JP4015583B2 - Superconducting coil energy storage circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a superconducting coil energy storage circuit that stores energy of an AC power system in a superconducting coil and releases the energy stored in the superconducting coil to the AC power system.
[0002]
[Prior art]
There exists patent document 1 as an example of the conventional superconducting coil energy storage circuit.
[0003]
In FIG. 4, the superconducting coil / energy storage circuit includes a three-phase AC / DC conversion circuit 1, a DC capacitor 2, and a chopper circuit 3 as main circuit components.
[0004]
The three-phase AC / DC conversion circuit 1 includes a terminal 4 connected to an AC power supply system (not shown), an insulation transformer 5, a voltage source inverter circuit 6 and a DC reactor 7. Then, AC power is input, converted into DC power by the voltage source inverter circuit 6 and the DC reactor 7, and output.
[0005]
The chopper circuit 3 includes a superconducting coil 8 whose refrigerant is cooled by a refrigerator (not shown), bidirectional DC chopper circuits 9 and 10, and diodes 11 and 12. DC power output from the three-phase AC / DC conversion circuit 1 Is stored in the superconducting coil 8, and conversely, the energy stored in the superconducting coil 8 is released to the AC power system. The chopper circuit 3 includes current detectors 13 and 14 and a voltage detector 15, and outputs from these are input to the chopper control circuit 16 and are used to control the chopper circuits 9 and 10. .
[0006]
Such a superconducting coil energy storage circuit operates as follows. In other words, in the mode in which energy is stored in the superconducting coil 8, the chopper circuit 3 performs a chopping operation so that the current flowing through the superconducting coil 8 becomes a constant value to step down the terminal voltage of the DC capacitor 2 and is applied to the superconducting coil 8. Adjust the average voltage.
[0007]
The voltage source inverter circuit 6 performs DC voltage control so that the voltage of the DC capacitor 2 is maintained. In the mode in which the energy of the superconducting coil 8 is released, the chopper circuit 3 operates as a step-up chopper, charges the DC capacitor 2, and the voltage source inverter circuit 6 converts the energy of the DC capacitor 2 to the AC power supply system by reverse conversion operation. discharge.
[0008]
As described above, in the conventional superconducting coil energy storage circuit, by switching the operation mode of the chopper circuit 3 and the voltage source inverter circuit 6, energy can be stored in the superconducting coil 8 or the energy stored in the superconducting coil 8 can be exchanged. It can also be released to the power system.
[0009]
[Patent Document 1]
JP 61-262038 A (FIG. 1)
[0010]
[Problems to be solved by the invention]
In the conventional superconducting coil energy storage circuit described above, the average value of the DC voltage applied to the superconducting coil 8 in the mode of storing energy in the superconducting coil 8 is controlled by chopping the terminal voltage of the DC capacitor 2.
[0011]
However, the terminal voltage of the DC capacitor 2 is generally a high voltage of 1000 V or higher due to the exchange of power with the AC system via the voltage source inverter circuit 6. For this reason, the terminal voltage of the superconducting coil 8 is 1000 V or higher. A high ripple voltage is applied.
[0012]
Such a high ripple voltage causes a large change in magnetic flux density inside the superconducting coil 8 and causes a loss. For this reason, the burden of the refrigerator provided in the superconducting coil 8 is increased.
[0013]
An object of the present invention is to provide a superconducting coil energy storage circuit capable of reducing coil loss when energy is stored in a superconducting coil and reducing the burden on a refrigerator provided in the superconducting coil.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a DC power supply circuit having a series switch for exciting a superconducting coil, and a DC current connected to the DC power supply circuit via a switch in parallel and accumulated in the superconducting coil. Operates as a closed circuit switch in the mode that holds the energy of the current, and operates as a step-up chopper in the output mode, a DC capacitor that charges the chopper when the chopper circuit operates as a step-up chopper, and the DC capacitor A superconducting coil energy storage circuit comprising a voltage-type inverter circuit that discharges AC energy to an AC power supply system connected in parallel.
[0015]
According to the present invention, since the current of the superconducting coil is controlled by a DC power supply circuit different from the DC capacitor, there is no possibility of applying an excessive ripple voltage, coil loss can be reduced, and the refrigeration provided in the superconducting coil can be reduced. The burden on the machine can be reduced.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
(First embodiment)
FIG. 1 is a diagram showing a configuration example of a superconducting coil energy storage circuit according to a first embodiment of the present invention.
[0018]
In FIG. 1, a voltage type inverter circuit 21 is connected to an AC power supply system 20 to convert AC power from the AC power supply system 20 into DC power. A DC capacitor 22 is connected in parallel to the voltage type inverter circuit 21 and charges DC power from the voltage type inverter circuit 21. A superconducting coil 26 is connected to the DC capacitor 22 via a chopper circuit 23, a diode switch 24, and a DC power supply circuit 25.
[0019]
The mode in which energy is stored in the superconducting coil 26 is realized by turning on the series switch 29 connected in series to the DC power supply 30 constituting the DC power supply circuit 25 and closing the switch 27 of the chopper circuit 23.
[0020]
At this time, it is possible to arbitrarily control the current flowing through the superconducting coil 26 by controlling the on / off of the series switch 29 and controlling the average DC voltage applied to the superconducting coil 26. That is, when the series switch 29 is turned on, the current increases, and when the diode switch 24 is opened, it circulates through the switch 27 of the chopper circuit 23 and maintains a constant value.
[0021]
The mode in which the energy of the superconducting coil 26 is released is realized by opening the series switch 29 of the DC power supply circuit 25 and operating the chopper circuit 23 and the voltage source inverter circuit 21. The operation in this mode is the same as in the conventional example.
[0022]
Thus, according to the present embodiment, since the current of the superconducting coil 26 is controlled by the DC power supply circuit 25 different from the DC capacitor 22, there is no possibility of applying an excessive ripple voltage, and the coil loss can be reduced. In addition, the burden on the refrigerator provided in the superconducting coil 26 can be reduced.
[0023]
(Second Embodiment)
FIG. 2 is a diagram showing a configuration example of a superconducting energy storage circuit according to the second embodiment of the present invention. The same parts as those in FIG. State.
[0024]
In FIG. 2, a snubber circuit composed of a snubber capacitor 31 and a snubber diode 32 is connected in parallel with the switch 27 of the chopper circuit 23 ′. The snubber diode 32 and the snubber capacitor 31 are connected to one electrode of the DC capacitor 22 via the snubber resistor 33 from the connection point. Similarly, the snubber capacitor 34, the snubber diode 35, and the snubber resistor 36 are connected to the series switch 329 of the DC power supply circuit 25 ′.
[0025]
The operation of the superconducting energy storage circuit according to the present embodiment configured as described above is as follows. That is, when the switch 27 of the chopper circuit 23 ′ is opened during energization, the energy stored in the circuit wiring inductance (not shown) charges the snubber capacitor 31 via the snubber diode 32.
[0026]
Next, when the switch 27 is closed, the snubber diode 32 is turned off, so that the energy of the snubber capacitor 31 charges the DC capacitor 22 via the snubber resistor 33. A snubber circuit including a snubber capacitor 34, a snubber diode 35, and a snubber resistor 36 provided in the series switch 29 of the DC power supply circuit 25 'has the same operation.
[0027]
Thus, in the second embodiment, the energy stored in the wiring inductance is absorbed by the snubber capacitors 31 and 34, so there is no fear of applying an overvoltage to the switch. Moreover, since the voltage of the snubber capacitors 31 and 34 is clamped to the voltage of the DC capacitor 22, the loss of the snubber resistors 33 and 36 is also reduced.
[0028]
(Third embodiment)
FIG. 3 is a diagram showing a configuration example of a superconducting energy storage circuit according to the third embodiment of the present invention. The same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted. Only the part is described.
[0029]
In FIG. 3, the chopper circuit 23 ″ and the DC power supply circuit 25 are provided with a common snubber capacitor 37 and a snubber resistor 39, and the snubber diodes 38 and 40 are individually connected.
[0030]
Even with this configuration, the chopper circuit 23 ″ and the series switches 27 and 29 of the DC power supply circuit 25 do not turn on and off at the same time, so that the operation of the snubber circuit functions in the same way as when installed independently. The number of parts can be reduced.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a highly reliable superconducting coil energy storage circuit while reducing coil loss when energy is stored in the superconducting coil, reducing the burden on the refrigerator.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a superconducting coil energy storage circuit according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram showing a superconducting coil energy storage circuit according to a second embodiment of the present invention.
FIG. 3 is a circuit diagram showing a superconducting coil energy storage circuit according to a third embodiment of the present invention.
FIG. 4 is a circuit diagram showing an example of a conventional superconducting coil energy storage circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 20 ... AC power supply system, 21 ... Voltage type inverter circuit, 22 ... DC capacitor, 23 ... Chopper circuit, 24 ... Diode, 25 ... DC power supply circuit, 26 ... Superconducting coil, 27 ... DC chopper, 28 ... Diode, 29 ... Switch Part, 30 ... DC power supply.

Claims (3)

A DC power supply circuit with a series switch for exciting the superconducting coil;
A chopper circuit that is connected in parallel with the DC power supply circuit via a switch, operates as a closed circuit switch in a mode that holds the energy of the DC current accumulated in the superconducting coil, and operates as a boost chopper in the output mode;
A DC capacitor that charges the chopper when the chopper circuit operates as a boost chopper;
A superconducting coil energy storage circuit comprising: a voltage type inverter circuit that discharges AC energy to an AC power supply system connected in parallel with the DC capacitor. The series switch of the DC power supply circuit and the switch of the chopper circuit are connected so that at least one of the poles has the same potential as any one of the poles of the DC capacitor, and a snubber diode and a snubber capacitor are connected in parallel with each switch. The snubber circuit is connected to absorb the wiring inductance energy as the voltage energy of the snubber capacitor during the switch-off operation, and the snubber capacitor energy is discharged to the DC capacitor via the snubber resistor during the switch-on operation. The superconducting coil energy storage circuit according to claim 1, wherein: 3. The superconducting coil energy according to claim 2, wherein the snubber capacitor and the snubber resistance for the series switch of the DC power supply circuit and the snubber capacitor and the snubber resistance of the chopper circuit are common. Storage circuit.

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