JP2013172582A - Power conversion system and superconducting magnet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a superconducting coil upon occurrence of quenching, by recovering energy stored therein rapidly.SOLUTION: A power conversion system 100 includes a self-excited AC-DC conversion unit 110 which can perform conversion from AC to DC and conversion from DC to AC by connecting one end with an AC power supply 300, a DC capacitor 14 for connection with the other end of the self-excited AC-DC conversion unit 110, and a 2-quadrant chopper unit 120. When a quench detection unit 16c detects quenching of a superconducting coil 200 transferring energy via the 2-quadrant chopper unit 120, the power conversion system 100 stops the 2-quadrant chopper unit 120, and the AC-DC conversion unit 110 controls the voltage of the superconducting coil 200 not to exceed a predetermined value, thus regenerating energy of the superconducting coil 200 to the AC power supply 300.

Description

  The present invention relates to a technique for protecting a superconducting coil when a quench occurs.

  The synchrotron accelerator plays a role of accelerating the beam (particles) while rotating around. The accelerator is composed of a number of electromagnets in order to make the beam circulate in a fixed orbit, and collects and deflects the beam to ensure the orbit. At that time, the electromagnet is excited at a predetermined cycle by the power conversion system, and a large amount of power is supplied to deflect the beam. Superconducting coils are often used for this electromagnet.

  In superconducting coils, the phenomenon of quenching, where superconductivity switches to normal conduction, becomes a problem. When quenching occurs, the resistance component increases with respect to the current flowing in the superconducting state, and a large amount of heat is generated. And the range of quenching (normal range) is further expanded by the heat, and more and more heat is generated. Therefore, when quenching occurs in the superconducting coil, it is necessary to quickly reduce the current and protect the superconducting coil from overvoltage and overheating.

  Patent Document 1 shown below discloses a quench detection device for detecting quenching of a superconducting coil.

JP 2010-118453 A

When a quench occurs in the superconducting coil, it is necessary to detect it with a quench detection device and quickly cut off the current. However, when the current is cut off, the superconducting coil tries to keep the current flowing, so that there is a problem that the superconducting coil must be protected by consuming the energy.
Accordingly, an object of the present invention is to provide a technique for rapidly recovering energy accumulated in a superconducting coil and protecting the superconducting coil when quenching occurs in the superconducting coil.

  In order to solve the above problems, the power conversion system of the present invention includes an AC / DC conversion unit that is connected to an AC system at one end and can perform conversion from AC to DC and conversion from DC to AC, and the AC / DC conversion. When a quench detection unit detects quenching of a superconducting coil that includes a DC capacitor connected in parallel to the other end of the unit and a two-quadrant chopper unit and transfers energy via the two-quadrant chopper unit, The quadrant chopper unit is stopped, and the AC / DC converter unit controls the voltage of the superconducting coil so as not to exceed a predetermined value, and the energy of the superconducting coil is regenerated in the AC system.

  According to the present invention, when a quench occurs in a superconducting coil, the energy stored in the superconducting coil can be quickly recovered and the superconducting coil can be protected.

It is a figure which shows the structural example of a synchrotron. It is a figure which shows the structural example of the power conversion system in 1st Embodiment. It is a figure which shows the structural example of the power conversion system in 2nd, 3rd embodiment.

  Next, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings as appropriate.

A configuration example of a synchrotron including a superconducting coil will be described with reference to FIG.
The beam generated by the ion source 31 is accelerated by the linear accelerator 32 and taken into the circular orbit via the incident device 33. In the circular orbit, the beam is deflected by the deflecting electromagnet 34 and revolves, accelerated by the high-frequency accelerating cavity 35, narrowed by the quadrupole electromagnet 36, and taken out from the emission device 37. The main parts of the incidence device 33, the deflection electromagnet 34, the emission device 37, and the like are the superconducting coil 200 shown in FIGS. 2 and 3, and are electrically loaded with an inductance component.

(First embodiment)
Here, as a first embodiment, a configuration example of a superconducting coil and a power conversion system that excites the superconducting coil will be described with reference to FIG.
The power conversion system 100 includes at least a self-excited AC / DC converter 110, a DC capacitor 14, a two-quadrant chopper 120, a filter 130, and a controller 160.

  The power conversion system 100 inputs the AC power output from the AC power supply 300 to one end of the self-excited AC / DC converter 110 via the AC reactor 140, converts the AC power into DC power, and other than the self-excited AC / DC converter 110 Output from the end. A DC capacitor 14 and a two-quadrant chopper unit 120 are connected in parallel to the other end (DC output side) of the self-excited AC / DC converter 110. The two-quadrant chopper unit 120 controls the amount of current and excites the superconducting coil 200 via the filter 130. Details of the two-quadrant chopper section 120 will be described later.

  The self-excited AC / DC converter 110 has a function capable of executing conversion from AC to DC and conversion from DC to AC by connecting one end to the AC power supply 300. The self-excited AC / DC converter 110 can be constituted by, for example, a 6-arm IGBT (Insulated Gate Bipolar Transistor) element. Each IGBT element 11a-11f comprises each arm. Further, a gate drive signal subjected to PWM (pulse width modulation) modulation is input from the AC / DC converter control unit 16a to the gate which is a control electrode of each of the IGBT elements 11a to 11f. Each IGBT element 11a-11f is switched based on a gate drive signal, and has the function to convert alternating current power into direct current power or direct current power into alternating current power. In addition, although the diode element is connected in antiparallel to the IGBT element shown in FIG. 2, what connected the antiparallel diode element in this specification is called an IGBT element.

  The DC capacitor 14 has a function of smoothing the DC power output from the other end of the self-excited AC / DC converter 110 and accumulating the energy released from the superconducting coil 200.

  The two-quadrant chopper unit 120 will be described as a case where it is composed of two IGBT elements and two diode elements. In the first phase, the IGBT element 12a and the diode element 12b are connected in series, and an output is provided between the IGBT element 12a and the diode element 12b. In the second phase, the diode element 12c and the IGBT element 12d are connected in series, and an output is provided between the diode element 12c and the IGBT element 12d. A gate drive signal subjected to PWM modulation is input from the two-quadrant chopper controller 16b to the gate which is the control electrode of each IGBT element 12a, 12d. The two-quadrant chopper unit 120 has a function of exciting the superconducting coil 200 by controlling the amount of current by switching the IGBT elements 12a and 12d based on the gate drive signal.

The filter 130 includes reactors 13a and 13b and a capacitor 13c, and is connected between the output side of the two-quadrant chopper unit 120 and the superconducting coil 200. A specific frequency component generated by the two-quadrant chopper unit 120 is super high. It has a function of suppressing application to the conductive coil 200.
AC reactor 140 has a function of suppressing harmonic current.
The alternating current detection unit 150 measures the current value on the alternating current power supply side.
The voltage detector 151 measures the voltage value of the DC capacitor 14.
The direct current detector 152 measures the value of the current flowing through the superconducting coil 200.

  The controller 160 includes an AC / DC converter controller 16a and a two-quadrant chopper controller 16b. The AC / DC converter control unit 16a acquires the measurement value of the AC current detection unit 150 and the measurement value of the voltage detection unit 151, and converts AC to DC based on the acquired measurement value or converts DC to AC. And having a control function of regenerating the AC power supply 300. The two-quadrant chopper control unit 16b has a function of controlling switching of the IGBT elements 12a and 12d of the two-quadrant chopper unit 120 based on the measurement value of the DC current detection unit 152 and the output signal of the quench detection unit 16c.

Superconducting coil 200 is excited by power conversion system 100.
Moreover, the quench detection part 16c has a function which detects generation | occurrence | production of the quench in the superconducting coil 200, and outputs the detection signal which shows having detected, when a quench is detected.

Next, when quenching occurs in the superconducting coil 200, an operation for protecting the superconducting coil 200 will be described below.
When quenching occurs in superconducting coil 200, energy represented by the product of resistance component R generated by quenching and the square of current i is generated as heat. Therefore, the current i needs to be reduced as quickly as possible. However, when the current i is changed, the voltage across the superconducting coil 200 is expressed as L × di / dt using the inductance L. Therefore, the power conversion system 100 performs control so as to change the current i while maintaining a voltage as high as possible so that the superconducting coil 200 is not damaged.

  First, when a quench occurs in the superconducting coil 200, a detection signal is transmitted from the quench detection unit 16c to the two-quadrant chopper control unit 16b. The two-quadrant chopper control unit 16b receives the detection signal and stops the switching of the IGBT elements 12a and 12d in the off state. The current i flowing in the superconducting coil 200 passes through the diode elements 12b and 12c of the two-quadrant chopper 120 and flows into the DC capacitor 14, and the voltage of the DC capacitor 14 increases. AC / DC converter control unit 16a acquires a voltage measurement value of DC capacitor 14 at a predetermined cycle via voltage detection unit 151, and the voltage measurement value fluctuates from a predetermined voltage set in advance. The IGBT elements 11a to 11f of the self-excited AC / DC converter 110 are switched to convert DC power into AC power. That is, the power conversion system 100 can regenerate the energy of the superconducting coil 200 to the AC power supply 300 side.

  As described above, in the power conversion system 100 according to the first embodiment, when quenching occurs in the superconducting coil 200, the voltage stored in the superconducting coil 200 is maintained by keeping the voltage of the superconducting coil 200 as high as possible. Is recovered rapidly by the self-excited AC / DC converter 110 to the AC power supply 300 side, and the superconducting coil 200 can be protected. Note that regeneration of electric power as in the first embodiment has an advantage that energy can be effectively used compared to the case where energy is simply consumed by a protective resistor. Further, the first embodiment does not need to provide a large-scale cooling device for processing the heat generated by the protective resistance, and is effective from the viewpoint of equipment cost.

(Second Embodiment)
The structural example of the power conversion system 100 in 2nd Embodiment is demonstrated using FIG. The second embodiment is different from the first embodiment in that the power absorption unit 170 that absorbs energy released from the superconducting coil 200 in parallel with the DC capacitor 14 and the amount of energy that is absorbed by the power absorption unit 170 are controlled. A power absorption unit control unit 16d. In addition, the same code | symbol is attached | subjected to the same location as 1st Embodiment, and description is abbreviate | omitted. In addition, the power conversion system 100 performs control so as to change the current i while maintaining a voltage as high as possible so that the superconducting coil 200 is not damaged.

  As shown in FIG. 3, the power absorption unit 170 is connected to the other end of the self-excited AC / DC conversion unit 110 in parallel with the DC capacitor 14. The power absorption unit 170 is configured by connecting an IGBT element 17a and a resistance element 17b in series.

  The controller for AC / DC converter 16a acquires the voltage measurement value of the DC capacitor 14 at a predetermined cycle via the voltage detector 151, as in the case of the first embodiment. When the self-excited AC / DC converter 110 is overloaded and power cannot be regenerated to the AC power supply 300, the AC / DC converter controller 16a uses the measured voltage value of the DC capacitor 14 as a voltage value signal for the power absorption unit. It transmits to the control part 16d. The power absorption unit control unit 16d obtains a voltage measurement value and switches the IGBT element 17a of the power absorption unit 170 when the voltage of the DC capacitor 14 fluctuates from a predetermined voltage. Then, control is performed to maintain the voltage of the DC capacitor 14 at a predetermined value as much as possible by changing the resistance component of the power absorption unit 170, or control to prevent the voltage of the DC capacitor 14 from exceeding a predetermined value. That is, the value of the resistance element 17b is set so that the current flowing through the IGBT element 17a does not become too large.

(Third embodiment)
Next, the structural example of the power conversion system 100 in 3rd Embodiment is demonstrated using FIG. The power conversion system 100 performs control so as to change the current i while maintaining a voltage as high as possible so that the superconducting coil 200 is not damaged.

  In the third embodiment, the AC / DC converter control unit 16a acquires the measurement value of the AC current detection unit 150 at a predetermined cycle in addition to the operation described in the second embodiment. The AC / DC converter control unit 16a detects that an abnormality has occurred in the AC power supply 110 based on the measurement value of the AC current detection unit 150. Then, the AC / DC converter controller 16a transmits the voltage measurement value of the DC capacitor 14 measured by the voltage detector 151 to the power absorber controller 16d as a voltage value signal. The power absorption unit control unit 16d obtains a voltage measurement value, and when the voltage of the DC capacitor 14 fluctuates from a predetermined voltage set in advance, the power absorption unit control unit 16d performs an equivalent operation by switching the IGBT element 17a of the power absorption unit 170. Then, control is performed to maintain the voltage of the DC capacitor 14 at a predetermined value as much as possible by changing the resistance component of the power absorption unit 170, or control to prevent the voltage of the DC capacitor 14 from exceeding a predetermined value.

  As described above, the power conversion system 100 according to the second and third embodiments changes the resistance component of the power absorption unit 170 to change the voltage of the DC capacitor 14 to a predetermined value when quenching occurs in the superconducting coil 200. The voltage of superconducting coil 200 is kept high by maintaining the value. The power conversion system 100 can protect the superconducting coil 200 by absorbing the energy stored in the superconducting coil 200 into the power absorbing unit 170.

  In the present embodiment, the self-excited AC / DC converter 110 has been described. The circuit configuration of the self-excited AC / DC converter 110 shown in FIGS. 2 and 3 is not limited to the 6-arm configuration. Further, the circuit of the self-excited AC / DC converter 110 may use a semiconductor switching element other than the IGBT element.

  Moreover, although the case where the quench detection part 16c detected generation | occurrence | production of the quench in the superconducting coil 200 was described in this embodiment, the case where the quench detection part 16c predicted the generation | occurrence | production of quench may be included.

11a to 11f, 12a, 12d, 17a IGBT element 12b, 12c Diode element 13a, 13b Reactor for filter 13c Capacitor for filter 14 DC capacitor 16a Control unit for AC / DC conversion unit 16b Control unit for two quadrant chopper 16c Quench detection unit 16d Power Absorber control unit 17b Resistive element 100 Power conversion system 110 Self-excited AC / DC converter (AC / DC converter)
120 2 quadrant chopper unit 130 filter 140 AC reactor 150 AC current detection unit 151 voltage detection unit 152 DC current detection unit 170 power absorption unit 200 superconducting coil 300 AC power supply

Claims (7)

An AC / DC converter that is capable of performing conversion from AC to DC and conversion from DC to AC by connecting one end to an AC system, a DC capacitor connected in parallel to the other end of the AC / DC converter, and a two-quadrant chopper A power conversion system comprising:
When the quench detection unit detects quenching of the superconducting coil that transfers energy through the two-quadrant chopper unit, the two-quadrant chopper unit is stopped, and the voltage of the superconducting coil is set to a predetermined value by the AC / DC conversion unit. The power conversion system is characterized in that the superconducting coil energy is regenerated in the AC system so as not to exceed. Further connecting a power absorption unit that absorbs energy of the superconducting coil to the other end of the AC / DC conversion unit,
2. The power conversion system according to claim 1, wherein a voltage of the superconducting coil does not exceed a predetermined value by controlling an energy amount of the superconducting coil absorbed by the power absorbing unit.   3. The power conversion system according to claim 2, wherein when the AC to DC conversion unit stops operating due to an overload, the power absorption unit absorbs energy of the superconducting coil.   The power conversion system according to claim 2, wherein when the operation of the AC / DC converter stops due to an abnormality of the AC system, the power absorption unit absorbs energy of the superconducting coil. The power conversion system according to any one of claims 2 to 4, wherein the power absorption unit is configured by connecting a switch and a resistance element in series. The power conversion system according to claim 1, wherein the superconducting coil is used as an accelerator for accelerating particles.   A superconducting magnet device that is operated by the power conversion system according to any one of claims 1 to 6.

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