JP7399331B2 - Power conversion equipment, motor drive equipment, blowers, compressors and air conditioners - Google Patents

Description

The present invention relates to a power conversion device that converts an AC voltage output from an AC power source into a DC voltage, a motor drive device equipped with the power conversion device, a blower and a compressor equipped with the motor drive device, and a blower or compressor. Regarding the equipped air conditioner.

2. Description of the Related Art In a power conversion device that is connected to an AC power source and converts AC power into DC power while improving the power factor, there is a demand for higher power density of the device. In order to achieve high power density, it is essential to reduce the loss and size of the device. In order to reduce the loss and reduce the size, it is important to reduce the loss and reduce the size of the reactor, which has a high volume ratio among the components of the device. Generally, one way to make a reactor smaller is to increase the frequency of the circuit and reduce the required capacity. On the other hand, increasing the frequency of the circuit increases losses in reactors and switching elements, resulting in lower conversion efficiency and larger coolers.

To address the above-mentioned problems, Patent Document 1 listed below discloses a multi-level power conversion device. The power conversion device described in Patent Document 1 includes a sub-converter including four switching elements and one capacitor between a reactor and a main converter. In Patent Document 1, by driving the switching elements of the main converter and the sub-converter at switching periods shifted by half a period, a high power factor is achieved while interposing the capacitor voltage of the sub-converter between the output DC voltage and the input AC voltage. performs power control. As a result, the voltage applied to the reactor is lower than that of a typical high power factor converter with a bridgeless configuration, and the reactor capacity and loss are reduced compared to a high power factor converter with the same specifications.

Patent No. 6129450

However, in Patent Document 1, the driving frequency of the circuit is always 10 kHz or more under any operating conditions. Therefore, there is a problem that the switching loss of the switching element and the high frequency loss of the reactor are large, and the conversion efficiency of the power converter is low.

The present invention has been made in view of the above, and an object of the present invention is to obtain a highly efficient power conversion device by reducing switching loss of a switching element and high frequency loss of a reactor.

In order to solve the above-mentioned problems and achieve the objective, a power conversion device according to the present invention includes a reactor, a main converter having a switching element, a first capacitor that holds the DC voltage converted by the main converter, A sub-converter having a switching element, a second capacitor that is provided between the reactor and the first capacitor and holds the DC voltage converted by the sub-converter, and a controller that controls conduction of the switching element. . The reactor, main converter, sub-converter, first capacitor, and second capacitor are provided between the AC power source and the DC load. The power conversion device performs power conversion between an alternating current voltage of an alternating current power supply and a first capacitor voltage that is a voltage of a first capacitor. The sub-converter has a first leg connected in parallel to the second capacitor, and a second leg connected in parallel to the second capacitor and the first leg. The main converter has a third leg connected in parallel to the first capacitor, and a fourth leg connected in parallel to the first capacitor and the third leg. The midpoint of the first leg is connected to one side of the AC power source via a reactor, the midpoint of the second leg is connected to the midpoint of the third leg, and the midpoint of the fourth leg is connected to the other side of the AC power source. connected to. The connection polarity between the first capacitor and the second capacitor is configured to be reversible depending on the operating region. The controller performs switching control on the switching element at a switching frequency of once or more and 20 or less times per half cycle of the AC voltage.

According to the present invention, it is possible to drive the power converter device with high efficiency by reducing the switching loss of the switching element and the high frequency loss of the reactor.

A diagram showing a basic circuit configuration of a power conversion device according to Embodiment 1 A diagram used to explain the concept of an operating region when the power conversion device according to Embodiment 1 performs step-up operation. A diagram used to explain the concept of an operating region when the power conversion device according to Embodiment 1 performs step-down operation. Diagram showing the relationship between the operating region defined in FIGS. 2 and 3 and the operating state of the main circuit A diagram showing an example of a current path when the power conversion device according to Embodiment 1 performs power conversion. A diagram showing an example of a switching pattern when the power conversion device according to Embodiment 1 performs step-up operation. A diagram showing an example of a switching pattern when the power conversion device according to Embodiment 1 performs step-down operation. Block diagram showing the internal configuration of the controller in Embodiment 1 A block diagram showing the detailed configuration of the DC capacitor voltage controller shown in Figure 8. Time chart used to explain the operation of the addition/subtraction determiner shown in FIG. 8 Block diagram used to explain the operation of the addition/subtraction determiner shown in FIG. 8 Block diagram showing the internal configuration of a controller in Embodiment 2 A diagram showing an example of a switching pattern when the power conversion device according to Embodiment 2 performs step-up operation. A diagram showing an example of a switching pattern when the power conversion device according to Embodiment 2 performs step-down operation. A block diagram showing the detailed configuration of the carrier wave generator shown in FIG. 12 A block diagram showing the detailed configuration of the high power factor controller shown in FIG. 12 A block diagram showing the detailed configuration of the gate signal generator shown in FIG. 12 A diagram showing a basic circuit configuration of a power conversion device according to Embodiment 3 A diagram showing a configuration example of a motor drive device according to Embodiment 4 A diagram showing an example in which the motor drive device shown in FIG. 19 is applied to an air conditioner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A power conversion device, a motor drive device, a blower, a compressor, and an air conditioner according to embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below. Furthermore, in the following description, electrical connections will be simply referred to as "connections."

Embodiment 1.
FIG. 1 is a diagram showing a basic circuit configuration of a power conversion device 100 according to the first embodiment. Power conversion device 100 according to Embodiment 1 includes a main circuit 110 and controller 8. The main circuit 110 is a power conversion circuit that converts AC power using an AC voltage output from the AC power supply 1 into DC power using a DC voltage, and applies the DC power to the load 7 . Load 7 is a DC load. A DC load is a load that operates by receiving DC power. A load 7 that includes an inverter that converts DC power into AC power is also included in the DC load referred to herein.

The main circuit 110 includes a current-limiting reactor 2, a sub-converter 3, a main converter 5, and a smoothing capacitor 6, which is a first capacitor. Smoothing capacitor 6 is connected in parallel to main converter 5 and load 7, respectively, between main converter 5 and load 7.

The sub-converter 3 includes a first leg in which a switching element 3a and a switching element 3b are connected in series, a second leg in which a switching element 3c and a switching element 3d are connected in series, and a second capacitor that is a direct current converter. It has a capacitor 4. The first leg, the second leg, and the DC capacitor 4 are connected in parallel with each other.

Examples of the DC capacitor 4 and the smoothing capacitor 6 are aluminum electrolytic capacitors and film capacitors.

The main converter 5 includes a third leg in which a diode 5a and a switching element 5b are connected in series, and a fourth leg in which a diode 5c and a switching element 5d are connected in series. Both the third leg and the fourth leg have a configuration in which the anode of each diode is connected to a switching element. The third leg and the fourth leg are connected in parallel to each other. Note that the diodes 5a and 5c may be replaced with switching elements.

One end of the reactor 2 is connected to one side of the AC power supply 1, and the other end of the reactor 2 is connected to the midpoint of the first leg. The midpoint of the first leg is the connection point between switching element 3a and switching element 3b. In other legs as well, the connection points between switching elements and the connection points between diodes and switching elements are called "midpoints."

In the main converter 5 , the midpoint of the third leg is connected to the midpoint of the second leg of the sub-converter 3 , and the midpoint of the fourth leg is connected to the other side of the AC power supply 1 .

An example of the switching elements 3a, 3b, 3c, 3d (hereinafter appropriately referred to as "3a to 3d") and the switching elements 5b, 5d is a metal oxide semiconductor field effect transistor (Metal Oxide Semiconductor Field Effect Transistor: MOSFET). Antiparallel connection means that the drain of the MOSFET and the cathode of the diode are connected, and the source of the MOSFET and the anode of the diode are connected. Note that a parasitic diode included in the MOSFET itself may be used as the diode. A parasitic diode is also called a body diode.

Instead of MOSFET, an insulated gate bipolar transistor (IGBT) or a high electron mobility transistor (HEMT) may be used. As the HEMT, a cascode type GaN (Gallium Nitride)-HEMT is suitable.

Smoothing capacitor 6 smoothes and holds the DC voltage converted by main converter 5. The polarity of smoothing capacitor voltage Vdc, which is the voltage held in smoothing capacitor 6, is indicated by an arrow. The tip of the arrow is the high potential side, and the opposite side is the low potential side. This definition also applies to the sub-converter 3. In addition, in the AC power supply 1, when the tip of the arrow is at a high potential, it is defined as positive polarity, and when the opposite side is at a high potential, it is defined as negative polarity.

Power converter 100 further includes voltage detectors 30, 31, 33 and current detector 32.

Voltage detector 30 detects smoothing capacitor voltage Vdc. Note that in the following description, the smoothing capacitor voltage may be referred to as a "first capacitor voltage" and the voltage detector 30 may be referred to as a "first voltage detector." The detected value of the smoothing capacitor voltage Vdc detected by the voltage detector 30 is input to the controller 8.

Voltage detector 31 detects DC capacitor voltage Vsub, which is the voltage of DC capacitor 4 . Note that in the following description, the DC capacitor voltage may be referred to as a "second capacitor voltage" and the voltage detector 31 may be referred to as a "second voltage detector". The detected value of the DC capacitor voltage Vsub detected by the voltage detector 31 is input to the controller 8.

Current detector 32 detects alternating current iac flowing through reactor 2 . The detected value of the alternating current iac detected by the current detector 32 is input to the controller 8.

Voltage detector 33 detects AC voltage vac output from AC power supply 1 . Note that the voltage detector 33 may be referred to as a "third voltage detector". The detected value of the AC voltage vac detected by the voltage detector 33 is input to the controller 8.

The controller 8 generates gate signals G3a, G3b, G3c, and G3c for controlling the conduction of the switching elements 3a to 3d based on the detected values of the smoothing capacitor voltage Vdc, the DC capacitor voltage Vsub, the AC voltage vac, and the AC current iac. G3d (hereinafter appropriately referred to as "G3a to G3d") and gate signals G5b and G5d for controlling conduction of switching elements 5b and 5d.

Sub-converter 3 and main converter 5 each have a gate drive circuit (not shown). Each gate drive circuit of the sub-converter 3 generates a drive pulse using gate signals G3a to G3d output from the controller 8, and applies the generated drive pulse to the gate of the corresponding switching element to drive the corresponding switching element. drive Each gate drive circuit of the main converter 5 generates a drive pulse using gate signals G5b and G5d output from the controller 8, and applies the generated drive pulse to the gate of the corresponding switching element to drive the corresponding switching element. drive

The internal configuration of the controller 8 and the detailed operation of the controller 8 will be described later.

In the controller 8, the processor 8a is an arithmetic unit such as an arithmetic unit, a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor).

The memory 8b is a nonvolatile memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), or EEPROM (registered trademark) (Electrically EPROM). It is a permanent or volatile semiconductor memory.

The memory 8b stores functions of the controller 8, which will be described later, and programs that execute the functions of the controller 8, which will be described later. The processor 8a exchanges necessary information via an interface including an analog-to-digital converter and a digital-to-analog converter (not shown), and performs necessary processing by executing a program stored in the memory 8b. The calculation results by the processor 8a can be stored in the memory 8b.

Note that the functions of the controller 8 may be realized using a processing circuit. The processing circuit referred to herein may be a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. Note that even in a configuration using a processing circuit, some of the processing in the controller 8 may be performed by the processor 8a.

The power conversion device 100 configured as described above performs power conversion between the AC voltage output from the AC power supply 1 and the first capacitor voltage, which is a DC voltage held in the smoothing capacitor 6. This power conversion function is performed by reactor 2, sub-converter 3, and main converter 5. Further, the power converter 100 controls conduction of the switching elements 3a to 3d, 5b, and 5d so that the second capacitor voltage held in the DC capacitor 4 matches the command voltage. This function is handled by the controller 8.

Although FIG. 1 discloses a configuration in which one reactor 2 is connected to one side of the AC power source 1, the present invention is not limited to this configuration. A configuration may also be adopted in which one reactor 2 is connected to the other side of the AC power supply 1. Alternatively, the two divided reactors 2 may be connected to both one side and the other side of the AC power source 1. Alternatively, the divided reactors 2 may be wound around the same core to form one magnetically coupled reactor and connected to either one side or the other side of the AC power source 1.

Next, the main points of control in the power conversion device 100 according to the first embodiment will be explained with reference to the drawings of FIGS. 2 to 7. FIG. 2 is a diagram used to explain the concept of an operating region when power conversion device 100 according to the first embodiment performs a boost operation. FIG. 3 is a diagram used to explain the concept of an operating region when power conversion device 100 according to the first embodiment performs voltage step-down operation. FIG. 4 is a diagram showing the relationship between the operating region defined in FIGS. 2 and 3 and the operating state of the main circuit 110. FIG. 5 is a diagram illustrating an example of a current path when power conversion device 100 according to Embodiment 1 performs power conversion. FIG. 6 is a diagram illustrating an example of a switching pattern when power conversion device 100 according to the first embodiment performs a boost operation. FIG. 7 is a diagram illustrating an example of a switching pattern when power conversion device 100 according to the first embodiment performs a step-down operation.

FIG. 2 shows the voltage relationship when the smoothing capacitor voltage Vdc is larger than the absolute value |vac| of the AC voltage vac in a half cycle of the AC voltage vac (hereinafter referred to as "AC half cycle"). There is. Since the smoothing capacitor voltage Vdc is larger than the absolute value |vac|, it is necessary to boost the AC voltage vac. Therefore, the power converter 100 performs a boost operation. Hereinafter, the mode in which the power conversion device 100 is operated to boost the voltage will be referred to as a "boost operation mode."

Further, FIG. 3 shows the voltage relationship in the case where the AC half cycle includes a region where the smoothing capacitor voltage Vdc is smaller than the absolute value |vac| of the AC voltage vac. Since the smoothing capacitor voltage Vdc is smaller than the absolute value |vac|, it is necessary to step down the AC voltage vac. Therefore, the power conversion device 100 performs a step-down operation. Hereinafter, the mode in which the power conversion device 100 operates in a step-down operation will be referred to as a "step-down operation mode."

In FIGS. 2 and 3, α1 and α2 are phases such that Vsub=|vac|. Further, β1 and β2 are phases such that Vdc=|vac|.

In FIGS. 2 and 3, the operating region where the phase θ satisfies 0≦θ<α1 and α2<θ≦π is an operating region where the relationship |vac|<Vsub<Vdc holds true. This operating region is defined as region 1.

Further, the region of α1≦θ≦α2 in FIG. 2 and the operating region that satisfies α1≦θ<β1 and β2<θ≦α2 in FIG. 3 are operating regions that satisfy Vsub≦|vac|<Vdc. This operating region is defined as region 2.

Further, in FIG. 3, the operating region that satisfies β1≦θ≦β2 is an operating region that satisfies Vsub<Vdc≦|vac|. This operating region is defined as region 3.

FIG. 4 shows the operating states of the reactor 2 and DC capacitor 4 corresponding to each operating region defined in FIGS. 2 and 3, and the magnitude of the reactor applied voltage, which is the voltage applied to the reactor 2. .

The reactor 2 has two operating states: "excitation" and "reset". “Excitation” is an operation of accumulating electromagnetic energy in the reactor 2. “Reset” is an operation that causes the electromagnetic energy accumulated in the reactor 2 to be released.

There are three operating states of the DC capacitor 4: "through", "discharging", and "charging". “Through” is an operation in which the alternating current iac is caused to flow through a path that does not pass through the direct current capacitor 4. “Discharge” is an operation of discharging the DC capacitor 4. When the DC capacitor 4 is discharged, the charge accumulated in the DC capacitor 4 is transferred to the smoothing capacitor 6. “Charging” is an operation of charging the DC capacitor 4. The DC capacitor 4 is charged using the electric power of the AC power supply 1 and the electromagnetic energy stored in the reactor 2.

FIG. 5 shows a current path when the voltage applied to the reactor becomes "vac-Vdc+Vsub" in region 2 of FIG. 4. Arrows in FIG. 5 indicate current paths through which alternating current iac flows. As shown in FIG. 5, when the reactor applied voltage becomes "vac-Vdc+Vsub", the controller 8 controls the switching elements 3b, 3c, and 5d to be turned on, and the switching elements 3a, 3d, and 5b to be turned off. controlled. Regarding other operations, the current path of the alternating current iac can be shown similarly to FIG. 5. Note that the explanation here is omitted.

The lower part of FIG. 6 shows an example of a switching pattern in the boost operation mode. The lower part of FIG. 7 shows an example of a switching pattern in the step-down operation mode. In addition, in the upper parts of FIGS. 6 and 7, smoothing capacitor voltage Vdc, smoothing capacitor voltage command Vdc* which is the command value of smoothing capacitor voltage Vdc, DC capacitor voltage Vsub, and DC which is the command value of DC capacitor voltage Vsub are shown. The waveforms of capacitor voltage command Vsub*, AC voltage vac, and AC current iac are shown.

In FIG. 6, the switching pattern in section A in region 2 is the switching pattern when the operation shown in FIG. 5 occurs. Furthermore, the switching pattern in section B in region 1 in FIG. 6 performs the operation shown in region 1 in FIG. 4 in which the DC capacitor 4 is "through" and the voltage applied to the reactor is "vac".

Next, the internal configuration of the controller 8 in the first embodiment will be explained. FIG. 8 is a block diagram showing the internal configuration of controller 8 in the first embodiment. The controller 8 includes an operating region determiner 9, a feed forward (FF) duty (Duty) (hereinafter referred to as "FF_Duty") calculator 10, a DC capacitor voltage controller 11, and an addition/subtraction determiner 12. , an adder 12a, and a gate signal generator 13.

The operating region determination device 9 generates a region determination signal Sig_SP based on each detected value of the AC voltage vac, the smoothing capacitor voltage Vdc, and the DC capacitor voltage Vsub. The area determination signal Sig_SP is a signal indicating in which area of FIG. 2 or 3 the operating state of the power conversion device 100 is in at the time of determination. The region determination signal Sig_SP generated by the operating region determiner 9 is input to the FF_Duty calculator 10 , the addition/subtraction determiner 12 , and the gate signal generator 13 . Each arithmetic unit performs arithmetic operations according to the operating area.

The FF_Duty calculator 10 calculates the FF_Duty ratio D_Vdc based on the detected value of the AC voltage vac and the area determination signal Sig_SP. When calculating the FF_Duty ratio D_Vdc, the DC capacitor 4 is set to be charged and discharged the same number of times in each AC half cycle in each region shown in FIG. 2 or 3. For example, in a certain AC half cycle, if the DC capacitor 4 is charged once, the DC capacitor 4 is discharged once, and if the DC capacitor 4 is charged twice, the DC capacitor 4 is discharged twice. be exposed. Note that the number of times of charging and discharging, which is the total value of the number of times of charging and the number of discharging, also includes "0".

Charging and discharging in each operating region are set with reference to FIG. 4. When the number of times of charging and discharging is "0", "through" in FIG. 4 is selected. Note that, although it is preferable that a set of "charging" and "discharging" for the same number of times be selected for each operating region, the present invention is not limited thereto. A set of "charging" and "discharging" may be selected across the operating range as long as it is within the period of an AC half cycle.

Further, the number of times of charging and discharging can be determined based on the capacity of the DC capacitor 4, the withstand voltage of the main circuit components, and the power factor of the main circuit 110. When the number of times of charging and discharging is small, switching loss can be reduced, but control responsiveness deteriorates, leading to a decrease in power factor and an increase in the amount of voltage ripple. Therefore, in order to operate the power conversion device 100 stably, it is necessary to increase the capacitor capacity. On the other hand, if the number of charging and discharging operations is large, the capacitor capacity may be small and control responsiveness improves, but switching loss increases.

FIG. 9 is a block diagram showing the detailed configuration of the DC capacitor voltage controller 11 shown in FIG. 8. The DC capacitor voltage controller 11 includes a preprocessor 11a and a sample and hold device 11b. The DC capacitor voltage controller 11 controls the DC capacitor voltage based on the detected value of the DC capacitor voltage Vsub so that the DC capacitor voltage Vsub follows a DC capacitor voltage command Vsub* which is a command value of the DC capacitor voltage Vsub. Generate command duty ratio D_Vsub.

The preprocessor 11a proportionally controls the deviation between the DC capacitor voltage command Vsub* and the detected value of the DC capacitor voltage Vsub, and calculates a normalized duty ratio by dividing the control value by the DC capacitor voltage command Vsub*. Calculate. The sample and hold device 11b updates the value of the output of the preprocessor 11a at a sample and hold period, and outputs the updated value to the addition/subtraction determination device 12 as the DC capacitor voltage command duty ratio D_Vsub.

In the following description, the FF_Duty ratio described above may be referred to as a "first duty ratio," and the DC capacitor voltage command duty ratio described above may be referred to as a "second duty ratio."

FIG. 10 is a time chart used to explain the operation of the addition/subtraction determiner 12 shown in FIG. FIG. 11 is a block diagram used to explain the operation of the addition/subtraction determiner 12 shown in FIG. 8.

The waveform in FIG. 10 is an example of the operation in region 2 in the positive half wave of the alternating current voltage vac. FIG. 10 shows, in order from the top side, the waveform of the alternating current iac and the waveforms of the gate signals G3a to G3d, G5b, and G5d for controlling each of the switching elements 3a to 3d, 5b, and 5d. . Further, the operating state of the DC capacitor 4 is shown in the lower part of FIG. The reactor 2 is excited at times t0-t1 and t2-t3, and the excitation of the reactor 2 is reset at times t1-t2 and t3-t4. Therefore, in the example of FIG. 10, two pairs of switching control, one pair of excitation and one reset, that is, four switching controls are performed.

A DC capacitor voltage command duty ratio D_Vsub is input to the addition/subtraction determiner 12 . The addition/subtraction determiner 12 multiplies the DC capacitor voltage command duty ratio D_Vsub by a value of "1" or "-1" based on the area determination signal Sig_SP. That is, the addition/subtraction determiner 12 outputs a non-inverted control signal "+D_Vsub" whose sign is not inverted, or a control signal "-D_Vsub" whose sign is inverted, depending on the area determination signal Sig_SP. The upper part of FIG. 11 shows a situation where a non-inverted control signal "+D_Vsub" is output. The lower part of FIG. 11 shows a situation where the inverted control signal "-D_Vsub" is output.

In the first embodiment, voltage control is performed by changing time t1 and time t3 in FIG.

For example, when the DC capacitor voltage Vsub becomes lower than the DC capacitor voltage command Vsub* due to a disturbance, as shown in the upper part of FIG. 11, at time t1, the DC capacitor voltage The command duty ratio D_Vsub is positive and added. Further, as shown in the lower part of FIG. 11, at time t3, the adder 12a adds a negative DC capacitor voltage command duty ratio D_Vsub to the FF_Duty ratio D_Vdc. As a result, the main circuit 110 operates in such a manner that the amount of charge to the DC capacitor 4 increases and the amount of discharge decreases.

Contrary to the above, when the DC capacitor voltage Vsub becomes higher than the DC capacitor voltage command Vsub*, at time t1, the adder 12a adds the DC capacitor voltage command duty ratio D_Vsub with a negative value to the FF_Duty ratio D_Vdc. be done. Furthermore, at time t3, the adder 12a adds a positive DC capacitor voltage command duty ratio D_Vsub to the FF_Duty ratio D_Vdc. As a result, the main circuit 110 operates in such a manner that the amount of charge to the DC capacitor 4 decreases and the amount of discharge increases.

Through the above operation, the DC capacitor voltage Vsub is controlled according to the DC capacitor voltage command Vsub*. In addition, in FIG. 10, the operation in region 2 in the positive half wave of the AC voltage vac has been explained, but the same operation also applies in regions 1 and 3 in the positive half wave and in regions 1 to 3 in the negative half wave. can perform constant voltage control.

Returning to FIG. 8, the gate signal generator 13 receives the AC voltage vac, the area determination signal Sig_SP, and the duty ratio sum D_total output from the adder 12a. The gate signal generator 13 generates gate signals G3a to G3d, G5b, and G5d based on the AC voltage vac, the area determination signal Sig_SP, and the duty ratio sum D_total output from the adder 12a. Gate signals G3a to G3d, G5b, and G5d are applied to switching elements 3a to 3d, 5b, and 5d, respectively, and conduction of switching elements 3a to 3d, 5b, and 5d is controlled.

Through the above control, the power conversion device 100 of the first embodiment can supply the required power to the load 7 through control of the first capacitor voltage. Further, while controlling the first capacitor voltage, it is possible to perform voltage constant control in which the second capacitor voltage follows the command value.

Further, in the first embodiment, the number of times of switching in an AC half cycle is at most 20 times. That is, in the first embodiment, switching control is performed on the switching elements 3a to 3d, 5b, and 5d of the main circuit 110 by a number of switching times of less than ten times in an AC half cycle.

When the frequency of the AC voltage vac is 50 Hz, the AC half cycle is 10 [ms]. If switching control is periodically performed 20 times in an AC half cycle, the time required for one switching control is 0.5 [ms]. If 0.5 [ms] is one switching period, the switching frequency is 5 [kHz], which allows the switching frequency to be reduced compared to the conventional art. Thereby, the switching loss of the switching element and the high frequency loss of the reactor can be reduced, so that the power converter can be driven with higher efficiency than in the past.

In addition, although the description so far has been based on the assumption that the DC capacitor 4 is charged and discharged at least once in an AC half cycle, the present invention is not limited to this. In the case of a boost operation using only regions 1 and 2, it is also possible to set the number of charging and discharging times of the DC capacitor 4 in an AC half cycle to 0, and operate the main circuit 110 only by controlling the smoothing capacitor voltage Vdc. In this case, the FF_Duty calculator 10 selects only the "through" operation in FIG. 4 and calculates the FF_Duty ratio D_Vdc. Then, gate signals G3a to G3d, G5b, and G5d are generated using the calculated FF_Duty ratio D_Vdc. In this case, feedback control of the DC capacitor voltage Vsub becomes unnecessary. For this reason, the number of times of switching and the conduction time depending on the operating conditions may be stored in advance in the memory 8b of the controller 8, and the stored information may be read out to operate the main circuit 110.

As described above, according to the power conversion device according to the first embodiment, the controller switches the plurality of switching elements at least once and at most ten times (less than 20 times) in a half cycle of the AC voltage. to control switching. Thereby, the switching loss of the switching element and the high frequency loss of the reactor can be reduced, and the power conversion device can be driven with high efficiency. In addition, during this switching control, the controller controls the amount of charge and the amount of discharge of the second capacitor in a half cycle of the AC voltage so that the second capacitor voltage matches the command value of the second capacitor voltage. Take control. With this control, it is possible to increase the power factor of the main circuit operation while reducing the switching loss of the switching element and the high frequency loss of the reactor. Thereby, the power conversion device can be driven with high efficiency.

Note that in the above control, the controller can perform switching control while changing the charging time for charging the second capacitor and the discharging time for discharging the second capacitor. Since this control can be performed without using carrier waves, it is possible to easily drive the power converter with high efficiency.

In the above control, the controller charges and discharges the second capacitor at least once each within a half cycle of the AC voltage, and the number of times of charging and the number of times of discharging are within a half cycle of the AC voltage. It is preferable to perform switching control so that the values are equal to each other. Thereby, voltage constant control that causes the second capacitor voltage to follow the command value can be reliably performed.

In addition, in the above control, for the total amount of duty ratio, which is the sum of the first duty ratio for controlling the first capacitor voltage and the second duty ratio for controlling the second capacitor voltage, Preferably, the controller adds or subtracts the second duty ratio to the first duty ratio so that the total amount of duty ratios within a half cycle of the AC voltage is kept constant. Thereby, control of the first capacitor voltage and constant voltage control for causing the second capacitor voltage to follow the command value can be performed simultaneously.

Embodiment 2.
FIG. 12 is a block diagram showing the internal configuration of controller 8A in the second embodiment. In the controller 8A in the second embodiment, the FF_Duty calculator 10 is replaced with a high power factor controller 17 in the configuration of the controller 8 in the first embodiment shown in FIG. It has been replaced by generator 18. Additionally, a carrier wave generator 16 is added. Note that the other configurations are the same or equivalent to the configuration shown in FIG. 8, and the same or equivalent components are denoted by the same reference numerals and redundant explanations will be omitted. Further, the basic circuit configuration is the same or equivalent to that in FIG.

FIG. 13 is a diagram illustrating an example of a switching pattern when power conversion device 100 according to the second embodiment performs a boost operation. Further, FIG. 14 is a diagram showing an example of a switching pattern when power conversion device 100 according to the second embodiment performs a step-down operation. The concept of the operating area explained in the first embodiment is the same in the second embodiment. Power conversion device 100 according to the second embodiment performs switching control on switching elements 3a to 3d, 5b, and 5d while changing the carrier frequency for each operating region. When the carrier frequency is changed, the switching frequency is also changed. Note that in this specification, a period during which the same switching frequency is maintained is defined as a "first switching period."

According to the switching patterns shown in FIGS. 13 and 14, the DC capacitor 4 is operated to be charged and discharged one or more times in each operating region. Note that, as described above, the width of each operating region is determined by the magnitude relationship between the smoothing capacitor voltage Vdc, the DC capacitor voltage Vsub, and the AC voltage vac, so the width of each operating region varies. Therefore, in a region with a narrow period, power factor control is performed using switching control at a higher frequency, and in a region where the period is wide, power factor control is performed using switching control at a lower frequency. On the other hand, as described above, the number of switching times is 20 at most, which is significantly reduced compared to the conventional method. Therefore, it is possible to significantly reduce loss compared to the conventional method, and the power conversion device can be driven with high efficiency.

Note that in the case of the step-down operation shown in FIG. 14, the operating range is increased compared to the case of the step-up operation shown in FIG. Therefore, if the number of times of switching is the same for each operating region, the number of times of switching in an AC half cycle will be greater in the step-down operation. Further, unlike the step-up operation, the step-down operation must be performed while charging and discharging the DC capacitor 4. Therefore, in region 3, switching control for charging and discharging is always performed. Note that this point also applies to the first embodiment. As shown in region 3 of FIG. 4, there is no "through" operation in region 3, and either discharging or charging operation is selected.

FIG. 15 is a block diagram showing the detailed configuration of the carrier wave generator 16 shown in FIG. 12. The carrier wave generator 16 includes a switching frequency calculator 20 and a frequency converter 21.

The switching frequency calculator 20 calculates the time of each operating region in an AC half cycle based on the AC voltage vac, the DC capacitor voltage Vsub, and the smoothing capacitor voltage Vdc. Furthermore, the switching frequency calculator 20 calculates the switching period, which is the reciprocal of the switching frequency, based on the number of charging and discharging times of the DC capacitor 4 set by the user.

The frequency converter 21 generates a carrier wave based on the switching period calculated by the switching frequency calculator 20 and the area determination signal Sig_SP. Note that the carrier wave may be a sawtooth wave or a triangular wave.

As shown in FIG. 15, the switching frequency calculator 20 includes a first time calculator 20a, a second time calculator 20c, a third time calculator 20e, and a fourth time calculator 20i. It includes dividers 20b, 20d, 20g, and 20j, and an adder 20h.

The first time calculator 20a calculates the time Rt1 in region 1 by dividing the DC capacitor voltage Vsub by the AC voltage vac, converting it into time using an inverse trigonometric function, and further dividing by the angular frequency 2πfac. The time Rt1 is a time corresponding to the phase difference from 0 to α1 in FIG. fac is the frequency of the alternating current voltage vac. Hereinafter, the frequency of the AC voltage vac will be referred to as "AC voltage frequency". The switching frequency calculator 20 calculates the switching period Tsw_1 in the region 1 by dividing the time Rt1 by the number of times of charging and discharging in the divider 20b.

The second time calculator 20c calculates the time Rt2b of the region 2 by subtracting the double value of the time Rt1 of the region 1 from the value obtained by dividing the value of 1 by the double value of the AC voltage frequency fac. The double value of time Rt1 is a time corresponding to the phase difference obtained by adding the phase difference from 0 to α1 in FIG. 2 and the phase difference from α2 to π. Further, the value obtained by dividing the value of 1 by twice the value of the AC voltage frequency fac is the time corresponding to the phase difference from 0 to π in FIG. Therefore, the time Rt2b of region 2, which corresponds to the phase difference from α1 to α2 in FIG. 2, is calculated by the processing of the second time calculator 20c. The switching frequency calculator 20 calculates the switching period Tsw_2b in region 2 in the boost operation mode by dividing the time Rt2b by the number of times of charging and discharging in the divider 20d.

For step-down operation, there is an operating range up to region 3, so another control block is provided. The third time calculator 20e converts the smoothing capacitor voltage Vdc divided by the AC voltage vac into time using an inverse trigonometric function, further divides by the angular frequency 2πfac, and further subtracts the time Rt1 in region 1. Calculate the time Rt2s of region 2. The value divided by the angular frequency 2πfac is the time corresponding to the phase difference from 0 to β1 in FIG. Therefore, the time Rt2s of the region 2 can be calculated by subtracting the time Rt1 of the region 1 from the value divided by the angular frequency 2πfac. The switching frequency calculator 20 calculates the switching period Tsw_2s in region 2 in the step-down operation mode by dividing the time Rt2s by the number of times of charging and discharging in the divider 20g.

The adder 20h recalculates the time corresponding to the phase difference from 0 to β1 in FIG. 3 by adding the time Rt2s of region 2 and the time Rt1 of region 1. The fourth time calculator 20i calculates the time Rt3 in region 3 by subtracting the double value of the output of the adder 20h from the value obtained by dividing the value of 1 by the double value of the AC voltage frequency fac. The double value of the output of the adder 20h is the time corresponding to the phase difference obtained by adding the phase difference from 0 to β1 in FIG. 3 and the phase difference from β2 to π. Further, the value obtained by dividing the value of 1 by twice the value of the AC voltage frequency fac is the time corresponding to the phase difference from 0 to π in FIG. 3. Therefore, through the processing of the fourth time calculator 20i, time Rt3 of region 3, which corresponds to the phase difference from β1 to β2 in FIG. 3, is calculated. The switching frequency calculator 20 calculates the switching period Tsw_3 in region 3 in the step-down operation mode by dividing the time Rt3 by the number of times of charging and discharging in the divider 20j.

Note that although the switching frequency calculator 20 outputs the calculated switching periods Tsw_1, Tsw_2b, Tsw_2s, and Tsw_3 to the frequency converter 21, the present invention is not limited thereto. The reciprocals of the switching periods Tsw_1, Tsw_2b, Tsw_2s, and Tsw_3 may be calculated, and each calculated value may be output to the frequency converter 21 as a switching frequency corresponding to the operating region.

Moreover, when switching periods Tsw_1, Tsw_2b, Tsw_2s, and Tsw_3 are information on switching frequencies, times Rt1, Rt2b, Rt2s, and Rt3 can be regarded as reference switching frequencies for calculating each switching frequency. Viewed in this way, the switching frequency calculator 20 shown in FIG. 15 calculates the reference switching frequency corresponding to the operating region in the front stage, and calculates the reference switching frequency and the number of times of charging and discharging the second capacitor in the rear stage. The switching frequency is calculated based on the switching frequency.

The frequency converter 21 generates a carrier wave corresponding to the operating area based on the switching periods Tsw_1, Tsw_2b, Tsw_2s, Tsw_3 calculated by the switching frequency calculator 20 and the area determination signal Sig_SP, and converts the carrier wave into a gate signal generator. Output to 18.

The following is a supplementary explanation of the number of times of charging and discharging. The number of times of charging and discharging is set as an integer including 0 so that it is 1 or more in an AC half cycle. The number of times of charging and discharging can be determined based on the capacity of the DC capacitor 4, the withstand voltage of the main circuit components, and the power factor of the main circuit 110. When the number of times of charging and discharging is small, switching loss can be reduced, but control responsiveness deteriorates, leading to a decrease in power factor and an increase in the amount of voltage ripple. Therefore, in order to operate the power conversion device 100 stably, it is necessary to increase the capacitor capacity. On the other hand, if the number of charging and discharging operations is large, the capacitor capacity may be small and control responsiveness improves, but switching loss increases.

FIG. 16 is a block diagram showing the detailed configuration of the high power factor controller 17 shown in FIG. 12. The high power factor controller 17 includes a current command calculator 17a, a current controller 17b, an FF_Duty calculator 17c, and an adder 17d. The high power factor controller 17 commands the smoothing capacitor voltage Vdc while controlling the power factor of the main circuit 110 to approach 1 based on each detected value of the AC voltage vac, the smoothing capacitor voltage Vdc, and the AC current iac. A control signal D_PFC is generated to follow the value.

The current command calculator 17a calculates the current command amplitude Iac* by controlling the deviation between the smoothing capacitor voltage command Vdc* and the detected value of the smoothing capacitor voltage Vdc using proportional integral (PI) control. The current command calculator 17a multiplies the current command amplitude Iac* by a sine wave signal Sin (ωt) having the same phase as the AC voltage vac generated by phase locked loop (PLL) control to obtain an AC current command iac. Calculate *. Note that when only high power factor control of the alternating current iac is performed without voltage control of the smoothing capacitor voltage Vdc, the alternating current command iac* may be arbitrarily determined or set by the user.

The current controller 17b performs PI control on the deviation between the AC current command iac* and the AC current iac, and calculates a normalized control duty ratio D_PFC1 by dividing the control value by the DC capacitor voltage command Vsub*. The adder 17d adds the control duty ratio D_PFC1 and the FF_Duty ratio D_PFC_FF calculated by the FF_Duty calculator 17c, and outputs the added value to the adder 12a in FIG. 12 as the FF_Duty ratio D_PFC for high power factor control. do. By adding the FF_Duty ratio D_PFC_FF to the control duty ratio D_PFC1, the responsiveness of high power factor control can be improved.

In the power conversion device 100 according to the second embodiment, the control duty ratio D_PFC1 is switched depending on the operating region, so by including FF control, current fluctuations at the time of control switching can be suppressed.

The FF_Duty ratio D_PFC_FF for FF control calculates a theoretical duty ratio such that increases and decreases in the alternating current iac due to excitation and reset of the reactor 2 are equal. The method for calculating the theoretical duty ratio is described in detail in the above-mentioned Patent Document 1, so please refer to the description. The content of the description is incorporated into this specification and constitutes a part of this specification. The method for calculating the theoretical duty ratio is not limited to the content described in the publication, and any method may be used as long as it can obtain the theoretical duty ratio.

In the second embodiment, as in the first embodiment, a set of excitation and reset is selected such that the DC capacitor 4 is charged and discharged the same number of times in an AC half cycle. The FF_Duty calculator 17c calculates a theoretical duty ratio based on information regarding the selected excitation and reset combination.

FIG. 17 is a block diagram showing the detailed configuration of the gate signal generator 18 shown in FIG. 12. The gate signal generator 18 includes a comparator 18a and a pulse calculator 18b. Further, the comparator 18a includes a first comparator 18a1, a multiplier 18a2, and a second comparator 18a3.

The duty ratio sum D_total is input to the + terminal of the second comparator 18a3 via the multiplier 18a2, and the carrier wave is input to the - terminal of the second comparator 18a3. The second comparator 18a3 compares the duty ratio total amount D_total and the amplitude value of the carrier wave, and if the duty ratio total amount D_total is larger than the amplitude value of the carrier wave, an on signal that makes the switching element conductive is generated. . The pulse calculator 18b generates gate signals G3a to G3d, G5b, and G5d using the on signal and area determination signal Sig_SP output from the comparator 18a. Gate signals G3a to G3d, G5b, and G5d are applied to switching elements 3a to 3d, 5b, and 5d, respectively, and conduction of switching elements 3a to 3d, 5b, and 5d is controlled.

Note that in FIG. 17, a first comparator 18a1 and a multiplier 18a2 are provided to implement control when the number of charging and discharging operations is 0. In the configuration of FIG. 17, when the number of times of charging and discharging is 0, the output of the first comparator 18a1 is 0, and the output of the multiplier 18a2 is also 0, so the duty ratio total amount D_total input to the second comparator 18a3 also becomes 0. Note that the configuration in FIG. 17 is an example, and the configuration is not limited to these configurations. For example, a configuration may be adopted in which an on signal that makes the switching element conductive is generated when the duty ratio total amount D_total is smaller than the amplitude value of the carrier wave.

Through the above control, the power conversion device 100 of the second embodiment can supply the required power to the load 7 through control of the first capacitor voltage. Further, while controlling the first capacitor voltage, it is possible to perform voltage constant control in which the second capacitor voltage follows the command value.

Further, in the second embodiment as well, the number of times of switching in an AC half cycle is at most 20 times. Therefore, in the second embodiment, the first capacitor voltage is controlled by controlling the switching elements 3a to 3d, 5b, and 5d of the main circuit 110 by switching the number of times less than ten times in a half cycle of the AC voltage. It is possible to perform both constant voltage control that causes the second capacitor voltage to follow the command value.

As explained above, according to the power conversion device according to the second embodiment, the controller performs the following operations according to the magnitude relationship between each detected value of the first and second capacitor voltages and the detected value of the AC voltage. The operating region is determined, and switching control is performed while changing the switching frequency for each operating region based on each detected value of the first and second capacitor voltages and the detected value of the AC voltage. With this control, it is possible to increase the power factor of the main circuit operation while reducing the switching loss of the switching element and the high frequency loss of the reactor. Thereby, the power conversion device can be driven with high efficiency.

In the above control, the controller charges and discharges the second capacitor at least once each during the first switching period in which the same switching frequency is maintained, and It is preferable to perform switching control so that the number of discharges is equal within the first switching period. Thereby, voltage constant control that causes the second capacitor voltage to follow the command value can be reliably performed.

In addition, in the above control, for the total amount of duty ratio, which is the sum of the first duty ratio for controlling the first capacitor voltage and the second duty ratio for controlling the second capacitor voltage, , the controller may add or subtract the second duty ratio from the first duty ratio so that the total amount of duty ratios within the first switching period is kept constant. Thereby, control of the first capacitor voltage and constant voltage control for causing the second capacitor voltage to follow the command value can be performed simultaneously.

In addition, in the above control, the controller determines a reference value from a first phase where the AC voltage and the second capacitor voltage intersect, and a second phase where the AC voltage and the first capacitor voltage intersect, for each operating region. Calculate the switching frequency. The controller may calculate the switching frequency based on the predetermined number of charging and discharging times of the second capacitor and the calculated reference switching frequency. If this method is used, switching frequencies in a plurality of operating regions can be calculated at once, so it is possible to quickly respond to switching of operating regions.

In addition, in the above control, the controller uses a theory that the increase/decrease of the alternating current due to excitation and reset of the reactor is equal to the feedback duty ratio for controlling the second capacitor voltage within the first switching period. A duty ratio may also be added. This allows smooth switching between operating regions.

Embodiment 3.
FIG. 18 is a diagram showing a basic circuit configuration of a power conversion device 100A according to the third embodiment. In the power converter 100A according to the third embodiment, a diode bridge 24 is provided closer to the AC power supply 1 than the reactor 2 in the configuration of the power converter 100 according to the first embodiment shown in FIG. With this configuration, in FIG. 18, switching elements 3a and 3d included in sub-converter 3 of main circuit 110 are replaced with diodes 3a' and 3d', respectively. Moreover, in FIG. 18, switching element 5d included in main converter 5 of main circuit 110 is replaced with diode 5d'. Note that the other configurations are the same or equivalent to the configuration shown in FIG. 1, and the same or equivalent components are denoted by the same reference numerals and redundant explanations will be omitted.

In the case of the power conversion device 100A according to the third embodiment, a voltage waveform that has been full-wave rectified by the diode bridge 24 is applied to the sub-converter 3. Therefore, the operation of the controller 8 in the third embodiment is not a negative half-wave operation, but only a positive half-wave operation. Therefore, the functions of the controller 8 in Embodiment 1 or Embodiment 2 can be used as is. Note that the positive half-wave operation is the same as in Embodiment 1 and Embodiment 2, and therefore will not be described here.

According to the power converter device 100A according to the third embodiment, the number of switching elements can be reduced compared to the first and second embodiments, so it is possible to reduce switching loss. Furthermore, since diodes can be obtained more cheaply than switching elements, it is possible to reduce the cost of the device.

Moreover, according to the power conversion device 100A according to the third embodiment, the operation of the controller 8 is only a positive half-wave operation. Therefore, compared to the first and second embodiments, the function of the controller 8 can be simplified. This makes it possible to reduce the cost of the device.

Embodiment 4.
In Embodiment 4, an example of application of power conversion device 100 described in Embodiment 1 to a motor drive device will be described. FIG. 19 is a diagram showing a configuration example of a motor drive device 150 according to the fourth embodiment. In a motor drive device 150 according to Embodiment 4 shown in FIG. 19, an inverter 7a and a motor 7b are added to the configuration of power conversion device 100 shown in FIG.

A motor 7b is connected to the output side of the inverter 7a. The motor 7b is an example of a load device. The inverter 7a converts the DC power accumulated in the smoothing capacitor 6 into AC power, and drives the motor 7b by supplying the converted AC power to the motor 7b.

The motor drive device 150 shown in FIG. 19 can be applied to products such as blowers, compressors, and air conditioners. Note that in FIG. 19, the motor drive device 150 is configured by applying the power conversion device 100 according to the first embodiment, but the present invention is not limited thereto. Instead of the power conversion device 100 according to the first embodiment, the power conversion device 100 according to the second embodiment or the power conversion device 100A according to the third embodiment may be used.

FIG. 20 is a diagram showing an example in which the motor drive device 150 shown in FIG. 19 is applied to an air conditioner. A motor 7b is connected to the output side of the motor drive device 150, and the motor 7b is connected to the compression element 504. Compressor 505 includes a motor 7b and a compression element 504. The refrigeration cycle section 506 is configured to include a four-way valve 506a, an indoor heat exchanger 506b, an expansion valve 506c, and an outdoor heat exchanger 506d.

The flow path of the refrigerant circulating inside the air conditioner starts from the compression element 504, passes through the four-way valve 506a, the indoor heat exchanger 506b, the expansion valve 506c, the outdoor heat exchanger 506d, and again via the four-way valve 506a. , and return to the compression element 504. The motor drive device 150 receives power from the AC power supply 1 and rotates the motor 7b. The compression element 504 can compress the refrigerant and circulate the refrigerant inside the refrigeration cycle section 506 by rotating the motor 7b.

A motor drive device 150 according to the fourth embodiment includes the power conversion devices according to the first to third embodiments. As a result, the effects described in Embodiments 1 to 3 can be obtained in products such as blowers, compressors, and air conditioners to which the motor drive device according to Embodiment 4 is applied.

Note that the configuration shown in the above embodiments shows an example of the content of the present invention, and it is possible to combine it with another known technology, and the configuration can be modified without departing from the gist of the present invention. It is also possible to omit or change a part of it.

1 AC power supply, 2 Reactor, 3 Sub-converter, 3a to 3d, 5b, 5d Switching element, 3a', 3d', 5a, 5c, 5d' Diode, 4 DC capacitor, 5 Main converter, 6 Smoothing capacitor, 7 Load, 7a Inverter, 7b Motor, 8, 8A controller, 8a Processor, 8b Memory, 9 Operating region determiner, 10, 17c FF_Duty calculator, 11 DC capacitor voltage controller, 11a Preprocessor, 11b Sample hold device, 12 Addition/subtraction Judgment unit, 12a, 16h, 17d Adder, 13, 18 Gate signal generator, 16 Carrier wave generator, 17 High power factor controller, 17a Current command calculator, 17b Current controller, 18a Comparison unit, 18a1 1st Comparator, 18a2 Multiplier, 18a3 Second comparator, 18b Pulse calculator, 20 Switching frequency calculator, 20a First time calculator, 20b, 20d, 20g, 20j Divider, 20c Second time calculator, 20e third time calculator, 20i fourth time calculator, 21 frequency converter, 24 diode bridge, 30, 31, 33 voltage detector, 32 current detector, 100,100A power converter, 110 main circuit, Reference Signs List 150 motor drive device, 504 compression element, 505 compressor, 506 refrigeration cycle section, 506a four-way valve, 506b indoor heat exchanger, 506c expansion valve, 506d outdoor heat exchanger.

Claims (13)

A reactor, a main converter having a switching element, a first capacitor that holds the DC voltage converted by the main converter, a sub-converter having a switching element, and a sub-converter provided between the reactor and the first capacitor. a second capacitor that holds the DC voltage converted by the sub-converter; and a controller that controls conduction of the switching element; and the second capacitor is provided between the AC power source and the DC load,
In a power conversion device that performs power conversion between an AC voltage of the AC power supply and a first capacitor voltage that is a voltage of the first capacitor,
The sub-converter has a first leg connected in parallel to the second capacitor, and a second leg connected in parallel to the second capacitor and the first leg,
The main converter has a third leg connected in parallel to the first capacitor, and a fourth leg connected in parallel to the first capacitor and the third leg,
The midpoint of the first leg is connected to one of the AC power sources via the reactor, the midpoint of the second leg is connected to the midpoint of the third leg, and the midpoint of the fourth leg is connected to the midpoint of the fourth leg. is connected to the other of the AC power sources,
The connection polarity between the first capacitor and the second capacitor is configured to be reversible depending on the operating region,
The controller controls switching of the switching element at a switching frequency of 1 or more and 20 or less times in a half cycle of the AC voltage ,
a duty ratio summation that is the sum of a first duty ratio for controlling the first capacitor voltage and a second duty ratio for controlling the second capacitor voltage that is the voltage of the second capacitor; For the amount,
The controller adds or subtracts the second duty ratio to the first duty ratio so that the total amount of duty ratios within a half cycle of the AC voltage is kept constant.
Power converter. The controller controls a charging amount and a discharging amount of the second capacitor within a half-cycle period of the AC voltage, and adjusts the second capacitor voltage to a command value of the second capacitor voltage. The power conversion device according to claim 1, wherein control is performed to match the power conversion device. A first voltage detector that detects the first capacitor voltage, a second voltage detector that detects the second capacitor voltage, and a third voltage detector that detects the AC voltage. ,
The controller determines an operating region according to the magnitude relationship between each detected value of the first and second capacitor voltages and the detected value of the AC voltage, and determines the operating range of each of the first and second capacitor voltages. The switching control is performed while changing the charging time for charging the second capacitor and the discharging time for discharging the second capacitor based on each detected value and the detected value of the AC voltage. power converter. The controller charges and discharges the second capacitor at least once each within a half cycle of the AC voltage, and the number of times of charging and the number of times of discharging are within a half cycle of the AC voltage. The power conversion device according to claim 3, wherein the switching control is performed so that the switching is equal to each other. A reactor, a main converter having a switching element, a first capacitor that holds the DC voltage converted by the main converter, a sub-converter having a switching element, and a sub-converter provided between the reactor and the first capacitor. a second capacitor that holds the DC voltage converted by the sub-converter; a controller that controls conduction of the switching element; and a first capacitor voltage that is the voltage of the first capacitor. a second voltage detector that detects a second capacitor voltage that is the voltage of the second capacitor; and a third voltage detector that detects the AC voltage that is the voltage of the AC power supply. The reactor, the main converter, the sub-converter, the first capacitor, and the second capacitor are provided between the AC power supply and the DC load,
In a power conversion device that performs power conversion between the alternating current voltage and a first capacitor voltage that is the voltage of the first capacitor,
The sub-converter has a first leg connected in parallel to the second capacitor, and a second leg connected in parallel to the second capacitor and the first leg,
The main converter has a third leg connected in parallel to the first capacitor, and a fourth leg connected in parallel to the first capacitor and the third leg,
The midpoint of the first leg is connected to one of the AC power sources via the reactor, the midpoint of the second leg is connected to the midpoint of the third leg, and the midpoint of the fourth leg is connected to the midpoint of the fourth leg. is connected to the other of the AC power sources,
The connection polarity between the first capacitor and the second capacitor is configured to be reversible depending on the operating region,
The controller controls switching of the switching element at a switching frequency of 1 or more and 20 or less times in a half cycle of the AC voltage,
The controller determines an operating region according to the magnitude relationship between each detected value of the first and second capacitor voltages and the detected value of the AC voltage, and determines the operating range of each of the first and second capacitor voltages. The switching control is performed while changing the switching frequency for each operating region based on each detected value and the detected value of the AC voltage.
Power converter. The controller charges and discharges the second capacitor at least once each during a first switching period in which the same switching frequency is maintained, and controls the number of times of charging and the number of times of discharging. The power conversion device according to claim 5 , wherein the switching control is performed such that the values are equal within the first switching period. With respect to a total duty ratio amount that is the sum of a first duty ratio for controlling the first capacitor voltage and a second duty ratio for controlling the second capacitor voltage,
The power conversion according to claim 6 , wherein the controller adds or subtracts the second duty ratio to the first duty ratio so that the total amount of duty ratios within the first switching period is kept constant. Device. The controller performs reference switching from a first phase where the alternating current voltage and the second capacitor voltage intersect, and a second phase where the alternating current voltage and the first capacitor voltage intersect, for each of the operating regions. The power conversion device according to claim 6 or 7, wherein the switching frequency is calculated based on a predetermined number of times of charging and discharging of the second capacitor and the reference switching frequency. The controller sets a theoretical duty ratio such that an increase/decrease in alternating current due to excitation and reset of the reactor is equal to a feedback duty ratio for controlling the second capacitor voltage within the first switching period. The power conversion device according to any one of claims 6 to 8 . The power conversion device according to any one of claims 1 to 9 ,
A motor drive device comprising: an inverter that converts DC power output from the power conversion device into AC power. A blower comprising the motor drive device according to claim 10 . A compressor comprising the motor drive device according to claim 10 . An air conditioner comprising at least one of the blower according to claim 11 and the compressor according to claim 12 .

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