JP5668442B2 - Single-phase AC / DC converter and air conditioner using single-phase AC / DC converter - Google Patents

Description

  The present invention relates to a single-phase AC / DC converter that converts a single-phase AC power source into DC, and also relates to an air conditioner using the AC / DC converter.

  When driving a load such as a motor provided in an air conditioner, it is generally performed by an inverter. Here, since the input to the inverter must be a DC voltage, it is necessary to convert the voltage output from the single-phase AC power source into a DC voltage.

  Various devices have been proposed as devices for converting this single-phase AC power source into a DC power source. For example, Patent Document 1 discloses an AC / DC conversion circuit for obtaining a DC output voltage higher than a DC voltage obtained by full-wave rectification of an AC input. Half the number of rectifying element arms that constitute a full-wave rectifier circuit, with an AC reactor connected in series to the AC input side of the full-wave rectifier circuit and a capacitor connected to the DC output side. An AC / DC conversion circuit is disclosed in which a self-extinguishing semiconductor switch is connected in reverse parallel to the rectifying element.

Japanese Patent Publication No. 7-79548 (Claim 1, FIG. 1)

  In the conventional single-phase DC-AC converter configured in this way, the AC input voltage, phase, and waveform are present on the AC input side by turning on and off the reverse blocking switch element at a frequency sufficiently higher than the frequency of the AC input. A matching current flows so that the terminal voltage of the DC smoothing capacitor rises. However, in the conventional single-phase DC / AC converter that operates in this way, the input current pulsates with the ON / OFF cycle of the reverse blocking switch element, and the pulsation of the current is the cause of noise increase. There was a problem.

  The present invention has been made to solve the above problems, and reduces a pulsation of an input current and suppresses noise caused by the pulsation of the current, and the single-phase AC / DC converter. The purpose is to obtain an air conditioner using the above.

Single-phase AC-DC converter according to the present invention, the two rectifying elements are formed by connection series contact, a rectifying element rows one pole is connected to single-phase AC power source to a connection point between the rectifier elements, Two rectifier elements are connected in series, respectively, and two rectifier element arrays connected in parallel to the rectifier element array, and connected in parallel to each rectifier element constituting the two rectifier element arrays The reverse blocking switch element and one end are connected to a power line branched from the other pole of the single-phase AC power supply, and the other end is connected to a connection point between the rectifying elements in the two rectifying element arrays. Two types of PWM control signals are generated by the two reactors and two triangular waves having opposite phases to each other, and one PWM control signal generates one of the two rectifying element arrays. Control the connected reverse blocking switch element. And a pulse width modulation control means for controlling a reverse blocking switch element connected to the other rectifying element array of the two rectifying element arrays in accordance with the other PWM control signal .

The single-phase AC / DC converter according to the present invention generates two types of PWM control signals from two triangular waves having opposite phases, and one of the two rectifying element arrays is generated by one of the PWM control signals. The reverse blocking switch connected to one of the rectifying element arrays, and the reverse blocking switch connected to the other rectifying element array of the two rectifying element arrays is controlled by the other PWM control signal. Since pulse width modulation control means for controlling the element is provided, the reverse blocking switch connected to each of the two rectifying element arrays is driven by the PWM control signal generated by the triangular wave having the opposite phase, so that the current pulsation There distortion current is suppressed is reverse phase, while reducing the pulsation of the input current, suppressing noise due to the pulsation of the current single-phase AC-DC converter and the single-phase AC linear It is possible to obtain an air conditioner using the converter.

1 is a circuit configuration diagram of a single-phase AC / DC converter according to Embodiment 1. FIG. FIG. 4 is a waveform diagram showing an operation according to the first embodiment. 6 is a waveform diagram showing an example of generating a PWM control signal according to the first embodiment. FIG. It is the circuit diagram used in simulation. It is a figure which shows the simulation result in a prior art. 6 is a diagram showing a simulation result in the first embodiment. FIG. It is a figure which shows the change of the earth-ground voltage near power supply voltage zero crossing. 6 is a circuit configuration diagram of a single-phase AC / DC converter according to Embodiment 2. FIG.

Embodiment 1 FIG.
1 is a circuit configuration diagram of a single-phase AC / DC converter according to Embodiment 1. FIG.
In FIG. 1, a single-phase AC power source 1 has one pole grounded, and a power line extending from the other pole branches off and is connected to one end of a reactor 2a and a reactor 2b.

  The reverse blocking switch elements 3a to 3d are configured by bridge connection. That is, reverse blocking switch elements 3a and 3b are connected in series, and reverse blocking switch elements 3c and 3d are connected in series. The collector sides of the reverse blocking switch elements 3a and 3c are connected to the upper DC bus, and the emitter sides of the reverse blocking switch elements 3b and 3d are connected to the lower DC bus. The upper DC bus refers to the DC bus on the high voltage output side of the DC bus, and the lower DC bus refers to the low voltage output side of the DC bus. It points to the DC bus. Hereinafter, the reverse blocking switch element connected to the upper DC bus is referred to as the upper arm reverse blocking switch element, and the reverse blocking switch element connected to the lower DC bus is the lower arm reverse blocking switch. Called an element.

  Rectifying elements 4a to 4d are connected in parallel to the reverse blocking switch elements 3a to 3d, respectively. The rectifying elements 4a to 4d are, for example, diodes, and are connected so that current flows in a direction opposite to the direction of current when the reverse blocking switch elements 3a to 3d are in the on state. That is, the emitter side of each reverse blocking switch element and the anode side of the diode are connected, and the collector side of each reverse blocking switch element and the cathode side of the diode are connected. In this circuit, rectifying elements 4a and 4b are connected in series to form a rectifying element array, and rectifying elements 4c and 4d are connected in series to form a rectifying element array.

  One end of the reactor 2a is connected to the emitter side of the reverse blocking switch element 3a (that is, the collector side of the reverse blocking switch element 3b). Similarly, the emitter side (that is, the reverse blocking switch 3c) of the reverse blocking switch element 3c is connected. One end of the reactor 2b is connected to the collector side of the element 3d. Although not shown in detail, the drive signal input portions of the reverse blocking switch elements 3a to 3d (base-emitter when the reverse blocking switch element is a transistor structure, gate-emitter when the IGBT structure is used, FET In the case of the configuration, the gate-source) is connected to pulse width modulation control means 9 described later. In addition, the other end side of reactor 2a, 2b is connected to the single phase alternating current power supply 1 mentioned above.

  Further, rectifying elements 4e and 4f are connected in parallel to the output side of the reverse blocking switch elements 3a to 3d. That is, the cathode side of the rectifying element 4e is connected to the upper DC bus, the anode side of the rectifying element 4e and the cathode side of the rectifying element 4f are connected, and the anode side of the rectifying element 4f is connected to the lower DC bus. . The rectifying elements 4e and 4f constitute a rectifying element array. Furthermore, the power line on the ground side of the single-phase AC power supply 1 is connected to a connection point between the rectifying element 4e and the rectifying element 4f.

  A DC smoothing capacitor 5 is connected in parallel between the DC buses on the output side of the rectifying elements 4e and 4f, and a load 6 is connected in parallel between the DC buses on the output side of the DC smoothing capacitor 5. Note that a DC load or an AC load via an inverter is connected as the load 6, but detailed illustration is omitted. As the load 6, for example, in an air conditioner, a motor driving a compressor, a blower, or the like is connected.

  The power supply voltage phase detection means 7 is connected in parallel with the single-phase AC power supply 1 and detects the voltage phase (polarity) of the single-phase AC power supply 1. The DC voltage detecting means 8 is connected to both ends of the DC smoothing capacitor 5 and detects a voltage applied to the DC smoothing capacitor 5 (that is, an output voltage between the DC buses). The pulse width modulation control means 9 sends a control signal to the gates of the reverse blocking switch elements 3a to 3d based on the detection results of the power supply voltage phase detecting means 7 and the DC voltage detecting means 8, thereby reverse blocking. The switch elements 3a to 3d are driven.

Next, the operation will be described.
FIG. 2 is a waveform diagram showing an operation according to the first embodiment. FIG. 2 shows one cycle of the power supply voltage waveform 10. The power supply voltage waveform 10 is generally a commercial AC power supply and is a sine wave. The triangular waves 11a and 11b are waveforms generated inside the pulse width modulation control means 9, and waveforms having phases opposite to each other are generated. Further, the pulse width modulation control means 9 compares the triangular waves 11a and 11b with a separately generated target waveform so that the PWM control signals 12a to 12d are turned on when the triangular waves 11a and 11b are smaller. I have control. The PWM control signals 12a to 12d are signals that are applied to the drive signal input portions of the reverse blocking switch elements 3a to 3d, respectively, to turn on the reverse blocking switch elements 3a to 3d.

  The pulse width modulation control unit 9 controls the reverse blocking switch elements 3b and 3d on the lower arm side when the power supply voltage is positive, and the reverse blocking switch element 3a on the upper arm side when the power supply voltage is negative. PWM control signals 12a to 12d are output so as to control 3c.

  The reverse blocking switch element 3b and the reverse blocking switch element 3d on the lower arm side are controlled by PWM control signals 12b and 12d generated by triangular waves 11a and 11b having opposite phases to each other. Also, the reverse blocking switch element 3a and the reverse blocking switch element 3c on the upper arm side are controlled by PWM control signals 12a and 12c generated by triangular waves 11a and 11b having opposite phases.

  FIG. 3 is a waveform diagram illustrating a generation example of a PWM control signal according to the first embodiment. In FIG. 3, the pulse width modulation control means 9 makes a comparison between the separately generated target waveform 13 and the triangular wave 11 a and the triangular wave 11 b. As the target waveform 13, a value obtained by multiplying the power supply voltage waveform 10 by a gain for bringing the DC voltage detecting means 8 close to the target value is captured. The PWM control signal 12b is turned on in a section where the triangular wave 11a is smaller than the target waveform 13, and the PWM control signal 12d is turned on in a section where the triangular wave 11b is smaller than the target waveform 13. The PWM control signal 12b is applied to the base of the reverse blocking switch element 3b, and the PWM control signal 12d is applied to the base of the reverse blocking switch element 3d to turn on the respective reverse blocking switch elements.

  In FIG. 3, the reverse blocking switch elements 3b and 3d are taken as an example, but the same applies to the reverse blocking switch elements 3a and 3c. In FIG. 3, the PWM control signal 12b is generated by the triangular wave 11a and the PWM control signal 12d is generated by the triangular wave 11b. However, the PWM control signal only needs to be generated by triangular waves having opposite phases. The reverse of the example of 3 may be used.

  When the reverse blocking switch element is controlled as described above, the current flow path depends on whether the power supply voltage is positive or negative, the on / off state of the reverse blocking switch element, and the reverse blocking switch element being controlled. There are 8 patterns.

(A) Section in which power supply voltage is positive <Reverse blocking switch element 3b is on>
(1) Single-phase AC power supply 1 → reactor 2a → reverse blocking switch element 3b → rectifier element 4f → single-phase AC power supply 1
<Reverse blocking switch element 3b is off>
(2) Single-phase AC power source 1 → reactor 2a → rectifier element 4a → DC smoothing capacitor 5 → rectifier elements (4b, 4d, 4f) → single-phase AC power source 1
<Reverse blocking switch element 3d is on>
(3) Single-phase AC power source 1 → reactor 2b → reverse blocking switch element 3d → rectifier element 4f → single-phase AC power source 1
<Reverse blocking switch element 3d is off>
(4) Single-phase AC power supply 1 → reactor 2b → rectifier element 4c → DC smoothing capacitor 5 → rectifier elements (4b, 4d, 4f) → single-phase AC power supply 1

(B) Negative power supply voltage section <Reverse blocking switch element 3a is on>
(5) Single-phase AC power source 1 → rectifier element 4e → reverse blocking switch element 3a → reactor 2a → single-phase AC power source 1
<Reverse blocking switch element 3a is off>
(6) Single-phase AC power source 1 → rectifier element 4e → DC smoothing capacitor 5 → rectifier element (4b, 4d) → reactor (2a, 2b) → single-phase AC power source 1
<Reverse blocking switch element 3c is on>
(7) Single-phase AC power source 1 → rectifier element 4e → reverse blocking switch element 3c → reactor 2b → single-phase AC power source 1
<Reverse blocking switch element 3c is off>
(8) Single-phase AC power source 1 → rectifier element 4e → DC smoothing capacitor 5 → rectifier element (4b, 4d) → reactor (2a, 2b) → single-phase AC power source 1

  The states of (1), (3), (5), and (7) above are the states in which a reverse blocking switch element is used to create a path that short-circuits the positive and negative of the power source via the reactor, and energy is accumulated in the reactor. is there. The states (2), (4), (6), and (8) are states in which the energy accumulated in the reactor is released, and the released energy charges the DC smoothing capacitor 5.

  At this time, since the reverse blocking switch elements 3b and 3d and the reverse blocking switch elements 3a and 3c are generated by triangular waves having opposite phases, the pulsations of the currents flowing through the reactors 2a and 2b are also opposite in phase. . Since the sum of the currents flowing through the reactors 2a and 2b flows into the DC smoothing capacitor 5, the pulsation of the current flowing through the DC smoothing capacitor 5 is reduced. This also reduces the pulsation of the input current flowing through the power supply.

  The inventors have confirmed this effect by circuit simulation. The circuit simulator used is a circuit simulator PSIM manufactured by Mayway Plus, and FIG. 4 is a circuit diagram used in the simulation. This circuit diagram basically has the same circuit configuration as that of FIG. 1, but a pseudo power supply circuit 14 is inserted in the circuit in order to perform noise measurement. The pseudo power supply circuit 14 is a circuit network used when the EUT measures the terminal voltage of a conducted disturbance wave that leaks to the power supply line.

  The pseudo power supply circuit 14 inserts the reactors 15 and 16 into both the upper and lower DC buses immediately after the output from the single-phase AC power source 1, and the upper DC bus between the DC buses on the output side of the reactors 15 and 16. The capacitor 17, resistor 18, resistor 19, and capacitor 20 are connected in series in this order. The resistor 18 and the resistor 19 are grounded.

  In the simulation, the constants of the pseudo power supply circuit are 50 μH for reactors 15 and 16, 50 Ω for resistors 18 and 19, and 0.1 μF for capacitors 17 and 20.

  FIG. 5 is a diagram showing a simulation result in the prior art. The simulation in the prior art is similar to FIG. 1 of Patent Document 1, and is performed by a circuit in which the reactor 2b, the reverse blocking switch elements 3c and 3d, and the rectifying elements 4c and 4d in FIG. 4 are removed. FIG. 6 is a diagram showing a simulation result in the first embodiment. In both figures, the waveforms of the simulation results are, in order from the top, the power supply voltage, the input current, the voltage to ground (fluctuation of the potential of the DC bus voltage to ground), and the noise terminal voltage (voltage across the resistor 18). . The ground voltage is a voltage between the ground (ground) and the negative side of the DC smoothing capacitor 5, and a potential difference is generated between the ground and the ground 21 via the ground capacitance 21. In addition, simulation was performed with a power supply voltage of 200 V, a carrier frequency of 25 kHz, a bus voltage command of 380 V, the reactors 2 a and 2 b as 550 μH, and the DC smoothing capacitor 5 as 1500 μF as circuit constants.

  When comparing the noise terminal voltage in FIGS. 5 and 6, it can be seen that the peak in FIG. 5 that is 20 mV or more is reduced to a level close to zero in FIG.

  In FIGS. 5 and 6, it can be seen that the ground voltage takes two values as the phase of the power supply changes. When the power supply voltage is in the vicinity of 0 V, it is difficult to determine the power supply voltage phase, and a phenomenon in which the change in the ground voltage is repeated in a short time may occur. FIG. 7 is a diagram showing a change in the voltage between the grounds near the power supply voltage zero cross. In FIG. 7, when the power supply voltage waveform 10 changes from positive to negative, the case where the upper arm and the lower arm of the reverse blocking switch element for performing ON / OFF control erroneously in the determination of the power supply voltage phase is reversed is shown. The voltage between the positive voltage and the negative voltage is repeatedly changed in a short time, and the ground voltage is repeatedly changed between 0V and 380V.

  The change in the voltage to ground causes not only an increase in noise but also an increase in leakage current. For this reason, when the power supply voltage value is within a predetermined range of around 0 V, the pulse width modulation control means 9 may provide a period during which the reverse blocking switch elements 3a to 3d are not switched.

  According to the present invention, since the reverse blocking switch elements 3b and 3d and the reverse blocking switch elements 3a and 3c are driven by triangular waves with opposite phases, the current pulsation of the current flowing through the rectifier circuit is in reverse phase. The distortion current is suppressed, and there is an effect that noise generated due to current pulsation is reduced. For this reason, while reducing the pulsation of input current, the single phase alternating current direct current converter which suppresses the noise resulting from the pulsation of an electric current can be obtained.

  Further, the rectifying element and the reverse blocking switch element may be composed of a wide band gap semiconductor such as SiC. By using a wide bandgap semiconductor such as SiC, high-speed operation is possible, and the reactors 2a and 2b can be reduced in size. In addition to cost reduction, followability with respect to load fluctuations is improved and controllability is improved.

  The wide band gap semiconductor is a general term for semiconductor elements having a larger band gap compared to silicon (Si) elements. In addition to silicon carbide (SiC) elements, for example, gallium nitride (GaN), diamond elements, etc. Can be given.

  Note that when a wide band gap semiconductor such as SiC is used, the carrier frequency of the triangular wave that generates the PWM signal is determined by EMC emission regulations such as noise terminal voltage (for example, EN61000-6-3: 2007, J55014-1 (H20), From the viewpoint of VCCI (2008. 4) class A), it is preferable to set the frequency to be a frequency that is not subject to the carrier frequency and its sideband. For example, the carrier frequency of the triangular wave that generates the PWM signal is less than 1/2 of 150 kHz so that the sideband wave that is an integral multiple of the carrier frequency is less than 150 kHz with respect to 150 kHz, which is the lower limit frequency of noise terminal voltage regulation. About 73 kHz, about 49 kHz which is less than 1/3 of 150 kHz, and about 36 kHz which is less than 1/4 of 150 kHz.

  Further, in the case of a DC power supply, a specific element is always driven, and there is a disadvantage that the burden on the element becomes large. In the case of an AC power supply, as described in the first embodiment, a reverse blocking switch through which a current passes is provided. When the power supply voltage is positive, the elements are switched between the reverse blocking switch elements 3b and 3d, and when the power supply voltage is negative, the reverse blocking switch elements 3a and 3c are switched every 180 degrees in the energizing section, so that the average heat generation can be suppressed. Out. Further, by using SiC that can be operated at high temperature, it is possible to reduce the number of components such as external heat radiation fins that may increase complexity and cost.

  In the above description, the PWM control has been described with a simple method. However, if tracking control based on feedback of the input current is used, distortion of the input power supply voltage can be dealt with, and high-precision control that makes the input current closer to a sine wave. Needless to say, it is possible to select cost-effectiveness depending on the load capacity, the regulation value, and the influence on the surrounding environment.

  Further, when generating a PWM control signal, the frequency of the triangular wave to be compared with the reference signal may be a fixed frequency. However, by changing the frequency such as having frequency jitter, the radiation noise from the main circuit concentrates on a specific frequency. Without being dispersed, and the peak of radiation noise can be reduced.

Embodiment 2. FIG.
FIG. 8 is a circuit configuration diagram of the single-phase AC / DC converter according to the second embodiment. In the circuit configuration diagram of FIG. 1, a motor 23 driven by an inverter 22 is connected as a load 6. The motor 23 is used for a compressor (not shown), for example.

  Usually, since the compressor is attached to the metal casing of the air conditioner outdoor unit, the compressor casing is connected to the ground. In addition, since the motor coil constituting the compressor is present in the refrigerant or oil circulating for cooling, a large stray capacitance is present between the motor coil and the casing (ground). Cm is formed. Therefore, when the potential fluctuation between the DC portion of the inverter and the ground is large, a high-frequency current corresponding to the potential fluctuation flows to the ground via the stray capacitance Cm.

  However, according to the air conditioner using the single-phase AC / DC converter according to the present embodiment, as described in the first embodiment, the ground potential fluctuation in the AC / DC converter unit is suppressed and the leakage current is reduced. Since the current flowing to the ground via the stray capacitance Cm can be suppressed to the same extent as in the case of a simple rectifier circuit configuration that does not have a switch element in the AC / DC change device unit, the entire air conditioner As a result, the leakage current can be suppressed.

  The present invention is widely applicable to devices that convert single-phase alternating current into direct current. In particular, the present invention can be widely applied to electrical equipment having an inverter load such as an air conditioner, a refrigerator, a refrigerator, and a heat pump water heater.

1 Single-phase AC power supply 2a, 2b Reactor 3a, 3b, 3c, 3d Reverse blocking switch element 4a, 4b, 4c, 4d, 4e, 4f Rectifier element 5 DC smoothing capacitor 6 Load 7 Power supply voltage phase detection means 8 DC voltage detection Means 9 Pulse width modulation control means 10 Power supply voltage waveforms 11a, 11b Triangular waves 12a, 12b, 12c, 12d PWM control signal 13 Target waveform 14 Pseudo power supply circuit 15, 16 Reactor 17 Capacitor 18, 19 Resistor 20 Capacitor 21 Capacitance to ground 22 Inverter 23 Motor

Claims (6)

Two rectifying element is formed by connection series contact, a rectifying element rows one pole is connected to single-phase AC power source to a connection point between the rectifier elements,
Two rectifier elements connected in series with each other, and two rectifier elements connected in parallel with the rectifier element;
Reverse blocking switch elements connected in parallel to each of the rectifying elements constituting the two rectifying element arrays;
One end is connected to a power supply line branched from the other pole of the single-phase AC power supply, and the other end is connected to a connection point between the rectifying elements of each of the two rectifying element arrays. Reactor,
Two types of PWM control signals are generated by two triangular waves having opposite phases, and the reverse connected to one of the two rectifying element arrays by the one PWM control signal. Pulse width modulation control means for controlling the blocking switch element connected to the other rectifying element row of the two rectifying element rows by controlling the blocking switch element, and the other PWM control signal ;
Single-phase AC-DC converter of Ru with a. The pulse width modulation control means includes
2. The single-phase AC / DC converter according to claim 1, wherein the reverse blocking switch element is not controlled when the voltage value of the single-phase AC power source is within a predetermined range of about 0V. The pulse width modulation control means includes
While the single-phase AC power supply is positive potential, while controlling the reverse blocking switch element on the lower arm side,
3. The single-phase AC / DC converter according to claim 1, wherein the reverse blocking switch element on the upper arm side is controlled while the single-phase AC power supply is at a negative potential. 4. The single-phase AC / DC converter according to claim 1, wherein at least one of the rectifying element and the reverse blocking switch element is formed of a wide band gap semiconductor. 5. The single-phase AC / DC converter according to claim 4, wherein the wide band gap semiconductor is a SiC element. An air conditioner equipped with a compressor driven using the single-phase AC / DC converter according to any one of claims 1 to 5.

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