JPH0866047A - Voltage type power converter - Google Patents

Abstract

PURPOSE: To suppress short-circuit fault currents and prevent a failure of self- arc-extinguishing element by providing a DC power supply circuit for making a normal equivalent maximum current value of a power converting circuit flow through a diode and also providing a serial connecting circuit of a current limiting reactor. CONSTITUTION: At the time of a short-circuit accident of a power converting circuit, a current flows through a current limiting reactor 12 and restricted by the reverse blocking action of a diode 10. Also, a short-circuit detecting circuit 14 obtains a signal from a current detector 5, a short-circuit accident detecting signal is given to a control circuit 6 by a short-circuit detecting circuit 14 and a protection circuit 15, the control circuit 6 turns all the self-arc- extinguishing type elements 411 to 416 of the power converting circuit to ON through the gate circuit 7, or a gate status at point in time is retained. Moreover, by the short-circuit detecting circuit 14 and a protecting circuit 15, if a current reversing signal generated when a short-circuit accident current is reversed, is given to the control circuit 6, then the control circuit 6 turn off all the self-arc-extinguishing type elements 411 to 416 through the gate circuit 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage-type power converter for converting DC power and AC power in a forward / backward manner by a power converter circuit using a self-extinguishing type switching element, and particularly to a power converter circuit short-circuit accident. The present invention relates to a voltage type power conversion device having an overcurrent protection function.

[0002]

2. Description of the Related Art A voltage converter that reverses DC power and AC power in order by a power conversion circuit composed of a switching element having a self-extinguishing function (hereinafter referred to as a self-extinguishing element) such as a gate turn-off thyristor or an electrostatic induction thyristor. Power converters are commonly used. In a voltage-type power converter, a method of turning on all the self-extinguishing elements in the event of a short-circuit accident is generally taken to protect the self-extinguishing elements in the case of an arm short circuit failure or an output short circuit failure of the power conversion circuit. ing. This type of conventional technique will be described with reference to FIGS. 4 and 5.

FIG. 4 shows the structure of the main part of a conventional example. Reference numerals 2 and 3 are filter capacitors and filter reactors arranged on the output side of the DC power supply 1, and 4 is a self-extinguishing element.
11 to 416 and feedback diodes 421 to 426 respectively connected in reverse parallel to the self-extinguishing elements thereof. Further, 5 is a current detector for detecting the current of the filter capacitor 2, 6 is a control circuit for applying a gate signal through the gate circuit 7 to control ON / OFF of the self-extinguishing type elements 411 to 416, and 8 is a current detector 5. A short circuit detection circuit for detecting an arm short circuit failure or the like from the output signal, and a protection circuit 9 for receiving the output signal of the short circuit detection circuit 8 and providing a protection control signal to the control circuit 6. Here, the power conversion circuit 4 receives a DC input and supplies three-phase output AC power to be applied to a power system or an electric motor, etc., by controlling ON / OFF of the self-extinguishing elements 411 to 416.

In this type of voltage type power converter,
An arm short circuit or output short circuit failure of the power conversion circuit 4 occurs, and the short circuit detection circuit 8 detects a short circuit failure current larger than the current of the filter capacitor 2 in the normal operation from the output of the current detector 5 and outputs an overcurrent signal to the protection circuit 9. Is output. Further, the control circuit 6 that obtains the output of the protection circuit 9 includes the gate circuit 7
By blocking the control signal to the self-extinguishing elements and turning on all the self-extinguishing elements of the power conversion circuit 4, all short-circuit currents are turned on by turning on all the self-extinguishing elements. Divide the current into the arms of the shape elements 411 to 416, etc., and reduce the current of the arm that caused the short-circuit fault. After that, when the currents of the self-arc-extinguishing elements 411 to 416 are reversed, an OFF signal is given to all the self-arc-extinguishing elements, the operation of stopping the device is performed, and the elements of the power conversion circuit are prevented from being destroyed by the overcurrent. It was protected.

FIG. 5 shows the structure of the main part of another conventional example, in which 10 is a diode and 11 is a current limiting reactor. In the figure, the same symbols as those in FIG. 4 indicate parts having the same functions. That is, the power conversion circuit 4 and the filter capacitor 2
Between the DC stage and the diode 10 in the direction shown in FIG.
Is arranged in series with the power conversion circuit 4, and the current limiting reactor 11 is connected in parallel with the diode 10. With such a configuration, the protection operation at the time of short-circuit failure is the same as that of the example of FIG. 4, but the current limiting reactor 11 is effective and the current limiting reactor 11 suppresses the overcurrent at the time of short-circuit failure. .

[0006]

As described above, in the overcurrent protection function of the conventional voltage type power conversion device, basically,
Simultaneously with the occurrence of the short-circuit fault, all the self-extinguishing elements are turned on and the short-circuit current is shunted to other arms as well, and the element current of the arm in which the short-circuit fault occurs is reduced. During the subsequent half cycle, the device is stopped when the device current reverses,
The operation is to protect the element from destruction.

Here, in terms of the protection operation, in order to surely protect the element from damage, it is important to keep the element current flowing when all arc-extinguishing elements are turned on within the overcurrent withstanding capability. The filter capacitor constant was designed and the element rating was selected so that it was within the overcurrent withstand capability. Alternatively, in the example of FIG. 5, the overcurrent is suppressed by the current limiting reactor. However, the magnitude of the short-circuit current that flows due to commutation failure of the self-extinguishing element depends on the impedance of the circuit, the capacity of the filter capacitor, and the voltage of the DC stage. In particular, when the voltage of the DC stage becomes high due to the high voltage and large capacity of the device, the value of the short circuit current increases and exceeds the overcurrent withstanding capability of the self-extinguishing element.

Further, in the method of inserting the current limiting reactor, if the inductance is required to suppress the short-circuit current, the electric power is supplied through the reactor even during normal operation, so that the electric power due to the voltage drop of the reactor is generated. The voltage of the conversion circuit drops and a current delay occurs. This causes problems such as poor control performance, and becomes a problem especially when applied to a high-voltage power converter. The present invention solves such a problem, and an object of the present invention is to suppress a short-circuit fault current without deteriorating the performance, especially in a device having a high voltage and a large capacity, and to provide a power conversion circuit. It is an object of the present invention to provide a special device capable of effectively protecting the self-arc-extinguishing element of the present invention from destruction.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and voltage-type power for converting DC power and AC power in reverse order by a power conversion circuit composed of self-arc-extinguishing elements. In the converter, a diode with a polarity that blocks the current on the DC power supply side is connected to the DC side of the power conversion circuit, and a DC power supply circuit and a current limiting reactor that pass the current corresponding to the maximum normal value of the power conversion circuit through the diode. When a circuit connected in series with this diode is connected in parallel with this diode, and the DC power supply circuit is always made to flow through the diode, a short circuit fault current of more than this flowing value will flow. The reverse blocking action of the diode diverts the current to the current limiting reactor to suppress the magnitude of the short-circuit current, and detects all short-circuit faults to turn on all self-extinguishing elements or at that time. Over preparative state is held, and in which current reverses the arm current of the power conversion circuit is configured to turn off all the self-turn-off device at the time the flow through the feedback diode.

[0010]

When the short-circuit current reaches the detected value, the diode current becomes zero and flows into the current limiting reactor, and the short-circuit current can be suppressed. Furthermore, by turning off all the self-extinguishing elements when the arm current of the power conversion circuit is reversed, it is possible to protect the elements from destruction. Although the current flowing through the diode is a large value equivalent to the short-circuit current detection value, a low-voltage, small-capacity DC power supply circuit that takes into account the conduction loss of the diode and the loss of the current limiting reactor is used. You can Also, the current controlled by the power conversion circuit does not flow through the current limiting reactor,
It is clear that the voltage drop and the current delay as in the example of FIG. 5 are not caused. In this way, the current limiting reactor can be actuated so that the short-circuit current can be suppressed within the surge current withstanding capability of the self-extinguishing element only in the half thyristor in which a short-circuit accident occurs. Even in the application of the above, the overcurrent protection function can be particularly exerted.
Hereinafter, the present invention will be described in detail with reference to the drawings.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the main construction of an embodiment of the present invention.
Similar to FIG. 5, 12 is a current limiting reactor, 13 is a DC power supply circuit, 14 is a short circuit detection circuit, and 15 is a protection circuit. That is, in FIG. 1, in particular, a series connection circuit of the current limiting reactor 12 and the DC power supply circuit 13 is provided in parallel with the diode 10. Here, the diode 10 and the DC power supply circuit 13 are arranged in the illustrated direction. Further, the output of the protection circuit 15 is controlled by the short circuit detection circuit 14 for obtaining the output of the current detector 5 and the protection circuit 15 for obtaining the output of the short circuit detection circuit 14.
It is configured to give to.

Next, the operation of this circuit configuration will be described. In the parallel circuit of the diode 10, the DC power supply circuit 13, and the current limiting reactor 12 shown in FIG.
Is arranged so that a current equivalent to the short-circuit current detection value can flow through the current limiting reactor 12 and the diode, and the current value is supplied during normal operation. The DC power supply circuit 13 supplies a current with a low voltage power supply, and has only a small capacity because it has only a diode conduction loss and a reactor loss here.
Now, at the time of a short circuit accident of the power conversion circuit 4, if the current of the DC stage becomes equal to or more than the above-mentioned short circuit current detection value, the diode
The reverse blocking action of 10 causes the current to be suppressed through the current limiting reactor 12.

The short-circuit detection circuit 14 obtains the output signal of the current detector 5, and the short-circuit detection circuit 14 and the protection circuit 15 provide the short-circuit accident detection signal to the control circuit 6 and the control circuit 6
Turns on all the self-extinguishing elements 411 to 416 of the power conversion circuit 4 via the gate circuit 7 or maintains the gate state at that time. Further, when the short circuit detection circuit 14 and the protection circuit 15 provide the control circuit 6 with a current reversal signal generated when the short circuit fault current is reversed, the control circuit 6
Turns off all self-extinguishing elements 411-416 via gate circuit 7.

FIG. 2 shows the circuit state during the overcurrent protection operation, and FIG. 3 shows the current waveform at this time. 2 and 3, when, for example, an arm short circuit accident occurs in which the self-extinguishing elements 441 and 414 are simultaneously turned on from the normal operating state at time T0, the current IF of a value equivalent to the short circuit current detected by the diode 10 is passed. Short circuit current I1 is diode
Flows through 10 at high (dt / di). At the time point T1 when the short-circuit current I1 reaches the short-circuit current detection equivalent value IF, the short-circuit current I2 flows through the shunt through the current limiting reactor 12 and the DC power supply circuit 13 due to the reverse blocking action of the diode 10. At this time, since the gradient of the short-circuit current I2 is limited by the current limiting reactor 12, the short-circuit current value can be suppressed. The value of the current limiting reactor may be designed so that the currents flowing through the self-arc-extinguishing elements 411 to 416 are within the element overcurrent withstand capability.

After that, at time T2, the short-circuit current I2 becomes zero, and due to the resonance of the current limiting reactor 12 and the filter capacitor 2, the inverted short-circuit current I3 is returned to the feedback diode, for example.
It flows through 426, 421 and diode 10. During the period from time T2 when the short-circuit current I3 flows to time T3, since all the self-extinguishing type elements 411 to 416 are turned off as described above,
Therefore, the short-circuit current I3 is commutated to the diode side, and the short-circuit current that continues to flow is blocked without current interruption by the element during the zero-current period on the side of all self-extinguishing elements, and the device is stopped. be able to.

In the embodiment thus constructed, a DC power supply circuit 13 capable of flowing a current equivalent to the short-circuit current detection value is arranged in the current limiting recoil 12 and the diode 10, and the short-circuit current detection value equivalent. By flowing the current of 10 through the diode 10, the DC side current of the power conversion circuit flows through the diode 10 during normal operation, and a short-circuit fault occurs, and the short-circuit current flows only when the short-circuit current detection value or more is reached. Through which the short circuit current is suppressed. At the same time, all self-extinguishing elements of the power conversion circuit are turned on or hold their gate state, and further after the current reversal, all self-extinguishing elements are turned on during the period when the feedback diodes connected to the self-extinguishing elements are connected in antiparallel. By turning off the element, overcurrent interruption of the element is prevented. Therefore, even if the power conversion circuit current flows through the diode 10 during normal operation, the output of the current conversion circuit is increased even if the device has a high voltage and a large capacity to sufficiently suppress the short-circuit current and sufficiently increase the value of the current limiting reactor. The voltage does not decrease and the output current control performance does not deteriorate.

[0017]

As described above, according to the present invention, the short-circuit fault current can be suppressed and the self-extinguishing type of the power conversion circuit can be suppressed without deteriorating the performance even in a device having a high voltage and a large capacity. It is possible to provide a voltage type power conversion device having an overcurrent protection function with a simple configuration that can effectively protect elements from damage.

[Brief description of drawings]

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

FIG. 2 is a circuit state diagram shown for explaining the operation of FIG.

FIG. 3 is a diagram showing a current waveform of FIG.

FIG. 4 is a configuration diagram showing a conventional example.

FIG. 5 is a configuration diagram showing another conventional example.

[Explanation of symbols]

1 DC power supply 2 Filter capacitor 3 Filter 4 Power conversion circuit 411 Self-extinguishing switching element (self-extinguishing element) 421 Feedback diode 5 Current detector 6 Control circuit 7 Gate circuit 8 Short circuit detection circuit 9 Protection circuit 10 Diode 11 Current limiting reactor 12 Current limiting reactor 13 DC power supply circuit 14 Short circuit detection circuit 15 Protection circuit I1 Short circuit current I2 Short circuit current I3 Short circuit current IF Current equivalent to short circuit current detection value

Claims (2)

[Claims] 1. A voltage type power conversion device for obtaining alternating current from direct current by a power conversion circuit using a self-extinguishing type switching element, wherein the voltage side power conversion device is arranged on the direct current side of the power conversion circuit with a polarity that blocks the current of a direct current power supply. A diode and a series connection circuit of a direct current power supply circuit and a current limiting reactor for allowing the diode to pass a value corresponding to the maximum current commonly used in the power conversion circuit in parallel with the diode are provided, and a short circuit accident occurs in the power conversion circuit. While detecting an overcurrent, all the self-extinguishing switching elements are turned on, and all the self-extinguishing switching elements are turned off during a period in which the arm current of the power conversion circuit is reversed. Voltage type power converter. 2. A voltage type power conversion device for obtaining AC from DC by a power conversion circuit using a self-extinguishing type switching element, wherein the DC side of the power conversion circuit is arranged in a polarity to block a current of a DC power supply. A diode and a series connection circuit of a direct current power supply circuit and a current limiting reactor for allowing the diode to pass a value corresponding to the maximum current commonly used in the power conversion circuit in parallel with the diode are provided, and a short circuit accident occurs in the power conversion circuit. While detecting an overcurrent, the self-extinguishing switching element is held in the gate state at that time, and all the self-extinguishing switching elements are turned off during the period when the arm current of the power conversion circuit reverses. A voltage type power conversion device characterized by the above.