JPS62141961A - Power converter - Google Patents

Abstract

PURPOSE:To effectively limit an overcurrent by a fuse by connecting the fuse in series with a plurality of semiconductor elements which form arms, and connecting nonlinear resistors in parallel with the series circuit. CONSTITUTION:The arm of a power converter is composed by connecting in series unit circuits 1-m in which nonlinear resistors 31-3m are connected in parallel with series connecting circuit of fuses 11-1m and thyristors 21-2m. When the thyristors 21-2m become overcurrent states during their energization, the fuses 11-1m start melting, and when the melting of the fuses if proceeded, the fuses 11-1m generate arc voltages corresponding to the circuit voltage. The arc voltages generated from the fuses 11-1m are suppressed to the limiting voltages of the resistors 31-3m by the operations of the resistors 31-3m.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a high-voltage system in which semiconductor elements are connected in series and parallel to form an arm, such as a thyristor converter for DC power transmission or a power supply for a coil that controls the plasma of a nuclear fusion device. The present invention relates to a power converter for high voltage and large current, and particularly to a power converter that can protect semiconductor elements from overcurrent.

[Technical background of the invention and its problems] As an overcurrent protection method for power conversion devices using semiconductor elements such as diodes, thyristors, and transistors, a general method is to connect a fuse in series with the semiconductor element. .

Examples of purposes for using fuses include:

(1) The overcurrent withstand capacity of the semiconductor element is selected to be larger than that of the fuse, and when an overload or short-circuit current flows, the fuse is blown to cut off the current, thereby preventing destruction of the semiconductor element.

(2) In a device in which multiple semiconductor elements are connected in parallel, if one of the semiconductor elements connected in parallel is damaged, a fuse connected in series with the damaged semiconductor element may be damaged. By fusing and disconnecting the damaged semiconductor element from other healthy semiconductor elements in the electrical circuit, it is possible to continue operating the device.

(3) As the current capacity R of the power converter increases, the current flowing through the semiconductor element also increases, and if a current exceeding the specified value flows, the semiconductor element will explode, resulting in an arc blowing out and sometimes a fire. This may result in a serious accident. In order to prevent such an explosion of the semiconductor device, it is necessary to limit the short circuit current at high speed using a fuse.

However, fuses cannot be applied to high-voltage power converters for the reasons described below. −
For example, in a thyristor converter for DC power transmission, the DC voltage is about 250 kV, and there is no single fuse that can withstand such high voltage.It is conceivable to connect multiple fuses in series, but each Due to the difference in the fusing characteristics of the fuses, the arc voltage shared when each fuse blows is not uniform, and the voltage that is higher than the fuse's unique ability is shared, making it impossible to expect a current limiting effect. Therefore, in high-voltage thyristor converters, overcurrent protection does not use a fuse, but rather by gate operation of the thyristor.
That is, it relied only on gate shifts or gate plots. In the thyristor converter for DC power transmission, the DC current rating is about 3 kA, so there was no need for the above-mentioned purpose of use of the fuse (2113).

However, in recent years, in power conversion equipment for nuclear fusion, etc., a DC voltage rating of several tens of kV or several hundreds of kV is required, and technology that makes it possible to apply fuses according to the above-mentioned purposes (2) and (3) of fuse use has been developed. , power transformer IIAv
This was an important issue in terms of increasing the current capacity of the 4-position.

[Object of the Invention] An object of the present invention is to enable the application of a fuse to a high-voltage, large-current power converter, and to provide a highly reliable and highly safe power converter.

[Summary of the Invention] In order to achieve the above-mentioned object, the present invention provides a power conversion device in which a plurality of semiconductor elements are connected in series to form an arm, in which a fuse is connected in series to each semiconductor element, A series circuit of each fuse and a semiconductor element is used, or a nonlinear resistor is connected in parallel to each fuse to ensure the arc voltage when the fuse blows, so that the fuse can reliably limit overcurrent. This is what I did.

[Embodiment 1 of the Invention The present invention will be described below with reference to an embodiment shown in FIG. In Figure 1, 11, 12...1m are fuses, 21, 22... ...2m is a semiconductor element, for example, Cyrisk, 3). ．． 32. ...3m is a nonlinear resistance.

Here, m is the number of series.

As shown in FIG. 1, unit circuits 1, 2. ...m are connected in series.

In such a configuration, the operation of the thyristors 21, 22 . . . 2m becomes energized and the current drops out, the fuse 1112. ...1m begins to fuse, and as the fuse progresses, each of the fuses 11.12°...1m generates an arc voltage commensurate with the circuit voltage. Fuse 1
1,12. ... Each arc voltage generated by 1m is suppressed to the limiting voltage of the nonlinear resistor by the action of the nonlinear resistor 3)゜32, ...3m, and it is no longer effective as a fuse. Can exhibit current limiting effect.

Fig. 2 shows an example of a real box, in which unit circuits 1, 2, 2, 3, 3, 3, 4, 3, 4, 3, 3, 3, 4, 3, 3, 4, 3, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 2, etc were each each consisted of a fuse and a nonlinear resistor were connected in parallel, and a thyristor was connected in series with them. ...m are connected in series. Same as Figure 1 (hanging, fuse 11°12,...1m
The arc voltage generated by nonlinear resistance 3), 32.・・・
・Suppressed to voltage limit of 3m.

FIG. 3 shows an embodiment in which the present invention is applied to a high-voltage, large-current power conversion device in which 7!2 thyristors are connected in series. In FIG. 3, n represents the number of parallel lines. Figure 3 is also called a mesh connection, and is the unit circuit 1 in Figure 1.
,2. . . . nl series-connected fuses and thyristors are connected in parallel.

Nonlinear resistance 3). 32...3m are commonly connected in parallel to the unit circuit, but they may be divided into n pieces in parallel.

The present invention is even more effective in a high-voltage, large-current power converter as shown in FIG. That is, since the fuse can be applied, when the thyristors connected in parallel are damaged, it is possible to continue operating the device by disconnecting the damaged thyristor by blowing the fuse. Explosion of the thyristor can be prevented by limiting the short circuit current flowing through the thyristor using a fuse.

FIG. 4 shows another embodiment in which the present invention is applied to a high-voltage, large-current power conversion device in which a plurality of thyristors are connected in series and parallel. FIG. 4 is also called a string connection, in which n circuits shown in FIG. 1 are connected in parallel. The action of the fuse nonlinear resistance is the same as in the case of FIG. 3, but by connecting a plurality of thyristors in series, variations in the forward voltage drop characteristics of the thyristors are canceled out, and the unit circuit 1.2. . . . The characteristic is that the current sharing between each n is improved.

[Effects of the Invention] As described above, according to the present invention, a fuse can be applied to a high voltage power converter, thereby providing a highly reliable and safe power converter.

[Brief explanation of drawings]

FIG. 1 is a connection diagram showing only the main parts of the power conversion device according to the present invention, and FIGS. 2 to 4 are connection diagrams of other different embodiments showing only the main parts of the power conversion device according to the invention. be. 11-1n, 111-11IIn... Fuse, 21
~2Ill, 211~2IIIn... Cyrisk, 3
)~3m...Nonlinear resistor. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (3)

[Claims] (1) In a power conversion device in which a plurality of semiconductor elements are connected in series to form an arm, a fuse is connected in series to each of the semiconductor elements, and a nonlinear resistor is connected in parallel to each series circuit of the fuse and semiconductor element. A power conversion device characterized by being connected to. (2) The power conversion device according to claim 1, wherein the nonlinear resistor is connected in parallel only to each of the fuses. (3) In a power conversion device in which a plurality of semiconductor elements are connected in parallel and a plurality of parallel circuits are connected in series to form an arm, a fuse is connected in series to each of the semiconductor elements, and a fuse is connected to each parallel circuit. A power conversion device characterized by connecting nonlinear resistors in parallel.