JP5660916B2 - Power converter and air conditioner - Google Patents

Description

  The present invention relates to a power converter and an air conditioner.

  A conventional power converter for a three-phase AC power supply is configured to connect three reactors on the AC power supply side in order to improve the power factor and comply with the harmonic current standard (see, for example, Patent Document 1 below). .

JP 2004-166359 A

  However, the conventional power converter for a three-phase AC power supply is configured to connect three low-frequency reactors. Therefore, when the output load is large, it is necessary to increase the size of the reactor in order to secure the current capacity, and there is a problem that the size of the electric product becomes very large. Further, since the size of the reactor is increased, there is a problem that the total heat generation amount is large, the mounting restrictions on the substrate and the electronic components are increased, and the cost of the electrical product is significantly increased.

  The present invention has been made in view of the above, and a power conversion device capable of suppressing an increase in the size of a reactor on the AC power supply side while complying with the harmonic current standard even when the output load is large The purpose is to obtain.

In order to solve the above-described problems and achieve the object, the present invention provides a power converter that converts AC power supplied from an AC power source into DC power, and a rectifier circuit that rectifies the AC power into DC power. And a smoothing capacitor for smoothing the DC power, an AC side reactor connected to each phase of the AC power supply, a DC side reactor connected to the DC side of the rectifier circuit, and the smoothing capacitor. A resonance capacitor, a connection point between the AC side reactor and the rectifier circuit, a switching unit having a switch provided between the resonance capacitor, and a current detection unit for detecting a current of the AC power; A voltage detection unit for detecting the voltage of the AC power, an AC side short circuit switching unit for switching whether or not the AC side reactor is short-circuited, and a short circuit for the DC side reactor Whether a DC short-circuit switching portion that switches whether, and a control unit for controlling the opening and closing of the switch to perform a switching operation in a pattern generated by a predetermined calculation processing based on the voltage, wherein, When the current is less than or equal to a predetermined threshold value, the AC side reactor is controlled to be short-circuited without short-circuiting the AC-side reactor, and when the current exceeds a predetermined threshold value, the AC-side reactor is short-circuited. The direct current side reactor is controlled not to be short-circuited, and the switching operation is controlled to be stopped .

  According to the present invention, even when the output load is large, an increase in the size of the reactor on the AC power supply side can be suppressed while complying with the harmonic current standard.

FIG. 1 is a diagram illustrating a configuration example of the power conversion device according to the first embodiment. FIG. 2 is a diagram illustrating a circuit configuration example of the semiconductor switch. FIG. 3 is a diagram illustrating a circuit configuration example of the semiconductor switch. FIG. 4 is a diagram showing a circuit configuration example of a semiconductor switch having a unidirectional electronic contact. FIG. 5 is a diagram illustrating a circuit configuration example of a semiconductor switch having electronic contacts in one direction. FIG. 6 is a diagram illustrating a configuration example of the power conversion device according to the fourth embodiment. FIG. 7 is a diagram illustrating a configuration example of an outdoor unit of the air conditioner according to the fifth embodiment.

  Hereinafter, embodiments of a power conversion device and an air conditioner according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a first embodiment of a power conversion device according to the present invention. As shown in FIG. 1, the power converter of this embodiment includes an AC power source 1, reactors (AC side reactors) 2-1 to 2-3, a rectifier diode bridge (rectifier circuit) 3, and a reactor (DC side reactor) 4. , Smoothing capacitors (smoothing circuits) 5-1, 5-2, inverter (inverse conversion unit) 6, resonant capacitor 8, voltage detection unit 10, current detection unit 11, control unit 12, inverter control unit 13, first switch A group (AC side short circuit switching unit) 14, a second switch group (switching unit) 15, and a third switch group (DC side short circuit switching unit) 16 are provided to control the motor 7.

  The AC power source 1 is a three-phase AC power source, and the reactors 2-1 to 2-3 are connected to the respective phases of the AC power source 1. The rectifying diode bridge 3 includes diodes 17-1 to 17-6. The rectifier diode bridge 3 is connected to the reactors 2-1 to 2-3 on the input side, and the positive side of the output is connected to the positive side of the smoothing capacitor 5-1 via the reactor 4. The smoothing capacitors 5-1 and 5-2 are connected in series, and the negative side of the output of the rectifying diode bridge 3 is connected to the negative side of the smoothing capacitor 5-2. Here, an example in which the rectifier diode bridge 3 is used as the rectifier circuit will be described. However, the configuration of the rectifier circuit is not limited, and is not limited to the configuration example shown as the rectifier diode bridge 3.

  An inverter 6 is connected in parallel to the smoothing capacitors 5-1 and 5-2. The inverter 6 is connected to the motor 7 and drives / stops the motor 7. The inverter 6 converts the DC power obtained from the motor 7 into AC power. The first switch group 14 includes bidirectional switches 18-1 to 18-3, and the bidirectional switches 18-1 to 18-3 are connected in parallel to the reactors 2-1 to 2-3, respectively. . That is, the first switch group 14 is a circuit that switches between a short-circuited state and a non-short-circuited state with respect to the reactors 2-1 to 2-3, and when the bidirectional switches 18-1 to 18-3 are turned on. Reactors 2-1 to 2-3 are short-circuited.

  The second switch group 15 has built-in bidirectional switches 18-4 to 18-6, and the bidirectional switches 18-4 to 18-6 are connected to the AC lines downstream of the reactors 2-1 to 2-3. And connected to the intermediate point of the smoothing capacitor 5-1 and the smoothing capacitor 5-2 through the resonance capacitor 8.

  The third switch group 16 includes one or more switches 18-7 and is connected to the reactor 4 in parallel. That is, the 3rd switch group 16 is a circuit which switches the state short-circuited about the reactor 4, and the state which is not short-circuited, and short-circuits the reactor 4 when switch 18-7 is set to ON.

  The voltage detection unit 10 is connected to the AC power source 1, detects the AC power source voltage of the AC power source 1 and the power source synchronization timing, and outputs the detection result to the control unit 12. The current detection unit 11 detects a one-phase current in the three-phase AC power supply 1 and outputs the detection result to the control unit 12.

  The control unit 12 controls the first switch group 14, the second switch group 15, and the third switch group 16 based on the voltage detected by the voltage detection unit 10 and the current detected by the current detection unit 11. The inverter control unit 13 controls the inverter 6. In addition, the control unit 12 and the inverter control unit 13 exchange control information and the like with each other.

  Next, the operation will be described. The control unit 12 determines whether or not the input current flowing through the power conversion device is small based on the current detected by the current detection unit 11 (for example, the current detected by the current detection unit 11 is equal to or less than a predetermined threshold value). Whether or not the input current flowing through the power conversion device is small). And when the control part 12 judges that the input current which flows into a power converter device is small, while controlling the bidirectional | two-way switches 18-1 to 18-3 in the 1st switch group 14 to always turn OFF, The bidirectional switches 18-4 to 18-6 in the second switch group 15 are controlled to perform a switching operation according to a pattern calculated according to the voltage value detected by the voltage detection unit 10 and the power supply synchronization timing, The switch 18-7 of the switch group 16 is controlled to be always ON. Specifically, as the switching operation, for example, the control unit 12 controls the bidirectional switches 18-4 to 18-6 connected to each phase so as to open and close once or several times in each half cycle of the power source. To do.

  By such an operation, the harmonic current can be suppressed, and the input current flowing through the power converter can satisfy the harmonic current standard (for example, IEC (International Electrotechnical Commission) 61000-3-2).

  On the other hand, the control unit 12 always switches the bidirectional switches 18-1 to 18-3 in the first switch group 14 when the input current flowing through the power conversion device is large based on the current detected by the current detection unit 11. The bidirectional switches 18-4 to 18-6 in the second switch group 15 are controlled to stop the switching operation, and the switch 18-7 of the third switch group 16 is controlled to be always OFF.

  When the input current flowing through the power converter is large (16 A or more), the harmonic current standard (for example, IEC61000-3-12) relaxed from IEC61000-3-2 is applied. Therefore, the switching operation of the bidirectional switches 18-4 to 18-6 in the second switch group 15 is stopped and the reactor 4 is used, so that the input current flowing through the power converter is a harmonic current standard (for example, IEC61000). −3-12) can be satisfied.

  As the bidirectional switches 18-1 to 18-3 of the first switch group 14, for example, switches having mechanical contacts such as a power relay can be used. Further, as each of the bidirectional switches 18-1 to 18-3 of the first switch group 14, a switch having an electronic contact constituted by a semiconductor circuit may be used. 2 and 3 are diagrams showing circuit configuration examples of switches (semiconductor switches) configured by semiconductor circuits. In the configuration example of FIG. 2, the semiconductor switch is configured by four diodes 20 and transistors 21, and in the configuration example of FIG. 3, the semiconductor switch is configured by two diodes 20 and two transistors 21. For example, the semiconductor switches shown in FIGS. 2 and 3 can be used as the bidirectional switches 18-1 to 18-3. The circuit configuration of the semiconductor switch is not limited to the examples of FIGS.

  As the switch 18-7 of the third switch group 16, for example, a switch having a mechanical contact such as a power relay can be used. Further, as the switch 18-7 of the third switch group 16, a switch having a one-way electronic contact constituted by a semiconductor circuit may be used. FIG. 4 and FIG. 5 are diagrams showing circuit configuration examples of a switch (semiconductor switch) having a unidirectional electronic contact configured by a semiconductor circuit. In the configuration example of FIGS. 4 and 5, the semiconductor switch is configured by a P-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) 22 or an N-type MOSFET 23. For example, the semiconductor switch shown in FIGS. 4 and 5 can be used as the switch 18-7. The circuit configuration of the semiconductor switch used as the switch 18-7 is not limited to the examples of FIGS.

  As the bidirectional switches 18-4 to 18-6 of the second switch group 15, electronic contacts configured by semiconductor circuits are used. For example, the semiconductor switch having the circuit configuration shown in FIGS. 2 and 3 can be used. When a semiconductor switch is used, a Si semiconductor or the like may be used, but a wide gap semiconductor may be used. Examples of the wide band gap semiconductor include silicon carbide, a gallium nitride-based material, and diamond.

  Since the switching element formed of such a wide band gap semiconductor has high voltage resistance and high allowable current density, the switching element can be reduced in size. By using these reduced switching elements, A semiconductor module incorporating these elements can be miniaturized.

  In addition, since the wide band gap semiconductor has high heat resistance, it is possible to reduce the size of the heat dissipating fins of the heat sink and the air cooling of the water cooling portion, thereby further reducing the size of the semiconductor module.

  Furthermore, since the wide band gap semiconductor has low power loss, it is possible to increase the efficiency of the switching element, and further increase the efficiency of the semiconductor module.

  The rectifying diode bridge 3 may also use the above-described wide band gap semiconductor for the diodes 17-1 to 17-6.

  In the present embodiment, the configuration in which the reactor 4 and the third switch group 16 that short-circuits the reactor 4 are connected to the positive side of the smoothing capacitor 5-1 has been described. The third switch group 16 may be configured such that the reactor 4 is connected to the negative side of the smoothing capacitor 5-2.

  As described above, in the present embodiment, the control unit 12, the first switch group 14 for short-circuiting the reactors 2-1 to 2-3, and the third switch group 16 for short-circuiting the reactor 4 are used. When the control unit 12 determines that the input current flowing through the power converter is small, the first switch group 14 and the first switch 14 are short-circuited without causing the reactors 2-1 to 2-3 to be short-circuited. 3 switch group 16 and a switching operation according to the voltage value of AC power supply 1. The control unit 12 controls the first switch group 14 and the third switch group 16 so that the reactors 2-1 to 2-3 are short-circuited and the reactor 4 is not short-circuited when the input current flowing through the power converter is large. In addition, the switching operation is stopped. Therefore, even when the output load is large, an increase in the size of the reactor on the AC power supply side can be suppressed while complying with the harmonic current standard.

Embodiment 2. FIG.
Next, a second embodiment of the power conversion device according to the present invention will be described. In the first embodiment, the method of suppressing the harmonic current in the case where the input current flowing through the power converter is small or large is described. In the present embodiment, the circuit switching (reactor (reactor 4 or reactors 2-1 to 2-3) to be short-circuited) is switched without stopping the inverter 6 when the input current flowing through the power converter changes, and A power conversion device capable of performing switching / execution of switching operation) will be described.

  The configuration of the power conversion device of the present embodiment is the same as that of the first embodiment. Components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant description is omitted. In the present embodiment, wide gap semiconductors are applied as the bidirectional switches 18-1 to 1-3 of the first switch group 14 and the switch 18-7 of the third switch group 16. Examples of the wide band gap semiconductor include silicon carbide, a gallium nitride-based material, and diamond. As a result, the first switch group 14 and the third switch group 16 can be switched at high speed.

  When starting the operation of the inverter 6 from the stopped state, the control unit 12 turns off the first switch group 14, turns on the third switch group 16, and instructs the inverter control unit 13 to start the operation of the inverter 6. At the same time, the switching operation of the second switch group 15 is started.

  When the load of the inverter 6 increases and the input current (current detected by the current detection unit 11) flowing through the power converter exceeds a set threshold, the control unit 12 first switches the second switch group 15. Stop operation. Next, the control unit 12 turns on the first switch group 14 from the OFF state. Finally, the control unit 12 turns off the third switch group 16 from the ON state. By performing the above three switching operations in a short time, it is possible to reduce the fluctuation of the voltage across the smoothing capacitor 5 and switch the circuit without stopping the operation of the inverter 6. For example, by performing the above three switching operations in a time of 0.2 seconds or less, it is possible to reduce the fluctuation of the voltage across the smoothing capacitor 5 and switch the circuit without stopping the operation of the inverter 6.

  Thereafter, when the load on the inverter 6 is reduced and the input current flowing through the power converter falls below a set threshold value, the operations opposite to the three switching operations are performed in the reverse order. That is, the control unit 12 first turns on the third switch group 16 from the OFF state. Next, the control unit 12 turns off the first switch group 14 from the ON state. Finally, the control unit 12 starts the switching operation of the second switch group 15. By performing these three switching operations in a time of 0.2 seconds or less, it is possible to reduce the fluctuation of the voltage across the smoothing capacitor 5 without stopping the operation of the inverter 6 by performing it in a short time. The circuit can be switched. For example, by performing the above three switching operations in a time of 0.2 seconds or less, it is possible to reduce the fluctuation of the voltage across the smoothing capacitor 5 and switch the circuit without stopping the operation of the inverter 6.

  As described above, by using wide gap semiconductors as the bidirectional switches 18-1 to 1-3 of the first switch group 14 and the switch 18-7 of the third switch group 16, the switching operation is performed at high speed. be able to.

  In addition, since the switching element formed of such a wide band gap semiconductor has high voltage resistance and high allowable current density, the switching element can be miniaturized, and these miniaturized switching elements should be used. Thus, it is possible to reduce the size of a semiconductor module incorporating these elements.

  In addition, since the wide band gap semiconductor has high heat resistance, it is possible to reduce the size of the heat dissipating fins of the heat sink and the air cooling of the water cooling portion, thereby further reducing the size of the semiconductor module.

  Furthermore, since the wide band gap semiconductor has low power loss, it is possible to increase the efficiency of the switching element, and further increase the efficiency of the semiconductor module.

  Further, the control unit 12 has a hysteresis function, and when the input current fluctuates in the vicinity of the set threshold value (for example, the difference from the set threshold value is within a predetermined range), the above-described circuit switching ( If the switching of the reactor to be short-circuited and the switching / switching of the switching operation are not performed), stable operation can be performed even if the input current flowing through the power supply converter fluctuates near the threshold value.

Embodiment 3 FIG.
Next, a third embodiment of the power converter according to the present invention will be described. The configuration of the power conversion device of the present embodiment is the same as that of the first embodiment. In the present embodiment, a set threshold value (threshold value for determining operation switching) for the input current flowing in the power converter described in the first embodiment and the second embodiment is set in the vicinity of 16A.

  Thus, the reactor connected to the three AC power supplies is compatible with both the international standards IEC61000-3-2 and IEC61000-3-12 of the harmonic current and the input current flowing through the power converter is larger than 16A. It is possible to avoid flowing current through 2-1 to 2-3, and to reduce the size of reactors 2-1 to 2-3.

Embodiment 4 FIG.
FIG. 6 is a diagram illustrating a configuration example of a power conversion device according to a fourth embodiment of the present invention. In the first embodiment, one end of the resonant capacitor 8 is connected to an intermediate point between two series-connected smoothing capacitors 5-1 and 5-2. In the present embodiment, as shown in FIG. Further, one end of the resonant capacitor 8 is connected to the negative side of two smoothing capacitors 5-1 and 5-2 connected in series. Other configurations of the power conversion device of the present embodiment are the same as those of the first embodiment. In the present embodiment, by connecting one side of the resonant capacitor 8 to the negative side of the smoothing capacitors 5-1 and 5-2, the potential on one side of the resonant capacitor 8 becomes the same as the reference potential of the inverter. A capacitor having polarity can be used as the capacitor 8.

  The operation of the present embodiment is the same as that of the first, second, or third embodiment. As described above, the switching operation similar to that of the first, second or third embodiment is applied to the configuration in which one end of the resonant capacitor 8 is connected to the negative side of the two smoothing capacitors 5-1 and 5-2 connected in series. it can.

Embodiment 5 FIG.
FIG. 7: is a figure which shows the structural example of Embodiment 5 of the outdoor unit 30 of an air conditioner provided with the power converter device concerning this invention. As shown in FIG. 7, the outdoor unit 30 includes a fan 31, a power conversion device 32, and a compressor 33 that compresses the refrigerant, and constitutes an air conditioner together with an indoor unit and the like (not shown).

  The power conversion device 32 is the power conversion device described in the first to fourth embodiments, is attached to the upper part in the outdoor unit 30, and is used for the compressor 33, the motor in the compressor 33, and the ventilation of the indoor unit. Control fan etc. In addition, in FIG. 7, since the concept of the overview is shown, wiring and the like are not shown, but the power conversion device 32 is connected to the compressor 33 and the blower fan and the like by wiring and the like. The configuration and operation of power conversion device 32 are the same as those of the power conversion device described in the first to fourth embodiments.

  Therefore, according to this Embodiment, the power converter device of Embodiment 1- Embodiment 4 can be applied to an air conditioner, and the air conditioner which satisfy | filled the specification of the harmonic current can be provided. it can. Can be satisfied.

DESCRIPTION OF SYMBOLS 1 AC power source 2-1 to 2-3, 4 Reactor 3 Rectifier diode bridge 5-1, 5-2 Smoothing capacitor 6 Inverter 7 Motor 8 Resonance capacitor 10 Voltage detection part 11 Current detection part 12 Control part 13 Inverter control part 14 First switch group 15 Second switch group 16 Third switch group 17-1 to 17-6, 20 Diode 18-1 to 18-6 Bidirectional switch 18-7 Switch 21 Transistor 22, 23 MOSFET
30 Outdoor unit 31 Fan 32 Power converter 33 Compressor

Claims (10)

A power conversion device that converts AC power supplied from an AC power source into DC power,
A rectifier circuit for rectifying the AC power into DC power;
A smoothing capacitor for smoothing the DC power;
An AC reactor connected to each phase of the AC power supply;
A DC reactor connected to the DC side of the rectifier circuit;
A resonant capacitor connected to the smoothing capacitor;
A switching unit having a switch provided between a connection point between the AC side reactor and the rectifier circuit, and the resonant capacitor;
A current detector for detecting the current of the AC power;
A voltage detector for detecting the voltage of the AC power;
An AC-side short-circuit switching unit that switches whether to short-circuit the AC-side reactor; and
A DC-side short-circuit switching unit that switches whether to short-circuit the DC-side reactor;
A control unit that controls opening and closing of the switch so as to perform a switching operation in a pattern generated by a predetermined arithmetic processing based on the voltage;
With
The control unit performs control so that the AC side reactor is not short-circuited without short-circuiting the AC-side reactor when the current is less than or equal to a predetermined threshold, and when the current exceeds a predetermined threshold, the AC A power conversion device, characterized in that control is performed such that the side reactor is short-circuited and the DC-side reactor is not short-circuited, and the switching operation is stopped . The power converter according to claim 1 , wherein the predetermined threshold is approximately 16A. Two smoothing capacitors connected in series,
The resonant capacitor, the two said connected between the smoothing capacitor, that the power conversion device according to 2 claim 1 or characterized. Two smoothing capacitors connected in series,
The resonant capacitor is connected to the negative side of the smoothing Kondenza connected to the negative side of the two of the smoothing capacitor, that the power conversion device according to claim 1 or 2, characterized in. The switch power converter according to any one of claims 1-4, characterized in being formed by a wide band gap semiconductor. The AC side short circuit switch portion and the DC-side short-circuit switch section is provided with a semiconductor switch formed by a wide band gap semiconductor, the power conversion apparatus according to any one of claims 1-5, characterized in that. The power converter according to claim 5 or 6 , wherein the wide band gap semiconductor is silicon carbide, a gallium nitride-based material, or diamond. The power conversion device according to any one of claims 1 to 7 , wherein switching between the AC side short circuit switching unit and the DC side short circuit switching unit is performed in a required time of 0.2 seconds or less. An inverse converter connected in parallel to the smoothing capacitor and converting DC power to AC power;
Further comprising
The switching of the AC side short circuit switching unit and the DC side short circuit switching unit is performed without stopping the operation of the inverse conversion unit,
Power conversion apparatus according to any one of claims 1-8, characterized in that. The power conversion device according to any one of claims 1 to 9 ,
An air conditioner comprising:

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