JP2012034451A - Protective device of power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective device of a power conversion device capable of performing overvoltage protection with sure and quickly.SOLUTION: A protective device of a power conversion device includes a DC power source 1 of 3-level, DC capacitors 5A and 5B on a positive side and negative side, a 3-level inverter 6 for driving an AC motor 7, first initial charging means 8 for performing initial charging with the capacitors 5A and 5B, and first short circuit failure detecting means for detecting an internal short circuit failure of the 3-level inverter. It further includes a first bridge circuit 9 for rectifying an input of the AC motor 7, a first thyristor 10 provided parallel to the DC output of the first bridge circuit 9, a first ignition assisting capacitor 11 connected parallel to the thyristor, and second initial charging means for performing initial charging with the first ignition assisting capacitor. When the first short circuit failure detecting means detects the short circuit failure, the first thyristor is ignited.

Description

  The present invention relates to a protection device for a power conversion device, and more particularly to a protection device for a power conversion device that suppresses an overvoltage of a DC capacitor when a failure occurs in the power conversion device.

  In recent power converters, power converters equipped with a DC capacitor on the DC side are widely used. With the increase in voltage and current, the number of DC capacitors in series and in parallel increases, and the DC capacitor as a whole is increased. The proportion occupied by is also increasing. In such a power converter, when operating normally, a DC voltage obtained by converting an AC voltage on the power supply system side into a DC by a converter is applied to the DC capacitor and is not overcharged. However, the DC capacitor may be overcharged by the energy on the power supply system side due to a DC short circuit failure due to breakage of the switching element on the converter side or false ignition, and the rated voltage may be exceeded. The same applies to the inverter side, and the DC capacitor is overcharged by the energy on the motor side due to the DC short circuit failure due to breakage of the switching element on the inverter side or false ignition. At this time, if the failure state continues, there is a risk of causing an accident such as a burst of the DC capacitor and an arc discharge of the switching element. In order to prevent such damage from spreading, it is necessary to provide a protection circuit on the power supply system side and the motor side, and the proposal has been made to suppress the overcharge of the DC capacitor by consuming the energy caused by the short-circuit failure in the protection circuit ( For example, see Patent Document 1.)

JP 2010-11612 (page 8-9, FIG. 9, FIG. 10)

  The conventional protection circuit disclosed in Patent Document 1 does not mention the function of reliably and quickly starting a thyristor that is fired when overvoltage protection is performed, and in some cases, the burden on the thyristor increases. In addition, there was a problem that the ignition operation was delayed.

  This invention is for solving the above problems, and it is an object of the present invention to provide a protection device for a power conversion device capable of reliably and quickly performing overvoltage protection.

  In order to achieve the above object, a protection device for a power conversion device according to the present invention includes a three-level DC power source, positive and negative DC capacitors fed from the DC power source, and 3 applied to the DC capacitor. A three-level inverter that converts the DC voltage of the level into an AC voltage to drive the AC motor, a first initial charging means for initially charging the DC capacitor, and a first detector that detects an internal short-circuit fault of the three-level inverter 1 is a protection device that performs overvoltage protection of a power converter having one short-circuit fault detection means, the first bridge circuit rectifying the input of the AC motor, and a DC output of the first bridge circuit in parallel. A first thyristor provided; a first ignition auxiliary capacitor connected between the anode and cathode of the first thyristor; and the first ignition auxiliary capacitor. And a second initial charging means for initially charging the first thyristor when the first short-circuit fault detecting means detects a short-circuit fault. .

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the protective device of the power converter device which can perform overvoltage protection reliably and rapidly.

The circuit block diagram of the protection apparatus of the power converter device which concerns on Example 1 of this invention. The circuit block diagram of the protection apparatus of the power converter device which concerns on Example 2 of this invention. The circuit block diagram of the protection apparatus of the power converter device which concerns on Example 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a circuit configuration diagram of a protection device for a power conversion device according to a first embodiment of the present invention.

  In FIG. 1, a DC power source 1 outputs three levels of a positive potential, a negative potential, and a zero potential. A positive capacitor 5A is connected between the positive potential and the zero potential, and a negative capacitor 5B is connected between the zero potential and the negative potential.

  The three-level DC voltage smoothed by the positive-side capacitor 5A and the negative-side capacitor 5B is converted into a three-level AC voltage by the three-level inverter 6 to drive the AC motor 6.

  The circuit configuration for one phase of the three-level inverter 6 is shown in FIG. That is, switching elements 61, 62, 63 and 64 are connected in series from the positive potential side to the negative potential side. Free wheel diodes 65, 66, 67 and 68 are connected in antiparallel to each switching element 61, 62, 63 and 64, respectively, between the connection point of the switching elements 61 and 62 and the neutral point, and between the switching elements 63 and 64. By connecting clamp diodes 69 and 70 between the connection point and the neutral point, the potential at these connection points is clamped to zero potential. And it becomes the structure which obtains the alternating current output for one phase from the connection point of the switching elements 63 and 62, and becomes a structure which can obtain the three-phase three-phase alternating current output by providing the same circuit for two more phases. .

  An initial charging circuit 8 is provided in order to prevent an excessive inrush current from flowing through the positive capacitor 5A and the negative capacitor 5B at the start of operation of the apparatus. The initial charging circuit 8 rectifies the output of the transformer 82 that boosts the low-voltage AC voltage via the switch 81, and supplies the DC voltage to the series circuit of the positive-side capacitor 5A and the negative-side capacitor 5B. The rectifier 83 is configured. The initial charging circuit 8 charges the positive-side capacitor 5A and the negative-side capacitor 5B to appropriate values, and then DC power is supplied from the DC power source 1. A resistor may be provided in series on the output side of the rectifier 83 in order to suppress the charging current during initial charging, but this is not necessary when the charging current is suppressed by the resistance of the transformer 82.

  The input voltage of the AC motor 7 is rectified by a three-phase diode bridge 9, and a thyristor 10 is connected in parallel with the DC output. When the thyristor 10 is fired, the output of the three-phase diode bridge 9 is short-circuited.

  A firing auxiliary capacitor 11 is connected between the anode and cathode of the thyristor 10. When the thyristor 10 is ignited, the ignition auxiliary capacitor 11 rapidly raises the main circuit current by the discharge, and instantaneously equalizes the current flowing in the junction plane of the thyristor 10. This prevents incomplete firing and the thyristor 10 is safely and quickly turned on.

  The ignition auxiliary capacitor 11 only needs to have a capacity sufficient to supply the discharge current as described above, but when the three-level inverter 6 is operated, the inrush current to the ignition auxiliary capacitor 11 becomes excessive. There is a fear. For this reason, the positive electrode of the ignition auxiliary capacitor 11 and the positive electrode of the positive capacitor 5A are connected via the resistor 12, and the negative electrode of the ignition auxiliary capacitor 11 and the negative electrode of the negative capacitor 5B are connected via the resistor 13. Connect. With such a circuit configuration, the initial charging circuit 8 can initially charge the positive-side capacitor 5A and the negative-side capacitor 5B, and at the same time, the ignition auxiliary capacitor 11 can be initially charged. Note that either the resistor 12 or the resistor 13 may be omitted.

  In the above configuration, when any of the switching elements, freewheel diodes, or clamp diodes constituting the three-level inverter 6 is short-circuited, a route for charging the capacitor 5A or 5B with the line voltage of the AC motor 7 is formed. Overcharging occurs, and in some cases, an event that the capacitor 5A or 5B is damaged occurs. At this time, a means for detecting the short-circuit fault not shown in FIG. 1 is provided, and the gate block of each switching element is instantaneously performed by this detection signal. However, the charging route remains due to the short-circuit fault of the element. Therefore, overcharging cannot be resolved with the gate block alone. For this reason, the thyristor 10 is fired by the detection signal of the short-circuit fault detection means. By the ignition of the thyristor 10, the line voltage of the AC motor 7 is substantially short-circuited and rapidly decreases, so that overvoltage of the capacitor 5A or 5B can be prevented. Since the thyristor 10 requires a short-circuit withstand capability at this time, an element having a large joint area is required. Therefore, the role of the starting auxiliary capacitor 11 becomes important.

  In the first embodiment, even when the switching elements constituting the three-level inverter 6 have a multi-series configuration, basically the same protection device can be applied. The same applies to Example 2 and Example 3 described below.

  FIG. 2 is a circuit configuration diagram of the protection device for the power conversion device according to the second embodiment of the present invention. In each part of the second embodiment, the same parts as those of the protection device of the power conversion apparatus according to the first embodiment of the present invention shown in FIG. The second embodiment is different from the first embodiment in that the DC power source 1 is replaced with a transformer 2, a switch 3, and a three-level converter 4, and on the input side (power supply system side) of the three-level converter 4. Also, the three-phase diode bridge 14, the thyristor 15 that short-circuits the DC output thereof, the ignition auxiliary capacitor 16, and the initial charging resistors 17 and 18 are provided.

  The three-level converter 4 has the same configuration as the three-level inverter 6, and the three-phase diode bridge 14, the thyristor 15, the ignition auxiliary capacitor 16, and the resistors 17 and 18 on the power supply system side are respectively three-phase diodes on the motor side. Since the bridge 9, the thyristor 10, the ignition auxiliary capacitor 11, and the resistors 12 and 13 have the same configuration, their descriptions are omitted.

  By adopting such a configuration shown in FIG. 2, in addition to the case where a short-circuit fault occurs inside the three-level inverter 6, even if a short-circuit fault occurs inside the three-level converter 4, the thyristor By firing 15, overvoltage of the capacitor 5 </ b> A or the capacitor 5 </ b> B can be prevented.

  FIG. 3 is a circuit configuration diagram of the protection device for the power conversion device according to the third embodiment of the present invention. In each part of the third embodiment, the same parts as those of the protection device of the power conversion apparatus according to the second embodiment of the present invention shown in FIG. The third embodiment is different from the second embodiment in that the DC outputs of the three-phase diode bridge 9 and the three-phase diode bridge 14 are connected to each other, and the thyristor 15, the ignition auxiliary capacitor 16, and the resistors 17 and 18 are omitted. This is the point.

  If the thyristor 10, the ignition auxiliary capacitor 11, and the resistors 12 and 13 are operated not only on the motor side but also on the power supply system side as in the third embodiment, compared to the second embodiment. The number of parts can be greatly reduced. Here, the short-circuit withstand capability of the thyristor 10 may be basically the same as that of the second embodiment unless considering that the 3-level converter 4 and the 3-level inverter 6 cause a short-circuit failure at the same time. In consideration of simultaneous short-circuit failures, the short-circuit tolerance may be approximately doubled.

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Transformer 3 Switch 4 3 level converter 5A Positive side capacitor 5B Negative side capacitor 6 3 level inverter 7 AC motor 8 Initial charging circuit 9, 14 Three-phase diode bridge 10, 15 Thyristor 11, 16 For auxiliary firing Capacitors 12, 13, 17, 18 Resistors 61, 62, 63, 64 Switching elements 65, 66, 67, 68 Freewheel diode 69, 70 Clamp diode 81 Switch 82 Transformer 83 Rectifier

Claims (5)

3 level DC power supply,
Positive and negative DC capacitors fed from this DC power supply,
A three-level inverter that converts the three-level DC voltage applied to the DC capacitor into an AC voltage to drive the AC motor;
First initial charging means for initially charging the DC capacitor;
A protective device for overvoltage protection of a power converter having a first short-circuit fault detection means for detecting an internal short-circuit fault of the three-level inverter,
A first bridge circuit for rectifying the input of the AC motor;
A first thyristor provided in parallel with the DC output of the first bridge circuit;
A first firing auxiliary capacitor connected between the anode and cathode of the first thyristor;
Second initial charging means for initially charging the first ignition auxiliary capacitor;
A protection device for a power converter, wherein the first thyristor is ignited when the first short circuit failure detecting means detects a short circuit failure. The DC power supply is composed of a three-level converter provided with a second short-circuit fault detecting means for detecting an internal short-circuit fault with an AC power supply as an input,
A second bridge circuit for rectifying the input of the three-level converter;
A second thyristor provided in parallel with the DC output of the second bridge circuit;
A second ignition auxiliary capacitor connected between the anode and cathode of the second thyristor;
A third initial charging means for initially charging the second ignition auxiliary capacitor;
The protection device for a power converter according to claim 1, wherein the second thyristor is ignited when the second short-circuit fault detecting means detects a short-circuit fault. The DC power supply is composed of a three-level converter provided with a second short-circuit fault detecting means for detecting an internal short-circuit fault with an AC power supply as an input,
A second bridge circuit that rectifies the input of the three-level converter and connects the DC output to the DC output of the first bridge circuit;
2. The protection device for a power converter according to claim 1, wherein the first thyristor is ignited when the second short-circuit fault detecting unit detects a short-circuit fault. The second initial charging means includes
4. The three-level DC power source and the DC outputs of the first bridge circuit are connected to each other between positive potentials and negative potentials through resistors. Power converter protection device. The third initial charging means includes
3. The electric power according to claim 2, wherein the three-level DC power source and the DC output of the second bridge circuit are connected to each other between positive potentials and negative potentials through a resistor. Protection device for the conversion device.

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