JPH0678544A - Detecting device for element failure of semiconductor converter - Google Patents

Abstract

PURPOSE:To obtain a cheap, high-reliability failure detector for semiconductor devices with a fewer number of components, by measuring currents flowing is connection wires which connect between parallel elements for mesh connection. CONSTITUTION:Direct current transformers 31 and inserted into connection wires 21 and 22 for connecting between parallel elements mutually, and it is judged by the use of a judging means 5 that a certain element is malfunctioning when the output values of these direct current transformers 31 and 32 exceed a specified value. Consequently, it becomes possible to perform failure detection of all the elements by the use of the direct current transformers 31 and 32 fewer than the number of the elements. Reliability increase of a detector and cost reduction owing to the reduction of the number of circuit elements required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor conversion device for detecting a failure of a semiconductor device such as a large-capacity rectifier device in which a large number of semiconductor devices are used in series and parallel connection such as a rectifier device for aluminum electrolysis. The present invention relates to a device failure detection device.

[0002]

2. Description of the Related Art In a power converter device such as a rectifier or an inverter which uses a semiconductor element such as a diode or a thyristor, if one semiconductor element in one arm cannot bear the voltage of the apparatus, the element is connected in series. The rated voltage and rated current of the device are satisfied by connecting them and connecting the elements in parallel when the current is large. As described above, when the capacity of the semiconductor device is large, a configuration in which semiconductor elements are connected in series and parallel is adopted, but at that time, a mesh connection in which parallel elements are connected by a connection line to form a mesh shape is used. It may be adopted. (Electrical Engineering Handbook (1988 edition) P.749) As a device for detecting a failure of a semiconductor element connected in series, a method of monitoring a burden voltage of the element is adopted. That is, when a semiconductor element fails, a short circuit occurs, so that no voltage is applied between the terminals of the failed element even when the element is in the off state.Therefore, the failure is detected by detecting this, and at the same time the failure element can be identified. It is possible.

FIG. 5 is a circuit diagram showing a rectifier of a conventional rectifier adopting a mesh connection. In this figure,
The three terminals U, V, W on the left side are connected to the secondary side of a rectifier transformer (not shown), and the DC load is connected to the two terminals P, N on the right side via a smoothing reactor (not shown). . The illustrated rectifier circuit has a three-phase bridge connection and is composed of six arms. In this figure, reference numeral 1 is attached to only one of the arms. The arm 1 has three diodes 11, 12, 13 and 14, 15, 16 respectively.
Each is connected in series to form two series circuits, and these two series circuits are connected in parallel. Such a configuration is abbreviated as 3 series and 2 parallel.

Adjacent diodes are connected by connecting lines 21 and 22 for mesh connection. By the way, the diodes 11 to 16 of the arm 1 constituting the rectifier
Also, the diodes of other arms not labeled have a very low probability but may fail, and an element failure detection device for detecting the failure may be provided. The detection method is to monitor the voltage across the terminals of each of the diodes 11 to 16 as described above. When the diodes are normal, a voltage is applied between the terminals during the off period when a voltage is applied in the opposite direction, but a failure occurs. In the case of, the voltage is practically the same as a short circuit, so the voltage between the terminals remains zero even during the off period. A failure is detected based on the presence / absence of the inter-terminal voltage in the off period of the diodes 11 to 16. As a specific failure detection device, for example, a light emitting diode is connected in parallel to each diode, and the light emitted from this light emitting diode is guided to a detection device through an optical fiber and converted into an electric signal by a light receiving element. , When the diode is off, check whether this electric signal is in the high state or the low state, and when it is high, it is regarded as normal, and when it is low, it is considered as a failure.

[0005]

In the device failure detection system as described above, it is necessary to provide a light emitting diode for detection and an optical fiber, a light receiving device and a judging means associated therewith to all the diodes. It is necessary to operate the judging means in synchronism with turning on and off, and as a result, there is a problem that the number of parts increases, the apparatus becomes complicated and the apparatus becomes expensive, and the reliability is lowered.

An object of the present invention is to solve such a problem and to provide a failure detecting apparatus for a semiconductor device which has a small number of parts and is therefore highly reliable and inexpensive.

[0007]

In order to solve the above-mentioned problems, according to the present invention, there is provided an element failure detection device for a rectifying device, in which semiconductor elements connected in series and parallel are mesh-connected. The connection line to be formed is provided with a DC current transformer, and it is provided with a determination means for determining that there is a faulty semiconductor element when the output value of these DC current transformers exceeds a predetermined value. When the absolute value of the output value of each DC current transformer is larger than a predetermined value and the direction is positive,
Outputs of the state determination means for determining three states, that is, the state where the absolute value is less than or equal to the predetermined value and the state where the absolute value is greater than the predetermined value and the direction is negative, and the state determination means corresponding to each of the DC current transformers. An element specifying means for specifying a semiconductor element having a failure from a combination of three states of signals is provided.

[0008]

In the structure of the present invention, a DC current transformer is provided on the connecting line connecting the parallel elements to each other, and when the output value of the DC current transformer exceeds a predetermined value by the judging means, any one of the elements is turned off. By determining that a failure has occurred, it is possible to detect the failure of all the elements with a DC current transformer that is smaller than the number of semiconductor elements. In addition, when the absolute value of the output value of each DC current transformer is larger than the predetermined value and the direction is positive, when the absolute value is less than the predetermined value, and when the absolute value is larger than the predetermined value and the direction is negative By detecting the three states of (1) and (2) by the state determining means, and identifying the faulty semiconductor element by the element identifying means from the combination of the output signals of the state determining means corresponding to each DC current transformer, the failure element can be found. Make it quick and easy to replace it.

[0009]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a circuit of one arm showing an embodiment of the present invention.
5, which corresponds to the arm 1 of FIG. 5, the same circuit elements as those of FIG.
In this figure, the connection lines 21 and 22 are provided with DC current transformers 31 and 32, respectively, and the currents flowing through the connection lines 21 and 22 are measured. As the DC current transformers 31 and 32,
Since it is necessary to insulate the high-voltage connection lines 21 and 22, a shunt resistance or the like is not appropriate, and an insulating DC current transformer such as CT is appropriate.

A surge protection circuit 17 connected in parallel to the diodes 11 and 14 and another surge protection circuit having the same circuit configuration without reference numerals are omitted in FIG. 5 and are also provided in a conventional rectifier circuit. It is what has been. Adopting the mesh connection has an effect that the surge protection circuit 17 can be commonly used for the two diodes 11 and 14.

Letting the output signal of the DC current transformer 31 be that of the DC current transformer 32, these two electrical signals,
Is input to the determination circuit 5. The determination circuit 5 is the adder 5
1, the filter 52 and the overcurrent detector 53, the electrical signal input to the determination circuit 5 is the adder 5
The surge protection circuit 1 is added by 1 and is added by the filter 52.
When a signal exceeding a predetermined value is input to the overcurrent detector 53 after cutting the harmonic components such as the current flowing through 7, it is determined that a failure has occurred. Even if all the diodes are normal in the connection lines 21 and 22, the current imbalance component between the parallel elements flows. Therefore, the overcurrent detector 53 should not operate with respect to such a current. Only when the value is exceeded, the overcurrent detector 53 operates. In this figure, one arm 1 is shown as one determination circuit 5, but a configuration is adopted in which the output signals of the DC current transformers of all the other five arms are added and input to one determination circuit. You can also

As will be described later, the current measured by the DC current transformers 31 and 32 may be positive or negative. Therefore, simply adding by the adder 51 results in subtraction and the output signal of the adder 51 is It can be zero. Therefore, the above-mentioned problem can be avoided by actually inputting the electric signal to the adder 51 through an absolute value circuit such as a double bridge before inputting the electric signal to the adder 51. The filter 52 is for preventing the pulse current flowing through the surge protection circuit 17 during commutation to prevent malfunction of the overcurrent detector 53. The filter 52 is an electric signal rectified by an absolute value circuit. The pulsating flow component can be cut to such an extent that the determination by the determination circuit 5 can be made independent of the on / off period.

FIG. 2 is a circuit diagram for explaining a current flow when the diode 12 in the arm 1 of FIG. 1 fails. If the diode 12 fails, it will be substantially short-circuited. On the other hand, since the diode 15 is normal, there is a voltage drop of about 1 volt when it is on, and therefore the current 44 shown by the chain line in the figure that should originally flow in the normal diode 15 flows as the current 43 in the diode 12. At this time, a rightward current 43 flows in the connecting line 22, and a leftward current 43 flows in the connecting line 21, and these currents are detected by the DC current transformers 31 and 32. Further, when the diode 11 fails, a rightward current flows through the DC current transformer 31 and the DC current transformer 32 does not flow. Diode 13
If a failure occurs, a current flows to the left in the DC current transformer 32 and does not flow in the DC current transformer 31. Diodes 14, 15, 16
In case of failure, the direction of the current is reversed but it is substantially the same as described above. Therefore, which diode 11-16
The failure of the diode can be detected by the determination circuit 5 even if the failure occurs.

The determination circuit 5 merely detects the presence of a failed diode, and does not have a function of specifying which diode has failed. FIG. 3 is a circuit diagram of one arm showing another embodiment of the present invention. In this figure, an example constituted by 3 series and 3 parallel is shown. In this figure, nine diodes 1A to 1I are connected to each other in parallel by four connection lines 2A to 2D, and four DC current transformers 3A to 3D are provided on each of these connection lines 2A to 2D. There is.

Table 1 is a table showing the relationship between the output signals of the four DC current transformers 3A to 3D, the presence / absence of currents, and their directions when any of the nine diodes 1A to 1I fails. is there. In Table 1, ˜ is the output signal of the DC current transformers 3A to 3D in FIG. 3, and the reference symbols A to I of the failed diodes are only the alphabetical suffixes of the diodes 1A to 1I in FIG. . The + sign represents a case where a current flows in the right direction in FIG. 3, the no sign represents a case where no current flows, and the − sign represents a case where a current flows in the left direction. For example, when the diode 1A has a failure, it means that a current with a minus sign is detected in the output signal and no current is detected in and.

[0016]

[Table 1] As can be seen from Table 1, the nine diodes 1A-1I
If any of them fails, the four DC current transformers 3A-3
The signals ~ output by D all show different aspects. Therefore, by discriminating these, the failed diode can be specified.

FIG. 4 is a block diagram showing a defective element specifying circuit for specifying a failed diode. In this figure, the output signal of the DC current transformer 3A of FIG. 1 is input to a state determination circuit 5A, and whether or not the output signal has a predetermined value or more is determined, and the sign thereof is determined to determine the element identification circuit. 55 is input. The state discriminating circuit 5A includes a filter 52A, an overcurrent detector 53A and a polarity discriminator 54A. The filter 52A cuts a harmonic component to determine whether or not a current is detected by the overcurrent detector 53A. The result is input to the element identifying circuit 55, and the polarity discriminator 54 discriminates the positive / negative thereof and is input to the element identifying circuit 55. The element identification circuit 55 makes a determination based on Table 1 to identify the diode that has failed as a result.

Although a detailed description of the structure of the element identifying circuit 55 is omitted, the presence or absence of current is determined by the output signals of the overcurrent detectors 53A to 53D.
The failed diode is specified from the nine diodes 1A to 1I by appropriately combining the determination of the sign with the output signal of 54D. At this time, if a combination not listed in Table 1 is detected, it is considered that either the device itself has failed or two or more diodes have failed at the same time. Therefore, output a determination result to that effect. Is also possible.

The number of the DC current transformers 3A to 3D and the state determining circuits 5A to 5D associated therewith is equal to the number of the connecting lines 2A to 2D, and the number of the connecting lines 2A to 2D is generally the number of series of diodes. (n-1) x (m-1) where n is the number of parallel connections
Becomes In FIG. 1, since n = 3 and M = 2, (3-
1) × (2-1) = 2, and in FIG. 3, n = 3 and m =
Since it is 3, (3-1) × (3-1) = 4. Thus, the number of connecting lines can be smaller than the number of diodes.

In the case of 3 series and 2 parallel, the number of DC current transformers may be 2 as shown in FIG. 1, and in this case as well, the faulty diode can be identified as in the case of FIG. At this time, a table corresponding to Table 1 omits the part of the output signal of Table 1 and the diode codes G to I. Also in this case, two output signals can identify the failure of six diodes. it can. The same applies when the serial / parallel number is larger than that in FIG. However, in the case of 2 series and 2 parallel, only one DC current transformer is required, but since there are four diodes,
The faulty diode cannot be completely identified.
However, it can be specified as two out of four. Also, in the case of 2 series and 3 parallel, two DC current transformers are provided as in the case of 3 series and 2 parallel, but in this case as well, in the method shown in Table 1 and FIG. It is not possible. However, it becomes possible by not only the presence / absence of the current but also by including it in the judgment element for distinguishing whether the current originally flows through the diode.

The determination circuit of FIG. 1 and the faulty element identification circuit of FIG. 4 are examples of analog operation circuits, and are not limited to this circuit, but within the scope of achieving the object of the present invention. Any circuit configuration can be adopted. Also, a configuration may be adopted in which the current measured by the DC current transformer is converted into a digital signal and input to a computer to perform fault determination or element identification by digital calculation.

[0022]

As described above, according to the present invention, the DC current transformers are provided on the connection lines connecting the parallel elements to each other for the mesh connection, and the output values of the DC current transformers are determined by the determination means to be the predetermined values. By determining that any element has failed when it exceeds, it is possible to detect the failure of all the elements with less DC current transformer than the number of elements, so the device reliability can be reduced by reducing the number of circuit elements. And the effect of cost reduction. In addition, when the absolute value of the output value of each DC current transformer is larger than the predetermined value and the direction is positive, when the absolute value is less than the predetermined value, and when the absolute value is larger than the predetermined value and the direction is negative The state discriminating means discriminates the three states, and the faulty semiconductor element is discriminated by the element discriminating means from the combination of the output signals of the state discriminating means corresponding to the individual DC current transformers. In addition, it is possible to facilitate the maintenance of the device.

[Brief description of drawings]

FIG. 1 is a circuit diagram of one arm showing an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a current flow when one diode in FIG. 1 fails.

FIG. 3 is a circuit diagram of one arm showing another embodiment of the present invention.

4 is a block diagram showing an element identifying circuit for identifying a faulty diode in FIG. 3;

FIG. 5 is a circuit diagram showing a rectifier circuit of a conventional rectifier using a mesh connection.

[Explanation of symbols]

 1 arm 11 diode (semiconductor element) 12 diode (semiconductor element) 13 diode (semiconductor element) 14 diode (semiconductor element) 15 diode (semiconductor element) 16 diode (semiconductor element) 1A diode (semiconductor element) 1B diode (semiconductor element) 1C diode (semiconductor element) 1D diode (semiconductor element) 1E diode (semiconductor element) 1F diode (semiconductor element) 1G diode (semiconductor element) 1H diode (semiconductor element) 1I diode (semiconductor element) 21 connection line 22 connection line 2A connection Line 2B Connection line 2C Connection line 2D Connection line 31 DC current transformer 32 DC current transformer 3A DC current transformer 3B DC current transformer 3C DC current transformer 3D DC current transformer 5 Judgment circuit (judgment means) 5A State judgment Circuit (state determination means) 5 device specific circuits (elements specifying means)

Claims (2)

[Claims] 1. An element failure detection device for a rectifying device in which semiconductor elements connected in series and parallel are mesh-connected, wherein a DC current transformer is provided on a connection line forming the mesh connection, and these DC current transformers are connected. An element failure detection device for a semiconductor conversion device, comprising a determination means for determining that a semiconductor element having a failure exists when the output value exceeds a predetermined value. 2. A direct current transformer in which the absolute value of the output value is larger than a predetermined value and the direction is positive, a state in which the absolute value is a predetermined value or less, and a direction in which the absolute value is larger than the predetermined value Element identifying means for identifying a semiconductor element in which a failure has occurred based on a combination of a state determining means for determining three states of a negative case and an output signal of the state determining means corresponding to each DC current transformer. 2. The method according to claim 1, further comprising:
An element failure detection device of the semiconductor conversion device described.