JPS605744A - Energy storing device by superconductive magnet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an energy storage device that converts alternating current into direct current through a thyristor converter and stores electrical energy using a superconducting magnet.

[Prior art and its problems]

As this type of energy storage device, one shown in FIG. 1 is conventionally known. In FIG. 1, reference numeral 1 denotes a power supply line as an AC power supply, TC a thyristor converter consisting of a transformer 2 and a thyristor 3 for stepping up and down the alternating current from the power supply line 1, 4 a liquid helium, etc. A superconducting magnet provided in a cryogenic chamber T containing a
6 is a persistent current switch provided in the cryogenic chamber T, 6 is a hoki resistor whose resistance value is sufficiently smaller than the resistance value of the magnet 4 under normal conduction state, and 7 is a resistor for superconducting magnet 4. A switch is shown which closes the switch when it transitions to normal conductivity and quickly recovers energy to the protective resistor 6.

In the conventional energy storage device shown in Fig. 1, when storing drowsy energy, the thyristor converter TC is first operated as a forward converter to convert alternating current to direct current, and then converts the alternating current into direct current. When the superconducting magnet 4 is FjJJ magnetized with a direct current and the current is supplied to the superconducting magnet 4 until the maximum allowable current value is reached, the persistent current switch 5, which is typically a mechanical switch, is closed, the persistent current flows between the superconducting magnet 4 and the superconducting magnet 4. It circulates in a closed circuit formed with the persistent current switch 5, thereby storing electrical energy.

In order to extract the electrical energy stored in the superconducting magnet 4 to the external power supply line 1, a Cyrisk converter TC is used.
By operating the magnet as an inverse converter and opening the persistent current switch 5, electrical energy can be taken out to the power supply line 1 by the voltage generated in the superconducting magnet 4.

In the energy storage device using a superconducting magnet as described above, when the singing level around the superconducting magnet 4 locally increases, or when the current or magnetic flux density in the superconducting magnet 4 exceeds a certain value, the superconducting magnet 4 changes to a normal conducting state in a short time, generates Joule heat, and generates an extremely high voltage across the magnet 4. When this situation occurs, the persistent current switch 5 is turned off. By quickly opening the switch 7 and closing the switch 7, the stored energy is shunted to the protective resistor 6, and the stored energy is rapidly consumed by the resistor 6, which may cause dielectric breakdown of the superconducting magnet 4 or cause sudden liquid helium leakage. This prevents it from evaporating.

However, in such a conventional energy storage device, almost all of the stored energy is consumed by the protective resistor 6 when the superconducting magnet 4 transitions to normal conductivity. When stored in this device, there was a problem that not only the energy loss would be enormous, but also the liquid helium would be consumed a lot, which would lead to an increase in the size of the protective device.

[Purpose of the invention]

This invention was made in view of the above-mentioned problem, and when a superconducting magnet undergoes a normal conduction transition, the normal conduction transition is kept in a part of the superconducting magnet, and the stored energy is released to preserve this superconducting magnet. It is an object of the present invention to provide a superconducting energy storage device that minimizes loss and consumption due to vaporization of liquid helium in a cryogenic chamber and miniaturizes a protective device.

[Key points of the invention]

This invention provides an energy storage device equipped with a superconducting magnet connected to an AC power source via a thyristor converter, in which the superconducting magnet is configured by connecting a plurality of superconducting coils in series, and each superconducting coil is provided with an insurance permanent current. If a switch is connected in parallel to each other, and a switch is connected in parallel to the entire superconducting magnet consisting of multiple superconducting coils, and a normal conduction transition occurs in some of the superconducting coils, the coil in which the normal conduction transition has occurred can be detected. The superconducting magnet can be protected by forming a local closed circuit consisting of the coil and the insurance persistent current switch connected in parallel to the coil, and a closed circuit consisting of the other healthy coils and the switch installed in parallel throughout the superconducting magnet. This system allows the stored energy to be absorbed into healthy superconducting coils without releasing much of it to the outside.

[Embodiments of the invention]

FIG. 2 is an electric circuit diagram showing an embodiment of the present invention, and FIG. 3 is a current diagram for explaining its operation.

Components that are the same as those in FIG. 1 are designated by the same symbols and their explanations will be omitted. In FIG. 2, the superconducting magnet 8 is composed of, for example, three divided superconducting coils 8a, 8b, and 8C connected in series, and an insurance persistent current switch 9a is connected to each coil.

9b and 9C are each connected in parallel. Further, a persistent current switch 10 is connected in parallel with the superconducting magnet 8, and is housed in a cryogenic chamber T1 together with the superconducting magnet 8 and the persistent current switches 9a to 9C for maintenance. Further, a switch 11 is connected in series between the superconducting magnet 8 and the thyristor converter TC, and is opened only when the superconducting magnet 8 is imaged to disconnect the thyristor converter TC and the superconducting magnet 8.

In such a configuration, in order to store electrical energy by the superconducting maknet 8, the thyristor converter TC is first operated as a forward converter, so that the current value changes between each of the superconducting coils 8a and 8b.

each coil 8a until the maximum allowable current value of 8C is reached.

Charge to 8B, 8C. At this time, the protective persistent current switches 9a, 9b, 9c and the persistent current switch 10 are all kept open.

When charging is complete, the persistent current switch 10 is closed to preserve energy. Even if the persistent current switch 10 is closed,
Each protective persistent current switch 93-9C is left open. Therefore, the current flowing through each superconducting coil 8a to 8C circulates within the closed circuit formed by the permanent current switch 10 and the superconducting magnet 8, and is not released to the outside. will continue to be stored. To extract the electrical energy stored in the superconducting magnet 8 to the external power supply line 1, the thyristor converter TC is operated as an inverse converter and the permanent current switch 10 is opened, thereby performing the operation explained in FIG. It is similar to

Next, the operation when normal conduction transition occurs in some of the superconducting coils will be explained with reference to FIG. 3.

- As an example, if a normal conduction transition occurs in the superconducting coil 8b, the persistent current switch 9b for maintenance connected in parallel to the superconducting coil 8b is immediately closed, and at the same time the persistent current switch 10 is also closed. The protection persistent current switches 9a and 9c are still left open. In this series of operations, the switch 11 is finally opened to disconnect the superconducting magnet 8 from the Cyrisk converter TC. As a result, the electrical energy possessed by the superconducting coils 8a and 8c is transferred into a closed circuit formed by the superconducting coils 8a and 8c, the persistent current switch 10, and the protective persistent current switch 9b, as shown by the solid line P loop in FIG. of'
The energy is allowed to circulate as an electric current, so that the energy continues to be stored without being released to the outside.

On the other hand, the current in the superconducting coil 8b flows through a local closed circuit as shown by the broken line Q loop in FIG. Most of the stored energy is transferred to the superconducting coils 8a and 8c by mutual inductance between the superconducting coils 8a and 8c, and the energy of the superconducting coil 8b can be rapidly attenuated.

Therefore, when a normal conduction transition occurs in a part of the superconducting magnet 8, it is important to suppress the normal conduction transition locally without propagating it to other normal parts, and only a small part of the stored energy is suppressed. Compared to the conventional device shown in FIG. 1, losses due to energy release and consumption due to vaporization of liquid helium in cryogenic conditions can be minimized.

Also, whether a voltage is generated in the superconducting magnet 8 due to the normal conduction transition, or this generated voltage is sufficiently low that the superconducting magnet 8 will not suffer dielectric breakdown. Furthermore, according to this method, since the insurance persistent current switch is located inside the cryogenic chamber T1, there is no need to provide special current leads from each of the superconducting coils 8a, 8b, 8c to the external normal temperature section, and Since there is no heat penetrating through the leads, there is no reduction in efficiency as an energy storage device. Furthermore, since there is no storage resistor, there is an advantage that the device can be made smaller.

FIG. 4 shows a different embodiment of the invention.
The difference from the embodiment in the figure is that the persistent current switch 10 in FIG.
Since the switch 12 is provided externally, the operation as an energy storage device is no different from the embodiment shown in FIG. 2 except for the degree of energy attenuation. The embodiment of FIG. 4 is practical when the frequency of energy input and output is relatively high.

In the embodiment described above, an example has been described in which the superconducting magnet 8 is divided into three coils, but the number of divisions is not limited to three. The larger the number of divisions, the smaller the impact can be made to be negligible since it will not affect each circuit due to the operation that occurs when normal conduction occurs. Furthermore, in the embodiment, an example has been described in which the switch 11 is connected in series between the Cyrisk converter TC and the superconducting Macnet 8, but the switch 11 may be omitted.

This is because instead of opening this switch 11, the thyristor can be blocked.

〔Effect of the invention〕

According to this invention, a superconducting magnet is constructed by connecting a plurality of superconducting coils in series, a protective persistent current switch is connected in parallel to each superconducting coil, and a switch is connected in parallel to the superconducting magnet, When a normal conduction transition occurs in some superconducting coils, a local closed circuit consisting of the coil in which the normal conduction transition has occurred and a protective persistent current switch connected in parallel to that coil, other healthy coils, and a superconducting magnet is generated. Since a closed circuit is formed with switches installed in parallel throughout the entire structure, the loss of electrical energy and the consumption of liquid helium, which is a cryogenic refrigerant, for protecting the superconducting magnet can be minimized, and the protection device This has the effect of reducing the size of the device.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of an energy storage device using a conventional superconducting magnet, Fig. 2 is an electric circuit diagram of an embodiment of the present invention, and Fig. 3 is a current diagram for explaining the operation of the embodiment of Fig. 2. , and FIG. 4 are electrical circuit diagrams of different embodiments of the present invention. 8... Superconducting magnet, 8a, 8b, 8c... Superconducting coil, 9a, 9b, 9c... Persistent current switch for protection, 10... Persistent current switch, 11.12 Switch, TC... Thyristor conversion Vessel, Tt, T221 Mouth: 2 Diagrams: 3 Concave 1/ Su: 4 Diagrams

Claims (1)

[Claims] 1) In an energy storage device equipped with a superconducting magnet connected to an AC power source via a thyristor converter,
A superconductor characterized in that the superconducting magnet is constructed by connecting a plurality of superconducting coils in series, a protective persistent current switch is connected in parallel to each of the superconducting coils, and a switch is further connected in parallel to the superconducting magnet. Energy storage device using magnets.