JP2015220871A - Pulse magnetic field generating source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable power received from an external power source to be set to fixed power by a pulse magnetic field generator.SOLUTION: In a highly repetitive magnetic field generator having magnetic energy storage means in which the current of a magnetic energy storage coil is controlled by a low-speed chopper so that the voltage of a voltage source capacitor is fixed and the pulse current of a magnetic field generating coil is controlled with high precision from the voltage source by a high-speed chopper, the voltage of the voltage source capacitor at the intermediate portion is controlled to be fixed, so that the received power can be smoothed by merely connecting a DC power source comprising passive circuits such as a transformer for receiving power from an external power source, a diode rectifier, etc. to the voltage source capacitor in parallel.

Description

  The present invention relates to a magnetic field generating power source.

  Magnetic energy is stored in the magnetic field generator, and the pulsed magnetic field generating power source is charged and discharged with magnetic energy every time generation of the pulsed magnetic field is stopped. The pulse magnetic field generating power source needs to supply both the Joule loss and the magnetic energy as the current flows to the magnetic field generator. When the device becomes larger, this magnetic energy increases, and when the pulse rate increases, it is ideal to store the energy when discharging the stored energy and reuse it when it is restarted. . In recent large-scale magnetic field generators, a superconducting conductor is adopted because the coil current density is large and the electric resistance is zero. Magnetic energy increases with respect to Joule loss, and it is not efficient from the viewpoint of electric power charges if the magnetic energy is discarded every time. Moreover, even a power source that can be regenerated is difficult because there are restrictions on returning energy to the power system. For this purpose, it is ideal that the pulse magnetic field generating power source has energy storage means. Examples of the energy storage means include a capacitor, a flywheel, and a magnetic energy storage (SMES) coil.

In order to use the SMES coil as energy storage means, a circuit has been proposed in which two chopper circuits shown in FIG. 1 are subjected to current / voltage conversion with a voltage source capacitor interposed therebetween. Using a low-speed chopper circuit, the current is charged into the intermediate voltage source capacitor, and the on / off control is performed so as to maintain the SMES current at the voltage of the determined voltage source capacitor. The voltage of the capacitor is passed through the magnetic field generator by the second high-speed chopper circuit. At that time, it is required to control the current with the necessary accuracy of the magnetic field generator, so the voltage of the voltage source is constant. I want.
In this double chopper circuit, the energy of the entire system is reduced by operation due to Joule loss of the magnetic field generator and loss inside the chopper circuit. It is necessary to supply only the decreasing energy from an external power source (in many cases, a commercial power source). Regarding the method of replenishing energy from an external power source, generally, there is a method of replenishing energy by inserting a voltage source in series with the SMES coil, which is also adopted in the previous application. A replenishment voltage source connected in series with the low-speed chopper circuit of FIG. 1 replenishes the loss from the external power source.

  Power reception from an external power source preferably receives constant power regardless of pulse operation and has no power peak, but for that purpose, voltage is generated while the current changes according to pulse operation, so the power is constant. Requires advanced control. Because power supply capacity is only for loss

  As shown in FIG. 5 of the patent document, a constant voltage power control of an external power source placed in series with a magnetic coil requires a variable voltage current DC power source together with a current sensor, a voltage sensor, and an arithmetic and control unit. High-speed and high-precision chopper circuit for current control of magnetic field generator, relatively low-speed chopper circuit to make SMES coil current necessary for voltage source capacitor, DC voltage from external power supply to supplement loss Three types of circuits to be injected into the circuit are required.

"Pulse power supply" Patent 4382665

  The problem to be solved is that a pulse magnetic field generating power source as an SMES coil energy storage device requires a power source that simultaneously performs three types of control, but this is complicated.

  The present invention is a system that makes it possible to control the constant injection power from an external power source by controlling the voltage of the voltage source capacitor by the voltage control capability of the chopper circuit of the SMES coil. The most important feature is that the constant control of the received power can be rationalized only by connecting only the diode rectifier in parallel to the voltage source capacitor from the external power source.

The pulse magnetic field generating power supply of the present invention can be realized by a power supply that controls only the SMES coil and two types of chopper circuits, and does not require calculation control of current × voltage = power.

FIG. 1 is an explanatory diagram showing a method of implementing a power supply for generating a pulse magnetic field. FIG. 2 shows a simulation circuit of the embodiment. FIG. 3 shows a simulation calculation result of the example.

The SMES coil is assumed to have the same inductance Lsm as the magnetic field generating coil, but it is assumed that the energy required for operation is sufficiently stored.

  FIG. 1 is a circuit diagram of an embodiment of the apparatus of the present invention. One high-speed chopper is turned on / off by S1 gate control, and two low-speed choppers are turned on / off by S2 gate control. The voltage source capacitor C11 of No. 3 needs a capacity sufficient to maintain a stable voltage as a voltage source of the high-speed chopper, and is 25 mF here. The diode power supply 4 sends current from the external power supply to the voltage source capacitor, but the magnitude of the current is constant if the voltage of the voltage source capacitor does not change.

  The voltage sensor detects the voltage of the voltage source capacitor, and is turned off when the voltage of the capacitor is raised by the control of the S2 gate control, and turned on when lowered. Here, hysteresis control for outputting an on / off command with a voltage width of Δ with respect to the voltage command is assumed. However, since the voltage control method can be implemented by other voltage control methods, description of the electronics and the control system is omitted.

The current sensor detects the current of the magnetic field generator, and is turned on when the current is raised by the control of the S1 gate control, and turned off when the current is lowered. Here, hysteresis control that outputs an on / off command with a width of an allowable deviation with respect to the current command is assumed. However, since it can be implemented by other current control methods, description of the electronic and control systems is omitted.

  The input from the external power supply has a simple rectified output of AC power connected in parallel to the voltage source capacitor. Since the AC inflow power is determined by the series reactance including the transformer on the AC side and the voltage of the voltage source capacitor, if the capacitor voltage is constant, the input power is also constant. For the magnitude of the electric power, an AC side voltage such as a secondary voltage tap of the transformer may be selected.

  In the magnetic field generator during high repetition operation of the high energy particle accelerator, its magnetic energy is about several MJ, and it is not as large as several GJ like the toroidal magnetic field coil of the fusion experimental device JT-60, but it is excited and demagnetized at intervals of several seconds. Since it repeats, the power peak is as large as several MW, which is large. In this pulse magnetic field generating power source, an SMES coil is planned as an energy storage means.

A case where the circuit of FIG. 1 is applied will be described by simulation. In the accelerator, the magnetic field strength is increased synchronously with the acceleration of the particles. When the velocity of the particle reaches the specified value, the particle is discharged, and the magnetic field is demagnetized to the original value in preparation for the next acceleration. The magnetic field coil synchronously increases the current and decreases for the next preparation, and repeats this.

FIG. 2 shows the conditions of the simulation circuit. As an example, it is composed of six MR (main ring) magnetic field generators of a synchrotron particle accelerator. Inductance L2 = 1.6 [H] and electrical resistance is R = 0.7Ω. The maximum current value is 1.6 kA. Assuming that the start-up time is 1 second, the magnetic energy is 2 MJ. Since the peak voltage of this power supply is immediately before the end of rising of the magnetic field current and the voltage is Vmax = R × I + LdI / dt, Vmax = 1120 + 1.6 × 1600 = 3680 V = 3.6 kV. The power at this time is Pmax = 3.6 kV × 1.6 kA = 5.76 MW. It is impossible to receive this power directly from the grid power system.
Therefore, by using the SMES coil as an energy storage device, it is possible to further increase the repetition speed when the power peak is leveled.

FIG. 3 shows the simulation calculation results of the example. The magnetic field generating coil current is tracked and increased by the current control chopper circuit in accordance with the current reference value Vrf that increases linearly. The voltage source capacitor is kept at 6 kV under the control of the low speed chopper. Therefore, the external power is constant.
The upper graph shows Icoil: current of the magnetic field generating coil, I (Lsm): current of the superconducting coil, and Vrf: target coil current value.
The middle graph shows Vc: Voltage of the voltage source capacitor (controlled to 6 kV), Vcoil: Coil applied voltage (moves up and down violently)
The lower graph shows W1: power from the external power supply (a constant value of 1 MW or less), W3: output power from the high-speed chopper, the maximum value is 7.5 MW, and minus is about 7 MW.

In an accelerator, which is a representative of a pulsed magnetic field generator, a plus or minus power fluctuation of several MW is provided with a magnetic energy storage device, and the chopper power supply voltage source capacitor is powered to continuously operate with constant power reception. It becomes possible.

In a pulsed magnetic field generator, it can be realized by switching taps between a diode rectifier and a transformer without performing advanced constant power control to receive constant power from an external power supply, and changes in flicker, harmonics, and power factor High speed repetition of pulse operation is possible without any problem. According to this method, it is possible to reduce operating power peaks and power charges of pulsed magnetic field application devices such as medical particle accelerators, and to eliminate disturbance to the power environment.

1 High-speed chopper 2 Low-speed chopper 3 Voltage source capacitor C
4 Diode power supply 5 Gate control device

Claims (2)

In a pulse magnetic field generator driven by magnetic energy as an energy storage source, as a method of receiving power from an external power source, a DC power source consisting of a transformer and a diode rectifier is connected in parallel to the voltage source capacitor of the current control chopper from the external power source. A pulsed magnetic field generating power source characterized in that it is connected and replenished without pulsating power necessary for operation. In a pulsed magnetic field generator driven by using magnetic energy as an energy storage source, a high-speed on / off chopper circuit is used to control the current of the magnetic field generating coil with high accuracy, while a low-speed on / off chopper circuit is used for the magnetic energy storage coil. A pulse magnetic field generating power source characterized by performing voltage control of a voltage source capacitor.