JP2000152605A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large capacity power converter which can detect a turn-off failure in a short time and protect GTOs from chain breakdowns to improve reliability by adding and changing a low cost and small-sized circuit. SOLUTION: The voltage between the terminals of an off-gate output switch 25 is amplified by a preamplifier 26. If the output voltage V of the preamplifier 26 is higher than a reference voltage Vref in steady state after the turn-off, it is determined that the turn-off has failed, and a controller 1 is instructed so as not to output turn-on signals to all GTOs so as to protect normal GTOs from breakdown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device such as an inverter or a converter constituted by using a large-capacity GTO.

[0002]

2. Description of the Related Art As a method of detecting a turn-off failure (breakdown) of a GTO element, an overcurrent detection by a change in impedance between a gate and a cathode or a detection by a change in voltage between a gate and a cathode is used. As a method based on overcurrent detection, a method disclosed in, for example, Japanese Unexamined Patent Application Publication No. 59-83569, entitled "Failure detection circuit of gate turn-off thyristor" is disclosed. In this known example, a current detector (current transformer) is provided on the primary side of an insulating transformer that supplies off power to the GTO gate driver, and overcurrent detection is performed. A similar technology is disclosed in
No. 19916 is also disclosed. A method of directly detecting a gate current via a current transformer is disclosed in Japanese Patent Application Laid-Open No. 61-15 / 1986.
No. 7256, JP-A-2-106158, JP-A-4-1
No. 25057 and the like.

[0003]

Among the above-mentioned prior arts, in the method of providing a current detector on the primary side of an insulating transformer, it is necessary to provide a current detector such as a current transformer in addition to a power supply circuit. However, it is difficult to reduce the size and cost of the circuit, and because the gate signal is not detected directly but through a transformer, a delay occurs before overcurrent detection, which is not suitable for high-speed on / off control. There was a problem. Also, the method of measuring the gate current directly through the current transformer is
Since the current transformer is inserted into the gate lead wire, the inductance of the lead wire increases, so that there is a problem that a steep off-gate signal necessary for turn-off is impaired especially in the case of a large-capacity GTO.

[0004] In addition, when detection is performed based on a change in gate-cathode voltage during the GTO off period, a gate reverse voltage (negative voltage) is generally applied between the gate and the cathode to prevent erroneous firing during the GTO off period. The method of applying is taken. This voltage varies depending on the GTO element, but is a negative voltage of about 20V. Therefore, during normal turn-off, a gate reverse voltage is generated between the gate and the cathode. On the other hand, when the turn-off fails, a negative voltage is generated between the gate and the cathode because the impedance between the gate and the cathode of the GTO becomes low and a negative gate current continuously flows. For example, if the gate-cathode impedance at the time of turn-off failure is 20 mΩ and the negative gate current is 900 A,
A negative voltage of 18 V is generated between the gate and the cathode. There is almost no difference between this voltage and the gate reverse voltage, and it is difficult to distinguish and detect this. Further, in order to enable detection, it is necessary to stabilize the power supply for suppressing the voltage fluctuation of the gate reverse voltage, which leads to an increase in the size and cost of the power supply circuit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-cost, small-sized circuit configuration without providing an unnecessary detector in a GTO gate driver, and a highly reliable device capable of detecting a turn-off failure in a short time. An object of the present invention is to provide a power converter using a large capacity GTO.

[0006]

In order to achieve the above object, the present invention provides a method for each of the GTOs constituting the arm.
A power converter configured to provide an on signal for turning on the GTO via an on-gate switch and an off signal for turning off the GTO to a gate of the GTO via an off-gate switch. In G
Provided for each TO, when the potential difference generated between both terminals of the off-gate switch when the off-gate switch is turned on and the off signal is applied to the gate is equal to or less than a predetermined reference value, and Only at that time, current detection means for outputting a detection signal of the first level indicating that the GTO has been normally turned off, provided for each GTO, and a predetermined time from when the off-gate switch is turned on. Determining means for determining whether or not the output of the current detecting means at the first level is equal to or less than the first level, and determining that the determination means corresponding to at least one GTO is not at the first level. And a control means for controlling not to output ON signals to all GTOs.

Further, the present invention provides a method for determining whether or not the output of the current detecting means when the predetermined time has elapsed is equal to the first level. When the time has elapsed, the output of the current detection means is sampled a plurality of times, and when at least half of the sampled value is equal to or less than the reference value, the output is determined to be the first level. A power conversion device is disclosed.

Further, the present invention is characterized in that display means for displaying which GTO corresponds to the judgment means when the judgment result by the judgment means is not the first level is added. A characteristic power converter is disclosed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a power conversion device according to the present invention, which is an example of an inverter device.
In the figure, a DC power supply 9 is converted into three-phase AC by GTO converters 31 to 33 and supplied to a load 10. U, V,
Each of the GTO converters 31, 32, and 33 of each phase W has the same configuration, and one GTO converter includes two GTOs, and ignition / extinguishing control is individually performed. In FIG. 1, U
Only the GTO converter 31 of the phase is shown in detail, and only one configuration of the gate driver 2 for controlling the ignition / extinguishing of each of the GTOs 41 and 42 is shown.

FIG. 2 shows details of the gate driver of the GTO 42. An on / off control signal 14u from the control device 1 is supplied to an on / off pulse control section 21 in the GTO gate driver 2 by an on / off output switch 23 and an off gate. The signals are converted into signals for turning on the output switches 25, respectively. Here, semiconductor switches such as transistors are used as the switches 23 and 25. When the switch 23 is turned on, the on-gate storage battery 22
A forward current flows through the gate of the GTO 42 to turn on the GTO 42, and the off-gate storage battery 24 turns off the GTO 42 when the switch 25 is turned on.

The detection of the gate current, which is a feature of the present invention,
This is performed by detecting a voltage drop in the off-gate output switch 25. For this reason, both terminals of the off-gate output switch 25 are input to the preamplifier 26, and the potential difference between the two terminals is amplified to become the output voltage V of the preamplifier 26.
This voltage V is a voltage proportional to the gate current flowing through the on-resistance when the switch 25 is turned on. This voltage is compared with a reference voltage Vref by a comparator 27, and the comparison result is returned to the control device 1 as a detection signal 15u. It is. Here, FIG.
As shown in the figure, the preamplifier 26 includes a non-inverting input operational amplifier 26c and two input resistors 26a and 26b. The comparator 27 includes a reference voltage Vref generated by dividing the voltage by the resistors 27a and 27b and a preamplifier. 26 is used as an input to the operational amplifier 27c.

The configuration of the other GTO gate driver 2 is the same. Then, the GTO 41 constituting another arm for the U phase in FIG. 1 is supplied with an on / off control signal 12u from the control device 1 to the gate driver, and returns a detection signal 13u. Similarly, the V-phase GTO converter 3
2, on / off control signals 12 v and 14 v are provided from the control device 1 corresponding to the two arms, and the detection signal 13
v and 15v are returned, and in the W-phase GTO converter 33, on / off control signals 12w and 14w are given from the control device 1 corresponding to the two arms, and detection signals 13w and 15w are returned.

Next, the inverter device shown in FIG. 1 will be described by taking the GTO 42 of the U-phase GTO converter 31 as a representative. First, in the ON operation, the ON control signal 14u from the control device 1
Turns on the on-gate switch 23 via the on-off pulse control unit 21. Thus, an on-gate current, which is a positive current, flows from the on-gate storage battery 22 to the gate terminal of the GTO 42, and the GTO 42 is turned on. Next, in the off operation, the off control signal 14u from the control device 1 turns on the off gate output switch 25 via the on / off pulse control unit 21. Thus, an off-gate current as a negative current flows from the off-gate storage battery 23 to the gate terminal of the GTO 42,
Is turned off.

FIG. 3 is a timing chart showing the state of each signal at the time of the OFF operation, with the time axis taken along the horizontal axis. G
When the TO normally shuts off the anode current, the control device 1
When the on / off control signal 14u from ON changes from ON to OFF, the gate current IG of the GTO becomes a steep negative current. When the GTO shuts off the anode current (time t1),
The gate current IG gradually increases, and eventually becomes zero.
On the other hand, when the on / off control signal 14u changes from on to off, the preamplifier output V once drops to near zero voltage, then rises due to the on-resistance of the off-gate output switch 25, and further at time t1 when the GTO cuts off the anode current. And gradually falls to a value V near zero voltage
It becomes 1. Assuming that the comparator 27 operates so that the detection signal 15u goes high when V <Vref, the detection signal 15u goes high at time t2.
The time T required for the detection signal 15u to rise to the high level at the time t2 after the on / off control signal 14u is turned off is about several tens of μs, and this value is known in advance.
Therefore, in the control device 1, an appropriate time width after the time T from turning off the on / off control signal 14u is set as a detection signal monitoring period (part a in FIG. 3), and the detection signal 15u is output a plurality of times, for example, three times during that period And check if more than half of them are high level. And if more than half is high level, it is judged that turn-off was performed normally,
The on / off control signal 12u to the GTO 41 of the paired arms is turned on (part b in FIG. 3).

When the turn-off of the GTO fails (breakdown), the gate current IG does not return to zero current.
As shown by the dotted line, a current of, for example, about several hundreds A continues. Due to this current, a voltage drop occurs due to the on-resistance of the switch 25, and the preamplifier output V becomes a voltage V2 higher than V1 at the time of successful turn-off at time t2. Therefore, the reference voltage Vref is set to the value V1 of the successful turn-off and the value V of the failure of the preamplifier output voltage V before and after the time t2.
2, the detection signal 15u, which is the output of the comparator, does not go high when the turn-off fails. At this time, the control device 1 stops the operation of turning on the GTO 41 and turning on the next GTO 42 because the sampling effect in the section a is almost at a low level, and also turns on the other GTO converters 32 and 33. The operation is also stopped to prevent the occurrence and spread of a failure due to a short circuit.

The control device 1 further includes a GT as described above.
When detecting a turn-off failure of O, it indicates which GTO
It is easy to know which GTO should be checked if some kind of display is made to notify the maintenance person so that the GTO can be recognized.

As described above, according to the gate current detection method which is a feature of the present invention, the off-gate output switch 25 has no internal current transformer or the like for the main circuit. This configuration uses a resistor to detect the voltage drop. For this purpose, it is necessary that the difference between the above-mentioned voltage drops due to the gate current when the turn-off fails and when the turn-off fails is a value that can be detected. In this regard, for example, a switching transistor having an internal resistance of 2 mΩ is used as an off-gate output switch, and the gate current when the turn-off fails is 1
Considering the case where a GTO of 000 amps is controlled, the voltage drop due to the internal resistance is more than 2 V, and when the turn-off is successful, the voltage is almost OV. Further, since detection is performed in a transient state, more reliable detection can be performed by sampling and majority logic as described above.

[0018]

According to the present invention, a turn-off failure (breakdown) can be detected in a short time by adding or changing an inexpensive and small-sized circuit, and the reliability that does not cause the GTO breakdown to propagate in a chain is obtained. A high-capacity power conversion device with high performance can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an inverter device according to the present invention.

FIG. 2 is a block diagram showing a configuration inside a GTO gate driver.

FIG. 3 is a timing chart for explaining the operation of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control device 2 GTO gate driver 9 DC power supply 10 Load 12u-12w, 14u-14w On-off control signal 13u-13w, 15u-15w Detection signal 21 On-off pulse control unit 22 On-gate storage battery 23 On-gate output switch 24 Off-gate storage battery 25 Off-gate output switch 26 Preamplifier 27 Comparator 31-33 GTO converter 41, 42 GTO

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[Procedure amendment]

[Submission date] February 3, 1999 (1999.2.3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

In order to achieve the above object, the present invention provides a method for each of the GTOs constituting the arm.
An on signal for turning on the GTO is turned on through an on-gate switch, and an off-gate signal for turning off the GTO is turned on via the off-gate switch.
In the power converter configured to be applied to the gate of the power supply, the power supply device is provided for each GTO, between the two terminals of the off-gate switch when the off-gate switch is turned on and the off signal is applied to the gate. Current detection means for outputting a detection signal having a first level indicating that the GTO is normally turned off when the generated potential difference is equal to or less than a predetermined reference value and only at that time, provided for each GTO; Determining means for outputting an abnormal signal when the detection signal is not at the first level when a predetermined time has elapsed from the time when the off gate switch is turned on;
Control means for controlling not to output ON signals to all GTOs when the determination means corresponding to one GTO outputs the abnormal signal. I do.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

Further, the present invention relates to the G
For each TO, an on signal for turning on the GTO is supplied to the gate of the GTO via an on-gate switch, and an off-gate signal for turning off the GTO is supplied to the gate of the GTO via an off-gate switch. In the power converter, the potential difference generated between the two terminals of the off-gate switch when the off-gate switch is turned on and the off signal is applied to the gate is provided in advance for each GTO, and is set in advance. Current detection means for outputting a detection signal of a first level indicating that the GTO has been normally turned off when and only when the value is equal to or less than the reference value, and the off-gate switch is provided for each GTO and turned on. More than half of the detection signal at a plurality of time points after a predetermined time has passed from the time point is the first signal. A determination unit that outputs an abnormal signal when the signal is not a bell, and controls so as not to output ON signals to all GTOs when the determination unit corresponding to at least one GTO outputs the abnormal signal. A power conversion device comprising: a control unit;

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

Further, according to the present invention, in the above-mentioned power converter, when the abnormal signal is output, a display for indicating which GTO corresponds to the judging means which has output the abnormal signal. A power converter characterized by adding means is disclosed.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of a power conversion device according to the present invention, which is an example of an inverter device. In the figure, a DC power supply 9 is connected to GTO converters 31 to 3.
The power is converted into three-phase AC by 3 and supplied to the load 10. U,
Each of the GTO converters 31, 32, and 33 for each of the V and W phases has the same configuration, and one GTO converter includes two GTOs to individually control ignition / extinguishing. In FIG. 1, only the U-phase GTO converter 31 is shown in detail, and only one configuration of the gate driver 2 for controlling the firing / extinguishing of each of the GTOs 41 and 42 is shown.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

Next, the inverter device shown in FIG. 1 will be described by taking the GTO 42 of the U-phase GTO converter 31 as a representative. First, in the ON operation, the ON control signal 14u from the control device 1
Turns on the on-gate switch 23 via the on-off pulse control unit 21. Thus, an on-gate current, which is a positive current, flows from the on-gate storage battery 22 to the gate terminal of the GTO 42, and the GTO 42 is turned on. Next, in the off operation, the off control signal 14u from the control device 1 turns on the off gate output switch 25 via the on / off pulse control unit 21. As a result, an off-gate current, which is a negative current, flows from the off-gate storage battery 24 to the gate terminal of the GTO 42, and the GTO 42
Is turned off.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

When the turn-off of the GTO fails (breakdown), the gate current IG does not return to zero current.
As shown by the dotted line, a current of, for example, about several hundreds A continues. Due to this current, a voltage drop occurs due to the on-resistance of the switch 25, and the preamplifier output V becomes a voltage V2 higher than V1 at the time of successful turn-off at time t2. Therefore, the reference voltage Vref is set to the value V1 of the successful turn-off and the value V of the failure of the preamplifier output voltage V before and after the time t2.
2, the detection signal 15u, which is the output of the comparator, does not go high when the turn-off fails. At this time, the control device 1 stops the operation such as turning on the next GTO 41 and turning on the next GTO 42 because the sampling result at the section a is almost low level, and also turns on the other GTO converters 32 and 33. The operation is also stopped to prevent the occurrence and spread of a failure due to a short circuit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoki Misawa 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Process Computer Engineering Co., Ltd. (72) Inventor Shigetoshi Okamatsu 5-chome Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Inside the Hitachi, Ltd. Omika Plant (72) Inventor Kiyotaka Kobayashi 5-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term inside the Hitachi, Ltd. Omika Plant F-term (reference) JB02

Claims (3)

[Claims] 1. An on-signal for turning on the GTO is provided via an on-gate switch, and an off-signal for turning off the GTO is provided via an off-gate switch for each GTO constituting the arm. In the power converter configured to supply to the gate of the GTO, provided for each GTO, the off-gate switch is turned on when the off-gate switch is turned on and the off signal is applied to the gate. Current detection means for outputting a detection signal having a first level indicating that the GTO has been normally turned off only when the potential difference between the two terminals is equal to or less than a predetermined reference value, and The output of the current detection means when a predetermined time has elapsed from the time when the off-gate switch is turned on, Determining means for determining whether the level is a level or not, and controlling not to output ON signals to all GTOs when the determination result of the determining means corresponding to at least one GTO is not the first level. A power converter, comprising: control means; 2. The method according to claim 1, wherein the output of the current detecting means when the predetermined time elapses is equal to the first time.
The output of the current detection means is sampled a plurality of times when the predetermined time has elapsed in order to determine whether or not the level is equal to or less than a predetermined value. The power converter according to claim 1, wherein the power converter is configured to determine the first level. 3. The method according to claim 1, wherein a result of the determination by the determination means is the first
2. The power converter according to claim 1, further comprising a display unit for displaying which GTO the determination unit corresponds to when the level is not the level.