JP4590859B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter and can be applied to an air conditioner, for example.

  The power conversion device includes, for example, a converter that rectifies an input AC voltage, and an inverter that converts a voltage rectified by the converter into an AC voltage such as a three-phase AC voltage. In a conventional power converter, the converter performs only one of voltage doubler rectification and full wave rectification, for example. In particular, when voltage doubler rectification is performed, an abnormality such as a voltage becoming too high may occur.

  Therefore, recently, converters that enable switching between voltage doubler rectification and full-wave rectification have been developed. In this converter, the voltage output from the converter is controlled by controlling switching of rectification. Patent Document 1 discloses such a converter and a technique for controlling the converter.

  Patent Document 2 discloses a technique for controlling a converter or an inverter to protect the inverter or the converter in a power conversion device including a converter that performs only full-wave rectification and an inverter.

Japanese Patent No. 3422218 Japanese Patent Laid-Open No. 11-275869

  In the conventional technique for controlling the converter, the output voltage can be controlled. However, the output voltage is not always accurately controlled, and an abnormality may occur in the output voltage. Considering a power conversion device in which an inverter is connected to the output side of the converter, an abnormally high voltage output from the converter causes an excessive current to flow through the inverter and cause the inverter to fail.

  The present invention has been made in view of the above circumstances, and aims to reduce damage to an inverter when it is estimated that a failure has occurred in the inverter.

The power converter according to claim 1 of the present invention includes a converter (2, C11, C12, S1) that rectifies alternating current, an inverter (4) that converts the output of the converter into alternating current, and a current flowing through the inverter. An inverter abnormality detection unit (102) for detecting an abnormality and outputting a first abnormality detection signal, wherein the converter can switch between full-wave rectification and voltage doubler rectification, and the first abnormality detection signal is There lines the converter full-wave rectification when activated, the converter has a pair of input terminals, wherein the alternating current is supplied, a diode bridge having a pair of output ends (2), of the diode bridge A pair of capacitors (C11, C12) connected in series between the pair of output ends via a connection point (J2), and the pair of input ends of the diode bridge On the other hand, a bidirectional switch (S1) connected between (J1) and the connection point, and a converter current abnormality detection unit (101) for detecting an abnormality of a current flowing through the bidirectional switch and outputting a second abnormality detection signal When the second abnormality detection signal is inactive, the converter rectifies by alternately adopting full-wave rectification and voltage doubler rectification in the half cycle (T / 2) of the alternating current, 2 After the activation of the abnormality detection signal (t2), from the time (t1) when the voltage doubler rectification starts immediately before the activation of the second abnormality detection signal to the time (t3) when the half cycle of the alternating current elapses In the meantime, the converter employs full-wave rectification .

A power converter according to a second aspect of the present invention is the power converter according to the first aspect, wherein a converter voltage abnormality detection that detects a abnormality of the output voltage of the converter and outputs a third abnormality detection signal is provided. (201, 202, G1), and the converter performs full-wave rectification even when the third abnormality detection signal is activated.

A power conversion device according to claim 3 of the present invention is the power conversion device according to claim 2 , wherein the converter voltage abnormality detection unit detects a pair of voltages at both ends of the pair of capacitors. An abnormality detector (201, 202) and a logic element (G1) that activates the third abnormality detection signal when at least one of the pair of voltage abnormality detectors detects an abnormality.

A power converter according to a fourth aspect of the present invention is the power converter according to any one of the second and third aspects, wherein the inverter is activated when the second abnormality detection signal is activated. Is stopped.

According to the power conversion device of the first aspect of the present invention, when it is estimated that a failure has occurred in the inverter, the converter is reduced in output voltage to reduce damage to the inverter. Further, since it is not necessary to cut off the alternating current input to the converter, it is possible to separately control whether or not the alternating current is cut off, and the degree of freedom in design is high. In addition, the converter is protected from overcurrent while performing continuous operation without stopping the converter. The converter also performs voltage doubler rectification when the bidirectional switch is on, and full-wave rectification when the bidirectional switch is off.

  According to the power conversion device of the second aspect of the present invention, even when it is estimated that a failure has occurred in the converter, the damage given to the converter is reduced by reducing the output voltage of the converter.

According to the power conversion device of the third aspect of the present invention, the abnormality of the converter is detected even when the voltage applied to the pair of capacitors is lost.

According to the power conversion device of the fourth aspect of the present invention, when a failure occurs in the converter or the inverter, damage to the inverter is prevented. Further, since it is not necessary to cut off the alternating current input to the converter, it is possible to separately control whether or not the alternating current is cut off, and the degree of freedom in design is high.

  FIG. 1 is a conceptual block diagram showing a voltage converter according to the present invention. The voltage converter includes a main circuit switch S0, a reactor 10, a converter, an inverter 4, an inverter abnormality detection unit 102, a converter voltage abnormality detection unit, a converter current abnormality detection unit 101, and a control unit 3.

  The converter includes a diode bridge 2, capacitors C11, C12, C2, and a bidirectional switch S1. The diode bridge 2 has a pair of input ends to which alternating current is supplied from the power source 1 and a pair of output ends. The pair of output ends of the diode bridge 2 can also be grasped as the output ends of the converter. The capacitors C11 and C12 are connected in series between the pair of output ends of the diode bridge 2 via the connection point J2. The capacitor C <b> 2 is connected in parallel with the capacitors C <b> 11 and C <b> 12 between the pair of output terminals of the diode bridge 2. The bidirectional switch S1 is connected between the connection point J1 to which one of the input ends of the diode bridge 2 is connected and the connection point J2.

  The converter rectifies the alternating current input from the power supply 1. When the bidirectional switch S1 is in the ON state, the AC voltage is voltage doubled rectified. That is, the AC voltage is full-wave rectified by the diode bridge 2, and the voltage is doubled by the capacitors C11 and C12. The voltage rectified voltage is smoothed by the capacitor C2. When the bidirectional switch S1 is in an OFF state, the AC voltage is full-wave rectified by the diode bridge 2. The full-wave rectified voltage is smoothed not only by the capacitor C2 but also by the capacitors C11 and C12. At this time, the capacitors C11, C12, and C2 can be grasped as one smoothing capacitor 5.

  The converter can rectify by switching between full-wave rectification and voltage doubler rectification. This switching is performed when a hardware output circuit 3b included in the control unit 3 described later controls the bidirectional switch S1 to be turned on / off.

  The main circuit switch S0 and the reactor 10 are connected in series between the connection point J1 and the power source 1.

  In the inverter 4, the input end of the inverter 4 is connected to the output end of the converter, and the output end of the inverter 4 is connected to the motor M, for example. The inverter 4 converts the voltage input from the converter side into an AC voltage and outputs it to the motor M. In FIG. 1, a three-phase AC voltage is output from the inverter 4.

  The inverter abnormality detection unit 102 is connected to one of the pair of input terminals of the inverter 4. Further, converter current abnormality detection unit 101 is connected between node J2 and bidirectional switch S1.

  The converter voltage abnormality detection unit includes voltage abnormality detection units 201 and 202 and a logic element G1. The pair of voltage abnormality detectors 201 and 202 are connected in parallel to the pair of capacitors C11 and C12.

  The control unit 3 includes a converter software control unit 301, an inverter software control unit 302, a logic element G2, and hardware output circuits 3b and 3c. The logic element G2 is connected to the converter software control unit 301 via the hardware output circuit 3b, and is connected to the inverter software control unit 302 via the hardware output circuit 3c.

  Regarding the connection with the outside of the control unit 3, the logic terminal G2 is connected to the voltage abnormality detection units 201 and 202 via the logic terminal G1, and is also connected to the inverter abnormality detection unit 102. Converter software control unit 301 is connected to converter current abnormality detection unit 101. The hardware output circuit 3b is connected to the bidirectional switch S1, and the hardware output circuit 3c is connected to the inverter 4.

  For convenience, the structure of the control unit 3 is shown for each block for each function, but it is not always necessary to configure all of them by hardware, and the substantial function may be achieved by a program executable by a computer. In that case, it is desirable to have an interface for connecting the inside and outside of the control unit 3.

  FIG. 2 conceptually shows the relationship between the current flowing through the bidirectional switch and the ON / OFF state of the bidirectional switch, and the relationship between the active / inactive state of the signal output from the converter current abnormality detection 101. FIG. When the converter or inverter is operating normally, that is, when all of the abnormality detection signals output from the abnormality detection units 101, 102, 201, and 202 are inactive, the converter is supplied from the power supply 1. Rectification is performed by alternately adopting full-wave rectification and voltage doubler rectification in an AC half cycle T / 2. For example, FIG. 2 shows a case where on / off of the bidirectional switch corresponding to voltage doubler rectification and full-wave rectification is alternately switched in a half cycle T / 2. Here, the case where the converter or the inverter is operating normally is shown until the first two cycles shown in FIG.

  This control is performed, for example, by the converter software control unit 301 giving an activated signal to the hardware output circuit 3b during the period ΔT in the half cycle T / 2 and an inactive signal during the other periods. Is called. The hardware output circuit 3b controls the bidirectional switch S1 to be turned off when it receives an activated signal and to be turned on when it receives an inactive signal. When the bidirectional switch S1 is on, the converter performs voltage doubler rectification, so that the absolute value of the current flowing through the bidirectional switch S1 increases.

  When the converter obtains a high voltage by voltage double rectification, a failure may occur in the converter or the inverter. Below, the cause of a failure and the control operation | movement with respect to it are shown for every embodiment.

First embodiment.
In the present embodiment, the control operation of the above-described power conversion device will be described in the case where an abnormality such as an overcurrent has occurred in the current flowing through inverter 4.

  The inverter abnormality detection unit 102 detects an abnormality in the current flowing through the inverter 4 and activates and outputs an abnormality detection signal. The abnormality detection signal is given to the logic element G2. When at least one abnormality detection signal is input, the logic element G2 outputs an activated signal. For this reason, as long as the abnormality detection signal input from the inverter abnormality detection unit 102 to the logic element G2 is activated, the logic element G2 is activated regardless of the activation of the signal supplied from the logic element G1 side. Output a signal.

  The activated signal is given to the hardware output circuit 3b. When receiving the activated signal, the hardware output circuit 3b controls the bidirectional switch S1 to turn off. Thereby, the operation of the converter is switched from double voltage rectification to full wave rectification.

  Since the full-wave rectified voltage is lower than the double-voltage rectified voltage, the output voltage of the converter decreases and the current flowing to the inverter also decreases. Therefore, damage to the inverter can be reduced.

  Moreover, the control of the converter mentioned above is performed without interrupting the alternating current input to the converter. Therefore, it is possible to separately control whether or not the AC is interrupted, and the degree of freedom in design is increased.

  The contents of the present embodiment can also be obtained, for example, by the power conversion device shown in FIG. The power conversion device shown in FIG. 3 omits the converter voltage abnormality detection unit, the converter current abnormality detection unit 101, and the logic element G2 from the power conversion device shown in FIG.

Second embodiment.
In the present embodiment, the control operation of the power conversion device shown in FIG. 1 will be described when an abnormality occurs in the output voltage of the converter. An abnormality in the output voltage occurs, for example, when the voltage applied to each of the pair of capacitors C11 and C12 is unbalanced.

  The converter voltage abnormality detection unit detects an abnormality in the output voltage of the converter, activates the abnormality detection signal, and outputs it. In the converter voltage abnormality detection unit, the pair of voltage abnormality detection units 201 and 202 detect abnormality of the voltage at both ends of the capacitors connected in parallel to each other, and output a detection signal. The detection signal is given to the logic element G1. The logic element G1 activates and outputs an abnormality detection signal when at least one of the pair of voltage abnormality detection units 201 and 202 outputs a detection signal.

  The abnormality detection signal is given to the logic element G2. As long as the activated abnormality detection signal is provided from the logic element G1, the logic element G2 outputs the activated signal regardless of the activation of the abnormality detection signal provided from the inverter abnormality detection unit 102.

  The activated signal is given to the hardware output circuit 3b. When receiving the activated signal, the hardware output circuit 3b controls the bidirectional switch S1 to turn off. Thereby, the operation of the converter is switched from double voltage rectification to full wave rectification.

  Since the full-wave rectified voltage is lower than the double-voltage rectified voltage, the output voltage of the converter decreases. Therefore, the damage given to the converter can be reduced.

  For example, when the balance of the voltage applied to each of the pair of capacitors C11 and C12 is lost, the load on one of the capacitors increases. At this time, performing the above-described control is particularly effective because the load on the capacitor is reduced.

  The contents of the present embodiment can also be obtained by, for example, the power conversion device shown in FIG. In the power conversion device shown in FIG. 4, the converter current abnormality detection unit 101 is omitted from the power conversion device shown in FIG. 1.

Third embodiment.
In the present embodiment, the control operation of the power converter shown in FIG. 1 will be described in the case where an abnormality such as an overcurrent has occurred in the current flowing through the converter.

  Converter current abnormality detection unit 101 detects an abnormality of the current flowing through the converter, particularly bidirectional switch S1, and outputs an abnormality detection signal. For example, as shown at time t2 shown in FIG. 2, when the current flowing through the bidirectional switch S1 reaches the upper limit or lower limit of the overcurrent limit value, the converter current abnormality detection unit 101 activates the abnormality detection signal. Output. The abnormality detection signal is given to the converter software control unit 301.

  After a time point t2 when the activated abnormality detection signal is given to the converter software control unit 301, a time point when an AC half cycle T / 2 elapses from a time point t1 when voltage doubler rectification starts immediately before the abnormality detection signal is given. The converter software control unit 301 outputs the activated signal until t3. The activated signal is given to the hardware output circuit 3b. When receiving the activated signal, the hardware output circuit 3b controls the bidirectional switch S1 to turn off. Thereby, the converter employs full-wave rectification. Of the waveform (FIG. 2) indicating the on / off of the bidirectional switch S1, the broken line indicates the operation when no abnormality occurs in the current flowing through the converter.

  The time when the activated signal is output is within the period in which the inactive signal is output when the converter or inverter is operating normally. At this time, the converter software control unit 301 supplies the activated signal to the hardware output circuit 3b even though it is a period during which a signal that is inactive in normal operation is output.

  Since the full-wave rectified voltage is lower than the double-voltage rectified voltage, the output voltage of the converter decreases and the current flowing to the converter also decreases. Therefore, it is possible to reduce damage caused by overcurrent applied to the converter.

  The contents of the present embodiment can also be obtained by, for example, the power conversion device shown in FIG. The power conversion device shown in FIG. 5 omits the converter voltage abnormality detection unit and the logic element G2 from the power conversion device shown in FIG.

  In any of the above-described embodiments, the activated signal output from the logic element G2 may be further supplied to the hardware output circuit 3c. The hardware output circuit 3 c that has received the activated signal stops the inverter 4. As a result, the voltage output from the converter is not input to the inverter 4, and damage to the inverter 4 can be prevented.

  Moreover, the control of the inverter described above is performed without interrupting the AC input to the converter. Therefore, it is possible to separately control whether or not the AC is interrupted, and the degree of freedom in design is increased.

It is a block diagram which shows notionally the power converter device concerning this invention. It is a figure which shows notionally the relationship between the electric current which flows into a bidirectional switch, and ON / OFF of a bidirectional switch. It is a block diagram which shows the power converter device demonstrated by 1st Embodiment. It is a block diagram which shows the power converter device demonstrated by 2nd Embodiment. It is a block diagram which shows the power converter device demonstrated by 3rd Embodiment.

Explanation of symbols

2 Diode bridge 4 Inverter S1 Bidirectional switch C11, C12 Capacitor G1 Logic element J1, J2 Connection point t1, t2, t3 Time point T / 2 Half cycle

Claims (4)

Converters (2, C11, C12, S1) for rectifying alternating current;
An inverter (4) for converting the output of the converter into alternating current;
An inverter abnormality detection unit (102) for detecting an abnormality in the current flowing through the inverter and outputting a first abnormality detection signal;
The converter can rectify by switching between full-wave rectification and voltage doubler rectification,
There lines the converter full-wave rectification when the first abnormality detection signal is activated,
The converter is
A diode bridge (2) having a pair of input ends to which the alternating current is supplied and a pair of output ends;
A pair of capacitors (C11, C12) connected in series via a connection point (J2) between the pair of output ends of the diode bridge;
A bidirectional switch (S1) connected between one of the pair of input ends (J1) of the diode bridge and the connection point;
Converter current abnormality detection part (101) which detects abnormality of the current flowing through the bidirectional switch and outputs a second abnormality detection signal
Further comprising
When the second abnormality detection signal is inactive, the converter rectifies by alternately adopting full-wave rectification and voltage doubler rectification in the half cycle (T / 2) of the alternating current,
After the second abnormality detection signal is activated (t2), the time when the half cycle of the alternating current elapses from the time (t1) when the voltage doubler rectification starts immediately before the activation of the second abnormality detection signal (t3) In the meantime, the converter adopts full-wave rectification . Converter voltage abnormality detection unit (201, 202, G1) that detects abnormality of the output voltage of the converter and outputs a third abnormality detection signal
Further comprising
The power conversion device according to claim 1, wherein the converter performs full-wave rectification even when the third abnormality detection signal is activated. The converter voltage abnormality detection unit is
A pair of voltage anomaly detectors (201, 202) for detecting an anomaly in the voltage across each of the pair of capacitors;
A logic element (G1) that activates the third abnormality detection signal when at least one of the pair of voltage abnormality detectors detects an abnormality;
The power conversion device according to claim 2, comprising: The power converter according to any one of claims 2 and 3 , wherein the inverter is stopped when the third abnormality detection signal is activated .

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