetermined direct current by switching a semiconductor switch provided therein in accordance with a command. The mechanical circuit breaker is opened according to a command to interrupt a current path, and one end is connected to a connection point between the first inductor and the first unit. The second inductor includes a terminal on the side opposite to the side to which the first inductor of the first unit is connected, and a terminal on the side opposite to the side to which the first external connection terminal of the second unit is connected. And connected between. The first inductor and the second inductor are fault current limiting inductors. 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 first inductor 11, a first unit 12, a second unit 13, a mechanical circuit breaker 14, and a second inductor 15. A set of the first inductor 11 and the first unit 12 connected in series with each other and a set of the second inductor 15 and the second unit 13 connected in series with each other are connected in parallel. In the example shown in FIG. 1, the circuit breaker 1 is installed such that the first unit 12 and the second unit 13 are in parallel with respect to the applied DC power supply system. Is located on the power supply side and the mechanical circuit breaker 14 is located on the load side on the DC power supply system.

The first inductor 11 functioning as an accident current limiting inductor 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 first unit 12 includes one or a plurality of semiconductor power converters 21-1 cascade-connected to each other, and a current control inductor 22-1 connected in series to the semiconductor power converter 21-1. It consists of. The first unit 12 is connected to a connection point P ₁ on the opposite side of the first inductor 11 from the first external connection terminal T ₁ .

Semiconductor power converter 21-1 on the wiring branched from the connecting point P ₁ of the mechanical breaker 14 to be described later and the first inductor 11, is provided in a state that alone or a plurality are cascade-connected to each other . In the present specification, when there is one semiconductor power converter 21-1, the side to which the current control inductor 22-1 is connected is referred to as a "first DC side", and a plurality of semiconductor power converters are connected. When 21-1 is cascade-connected to each other, the side to which another semiconductor power converter 21-1 different from the semiconductor power converter 21-1 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 21-1 are cascade-connected to each other on the first DC side. A high breakdown voltage of the circuit breaker 1 can be easily realized only by appropriately adjusting the number of semiconductor power converters 21-1 connected in cascade.

  The semiconductor power converter 21-1 has a DCDC converter 31, an energy storage unit 32, and a non-linear resistance 33. By switching a semiconductor switch provided in the DCDC converter 31 according to a command, the semiconductor power converter 21-1 is operated. A predetermined direct current is output.

  The DCDC converter 31 in the semiconductor power converter 21-1 is configured as a bidirectional DCDC converter. As an example, in the example illustrated in FIG. 2, the DCDC converter 31 in the semiconductor power converter 21-1 is configured as a two-quadrant bidirectional DCDC converter (chopper cell). That is, the DCDC converter 31 in the semiconductor power converter 21-1 converts the direct current input from one of the first DC side and the second DC side to a desired magnitude and polarity by the switching operation of the semiconductor switch. The direct current input / output direction can be switched bi-directionally between the first direct current side and the second direct current side. By configuring the DCDC converter 31 in the semiconductor power converter 21-1 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, a four-quadrant bidirectional DCDC converter may be used instead of the two-quadrant bidirectional DCDC converter shown in FIG. 2 as the DCDC converter 31 in the semiconductor power converter 21-1. 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 21-1 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 21-1 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”). .) An element having a predetermined resistance value in the following cases and a resistance value lower than the predetermined resistance value in other cases. 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 stored energy of the first inductor 11 and the current control inductor 22-1, the DC capacitor 32 is charged. When the voltage gradually increases 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 first inductor 11 and the current control inductor 22-1 are thereafter clamped. The stored energy is consumed by the non-linear resistance 33. 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 second unit 13 includes one or a plurality of semiconductor power converters 21-2 cascade-connected to each other, and a current control inductor 22-2 connected in series to the semiconductor power converter 21-2. It consists of. One end of the second unit 13 is connected to the first external connection terminal T ₁ .

  As in the case of the semiconductor power converter 21-1, when the number of the semiconductor power converter 21-2 is one, the side to which the current control inductor 22-2 is connected is referred to as a "first DC side" When the semiconductor power converters 21-2 are cascade-connected to each other, the side to which the other semiconductor power converter 21-2 different from the semiconductor power converter 21-2 is connected is also the “first DC side”. Called. 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 21-2 are cascade-connected to each other on the first DC side. The high breakdown voltage of the circuit breaker 1 can be easily realized by simply adjusting the number of semiconductor power converters 21-2 connected in cascade.

  Similar to the semiconductor power converter 21-1, the semiconductor power converter 21-2 has a DCDC converter 31, an energy storage unit 32, and a non-linear resistance 33, and is a semiconductor switch provided inside the DCDC converter 31. Is switched according to the command to output a predetermined direct current.

  The DCDC converter 31 in the semiconductor power converter 21-2 is configured as a bidirectional DCDC converter. As an example, in the example illustrated in FIG. 2, the DCDC converter 31 in the semiconductor power converter 21-2 is configured as a two-quadrant bidirectional DCDC converter (chopper cell). That is, the DCDC converter 31 in the semiconductor power converter 21-2 converts the direct current input from one of the first DC side and the second DC side to a desired magnitude and polarity by the switching operation of the semiconductor switch. The direct current input / output direction can be switched bi-directionally between the first direct current side and the second direct current side. By configuring the DCDC converter 31 in the semiconductor power converter 21-2 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 four-quadrant bidirectional DCDC converter may be used as the DCDC converter 31 in the semiconductor power converter 21-2 instead of the two-quadrant bidirectional DCDC converter shown in FIG. 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 21-2 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 21-2 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”). .) An element having a predetermined resistance value in the following cases and a resistance value lower than the predetermined resistance value in other cases. 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 stored energy of a second inductor 15 and a current control inductor 22-2 described later, the DC capacitor 32 Is gradually increased to reach the operating voltage of the non-linear resistor 33, thereafter, the charging voltage of the DC capacitor 32 is clamped by the operating voltage of the non-linear resistor 33, and the second inductor 15 and the current control inductor 22 are clamped. −2 is consumed by the non-linear resistor 33. 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.

  FIG. 3 is a circuit diagram illustrating an arrangement example of the current control inductors in the circuit breakers according to the first and second embodiments of the present invention. In the first unit 12, the current control inductor 22-1 is connected in series to any one of the semiconductor power converters 21-1 among the plurality of semiconductor power converters 21-1 cascade-connected to each other. . Similarly, in the second unit 13, the current control inductor 22-2 is connected in series to any one of the plurality of semiconductor power converters 21-2 cascade-connected to each other. Connected. For example, as shown in FIGS. 3A and 3B, the current control inductors 22-1 and 22-2 are connected to the semiconductor power converters 21-1 and 21-2 located at both ends of the cascade connection. One of the semiconductor power converters 21-1 and 21-2 is installed on the side where the semiconductor power converters 21-1 and 21-2 are not connected. Further, for example, as shown in FIG. 3C, the current control inductors 22-1 and 22-2 are installed between the adjacent semiconductor power converters 21-1 and 21-2, respectively. When there are one semiconductor power converter 21-1 and 21-2, current control inductors 22-1 and 22-2 are simply connected in series to semiconductor power converters 21-1 and 21-2, respectively. Connected.

  In either case where a plurality of semiconductor power converters 21-1 and 21-2 are cascade-connected or only one semiconductor power converter 21-1 and 21-2, the current control inductor 22-1 and 22-2 are provided at any position on the same wiring as the plurality of semiconductor power converters 21-1 and 21-2 cascade-connected to each other. In the first embodiment of the present invention, a set of the first inductor 11 and the first unit 12 connected in series with each other and a set of the second inductor 15 and the second unit 13 connected in series with each other are provided. Connected in parallel.

One end of the mechanical circuit breaker 14 is connected to a connection point P ₁ between the first inductor 11 and the first unit 12. The mechanical circuit breaker 14 is connected to the second external connection terminal T ₂ on the side opposite to the side where the first inductor 11 and the first unit 12 are connected (that is, the side where the connection point P ₁ is present). Have The mechanical circuit breaker 14 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 14 include a vacuum circuit breaker, a gas circuit breaker, or an air blowing circuit breaker. Circuit on the load side is connected to the second external connection terminal T _2.

The second inductor 15 functioning as the fault current limiting inductor is a terminal P ₂ on the opposite side of the first unit 12 to the side to which the first inductor 11 is connected (that is, the side having the connection point P ₁ ). And the terminal P ₃ on the opposite side of the second unit 13 to the side to which the first external connection terminal T ₁ is connected.

  FIG. 4 is a circuit diagram illustrating a modified example of the first inductor and the second inductor in the circuit breaker according to the first and second embodiments of the present invention. In the first embodiment described above, the first inductor 11 and the second inductor 15 that function as the fault current limiting inductors are respectively configured as independent and independent uncoupled inductors. These may be configured as a coupled inductor 16 as shown in FIG. If the first inductor 11 and the second inductor 15 are configured as the coupled inductor 16 as shown in FIG. 4, the required number of iron cores is required as compared with the case where the first and second inductors 11 and 15 are configured separately. Can be reduced from two to one.

In the first embodiment of the present invention, the first inductor 11, the first unit 12, the second unit 13, the mechanical circuit breaker 14, and the second inductor 15 are connected by connecting the first inductor 11, the first unit 12, the second unit 13, as described above. The terminal P ₂ on the opposite side to the side to which the first inductor 11 of one unit 12 is connected (that is, the side having the connection point P ₁ ) is the first ground corresponding to the first external connection terminal T _1. the terminal G _1. Further, the connection point P ₃ between the second unit 13 and the second inductor 15 becomes the second ground terminal G ₂ corresponding to the second 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, The terminal P ₂ opposite to the side to which the connection point P ₁ is connected is defined as a terminal G ₁ having a polarity opposite to the polarity of the first external connection terminal T ₁ . The connection point P ₃ between the second unit 13 and the second inductor 15 is a terminal G ₂ having a polarity opposite to the polarity of the second external connection terminal T ₂ . When the circuit breaker 1 operates as a direct current circuit breaker, the DCDC converter 31 in the semiconductor power converters 21-1 and 2 may be configured with either a two-quadrant bidirectional DCDC converter or a four-quadrant bidirectional DCDC converter. However, when the circuit breaker 1 operates as an AC circuit breaker, the DCDC converter 31 in the semiconductor power converters 21-1 and 2 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.

Hereinafter, the power source side DC voltage is represented by V _dc , the load voltage is represented by v _L , and the voltage appearing at both ends of the mechanical circuit breaker 14 is represented by v _CB . The total voltage v ^a _HB semiconductor power converter 21-1 of N cascaded by the side of the semiconductor power converter 21-1, the N semiconductor power converter 21-2 cascaded by side semiconductor The total voltage of the power converter 21-2 is represented by v ^b _HB . Moreover, the voltage of the DC capacitor connected in parallel to each semiconductor power converter 21-1 is represented by v ^a _C1 ,..., V ^a _CN , respectively, and connected to each semiconductor power converter 21-2 in parallel. The voltage of the DC capacitor is represented by v ^b _C1 ,..., V ^b _CN (where N is a natural number). Further, the power source current flowing from the first external connection terminal T ₁ to the circuit breaker 1 is i _S , the current flowing from the first external connection terminal T ₁ to the connection point P ₁ is i ^a _S , and the connection point P ₁ From the connection point P ₁ to the semiconductor power converter 21-1 as the converter current i ^a _HB, and the current flowing from the first external connection terminal T ₂ to the second external connection terminal T ₂ as the load current i _{L. Let the} current flowing from ₁ to the connection point P ₃ be the converter current i ^b _HB, and the current flowing from the connection point P ₃ to the connection point P ₁ be i ^b _S. For the voltage and current in the figure, the direction of the arrow is positive.

  FIG. 5 is a block diagram illustrating a control system in the circuit breaker according to the first embodiment of the present invention. The circuit breaker 1 has an overcurrent detection unit 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 current i ^a _S flowing through the first inductor 11 increases. Therefore, the current i ^a _S is constantly monitored using a current detector (not shown), and the current i ^{a When “} _S” is larger than the rated current by a predetermined value, it is determined that “overcurrent has occurred”. 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 14 and the power conversion operation of the semiconductor power converters 21-1 and 21-2. 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 for commanding the mechanical circuit breaker 14 to start the opening operation; Semiconductor power converters 21-1 and 21 convert a DC current that converges the current flowing through the mechanical circuit breaker 14 to zero after the opening command is output and before the opening operation of the mechanical circuit breaker 14 is completed. The second command means 52 for outputting the power conversion command to be output to -2 and the semiconductor switch S in the semiconductor power converters 21-1 and 21-2 when the opening operation of the mechanical circuit breaker 14 is completed. And third command means 53 for outputting a command to turn off.

  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. 6 is a flowchart showing an operation flow of the circuit breaker according to the first embodiment of the present invention. 7 to 10 are diagrams showing equivalent circuits for explaining the operation of the circuit breaker according to the first embodiment of the present invention. Here, as an example, let us consider a case where an overcurrent occurs due to a ground fault or short circuit accident on the load side at time t ₀ .

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, the mechanical circuit breaker 14 is turned on under normal conditions, and power is supplied from the power supply side to the load side via the first external connection terminal T ₁ , the first inductor 11 and the mechanical circuit breaker 14. At this time, by the functioning of the diode D of the semiconductor power converter 21-1 and 21-2, a semiconductor power converter 21-1 and 21-2 itself operates as a diode, the converter current i ^a _HB and i ^b _HB is zero. 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 13 need to satisfy the relationship of Equation 1. N indicates the number of semiconductor power converters 21-1 or 21-2 (in other words, the number of DC capacitors).

As shown in FIG. 7, under normal conditions, the power supply current i _S , the load current i _L , the current i ^a _S flowing through the first inductor 11, and the current i ^b flowing through the second inductor 15 are determined according to Kirchhoff's current law. It is equal to _S, that is, the relational expression of Expression 2 is established.

In addition, since the voltage drop in the first inductor L ₁ is zero under normal conditions, the load voltage v _L and the power supply side DC voltage V _dc are equal, that is, “v _L = V _dc ”.

In step S102, the overcurrent detection unit 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 14 is ignored, the circuit equation shown in Equation 3 is established. In Equation 3, “i _S = i ^a _S = i ^b _S = i _L ” is assumed.

From Equation 3, i _S and i _L can be expressed as Equation 4. In Equation 4, the initial current of the power source current i _S and the load current i _L at time t ₀ is I ₀ .

As can be seen from Equation 4, the power supply current i _S and the load current i _L increase in a linear function with a slope of “V _dc / 2L ₁ ”. That is, if the inductor L ₁ of the first inductor 11 is increased, the current increase rate at the time of the accident can be suppressed. Since the power supply current i _S increases when a short circuit or ground fault occurs, the overcurrent detection unit 41 constantly monitors the power supply current i _S using a current detector (not shown), and the power supply current i _S is rated. When only a predetermined value larger than the current (for example, rated current 120%), it is determined that “overcurrent has occurred”. The time “t ₁ −t ₀ ” required from the occurrence of the accident to the judgment of the accident depends on the power source side DC voltage V _dc , the inductance L ₁ of the first inductor, the load, the reference current value, and the like.

  When the overcurrent detection unit 41 detects an overcurrent in step S102, in step S103, the first command means 51 of the control unit 42 instructs the mechanical circuit breaker 14 to start the opening operation. Output a command.

Even if a contact opening command is given to the mechanical circuit breaker 14, the mechanical circuit breaker 14 does not immediately complete the opening operation, but a delay time due to the mechanical structure of the mechanical circuit breaker 14 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 14 can interrupt the current path only at zero current, the load current i _L flowing through the mechanical circuit breaker 14 needs to be zero. Therefore, in step S104, the second command means 52 of the control unit 42 determines the current flowing through the mechanical circuit breaker 14 after the opening command is output until the opening operation of the mechanical circuit breaker 14 is completed. A power conversion command for causing the semiconductor power converters 21-1 and 21-2 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 converters 21-1 and 21-2 performs a PWM switching operation based on the received power conversion command. As a result, as shown in FIG. 9, the semiconductor power converter 21-1 is equivalent to operating as a control voltage source that outputs v ^a _HB , and the semiconductor power converter 21-2 outputs v ^b _HB . Equivalent to operating as a control voltage source. Therefore, in FIG. 9, circuit equations such as Expression 5 and Expression 6 are established.

In the first embodiment of the present invention, the control voltage source is realized by PI control as an example, and v ^a _HB is given by Equation 7 and v ^b _HB is given by Equation 8. In Equations 7 and 8, K _p denotes a proportional gain, K _I denotes integral gain, i a ^* _HB and i ^{b *} _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 Expressions 7 and 8, the first and second terms on the right side correspond to feedforward control, and the third term on the right side corresponds to feedback control (PI). Substituting Equation 7 into Equation 5 yields Equation 9 and substituting Equation 8 into Equation 6 yields Equation 10.

As shown in Equation 9, the converter current i ^a _HB responds to the command value i ^{a *} _HB with a second order delay, and as shown in Equation 10, the converter current i ^b _HB becomes the command value i ^{b *} _HB. Responds with a second order delay. At this time, the converter current command value i ^{a *} _HB is set to i ^a _S so that the converter current i ^a _HB matches the current i ^a _S flowing through the first inductor 11, and the converter current command value If control is performed to set the converter current i ^b _HB to the current i ^b _S flowing through the second inductor 15 by setting i ^{b *} _HB to i ^b _S , the load current i _L is reduced to zero by Kirchhoff's current law. can do. The time required to make the load current i _L zero (ie, the time required to match the converter currents i ^a _HB and i ^b _HB to the currents i ^a _S and i ^b _S , respectively) is the semiconductor power converter 21. -1 and 21-2 carrier frequency, equivalent switching frequency, and digital control 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.

  Based on the above, the generation principle of the power conversion command based on Equation 7 and Equation 8 will be described as follows. FIG. 11 is a control block diagram for explaining a power conversion command for controlling the converter current in the semiconductor power converter in the circuit breaker according to the first embodiment of the present invention. FIG. It is a figure explaining the power conversion instruction | command for controlling the converter electric current which flows through the unit of this, and (B) is a figure explaining the electric power conversion instruction | command for controlling the converter electric current which flows through a 2nd unit. In the control of the converter current, feedback control and feedforward control are used in combination.

As shown in FIG. 11A, the converter current i ^a _HB flowing through the first unit 12 is detected by a current detector (not shown) in the block B1-a related to feedback control. current i ^a _HB a current detector deviations by relative difference between the first current flowing through the inductor 11 i ^a _S detected by (not shown) to apply a PI control (i ^a _HB -i ^a _S) Suppress. On the other hand, in the block B2-a related to the feedforward control, the sum v ^a _f of the voltage v ^a _HB appearing at both ends of the semiconductor power converter 21-1 and the voltage appearing at both ends of the current control inductor 22-1 is used. Thus, the current controllability is improved. v ^a _f is calculated using the DC power supply side voltage V _dc , the current i ^a _S flowing through the first inductor 11, and the inductance L ₁ of the first inductor 11, or a voltage sensor (not shown) is used. It can be obtained by using and detecting directly. The output of the block B1-a and the output of the block B3-a are added to generate ^a power conversion command va ^* _j for each semiconductor power converter 21-1. Power conversion command v ^{a *} _j for each semiconductor power converter 21-1, after normalizing the DC capacitor voltage at block B4 _j -a v ^a _Cj (although, j = 1 to N), common PWM The modulation method (triangular wave comparison) is applied to the semiconductor switching element S of the semiconductor switch in each semiconductor power converter 21-1.

Similarly, the converter current i ^b _HB flowing through the second unit 13 is detected by a current detector (not shown) in the block B1-b related to feedback control, as shown in FIG. 11B. By applying PI control to the difference between the converter current i ^b _HB and the current i ^b _S flowing through the second inductor 15 detected by the current detector (not shown), the deviation (i ^b _HB −i ^b _S ) is suppressed. On the other hand, in the block B2-b related to the feedforward control, the sum v ^b _f of the voltage v ^b _HB appearing at both ends of the semiconductor power converter 21-2 and the voltage appearing at both ends of the current control inductor 22-2 is used. Thus, the current controllability is improved. v ^b _f is calculated using the DC power supply side voltage V _dc , the current i ^b _S flowing through the second inductor 15, and the inductance L ₁ of the second inductor 15, or a voltage sensor (not shown) is used. It can be obtained by using and detecting directly. The output of the block B1-b and the output of the block B3-b are added to generate a power conversion command v ^{b *} _j for each semiconductor power converter 21-2. The power conversion command v ^{b *} _j for each semiconductor power converter 21-2 is normalized with the DC capacitor voltage v ^b _Cj (where j = 1 to N) in block B4 _j -b, and then a general PWM. A modulation method (triangular wave comparison) is applied to the semiconductor switching element S of the semiconductor switch in each semiconductor power converter 21-2.

When the DCDC converter 31 in the semiconductor power converters 21-1 and 2 is configured as a two-quadrant bidirectional DCDC converter, the “phase shift” is performed by shifting the initial phase of the triangular wave carrier used for PWM control by 360 ° / N. If the “PWM method” is applied to the control of the DCDC converter 31 of each of the semiconductor power converters 21-1 and 21-2, 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 converters 21-1 and 2 is configured as a four-quadrant bidirectional DCDC converter, the “phase shift PWM that shifts the initial phase of the triangular wave carrier used for PWM control by 180 ° / N” If the “method” is applied to control of the DCDC converters 31 of the semiconductor power converters 21-1 and 21-2, the equivalent switching frequency can be increased. Specifically, assuming that the carrier frequency is f _C , the equivalent switching frequency is 2Nf _C. By setting the equivalent switching frequency high, it is possible to improve the current control system and reduce the inductance of the current control inductors 22-1 and 22-2.

  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 converters 21-1 and 21-2 in the circuit breaker 1 according to the first embodiment of the present invention perform the PWM operation only when an accident occurs, an increase in switching loss is not a problem. When the semiconductor power converters 21-1 and 21-2 use, for example, 3.3 [kV] / 1500 [A] SiC power modules (SiC MOSFET and SiC SBD (Schottky Barrier Diode)), the PWM modulation uses a number [ The carrier frequency of [kHz] is assumed to be improved, and the current controllability can be expected to be improved.The current in a high voltage application in which the number of cascades of the semiconductor power converters 21-1 and 21-2 increases when the same carrier frequency is assumed. Controllability is improved.

  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. 6, in step S <b> 105, the mechanical circuit breaker 14 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 14 can be operated only at zero current. However, the processing for reducing the current flowing through the mechanical circuit breaker 14 in step S104 to zero is performed after the opening command is output. It is executed in a time sufficiently shorter than the time required to complete the 14 opening operations.

When the opening operation of the mechanical breaker 14 is completed (in this case the time t ₂ is), in step S106, the third command means 53 in the control unit 42, a semiconductor power converter 21-1 and 21- A command to turn off all the semiconductor switches S in 2 is output. The time “t ₂ −t ₁ ” required from the start of the power conversion operation of the semiconductor power converters 21-1 and 21-2 to the completion of the opening operation of the mechanical circuit breaker 14 is open to the mechanical circuit breaker 14 It is equal to the delay time from when the command is given until the mechanical circuit breaker 14 actually completes the opening operation, and the time is, for example, 2 [ms].

The semiconductor device S in the semiconductor power converters 21-1 and 21-2 is turned off upon receiving the off command from the third command means 53 in the control unit 42, and the power conversion operation is completed. Thereby, as shown in FIG. 10, only each diode D in the semiconductor power converter 13 functions. At this time, the accumulated energy of the first inductor 11 and the current control inductor 22-1 is released to the DC capacitor 32 and the non-linear resistor 33 via the feedback diode D in the semiconductor power converter 21-1. Similarly, the stored energy of the second inductor 15 and the current control inductor 22-2 is released to the DC capacitor 32 and the non-linear resistor 33 via the feedback diode D in the semiconductor power converter 21-2. Since they are connected in parallel to the DC capacitor 32 and a nonlinear resistor 33 in the semiconductor power converter 21-1, after turn-off of the semiconductor switching elements S of the semiconductor switch (i.e. the time t ₂ after the period), the first the stored energy of the inductor 11 and the current control inductor 22-1, DC capacitor 32 is charged voltage v _c after gradually increased, is clamped in the operating voltage V _R of the non-linear resistor 33. After the DC capacitor 32 is charged to the operating voltage, the stored energy is consumed by the non-linear resistor 33. Similarly, since they are connected in parallel to the DC capacitor 32 and a nonlinear resistor 33 of the semiconductor power converter 21-2, after turn-off of the semiconductor switching elements S of the semiconductor switch (i.e. the time t ₂ after the period), the stored energy of the second inductor 15 and the current control inductor 22-2, DC capacitor 32 is charged voltage v _c after gradually increased, is clamped in the operating voltage V _R of the non-linear 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 energy stored in the first inductor 11 and the current control inductor 22-1, the circuit equation shown in Expression 11 holds.

From Equation 11, the voltage of the DC capacitor 32 v _C and the current flowing through the first inductor ^{_{11 i a S (= i a}} HB) can be calculated by solving the second order constant coefficient linear differential equation.

After the DC capacitor 32 is charged to the operating voltage, the circuit equation shown in Equation 12 is established. In Equation 12, the operating voltage of the nonlinear resistor 33 is V _R.

From Equation 12, the current i ^a _S flowing through the first inductor 11 and the converter current i ^a _HB can be calculated by solving a first-order constant coefficient linear differential equation.

  Similarly, until the DC capacitor 32 is charged to the operating voltage of the nonlinear resistor 33 by the energy stored in the second inductor 15 and the current control inductor 22-2, the circuit equation shown in Expression 13 is established.

From Equation 13, the voltage v _C of the DC capacitor 32 and the current i ^b _S (= i ^b _HB ) flowing through the second inductor 15 can be calculated by solving the second-order constant coefficient linear differential equation.

After the DC capacitor 32 is charged to the operating voltage, the circuit equation shown in Equation 14 is established. In Equation 14, the operating voltage of the nonlinear resistor 33 is V _R.

From Equation 14, the current i ^b _S flowing through the second inductor 15 and the converter current i ^b _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. 12 is a circuit diagram used for the simulation of the circuit breaker according to the first embodiment of the present invention. FIG. 12A 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. 12B, the regenerative load is simulated by a direct current source. FIG. 13 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 inductance L ₁ of the first and second inductors (accident current limiting inductor) was set to 5 [mH] so that the current increase rate V _dc / L ₁ was 3.0 [kA / ms]. 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 of the semiconductor power converters 21-1 and 21-2 is 10, and the carrier The frequency f _C was 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 Equation 15.

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 14 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. 14 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. Consider a case where a short circuit accident occurs at the closest end of the circuit breaker 1 at time t ₀ when an RL load (7.5 [MW]) is connected to the circuit breaker 1.

The semiconductor power converters 21-1 and 21-2 before the time t ₀ when the short-circuit accident occurs are caused by the function of each diode D in the semiconductor power converters 21-1 and 21-2. -1 and 21-2 themselves operate as diodes. In this case, the load current i _L , the current i ^a _S flowing through the first inductor 11 and the current i ^b _S flowing through the second inductor 15 are all 500 [A], and the converter current is determined by Kirchhoff's current law. i ^a _HB and i ^b _HB are both 0 [A]. Therefore, the DC side power supply voltage V _dc , the converter voltage v ^a _HB, and the converter voltage v ^b _HB are equal, and all are 15 [kV]. During this time, the voltage (V _dc / N) of the DC capacitor 32 in each of the semiconductor power converters 21-1 and 21-2 is charged to 1.5 [kV].

When a short circuit accident occurs at time t ₀ , the power source current i _S , the current i ^a _S flowing through the first inductor 11, the current i ^b _S flowing through the second inductor 15, and the load current i _L are 1.5 [kA / ms] (= V _dc / 2L ₁ ). From Equations 3, 5, and 6 and the relational expression “i ^a _HB = i ^b _HB = 0”, the converter voltages v ^a _HB and v ^b _HB are reduced to V _dc / 2.

At time t ₁ , an opening command is given to the mechanical circuit breaker 14. At the same time, a power conversion command for causing the semiconductor power converters 21-1 and 21-2 to output a direct current that converges the current flowing through the mechanical circuit breaker 14 to zero is output. Thereby, the semiconductor switching element S of the semiconductor switch in the semiconductor power converters 21-1 and 21-2 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 14 is set to 1.5 [ms]. As shown in FIG. 14, at 0.35 [ms] after application of current control, the load current i _L becomes zero, the current i ^a _S flowing through the first inductor 11 and the converter current i ^a _HB become equal, and Since the current i ^b _S flowing through the second inductor 15 and the converter current i ^b _HB are equal, the mechanical circuit breaker 14 can cut off the current path. According to Kirchhoff's current law, “i _s = i ^a _S + i ^b _S ”, the current increase rate of the power source current i _{S is} the current increase rate of the current i ^a _S flowing through the first inductor 11 (or the second rate). Twice the current i ^b _S flowing through the inductor 15 (= 3.0 [kA / ms]). Since converter power p _HB is always positive, the voltage v ^a _C1 of the DC capacitor 32 increases and is eventually clamped by 2 [kV] is the operating voltage V _R of the non-linear resistor 33.

Opening operation of the mechanical breaker 14 is completed at time t _2, the turning off the semiconductor switching element S of all the semiconductor switches of the semiconductor power converter 21-1 and 21-2 at the same time. The current i ^a _S flowing through the first inductor 11, the current i ^b _S flowing through the second inductor 15, the converter current i ^a _HB and the converter current i ^b _HB decrease linearly and become zero at time t ₃ . It becomes. According to this simulation result, it can be seen that the required time “t ₃ −t ₀ ” from the occurrence of a short-circuit accident to the completion of current interruption is 4.5 [ms], and the circuit breaker 1 can realize high-speed interruption.

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. Consider a case where a short circuit accident occurs at the closest end of the circuit breaker 1 at time t ₀ when a regenerative load (7.5 [MW]) is connected to the circuit breaker 1.

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, 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 5.2 [ms], and the circuit breaker 1 can realize high-speed interruption.

  Next, a second embodiment of the present invention will be described. FIG. 16 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 installed so that the first unit 12 and the second unit 13 are in parallel to the applied DC power supply system. The circuit breaker 2 according to the embodiment is installed such that the first unit 12 and the second unit 13 are in series with respect to the DC power supply system. As in the first embodiment, the circuit breaker 2 according to the second embodiment of the present invention includes a first inductor 11, a first unit 12, a second unit 13, a mechanical circuit breaker 14, A second inductor 15. A set of first inductor 11 and second unit 13 connected in series with each other, a set of first unit 12 and second inductor 15 connected in series with each other, and mechanical breaker 14 are connected in parallel. Connected. Each configuration will be described below.

The first inductor 11 functioning as an accident current limiting inductor 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 . 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 . The configuration of the first inductor 11 is the same as that described in the first embodiment.

As in the case of the first embodiment, the first unit 12 includes one or a plurality of semiconductor power converters 21-1 connected in cascade with each other, and the semiconductor power converter 21-1 in series. The current control inductor 22-1 is connected. The first unit 12 is connected to a terminal Q ₁ of the first inductor 11 opposite to the first external connection terminal T ₁ . That is, the semiconductor power converter 21-1 is provided on the wiring branched from the connection point Q ₁ between the first inductor 11 and the mechanical circuit breaker 14, either alone or in a state in which a plurality are cascade-connected to each other. . In the second embodiment of the present invention, the first unit 12, opposite to the first inductor 11 and the first side unit 12 is connected (i.e., the side where the connecting point Q ₁₎ The terminal is referred to as a third external connection terminal T ₃ . Circuit on the load side is connected to the third external connection terminal T _3. The fourth ground terminal G ₄ is provided as a terminal opposite to the polarity of the third external connection terminal T _{3. In} the second embodiment of the present invention, the third ground terminal G ₃ and the fourth ground terminal G ₄ are provided. The ground terminal G ₄ has the same potential. The configuration of the first unit 12 is the same as that described in the first embodiment.

The second unit 13 includes one or a plurality of semiconductor power converters 21-2 cascade-connected to each other, and a current control inductor 22-2 connected in series to the semiconductor power converter 21-2. It consists of. One end of the second unit 13 is connected to the first external connection terminal T ₁ . The configuration of the second unit 13 is the same as that described in the first embodiment.

  As in the case of the first embodiment, when there is one semiconductor power converter 21-1, the side to which the current control inductor 22-1 is connected is referred to as a "first DC side", and a plurality of semiconductors When the power converters 21-1 are cascade-connected to each other, the side to which another semiconductor power converter 21-1 different from the semiconductor power converter 21-1 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”. The same applies to the semiconductor power converter 21-2.

  As an example, FIG. 16 shows a case where a plurality (N, where N is an integer of 2 or more) semiconductor power converters 21-1 and 21-2 are cascade-connected to each other on the first DC side. ing. High voltage resistance of the circuit breaker 1 can be easily realized only by appropriately adjusting the number of semiconductor power converters 21-1 and 21-2 connected in cascade. The configurations of the semiconductor power converters 21-1 and 21-2 are the same as those described in the first embodiment. However, when the energy storage unit 32 in the semiconductor power converters 21-1 and 21-2 is a DC capacitor, an initial charging circuit (not shown) needs to be provided separately, unlike the case of the first embodiment. There is.

  As in the case of the first embodiment, in the first unit 12, the current control inductor 22-1 is a semiconductor power conversion of any one of the plurality of semiconductor power converters 21-1 cascade-connected to each other. In the second unit 13, the current control inductor 22-2 is connected in series to the capacitor 21-1, and the semiconductor power conversion of any one of the plurality of semiconductor power converters 21-2 cascade-connected to each other. Connected in series to the device 21-2. The arrangement example of the current control inductors 22-1 and 22-2 is as described with reference to FIG. In addition, when the number of the semiconductor power converters 21-1 and 21-2 is one, the current control inductors 22-1 and 22-2 are simply the semiconductor power converter 21 as in the case of the first embodiment. -1 and 21-2 are connected in series, respectively. That is, as in the case of the first embodiment, when a plurality of semiconductor power converters 21-1 and 21-2 are cascade-connected and when there is one semiconductor power converter 21-1 and 21-2, either Even in this case, the current control inductors 22-1 and 22-2 are located at any position on the same wiring as the plurality of semiconductor power converters 21-1 and 21-2 cascade-connected to each other. Will be provided.

One end of the mechanical circuit breaker 14 is connected to a connection point Q ₁ between the first inductor 11 and the first unit 12. Further, the second connection point Q ₂ of the mechanical circuit breaker 14 opposite to the side to which the first inductor 11 and the first unit 12 are connected (that is, the side having the connection point Q ₁ ) A terminal of the unit 13 opposite to the side to which the first external connection terminal T ₁ is connected is connected. The configuration of the mechanical circuit breaker 14 is the same as that described in the first embodiment.

The second inductor 15 that functions as the fault current limiting inductor is a third inductor 12 on the opposite side of the first unit 12 to the side to which the first inductor 11 is connected (that is, the side having the connection point Q ₁ ). an external connection terminal T ₃ of, the second unit 13, the opposite side of the terminal Q ₂ is a first side on which the external connection terminal T ₁ is connected, is connected between the. The configuration of the second inductor 15 is the same as that described in the first embodiment.

  In the second embodiment described above, the first inductor 11 and the second inductor 15 each functioning as an accident current limiting inductor are configured as independent and independent uncoupled inductors. These may be configured as a coupled inductor 16 as shown in FIG. If the first inductor 11 and the second inductor 15 are configured as the coupled inductor 16 as shown in FIG. 4, the required number of iron cores is required as compared with the case where the first and second inductors 11 and 15 are configured separately. Can be reduced from two to one.

In the second embodiment of the present invention, the first inductor 11, the first unit 12, the second unit 13, the mechanical circuit breaker 14, and the second inductor 15 are connected to each other as described above. A set of the first inductor 11 and the second unit 13 connected in series, a set of the first unit 12 and the second inductor 15 connected in series with each other, and the mechanical circuit breaker 14 are connected in parallel. It becomes the composition which was done. The circuit breaker 2 can operate as an AC circuit breaker in addition to operating as a DC circuit breaker. In this case, the terminal G ₃ has a polarity opposite to the polarity 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 .

In the example shown in FIG. 16, the side including the first external connection terminal T ₁ and the third ground terminal G ₃ is the power supply side, and the third external connection terminal T ₃ 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 third external connection terminal T ₃ and the fourth side side consisting of the ground terminal G ₄ may be a power supply side.

Here, the power source side DC voltage is represented by V _dc , the load voltage is represented by v _L , and the voltage appearing at both ends of the mechanical circuit breaker 14 is represented by v _CB . The total voltage v ^a _HB semiconductor power converter 21-1 of N cascaded by the side of the semiconductor power converter 21-1, the N semiconductor power converter 21-2 cascaded by side semiconductor The total voltage of the power converter 21-2 is represented by v ^b _HB . Moreover, the voltage of the DC capacitor connected in parallel to each semiconductor power converter 21-1 is represented by v ^a _C1 ,..., V ^a _CN , respectively, and connected to each semiconductor power converter 21-2 in parallel. The voltage of the DC capacitor is represented by v ^b _C1 ,..., V ^b _CN (where N is a natural number). Further, the power source current flowing from the first external connection terminal T ₁ to the circuit breaker 2 is i _S , the current flowing from the first external connection terminal T ₁ to the connection point Q ₁ is i ^a _S , and the connection point Q ₁ the current flowing to the semiconductor power converter 21-1 and the converter current i ^a _HB, the current flowing through the first external connection terminal T ₁ to the connection point Q ₂ and the converter current i ^b _HB, from the connection point Q ₂ from The current flowing through the third external connection terminal T ₃ is i ^b _S. In addition, the current flowing from the connection point Q ₁ to the connection point Q ₃ (that is, the current flowing through the mechanical circuit breaker 14) 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 14 is referred to as “load current”. Further, as described above, the third ground terminal G ₃ and the fourth ground terminal G ₄ have the same potential. For the voltage and current in the figure, the direction of the arrow is positive.

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 at the load side at time t ₀ and an overcurrent is generated. At time t ₁ , an opening command is given to the mechanical circuit breaker 14 and at the same time, each semiconductor power converter 21-1. And the power conversion operation | movement of the DCDC converter 31 in 21-2 is started. At the time t ₂ , the opening operation of the mechanical circuit breaker 14 is completed and 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 currents i ^a _HB and i ^b are turned off. _HB becomes zero and current interruption is completed. 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 14 is turned on and power is supplied from the power source side to the load side. At this time, the diodes D in the semiconductor power converters 21-1 and 21-2 function, so that the semiconductor power converters 21-1 and 21-2 themselves operate as diodes. In this case, the converter currents i ^a _HB and i ^b _HB are zero. That is, in a normal state before time t ₀ when a short circuit accident occurs, the current flowing from the first external connection terminal T ₁ is the first inductor 11, the closed mechanical circuit breaker 14, and the second inductor 15. the via sequentially flows from the third external connection terminal T _3. Therefore, at the normal time before the time t ₀ when the short circuit accident occurs, the power source current i _S , the load current i _L , the current i ^a _S flowing through the first inductor 11, and the current i flowing through the second inductor 15 are detected. ^b _S is all the same. In other words, the current i _L flowing through the mechanical circuit breaker 14 at the normal time before the time t ₀ when the short circuit accident occurs becomes the “load current” as described above. As in the first embodiment, the power source side DC voltage V _dc and the DC capacitor voltage v _C (= v _C1 = v _CN ) in the semiconductor power converters 21-1 and 21-2 satisfy the relationship of Equation 1. There is a need to.

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 source current i _S , the current i ^a _S flowing through the first inductor 11, the current i ^b _S flowing through the second inductor 15, and the load current i _L are “V _dc / 2L ₁ ” as shown in Equation 3. It increases in a linear function with the slope of.

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. 11, the converter current i ^a _HB matches the current i ^a _S flowing through the first inductor 11. The converter current i ^b _HB is controlled to coincide with the current i ^b _S flowing through the second inductor 15 so that the load current i _L becomes zero.

The operation of the circuit breaker 2 when the opening operation of the mechanical circuit breaker 12 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 converters 21-1 and 21-2, the accumulated energy of the first inductor 11 and the current control inductor 22-1 is changed to the semiconductor. In the power converter 21-1, the energy stored in the second inductor 15 and the current control inductor 22-2 is discharged to the DC capacitor 32 and the non-linear resistor 33 via the feedback diode D. The semiconductor power converter 21-2 Inside, it is discharged to the DC capacitor 32 and the non-linear resistance 33 via the feedback diode D. 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 1st inductor 12 1st unit 13 2nd unit 14 Mechanical circuit breaker 15 2nd inductor 21-1, 21-2 Semiconductor power converter 22-1, 22-2 Current Control inductor 31 DCDC converter 32 Energy storage unit 33 Non-linear resistance 41 Overcurrent detection unit 42 Control unit 51 First command means 52 Second command means 53 Third command means G ₁ First ground terminal G ₂ Second Ground terminal G3 _third ground terminal G4 _fourth ground terminal T1 _first external connection terminal T2 _second external connection terminal T3 _third external connection terminal

Claims (7)

A first inductor having a first external connection terminal;
A first unit comprising one or a plurality of semiconductor power converters cascade-connected to each other and a current control inductor connected in series to the semiconductor power converter, wherein the first unit A first unit connected to a terminal opposite to the first external connection terminal of the inductor;
A second unit comprising one or a plurality of semiconductor power converters cascade-connected to each other and a current control inductor connected in series to the semiconductor power converter, wherein the first unit A second unit having one end connected to the external connection terminal;
A mechanical circuit breaker having one end connected to a connection point between the first inductor and the first unit;
A terminal of the first unit opposite to the side to which the first inductor is connected; a terminal of the second unit opposite to the side to which the first external connection terminal is connected; A second inductor connected between,
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;
Equipped with a,
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;
Circuit breaker according to claim Rukoto to have a. The set of the first inductor and the first unit connected in series with each other and the set of the second inductor and the second unit connected in series with each other are connected in parallel,
The terminal on the opposite side to the side to which the first inductor of the first unit is connected is a terminal having a polarity opposite to the polarity of the first external connection terminal or a first ground terminal,
A terminal on the opposite side to the side to which the first inductor and the first unit of the mechanical circuit breaker are connected is a second external connection terminal,
2. The circuit breaker according to claim 1, wherein a connection point between the second unit and the second inductor is a terminal having a polarity opposite to a polarity of the second external connection terminal or a second ground terminal. . The set of the first inductor and the second unit connected in series with each other, the set of the first unit and the second inductor connected in series with each other, and the mechanical circuit breaker in parallel Connected,
A connection point between the first unit and the second inductor is a third external connection terminal,
The circuit breaker includes 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 third external connection terminal. A circuit breaker according to claim 1.   In the first unit and the second unit, the current control inductor is connected in series to any one of the plurality of semiconductor power converters cascade-connected to each other. Item 4. The circuit breaker according to any one of Items 1 to 3. 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 second inductor 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, comprising: The semiconductor switch is
A semiconductor switching element that allows current to flow in one direction when on,
A feedback diode connected in antiparallel to the semiconductor switching element;
The circuit breaker according to any one of claims 1 to 5 . 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 6 , wherein the movable contact is moved to the open circuit position to open a pole to interrupt a current path.

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