JPH07220583A - Permanent current switch - Google Patents

Abstract

PURPOSE:To provide a permanent current switch which has high speed responsiveness, and in which, in addition, resistance in a disconnection condition can be sufficiently high. CONSTITUTION:A permanent current switch 11 comprises a superconductive switch 111 for performing transition between a superconductive condition and a conductive condition by magnetism or heat, and a saturation reactor 112 connected in series. As switch disconnection is started, a control winding 23 of the superconductive switch 111 is excited to set the superconductive switch 111 in the conductive condition. As a current is decreased to be under a saturation current of a saturation core, impedance of the saturation reactor 112 is increased quickly to set the current at the switch 111 almost at zero. Apparant resistance in a switch disconnection condition can thus be set large to reduce heat generation quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a persistent current switch, and more particularly to a persistent current switch capable of increasing resistance in an off state.

[0002]

2. Description of the Related Art Recently, in an electric vehicle or a hybrid vehicle using liquid hydrogen as a fuel, a superconducting energy storage device (hereinafter referred to as SMES) to which a superconducting coil is applied.
[Superconducting Magnetic Energy Storage]. Is applied as an auxiliary power source for energy regeneration and energy leveling.

A so-called permanent current switch is indispensable for changing the operating mode of the SMES from the charge mode to the energy storage mode or from the energy storage mode to the discharge mode. This persistent current switch must have the following properties. (1) The power loss of the persistent current switch is small when the persistent current switch is turned on, that is, when the SMES is operated in the energy storage mode. (2) The open resistance of the persistent current switch is high when the persistent current switch is off, that is, when the SMES is operated in the charge or discharge mode.

This is because if the open resistance of the permanent current switch is small, Joule heat is generated and the same problem as in (1) occurs. (3) It has a high-speed response. When SMES is used for electric or hybrid vehicles, it is in discharge mode when the vehicle is accelerating or traveling uphill, and in charging mode when it is decelerating or traveling downhill.
In addition, it is necessary to switch to the storage mode frequently and quickly when traveling on a flat ground at a constant speed.

At present, there are (a) semiconductor switches, (b) mechanical switches, and (c) superconducting switches that are considered to be applied as permanent current switches. (A) Although the semiconductor switch has the properties of (2) and (3), the resistance when the switch is turned on is large, so the heat generated by the switch during operation in the storage mode cannot be ignored. For example, when GTO is used as a semiconductor switch, heat loss of 1 Kw or more occurs when a maximum current of 1000 amperes is passed.

Further, since the semiconductor switch and the superconducting coil cannot be placed together in the liquid hydrogen, the connection between the semiconductor switch and the superconducting coil becomes redundant, and the increase of Joule heat cannot be prevented. (B) The mechanical switch completely satisfies the property (2) because the resistance can be made infinite when off.

However, the mechanical switch has a residual contact resistance of about 10 μΩ when turned on, so that the stored power is consumed as heat. If the so-called zero current interruption is not performed when shifting to the off state, an arc may be generated, an oxide film may be formed on the contact surface, and the contact resistance at the time of on may increase.
That is, the property of (1) is not satisfied. (C) A superconducting switch is a persistent current switch that utilizes the fact that it is possible to make a transition from the superconducting state to the normal conducting state by applying heat or a magnetic field and from the normal conducting state to the superconducting state by removing the heat or magnetic field. , (1) is satisfied.

However, the thermal superconducting switch is (3)
Not only does it not have the above property, but it also has the problem of being accompanied by heat loss. Further, although the magnetic superconducting switch has the property (3), it requires a strong magnetic field source and inevitably becomes large in scale. Therefore, a transformer-type superconducting switch has been proposed for the purpose of reducing heat loss and downsizing (Japanese Patent Laid-Open No. 4-335582).
See the bulletin).

[0009]

However, even the superconducting switch according to the above proposal does not have the property (2). That is, it is common that a stabilizer is mixed in the superconducting material in order to maintain the superconducting state in the superconducting wire, and the resistance in the permanent current switch-off state cannot be sufficiently high. There remains the problem of loss.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a persistent current switch having not only a high-speed response but also a sufficiently high resistance in an off state.

[0011]

A persistent current switch according to a first aspect of the present invention is a superconducting switch for switching an on / off state by changing a conducting state of a superconducting wire from a superconducting state to a normal conducting state or from a normal conducting state to a superconducting state. A switch and a saturable core whose saturation start current is sufficiently smaller than the breaking current obtained by dividing the normal voltage applied to the superconducting switch by the breaking resistance which is the resistance when the superconducting switch is in the breaking state; And a saturable reactor which is connected to the superconducting switch in series and which is composed of a primary winding of a superconducting wire wound around a saturable core and connected in series to the superconducting switch.

The persistent current switch according to the second invention is
The saturable reactor has a secondary winding of a superconducting wire wound around a saturable core.When the superconducting switch is connected, a magnetic flux is applied in a direction that saturates the saturable core, and the secondary winding can be applied at the start of disconnection. It further comprises a pulsed power supply that generates a current pulse that applies a magnetic flux in a direction that makes the saturated iron core unsaturated.

The persistent current switch according to the third invention is
A superconducting switch that switches the superconducting wire from the superconducting state to the normal conducting state or from the normal conducting state to the superconducting state to switch the on / off state, and the superconducting wire wound around the iron core and the iron core and connected in series to the superconducting switch. A transformer that consists of a primary winding and a secondary winding that is wound around an iron core and that is connected in series to the superconducting switch, and the direction opposite to the current that flows through the superconducting switch in the primary winding of the transformer while the superconducting switch is shut off. And a control unit for applying a voltage for generating the current to the secondary winding of the transformer.

The persistent current switch according to the fourth invention is
A transformer that is composed of a semiconductor switch, a primary winding of a superconducting wire that is wound around the iron core and connected in series to the semiconductor switch, and a secondary winding that is wound around the iron core, and that is connected in series to the superconducting switch. A control unit for applying to the secondary winding of the transformer a voltage that induces a current in the primary winding of the transformer in the opposite direction to the current flowing through the superconducting switch while the superconducting switch is shut off.

[0015]

In the persistent current switch according to the first aspect of the present invention, the current flowing through the persistent current switch is reduced at the start of the interruption of the persistent current switch, and the saturable reactor is made into an unsaturated state to increase the impedance, thereby performing the charging mode operation. The current flowing through the permanent current switch is low.

In the permanent current switch according to the second aspect of the invention, the current pulse is applied to the secondary winding of the saturable reactor to control the unsaturated state or the saturated state of the saturable reactor to thereby charge or discharge the saturable reactor. The current flowing through the permanent current switch during mode operation is small. In the persistent current switch according to the third aspect of the present invention, a bias that generates a current in the opposite direction to the current flowing through the permanent current switch is applied via the secondary winding of the transformer, and the current flowing through the superconducting switch when the superconducting switch is cut off. Is reduced.

In the permanent current switch according to the fourth aspect of the present invention, a bias is applied through the secondary winding of the transformer to generate a current in the opposite direction to the current flowing through the permanent current switch. The cut-off voltage applied to is reduced.

[0018]

1 is a block diagram of an SMES to which the persistent current switch according to the first and second aspects of the invention is applied, showing the structure of a superconducting energy storage device mounted on an electric vehicle or a hybrid vehicle. The persistent current switch 11 has a configuration in which a superconducting switch 111 and a saturable reactor 112 are connected in series, and the superconducting coil 1 for energy storage is provided.
2 connected in parallel.

The superconducting coil 12 for energy storage is connected to a vehicle-mounted power source 14 via an energy converter 13.
The on-vehicle power supply 14 is connected to the input end of the PWM control device 16 via the capacitor 15 connected in parallel, and the output end of the PWM control device 16 is connected to the load 17 which is, for example, a motor.

When the energy storage superconducting coil 12 is operating in the charging mode, the permanent current switch 11 is turned off, and the electric power generated by the vehicle-mounted power source 14 is charged in the energy storage superconducting coil 12. When the energy storage superconducting coil 12 is operating in the discharge mode, the permanent current switch 11 is turned off, and the electric power stored in the energy storage superconducting coil 12 is supplied to the load 17 via the PWM control device 16. To be done.

When the energy storage superconducting coil 12 is operating in the storage mode, the permanent current switch 11 is turned on, and the closed circuit composed of the energy storage superconducting coil 12 and the persistent current switch 11 is turned on. Circulate. FIG. 2 is a cross-sectional view of the superconducting switch 111 used in the first and second inventions, in which a superconducting winding 22 constituted by a superconducting wire is wound around an iron core 21 in a non-inductive winding.

When the superconducting switch is of the magnetic type, the control winding 23 of the normal conducting wire is provided inside and outside the superconducting winding 22.
Are arranged. When the superconducting switch is of a thermal type, a heater is provided instead of the control winding 23. FIG. 3 is a cross-sectional view of the saturable reactor 112 used in the first and second inventions, in which a primary winding 32 composed of a superconducting wire is wound around a saturable iron core 31.

The superconducting winding 2 of the superconducting switch 111
2 and the primary winding 32 of the saturable reactor 112 are connected in series. The control unit 18 is installed to control the on / off states of the semiconductor switches 131 and 132 diagonally arranged among the bridge-connected semiconductor switches that form the energy converter 13, and is provided during operation in the storage mode. The semiconductor switch 131 is maintained in the ON state and the semiconductor switch 132 is maintained in the OFF state.

When the permanent current switch 11 is cut off in order to operate the energy storage superconducting coil 12 in the charging mode, the control section 18 excites the control winding 23 of the superconducting switch 111 to bring the superconducting switch 111 into the superconducting state. To normal conduction state. Then, the current flowing through the permanent current switch 11 sharply decreases.

FIG. 4 is a magnetization characteristic diagram of the saturable iron core 31 of the saturable reactor 112, wherein the vertical axis represents magnetic flux and the horizontal axis represents current. That is, since the saturable iron core 31 has a square-shaped magnetization characteristic, when the current decreases below the saturation current, the saturable iron core 3
1 shifts to the unsaturated state, and the impedance of the inductance of the saturable reactor 112 rapidly increases.

Further, by turning on the semiconductor switch 132 and applying a voltage opposite to the current applied during the operation in the storage mode to the permanent current switch, the resistance at the off time can be further increased. FIG. 5 is a diagram for explaining the operation of the permanent current switch according to the first aspect of the present invention, in which the vertical axis represents the current flowing from above in the energy storage superconducting coil 12, the current flowing in the permanent current switch, the power consumption in the permanent current switch, The on / off state of the semiconductor switch 131 and the on / off state of the semiconductor switch 132 represent time on the horizontal axis.

When shifting from the storage mode to the charging mode at time t ₁ , the semiconductor switch 132 is turned on and a reverse voltage is applied to the permanent current switch 11. Then, the impedance of the saturable reactor 112 rapidly increases, and the impedance of the persistent current switch 11 in the cutoff state becomes high. Therefore, the current flowing through the permanent current switch 11 during charging can be significantly reduced as compared with the case of only the superconducting switch 111, and the power consumption of the superconducting switch can be reduced. The alternate long and short dash line shows the case where the persistent current switch 11 is composed of only the superconducting switch 111.

However, the first invention cannot solve the following problems. 1. When shifting from the charging mode to the storage mode in time t _2, the saturable core 31 also saturable reactor 112 superconducting switch 111 as a superconducting state from the normal conducting state are in a high impedance state because it is unsaturated. Therefore, the electric current stored in the energy-conducting superconducting coil 12 is consumed in the closed circuit including the diode 133 and the semiconductor switch 131 until the saturable iron core 31 of the saturable reactor 112 is saturated. 2. When transitioning from the storage mode to the discharge mode at time t ₃ , the saturable core 31 of the saturable reactor 112 is
Cannot be made into an unsaturated state, so that the power consumption in the cutoff state of the persistent current switch 11 cannot be reduced.

In order to solve the above problems, in the persistent current switch according to the second invention, the secondary winding 33 of the superconducting wire is wound around the saturable reactor 112, and the control unit 18
To apply a pulse current to the secondary winding 33 to control the saturated state or the unsaturated state of the saturable iron core 31. FIG. 6 is a diagram for explaining the operation of the permanent current switch according to the second aspect of the invention, showing the current applied to the secondary winding 33 of the saturable reactor 112 in addition to the parameters shown in FIG.

That is, time t₁Charging from storage mode at
When switching to mode and time t ₃Storage at
When switching from the discharge mode to the discharge mode, the secondary winding 33
Direction to move saturable iron core 31 from saturated to unsaturated state
A current pulse is applied to. Time t₂In charging mode
From storage to storage mode and at time t_FourAt
When changing from discharge mode to storage mode,
Connect the saturable iron core 31 to the wire 33 from the unsaturated state to the saturated state.
A current pulse is applied in the direction of turning on.

According to the second aspect of the present invention, not only the power consumption can be reduced during the operation in the discharge mode as in the operation in the charge mode, but also the power consumption during the transition from the charge mode to the storage mode can be reduced. It is possible to reduce the number. For example, the saturable reactor 112 shown in FIG. 3 has a length of 100 mm and an outer diameter of 300 mm,
If the iron core is ferrite, the inductance when the iron core is saturated is 100 millihenry, while it is 10 when unsaturated.
It is about 10,000 times, about 0 henry.

Therefore, the resistance when the superconducting switch is cut off is 10
Assuming that the terminal voltage of the superconducting coil 12 for energy storage is 0 ohm and 300 V, the energy P _SW consumed by the superconducting switch in the charging time of 10 seconds without the saturable reactor 112 is 9000 watt seconds. When there is the saturable reactor 112, the energy P _LS consumed by the superconducting switch is 2000 watt seconds or less, and the power consumption can be reduced to 1/3 or less.

FIG. 7 is a block diagram of an SMES to which the persistent current switch according to the third invention is applied. The persistent current switch 11 has a configuration in which a superconducting switch 111 and a transformer 113 are connected in series. Transformer 113 is the second
Has the same structure as the saturable reactor 112 used in the present invention, and the primary winding 42 and the secondary winding 43 of the superconducting wire are wound around the iron core 41.

That is, the superconducting switch 111 and the transformer 11
3 is connected in series with the primary winding 42, and the controller 18 is connected to the secondary winding 43 of the transformer 113. The control unit 18 is also connected to a control winding 23 that controls on / off of the superconducting switch 111. FIG. 8 is an operation principle diagram of the permanent current switch according to the third aspect of the present invention, and shows the transition state of the operation mode and the bias application direction by the transformer 113.

The function of the transformer 113 is to apply a current in the opposite direction to the current flowing through the permanent current switch when the permanent current switch 11 is in the connected state in the charge or discharge mode in which the superconducting switch 111 is in the cutoff state. Is. The voltage across the superconducting coil in the charge or discharge mode is V, the voltage output from the control unit 18 to the secondary winding 33 is V _2, and the winding ratio of the transformer 113 is as follows: primary winding: secondary winding = n: Set to 1.

At this time, if V = n · V ₂ is satisfied, the current flowing through the superconducting switch 111 becomes “0”, and it is possible to completely prevent the superconducting switch from generating heat in the cutoff state. When the resistance of the superconducting switch 111 in the cut-off state is R and the allowable heat generation amount in the cut-off state of the superconducting switch 111 is P, the parameters can be set so that P> (Vn · V ₂ ) ² / R holds. It is practical.

That is, in the control unit 18, it is desirable to control the voltage output from the control unit 18 to the secondary winding 33 so that V ₂ satisfies the above expression. FIG. 9 is a diagram for explaining the operation of the permanent current switch according to the third aspect of the present invention, in which the vertical axis represents the current flowing from above in the energy storage superconducting coil 12, the current flowing in the permanent current switch, and the power consumption in the permanent current switch. The horizontal axis represents the voltage applied to the secondary winding of the transformer.

If the storage mode is switched to the charging mode at time t ₁ , a voltage is applied from the control unit 18 to the secondary winding 33 of the transformer 113 to cancel the current flowing through the superconducting switch 111. When switching from the storage mode to the discharge mode at time t ₃ , the control unit 18
Applies a reverse voltage to the secondary winding 33 of the transformer 113.

The permanent current switch according to the fourth invention is
The same configuration as the permanent current switch 11 according to the third invention, a semiconductor switch is used instead of the superconducting switch, and the gate of the semiconductor switch is connected to the control unit 18 instead of the control winding of the superconducting switch. Are different. As described above, the semiconductor switch generally has a drawback that the resistance in the connected state is large, but by using a MOS-FET as the semiconductor switch, this drawback can be overcome to some extent.

In order to avoid the problem that the withstand voltage of the MOS-FET cannot be sufficiently high, the transformer 113 is connected in series to reduce the voltage applied to the MOS-FET at the time of interruption. That is, when the allowable breakdown voltage of the MOS-FET is V _max , each parameter must be set so as to satisfy the following equation.

V-V _max <n · V ₂ That is, in the control unit 18, the secondary winding 33 from the control unit 18
It is desirable to control the voltage output to V ₂ so that V ₂ satisfies the above formula.

[0042]

As described above, according to the first aspect of the present invention, the charging mode operation is performed by decreasing the current flowing through the permanent current switch at the start of the interruption of the permanent current switch and making the saturable reactor into an unsaturated state to increase the impedance. It is possible to reduce the current flowing through the permanent current switch and reduce heat generation in the superconducting switch.

According to the second aspect of the present invention, in the permanent current switch, a current pulse is applied to the secondary winding of the saturable reactor to control the unsaturated state or the saturated state of the saturable reactor, thereby controlling the charge mode or the discharge mode. It is possible to reduce the current flowing through the permanent current switch during operation and reduce heat generation in the superconducting switch. According to the third aspect of the present invention, the bias that generates a current in the opposite direction to the current flowing through the permanent current switch is applied via the secondary winding of the transformer, so that the current flowing through the superconducting switch is prevented when the superconducting switch is cut off. It is possible to reduce the heat generation in the superconducting switch.

In the permanent current switch according to the fourth aspect of the invention, the semiconductor switch is applied when the superconducting switch is cut off by applying a bias for generating a current in the opposite direction to the current flowing through the permanent current switch through the secondary winding of the transformer. It is possible to reduce the cutoff voltage applied to the.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an SMES to which a persistent current switch according to the first and second inventions is applied.

FIG. 2 is a sectional view of a superconducting switch used in the first and second inventions.

FIG. 3 is a sectional view of a saturable reactor used in the first and second inventions.

FIG. 4 is a magnetization characteristic diagram of a saturable iron core.

FIG. 5 is an operation explanatory view of the persistent current switch according to the first invention.

FIG. 6 is an operation explanatory view of the permanent current switch according to the second invention.

FIG. 1 is a configuration diagram of an SMES to which a persistent current switch according to a third invention is applied.

FIG. 8 is an operation principle diagram of a persistent current switch according to a third invention.

FIG. 9 is an operation explanatory view of the permanent current switch according to the third invention.

[Explanation of symbols]

 11 ... Permanent current switch 111 ... Superconducting switch 112 ... Saturable reactor 113 ... Transformer 13 ... Energy converter 14 ... DC power supply 15 ... Capacitor 16 ... PWM control device 17 ... Load 18 ... Control unit

Claims (4)

[Claims] 1. A superconducting switch for switching an on / off state by changing a conducting state of a superconducting wire from a superconducting state to a normal conducting state or from a normal conducting state to a superconducting state, and a saturation start current applied to the superconducting switch. A saturable iron core that is sufficiently smaller than the breaking current obtained by dividing the voltage by the breaking resistance that is the resistance when the superconducting switch is in the breaking state, and the superconducting switch wound around the saturable iron core. A persistent current switch comprising: a primary winding of a superconducting wire connected in series; and a saturable reactor that is connected to the superconducting switch in series. 2. The saturable reactor has a secondary winding of a superconducting wire wound around the saturable iron core, and a magnetic flux is applied in a direction to saturate the saturable iron core at the start of connection of the superconducting switch. A permanent current switch further comprising a pulse power supply for generating a current pulse for applying a magnetic flux to the secondary winding in a direction in which the saturable iron core is unsaturated at the start of interruption. 3. A superconducting switch for switching an on / off state by transitioning a superconducting wire from a superconducting state to a normal conducting state or from a normal conducting state to a superconducting state, an iron core, and the superconducting switch wound around the iron core. A primary winding of a superconducting wire that is connected in series, and a secondary winding that is wound around the iron core, and a transformer that is connected in series to the superconducting switch, and while the superconducting switch is cut off, A controller for applying to the secondary winding of the transformer a voltage for generating a current in the primary winding of the transformer in the opposite direction to the current flowing through the superconducting switch. 4. A semiconductor switch, an iron core, a primary winding of a superconducting wire wound around the iron core and connected in series to the semiconductor switch, and a secondary winding wound around the iron core. And a transformer connected in series to the superconducting switch, and a voltage that induces a current in the primary winding of the transformer in the opposite direction to the current flowing through the superconducting switch while the superconducting switch is shut off. And a controller for applying the voltage to the permanent current switch.