JP2021136696A - Surge absorption circuit and current-limiting circuit - Google Patents

Abstract

To prevent a failure of commutation to a surge absorption circuit in a cutoff.SOLUTION: A surge absorption circuit (11) has a configuration in which a first switch element (Sw1) to which a second diode (D2) is connected in parallel between a first terminal (t1) and a second terminal (t2), a second switch element (Sw2) to which a first diode (D1) is connected in parallel, and a surge suppressor (Ab) are connected in series, and the first diode and the second diode are arranged in an opposite direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surge absorption circuit and a current limiting circuit using the same.

In DC power transmission, a current limiting reactor is used to suppress the rate of increase of the main current flowing through the main circuit when a failure occurs. However, when the main circuit is cut off by the circuit breaker, the inductive energy accumulated by the current limiting reactor is released, which increases the burden on the contacts of the circuit breaker. Therefore, Patent Document 1 proposes a circuit configuration in which a surge absorber is connected in parallel to a current limiting reactor in order to process the accumulated inductive energy.

In the circuit configuration of the present prior art, a switch element is provided in series with the surge absorber in order to prevent current from flowing into the surge absorber during normal operation. The switch element is normally turned off, but when the circuit breaker is cut off, the switch element needs to be turned on so that the inductive energy can be processed by the surge absorber. Therefore, when the occurrence of a failure in the DC transmission line is detected, the switch element is controlled so as to turn on.

JP-A-2015-33187

As described above, in the prior art of Patent Document 1, the switch element must be turned on based on the failure detection to perform commutation within a short period of time after the failure occurs until the circuit breaker shuts off. .. However, commutation within such a short period of time due to failure detection may fail. Then, the surge current due to the inductive energy accumulated in the current limiting reactor may destroy the contacts of the circuit breaker.

Further, in order to strengthen the protection of the DC power transmission system, if an attempt is made to cut off by a circuit breaker after a failure occurs more quickly, there is a problem that commutation failure is more likely to occur. One aspect of the present invention has been made in view of the above problems, and it is not necessary to operate a switch based on the failure detection of a DC transmission line, and a surge that fails to commutate to a surge absorption circuit at the time of interruption is suppressed. The purpose is to realize an absorption circuit.

In order to solve the above problems, the surge absorption circuit of one aspect of the present invention includes a first terminal and a second terminal as connection terminals to the outside, and a first switch element, a second switch element, and a first diode. A second diode and a surge absorber are provided, and the first switch element, the second switch element, and the surge absorber are connected in series between the first terminal and the second terminal, and the first diode is provided. Is connected in parallel to the second switch element in a direction that conducts the current flowing from the first terminal to the second terminal, and the second diode flows from the second terminal to the first terminal. A configuration is provided in which the first switch element is connected in parallel in a direction in which the current to be conducted is conducted.

In order to solve the above problems, another aspect of the surge absorption circuit of the present invention includes a first terminal and a second terminal as connection terminals to the outside, and a first switch element, a second switch element, and a first terminal. A partial circuit including a diode, a second diode, and a surge absorber in which the first switch element and the first diode are connected in series, and a partial circuit in which the second switch element and the second diode are connected in series. The parallel connection circuit with and the surge absorber are connected in series between the first terminal and the second terminal, and the first diode moves from the first terminal to the second terminal. The second diode is arranged in a direction for conducting a flowing current, and the second diode is arranged in a direction for conducting a current flowing through from the second terminal to the first terminal.

According to each aspect of the present invention, it is possible to realize a surge absorption circuit that does not require a switch operation based on a failure detection of a DC transmission line and suppresses a failure of commutation to the surge absorption circuit at the time of interruption.

It is a circuit diagram which shows the surge absorption circuit which concerns on Embodiment 1 of this invention, and the DC power transmission system to which it was applied. It is a figure for demonstrating the operation of the surge absorption circuit which concerns on Embodiment 1 of this invention, and shows the state in a normal state. It is a figure for demonstrating the operation of the surge absorption circuit which concerns on Embodiment 1 of this invention, and shows the state at the time of interruption. The dotted line indicates the path of the surge current flowing through the surge absorption circuit. It is a circuit diagram which shows the surge absorption circuit which concerns on Embodiment 2 of this invention, and the DC power transmission system to which it is applied. It is a figure for demonstrating the operation of the surge absorption circuit which concerns on Embodiment 2 of this invention, and shows the state in a normal state. It is a figure for demonstrating the operation of the surge absorption circuit which concerns on Embodiment 2 of this invention, and shows the state at the time of interruption. The dotted line indicates the path of the surge current flowing through the surge absorption circuit.

[Embodiment 1]
Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a diagram showing a circuit configuration of the surge absorption circuit 11 according to the first embodiment and a DC power transmission system 1 to which the surge absorption circuit 11 is applied.

As shown in FIG. 1, a circuit breaker Cb and a current limiting reactor L are provided on the main circuit 50 of the DC power transmission system 1. Similar to the conventional technique, a surge absorber Ac is connected in parallel to the circuit breaker Cb in order to prevent breakage between contacts at the time of circuit breaker. The current limiting reactor L is provided to reduce the rate of increase of the main current I flowing through the main circuit 50 when a failure such as a short circuit accident occurs in the DC power transmission system 1.

<Structure of surge absorption circuit>
The surge absorption circuit 11 according to the first embodiment is a circuit connected in parallel to the current limiting reactor L on the main circuit 50. The surge absorption circuit 11 includes a pair of external connection terminals, a first terminal t1 and a second terminal t2. The first terminal t1 is connected to one terminal of the current limiting reactor L, and the second terminal t2 is connected to the other terminal of the current limiting reactor L. The circuit that combines the surge absorption circuit 11 and the current limiting reactor L is referred to as the current limiting circuit 10.

The surge absorption circuit 11 includes a first switch element Sw1, a second switch element Sw2, a first diode D1, a second diode D2, and a surge absorber Ab. Further, the surge absorption circuit 11 includes a switch control circuit 12 that controls the first switch element Sw1 and the second switch element Sw2.

The connection of each of the above elements inside the surge absorption circuit 11 is as follows. The first switch element Sw1, the second switch element Sw2, and the surge absorber Ab are connected in series between the first terminal t1 and the second terminal t2. In the specific circuit example shown in FIG. 1, the first switch element Sw1, the second switch element Sw2, and the surge absorber Ab are arranged in this order from the first terminal t1 side, but the arrangement order may be arbitrary.

The first diode D1 is connected in parallel to the second switch element Sw2. The direction of the first diode D1 is such that the current flowing through the surge absorption circuit 11 can be conducted from the first terminal t1 to the second terminal t2. That is, the first diode D1 is arranged so that the first terminal t1 side is the anode and the second terminal t2 side is the cathode.

The second diode D2 is connected in parallel to the first switch element Sw1. The direction of the second diode D2 is such that the current flowing through the surge absorption circuit 11 can be conducted from the second terminal t2 to the first terminal t1. That is, the second diode D2 is arranged so that the second terminal t2 side is the anode and the first terminal t1 side is the cathode.

Any element can be applied to the first switch element Sw1 and the second switch element Sw2 as long as it is a circuit element whose on / off can be controlled by the switch control circuit 12. For example, MOSFET (Metal Oxide Semiconductor field-effect transistor) and other FETs can be applied. Alternatively, semiconductor switch elements such as IGBTs (Insulated Gate Bipolar Transistors), bipolar transistors, and other transistors can be applied.

Further, the present invention is not limited to the semiconductor switch element, and for example, a mechanical relay or other mechanical switch element may be applied. The first switch element Sw1 and the second switch element Sw2 are not limited to switch elements that can be energized in both directions, and switch elements that can be energized only in one direction can also be applied.

The first switch element Sw1 connected in parallel to the second diode D2 is arranged so that a current opposite to that of the second diode D2 can be energized. That is, when a switch element capable of energizing only in one direction is applied as the first switch element Sw1, the first switch element Sw1 transmits a current flowing through the surge absorption circuit 11 from the first terminal t1 to the second terminal t2. It is arranged so that it can conduct electricity.

The second switch element Sw2 arranged in parallel with the first diode D1 is arranged so that a current in the opposite direction to that of the first diode D1 can be energized. That is, when a switch element that can be energized in only one direction is applied as the second switch element Sw2, the second switch element Sw2 transfers a current flowing through the surge absorption circuit 11 from the second terminal t2 to the first terminal t1. It is arranged so that it can conduct electricity.

In the specific circuit example of FIG. 1, an IGBT, which is a switch element capable of energizing in one direction, is applied as the first switch element Sw1 and the second switch element Sw2. Therefore, according to the above-mentioned arrangement rule, the first switch element Sw1 which is an IGBT is arranged so that the collector is on the first terminal t1 side and the emitter is on the second terminal side. Further, the second switch element Sw2, which is an IGBT, is arranged so that the collector is on the second terminal t2 side and the emitter is on the first terminal side.

The circuit in which the IGBT and the diode are arranged as in the relationship between the first switch element Sw1 and the second diode D2 described above is commercially available as an IGBT product to which a so-called freewheel diode is added in a packaged manner. Has been done. Alternatively, a product called a reverse conduction IGBT in which a freewheel diode is built in a semiconductor chip of the IGBT is also commercially available. The arrangement of the parallel connection circuit of the second switch element Sw2 and the first diode D1 is the same as the arrangement of the parallel connection circuit of the first switch element Sw1 and the second diode D2. Therefore, if any of these products is used, the surge absorption circuit 11 can be easily manufactured.

<Operation of surge absorption circuit>
The switch control circuit 12 controls on / off of the first switch element Sw1 and the second switch element Sw2 according to the direction of the main current I flowing through the main circuit 50 of the DC power transmission system 1. Therefore, the main circuit 50 may be provided with a current detector 51, and the switch control circuit 12 may execute the above control with reference to the direction of the main current detected by the current detector 51. The current detector 51 may be, for example, a galvanometer or an ammeter that can detect the direction of the current.

In the switch control circuit 12, when the direction of the main current I is from the connection point of the first terminal t1 to the main circuit 50 to the connection point of the second terminal t2, the first switch element Sw1 is turned off and the second switch element Sw1 is turned off. The switch element Sw2 is controlled to be turned on. FIG. 2 is a diagram for showing the operation of the surge absorption circuit 11 in which the on / off status of each switch element at this time is added to the circuit diagram. FIG. 2 also shows the direction of the main current I. In this case, the second diode D2 connected in parallel to the first switch element Sw1 is not forward biased. Therefore, the second diode D2 and the first switch element Sw1 that is off prevent the main current I from flowing into the surge absorption circuit 11.

When the circuit breaker Cb is cut off in this state, the current limiting reactor L tries to maintain the main current I, and the connection point of the second terminal t2 has a higher potential than the connection point of the first terminal t1. Then, since the second switch element Sw2 is on, the second diode D2 is forward-biased. The surge current shown by the dotted line in FIG. 3 flows through the surge absorption circuit 11 from the second terminal t2 to the first terminal t1. At this time, the surge current inside the surge absorption circuit 11 passes through the surge absorber Ab, the second switch element Sw2 that is on, and the second diode D2.

On the other hand, in the switch control circuit 12, the direction of the main current I is opposite to that in the case of FIG. 2, that is, the direction from the connection point of the second terminal t2 to the main circuit 50 to the connection point of the first terminal t1. Then, the first switch element Sw1 is controlled to be turned on, and the second switch element Sw2 is controlled to be turned off. In this case, the first diode D1 connected in parallel to the second switch element Sw2 is not forward biased. Therefore, the second switch element Sw2 and the first diode D1 prevent the main current I from flowing into the surge absorption circuit 11.

When the circuit breaker Cb is cut off in this state, the current limiting reactor L tries to maintain the main current I, and the connection point of the first terminal t1 has a higher potential than the connection point of the second terminal t2. Then, since the first switch element Sw1 is on, the first diode D1 is forward-biased. The surge current flows through the surge absorption circuit 11 from the first terminal t1 to the second terminal t2. At this time, the surge current inside the surge absorption circuit 11 passes through the surge absorber Ab, the first switch element Sw1 that is on, and the first diode D1.

In the prior art of Patent Document 1, it is necessary to perform the switch operation of the switch element of the surge absorption circuit within a short period of time from the detection of the failure to the interruption by the circuit breaker. However, in the surge absorption circuit 11 according to the first embodiment, the switch operation of each switch element is performed regardless of the failure detection, and as a result, the surge absorption circuit 11 normally causes the main current I flowing through the main circuit. Does not affect.

When a failure occurs, the surge absorption circuit 11 has already completed the switch operation required for commutation. Further, regardless of the direction of the main current I, at least a part of the inductive energy accumulated by the current limiting reactor L is processed by the surge absorber Ab when the circuit breaker Cb of the main circuit 50 is cut off. NS. Therefore, the load on the contacts at the time of interruption by the circuit breaker Cb is reduced, and the possibility of contact breakage is reduced.

In the surge absorption circuit 11, there is no commutation failure due to a failure detection failure as in the prior art, and the switch operation is limited to a short period from the occurrence of an accident in the DC transmission line to the interruption. There is no commutation failure. Therefore, in the surge absorption circuit 11, the possibility of failure of commutation to the surge absorption circuit 11 at the time of interruption is reduced.

Regarding the method of controlling the on / off of the first switch element Sw1 and the second switch element Sw2 when the main current I flowing through the main circuit 50 continues to be 0, refer to the operation method of the entire DC power transmission system 1. Depending on the situation, an appropriate method can be appropriately selected. For example, the previous state may be maintained until the direction of the main current I is determined next. Alternatively, both the first switch element Sw1 and the second switch element Sw2 may be controlled to be off. Alternatively, both the first switch element Sw1 and the second switch element Sw2 may be controlled to be turned on.

[Embodiment 2]
Other embodiments of the present invention will be described below. For convenience of explanation, the same reference numerals will be added to the members having the same functions as the members described in the above embodiment, and the description will not be repeated.

FIG. 4 is a diagram showing a circuit configuration of the surge absorption circuit 21 according to the second embodiment and a DC power transmission system 2 to which the surge absorption circuit 21 is applied. The DC power transmission system 2 of the second embodiment has the same configuration as the DC power transmission system 1 of the first embodiment, except that the circuit configuration of the surge absorption circuit 21 is different from the surge absorption circuit 11 according to the first embodiment. The circuit that combines the surge absorption circuit 21 and the current limiting reactor L is referred to as the current limiting circuit 20.

<Structure of surge absorption circuit>
Similar to the surge absorption circuit 11 of the first embodiment, the surge absorption circuit 21 according to the second embodiment also includes a first terminal t1 and a second terminal t2 which are connection terminals to the outside. Further, the surge absorption circuit 21 includes a first switch element Sw1, a second switch element Sw2, a first diode D1, a second diode D2, a surge absorber Ab, and a switch control circuit 12, according to the first embodiment. This is the same as the surge absorption circuit 11. The types of switch elements applicable to the first switch element Sw1 and the second switch element Sw2 are the same as in the case of the first embodiment.

However, in the surge absorption circuit 21, the connection between the first switch element Sw1, the second switch element Sw2, the first diode D1, the second diode D2, and the surge absorber Ab is the circuit of the surge absorption circuit 11 of the first embodiment. It is different from the configuration. The connection of each element inside the surge absorption circuit 21 is as follows.

The parallel connection circuit of the partial circuit in which the first switch element Sw1 and the first diode D1 are connected in series, the partial circuit in which the second switch element Sw2 and the second diode D2 are connected in series, and the surge absorber Ab are , The first terminal t1 and the second terminal t2 are connected in series. The positional relationship between the parallel connection circuit and the surge absorber Ab may be on the first terminal t1 side.

Further, the positional relationship between the first switch element Sw1 and the first diode D1 in the partial circuit in which the first switch element Sw1 and the first diode D1 are connected in series may be on the first terminal t1 side. .. The positional relationship between the second switch element Sw2 and the second diode D2 in the partial circuit in which the second switch element Sw2 and the second diode D2 are connected in series may be on the first terminal t1 side.

The orientation of each element of the first switch element Sw1, the second switch element Sw2, the first diode D1, and the second diode D2 in the surge absorption circuit 21 with reference to the first terminal t1 and the second terminal t2 is an embodiment. It is the same as the case of 1. That is, the first switch element Sw1 and the first diode D1 are arranged in such a direction that the current flowing through the surge absorption circuit 21 can be conducted from the first terminal t1 to the second terminal t2. Further, the second switch element Sw2 and the second diode D2 are arranged in such a direction that the current flowing through the surge absorption circuit 21 can be conducted from the second terminal t2 to the first terminal t1.

<Operation of surge absorption circuit>
The method of controlling the on / off of the first switch element Sw1 and the second switch element Sw2 by the switch control circuit 12 is the same as that of the first embodiment.

FIG. 5 is a diagram for showing the operation of the surge absorption circuit 21 when the direction of the main current I is the direction from the connection point of the first terminal t1 to the main circuit 50 to the connection point of the second terminal t2. be. FIG. 5 shows the on / off status of each switch element and the direction of the main current I. In this case, the second diode D2 connected in series with the on second switch element Sw2 is not forward biased. Therefore, the second diode D2 and the first switch element Sw1 that is off prevent the main current I from flowing into the surge absorption circuit 21.

When the circuit breaker Cb is cut off in this state, the current limiting reactor L tries to maintain the main current I, and the connection point of the second terminal t2 becomes higher potential than the connection point of the first terminal t1 to the main circuit 50. .. Then, since the second switch element Sw2 is on, the second diode D2 is forward-biased. The surge current shown by the dotted line in FIG. 6 flows through the surge absorption circuit 21 from the second terminal t2 to the first terminal t1. The surge current inside the surge absorption circuit 21 passes through the surge absorber Ab, the second switch element Sw2 that is on, and the second diode D2.

On the other hand, when the direction of the main current I is opposite to that in FIG. 5, that is, the direction from the connection point of the second terminal t2 to the main circuit 50 to the connection point of the first terminal t1, it is on. The first diode D1 connected in series with the 1-switch element Sw1 is not forward biased. Therefore, the first diode D1 and the second switch element Sw2 that is off prevent the main current I from flowing into the surge absorption circuit 21.

When the circuit breaker Cb is cut off in this state, the current limiting reactor L tries to maintain the main current I, and the connection point of the first terminal t1 has a higher potential than the connection point of the second terminal t2. Then, since the first switch element Sw1 is on, the first diode D1 is forward-biased. The surge current flows through the surge absorption circuit 21 from the first terminal t1 to the second terminal t2. The surge current inside the surge absorption circuit 21 passes through the surge absorber Ab, the first switch element Sw1 that is on, and the first diode D1.

Also in the second embodiment, the same effect as that of the first embodiment is obtained with respect to the operation of the surge absorption circuit 21.

〔summary〕
The surge absorption circuit according to the first aspect of the present invention includes a first terminal and a second terminal as connection terminals to the outside, a first switch element, a second switch element, a first diode, a second diode, and a surge absorber. The first switch element, the second switch element, and the surge absorber are connected in series between the first terminal and the second terminal, and the first diode is transferred from the first terminal to the first terminal. The second diode is connected in parallel to the second switch element in a direction that conducts a current flowing through the two terminals, and the second diode is connected in a direction that conducts a current flowing through the second terminal to the first terminal. It has a configuration in which it is connected in parallel to the first switch element.

The surge absorption circuit according to the second aspect of the present invention includes a first terminal and a second terminal as connection terminals to the outside, a first switch element, a second switch element, a first diode, a second diode, and a surge absorber. , A parallel connection circuit of a partial circuit in which the first switch element and the first diode are connected in series, a partial circuit in which the second switch element and the second diode are connected in series, and the surge absorber. Are connected in series between the first terminal and the second terminal, and the first diode is arranged so as to conduct a current flowing through the first terminal to the second terminal. The second diode has a configuration in which the current flowing from the second terminal to the first terminal is arranged so as to conduct the current.

In the surge absorption circuit of the third aspect of the present invention, in the first or second aspect, each of the first switch element and the second switch element is an element capable of conducting a current in one direction when it is turned on, and the first switch element. The 1-switch element is arranged so as to conduct a current flowing from the first terminal to the second terminal, and the second switch element conducts a current flowing from the second terminal to the first terminal. It may have a configuration which is arranged in the direction of the current.

Aspect 4 of the present invention is a surge absorption circuit for connecting to a current limiting reactor provided on a main circuit of DC power transmission in any one of the above aspects 1 to 3.

The surge absorption circuit according to the fifth aspect of the present invention further includes a switch control circuit for controlling on / off of the first switch element and the second switch element in the fourth aspect, and the switch control circuit is the main main switch element. When the direction of the main current flowing through the circuit is the direction from the connection point of the first terminal to the connection point of the second terminal, the first switch element is turned off and the second switch element is controlled to be on. When the direction of the main current flowing through the main circuit is the direction from the connection point of the second terminal to the connection point of the first terminal, the first switch element is turned on and the second switch element is turned off. It may have a configuration to be used.

Aspect 6 of the present invention is a current limiting circuit including the surge absorbing circuit according to any one of the above aspects 1 to 5 and a current limiting reactor connected between the first terminal and the second terminal.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

1, 2 DC power transmission system 10, 20 Current limiting circuit L Limited current reactor 11, 21 Surge absorption circuit t1 1st terminal t2 2nd terminal D1 1st diode D2 2nd diode Sw1 1st switch element Sw2 2nd switch element Ab surge Absorber 12 Switch control circuit 50 Main circuit 51 Current detector Cb circuit breaker Ac Surge absorber

Claims (6)

The first and second terminals as connection terminals to the outside,
Equipped with a first switch element, a second switch element, a first diode, a second diode, and a surge absorber.
The first switch element, the second switch element, and the surge absorber are connected in series between the first terminal and the second terminal.
The first diode is connected in parallel to the second switch element in a direction that conducts a current flowing from the first terminal to the second terminal.
A surge absorbing circuit, characterized in that the second diode is connected in parallel to the first switch element in a direction in which a current flowing through the second terminal to the first terminal is conducted. The first and second terminals as connection terminals to the outside,
Equipped with a first switch element, a second switch element, a first diode, a second diode, and a surge absorber.
A parallel connection circuit of a partial circuit in which the first switch element and the first diode are connected in series, and a partial circuit in which the second switch element and the second diode are connected in series,
With the surge absorber,
Connected in series between the first terminal and the second terminal,
The first diode is arranged so as to conduct a current flowing through the first terminal to the second terminal.
The surge absorption circuit is characterized in that the second diode is arranged in a direction in which a current flowing through the second terminal to the first terminal is conducted. Each of the first switch element and the second switch element is an element capable of conducting a current in one direction when it is turned on.
The first switch element is arranged so as to conduct a current flowing through the first terminal to the second terminal.
The surge absorption circuit according to claim 1 or 2, wherein the second switch element is arranged so as to conduct a current flowing through the second terminal to the first terminal. The surge absorption circuit according to any one of claims 1 to 3, for connecting to a current limiting reactor provided on a main circuit of DC power transmission. A switch control circuit for controlling on / off of the first switch element and the second switch element is further provided.
The switch control circuit
When the direction of the main current flowing through the main circuit is the direction from the connection point of the first terminal to the connection point of the second terminal, the first switch element is turned off and the second switch element is turned on. death,
When the direction of the main current flowing through the main circuit is the direction from the connection point of the second terminal to the connection point of the first terminal, the first switch element is turned on and the second switch element is turned off. The surge absorption circuit according to claim 4, wherein the surge absorption circuit is provided. The surge absorption circuit according to any one of claims 1 to 5.
A current limiting reactor connected between the first terminal and the second terminal,
A current limiting circuit characterized by being provided with.

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