JP2012090506A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device capable of detecting a breakdown of one of a plurality of capacitors connected in series or in parallel.SOLUTION: There is provided a capacitor abnormality detection circuit comprising a switch unit 7SW, an excitation resistance 8R, a contact resistance 9R, and a diode 10D. The switch unit 7SW includes an excitation circuit and a contact circuit, and the contact circuit is closed when a predetermined amount of current flows through the excitation circuit. The excitation circuit of the switch unit 7SW and the excitation resistance 8R and the contact circuit and the contact resistance 9R are alternately connected in series by an amount equal to the number of serial connections of a capacitor, and this series circuit is connected in parallel to the capacitor. A junction point of the excitation resistance 8R and the next switch unit and a junction point of the contact resistance 9R and the next switch unit are connected, and the diode 10D is connected to a corresponding junction point of the capacitor via these connected points. When excitation of the switch circuit 7SW having the lowest potential is switched off, it is determined that at least one of the capacitors connected in series is short-circuited.

Description

  The present invention relates to a power converter, and more particularly, to a power converter having a function of detecting a short-circuit fault in a smoothing capacitor circuit.

  With the recent increase in voltage and size of power conversion devices, devices that require high voltage and large capacity capacitors have appeared. In such a device, a large number of capacitors are connected in series or in parallel. If the number of capacitors in series and parallel increases, even if the capacitor is partially short-circuited (hereinafter simply referred to as a failure), it cannot be detected as an abnormality of the entire device. May not be noticed until it breaks down and causes great damage. In order to prevent such expansion damage, a capacitor failure detection circuit is usually provided.

  As this failure detection circuit, a method of monitoring a DC voltage is common, but as described above, if the number of capacitors in series and parallel increases, a circuit for monitoring the voltage of each capacitor is not provided. The problem cannot be solved. Therefore, the failure detection circuit becomes complicated.

  On the other hand, by connecting the middle points of series and parallel capacitors with a diode bridge, it consists of a level detector that detects the voltage between the DC voltage terminals of the diode bridge, and by monitoring the output of this level detector Proposals have been made to detect failure of individual capacitors (see, for example, Patent Document 1).

JP-A-8-62270 (page 3-4, FIG. 1)

  In the technique disclosed in Patent Document 1, the intermediate point of a capacitor is rectified by a diode bridge circuit, the voltage between the DC terminals of the diode bridge is detected by a level detector, and one of the capacitors fails depending on the detection level. Detect whether or not According to this technique, it is described that a large number of capacitor circuits connected in series and in parallel can be used, and that the detection circuit can be constructed at a single location and at a low cost. However, there is a problem that an intermediate point cannot be obtained unless the number of capacitors connected in series is a multiple of two. Also, if the number of capacitors in series and parallel is large, even if the number of capacitors connected in series is a multiple of two, when one capacitor fails, the voltage fluctuation level decreases, so detection There is a problem that is difficult and unreliable. There is also a problem that detection becomes difficult when one point of series and parallel connection of capacitors is grounded or neutral point.

  The present invention has been made in view of the above problems, and even when a plurality of capacitors are connected in series and in parallel, a failure of one capacitor can be reliably detected with a relatively simple circuit. It aims at providing the power converter device provided with the failure detection circuit.

  In order to achieve the above object, a power conversion device of the present invention includes a converter that converts an AC voltage of an AC power source into a DC voltage, and a series connection for smoothing the DC voltage. A first capacitor circuit configured by N capacitors (N is an integer of 2 or more) defined as second,..., N, and the same configuration as the first capacitor circuit; A second capacitor circuit provided in parallel with the capacitor circuit; and a capacitor abnormality detection circuit that detects that any of the 2N capacitors has a short circuit failure. The capacitor abnormality detection circuit includes: an excitation circuit; , A contact circuit that closes the contact by this excitation current, and N switch circuits defined as first, second,..., N from the high potential side, and excitation of each of the N switch circuits. Alternating with circuit N excitation resistors connected to each other, and N contact resistors connected alternately in series with the contact circuits of each of the N switch circuits, and the first capacitor circuit One end of an excitation circuit and a contact circuit of the first switch circuit is connected to the high potential side of the capacitor, and a first excitation resistor connected to the first switch circuit and an excitation circuit of the second switch circuit The first connection point is connected to the connection point between the first contact resistance connected to the first switch circuit and the contact circuit of the second switch circuit. At the same time, a first diode is connected in a direction in which a current flows from the first connection point to the high potential side of the second capacitor of the first capacitor circuit. Similarly, the first K {K = 2, 3 ,... (N-1)} at the connection point of the Kth switch circuit. And the connection point of the contact circuit of the (K + 1) th switch circuit is connected to the connection point of the (K + 1) th capacitor of the first capacitor circuit from the Kth connection point. The Kth diode is connected in the direction in which current flows to the high potential side, the other end of the Nth excitation resistor connected to the Nth switch circuit, and the Nth contact resistance connected to the Nth switch circuit Are connected to the low potential side of the Nth capacitor of the first capacitor circuit, and the second to (K + 1) th of the second capacitor circuit are respectively connected from the first to Kth connection points. At least one of the 2N capacitors is connected when K diodes are respectively connected in the direction in which a current flows to the high potential side of the capacitor, and excitation of the Nth switch circuit is turned off during operation of the converter. Is found to have failed. Is characterized in that the the to.

  According to the present invention, there is provided a power conversion device including a failure detection circuit capable of reliably detecting a failure of one capacitor with a relatively simple circuit even when a plurality of capacitors are connected in series and in parallel. It becomes possible.

The circuit block diagram of the power converter device which concerns on Example 1 of this invention. The internal block diagram of the switch circuit of the power converter device which concerns on Example 1 of this invention. The time chart explaining operation | movement of the power converter device which concerns on Example 1 of this invention. The circuit block diagram of the power converter device which concerns on Example 2 of this invention. The circuit block diagram of the standardization unit for capacitor | condenser failure detection circuits used for 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.

  Hereinafter, the power converter concerning Example 1 of the present invention is explained with reference to Drawing 1 thru / or Drawing 3.

  FIG. 1 is a circuit configuration diagram of a power conversion apparatus according to Embodiment 1 of the present invention. An AC voltage is supplied from the three-phase AC power source 1 to the converter 3 via the switch 2. The converter 3 is composed of, for example, a diode connected in a bridge, and converts an AC voltage into a DC voltage. The converter 3 may be a self-excited type using a switching element. This DC voltage is smoothed by the smoothing capacitor circuit 4 and the capacitor circuit 5 connected in parallel therewith, and is supplied to the inverter 30. The inverter 30 drives the AC motor 40 by converting the DC voltage into an AC voltage again.

  The capacitor circuit 4 is configured by connecting capacitors 4C1, 4C2, and 4C3 in series. Similarly, the capacitor circuit 5 is configured by connecting capacitors 5C1, 5C2, and 5C3 in series.

  The capacitor failure detection circuit 20 detects that any of the capacitors 4C1, 4C2, and 4C3 and the capacitors 5C1, 5C2, and 5C3 has failed. Hereinafter, the internal configuration of the capacitor failure detection circuit 20 will be described.

  The capacitor failure detection circuit 20 includes the same number of switch circuits 7SW1, 7SW2, and 7SW3 as the series number of the capacitor circuits 4 and 5. FIG. 2 shows an internal configuration of the switch circuit 7SW having the same configuration as these. As shown in FIG. 2, in the switch circuit 7SW, a current exceeding a predetermined value flows through the exciting coil 7EX and a series circuit (hereinafter referred to as an exciting circuit) by a resistor 7SR provided in series therewith, and the exciting coil 7EX. It is composed of a contact 7MS circuit (hereinafter referred to as a contact circuit) that is sometimes closed.

  One end of the excitation circuit of the switch circuit 7SW1 and one end of the contact circuit are connected to the high potential end of the capacitor 4C1 (the positive potential end of the converter 3). Then, the other end of the excitation circuit of 7SW1 is switched to one end of the excitation circuit of the switch circuit 7SW2 via the excitation resistor 8R1 for adjusting the excitation current, and the other end of the contact circuit of SW1 is switched via the contact resistor 9R1 for voltage sharing. Connect to one end of the contact circuit of the circuit 7SW2. Then, one end of the excitation circuit of the switch circuit 7SW2 and one end of the contact circuit of the switch circuit 7SW2 are connected to each other, and the diode 10D1 is connected in a direction in which current flows from the connection point to the high potential end of the capacitor 4C2. Further, the diode 11D1 is connected in a direction in which current flows from the connection point to the high potential end of the capacitor 5C2.

  Similarly, the other end of the excitation circuit of 7SW2 is connected to one end of the excitation circuit of the switch circuit 7SW3 via the excitation resistor 8R2, and the other end of the contact circuit of 7SW2 is connected to the contact circuit of the switch circuit 7SW3 via the contact resistor 9R2. Connect to one end. One end of the excitation circuit of the switch circuit 7SW3 and one end of the contact circuit of the switch circuit 7SW3 are connected to each other, and the diode 10D2 is connected in a direction in which a current flows from the connection point to the high potential end of the capacitor 4C3. Further, the diode 11D2 is connected in a direction in which a current flows from the connection point to the high potential end of the capacitor 5C3. Then, the other end of the excitation circuit of the switch circuit 7SW3 having the lowest potential and the other end of the contact circuit are connected to the low potential end of the capacitor 4C3 (the negative potential end of the converter 3) via the excitation resistor 8R3 and the contact resistor 9R3, respectively. .

  The capacitor abnormality detector 21 determines that any of the capacitors 4C1, 4C2, and 4C3 and the capacitors 5C1, 5C2, and 5C3 has failed when the voltage across the contact resistance 9R3 becomes equal to or lower than a predetermined value during operation of the converter 3. To do.

  The above-described configuration shown in FIG. 1 is a case where the number of series capacitors is 3, but even when the number of series increases, the same connection as described above may be performed. That is, the connection related to the switch circuit 7SW having the highest potential is the same as the connection of the switch circuit 7SW1, the connection related to the switch circuit 7SW having the lowest potential is the same as the connection of the switch circuit 7SW3, and all the other switch circuits 7SW are related. The connection may be the same as the connection of the switch circuit 7SW2.

  Hereinafter, the operation of the capacitor failure detection circuit 20 will be described. First, if the capacitors 4C1, 4C2 and 4C3 in the capacitor circuit 4 and the capacitors 5C1, 5C2 and 5C3 in the capacitor circuit 5 are all normal during the operation of the converter 3, the excitation circuits of the switch circuits 7SW1, 7SW2 and 7SW3 are used. The exciting current flows and all the contact circuits are closed. For example, the current flowing through the excitation circuit of the switch circuit 7SW1 is a value obtained by dividing the voltage applied to the capacitor 4C1 by the sum of the resistor 8R1 and the resistor 7SR.

  In this state, for example, a state transition when the capacitor 4C1 breaks down and becomes a short circuit state will be described with reference to FIG. As shown in the figure, it is assumed that the capacitor 4C1 has failed at time t = T0. Due to this failure, the voltage applied to the capacitor 4C1 instantaneously becomes zero. Accordingly, since no current flows through the excitation circuit of the switch circuit 7SW1, the contact 7MS is opened, and the contact circuit of the switch circuit 7SW1 is opened. Although the voltage applied to the capacitors 4C2 and 4C3 other than the failed capacitor 4C1 is about 1.5 times, the forward voltage of the diodes 10D1 and 10D2 instantaneously becomes zero as shown in the figure, so that the excitation of the switch circuit 7SW2 No current flows through the excitation circuit of the circuit and the switch circuit 7SW3, and the contact circuits of the switch circuit 7SW2 and the switch circuit 7SW3 are also opened. For this reason, when the capacitor 4C1 breaks down from a normal state where the voltage across the contact resistor 9R3 exceeds a predetermined value during operation of the converter 3, the voltage across the contact resistor 9R3 becomes zero. Therefore, the failure detection of the capacitor 4C1 can be performed. By incorporating this failure signal into the protection sequence of the power converter and turning off the switch 2 in FIG. 1, it becomes possible to prevent the failure from expanding to the capacitors 4C2 and 4C3 that are in an overvoltage state. If the converter 3 is self-excited, the converter 3 may be gate-blocked instead of turning off the switch 2.

  The important point here is that the discharge current from the capacitor 5C1 is prevented from flowing due to the presence of the diode 10D1 when the capacitor 4C1 fails and is short-circuited. Further, assuming that the capacitor 5C1 has failed, the failure detection operation is similar to the above, but the discharge current from the capacitor 4C1 does not flow due to the presence of the diode 11D1. Since the above is true for all capacitors, the circuit configuration in FIG. 1 prevents the failure of one of the parallel-connected capacitors due to excessive discharge current flowing through the other. It can be seen that they are configured as described above.

  Next, when the capacitor 4C2 fails and becomes short-circuited, the voltage applied to the capacitor 4C2 due to this failure instantaneously becomes zero. Therefore, no current flows through the excitation circuit of the switch circuit 7SW2, so that the contact circuit of the switch circuit 7SW2 is opened. Also in this case, due to the action of the diodes 10D1 and 10D2, no current flows through the excitation circuit of the switch circuit 7SW3, and the contact circuit of the switch circuit 7SW3 is also opened. The basic operation when the capacitor 5C2 fails and is short-circuited is the same as described above.

  Further, when the capacitor 4C3 fails and is short-circuited, the voltage applied to the capacitor 4C3 instantaneously becomes zero due to this failure, so that no current flows through the excitation circuit of the switch circuit 7SW3. The circuit is opened. The basic operation when the capacitor 5C3 fails and is short-circuited is the same as described above.

  Thus, no matter which capacitor is short-circuited, no current flows through the excitation circuit of the switch circuit 7SW3 having the lowest potential. Therefore, if the capacitor abnormality detector 11 detects the state of the switch circuit 7SW3 attached to the place having the lowest potential, it is possible to detect a short-circuit failure of any one of the capacitors.

  As described above, according to the present embodiment, any one of the capacitors connected in series is reliably detected as a short circuit failure, and the sound capacitors including the capacitors connected in parallel with the failed capacitors are protected. It becomes possible.

  Here, a commercially available inexpensive relay can be used for the switch circuit 7SW. The relay contact 7MS is turned on (a contact) while the relay coil 7EX is excited. The same detection is possible even if the relay contact is a b contact. When this is detected by a circuit similar to that in FIG. 1, the operation is reversed, and when the voltage across the contact resistor 9R3 is zero when the normal value is greater than or equal to a predetermined value, any one capacitor is What is necessary is just to judge that it was out of order.

  Further, it is not always necessary to detect the voltage across the contact resistor 9R3 with the capacitor abnormality detector 21, and as described above, the change in the excitation state of the switch circuit 7SW3 attached to the portion having the lowest potential can be detected by some method. It ’s fine. For example, the voltage of the exciting resistor 8R3 may be detected, or a contact circuit may be further provided in the switch circuit 7SW3 to detect the on / off state. Further, the photoelectric conversion element may be used for a contact circuit or an excitation circuit to detect insulation by light.

  In general, when capacitors are connected in series, there is a variation in the capacitance of each capacitor. Therefore, a resistor is connected in parallel with the capacitor to balance the voltage between the capacitors. The excitation resistors 8R1, 8R2 and 8R3 can be used also as the balance resistor. Further, the contact resistors 9R1, 9R2 and 9R3 may also be used as the balance resistor.

  FIG. 4 is a circuit configuration diagram of the power conversion apparatus according to the second embodiment of the present invention. About each part of this Example 2, the same part as each part of the power converter device which concerns on Example 1 of this invention of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The second embodiment is different from the first embodiment in that a capacitor circuit 6 composed of a series circuit of capacitors 6C1, 6C2, and 6C3 is provided, a diode 12D1 is provided, and a current flows from the anode end of the diode 11D1. Is connected to the high potential end of the capacitor 6C2, and a diode 12D2 is provided, and is connected to the high potential end of the capacitor 6C3 in a direction in which current flows from the anode end of the diode 11D2.

  In the circuit configuration shown in FIG. 4, the capacitor circuits 4, 5, and 6 are all connected in parallel under the same conditions as seen from the series circuit of the switch circuits 7SW1, 7SW2, and 7SW3 provided for detecting an abnormality. Can be said. Therefore, as described in the first embodiment, even when any of the capacitors 6C1, 6C2, and 6C3 fails, the failure detection by the capacitor abnormality detector 21 is possible, and the capacitor circuit is provided by the diodes 12D1 and 12D2. Even if any of the capacitors constituting 4 or 5 fails, an excessive discharge current is prevented from flowing. That is, even in the case of the second embodiment, it is possible not only to detect any of the capacitors that constitute the whole, but also to detect a capacitor connected in parallel with the capacitor. There is no discharge current.

  In this embodiment, the number of capacitor circuits provided in parallel is three. However, even when the number of capacitor circuits is increased further, as described above, the switch circuits 7SW1, 7SW2 and It can be seen from the 7SW3 series circuit that the diodes may be connected so that all the capacitor circuits are connected in parallel under the same conditions.

  In addition, by incorporating the failure signal of the capacitor abnormality detector 21 into the protection sequence of the power converter and turning off the switch 2 in FIG. 3, it is possible to prevent the failure from being expanded to the overvoltage capacitor. This is the same as in the first embodiment.

  FIG. 5 is a circuit configuration diagram of a standardization unit for a capacitor failure detection circuit used in the power conversion apparatus according to Embodiment 3 of the present invention. As shown in the figure, if the standardization unit 50 incorporating the switch circuit 7SW, the resistor 8R, the resistor 9R, and the diodes 10D and 11D is prepared, the capacitor failure detection circuit 20 shown in the first embodiment can be easily achieved by combining the standardization unit 50. Can be assembled into.

  The terminal configuration of the standardization unit 50 is such that the point where the excitation circuit of the switch circuit 7SW and one end of the contact circuit are connected to each other is the terminal P, the connection point between the contact resistor 9R and the contact 7MS is the terminal D1, and the cathode terminal of the diode 11D is D2. The cathode side of 10D is a terminal N, both ends of the diode 10D are terminals S1 and S2, and both ends of the diode 11D are terminals S3 and S4. As illustrated, the terminal D2 and the terminal S2, the terminal N and the terminal S1, the terminal S2 and the terminal S3, and the terminal D2 and the terminal S4 are the same connection point. The terminals D1 and D2 are provided as voltage detection terminals, and the terminals S1 and S2 and the terminals S3 and S4 are provided for a standardization unit including the switch circuit 7SW3 at the lowest potential as described in FIG. This is a short-circuiting terminal for short-circuiting the diode 10D and the diode 11D.

  In the above, the standardized unit incorporating the switch circuit 7SW1 or 7SW2 in FIG. 1 does not use the terminals D1, S1, and S2, and S3 and S4. Therefore, as the standardized unit, only the three terminals of the terminal P, the terminal D2, and the terminal N are used. A capacitor failure detection circuit may be configured by the standardization unit, and a standardization unit that does not have the diodes 10D and 11D may be applied to a portion having the lowest potential.

  As described above, if the standardization unit 50 shown in FIG. 5 is used, not only the mass productivity is high, but all the products can be constituted by low-pressure products, so that the economy is extremely good.

  In addition, in FIG. 5, it is clear that the standardized unit applicable to the second embodiment can be provided if the diode 12D is provided in parallel with the diode 11D, and even when the capacitor circuit is further increased, It is obvious that a diode having the same configuration may be added.

  Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Switch 3 Converter 4, 5, 6 Capacitor circuit 4C1, 4C2, 4C3, 5C1, 5C2, 5C3, 6C1, 6C2, 6C3 Capacitor 7SW, 7SW1, 7SW2, 7SW3, 7SW4 Switch circuit 7EX Excitation coil 7MS Contact 7SR Resistance 8R, 8R1, 8R2, 8R3 Excitation resistance 9R, 9R1, 9R2, 9R3 Contact resistance 10D, 10D1, 10D2, 11D, 11D1, 11D2, 12D1, 12D2 Diode 20 Capacitor failure detection circuit 21 Capacitor abnormality detector 30 Inverter 40 AC motor 50 Standardization unit

Claims (6)

A converter that converts the AC voltage of the AC power source into a DC voltage;
In order to smooth the DC voltage, a first connected by N (N is an integer of 2 or more) capacitors defined as first, second,..., N from the high potential side. Capacitor circuit,
A second capacitor circuit having the same configuration as the first capacitor circuit and provided in parallel with the first capacitor circuit;
A capacitor abnormality detection circuit for detecting that any of the 2N capacitors has a short circuit failure;
The capacitor abnormality detection circuit is:
An excitation circuit and a contact circuit whose contact is closed by the excitation current, and N switch circuits defined as first, second,..., N from the high potential side;
N exciting resistors connected alternately in series with each exciting circuit of the N switch circuits;
N contact resistors connected alternately in series with the contact circuits of each of the N switch circuits;
Have
One end of the excitation circuit and the contact circuit of the first switch circuit is connected to the high potential side of the first capacitor of the first capacitor circuit,
A connection point between the first excitation resistor connected to the first switch circuit and the excitation circuit of the second switch circuit is defined as a first connection point, and the first switch circuit is connected to the first connection point. And a connection point of the contact circuit of the second switch circuit is connected to the high potential side of the second capacitor of the first capacitor circuit from the first connection point. Connect the first diode in the direction of current flow,
In the same manner, the Kth contact resistance connected to the Kth switch circuit and the (K + 1) th switch circuit are sequentially connected to the Kth {K = 2, 3, ... (N-1)} connection points. A connection point of the contact circuit, and a Kth diode in a direction in which a current flows from the Kth connection point to the high potential side of the (K + 1) th capacitor of the first capacitor circuit,
The other end of the Nth exciting resistor connected to the Nth switch circuit and the other end of the Nth contact resistor connected to the Nth switch circuit are connected to the Nth capacitor of the first capacitor circuit. Connected to the low potential side of
K diodes are connected in the direction in which current flows from the first to Kth connection points to the high potential sides of the second to (K + 1) th capacitors of the second capacitor circuit, respectively.
When the excitation of the Nth switch circuit is turned off during operation of the converter,
It is determined that at least one of the 2N capacitors has a short circuit failure. M capacitor circuits having the same configuration in parallel with the first capacitor circuit are provided in parallel with the first capacitor circuit (M is an integer of 1 or more);
The capacitor abnormality detection circuit is:
The direction in which current flows from the first to Kth connection points to the high potential sides of the second to (K + 1) th capacitors of the Lth (L = 1, 2,... M) capacitor circuits, respectively. The power converter according to claim 1, wherein (M × K) diodes are connected to each other. When the voltage across the Nth contact resistance becomes a predetermined value or less,
The power converter according to claim 1 or 2, wherein at least one of the capacitors is determined to have a short circuit failure.   4. The switch provided on the input side of the converter is turned off or the converter is gate-blocked when the capacitor abnormality detection circuit detects an abnormality. The power converter device according to any one of the above. The capacitor abnormality detection circuit is:
Each of the switch circuit, the excitation resistor, the contact resistance, and Q (Q is an integer of 2 or more), which is the number of the capacitor circuits, are used, and the excitation circuit and the contact circuit of the switch circuit. One end is connected as a first terminal, an excitation resistor is connected to the other end of the excitation circuit, the other end of the excitation resistor is used as a first connection point, and the other end of the contact circuit is connected to the first connection. A contact resistance is connected between the points, Q diodes are connected in a direction in which current flows from the first connection point, and the other ends are connected to the second, third,..., (Q + 1) terminals. The power conversion device according to any one of claims 1 to 4, wherein the standardization unit is configured to be combined.   6. The electric power according to claim 5, wherein a (Q + 2) -th terminal is provided at a connection point between the contact circuit and the contact resistance of the standardization unit, and short-circuit terminals are provided at both ends of each diode. Conversion device.

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