JP2009044785A - Superconducting coil energy storage device and superconducting coil energy storage method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconducting coil energy storage device which reduces the voltage being applied to a switch or to a diode. <P>SOLUTION: The superconducting coil energy storage device comprises an AC/DC conversion means, connected to an AC power supply system; a means for storing DC power obtained from the AC/DC conversion means in a superconducting coil 6; a means 14 for raising the current of the superconducting coil, a means for feeding back the current of the superconducting coil 6; and a means for discharging the power stored in the superconducting coil 6, wherein the coil current start means 14 comprises a rectifier 11, connected to the AC power supply system, the rectifier 11 and a switch 10 are connected in series with the superconducting coil 6, and a diode 8 is connected in parallel with the rectifier 11 and the switch 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a superconducting coil energy storage device and a superconducting coil energy storage method for storing energy of an AC power system in a superconducting coil.

  In general, the superconducting coil energy storage device is configured to store electricity from the AC power supply system in the superconducting coil and return the stored electricity to the AC power supply system. A typical device is a superconducting coil energy storage device that accumulates electric power during a period when there is little electric power demand and there is surplus electric power, and returns the accumulated electric power to the electric power system when the electric power demand increases (see, for example, Patent Document 1).

FIG. 3 is a circuit diagram showing a circuit configuration example of the superconducting coil energy storage device described in Patent Document 1. The superconducting coil energy storage device 100 converts AC power supplied from the AC power supply system 101 into DC power in the voltage source inverter circuit 103 via the insulation transformer 102 and stores the energy in the superconducting energy storage coil 105. To do. In addition, the energy stored in the superconducting energy storage coil 105 is converted into AC power by the reverse conversion operation via the DC capacitor 104 and released.
JP-A-61-262038

  In the superconducting coil energy storage device 100 of the technique proposed in Patent Document 1, the current of the superconducting energy storage coil 105 flows through the switches 106 and 107 and the diodes 108 and 109, and the voltage applied to the DC capacitor 104 is set. The switches 106 and 107 and the diodes 108 and 109 having the capacity to withstand are required. For this reason, there is a problem that the voltage and current of the switches 106 and 107 and the diodes 108 and 109 increase as the power of the device increases, resulting in an increase in size and cost of the device.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a superconducting coil energy storage device and a superconducting coil energy storage method capable of reducing the voltage applied to a switch or a diode.

  In order to solve the above-described problems, a superconducting coil energy storage device according to the present invention stores AC power connected to an AC power supply system and DC power obtained by the AC / DC conversion means in a superconducting coil. A power storage means; a coil current raising means for raising the current of the superconducting coil; a coil current recirculating means for recirculating the current of the superconducting coil; and a stored power discharge for releasing the power stored in the superconducting coil. A rectifier connected to an AC power supply system, and the rectifier and the switch are connected in series to the superconducting coil, and are parallel to the rectifier and the switch. A diode is connected.

  In order to solve the above-described problem, a superconducting coil energy storage method according to the present invention includes an AC / DC conversion step connected to an AC power supply system, and DC power obtained by the AC / DC conversion step. A power storing step for storing, a coil current starting step for starting the current of the superconducting coil, a coil current returning step for returning the current of the superconducting coil, and a storage for releasing the electric power stored in the superconducting coil A power discharging step, wherein the coil current raising step includes a rectifier connected to an AC power supply system, the rectifier and the switch connected in series to the superconducting coil, and parallel to the rectifier and the switch. A diode is connected to the circuit.

  According to the present invention, the voltage applied to the switch and the diode can be reduced.

  Embodiments of a superconducting coil energy storage device and a superconducting coil energy storage method according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a circuit diagram showing a circuit configuration example of a first embodiment of a superconducting coil energy storage device according to the present invention.

  In the superconducting coil energy storage device 1 according to the present invention, a voltage source inverter circuit 4 is connected to an AC power supply system 2 via an insulation transformer 3. The voltage source inverter circuit 4 exchanges energy with the AC power supply system by controlling the phase difference and voltage difference of the voltage with the AC power supply system 2. A DC capacitor 5 is connected between the DC output terminals of the voltage source inverter circuit 4. A switch 9 is connected to the DC capacitor 5 in parallel via a diode 7. Further, a superconducting coil 6 is connected in parallel to the DC capacitor 5, and a coil current raising means 14 is connected in series with the superconducting coil 6.

  The coil current raising means 14 includes a rectifier 11 connected to the AC power supply system 13, the rectifier 11 and the switch 10 connected in series to the superconducting coil 6, and a diode 8 in parallel to the rectifier 11 and the switch 10. Is connected. The control circuit 15 monitors current and voltage in the circuit and controls opening and closing of the switch 10. Here, the switches 9 and 10 use IGBTs (Insulated Gate Bipolar Transistors).

  Next, the operation of the superconducting coil energy storage device 1 according to the present invention will be described.

  First, in the energy storage mode, power is supplied to the superconducting coil 6 serving as power storage means by the coil current raising means 14. That is, the switch 9 is closed, and the voltage necessary for starting up the coil current is rectified by the diode rectifier 11 via the isolation transformer 12 and the switch 10 is repeatedly opened and closed to supply the DC current energy to the superconducting coil 6. . Here, the switch 10 is repeatedly opened and closed in order to adjust the coil current rising speed. Direct current energy is supplied to the superconducting coil 6 only when the switch 10 is closed.

  Next, in the energy holding mode, the current of the superconducting coil 6 is returned by the coil current return means. That is, the switch 9 continues to be closed and the switch 10 is opened, so that the current in the superconducting coil 6 circulates through the diode 8 and the switch 9. When the current decreases due to the influence of the circuit loss, the current increases by repeatedly closing or opening the switch 10.

  Further, in the mode for discharging energy, the power stored in the superconducting coil is discharged by the stored power discharging means. That is, by opening the switch 9, the current of the superconducting coil 6 is discharged to the DC capacitor 5 through the diode 8 and the diode 7, and the terminal voltage of the DC capacitor 5 is changed to the operation of the voltage source inverter circuit 4 by opening and closing the switch 9. It operates to control to the value according to.

Here, the voltage (VL) required for starting up the coil current is a voltage calculated by VL = L * di / dt + Vs where the inductance of the superconducting coil 6 is L [H] and the current change rate is di / dt. . Here, Vs is about 5 V corresponding to the voltage drop of the circuit, and assuming that L is raised to a current of 10 [H] and 1000 A in 600 seconds, VL is as follows.
[Equation 1]
VL = 10 * 1000/600 + 5 = 21.7 [V]

  Normally, when the conversion capacity of the voltage source inverter 4 is several MW or more, the DC voltage is required to be several kV or more. The switches 106 and 107 and the diodes 108 and 109 for raising the coil current in the superconducting coil energy storage device 100 of the conventional example also have to withstand a voltage of several kV.

  According to this embodiment, in the superconducting coil energy storage device 1 according to the present invention, the switch 10 only needs to have a voltage that can withstand the VL described above, and the component ratings of the diode rectifier 11 and the insulation transformer 12 also have a voltage of VL. It can be output. In particular, an expensive IGBT is used for the switch 10, and the fact that the voltage applied to the switch 10 is kept low has the effect of reducing the cost as well as downsizing the device.

[Second Embodiment]
FIG. 2 is a circuit diagram showing a circuit configuration example of the second embodiment of the superconducting coil energy storage device according to the present invention.

  A superconducting coil energy storage device 1A according to the present invention has an AC input terminal 2, an insulation transformer 3, a voltage source inverter circuit 4, a DC capacitor 5, a diode 7 and a switch 9 in the configuration of the first embodiment (see FIG. 1). It is the structure which made the structural unit which consists of 2 steps | paragraphs. Other configurations are the same as the configurations of the first embodiment, and the same reference numerals are given to the same configurations, and redundant descriptions are omitted.

  In the superconducting coil energy storage device 1A according to the present invention, in the A system, the voltage source inverter circuit 4A is connected to the AC power supply system via the insulation transformer 3A and the AC input terminal 2A. The voltage source inverter circuit 4A transfers energy to and from the AC power supply system by controlling the voltage phase difference and voltage difference with the AC power supply system. A DC capacitor 5A is connected between the DC output terminals of the voltage source inverter circuit 4A. A switch 9A is connected to the DC capacitor 5A in parallel via a diode 7A. The same applies to the B system.

  Next, the operation of the superconducting coil energy storage device 1A according to the present invention will be described.

  First, in the energy storage mode, power is supplied to the superconducting coil 6 which is power storage means by the coil current raising means 14. That is, the switches 9A and 9B are closed, and the voltage necessary for starting up the coil current is rectified by the diode rectifier 11 via the isolation transformer 12, and the switch 10 is repeatedly opened and closed, so that the DC current energy is supplied to the superconducting coil 6. Supply.

  Next, in the energy holding mode, the current of the superconducting coil 6 is returned by the coil current return means. That is, the switches 9A and 9B remain closed and the switch 10 is opened, whereby the current in the superconducting coil 6 is circulated through the diode 8 and the switches 9A and 9B. When the current decreases due to the influence of the circuit loss, the current increases by repeatedly closing or opening the switch 10.

  In the mode of releasing energy, the electric power stored in the superconducting coil 6 is released by the stored electric power discharging means. That is, by opening the switches 9A and 9B, the current of the superconducting coil 6 is discharged to the DC capacitor 5A through the diodes 8 and 7A. Further, the current of the superconducting coil 6 is discharged to the DC capacitor 5B through the diode 7B. The terminal voltage of the DC capacitor 5A is controlled to a value corresponding to the operation of the voltage source inverter circuit 4A by opening and closing the switch 9A, and the terminal voltage of the DC capacitor 5B is changed to the operation of the voltage source inverter circuit 4B by opening and closing the switch 9B. It operates to control to the value according to.

  In the present embodiment, examples are shown as the A system and the B system. However, the present invention is not limited to the two-stage configuration, and may be a multi-stage configuration having two or more stages.

  According to the present embodiment, it is possible to cope with the increase in voltage by increasing the circuit voltage accompanying the increase in energy storage capacity by connecting the same structural unit in multiple stages. Further, since the voltage (VL) required for raising the coil current is only a voltage drop of the switch 9B as compared with the circuit of the first embodiment, the voltage (VL) is only a few volts compared to the circuit of the first embodiment. Does not rise. That is, even if the circuit voltage rises, low voltage components can be used as they are for the switch 10, the diode 8, the diode rectifier 11, and the isolation transformer 12.

  As described above, according to the present invention, the component rating of the component used in the mode for storing energy in the superconducting coil 6 can be a component rated for a voltage (several tens of volts) necessary for starting up the coil current. For this reason, the whole apparatus can be reduced in size and cost.

  Further, the present invention is not limited to the embodiments described herein, and various modifications and changes can be made as necessary without departing from the gist of the present invention. For example, instead of the diode rectifier 11 and the switch 10 in the coil current raising means 14, a diode in which the diode of the diode rectifier 11 is replaced with an IGBT may be used.

The circuit diagram which shows the circuit structural example of 1st Embodiment of the superconducting coil energy storage apparatus which concerns on this invention. The circuit diagram which shows the circuit structural example of 2nd Embodiment of the superconducting coil energy storage apparatus which concerns on this invention. The circuit diagram which shows the circuit structural example of the superconducting coil energy storage apparatus described in patent document 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Superconducting coil energy storage device, 1A ... Superconducting coil energy storage device, 2 ... AC power supply system, 3 ... Insulation transformer, 4 ... Voltage type inverter circuit, 5 ... DC capacitor, 6 ... Superconducting coil, 7 ... Diode, 8 DESCRIPTION OF SYMBOLS ... Diode, 9 ... Switch, 10 ... Switch, 11 ... Diode rectifier, 12 ... Insulation transformer, 13 ... AC power supply system, 14 ... Coil current starting circuit, 15 ... Control circuit, 16 ... Voltage detector, 17 ... Current Detector, 18 ... current detector.

Claims (4)

AC-DC conversion means connected to the AC power supply system;
Power storage means for storing the DC power obtained by the AC / DC conversion means in a superconducting coil;
A coil current raising means for raising the current of the superconducting coil;
Coil current reflux means for refluxing the current of the superconducting coil;
Stored power discharge means for discharging the power stored in the superconducting coil,
The coil current raising means includes a rectifier connected to an AC power supply system, the rectifier and the switch connected in series to the superconducting coil, and a diode connected in parallel to the rectifier and the switch. A superconducting coil energy storage device. 2. The superconducting coil energy storage device according to claim 1, wherein the AC / DC conversion means includes a plurality of AC / DC conversion means for rectifying AC power from a plurality of AC power supply systems. AC / DC conversion step connected to AC power supply system;
A power storage step of storing the DC power obtained by the AC / DC conversion step in a superconducting coil;
A coil current raising step for raising the current of the superconducting coil;
A coil current reflux step for refluxing the current of the superconducting coil;
A stored power discharging step for discharging the power stored in the superconducting coil, and
The coil current rising step includes a rectifier connected to an AC power supply system, the rectifier and a switch connected in series to the superconducting coil, and a diode connected in parallel to the rectifier and the switch. A superconducting coil energy storage method. 4. The superconducting coil energy storage method according to claim 3, wherein the AC / DC conversion step includes a plurality of AC / DC conversion steps for rectifying AC power from a plurality of AC power supply systems.

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