WO2021260768A1

WO2021260768A1 - Power conversion device

Info

Publication number: WO2021260768A1
Application number: PCT/JP2020/024377
Authority: WO
Inventors: 憲嗣岩崎; 康彦和田; 和憲坂廼邉; 護神蔵
Original assignee: 三菱電機株式会社
Priority date: 2020-06-22
Filing date: 2020-06-22
Publication date: 2021-12-30
Also published as: JPWO2021260768A1; JP7309070B2; DE112020007351T5

Abstract

This power conversion device comprises: a rectifier unit for rectifying voltage supplied from a power supply; an inverter unit having power conversion elements, converting the voltage rectified by the rectifier unit by switching of the power conversion elements, and outputting the converted voltage to a load; a DC link unit connected between the rectifier unit and the inverter unit and provided with a capacitor with a capacity having an extent of not smoothing the voltage rectified by the rectifier unit; a control unit for controlling the switching of the power conversion elements of the inverter unit on the basis of a switching carrier frequency; and a carrier variable unit for outputting a command to the control unit, said command allowing the switching carrier frequency to change on the basis of a preset change pattern.

Description

Power converter

This disclosure relates to a power conversion device that supplies electric power received from an AC power supply to a load such as a permanent magnet type synchronous motor.

In general, an inverter is a device that can generate variable voltage and variable frequency alternating current by turning on and off switching elements from direct current, and can operate an electric motor at variable speed.

In addition, the process of receiving AC power from an AC power source, converting it to DC power, creating AC power from DC power, and operating the motor at variable speed may be collectively referred to as an "inverter". In this case, the inverter is composed of a rectifying unit that performs rectification, an inverter unit that performs DC-AC conversion, and a DC link unit that connects the rectifying unit and the inverter unit.

In a general inverter, rectification is performed in a rectifying section composed of a diode or a transistor to create a pulsating DC voltage. Further, by smoothing the pulsating DC voltage with a smoothing capacitor provided in the DC link portion, a pulsating DC voltage is created. Using this DC voltage, an AC voltage is created by turning on and off the semiconductor switch in the inverter section. The AC voltage output from the inverter is supplied to a load such as a motor.

In the DC link section, an electrolytic capacitor is used as a smoothing capacitor. However, the electrolytic capacitor has the disadvantages that it has a high risk of failure among the components constituting the inverter and has a short life such as dry-up due to aging deterioration. Further, in particular, the electrolytic capacitor used as a smoothing capacitor in the DC link portion needs to have a high withstand voltage and a large capacity, and therefore has a demerit that the size is large and the cost is high.

On the other hand, as a kind of inverter, there is a method that does not use an electrolytic capacitor in the DC link part. In the inverter of this type, by providing a capacitor with a small capacity such as a film capacitor in the DC link section, the pulsation output from the rectifying section is not smoothed and is output to the inverter section. This type of inverter is called an electrolytic capacitorless inverter.

In this disclosure, an inverter in which a large-capacity electrolytic capacitor is mounted on a conventional DC link unit is referred to as a "conventional inverter". Further, an inverter equipped with a small capacity capacitor such as a film capacitor without providing a large capacity electrolytic capacitor in the DC link portion is referred to as an "electrolytic capacitorless inverter".

In a "conventional inverter", the rectifying unit is often composed of four or six diodes. While the diode of the rectifying section is on, the charging current flows through the large-capacity electrolytic capacitor mounted on the DC link section, so that the power supply current rises sharply. If the rise of the power supply current is steep, it may cause a failure due to overcurrent, or the power factor and the power supply harmonics may deteriorate. Therefore, a reactor is inserted between the rectifying unit and the electrolytic capacitor for the purpose of slowing the change in the power supply current. The position of the reactor is not limited to this, and can be attached to both the AC (Alternating Current) side and the DC (Direct Current) side depending on the purpose of use such as the power supply environment, the inverter method, and the electric power. The reactor inserted on the AC side is called ACL (Alternating Current Reactor), and the reactor inserted on the DC side is called DCL (Direct Current Reactor).

Regardless of whether the reactor is ACL or DCL, it is necessary that the reactor has a high inductance in order to moderate the current change. Therefore, the reactor tends to be a particularly large and high-cost component among the components constituting the inverter.

On the other hand, in the "electrolytic capacitorless inverter", the capacitor capacity of the DC link is small, so the charging current is small and the rise of the current after rectification is relatively small. Therefore, the risk of capacitor failure can be reduced, and the inductance of the reactor can be made relatively small. Therefore, the reactor constituting the DCL or ACL can be reduced in inductance and size, and the cost can be suppressed.

For the above reasons, the "electrolytic capacitorless inverter" has merits such as reduction of failure risk, miniaturization, and cost reduction.

However, on the other hand, in the "electrolytic capacitorless inverter", the noise flowing out to the power supply system may increase due to its configuration.

In the "conventional inverter", a reactor with a large inductance is used. When the inductance of the reactor is large, it has a high impedance for high frequency current. Therefore, noise in the high frequency band such as noise caused by switching generated in the inverter section is unlikely to flow out to the power supply side. Further, in the "conventional inverter", since a large-capacity capacitor is mounted on the DC link portion, noise and voltage ripple generated in the inverter portion are easily absorbed by the DC link portion.

Here, the noise and voltage ripple generated in the inverter section will be briefly explained.

First, the voltage ripple will be explained. The inverter unit performs DC-AC conversion, and when the DC-AC conversion operation is performed, a switching operation for turning on / off the switching element provided in the inverter unit is performed. Due to these switching operations, voltage ripple occurs. Since the voltage ripple basically depends on the carrier frequency, it often becomes noise on the order of kHz.

Next, noise will be explained. Noise is divided into radiation noise and conduction noise. In the case of conduction noise, the emission limit value in the band of 150 kHz to 30 MHz is defined by the standard (EN61000-6-3, etc.).

Further, the noise current I common of the common mode noise, which occupies a large proportion of the conduction noise, is expressed by the following equation (1).

Icommon = CDv / dt ... (1)

Here, C: stray capacitance, v: voltage.

As can be seen from the equation (1), the magnitude of the noise current I common of the common mode noise is determined by the stray capacitance C between the inverter circuit board and the motor and the ground, and the change in the voltage v applied thereto.

As a method of suppressing the outflow of noise, there is a method of providing a snubber with a film capacitor or a ceramic capacitor in the DC link portion, or a method of providing a noise filter composed of a reactor and a capacitor on the power supply side. The noise filter can suppress the outflow of noise in a specific band to the power supply side by combining a reactor and a capacitor.

For example, Patent Document 1 has a configuration in which, in a power conversion device, the capacity of a film capacitor provided in a DC link portion is selected to a value at which a carrier component can be removed to suppress the influence of switching of the inverter portion on a power supply. It has been disclosed.

Japanese Unexamined Patent Publication No. 2009-219267

However, in the "electrolytic capacitorless inverter", when switching at a carrier frequency higher than that of normal motor control, the effect of conventional measures may be reduced. For that reason, in the "electrolytic capacitorless inverter", restraint energization for heating the refrigerant in the compressor for preventing the occurrence of the so-called refrigerant stagnation phenomenon is not performed.

For example, in an air conditioner, when restrained energization is performed at a high frequency in order to heat the refrigerant in the compressor by utilizing the iron loss generated in the motor mounted on the compressor, the carrier frequency used in normal motor control is higher than that of the carrier frequency. There is a possibility of switching the switching element of the inverter section at a high carrier frequency.

At this time, assuming that the carrier frequency used is the carrier frequency of normal motor control, if the capacitor of the DC link section and the noise filter of the power supply section are designed, the carrier ripple of a higher frequency is performed. , And its harmonic components cannot be sufficiently removed.

If high frequency noise leaks to the power supply side, it causes malfunction or failure of other devices connected to the power supply side.

In addition, in order to suppress the influence of noise, it is necessary to take measures such as providing noise filters corresponding to multiple frequency bands, and there are problems such as cost increase.

This disclosure is made to solve such a problem, and while maintaining the advantages of the electrolytic capacitorless inverter such as miniaturization, cost reduction, and long life, it does not significantly increase the cost. The purpose is to obtain a power conversion device capable of reducing carrier ripple and noise.

The power conversion device according to the present disclosure has a rectifying unit for rectifying a voltage supplied from a power source and a power conversion element, and the voltage rectified by the rectifying unit is converted by switching of the power conversion element to load. A DC link unit connected between the rectifying unit and the inverter unit and provided with a capacitor having a capacity that does not smooth the voltage rectified by the rectifying unit, and an inverter unit. A control unit that controls the switching of the power conversion element based on the switching carrier frequency and a carrier variable unit that outputs a command to change the switching carrier frequency based on a preset change pattern to the control unit are provided. It is a thing.

According to the power conversion device according to the present disclosure, carrier ripple and noise can be achieved without significantly increasing the cost while maintaining the advantages of the electrolytic capacitorless inverter such as miniaturization, cost reduction, and long life. It can be reduced.

It is a circuit diagram which shows the structure of the power conversion apparatus 8 which concerns on Embodiment 1. FIG. It is an image diagram explaining the difference of the noise component superimposed on the power supply current in the carrier variable ONOFF. It is an image diagram explaining the difference of the noise component superimposed on the power supply current in the carrier variable ONOFF. It is a figure which shows an example of the actual measurement result of the output voltage from the inverter part 5. It is a figure which shows an example of the actual measurement result of the output voltage from the inverter part 5. It is a circuit diagram which shows the structure of the power conversion apparatus 8 which concerns on Embodiment 2. FIG. It is a circuit diagram which shows the modification of the power conversion apparatus 8 which concerns on Embodiment 2. FIG. An example of the change pattern of the carrier frequency based on the Vdc synchronization command of the Vdc synchronization unit 7d provided in the control device 7 of the power conversion device 8 according to the second embodiment is shown. An example of the change pattern of the carrier frequency based on the Vdc synchronization command of the Vdc synchronization unit 7d provided in the control device 7 of the power conversion device 8 according to the second embodiment is shown. An example of the change pattern of the carrier frequency based on the Vdc synchronization command of the Vdc synchronization unit 7d provided in the control device 7 of the power conversion device 8 according to the second embodiment is shown. It is a block diagram which shows an example of the structure of the refrigerating cycle device 50 to which the power conversion device 8 which concerns on Embodiment 1 is applied.

Hereinafter, embodiments of the power conversion device according to the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and can be variously modified without departing from the gist of the present disclosure. In addition, the present disclosure includes all combinations of configurations that can be combined among the configurations shown in the following embodiments and modifications thereof. Further, in each figure, those having the same reference numerals are the same or equivalent thereof, which are common to the whole text of the specification. In each drawing, the relative dimensional relationship or shape of each component may differ from the actual one.

Embodiment 1.
FIG. 1 is a circuit diagram showing the configuration of the power conversion device 8 according to the first embodiment. As shown in FIG. 1, the power conversion device 8 includes a rectifying unit 2, a reactor 3, a DC link unit 4, an inverter unit 5, a control device 7, and a DC voltage detecting unit 9. The power conversion device 8 is applied to, for example, a refrigeration cycle device 50 (see FIG. 11) such as an air conditioner together with the motor 6.

FIG. 11 is a configuration diagram showing an example of the configuration of the refrigeration cycle device 50 to which the power conversion device 8 according to the first embodiment is applied. As shown in FIG. 11, the refrigeration cycle device 50 includes an outdoor unit 60 and an indoor unit 70. The outdoor unit 60 and the indoor unit 70 are connected to each other via a refrigerant pipe 52. The outdoor unit 60 is provided with a compressor 61, a four-way valve 62, a heat exchanger 63, a blower fan 64, and an expansion valve 65. On the other hand, the indoor unit 70 is provided with a heat exchanger 71 and a blower fan 72. The compressor 61 sucks in the refrigerant flowing in the refrigerant pipe 52. The compressor 61 compresses the sucked refrigerant and discharges it to the refrigerant pipe 52. The compressor 61 is, for example, an inverter compressor. The refrigerant discharged from the compressor 61 flows into the heat exchanger 63 of the outdoor unit 60 or the heat exchanger 71 of the indoor unit 70. The

heat exchangers

63 and 71 exchange heat between the refrigerant flowing inside and the air. The

heat exchangers

63 and 71 are, for example, fin-and-tube heat exchangers. Further, the blower fan 64 has a fan motor 64a and a blade portion 64b. Similarly, the blower fan 72 has a fan motor 72a and a wing portion 72b. The

blower fans

64 and 72 blow air to the

heat exchangers

63 and 71, respectively. The four-way valve 62 is configured to switch the state between the case of the cooling operation of cooling the indoor unit 70 side and the case of the heating operation of heating the indoor unit 70 side. In the case of cooling operation, the four-way valve 62 is in a state shown by a solid line, and the refrigerant discharged from the compressor 61 flows into the heat exchanger 63 of the outdoor unit 60. At this time, the heat exchanger 63 of the outdoor unit 60 acts as a condenser, and the heat exchanger 71 of the indoor unit 70 acts as an evaporator. On the other hand, in the case of the heating operation, the four-way valve 62 is in the state shown by the broken line, and the refrigerant discharged from the compressor 61 flows into the heat exchanger 71. At this time, the heat exchanger 63 of the outdoor unit 60 acts as an evaporator, and the heat exchanger 71 of the indoor unit 70 acts as a condenser. The expansion valve 65 is a pressure reducing device for reducing the pressure of the refrigerant, and is composed of, for example, an electronic expansion valve. The expansion valve 65 is provided between the heat exchanger 63 of the outdoor unit 60 and the heat exchanger 71 of the indoor unit 70. The compressor 61, the four-way valve 62, the heat exchanger 63, the expansion valve 65, and the heat exchanger 71 are connected by a refrigerant pipe 52 to form a refrigerant circuit.

Return to the explanation in Fig. 1. As shown in FIG. 1, the power conversion device 8 is connected to the AC power supply 1. The AC power supply 1 is, for example, a three-phase AC power supply. Not limited to this case, the AC power supply 1 may be composed of a power supply other than the three-phase power supply such as a single-phase power supply.

The rectifying unit 2 rectifies the AC voltage input from the AC power supply 1 and converts it into a DC voltage. The DC voltage is applied to the DC link unit 4 through the reactor 3. The rectifying unit 2 is composed of, for example, a full bridge circuit including six rectifying diodes. The six rectifying diodes are connected in series by two to form a total of three series circuits. The three series circuits are connected in parallel. The three series circuits are provided corresponding to the U phase, V phase, and W phase of the AC power supply 1, respectively. The connection points of the two rectifying diodes constituting each series circuit are connected to the U phase, V phase and W phase of the AC power supply 1, respectively. The rectifying unit 2 may use a switching element such as a transistor instead of the rectifying diode.

The reactor 3 is provided for the purpose of suppressing a steep rise in the power supply current from the AC power supply 1 and slowing down the current change. In the example of FIG. 1, the reactor 3 is provided in the rear stage of the rectifying unit 2, but may be provided in the front stage of the rectifying unit 2.

The DC link unit 4 has a small-capacity capacitor 4a. The small capacity capacitor 4a is, for example, a film capacitor or a ceramic capacitor. The capacity of the small-capacity capacitor 4a is smaller than the capacity of the smoothing electrolytic capacitor provided in the "conventional inverter". The capacity of the small-capacity capacitor 4a is such that the waveform of the DC voltage rectified by the rectifying unit 2 is not smoothed. Specifically, the capacity of the electrolytic capacitor for smoothing provided in the "conventional inverter" is such that the low-order harmonic component that pulsates greatly at a frequency twice or six times the voltage frequency of the commercial power supply is removed. Set. On the other hand, the capacitance of the small-capacity capacitor 4a does not remove the low-order harmonic component that pulsates greatly at a frequency twice or six times the voltage frequency of the commercial power supply, but removes the carrier frequency component of the inverter section 5. Is set to. Since the small-capacity capacitor 4a of the DC link portion 4 has a small capacitor capacity, the charging current is small and the rise of the current after rectification is relatively small. Therefore, the inductance of the reactor 3 may be relatively small. Therefore, the reactor 3 can be reduced in inductance and size, and the cost can be suppressed. As a result, the power conversion device 8 according to the first embodiment has merits such as reduction of failure risk, miniaturization, and cost reduction of the "electrolytic capacitorless inverter". The DC link unit 4 outputs the DC voltage input from the rectifying unit 2 to the inverter unit 5 without smoothing it.

Therefore, the voltage waveform of the voltage Vdc output from the DC link unit 4 has the voltage waveform 11 shown in the rectangular frame 10 of FIG. If the voltage Vdc is smoothed, it becomes a linear line with a constant value, but since it is not smoothed, the voltage waveform 11 of the voltage Vdc contains a pulsating component 11a that fluctuates up and down as shown in FIG. ing.

The inverter unit 5 converts the direct current input from the DC link unit 4 into alternating current by the operation of the power conversion element, and outputs it to the motor 6 which is a load. The inverter unit 5 has, for example, three upper arm switching elements 5a and three lower arm switching elements 5b as power conversion elements. The inverter unit 5 is composed of, for example, a full bridge circuit. One upper arm switching element 5a and one lower arm switching element 5b are connected in series, and the connection point thereof is a midpoint. A series circuit composed of one upper arm switching element 5a and one lower arm switching element 5b is called an arm. The inverter unit 5 has three arms. The three arms are connected in parallel. The three arms are provided corresponding to the U-phase, V-phase, and W-phase of the motor 6, respectively. The midpoint of each arm is connected to the U phase, V phase and W phase of the motor 6, respectively. Further, a reflux diode 5c is connected to each of the upper arm switching elements 5a in antiparallel. Similarly, a freewheeling diode 5c is connected to each of the lower arm switching elements 5b in antiparallel. The

switching elements

5a and 5b used in the inverter unit 5 are, for example, an IGBT, a MOSFET, a self-extinguishing thyristor, a bipolar transistor, and the like. The

switching elements

5a and 5b of the inverter unit 5 perform on / off operations according to the PWM drive command signal described later from the control device 7. By the on / off operation, the direct current input from the DC link unit 4 is converted into alternating current. The power obtained by switching the

switching elements

5a and 5b may be high frequency power. Although the case where the load is the motor 6 has been described here, the load may be any other device as long as it is a device driven by the electric power from the power conversion device 8. Further, the inverter unit 5 may be mounted on an inverter device that drives a load.

Although the example in which the inverter unit 5 has the

switching elements

5a and 5b as the power conversion element has been described here, the present invention is not limited to this case, and other power conversion elements may be used.

The motor 6 is, for example, a three-phase AC motor. The motor 6 is not limited to this, and may be a motor other than the three-phase, for example, a single-phase AC motor. Further, the motor 6 may be an AC motor or a DC motor. The motor 6 is mounted on the compressor 61 of the refrigeration cycle device 50, for example. When the motor 6 is a motor mounted on the compressor 61 and the compressor 61 is an inverter compressor, the power conversion device 8 may be mounted on the inverter device for driving the compressor 61. Further, the motor 6 may be used as the

fan motors

64a and 72a of the

blower fans

64 and 72. In that case, the power conversion device 8 may be mounted on the inverter device that drives the

blower fans

64 and 72. In FIG. 1, the motor 6 is given as an example as the load, but the load is not limited to this, and the load may be another device.

The control device 7 has a control unit 7a, a carrier variable unit 7b, and a storage unit 7c.

The control unit 7a receives a voltage signal from the DC voltage detection unit 9. The DC voltage detection unit 9 will be described later. The control unit 7a performs a PWM control operation based on the voltage signal, a command value input from the outside, and a switching carrier frequency, and outputs a PWM drive command signal to the inverter unit 5. PWM is an abbreviation for Pulse Width Modulation. The PWM drive command signal is a control signal for switching the on / off states of the U-phase, V-phase, and W-

phase switching elements

5a and 5b of the inverter unit 5. Further, the command value input from the outside is a command value that specifies a waveform (hereinafter, referred to as a modulated wave) to be output by the inverter unit 5.

The carrier variable unit 7b outputs a command for changing the switching carrier frequencies of the

switching elements

5a and 5b of the inverter unit 5 to the control unit 7a based on a preset change pattern. Hereinafter, the switching carrier frequencies of the

switching elements

5a and 5b are simply referred to as carrier frequencies. The carrier frequency changes within a preset carrier frequency variable range. The carrier frequency variable range is stored in advance in the storage unit 7c of the control device 7. The format of the command output from the carrier variable unit 7b to the control unit 7a may be a control signal for changing the carrier frequency, or may be the carrier frequency change pattern itself.

The lower graphs of FIGS. 8 to 10 show an example of a change pattern in which the carrier frequency changes based on the command of the carrier variable portion 7b in the first embodiment. As shown in FIG. 8, the carrier variable portion 7b may output a command for linearly changing the carrier frequency 41 in a triangular wave shape, or as shown in FIG. 9, the carrier frequency 41 is a curve such as a sine wave shape. A command to change the frequency may be output. Further, as shown in FIG. 10, the carrier variable unit 7b may output a command for changing the carrier frequency 41 in a stepwise manner. The change pattern of the carrier frequency 41 is not limited to the examples of FIGS. 8 to 10, and may be another pattern as long as it is a pattern that changes in the form of a repeating waveform. As described above, the change pattern of the carrier frequency 41 is not determined to be one, but is selected in advance according to the purpose of use, the environment of use, and the like, and the selected change pattern is preset in the carrier variable portion 7b. For example, when it is desired to reduce the noise generated by the power conversion device 8, the carrier variable unit 7b sets the carrier frequency 41 of the

switching elements

5a and 5b of the inverter unit 5 in accordance with the carrier frequency variable range 40. A pattern for changing the average value of the above so as to match the carrier frequency when the carrier is not changed is output to the control unit 7a. Alternatively, if it is desired to reduce the high frequency component of the sound emitted by the power converter 8, the carrier variable unit 7b can hear a part or all of the carrier frequency change pattern according to the carrier frequency variable range 40. A pattern for changing the carrier frequency 41 of the

switching elements

5a and 5b of the inverter unit 5 so as to pass outside the frequency range is output to the control unit 7a. In this case, since the audible frequency band is generally set to 20 Hz to 20 kHz, the carrier frequency is set to be higher than the audible frequency band. As an example of the case where a part or all of the change pattern of the carrier frequency passes outside the range of the audible frequency, for example, the frequency that is efficient for heating the refrigerant (for example, 16 kHz) and the frequency outside the audible frequency range are exchanged. There is a change pattern to be made. Alternatively, as another example, there is a change pattern in which the average value of the carrier frequencies is set to a frequency (for example, 16 kHz) that is efficient with respect to the heating of the refrigerant, and a part of the carrier frequency is out of the audible frequency range. .. As described above, the carrier variable unit 7b outputs a command for changing the carrier frequency to the control unit 7a based on the change pattern selected according to the problem to be solved such as the amount of noise or sound. The control unit 7a performs a PWM control operation using a carrier frequency that changes according to the change pattern.

The DC voltage detection unit 9 detects the voltage Vdc of the DC link unit 4. Specifically, the DC voltage detection unit 9 detects the voltage across the small-capacity capacitor 4a of the DC link unit 4 as the voltage Vdc. The voltage Vdc has the voltage waveform 11 shown in the rectangular frame 10 of FIG. Since the voltage Vdc is not smoothed, the voltage waveform 11 of the voltage Vdc contains a pulsating component 11a that fluctuates up and down as shown in the rectangular frame 10 of FIG. The DC voltage detection unit 9 transmits a voltage signal indicating the detected voltage Vdc of the DC link unit 4 to the control unit 7a of the control device 7. As described above, the control unit 7a performs PWM control based on the voltage signal. The DC voltage detection unit 9 is provided between the control device 7 and the DC link unit 4 in the example of FIG. 1, but the DC voltage detection unit 9 is not limited to this case and is one of the components of the control device 7. It may be one of the constituent elements of the DC link part 4.

Here, the hardware configuration of the control device 7 will be described. Each function of the control unit 7a and the carrier variable unit 7b of the control device 7 is realized by a processing circuit. The processing circuit is composed of dedicated hardware or a processor. The dedicated hardware is, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The processor executes a program stored in the storage unit 7c. The storage unit 7c is composed of a memory. The memory is a non-volatile or volatile semiconductor memory such as RAM (RandomAccessMemory), ROM (ReadOnlyMemory), flash memory, EPROM (ErasableProgrammableROM), or a disk such as a magnetic disk, flexible disk, or optical disk. be.

2 and 3 are image diagrams illustrating the difference in noise components superimposed on the power supply current in carrier variable ON / OFF. FIG. 2 shows a noise component when the carrier is variable OFF. That is, FIG. 2 shows a noise component when the carrier variable portion 7b does not perform carrier variable. On the other hand, FIG. 3 shows a noise component in the case of carrier variable ON. That is, FIG. 3 shows a noise component when the carrier is variable by the carrier variable portion 7b. In FIGS. 2 and 3, the horizontal axis represents frequency and the vertical axis represents amplitude.

4 and 5 are diagrams showing an example of the actual measurement result of the output voltage from the inverter unit 5. FIG. 4 shows the actual measurement result in the case of carrier variable OFF. That is, FIG. 4 shows the actual measurement results when the carrier variable portion 7b does not perform carrier variable. On the other hand, FIG. 5 shows the actual measurement result in the case of carrier variable ON. That is, FIG. 5 shows the actual measurement result when the carrier is variable by the carrier variable portion 7b. In FIGS. 4 and 5, the horizontal axis indicates the frequency and the vertical axis indicates the magnitude of conduction noise.

First, the case of carrier variable OFF will be described with reference to FIGS. 2 and 4. FIG. 2 shows harmonic components from the first order to the nth order. In the case of carrier variable OFF, the _{carrier ripple 20 having the carrier} frequency component f carrier shown in FIG. 2 is superimposed as a noise component on the output of the inverter unit 5. _{Further, the second harmonic 2f carrier} , which is the harmonic component of the carrier ripple 20, to the nth harmonic n * f _carrier are superimposed. In this case, the noise component may fall within the conduction noise regulation range. FIG. 4 shows a case where constrained energization is performed at a carrier frequency of 16 kHz, as shown by an arrow. The restraint energization will be described later. As shown by the broken line frame 31 in FIG. 4, a component having an integral multiple of the frequency of 16 kHz appears as a peak of the noise component. In FIG. 4, it is shown that the harmonic component 33 of the 10th or higher order of 16 kHz is within the conduction noise regulation range in the region higher than 150 kHz. In FIG. 4, the dotted line 32 shows the conduction noise envelope when the carrier is variable OFF.

Next, the case of carrier variable ON will be described with reference to FIGS. 3 and 5. FIG. 3 shows harmonic components from the first order to the nth order. In FIG. 3, the carrier variable unit 7b changes the carrier frequency within a preset carrier frequency variable range. Even in the case of carrier variable ON, the _{carrier ripple 21 having the carrier} frequency component (f carrier) shown in FIG. 3 and its harmonic component are superimposed on the output from the inverter unit 5 as the noise component 22. However, as can be seen by comparing FIGS. 3 and 2, in the case of FIG. 3, the width of the mountain hem portion of the noise component 22 is widened, but the apex of the noise component 22 is lowered, and the amplitude of the noise component 22 as a whole is reduced. Level is down. Here, the width of the mountain skirt portion of the noise component 22 is the difference between the minimum frequency fcmin and the maximum frequency fcmax of each noise component 22 as shown in FIG. Further, FIG. 5 is an actual measurement result in the case of carrier variable ON. In the actual measurement results of FIG. 5, it can be seen that the harmonic component 33 of the carrier ripple appearing in FIG. 4 is no longer visible, and the peak level of the noise component 22 is lowered. In FIG. 5, the dotted line 32 shows the conduction noise envelope when the carrier variable is OFF, as in FIG. 4.

As described above, the carrier variable unit 7b of the control device 7 outputs a command for changing the carrier frequency 41 based on the predetermined carrier frequency variable range 40. As a method for determining the carrier frequency variable range 40, for example, as shown in FIGS. 8 to 10, the maximum value f _max and the minimum value f _{min of the} carrier frequency 41 to be changed are determined, and the minimum value f _min and the maximum value are determined. The carrier frequency variable range 40 is defined as the range between _{f max and f max.} In this case, the carrier variable portion 7b changes the carrier frequency 41 so as to complement between _{the maximum value f max} and the minimum value f _min. Alternatively, the ± 1 kHz from the central value or mean value _{f typ} of the carrier frequency 41, may be the carrier frequency variable range 40. In this case, the increase / decrease range is not limited to ± 1 kHz, and may be appropriately set to any value. The carrier frequency variable range 40 is predetermined and stored in the storage unit 7c of the control device 7. However, if necessary, the carrier frequency variable range 40 may be appropriately changed by input from the outside or the like.

Further, a case where the power conversion device 8 is applied to the refrigeration cycle device will be described. In the refrigeration cycle apparatus, while the operation of the compressor 61 is stopped, a refrigerant stagnation phenomenon may occur in which the refrigerant accumulates in the compressor 61 due to a temperature difference or a pressure difference of the refrigerant. When the refrigerant stagnation phenomenon occurs, the starting load of the compressor 61 becomes large. Further, at the time of startup, a large amount of the mixed liquid of the refrigerating machine oil and the refrigerant in the compressor 61 is blown out from the compressor 61 in a short time, and the refrigerating machine oil in the compressor 61 is depleted, causing problems such as shaft breakage. there's a possibility that. Therefore, as a measure to prevent falling into the compressor 61, the inside of the compressor 61 is heated by the heater while the operation of the compressor 61 is stopped. Alternatively, the inverter unit 5 applies a restraint energization (a voltage that does not drive the motor 6 of the compressor 61 is applied) to the winding of the motor 6 of the compressor 61 to heat the inside of the compressor 61. In the constrained energization, the heating effect of the refrigerant may be most obtained at a specific carrier frequency (for example, 16 kHz). Here, a specific carrier frequency is referred to as a first carrier frequency. At this time, the carrier variable unit 7b changes the carrier frequency so that the average value or the median value of the switching carrier frequencies of the

switching elements

5a and 5b of the inverter unit 5 becomes the first carrier frequency. For example, when 16 kHz is the easiest to obtain the heating effect, 16 kHz is set as the first carrier frequency, and the carrier variable unit 7b sets the carrier frequency variable range 40 in the range of 16 kHz ± 1 kHz. This will be described by taking FIG. 8 as an example. In FIG. 8, 16 kHz is the first carrier frequency. Therefore, the minimum value f _min of the carrier frequency variable range 40 is 16 kHz-1 kHz = 15 kHz. Further, the maximum value f _max of the carrier frequency variable range 40 is 16 kHz + 1 kHz = 17 kHz. As a result, the carrier frequency variable range 40 is determined in the range from 15 kHz to 17 kHz. At this time, the carrier variable unit 7b changes the carrier frequency 41 in the carrier frequency variable range 40.

Further, the carrier variable frequency such as how many times the carrier frequency is changed per second by the carrier variable unit 7b may be determined in advance in consideration of the total noise amount, the sound heard due to switching, and the like. ..

The inverter unit 5 may have a function of outputting high frequency power due to switching of the

switching elements

5a and 5b to the motor 6 which is a load to heat the load. Specifically, the inverter unit 5 may have a function of performing restraint energization as a measure to prevent falling into the compressor 61. Further, the power conversion device 8 may be used as an inverter device having a function of heating the refrigerant in the compressor 61 by energizing the motor 6 mounted on the compressor 61.

As described above, in the first embodiment, the control device 7 has the carrier variable unit 7b, and changes the switching carrier frequency of the

switching elements

5a and 5b of the inverter unit 5. The carrier variable unit 7b changes the carrier frequency 41 in accordance with the preset carrier frequency variable range 40, for example, so that the noise component 22 emitted by the power conversion device 8 is reduced. Thereby, the noise component 22 due to the switching of the

switching elements

5a and 5b can be dispersed. As a result, the influence of noise on the AC power supply 1 can be suppressed. Alternatively, the carrier variable unit 7b changes the carrier frequency 41 in accordance with the preset carrier frequency variable range 40, for example, so that the high frequency component of the sound produced by the power conversion device 8 is reduced. This makes it possible to reduce noise such as electromagnetic noise of the motor 6 due to harmonic components included in the output waveform of the inverter unit 5.

In the first embodiment, the carrier variable unit 7b changes the carrier frequency 41 itself by using a change pattern selected in advance according to a problem such as noise amount or sound, so that the noise of the carrier frequency, which is the frequency to be suppressed, and the noise of the carrier frequency. , The noise level of the harmonic component can be lowered.

As a result, in the power conversion device 8 that employs an electrolytic capacitorless inverter, the influence of noise on the AC power supply 1 side can be suppressed even if high frequency switching is performed. As a result, it is possible to prevent malfunction or failure of other devices connected to the AC power supply 1 side. Further, in the first embodiment, since the carrier variable portion 7b is provided to change the carrier frequency, it is not necessary to mount a noise filter corresponding to a plurality of carrier frequencies for suppressing the influence of noise. As a result, it becomes possible to use the refrigerant heating in the compressor by high frequency switching at low cost. As described above, according to the first embodiment, it is possible to carry out the restraint energization by the electrolytic capacitorless inverter. Further, at that time, the outflow of high-frequency noise to the power supply side becomes an issue, but in the first embodiment, as a method of preventing it, a carrier variable portion 7b is provided and the carrier frequency is changed to a triangular wave shape or a sinusoidal shape. I'm changing. As a result, in the electrolytic capacitor-less inverter, it becomes possible to perform restraint energization while suppressing the outflow of high-frequency noise to the power supply side.

Embodiment 2.
FIG. 6 is a circuit diagram showing the configuration of the power conversion device 8 according to the second embodiment. As shown in FIG. 6, in the second embodiment, the Vdc synchronization unit 7d is added to the control device 7.

Further, in FIG. 6, an AC power supply 1A is provided instead of the AC power supply 1 of FIG. The AC power supply 1A is a single-phase AC power supply. Therefore, in FIG. 6, a rectifying unit 2A is provided instead of the rectifying unit 2 of FIG. As shown in FIG. 6, the rectifying unit 2A includes four six rectifying diodes. The four rectifying diodes are connected in series two by two to form a total of two series circuits. The two series circuits are connected in parallel. The rectifying unit 2A rectifies the AC voltage input from the AC power supply 1A and converts it into a DC voltage. The DC voltage is applied to the DC link unit 4 through the reactor 3.

Since the other configurations and operations of the second embodiment are the same as those of the first embodiment, the description thereof will be omitted here.

Not only in the case of FIG. 6, but also in the second embodiment, as shown in FIG. 7, the power conversion device 8 is connected to the AC power supply 1 composed of the three-phase AC power supply as in the first embodiment. You may. FIG. 7 is a circuit diagram showing a modified example of the power conversion device 8 according to the second embodiment. In FIG. 7, the AC power supply 1 is connected to the rectifying unit 2 as in FIG. 1.

As shown in FIGS. 6 and 7, a voltage signal indicating the voltage of the DC link unit 4 detected by the DC voltage detection unit 9 is input to the Vdc synchronization unit 7d. The Vdc synchronization unit 7d detects the pulsating component 11a from the voltage signal, synchronizes with the pulsating component 11a, and outputs a Vdc synchronization command. The Vdc synchronization command is input to the carrier variable unit 7b. The carrier variable unit 7b changes the carrier frequency 41 in synchronization with the pulsating component 11a based on the Vdc synchronization command. As described above, in the second embodiment, the Vdc synchronization unit 7d realizes the carrier variation synchronized with the pulsating component 11a of the voltage Vdc of the DC link unit 4 by inputting the Vdc synchronization command to the carrier variable unit 7b. ..

As shown in the above equation (1), the noise current Icommon of the common mode noise depends on the stray capacitance C between the inverter circuit board or the motor 6 and the ground and the change of the voltage v applied thereto. Therefore, noise is likely to occur in the inverter section 5 and the motor 6 whose voltage frequently changes due to switching. In the second embodiment, when the carrier is variable, the center value or the average value _ftyp of the carrier frequency variable range 40 that changes the carrier frequency is adjusted to the timing when the voltage Vdc of the DC link portion 4 becomes low, so that noise is generated. Lower the level of ingredients.

Hereinafter, the operation of the Vdc synchronization unit 7d will be described with reference to FIGS. 8 to 10 as an example. 8 to 10 show an example of a carrier frequency change pattern based on the Vdc synchronization command of the Vdc synchronization unit 7d provided in the control device 7 of the power conversion device 8 according to the second embodiment. For example, a case where the carrier variable unit 7b changes the carrier frequency 41 in the carrier frequency variable range 40 of 16 kHz ± 1 kHz will be described. In this case, the carrier frequency variable range 40 is in the range from 15 kHz to 17 kHz. Further, the center value or the average value _ftype of the carrier frequency variable range 40 is 16 kHz. At this time, the Vdc synchronization unit 7d issues a Vdc synchronization command indicating the timing of the valley 11b so that the timing t1 at which the carrier frequency 41 becomes 16 kHz coincides with the valley 11b of the pulsation component 11a of the voltage Vdc of the DC link unit 4. , Is input to the carrier variable unit 7b. The timing t1 is the timing for every 1/2 cycle of the carrier frequency 41. The carrier variable unit 7b matches the timing t1 at which the carrier frequency becomes 16 kHz with the valley 11b of the pulsating component 11a of the voltage Vdc of the DC link unit 4 according to the Vdc synchronization command. Further, the carrier variable unit 7b allocates another frequency of the carrier frequency, that is, a frequency of 16 kHz <f _carrier ≤ 17 kHz and 15 kHz ≤ f _carrier <16 kHz to a frequency other than the valley 11b of the pulsating component 11a.

As a result, the center value or the average value _ftype of the carrier frequency 41 remains at 16 kHz, and the noise coming from the ripple of the component of 16 kHz itself and its harmonic component becomes small, so that the ripple and noise caused by the carrier decrease on average. Will be.

As described above, also in the second embodiment, as in the first embodiment, the carrier variable by the carrier variable portion 7b may be performed so as to be linear as shown in FIG. 8, and FIG. 9 shows. As shown, it may be performed in a curved shape such as a sinusoidal shape. Further, as shown in FIG. 10, the carrier variable may be performed in a stepped manner. As described above, also in the second embodiment, as in the first embodiment, the change pattern of the carrier variable is not determined to be one, but is selected in advance according to the purpose of use or the environment of use, and the selected change. The pattern is preset in the carrier variable portion 7b.

The second embodiment can be applied regardless of the number of phases of the AC power supply 1 and the AC power supply 1A, but is particularly suitable for a single-phase electrolytic capacitorless inverter. In the case of a single phase, the fluctuation of the voltage of the DC link portion 4 is larger than that in the case of the three phase, and the voltage value becomes close to 0V in the valley 11b portion of the pulsating component 11a of the voltage Vdc of the DC link portion 4. Therefore, when the carrier frequency 41 is changed in synchronization with the pulsation component 11a of the voltage Vdc, the frequency component assigned to the valley 11b portion of the pulsation component 11a has a voltage change of almost 0, so that the common mode noise is further reduced. Become.

In the second embodiment, the carrier variable frequency of how many times the carrier is changed per second depends on the frequency of the pulsating component 11a of the voltage Vdc. In that case, it is 6 times the power supply cycle.

As described above, also in the second embodiment, the control device 7 has the carrier variable unit 7b to make the switching carrier frequencies of the

switching elements

5a and 5b variable, as in the first embodiment. Therefore, the same effect as that of the first embodiment can be obtained in the second embodiment.

Further, in the second embodiment, the control device 7 has a Vdc synchronization unit 7d. The Vdc synchronization unit 7d outputs a Vdc synchronization command in synchronization with the pulsation component 11a of the voltage Vdc of the DC link unit 4. As a result, the carrier variable portion 7b makes the carrier frequency 41 variable in synchronization with the pulsating component 11a, so that the average value of the noise itself can be lowered. Further, by changing the carrier frequency 41 in synchronization with the pulsation of the AC power supply 1, the average value of noise can be further reduced.

In the power conversion device 8 according to the above-described first and second embodiments, the power conversion element, the switching element, and the diode used in the rectifying unit 2 and the inverter unit 5 may be configured by a wideband gap semiconductor. Wide bandgap semiconductors have a larger bandgap than silicon (Si). Examples of the wide bandgap semiconductor include silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga ₂ O ₃ ), and diamond.

The power conversion element, switching element and diode formed by such a wide bandgap semiconductor have high withstand voltage resistance and high allowable current density. Therefore, the power conversion element, the switching element, and the diode can be miniaturized. Further, by using these miniaturized power conversion elements, switching elements and diodes, it is possible to miniaturize the semiconductor module incorporating these power conversion elements, switching elements and diodes.

In addition, since the wide bandgap semiconductor has high heat resistance, the heat dissipation fins of the heat sink can be miniaturized, and the water-cooled portion can be air-cooled, so that the semiconductor module can be further miniaturized. ..

Further, since the wide bandgap semiconductor has a low power loss, it is possible to improve the efficiency of power conversion elements, switching elements and diodes, and by extension, it is possible to improve the efficiency of semiconductor modules.

It is desirable that all of the power conversion element, switching element and diode are formed of a wide bandgap semiconductor. However, any one of them may be formed of a wide bandgap semiconductor, and even in that case, the above effect can be obtained.

The power conversion device according to the present disclosure can be widely used not only for refrigeration cycle devices such as air conditioners, but also for devices that drive loads such as compressors or motors.

1 AC power supply, 1A AC power supply, 2 rectifying unit, 2A rectifying unit, 3 reactor, 4 DC link unit, 4a small capacity capacitor, 5 inverter unit, 5a upper arm switching element, 5b lower arm switching element, 5c recirculation diode, 6 motor, 7 control device, 7a control unit, 7b carrier variable unit, 7c storage unit, 7d Vdc synchronization unit, 8 power conversion device, 9 DC voltage detector, 10 rectangular frame, 11 voltage waveform, 11a pulsation component, 11b valley , 20 carrier ripple, 21 carrier ripple, 22 noise component, 40 carrier frequency variable range, 41 carrier frequency, 50 refrigeration cycle device, 52 refrigerant piping, 60 outdoor unit, 61 compressor, 62 four-way valve, 63 heat exchanger, 64 Blower fan, 64a fan motor, 64b wing part, 65 expansion valve, 70 indoor unit, 71 heat exchanger, 72 blower fan, 72a fan motor, 72b wing part.

Claims

A rectifier that rectifies the voltage supplied from the power supply,
An inverter unit having a power conversion element and converting the voltage rectified by the rectifying unit by switching of the power conversion element and outputting it to a load.
A DC link unit connected between the rectifying unit and the inverter unit and provided with a capacitor having a capacity that does not smooth the voltage rectified by the rectifying unit.
A control unit that controls the switching of the power conversion element of the inverter unit based on the switching carrier frequency, and a control unit.
A power conversion device including a carrier variable unit that outputs a command for changing the switching carrier frequency to the control unit based on a preset change pattern.
A DC voltage detection unit that detects the voltage of the DC link unit,
It is provided with a Vdc synchronization unit that detects the pulsation component of the voltage detected by the DC voltage detection unit and outputs a Vdc synchronization command to the carrier variable unit in synchronization with the pulsation component.
Based on the Vdc synchronization command, the carrier variable unit outputs a command for changing the switching carrier frequency in synchronization with the pulsating component to the control unit as the command.
The power conversion device according to claim 1.
The carrier variable unit outputs a command for changing the switching carrier frequency within a preset carrier frequency variable range to the control unit as the command.
The power conversion device according to claim 1 or 2.
The carrier variable unit outputs a command for changing the switching carrier frequency to the control unit as the command so as to reduce the noise generated by the power conversion device.
The power conversion device according to any one of claims 1 to 3.
The carrier variable unit outputs a command for changing the switching carrier frequency as the command to the control unit so that the high frequency component of the sound generated by the power conversion device is reduced.
The power conversion device according to any one of claims 1 to 3.
The inverter unit outputs high-frequency power generated by switching of the power conversion element to the load to heat the load.
The power conversion device according to any one of claims 1 to 5.
The inverter unit is mounted on an inverter device whose load is a motor.
The power conversion device according to any one of claims 1 to 6.
The power conversion device is mounted on an inverter device that drives a compressor.
The power conversion device according to any one of claims 1 to 7.
The power converter is
It is mounted on an inverter device having a function of heating the refrigerant in the compressor by energizing a motor mounted on the compressor.
The power conversion device according to any one of claims 1 to 8.
The power conversion device is mounted on the refrigeration cycle device.
The power conversion device according to any one of claims 1 to 9.
The power conversion element of the inverter unit is formed of a wide bandgap semiconductor.
The wide bandgap semiconductor is silicon carbide, gallium nitride, gallium oxide, or diamond.
The power conversion device according to any one of claims 1 to 10.