JPS6058839B2 - Plasma current control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma current control device that can maintain plasma for a long time in a nuclear fusion device or the like.

In plasma devices such as tokamaks that aim to generate electricity through nuclear fusion, the plasma current that flows through the plasma plays an important role in confining the plasma within a vacuum vessel. Fluctuations in the magnitude of this plasma current cause fluctuations in the plasma itself. If the plasma collides with the inner wall of the vacuum vessel due to plasma fluctuations, the energy of the plasma is lost, making it difficult to maintain the plasma for a long time. Furthermore, rapid fluctuations in plasma are extremely dangerous because they generate excessive induced voltage and electromagnetic stress in various parts of the plasma device. The present invention was carried out based on the above reasons, and an object of the present invention is to provide a plasma current control device that can safely maintain plasma for a long time by controlling the plasma current.

The present invention will be described below based on an embodiment shown in the drawings. In a tokamak device, plasma is created inside a torus-shaped vacuum vessel. Therefore, the plasma is also annular, and a plasma current (hereinafter referred to as Ip) is passed in the axial direction of the annular ring, so that the plasma forms one circuit, that is, the plasma circuit configuring plasma circuit 1 in FIG. 1, a current transformer coil 3 is installed. A current transformer coil current (hereinafter referred to as If) is supplied to the current transformer coil 3 from a control power supply device 5. A change in If excites Ip by electromagnetic induction. In other words, the current transformer coil 3 and the plasma circuit 1 correspond to the primary and secondary windings of the transformer.
The current transformer coil voltage (hereinafter referred to as Vf) proportional to the input voltage is outputted. In other words, the controlled power supply device 5 is realized by a thyristor device or the like that has a power amplification function and performs phase control. If is detected by the coil current detector 4. Further, Ip is detected by a plasma current detector 2. As a method to detect IP,
A coil called a Rogowski coil is usually placed around the plasma to detect the magnetic field created by Ip.
A method of calculating is performed. The detected values of If and Ip are input to the control adjustment section 6 via a feedback loop.

The control adjustment section 6 performs calculations such as addition, subtraction, multiplication, division, integration, and differentiation, and various judgments on these feedback amounts and reference values given from the outside, and outputs U to be applied to the control power supply device 5 . The control adjustment section 6 has an arithmetic function as described above, so an analog computer or a digital computer is used. Further, the configuration of the present invention will be described in detail using the block diagram shown in FIG.

The controlled object characteristic 7 is the plasma circuit 1 in FIG.
The characteristics of the current transformer coil 3 and the current transformer coil 3 are expressed by a transfer function. The controlled object characteristic 7 is a transfer function 8 between If and Ip, Ip
, If transfer function 9, current transformer coil transfer function 11, and If adder 10. If, Ip transfer function 8 is I
With f as input and Ip as output, Ip, If transfer function 9 is
This is an incompletely differentiated transfer function with Ip as input and current transformer coil reverse induced current (hereinafter referred to as 1f2) as output. The current transformer coil transfer function is a first-order lag type transfer function in which Vf is input and the current transformer coil characteristic current (hereinafter referred to as 1f1) is output. Ifl and If are added in an If adder 10 to produce If. The controlled power supply device 5 is expressed by a dead time and a first-order delay, as shown by a power supply characteristic 14.

In the power supply characteristic 14, u is the input and Vf is the output. The coil current detector 4 has coil current detection characteristics 12,
If is input, and If detection value (hereinafter referred to as 1fd) is output. Plasma current detector 2 has plasma current detection characteristics 1
3, Ip is input, and p detection value (hereinafter referred to as 1pd) is output. Coil current detection characteristics 12
, and the plasma current detection characteristic 13 are all expressed by J in first-order delay and dead time. Next, the characteristics of the control adjustment section 6 will be explained using a transfer function.

The control adjustment section 6 includes a coil current control section 16, a coil current comparison section 17, a plasma current control section 18, a plasma current comparison section 19, and a 1p reference value setting section 20. The coil current control section 16 uses a coil current comparison section 17 to determine the coil current reference value (hereinafter referred to as 1f0) and If
The difference obtained by comparing d with d is input, and a proportional integral operation is performed on this to output u.

Therefore, the coil current control portion 16, control power supply characteristics 1
4. The current transformer coil characteristic 11 and the coil current detection characteristic 12 constitute a coil current control feedback loop 21.
The plasma current control section 18 is connected to the plasma current comparison section 1.
9, the plasma current reference value (hereinafter referred to as 1p0) and Ipd
The difference obtained by comparing is input, and the proportional-integral calculation is performed twice, and IfO is output.

Therefore, the plasma current control characteristic 18, the coil current feedback loop 21, the transfer function 8 between If and Ip, and the plasma current detection/output characteristic 13 constitute a plasma current control feedback loop 22. Reference value setting part 20
outputs a plasma current reference value set in advance or given from the outside as IpO.

However, by comparing and determining Ipd and IpO, IpO and Ip
When the difference in d is greater than the preset value ER,
Change the settings of IpO.

Next, the operation of the present invention will be explained.

The coil current control feedback loop 21 controls the coil current control section 16 so that Ef becomes zero given IfO.
operates, so If tries to match IfO. That is, If is controlled. The plasma current control feedback loop 22 has a transfer function 8 between If and Ip because the plasma current control section 18 is composed of a double proportional integral.
Even if is a differential form, this differential form is canceled by one of the proportional integrals, and the other proportional integral remains, so the loop can be made into an integral form. Therefore, for a given IpO, the plasma current control feedback loop 22 is set so that Ep becomes zero, that is, Ip matches IpO.
works.

The reason for adding a negative sign to the above equation (2) is as follows.
This is because the phase is reversed in the transfer function 8 between If and Ip.
The reference value setting section 20 automatically changes the setting of IpO when the difference between IpO and Ip is too large, and prevents saturation of the control system, generation of excessive voltage, and sudden changes in Ip associated therewith. Nuclear fusion devices have recently been developed as a future energy source in countries around the world, and tokamak devices are considered the most promising. In tokamak devices, flowing plasma current is essentially important for plasma confinement. Therefore, controlling plasma current according to the present invention is particularly effective for tokamak devices. In a tokamak device, in addition to the current transformer coil described above, various coils such as a toroidal coil, a vertical magnetic field coil, and a quadrupole magnetic field coil are installed for each function. In FIGS. 1 and 2, only the current transformer coils directly related to plasma current control are considered;
Other coils were omitted. Although the present invention has been described in detail above, the present invention can also be similarly applied to the following cases.

That is, (1) the coil current control section 16, the coil current detection characteristic 12, and the If comparison section 17 are removed and u=I
When fO.

In other words, if minor control of If is not performed. (Ii) When the program control reference value 1fp is added to the coil current comparison section 17 from the outside to manipulate If.

(iii) Plasma properties such as plasma resistance η9 change significantly.

When changing the proportional gain and integration time of the plasma current control section 18 in accordance with changes in plasma properties. In this way, according to the present invention, Ip can be controlled with high accuracy by feedback control of Ip.

Furthermore, since feedback control of If is performed, If is controlled even in the event of a coil short circuit accident. Therefore, it is advantageous in terms of protecting the power supply device. Furthermore, Ip<! :． 1
When the difference in PO is too large, a sudden change can be avoided by changing the setting of 1p0, so that it is possible to provide a plasma current control device with many benefits, such as being useful for protecting the device and preventing danger.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of the present invention, and FIG. 2 is a block diagram illustrating the detailed explanation and operation of the present invention. 1... Plasma circuit, 2... Plasma current detector, 3... Current transformer coil, 4...
...Coil current detector, 5...Control power supply device,
6...Control adjustment part, 7...Characteristics of controlled object, 8...■F, Ip transfer function, 9...
...Transfer function between Ip and If, 10...If addition...
Calculation section, 11...Current transformer coil characteristics, 12...
・Coil current detection characteristics, 13... Plasma current detection characteristics, 14... Control power supply characteristics, 16...
・Coil current control part, 17... Coil current comparison part, 18... Plasma current control part, 19...
. . . Plasma current/comparison section, 20 . . . Reference value setting section, 21 . . . Coil current control feedback loop, 22 . . . Plasma current control feedback loop.

Claims (1)

[Claims] 1. In a plasma device equipped with a current transformer coil that excites plasma current, a control power supply device that inputs a power control signal and supplies a current transformer coil voltage to the current transformer coil;
a coil current detector that detects the current of the current transformer coil; a plasma current detector that detects the plasma current;
The output of this plasma current detector is input through a plasma current feedback loop and compared with a set plasma current reference, and this error is subjected to plasma current control calculations to determine the coil current reference value of the current transformer coil. a control adjustment section that compares this coil current reference value with the output of the coil current detector input via a coil current feedback loop, performs a coil current control calculation on this error, and outputs the power supply control signal; A plasma current control device consisting of.