JPH0759255A - Overvoltage protective unit and power converter - Google Patents

Abstract

PURPOSE:To limit the voltage to be turned OFF within a predetermined range lower than the voltage of the entire series circuit at the time of firing thereof by connecting two types of impedance circuit having different impedances in parallel with a plurality of thyristors connected in series. CONSTITUTION:A snubber capacitor 12-n, a snubber resistor 13-n, and a voltage dividing resistor 14-n have a combined impedance of Zn. When they are connected in series, the voltages V1-V3 being applied to thyristors 11-1-11-3 have such relationship as V1:V2:V3=1.5:1:1 when Z1:Z2:Z3=1.5:1:1. An overvoltage detection circuit 15 connected in parallel with the thyristor 11-1 is actuated when the voltage V1 is higher than the voltage across the detection circuit 15. When the operating voltage is set equal to the tiring voltage of element (VSCR), the series circuit has a voltage equal to [1+(1/1.5)+(1+1.5)]VSCR=2.33 VSCR. Consequently, the overvoltage protective unit is turned ON at 2.33VSCR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overvoltage protection device and a power conversion device using a thyristor.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional overvoltage protection device using a thyristor. In the figure,
1 is an induction motor, 2 is a power converter that supplies low-frequency AC power to a secondary circuit of the induction motor 1, and 3 is an overvoltage configured by serially connecting a plurality of antiparallel connection circuits in which thyristors are connected in antiparallel. The protection device is an overvoltage protection device that is connected between each phase of the power conversion device 2. When an overvoltage occurs due to a power failure or the like on the primary side of the induction motor 1, the secondary circuit of the induction motor 1 is short-circuited, and the induction motor 1 is Protect from overvoltage.

FIG. 5 is a specific configuration diagram of a conventional overvoltage protection device. A plurality of anti-parallel connection circuits (the other thyristor is omitted in the figure) formed by connecting the thyristors 11 in anti-parallel are connected in series, and each anti-parallel connection circuit includes a snubber capacitor 12 and a snubber resistor 13. A snubber circuit composed of a series circuit is connected in parallel, the voltage dividing resistors 14 are connected in parallel, and a plurality of sets of anti-parallel connection circuits are connected in series, and an overvoltage detection circuit 15 is connected in parallel. is doing. The overvoltage detection circuit 15 outputs an optical signal when detecting the overvoltage. The optical signal is given to the gate signal generating circuit 20 by the optical cable 19, and the gate signals are given to the n thyristors 11 via the gate signal generating circuit 20 to ignite the thyristors 11.

Snubber capacitor 12 and snubber resistor 1
3. In order to make the voltage sharing between the series of the thyristors 11 uniform, the voltage dividing resistors 14 have the same value in each circuit.

FIG. 6 is a block diagram showing an example of the overvoltage detection circuit 15 of FIG. A resistor 16, a plurality of avalanche diodes 17 and a light emitting diode 18 are connected in series. The avalanche diode 17 is an element that causes a breakdown phenomenon when a predetermined reverse voltage is applied. Further, the light emitting diode 18 is an element which emits light by passing a forward current.

Assuming that the operating voltage value of the avalanche diode 17 is VZ, there are m avalanche diodes.
The operating voltage of the whole series circuit composed of the switch 17 is mV
Z, which is the overvoltage level. That is, when the voltage value of a part of the series circuit of n thyristors in which the overvoltage detection circuit 15 is connected in parallel reaches mVZ, a gate signal is given to the entire n thyristors 11.

Here, the thyristor 11 is detected by the overvoltage detection.
Letting VSCR be the voltage value per element when ignites, the voltage of the entire series circuit composed of n thyristors 11 becomes n.multidot.VSCR. Since VSCR is determined by the number m of avalanche diodes 17, its value changes stepwise.

[0008]

In the overvoltage protection device as shown in FIG. 5, thyristors are connected in antiparallel and n antiparallel circuits are connected in series to connect an overvoltage detection circuit in parallel to a part of the thyristor. If the overvoltage protection device is configured in this manner, the voltage applied to both ends of the overvoltage detection circuit is m · VZ.
Then, it turns on and the electric equipment (not shown) connected to both ends of the overvoltage protection device is protected from the overvoltage.

However, it is connected in parallel to the overvoltage protection device,
The overvoltage protection device shall not turn on for the voltage that is constantly generated in the electrical equipment to be protected from overvoltage. This constantly generated voltage is, for example, as shown in FIG.
In this case, since the surge voltage generated by the power conversion device 2 is also included, it is necessary to select a value higher than the rated voltage of the electric device to be protected from overvoltage. On the contrary, the thyristor 1 that configures the overvoltage protection device so that the voltage at which the overvoltage protection device turns on becomes higher than the voltage that is constantly generated.
The number of series of one anti-parallel circuit must be selected. For example, the voltage that is constantly generated is n.VSCR or more (n + 0.
5) When it is less than VSCR, it is necessary to set the number of series in the antiparallel circuit of the thyristor 11 to (n + 1). Therefore, in this case, the voltage generated in the electric device to be protected from overvoltage or the voltage applied to the electric device is (n +
1) ・ The overvoltage protection device does not turn on unless VSCR is reached. Electrical equipment that must be protected from overvoltage must withstand this (n + 1) VSCR voltage, and in the case of power converters as electrical equipment, insulation determined from constant voltage, insulation higher than the element configuration It is necessary to increase the number of series of antiparallel circuits of the thyristors 11 connected in series.

If the rank of the rated voltage of the avalanche diode is different, the operating voltage of the avalanche diode is also increased, and the detected voltage value by the overvoltage detection circuit changes stepwise. Since the voltage changes stepwise, if the voltage generated in the electrical equipment to be protected from overvoltage or the voltage applied to the electrical equipment cannot be coordinated with the operating voltage of the overvoltage protection device, the electrical equipment to be protected from overvoltage. Has become large and expensive due to the need for insulation reinforcement.

The overvoltage protection device shown in FIG. 5 has a function of protecting the voltage generated in the electric equipment to be protected from the overvoltage or the voltage applied to the electric equipment regardless of the polarity of the voltage. When the voltage generated in the electric device to be protected from overvoltage or the voltage applied to the electric device has only one polarity, the thyristors 11 may be connected in series without being connected in antiparallel. Even in such a case, similarly to the above, when the voltage generated in the electric device to be protected from the overvoltage or the voltage applied to the electric device and the operating voltage of the overvoltage protection device cannot be coordinated, the overvoltage protection device should be protected from the overvoltage. Electric equipment becomes bulky and expensive due to the need to strengthen its insulation.

Therefore, a first object of the present invention is to construct an overvoltage protection device by connecting n thyristors in series, in which a voltage at which the overvoltage protection device is turned on is within a predetermined range from n.VSCR. An object of the present invention is to provide a unidirectional overvoltage protection device that can be made small.

A second object of the present invention is to construct an overvoltage protection device by connecting n thyristors in series, in which the voltage at which the overvoltage protection device turns on is n within a predetermined range.
-To provide a unidirectional overvoltage protection device that can be smaller than VSCR and that can finely adjust the turn-on voltage.

Further, a third object of the present invention is to construct an overvoltage protection device by connecting n thyristors in series.
The voltage at which the overvoltage protection device turns on is
The bidirectional overvoltage protection device that can be smaller than n · VSCR and the voltage at which the overvoltage protection device turns on can be smaller than n · VSCR within a predetermined range.
Another object of the present invention is to provide a bidirectional overvoltage protection device capable of finely adjusting the turn-on voltage.

A fourth object of the present invention is to form an arm of a power conversion device by connecting n thyristors in series, and to provide the arm itself with an overvoltage protection function. Target
It is an object of the present invention to provide a power conversion device composed of an arm having a unidirectional polarity that can turn on the voltage in a predetermined range to be smaller than n · VSCR.

Further, a fifth object of the present invention is to form an arm of a power converter by connecting n thyristors in series.
By providing the arm itself with an overvoltage protection function, the voltage at which the arm turns on can be made smaller than n · VSCR within a predetermined range, and the voltage at which the turn on turns on can be finely adjusted. An object of the present invention is to provide a power conversion device composed of an arm having unidirectional polarity.

Furthermore, a sixth object of the present invention is to form an arm of a power conversion device by connecting n thyristors in series, and to provide the arm itself with an overvoltage protection function. The turn-on voltage can be made smaller than n · VSCR within a predetermined range, and the turn-on voltage can be finely adjusted. An object is to provide a power conversion device.

[0018]

The first object of the present invention is to:
A plurality of thyristors connected in series, an impedance circuit connected in parallel to each of the thyristors, an overvoltage detection circuit connected in parallel to a part of the thyristor, In an overvoltage protection device that includes a gate pulse generation circuit that responds to an overvoltage detection circuit and provides a gate signal to the thyristor, and that is connected in parallel to an electric device to be protected from overvoltage, the impedance circuit includes an impedance value. Can be achieved by using at least two types of impedance circuits having different values.

A second object of the present invention is, as described in claim 2, at least a plurality of thyristors connected in series, an impedance circuit connected in parallel to each of the thyristors, and the thyristor. An overvoltage detection circuit connected in parallel to a part of the above, and a gate pulse generation circuit that responds to the overvoltage detection circuit and provides a gate signal to the thyristor, and an overvoltage connected in parallel to an electrical device to be protected from overvoltage. In the protection device, the impedance circuit can be achieved by configuring the impedance circuit by at least two types of impedance circuits having different impedance values, and at least a part of the impedance circuit being a variable impedance circuit. .

Further, the third object of the present invention can be achieved by connecting the thyristor according to claim 1 and the thyristor according to claim 2 in anti-parallel connection as described in claim 3.

Further, a fourth object of the present invention is, as described in claim 4, in which at least a plurality of thyristors connected in series with the arms constituting the power converter are connected in parallel to the thyristors. A power conversion circuit including an impedance circuit connected to the thyristor, an overvoltage detection circuit connected in parallel to a part of the thyristor, and a gate pulse generation circuit that responds to the overvoltage detection circuit and provides a gate signal to the thyristor. In the apparatus, it can be achieved by configuring the impedance circuit with at least two types of impedance circuits having different impedance values.

Further, a fifth object of the present invention is, as described in claim 5, that at least a plurality of thyristors connected in series with the arms constituting the power converter are connected in parallel to the thyristors. An impedance circuit to be connected,
In an electric power converter comprising an overvoltage detection circuit connected in parallel to a part of the thyristor, and a gate pulse generation circuit for giving a gate signal to the thyristor in response to the overvoltage detection circuit, the impedance circuit is This can be achieved by using at least two types of impedance circuits having different impedance values, and at least a part of the impedance circuits being variable impedance circuits.

Still further, a sixth object of the present invention is to claim 6.
This can be achieved by connecting the thyristor according to claim 4 and the thyristor according to claim 5 in antiparallel.

[0024]

According to the invention of claim 1, the impedance of the impedance circuit is connected in parallel to each of the n thyristors.
When the Dunn values are all the same, if the voltage applied to the overvoltage protection device is E, the voltage applied to each thyristor is E / n.
However, an impedance circuit connected in parallel to each of the n thyristors has an impedance value of Z
1 If the other is two types of impedance circuits with different Z2 (where Z1> Z2), the voltage of E1 is applied to half of the n thyristors, and the voltage of E2 is applied to the other half. , E1 + E2 = E, so E1> E /
2, E2 <E / 2. As described above, if the impedance values of the impedance circuits connected in parallel to the n thyristors are made different, the turn-on voltage of the overvoltage protection device can be changed within a range lower than n · VSCR. .

According to the invention of claim 2, in addition to the effect of the invention of claim 1, at least a part of the impedance circuit is a variable impedance circuit.
After the overvoltage protection device is installed, the turn-on voltage of the overvoltage protection device can be more finely adjusted according to the local situation at the installation site.

Further, according to the invention of claim 3, claim 1
It is possible to provide an overvoltage protection device having a bidirectional polarity, which has the effects of the invention of claim 2 and the effects of the invention of claim 2. Further, according to the invention of claim 4, the arm itself constituting the power conversion device has a protection function against an overvoltage of unidirectional polarity, and the power conversion device capable of adjusting the overvoltage protection operation level is provided. it can.

Further, according to the invention of claim 5, the arm itself constituting the power conversion device has a protection function against an overvoltage having a unidirectional polarity, and this overvoltage protection operation level is
It is possible to provide a power conversion device that can be finely adjusted after installation of the power conversion device according to local conditions at the installation site.

Further, according to the invention of claim 6, the arm itself constituting the power conversion device has a protection function against an overvoltage of bidirectional polarity, and this overvoltage protection operation level is
A power conversion device that can be adjusted or finely adjusted can be provided.

[0029]

FIG. 1 is a block diagram of an overvoltage protection device for protecting an overvoltage having a unidirectional polarity according to an embodiment of the present invention. In the figure, 11-1, 11-2, 11-3 ... 11-n are thyristors, 12-1, 12-2, 12-3 ... 12-n.
Is a snubber capacitor, each snubber capacitor 12-
1, 12-2, 12-3 ... 12-n are connected in series with 13-1, 13-2, 13-3 ... 13-n, respectively.
Is a snubber resistor, thyristor 11-1, 11-2, 11
-3 ... 11-n connected in parallel 14-
1, 14-2, 14-3 ... 14-n are voltage dividing resistors.

Here, a combined impedance of the snubber capacitor 12-1, the snubber resistor 13-1, and the voltage dividing resistor 14-1.
The synthetic impedance of the dance is Z1, the snubber capacitor 12-2, the snubber resistor 13-2, and the voltage dividing resistor 14-2 is Z2, the snubber capacitor 12-3, the snubber resistor 13
-3, the composite impedance of the voltage dividing resistor 14-3 is Z3
, Snubber capacitor 12-n, snubber resistor 13-
n, the combined impedance of the voltage dividing resistors 14-n is Zn.

In the present invention, all or some of Z1, Z2, Z3 ... Zn are selected to have different values. For example, when n = 3, Z1: Z2: Z3 = 1.5: 1: 1 or Z1: Z
Select so that 2: Z3 = 1.5: 1.2: 1.

For the sake of easy understanding, an overvoltage protection device having three series connections will be described below. Z as described above
When 1: Z2: Z3 = 1.5: 1: 1 is selected, the voltage V1 applied to the thyristor 11-1 is
It becomes larger than the voltage V2 applied to 1-2 and the voltage V3 applied to thyristor 11-3, and its ratio V
1: V2: V3 = 1.5: 1: 1.

Here, when the overvoltage detection circuit 15 is connected in parallel to the thyristor 11-1, the overvoltage detection circuit 15 is
It operates when the voltage V1 applied to the thyristor 11-1 becomes m.multidot.VZ or more. Assuming that the operating voltage of the overvoltage detection circuit 15 is VSCR, the voltage applied to the series circuit of the thyristor 3 when the overvoltage detection circuit 15 operates and the thyristors 11-1, 11-2 and 11-3 turn on. Is
[1+ (1 / 1.5) + (1 / 1.5)] VSCR = 2.
It becomes 33VSCR. Therefore, the overvoltage protection device turns on at 2.33V SCR.

Further, for example, the impedance ratio is 1.2:
If the ratio is 1: 1, the turn-on voltage of the overvoltage protection device is [1+ (1 / 1.2) + (1 / 1.2)] VSCR = 2.
It can also be 66VSCR.

By properly selecting the impedance ratio in this way, the voltage at which the overvoltage protection device is turned on can be freely changed. In the embodiment of FIG. 1, snubber capacitors 12-1, 12-2, 12-3 ... 12-n, snubber resistors 13-1, 13-2, 13-3 ... 13-n and voltage dividing resistors 14-. 1, 14-2, 14-3 ... 14-n are fixed values, but as shown in FIG. 2, snubber capacitors 21-1, 21-2, 21-3 ... 21-n are variable capacitors, Snubber resistors 22-1, 22-2, 22
―3 ... 22-n and voltage dividing resistors 23-1, 23-2, 2
If the variable resistors 3-3 ... 23-n are used, the turn-on voltage of the overvoltage protection device can be more finely adjusted.

Further, in FIG. 1 and FIG. 2, when the thyristors 11-1, 11-2, 11-3 ... 11-n are connected in antiparallel as shown in FIG. It can be an overvoltage protection device for protection.

When the voltage generated in the electric equipment to be protected from the overvoltage or the voltage applied to the electric equipment is the unidirectional polarity overvoltage, the overvoltage protection device of FIG. It can be connected in parallel to the device. Further, when the voltage generated in the electric equipment to be protected from the overvoltage or the voltage applied to the electric equipment is the overvoltage having the bidirectional polarity, the overvoltage protection device having the configuration in which the thyristors of FIG. 1 or 2 are connected in anti-parallel is used. Good.

If the arm of the power converter is constructed as shown in FIG. 3 with the overvoltage protection device shown in FIG. 1 or 2, the arm itself has a power conversion device having an overvoltage protection function. Can be provided. In this case, it is possible to omit the overvoltage protection device provided in each arm like the conventional power conversion device.

The arm constituting the power converter is shown in FIG.
The present invention is not limited to the arm configured by connecting the thyristors in series, but the power conversion device may be configured by an arm configured by connecting a plurality of circuits in which the thyristors are connected in anti-parallel in series. The power converter is not limited to the power converter shown in FIG. 3, but may be a power converter or a cycloconverter for a reactive power compensator for compensating reactive power.
It is also applicable to other power conversion devices such as chopper circuits.

[0040]

As described above, according to the first aspect of the present invention, even if an n-th thyristor having an overvoltage detection value of VSCR is connected in series to construct an overvoltage protection device, the turn-on of the overvoltage protection device is turned on. Since the voltage can be reduced to n · VSCR or less, the insulation of electrical equipment to be protected from overvoltage is n
-It does not need to withstand VSCR, and does not require enhanced insulation of electrical equipment to be protected from overvoltage.

Further, according to the invention of claim 2, in addition to the effect of the invention of claim 1, after the overvoltage protection device is installed, the type of the overvoltage protection device is adjusted according to the local situation at the installation site. -The turn-on voltage can be finely adjusted to a predetermined value of n · VSCR or less.

Further, according to the invention of claim 3, claim 1
Alternatively, it is possible to provide the effect of the invention of claim 2, and to provide an overvoltage protection device that protects an electric device from an overvoltage of bidirectional polarity.

Further, according to the invention of claim 4, since the arm itself constituting the power conversion device has an overvoltage protection function capable of adjusting the overvoltage protection operation level, it is provided in each arm. It is possible to provide a power conversion device that can omit the overvoltage protection device that is present.

Furthermore, according to the invention of claim 5, claim 4
In addition to the effects of the invention of claim 1, after the power converter is installed, the overvoltage protection operation level of the arm itself constituting the power converter at the installation site can be finely adjusted according to the local situation. A conversion device can be provided.

Further, according to the invention of claim 6, the effect of the invention of claim 4 or 5 can be obtained, and further, the arm itself constituting the power conversion device has a bidirectional polarity. A power conversion device having an overvoltage protection function can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the present invention.

FIG. 3 is a configuration diagram showing still another embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional overvoltage protection device.

FIG. 5 is a detailed configuration diagram of a conventional overvoltage protection device.

FIG. 6 is a configuration diagram showing an example of an overvoltage detection circuit of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Induction motor 2 ... Power converter 3 ... Overvoltage protection device 11 ... Thyristor 11-1 to 11-N ... Thyristor 12-1 to 12-N ... Snubber capacitor 13-1 to 13-N ... Snubber resistor 14-1 ... 14-N ... voltage dividing resistor 15 ... overvoltage detection circuit 16 ... resistor 17 ... avalanche diode 18 ... light emitting diode 19 ... optical cable 20 ... gate pulse generation circuit 21-1 to 21-N ... Variable capacitors 22-1 to 22-N ... Variable resistors 23-1 to 23-N ... Variable resistors

Claims (6)

[Claims] 1. A plurality of thyristors connected in series, an impedance circuit connected in parallel to each of the thyristors, an overvoltage detection circuit connected in parallel to a part of the thyristor, and an overvoltage detection circuit. In an overvoltage protection device including a gate pulse generation circuit which responds to provide a gate signal to the thyristor and which is connected in parallel to an electric device to be protected from overvoltage, the impedance circuit has at least two impedance values different from each other. An overvoltage protection device characterized by being configured with various types of impedance circuits. 2. A plurality of thyristors connected in series, an impedance circuit connected in parallel to each of the thyristors, an overvoltage detection circuit connected in parallel to a part of the thyristor, and an overvoltage detection circuit. In an overvoltage protection device including a gate pulse generation circuit which responds to provide a gate signal to the thyristor and which is connected in parallel to an electric device to be protected from overvoltage, the impedance circuit has at least two impedance values different from each other. An overvoltage protection device comprising a plurality of types of impedance circuits and at least a part of the impedance circuits being variable impedance circuits. 3. The overvoltage protection device according to claim 1, wherein the thyristor has an antiparallel connection configuration. 4. An arm constituting a power conversion device, at least a plurality of thyristors connected in series, impedance circuits respectively connected in parallel to the thyristors, and a part of the thyristors connected in parallel. In an electric power conversion device comprising an overvoltage detection circuit for providing a gate signal to the thyristor in response to the overvoltage detection circuit, the impedance circuit includes at least two types of impedance values having different impedance values. -A power conversion device comprising a dance circuit. 5. An arm constituting a power conversion device, at least a plurality of thyristors connected in series, impedance circuits respectively connected in parallel to the thyristors, and a part of the thyristors connected in parallel. In an electric power conversion device comprising an overvoltage detection circuit for providing a gate signal to the thyristor in response to the overvoltage detection circuit, the impedance circuit includes at least two types of impedance values having different impedance values. -A power conversion device comprising a dance circuit, and at least a part of the impedance circuit is a variable impedance circuit. 6. The power conversion device according to claim 4, wherein the thyristor has an anti-parallel connection configuration.