JPH01138491A - Plasma current controller - Google Patents

Abstract

PURPOSE:To control a plasma current by providing a selection part which inputs the output signal of a current limitation control part and a signal corresponding to the terminal voltage across an ohm heating coil and selects and outputs one of them. CONSTITUTION:A current detector 30 detects the current IOH of the ohm heating coil 3, the current limitation control part 31 amplifies the sum of said current and the value corresponding to a permissible current IN, and its output signal x2 is compared with the output signal x1 of a plasma control part 22. The result is inputted to the selection part 32 which selects and outputs the smaller current, and the output voltage V2 of a 2nd thyristor converting device 21 is adjusted according to the output signal x3 of the selection part 32.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an improvement of a plasma current control device for a tokamak type nuclear fusion device.

(Prior Art) First, the basic principle of plasma current control in a tokamak-type nuclear fusion device will be briefly explained.

FIG. 3 is a schematic diagram for explaining the principle of plasma current control in a tokamak type nuclear fusion device. In FIG. 3, reference numeral 1 denotes a vacuum vessel in which plasma 2 is generated. In a tokamak-type fusion device, an ohmic heating coil (hereinafter referred to as
(abbreviated as OH coil) 3 is provided, and this OH
A magnetic flux Φ is created in the iron core 4 by the current IOH flowing through the coil 3. (We also consider an air-core tokamak-type fusion device without the iron core 4, but the principle is the same.) Now, if we apply a current IOH to the OH coil 3 as shown in Fig. 4(a), we can see the difference from Fig. 3. As shown in FIG. 4(b), a current transformer is formed in which the OH coil 3 is the primary winding and the plasma 2 is the secondary winding (the number of turns is 1), so the plasma current Ip is as shown in FIG. flows.

That is, by changing the magnitude of OI (voltage VOH applied to the terminal of the coil 3) and controlling the current IOH flowing through the OH coil 3, the plasma current Ip can be controlled.

FIG. 5 is a diagram showing the configuration of a conventional plasma control device, and FIG. 6 is a diagram for explaining its operation.

First, the switch S is turned ON and the switch S is turned OFF, and the current controller (ACR1) 10 causes the OH coil 3 to receive a current I, as shown in period A of C in FIG.
OH is made to flow by the first thyristor conversion device 11 to a predetermined value. 13 is a phase controller. In this case, period A
Since the current change rate is sufficiently small compared to period B, which will be described next, almost no induced voltage is applied to the plasma 2, and therefore almost no plasma current Ip flows. Next, at time t1, the first thyristor conversion device 11 is set to Bino 4 spare (BPP), and the switch S1
When , the electric current of OH coil 3 becomes C in Fig. 6.
As shown in period B of FIG.
rise as shown in . Also the time.

Then, the switch S is turned on and the second thyristor converter 21 is utilized to set the plasma current reference value Ipref and the output voltage of the Rogowski coil 24 (which is the differential value of the plasma current Ip) as shown in FIG. plasma current detection value I detected by integrating the plasma current (proportional) with an integrator 25
Plasma control unit (APR) 2 that amplifies the difference with PD
Based on the signal x1 output from the phase controller 23
The firing phase of the second thyristor converter 21 is controlled by the dart pulse of , and the output voltage (1) of this thyristor converter 2 is adjusted. Since switch S is closed, O
V at the terminal of H coil 3. , = -V, and the plasma current I
p is controlled. At time t, when the second thyristor converter f21 is set to pino f spare (EPP), O
The current IOH of the H coil 3 decreases as shown in the period C of FIG.
It decreases and disappears as shown in d in the figure.

(Problems to be Solved by the Invention) By the way, for some reason, for example, impurity ions are mixed into the plasma 2, and the temperature of the plasma 2 is lower than the expected value.
If the plasma resistance Rp is larger than the expected value, the slope of the OH coil current IOH required to flow the same plasma current Ip must be large, as shown in FIG. Therefore, in the conventional plasma control device shown in FIG. 5, if an attempt is made to forcibly control the plasma current Ip to match the reference value Iprsf in such a case, at a certain time tx as shown in FIG. The absolute value of the current IOH of the OH coil 3 becomes large as well as the allowable current In of the OH coil 3 or the second thyristor converter [21], and there is a risk of damaging these devices.

In addition, even if the plasma resistance Rp is as expected, if the BPP signal does not come even at the stop time t, the current IOH at the time ty will become as shown by the thick dotted line in FIG. There is a possibility that the absolute value of In may become larger than the allowable current In.

The purpose of the present invention is to prevent the terminal voltage VO of the OH coil from increasing when the absolute value of the current IOH is less than or equal to the allowable current In, as in the conventional case.
H is controlled to a value necessary for plasma control, and the current IOH is
It is an object of the present invention to provide a plasma current control device capable of restricting the absolute value of the current IOH so that it does not increase any further once the absolute value of the current IOH reaches the allowable current In.

[Structure of the invention]

(Means for solving the problem) In order to achieve the above object, the present invention provides a signal x corresponding to the terminal voltage of the OH coil for controlling the plasma current.
1, and the output signal x of the current limit control unit that limits the absolute value of the current IOH of the OH coil so that it does not exceed the allowable value In.
2 to the selection section, and the selection section selects the signal x1 and the output signal x2 so that the absolute value of the OH coil current IOH is the allowable value I.
The signal x1 is selectively outputted as the signal x3 in a range where n is not exceeded, and the signal x2 is selectively outputted when the value exceeds n, and the amount corresponding to the terminal voltage of the OH coil is controlled based on this signal x1. ing.

(Function) Therefore, in the plasma current control device of the present invention, the absolute value of the signal x1 corresponding to the terminal voltage of the OH coil for controlling the plasma current and the current IOH of the OH coil does not exceed the allowable value In. The output signal x2 of the current limit control section is input to the selection section, and the selection section selects the signal Xl and the output signal x2 as the signal X, as long as the absolute value of the OH coil current IOH does not exceed the allowable value In. but,
When the voltage is exceeded, the signal xt is selectively outputted as the signal x3, and the amount corresponding to the terminal voltage of the OH coil is controlled based on the signal x1.

(Example) An embodiment of the present invention shown in the drawings will be described below.

FIG. 1 shows an example of the configuration of a plasma current control device according to the present invention, and the same parts as those in FIG. 5 are given the same reference numerals, and the explanation thereof will be omitted. What is different in Fig. 1 from Fig. 5 is that the current l011 of the OH coil 3 is detected by the current detector 30, and the value corresponding to the allowable current In (this is also indicated as In in Fig. 1) is detected by the current detector 30. ) is amplified by the current limit control section 3, and inputted to the selection section 32 which compares the magnitude of the output signal x2 and the output signal x1 of the plasma control section 22, selects the smaller one, and outputs it. , the output voltage V of the second thyristor conversion device 21 is adjusted based on the output signal x3 of the selection section 32.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be explained.

As can be seen from Fig. 7, when the plasma resistance Rp is larger than expected, or when the pie/mother spare (BPP) command does not arrive at time tX, the current IOH of the OH coil 3 changes to the negative side ( That is, the current I shown in the main circuit of FIG.
(in the opposite direction to the OH arrow), the allowable current In is exceeded. Therefore, consider the case of Ion (0, In) O in FIG. If, l
If n=50kA, IO,=-55kA, In+I
□B=50+(-55)=-5kA, and x, <0.

On the other hand, as shown in FIG.
l) It is O. Therefore,! ! < x I, and the output signal x2 of the selection section 32 is X.

Since the output voltage VT of the second thyristor conversion device 21 is negative, the current Ion is increasing (in other words, from -55 kA to 0). ,
In other words, the absolute value moves in the direction of decreasing. When the absolute value on the negative side of this current IOH decreases to l0H=-50kA, In+Ioi=50+(-50)=OkA, px,=
It becomes O. Furthermore, when the absolute value of the negative side of the current IOH decreases to, for example, IOH''-49.5 kA, In+Ioi
=50+(-49,5)=0.5kA #)! ! >0
becomes. For example, if the value of X at this time becomes equal to xl, the absolute value of the negative side of the current IoH will no longer decrease, and the current Ion will be controlled to -49.5 kA (constant value). That is, the current Ion is controlled to be constant with an offset of 0.5 kA. The value of this offset can be adjusted as appropriate by adjusting the dyne of the current limit control section 31. As you can see from the above explanation, if the absolute value of the current IoH is 49.5 kA or less! +<Xt. Since X appears in the output signal x3 of the selection section 32, the fifth
Similarly to the conventional method shown in the figure, the output signal x of the plasma control section 22
Plasma control is performed based on 1.

In other words, if the dyne of the current limit control section 3 is adjusted to such an extent that the above offset can be ignored, conventional plasma control will be performed until the current Ion exceeds the allowable current In (on the negative side), but if some If the current Ion exceeds the allowable current In (on the negative side) for some reason, the current is limited and the current exceeding the allowable current In is applied to the OH coil 3 and the second thyristor converter 21. This can prevent water from flowing and causing damage. This state is shown in FIG. 2.

Next, other embodiments of the present invention will be described.

In the embodiment of FIG. 1, the signal X is the plasma current I
Although a case has been shown in which the plasma control unit 22 is provided as an output signal of the plasma control unit 22 configured to perform feedback control of It is clear that the present invention can be applied even if a feedback control loop is configured based on the above-described feedback control loop, or even if the signal x1 is configured to output the signal x1 as a pre-programmed amount rather than as a result of feedback control. In short, some closed loop f
Or from the plasma control section 22 that performs open loop control,
When the signal corresponding to the terminal voltage of the OH coil 3 is given as xl, the present invention can be applied as is. Note that the various control signals ("1"
t
There are various combinations of codes for the phase controller 23, etc.), and the addition/subtraction codes of each part in FIG. However, since these procedures are well known in the field of control systems, their explanation will be omitted here.

Further, although the configuration diagram in FIG. 1 is drawn as if it were an analog control system, those skilled in the art will easily understand that it can be applied to a digital control system without any problem.

〔Effect of the invention〕

As explained above, according to the plasma current control device of the present invention, the signal x2 corresponding to the terminal voltage of the OH coil for controlling the plasma current and the absolute value of the current IOH of the OH coil do not exceed the allowable value In. The output signal x2 of the current limit control section that limits the current is input to the selection section, and the selection section selects the signal Xl and the output signal When x2 is exceeded, signal x2 is selectively output as signal x2, and the amount corresponding to the terminal voltage of the OH coil is controlled based on signal x1. It is possible to control the plasma, and to limit the OI (coil current ■.H so that it does not exceed the allowable value In). It is possible to control the plasma current in a tokamak-type fusion device, which is difficult to control.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a plasma current control device according to the present invention, FIG. 2 is a diagram for explaining the effects of the embodiment, and FIGS. 3 and 4 (a). (b) is a diagram used to explain the principle of plasma current control in a tokamak and fusion device, Figure 5 is a configuration diagram showing an example of a conventional plasma current control device, and Figure 6 is a normal diagram in Figure 5. FIG. 7 is a time chart diagram for explaining the operation of the conventional method, and FIG. DESCRIPTION OF SYMBOLS 1... Vacuum vessel, 2... Plasma, 3... OH coil, 4... Iron core, 11.21... Thyristor conversion device, 22... Plasma control part, 13.23... Phase controller, 25... Integrator, 30... Current detector,
31... Current limit control section, 32... Selection section. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 3

Claims (2)

[Claims] (1) A signal x_1 corresponding to the terminal voltage of the ohmic heating coil necessary for controlling the plasma current is provided, and the terminals of the ohmic heating coil are connected to generate a voltage in response to the signal x_1. a thyristor conversion device;
a phase controller for controlling the firing phase of the thyristor conversion device; a means for detecting a current I_O_H flowing through the ohmic heating coil; means for providing an allowable current I_n of the current I_n;
A current limit control section that limits O_H so that it does not exceed the allowable current I_n, and a selection section that inputs the output signal x_2 of this current limit control section and the signal X_1 and selects and outputs one of the two. A plasma current control device characterized by comprising: (2) The selection unit outputs the signal X_1 in the range where the ohmic heating coil current I_O_H does not exceed the allowable current I_n,
The plasma current control device according to claim 1, wherein the plasma current control device is configured to output the signal x_2 when the ohmic heating coil current I_O_H exceeds the allowable current I_n.