JP3015863B2 - Variable impedance element, variable impedance current limiter, and variable impedance superconducting converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable impedance element capable of performing a switching operation by giving a superconductor / normal conduction phase change to a superconductor by a magnetic field generator, and a variable impedance element using the same. The present invention relates to a variable impedance type superconducting converter used for DC / AC power conversion for a DC superconducting power transmission cable, which is promising as a power application of a current limiter and a high-temperature superconducting material.

[0002]

2. Description of the Related Art In general, a power semiconductor converter is used as a current limiting device having a large current or a means for converting a direct current to an alternating current or for limiting a current.

[0003]

Although the superconductor has zero DC electrical resistance, AC loss occurs when used in AC. This loss becomes a large value in the operation at the commercial frequency of 50 or 60 Hz, and the loss is extremely large.
The cable must be cooled using cooling refrigeration such as e-gas. This is a major bottleneck in the practical application of AC superconducting power transmission cables. It has been found that if the cable current is changed to DC, there is no AC loss from the superconductor, so that the superconducting characteristics can be used most effectively. However, since all current power systems operate on alternating current, direct current must be converted to alternating current. Since the current power semiconductor type converter operates at room temperature, it is necessary to pull out a cable cooled to an extremely low temperature to room temperature, which causes a large thermal loss. In addition, the loss caused by the semiconductor converter is enormous, so that the overall efficiency is greatly reduced. For this reason, it has been considered that DC superconducting power transmission cannot be put to practical use. To solve this, it is essential to develop a device that can efficiently convert DC current to AC current at extremely low temperatures.

[0004] Therefore, the present invention provides a variable impedance element unit and an impedance variable element which enable cryogenic operation of power conversion, which is impossible with a conventional semiconductor converter, and which realizes an efficient DC superconducting power transmission cable. It is an object of the present invention to provide a variable current limiter and a variable impedance superconducting converter.

[0005]

The variable impedance element according to the present invention comprises a yoke constituting a closed magnetic circuit, a cylindrical superconductor wound on the yoke, and an insulating film on the cylindrical superconductor. And a magnetic field generating section for giving a superconducting / normal conducting phase change to the cylindrical superconductor and switching the impedance of the main coil between small and large.

Further, the variable impedance type current limiting device according to the present invention comprises a yoke constituting a closed magnetic circuit, a cylindrical superconductor wound on the yoke, and an insulating film interposed on the cylindrical superconductor. A wound main coil, a magnetic field generating unit for giving a superconducting / normal conducting phase change to the cylindrical superconductor and switching the impedance of the main coil between small and large, and a primary coil connected in series with the main coil. And a current transformer comprising a winding and a secondary winding for supplying the induced current to the magnetic field generating unit.

Further, in the variable impedance superconducting converter according to the present invention, a yoke constituting a closed magnetic circuit, a cylindrical superconductor wound on the yoke, and an insulating film on the cylindrical superconductor are provided. Two variable impedance element devices each having a wound main coil and a magnetic field generating unit for giving the superconducting / normal conducting phase change and switching the impedance of the main coil between small and large are connected in series with each of the two main coils. Connected, one end of the main coil connected in series is connected to one pole of the DC power supply, the other end is connected to one end of the load, the other end of the load is connected to the other pole of the DC power supply, the two A capacitor is connected between the connection point of the variable impedance element and the other pole of the DC power supply, and a superconducting / normal conduction phase change is alternately applied to the cylindrical superconductors of the two variable impedance element. Magnetic Those having a generator.

Further, a synthesis transformer is used in place of the capacitor.

Further, the magnetic field generating section of each of the variable impedance element devices has a control coil wound on an auxiliary yoke branched from a yoke constituting the closed magnetic circuit, and the control coil is energized. Generates a magnetic field.

[0010]

In the variable impedance element of the present invention, when a magnetic field is generated by energizing the magnetic field generating section, the cylindrical superconductor changes its phase from the superconducting state to the normal conducting state, and the impedance of the main coil rapidly increases. , Switching is performed.

Further, in the variable impedance type current limiting device of the present invention, when a large current flows through the main coil, the current transformer 2
A current is induced in the next winding, which flows through the auxiliary coil, and a magnetic field is generated from the magnetic field generating unit, so that the impedance of the variable impedance element device rapidly increases and the current is limited.

In the variable impedance superconducting converter according to the present invention, the columnar iron yoke is covered with a cylindrical superconductor, the upper part is covered with a cylindrical electric insulating material, and the main coil is wound thereon. The series of the main coil and the cylindrical superconductor by controlling the superconducting characteristics of the cylindrical superconductor by controlling the energization of the auxiliary coil of the external magnetic field generating means by connecting to the series with the cylindrical superconductor and giving the circuit impedance. Two variable impedance element devices that can change the impedance created by the circuit are prepared, and the control magnetic field of each variable impedance element device is generated alternately, and the impedance of the variable impedance element device is alternately changed to change the impedance. Alternates the DC current flowing through the element unit and combines two variable impedance element units and a capacitor. Luke, or by combining the varying current in the synthesis transformer, is intended to convert direct current to alternating current.

[0013]

1 and 2 are a front view and a plan view showing the configuration of an embodiment of a variable impedance element according to the present invention. In FIG. 1, reference numeral 10 denotes a variable impedance element (hereinafter, simply referred to as an element), and FIG. 3 is an enlarged view of a central portion thereof.

As shown in FIGS. 1 to 3, the element device 10 covers a central yoke 11 which is a part of a yoke constituting a closed magnetic circuit with a cylindrical superconductor 12 such as a cylindrical or rectangular tube. The upper part is covered with an insulating film 13 and the main coil 14
Is wound around. The main coil 14 and the cylindrical superconductor 12 are connected in series. Reference numerals 15 and 16 denote surrounding yokes, which together with the central yoke 11 constitute a closed magnetic circuit. Reference numeral 17 denotes an auxiliary yoke, which is provided in a direction orthogonal to the center yoke 11 from the surrounding yokes 15 on both sides thereof, and a control coil 18 is wound thereon. The auxiliary yoke 17 and the control coil 18 The magnetic field generator 19 is configured. The magnetic field generator 19 is provided with control means for controlling the energization of the control coil 18, but is not shown.

Now, the equivalent impedance Z of the element 10
Is composed of an inductance L and a resistance R formed by a superconductor as shown in FIG. When the cylindrical superconductor 12 is in the superconducting state, the resistance R is zero, and the magnetic flux generated by the main coil 14 due to the diamagnetic property which is a characteristic of the superconductor is generated by the central yoke 1.
Since it does not reach 1, the inductance L of the main coil 14 is the same as the air-core coil and has a very small value, and the impedance Z (jwL + R) of the element device 10 has a very small value. However, the control coil 18 shown in FIGS.
When the superconducting state of the cylindrical superconductor 12 is destroyed by applying a current to the
Since the magnetic flux created by 4 loses the diamagnetic property of the cylindrical superconductor 12, it reaches the central central yoke 11 to generate a large inductance L, and the impedance Z of the element 10 becomes a very large value. This means that the control coil 18
The characteristics of the cylindrical superconductor 12 are controlled by the
Can greatly change the value of the impedance Z of
This means that a kind of switching operation can be performed.

FIG. 5 is a diagram showing the configuration of one embodiment of the variable impedance type current limiting device according to the present invention. This embodiment is configured by using the element device 10 shown in FIGS. 5, the same reference numerals as those in FIGS. 1 to 3 denote the same parts, reference numeral 20 denotes a variable impedance current limiter (hereinafter, simply referred to as a current limiter), reference numeral 21 denotes a current transformer, and primary windings 22, 2.
The primary winding 22 is connected in series with the main coil 14, and both ends of the secondary winding 23 are connected to both ends of the control coil 18.

The basic principle of the current limiter 20 is that when the current flowing through the current limiter 20 is small, the magnetic flux does not reach the central yoke 11 due to the magnetic shielding effect of the cylindrical superconductor 12 and the main coil 14
Has a small impedance. However, when a fault current flows, the magnetic flux generated by the main coil 14 reaches the central yoke 11, and the impedance is rapidly increased to control the flowing current. In the present invention, since the control coil 18 of the element device 10 is used, the current limiting characteristic can be freely controlled by making the coupling coefficient between the primary winding 22 and the secondary winding 23 variable. Further, since the auxiliary yoke 17 is provided, the magnetic flux is concentrated and the superconducting characteristics of the cylindrical superconductor 12 are quickly destroyed, so that the responsiveness is excellent. A quick recovery can be achieved by providing a switch in series with the main coil 14 and opening the switch.

FIG. 6 is a basic circuit diagram of one embodiment of a variable impedance superconducting converter (inverter) according to the present invention. Reference numeral 30 denotes a variable impedance superconducting converter, which converts from DC to AC when a capacitor is used. Is what you get. 10A and 10B are element devices, and 18A and 1
8B is a control coil, 31 is a capacitor, 40 is a load, and the others are the same as in FIGS.

FIG. 7 shows an equivalent circuit of the variable impedance superconducting inverter shown in FIG. 6, and FIG. 8 shows the timing of the current flowing through the control coils 18A and 18B and the change in impedance of the element 10 caused by the timing. It is shown. 7, the same components as those in FIG. 1 are denoted by the same reference numerals, and φ _A and φ _B are control coils 18A,
18B shows the current flowing through 18B.

The operation of FIG. 7 will be described with reference to the timing chart of FIG. Until time t ₀ ~t ₁ shown in FIG. 8, the current phi _B of the control coil 18B is being energized element 10
B has a large impedance Z _B and an impedance Z _A
Is a small value. This is because a charging current flows from the power supply (ad side) E toward the capacitor 31 (solid line in FIG. 7).
Means that. However, at this time, the impedance Z _B is current so large from the capacitor 31 to the load 40 is extremely small. Between times t _{1 and} t ₂ , Z _A is very large and Z _B is small, so the charge stored in capacitor 31 flows toward load 40 (dashed line in FIG. 7), and Charging current hardly flows. By repeating this, the fluctuating voltage shown in FIG. 9 appears on the load 40, and the DC current can be converted to the AC current.

FIG. 10 is a basic circuit diagram showing another embodiment of the variable impedance superconducting converter according to the present invention, in which a combining transformer 32 is used in place of the capacitor 31 in the embodiment of FIG.

In FIG. 10, 33A and 33B are primary windings connected in series, 33C is a secondary winding, 34 is a yoke, and 35 is an intermediate tap at a connection point between the primary windings 33A and 33B. Connected. Others are the same as FIG.

Next, the operation will be described. Control current ICl
Is on, the cylindrical superconductor 12 of the element 10A is broken, and the magnetic flux reaches the central yoke 11, so that the main coil 1
4 becomes large and the current hardly flows. On the other hand, the impedance of the element 10B is low. As a result, a current of I ₂ flows through the synthesis transformer 32. Conversely to the control current IC2 is flowing current I ₁ for the synthesis transformer 32 for the on the large impedance element unit 10B. Since the directions of the currents I ₁ and I ₂ are opposite, the magnetic flux in the composite transformer 32 changes alternately and the secondary winding 33
AC power is obtained at C.

[0024]

As described above, the element device according to the present invention is provided with a magnetic field generating section, and the magnetic field generated by the magnetic field generating section gives the cylindrical superconductor a phase change of superconductivity / normal conduction to control the impedance. Therefore, switching can be performed.

Further, since the current limiting device according to the present invention is configured using the above-described element devices, the current limiting characteristics can be changed and the response speed can be increased.

Further, in the variable impedance superconducting converter according to the present invention, the impedance of the element is controlled by controlling the diamagnetic characteristics of the superconductor by the magnetic field generating means, and the impedance change of the two elements is utilized. Thus, it is possible to convert DC to AC in a cryogenic environment where superconductivity occurs. In addition, since the used capacitors (other than the electrolytic solution type) or the synthetic transformer operate without any trouble even in a very low temperature state, it is possible to install all circuits in a very low temperature environment. When connecting a DC power system that superconductivity is good at to a normal AC power system that operates at room temperature, a cooled current lead called a power lead is necessary to introduce current from room temperature to cryogenic environment. In addition, a power semiconductor conversion element is required. With such a configuration, a large amount of heat enters from the power lead, and the loss of the semiconductor converter is enormous, so that the efficiency of the entire system is significantly reduced. If the present invention is used, there is almost no resistance loss unlike a semiconductor converter, and since it can be operated in a cryogenic environment, the efficiency can be greatly improved and a DC power device using superconductivity can be realized.

[Brief description of the drawings]

FIG. 1 is a front view showing a configuration of an element device according to the present invention.

FIG. 2 is a plan view of the embodiment of FIG.

FIG. 3 is a detailed view of the basic components of the element device.

FIG. 4 is an equivalent circuit diagram of the variable impedance element of the embodiment shown in FIGS. 1 and 2;

FIG. 5 is a diagram showing a configuration of one embodiment of a current limiter according to the present invention.

FIG. 6 is a diagram showing a configuration of one embodiment of a variable impedance superconducting converter according to the present invention.

FIG. 7 is an equivalent circuit diagram of the embodiment of FIG.

FIG. 8 is a diagram showing a state of energization timing of a control coil and a change in impedance of an element device in the embodiment of FIG. 6;

FIG. 9 is a diagram showing an output waveform after conversion in the embodiment of FIG. 6;

FIG. 10 is a circuit diagram showing the configuration of another embodiment of the variable impedance superconducting converter according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Variable impedance element device 10A Variable impedance element device 10B Variable impedance element device 11 Central yoke 12 Cylindrical superconductor 13 Insulating film 14 Main coil 15 Surrounding yoke 16 Surrounding yoke 17 Auxiliary yoke 18 Control coil 19 Magnetic field generation Unit 20 Variable impedance current limiter 21 Current transformer 22 Primary winding 23 Secondary winding 24 Yoke 30 Impedance variable superconducting converter 31 Capacitor 32 Synthetic transformer 33A Primary winding 33B Primary winding 33C Secondary winding Wire 34 Yoke 35 Middle tap 40 Load

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI H02H 3/08 ZAA H01F 5/08 ZAAZ (56) References JP-A-2-105402 (JP, A) JP-A-1-160065 JP-A-64-827 (JP, A) JP-A-51-118057 (JP, A) JP-A-1-99479 (JP, A) JP-A-4-112620 (JP, A) Japanese Patent Laid-Open No. 1-10021 (JP, A) Japanese Patent Laid-Open No. 1-164231 (JP, A) Japanese Patent Laid-Open No. 1-217902 (JP, A) Japanese Patent Laid-Open No. 4-368422 (JP, A) Japanese Patent Laid-Open No. 50484/1984 JP, A) JP 42-727 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02H 9/02 H01F 6/06 H01H 33/00 H01L 39/20 H02H 3 / 08 H02M 7/00 H02M 3/00

Claims (4)

(57) [Claims] A central yoke which is a part of a yoke constituting a closed magnetic circuit; a cylindrical superconductor which covers the periphery of the central yoke in a cylindrical shape; A main coil wound through an insulating film and connected in series with the cylindrical superconductor; an outer yoke that forms a closed magnetic circuit together with the center yoke; and a direction perpendicular to the center yoke. An auxiliary yoke branched from the surrounding yoke; and a control coil wound on the auxiliary yoke, wherein when no current flows through the control coil, the cylindrical superconductor is provided. Is in a superconducting state, the electric resistance of the cylindrical superconductor becomes substantially zero, and a small inductance is generated in the main coil. On the other hand, when a current flows through the control coil, the cylindrical superconducting The superconducting state of the body is destroyed, and the electric resistance of the cylindrical superconductor becomes relatively large. ,
In addition, the variable impedance element device in which the control coil controls a current flowing through the main coil so that a large inductance is generated in the main coil. 2. A central yoke which is a part of a yoke constituting a closed magnetic circuit; a cylindrical superconductor which covers the periphery of the central yoke in a cylindrical shape; A main coil wound through an insulating film and connected in series with the cylindrical superconductor; an outer yoke that forms a closed magnetic circuit together with the center yoke; and a direction perpendicular to the center yoke. An auxiliary yoke branched from the surrounding yoke; a control coil wound on the auxiliary yoke; a primary winding connected in series with the main coil; A current transformer having a secondary winding connected to both ends of the control coil; and when no overcurrent flows through the main coil, the tubular superconductor is in a superconducting state, and the tubular superconductor is in a superconducting state. The electric resistance of the body becomes almost zero, and a small inductance is generated in the main coil, while the main coil has a small inductance. When an overcurrent flows through the tubular superconductor, the superconducting state of the tubular superconductor is destroyed, the electrical resistance of the tubular superconductor becomes relatively large, and
An impedance variable current limiter wherein the current flowing through the main coil is controlled by the current transformer and the control coil so that a large inductance is generated in the main coil. 3. The apparatus according to claim 1, further comprising two variable impedance elements, wherein said main coil and said tubular superconductor of each of said variable impedance elements are connected in series. One end of a circuit connected in series is connected to one pole of a DC power supply, and the other end is connected to one end of a load. The other end of the load is connected to the other pole of the DC power supply.
A capacitor is connected between the connection point of the two variable impedance element devices and the other pole of the DC power supply, and the superconducting and normal conduction phase change is performed by the two cylindrical variable impedance element devices. A variable impedance superconducting converter, wherein alternating current is supplied to the load by alternately applying the control coils to the superconductor. 4. A primary winding of a composite transformer, comprising two variable impedance elements according to claim 1, wherein the main coil and the cylindrical superconductor of each of the variable impedance elements are combined. Connected in series with a wire interposed therebetween, and the two impedance-variable type elements connected in series.
Both ends of the element and an intermediate tag between the primary windings of the composite transformer
A DC power supply is connected between the control coil and the control coil, and the superconducting / normal conducting phase change is alternately applied to the cylindrical superconductors of the two impedance variable element devices by the respective control coils, and the synthesis is performed. A variable impedance superconducting converter characterized in that a predetermined AC power source is obtained from a secondary winding of a transformer.