JPH06327171A - Electric-power storage apparatus - Google Patents

Abstract

PURPOSE:To increase the amount of a persistent current by a method wherein a voltage-drop element is installed in a route reaching a capacitor from a power supply, a voltage drop is caused here, a current from the capacitor is added to the current of a battery and a superconducting coil is charged. CONSTITUTION:When switches S1, S2 in a chopper circuit 16 are turned on, a current flows in a route from the switch S1 through a superconducting coil 18 up to the switch S2, and the coil 18 is charged. At this time, since a prescribed voltage drop is caused in a voltage-drop element 20, the potential on the power-supply side of a capacitor 14 becomes higher than the potential on the downstream side of the voltage-drop element 20, and the capacitor 14 is discharged. Consequently, its discharge current is added to the charging current of the coil 18. Then, when the switch S1 or S2 is turned off, the coil 18 is separated from a battery 10, a current flowing to the voltage-drop element 20 is reduced, and the capacitor 14 is charged by a current from the battery 10 until it becomes the same voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power storage device for storing power in a superconducting coil, and more particularly to an increase in the amount of permanent current flowing in the superconducting coil.

[0002]

2. Description of the Related Art Conventionally, as an energy storage device,
The use of superconducting coils has been studied. That is, since the superconducting coil has an electric resistance of 0, there is no energy loss while a permanent current is flowing through it. Also,
Since the electric resistance is 0, the electric wire itself may be thin, and it is not necessary to upsize the device even when a large current is applied.

Therefore, it is considered to use this superconducting coil in an energy storage device. For example, Japanese Unexamined Patent Publication No. 63-80730 discloses that a superconducting coil is used in order to cope with a large output fluctuation by a fuel battery that is weak against the output fluctuation.

In this example, electric power is supplied from a power source to a load, and an electric power storage unit including a superconducting coil is connected in parallel to the load. This power storage unit includes a chopper circuit and a superconducting coil. Therefore, when the power consumption of the load changes significantly, the chopper circuit is operated to allow a predetermined amount of current to flow in and out of the superconducting coil, thereby slowing down the change in the power consumption on the load side. In this way
The fuel battery, which is vulnerable to output fluctuations, can be adapted to a load with large output fluctuations.

[0005]

In the power storage device using such a superconducting coil, the power storage amount is the amount of permanent current flowing in the superconducting coil. Therefore, in order to increase the amount of power supplied from the power storage device, the amount of permanent current in the superconducting coil must be increased. Therefore, there is a demand for increasing the amount of permanent current as much as possible. However, there is generally an upper limit to the current supply capability of the power supply. Particularly, in a battery power supply, the maximum output current is not so large because its internal resistance is quite large. Therefore, there is a problem that the permanent current flowing through the superconducting coil cannot be increased.

Further, the input / output of the electric current of the power storage device is performed by the chop control of the chopper circuit, and the chopping control causes the discharge current to pulsate. And to suppress this, increase the chop frequency or
It may be possible to smooth it with a capacitor. But,
Since the switching of the device cannot be performed so fast, the chop frequency cannot be increased so much. On the other hand, if a capacitor is used to perform sufficient smoothing, the capacity of the capacitor becomes very large, and the size of the device becomes large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric power storage device capable of increasing the amount of permanent current and suppressing pulsation.

[0008]

A power storage device according to the present invention includes a voltage drop element having one end connected to one end of a power supply,
A capacitor whose one end is connected to the other end of the voltage drop element and whose other end is connected to the other end of the power supply; and a chopper circuit that is connected in parallel to this capacitor and controls the flow of current by switching the built-in switching element. , A superconducting coil that receives a current controlled by this chopper circuit, and by switching the switching element of the chopper circuit, the current supplied through the voltage drop element charges and discharges the capacitor to increase the storage current of the superconducting coil. It is characterized by

A voltage drop element having one end connected to one end of the power source, a capacitor having one end connected to the other end of the voltage drop element and the other end connected to the other end of the power source, and the capacitor connected in parallel to the capacitor. , A chopper circuit that controls the flow of current by switching the built-in switching element, a superconducting coil that receives the current controlled by this chopper circuit, and a transistor that is inserted and arranged in the path from the chopper circuit to the other end of the power supply. And, by switching the switching element of the chopper circuit, the storage current of the superconducting coil is increased by charging and discharging the capacitor with the current supplied through the voltage drop element.

[0010]

In the present invention, the superconducting coil is charged by the control of the chopper circuit, but the capacitor is charged with the superconducting coil disconnected from the power supply by the chopper circuit. Since the voltage drop element is provided between the power supply and the capacitor, a voltage drop occurs when a current flows there. Therefore, the chopper circuit can charge the superconducting coil by adding the current from the capacitor to the current from the power source while the superconducting coil and the power source are connected. Therefore, a current exceeding the maximum energization current of the power source can be passed through the superconducting coil, and effective power storage can be performed.

Further, by disposing the transistor in the current path between the power source and the capacitor, it is possible to selectively increase the voltage drop with respect to the current of a predetermined amount or more,
Pulsation can be effectively suppressed by the condenser.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 is a circuit diagram showing the overall configuration of the first embodiment, in which a motor 12 is connected to a battery 10 and the battery 1
The electric power from 0 drives the motor 12. on the other hand,
The battery 10 includes a capacitor 14 and a chopper circuit 16
The superconducting coil 18 is connected via. And
Under the control of the chopper circuit 16, the state in which the superconducting coil 18 is connected to the battery 10 to supply the electric current to the superconducting coil or discharge the electric current from the superconducting coil 18 and the superconducting coil 1
8 is disconnected from the battery and switched to a state for storing electric power. The control unit 22 controls on / off of the switches S1 and S2.

To this end, the chopper circuit 16 has diodes D1 to D4 for flowing a current from the ground side to the power supply potential side, and the diodes D1 and D2 and the diode D3,
D4 are respectively connected in series, and a switch S1 and a switch S2 are arranged in parallel with the diode D1 and the diode D4. And the diodes D1 and D
Both ends of the superconducting coil 18 are connected to the connection portion of No. 2 and the connection portion of the diodes D3 and D3, respectively.

In this embodiment, the voltage drop element 20 is arranged in the conduction path on the power supply potential side of the battery 10 and the capacitor 14. Therefore, when a current flows there, a voltage drop occurs. Then, when charging the superconducting coil 18, the switches S1 and S2 are turned on. by this,
A current flows through the path of switch S1 → superconducting coil 18 → switch S2, and superconducting coil 18 is charged. Then, at this time, a predetermined voltage drop occurs in the voltage drop element 20. Therefore, the potential of the capacitor 14 on the power supply side becomes higher than the potential on the downstream side of the voltage drop element 20, and the capacitor 14 is discharged. Therefore, this discharge current is added to the charging current of the superconducting coil 18. Also,
If the switch S1 or S2 is turned off, the superconducting coil 1
8 is disconnected, the current flowing through the voltage drop element 20 decreases, and the capacitor 14 is charged by the current from the battery 10 until the same voltage is reached. Therefore, the switch S1
(Or S2) is turned on, the switch S2 (or S1) is repeatedly turned on and off, so that the battery 10
The charging of the superconducting coil 18 and the charging of the capacitor 14 with the current from the capacitor 14 and the current from the capacitor 14 are repeated. The charging current of superconducting coil 18 is the sum of the discharging currents of battery 10 and capacitor 14, and a current larger than the maximum current (rated current) of battery 10 can be supplied to superconducting coil 18.

That is, as shown in FIG. 2, initially, the switches S1 and S2 are turned on to supply a current to the superconducting coil 18. The inclination at this time is a magnitude obtained by dividing the voltage across the superconducting coil 18 by the reactance of the superconducting coil 18. Then, when the amount of current in the superconducting coil 18 reaches the rated current of the battery 10, the current flowing in the superconducting coil 18 becomes constant.

When the switch S2 (or S1) is turned on / off at a duty ratio of 50% while the switch S1 (or S2) is turned on, the battery 10 is charged as described above.
The permanent current of the superconducting coil 18 is further increased by the current from the capacitor 14 and the current from the capacitor 14. At this time, the current of the battery 10 is almost 1 of the current flowing through the superconducting coil 18.
/ 2, and the current flowing through the superconducting coil 18 can be increased until this current reaches the rated current. Therefore, in this example, the current flowing through the superconducting coil 18 can be increased to about twice the rated current of the battery 10.

Thus, in this embodiment, the battery 10
The superconducting coil 18 can be energized with a current larger than the current that can be energized, and a large amount of energy can be stored therein. Here, the stored energy of the superconducting coil 18, when the reactance of the superconducting coil 18 L, the current flowing here was I, a LI ^2/2. In addition,
By reducing the duty ratio during switching, the amount of permanent current can be further increased. It is also preferable that the duty ratio is initially increased and then gradually decreased.

Next, when discharging from the superconducting coil 18, both the switches S1 and S2 are turned off. As a result, both ends of the superconducting coil 18 are connected to the load 12 via the diodes D2 and D3, and the load 12 can be driven by the current from the superconducting coil 18.

Here, when both the switches S1 and S2 are turned off, the current of the superconducting coil 18 flows into the load 12. In order to adjust the amount of this current, the switch S1 (or S2) in the chopper circuit 16 is adjusted. Turn on and off. Thereby, the amount of current supplied to the load 12 can be adjusted. Here, in this embodiment, the voltage drop element 22 is arranged in the current path. Therefore, the load 12
A voltage drop occurs here when a current flows through. Therefore, the capacitor 14 repeats charging / discharging according to ON / OFF of the switch S1, and pulsation in the current of the load 12 can be reduced. Therefore, it is possible to reduce the generation of noise caused by driving the load 12, for example, the motor.

That is, when the voltage drop element 20 is not provided, the current from the superconducting coil 18 is directly supplied to the load 12. Therefore, if this current is controlled by switching the switch S1 (or S2),
The current flowing through the load 12 is in the form of a pulse that repeats 0 and a predetermined current value.
Driving causes a large amount of noise.

As described above, by utilizing the inductance as the voltage drop element 20, the pulsation at the time of discharge can be reduced and effective discharge can be performed. As described above, since the current supply to the load 12 can be leveled, it becomes relatively easy to allocate the distribution of the current supply from the battery 10 and the superconducting coil 18 using a map or the like.

Here, a specific example of charging and discharging in the superconducting coil 18 will be described. When the superconducting coil 18 has an inductance of 10H and a current of 100A flows through it, the stored energy is (1/2) × 10 (100).
² = 50 kJ. 3 from this state to the battery 10 side
To discharge kW (V _B = 300 V), voltage drop element 20
The current I _RB flowing to the left in the direction should be 10 A on average. When S ₁ and S ₂ are simply turned off, the current I _RB flowing through the voltage drop element 20 becomes as shown in FIG. Therefore, normally, S ₁ is turned on and S ₂ is chopped with the duty ratio D.

This duty ratio D is determined by the superconducting coil 18
Of the current I _LSC and the discharge desired current of the battery 10 is I _B , it is determined so that D (t) = I _B / I _LSC .

FIG. 4 shows a current waveform subjected to the above control.
In this way, the current fluctuates in the stable region. This pulsation causes problems such as generation of noise and increase in power loss, so it is necessary to reduce this pulsation. Current fluctuation width ΔI
The When the magnitude of the pulsating [Delta] I / I _B normalized by I _B, the magnitude of this pulsation, resistance voltage dropping element 20 R
When the resistance of _B, represented by approximately _{ΔI / I B (%) =} (1-D) / C · R B · f. Here, f is the chop frequency, and C is the capacitance of the capacitor 14. The time τ until stabilization is almost CR _B.

For example, f = 1 KHz, C = 50 mF, D
= 0.5 (I _LSC = 20 A and I _B is 10 A), the pulsation magnitude is 10% at the resistance value R = 0.1Ω. Therefore, in order to suppress the magnitude of pulsation to 1% or less, a resistance of 1Ω is necessary. However, if a resistance of 1Ω is inserted, I _B ² R = 10 ² × 1 = 1
It becomes 00W and the power loss becomes 10 times. Also, the frequency f
Is limited to 10 KHz in relation to the switching performance of the element. Further, the capacitance of the capacitor 14 is set to 0.
If it is set to 5F, the device becomes large. Therefore, in the present invention, an inductor is inserted as the voltage drop element 20.

[0027] There is a limit to the size of the _{inductor, L = 0.5mH >> (R B} 2/4) times as to settle down to the command current cause overshoot as the case Figure 5 C is applied .

[0028] ^{_{L = 0.03mH << (R B 2}} /4) overshoot as in the case of C Figure 5 although not small effect of reducing Hado. That is, the current fluctuation width ΔI = 3A.

As shown in FIG. 5, the size of the inductor is approximately L = 0.125 mH = (R _B ² /
4) When C, the best result is obtained. That is, the current fluctuation width ΔI = 1A, and there is no overshoot. Therefore, as the voltage drop element 20, L = (R _B ² /
4) It will be appreciated that inductors of the order of C are suitable.

When the inductor is made extremely small such as L = 0.001 mH, the pulsation is hardly reduced as shown in FIG.

Here, the inductor has a current capacity of 3
00A is required. For this reason, if it is made of a normal copper wire, it becomes very large in size and electrical resistance is generated there, which makes it difficult to design. Therefore, it can be easily constructed by using a superconducting wire. That is, if the inductor is 0.125 nH, the diameter φ20 mm and the length l = 20 mm.
Can be configured with enough. At this time, I _B = 300 A, which is an empty core.

Second Embodiment Next, the configuration of the second embodiment is shown in FIG. Thus, in this embodiment, the transistor 30 is provided in the path connecting the battery 10 and the capacitor 14. The transistor 30 regulates the current at the operating point where the collector current is saturated. As a result, even if a resistor having a small resistance value is used for the voltage drop element 20, the pulsation of current can be effectively suppressed by the action of the transistor 30. The reference battery 32 determines the base current of the transistor 30.

That is, the transistor 30 changes in accordance with the collector-emitter voltage VCE, as shown in FIG. Then, the base current of the transistor 30 is set to a constant value I
_{If TRB} , VCE
The collector current I _C increases according to the
Even if E rises, it does not increase much. Therefore, the bending point P is generated.

Then, the base current of the transistor 30 is adjusted so that the battery current I _B changes in the vicinity of the bending point P. Then, when the current I _B pulsates and the current I _B exceeds a predetermined value (the inflection point P), the voltage drop due to the transistor 30 rapidly increases. Therefore,
The capacity V · 2ΔV · C of the capacitor 14 is greatly utilized, and the pulsation can be effectively suppressed. If the transistor 14 is not provided and the capacitor 14 is caused to exhibit the same capability by the voltage drop element (resistor) 20,
The power consumption of the voltage drop element 20 will increase. That is, if the vicinity of the bending point P of the transistor 30 is used as in the present embodiment, the voltage drop can be reduced when the amount of current is small, and the power consumption during normal use can be suppressed. The power consumption of the transistor 30 is I _C · V _CE .

In the above example, the base current of the transistor 30 is also constant when the current I _B is fixed. It should be noted that the temperature drift must be compensated.
However, as shown in FIG. 8, the switch S of the chopper circuit 16 is
It is preferable to change the base current I _TRB of the transistor 30 and move the inflection point in synchronization with ON / OFF of 1 (or S2). That is, at the time of discharging the superconducting coil 18, when S1 is turned on and the superconducting coil 18 is disconnected,
The base current I _TRB of the transistor 30 is reduced and the resistance here is increased. Therefore, the capacitor 14 can effectively prevent pulsation. The base current can be controlled by adjusting the reference battery 32.

As described above, according to this embodiment, the occurrence of pulsation can be effectively suppressed. Here, the pulsation magnitude is first
As in the example, it is represented by ΔI / I _B , C = 50 mF, duty ratio = 0.5, f = 1 kHz, I _LSC = 200 A,
When I _B = 100 A, the magnitude of pulsation and power loss are as follows.

(1) If there is no transistor 30 and the resistance value R _B of the voltage drop element 20 is 0.1Ω, ΔI / I _B = 10% and power loss is 1.2 kW.

(2) When the transistor 30 is arranged and the resistance value R _B of the voltage drop element 20 is 0.1Ω, ΔI / I _B = 3% and power loss is 1.1 kW.

(3) When the transistor 30 is arranged and the resistance value R _B of the voltage drop element 20 is 0Ω, ΔI / I _B = 4% and power loss is 400 W. In this example, the base current of the transistor 30 is constant. By disposing the transistor 30 in this manner, power loss can be reduced and pulsation can be effectively suppressed.

In the above example, the NPN type transistor 3 is used.
Although 0 is used, a PNP type transistor may be used. In this case, the transistor 30 is arranged in series with the voltage drop element 20 as shown in FIG.

Further, instead of the transistor 30, a FET
(Voltage effect transistor), IGBT, etc. can also be used.

[0042]

As described above, according to the power storage device of the present invention, the voltage drop element is provided in the path from the power source to the capacitor. Therefore, due to the voltage drop here, the current from the capacitor can be added to the current of the battery to charge the superconducting coil. Therefore, a current exceeding the maximum energization current of the power source can be passed through the superconducting coil, and effective power storage can be performed.

Further, by disposing a transistor in the current path between the power source and the capacitor, the voltage drop can be selectively increased for a current of a predetermined amount or more,
Pulsation can be effectively suppressed by the condenser.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a first embodiment.

FIG. 2 is a characteristic diagram showing a current state of the example.

FIG. 3 is a characteristic diagram showing a current flowing through a voltage drop element in the example.

FIG. 4 is a characteristic diagram showing the relationship between the chop control of the chopper circuit 16 and the current flowing through the voltage drop element in the embodiment.

FIG. 5 is a voltage drop element (inductor) according to the embodiment.
FIG. 6 is a characteristic diagram showing the relationship between the size of the current and the current of the superconducting coil.

FIG. 6 is a circuit diagram showing a configuration of a second embodiment.

FIG. 7 is a characteristic diagram showing a relationship between VCE and collector current IC of a transistor.

FIG. 8 is a characteristic diagram showing an example of base current control of a transistor in the example.

FIG. 9 is a circuit diagram showing another arrangement example of transistors.

[Explanation of Codes] 10 Battery 12 Load 14 Capacitor 16 Chopper Circuit 18 Superconducting Coil 20 Voltage Drop Element 30 Transistor

Claims (2)

[Claims] 1. A voltage drop element having one end connected to one end of a power supply, a capacitor having one end connected to the other end of the voltage drop element and the other end connected to the other end of the power supply, and connected in parallel to the capacitor. , A chopper circuit that controls the flow of current by switching the built-in switching element, and a superconducting coil that receives the current controlled by this chopper circuit, and a voltage drop element is switched by switching the switching element of the chopper circuit. An electric power storage device, characterized in that a storage current of a superconducting coil is increased by charging and discharging a capacitor by an electric current supplied through the electric storage device. 2. A voltage drop element having one end connected to one end of a power supply, a capacitor having one end connected to the other end of the voltage drop element and the other end connected to the other end of the power supply, and connected in parallel to the capacitor. , A chopper circuit that controls the flow of current by switching the built-in switching element, a superconducting coil that receives the current controlled by this chopper circuit, and a transistor that is inserted and arranged in the path from the chopper circuit to the other end of the power supply. An electric power storage device comprising: a switching element of a chopper circuit for switching a switching element of a chopper circuit to charge and discharge a capacitor by a current supplied through a voltage drop element to increase a storage current of a superconducting coil.