Power conversion devices, motor drives and refrigeration cycle application equipment

Abstract

A power conversion device (1) to be mounted to refrigeration cycle application equipment comprises: a rectifying unit (130) that rectifies first AC power supplied from a commercial power supply (110); a capacitor (210) that is connected to an output end of the rectifying unit (130); an inverter (310) that converts power outputted from the rectifying unit (130) and the capacitor (210) into second AC power and outputs the same to a motor (314); and a control unit (400) that controls the operation of the inverter (310) so as to output, from the inverter (310), the second AC power which includes pulsation corresponding to the pulsation of power flowing from the rectifying unit (130) into the capacitor (210), and that suppresses the current flowing to the capacitor (210). The power conversion device (1) operates, in a state of receiving predetermined power from the commercial power supply (110), such that the pulsation width of pulsating current due to the second AC power becomes different values depending on whether the operation of the refrigeration cycle application equipment is a cooling operation or a heating operation.

Description

[Technical field]

[0001] The present disclosure relates to a power conversion device that converts AC power into desired power, a motor drive device, and a refrigeration cycle application device. [Background technology]

[0002] Conventionally, there is a power conversion device that converts AC power supplied from an AC power source into desired AC power and supplies it to a load such as an air conditioner. For example, Patent Document 1 discloses a technology in which a power conversion device, which is a control device for an air conditioner, rectifies AC power supplied from an AC power source with a diode stack, which is a rectifier, and further smoothes the power with a smoothing capacitor, converts the power into the desired AC power with an inverter consisting of multiple switching elements, and outputs the power to a compressor motor, which is a load. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-71805 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional technology described above has a problem in that a large current flows through the smoothing capacitor, accelerating the deterioration of the smoothing capacitor over time. To address this problem, it is possible to suppress the ripple change in the capacitor voltage by increasing the capacity of the smoothing capacitor, or to use a smoothing capacitor that has a high resistance to deterioration due to ripples, but this increases the cost of the capacitor components and increases the size of the device.

[0005] The present disclosure has been made in consideration of the above, and has an object to provide a power conversion device that can suppress deterioration of a smoothing capacitor while suppressing an increase in the size of the device. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the power conversion device according to the present disclosure is a power conversion device mounted on a refrigeration cycle application device, and includes a rectifier, a capacitor connected to an output terminal of the rectifier, an inverter connected to both ends of the capacitor, and a control unit. The rectifier rectifies a first AC power supplied from an AC power source. The inverter converts the power output from the rectifier and the capacitor into a second AC power and outputs the second AC power to a load having a motor. The control unit controls the operation of the inverter so that the second AC power including pulsation corresponding to the pulsation of the power flowing from the rectifier to the capacitor is output from the inverter to the load, and suppresses the current flowing to the capacitor. In a state in which a predetermined power is received from the AC power source, the power conversion device operates so that the pulsation width of the pulsation current due to the second AC power has a different value depending on whether the operation of the refrigeration cycle application device is a cooling operation or a heating operation. Effect of the Invention

[0007] The power conversion device according to the present disclosure has an advantage in that it is possible to suppress deterioration of the smoothing capacitor while suppressing an increase in size of the device. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration example of a power conversion device according to a first embodiment; [Diagram 2] FIG. 13 is a diagram showing, as a comparative example, an example of each current and a capacitor voltage of a capacitor in a smoothing unit when the current output from the rectification unit is smoothed by the smoothing unit and the current flowing through the inverter is made constant. [Diagram 3] FIG. 13 is a diagram showing an example of each current and a capacitor voltage of a capacitor in a smoothing section when a control unit of a power conversion device according to a first embodiment controls an operation of an inverter to reduce a current flowing in a smoothing section; [Figure 4] A flowchart showing the operation of a control unit included in the power conversion device according to the first embodiment. [Diagram 5] FIG. 1 is a diagram showing an example of a hardware configuration for implementing a control unit included in a power conversion device according to a first embodiment. [Figure 6] FIG. 13 is a diagram showing a configuration example of a refrigeration cycle application device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power conversion device, a motor drive device, and a refrigeration cycle applied device according to embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0010] Embodiment 1 FIG. 1 is a diagram showing a configuration example of a power conversion device 1 according to a first embodiment. The power conversion device 1 is connected to a commercial power source 110 and a compressor 315. The commercial power source 110 is an example of an AC power source. The power conversion device 1 converts a first AC power of a power source voltage Vs supplied from the commercial power source 110 into a second AC power having a desired amplitude and phase, and supplies the second AC power to the compressor 315. The power conversion device 1 includes a voltage / current detection unit 501, a reactor 120, a rectification unit 130, a voltage detection unit 502, a smoothing unit 200, an inverter 310, current detection units 313a and 313b, a temperature detection unit 504, and a control unit 400. The power conversion device 1 and a motor 314 provided in the compressor 315 form a motor drive device 2. The power conversion device 1 is configured so as to be mountable on a refrigeration cycle application device described later.

[0011] Voltage / current detection unit 501 detects the voltage value and current value of the first AC power of power supply voltage Vs supplied from commercial power supply 110, and outputs the detected voltage value and current value to control unit 400. Reactor 120 is connected between voltage / current detection unit 501 and rectification unit 130.

[0012] The rectifier 130 has a bridge circuit constituted by rectifier elements 131 to 134, and rectifies and outputs the first AC power of the power supply voltage Vs supplied from the commercial power supply 110. The rectifier 130 performs full-wave rectification.

[0013] The voltage detection unit 502 detects the voltage value of the power rectified by the rectification unit 130 , and outputs the detected voltage value to the control unit 400 .

[0014] The smoothing unit 200 is connected to the output terminal of the rectifying unit 130 via a voltage detecting unit 502. The smoothing unit 200 has a capacitor 210 as a smoothing element, and smoothes the power rectified by the rectifying unit 130.

[0015] The capacitor 210 is, for example, an electrolytic capacitor or a film capacitor. The capacitor 210 has a capacity for smoothing the power rectified by the rectification unit 130. The voltage generated in the capacitor 210 by the smoothing is not a full-wave rectified waveform of the commercial power source 110, but a waveform in which a voltage ripple according to the frequency of the commercial power source 110 is superimposed on a DC component, and does not pulsate significantly. The frequency of this voltage ripple is twice the frequency of the power supply voltage Vs when the commercial power source 110 is single-phase, and is mainly six times the frequency when the commercial power source 110 is three-phase. When the power input from the commercial power source 110 and the power output from the inverter 310 do not change, the amplitude of the voltage ripple is determined by the capacitance of the capacitor 210. The amplitude of the voltage ripple pulsates within a range in which the maximum value of the voltage ripple generated in the capacitor 210 is less than twice the minimum value.

[0016] The inverter 310 is connected to the smoothing unit 200, i.e., both ends of the capacitor 210. The inverter 310 has switching elements 311a-311f and freewheeling diodes 312a-312f. The inverter 310 turns on and off the switching elements 311a-311f under the control of the control unit 400, converts the power output from the rectification unit 130 and the smoothing unit 200 into second AC power having a desired amplitude and phase, and outputs the second AC power to the compressor 315.

[0017] Each of the current detection units 313a and 313b detects a current value of one phase of the three-phase current output from the inverter 310, and outputs the detected current value to the control unit 400. Note that the control unit 400 can calculate the current value of the remaining one phase output from the inverter 310 by acquiring current values ​​of two phases of the three-phase current values ​​output from the inverter 310.

[0018] Temperature detection unit 504 detects the temperature of capacitor 210 or the ambient temperature of capacitor 210, and outputs the detected temperature value to control unit 400. In a typical power conversion device, a temperature detector is provided on a control board or a circuit board. Therefore, temperature detection unit 504 may not be provided and the detected value of the temperature detector provided on the board may be used instead.

[0019] Compressor 315 is a load having motor 314 for driving the compressor. Motor 314 rotates and performs a compression operation according to the amplitude and phase of the second AC power supplied from inverter 310. For example, when compressor 315 is a hermetic compressor used in an air conditioner or the like, the load torque of compressor 315 can often be regarded as a constant torque load.

[0020] In the power conversion device 1, the arrangement of each component shown in Fig. 1 is an example, and the arrangement of each component is not limited to the example shown in Fig. 1. For example, the reactor 120 may be arranged after the rectifier 130. In the following description, the voltage / current detection unit 501, the voltage detection unit 502, and the current detection units 313a and 313b may be collectively referred to as detection units. Furthermore, the voltage value and the current value detected by the voltage / current detection unit 501, the voltage value detected by the voltage detection unit 502, and the current value detected by the current detection units 313a and 313b may be referred to as detection values.

[0021] The control unit 400 obtains the voltage value and current value of the first AC power from the voltage / current detection unit 501, and obtains the voltage value of the power rectified by the rectification unit 130 from the voltage detection unit 502. The control unit 400 also obtains the current value of the second AC power having the desired amplitude and phase converted by the inverter 310 from the current detection units 313a and 313b, and obtains the temperature value of the capacitor 210 or the ambient temperature from the temperature detection unit 504. The control unit 400 uses the detection values ​​detected by each detection unit to control the operation of the inverter 310, specifically, the on / off of the switching elements 311a to 311f of the inverter 310. Note that the control unit 400 does not need to use all the detection values ​​obtained from each detection unit, and can perform control using some of the detection values.

[0022] In the first embodiment, the control unit 400 controls the current flowing through the capacitor 210 of the smoothing unit 200 by the pulsating current due to the second AC power. Specifically, the control unit 400 controls the operation of the inverter 310 so that the second AC power including the pulsation corresponding to the pulsation of the power flowing from the rectifier 130 to the capacitor 210 of the smoothing unit 200 is output from the inverter 310 to the compressor 315 which is the load. Here, the pulsation corresponding to the pulsation of the power flowing into the capacitor 210 of the smoothing unit 200 is, for example, a pulsation that varies depending on the frequency of the pulsation of the power flowing into the capacitor 210 of the smoothing unit 200. As a result, the control unit 400 suppresses the current flowing through the capacitor 210 of the smoothing unit 200.

[0023] Next, the operation of the control unit 400 included in the power conversion device 1 will be described. In the power conversion device 1 according to the first embodiment, the load generated by the inverter 310 and the compressor 315 can be regarded as a constant load. For this reason, in the power conversion device 1, the following description will be given assuming that a constant current load is connected to the smoothing unit 200 when viewed from the current output from the smoothing unit 200.

[0024] Here, as shown in FIG. 1, the current flowing from the rectifier 130 is current I1, the current flowing to the inverter 310 is current I2, and the current flowing from the smoothing unit 200 is current I3. Current I2 is a current obtained by combining current I1 and current I3. Current I3 can be expressed as the difference between current I2 and current I1, that is, current I2-current I1. The discharge direction of the smoothing unit 200 is the positive direction of current I3, and the charge direction of the smoothing unit 200 is the negative direction. That is, current may flow into or flow out of the smoothing unit 200.

[0025] FIG. 2 is a diagram showing an example of each current I1 to I3 and the capacitor voltage Vdc of the capacitor 210 of the smoothing unit 200 when the current output from the rectifying unit 130 is smoothed by the smoothing unit 200 and the current I2 flowing through the inverter 310 is kept constant, as a comparative example. From the top, the diagram shows the current I1, the current I2, the current I3, and the capacitor voltage Vdc of the capacitor 210 generated according to the current I3. The vertical axis of the currents I1, I2, and I3 indicates the current value, and the vertical axis of the capacitor voltage Vdc indicates the voltage value. The horizontal axis indicates time t. Note that the currents I2 and I3 are actually superimposed with the carrier components of the inverter 310, but are omitted here. The same applies to the following.

[0026] 2, in the power conversion device 1, if the current I1 flowing from the rectifier 130 is sufficiently smoothed by the smoothing unit 200, the current I2 flowing to the inverter 310 will have a constant current value. However, a large current I3 flows through the capacitor 210 of the smoothing unit 200, which will cause deterioration of the capacitor 210. Therefore, in the first embodiment, in the power conversion device 1, the control unit 400 controls the current I2 flowing through the inverter 310, i.e., controls the operation of the inverter 310, so as to reduce the current I3 flowing through the smoothing unit 200.

[0027] FIG. 3 is a diagram showing an example of each of the currents I1 to I3 and the capacitor voltage Vdc of the capacitor 210 of the smoothing unit 200 when the control unit 400 of the power conversion device 1 according to the first embodiment controls the operation of the inverter 310 to reduce the current I3 flowing through the smoothing unit 200. From the top, the diagram shows the current I1, the current I2, the current I3, and the capacitor voltage Vdc of the capacitor 210 generated according to the current I3. The vertical axis of the currents I1, I2, and I3 indicates the current value, and the vertical axis of the capacitor voltage Vdc indicates the voltage value. All horizontal axes indicate time t. The control unit 400 of the power conversion device 1 controls the operation of the inverter 310 so that the current I2 shown in FIG. 3 flows through the inverter 310. By this control, the current flowing from the rectification unit 130 to the smoothing unit 200 is reduced compared to the example of FIG. 2, and as a result, the current I3 flowing through the smoothing unit 200 is reduced. Specifically, the control unit 400 controls the operation of the inverter 310 so that the current I2, which includes a pulsating current whose main component is the frequency component of the current I1, flows through the inverter 310.

[0028] The frequency component of the current I1 is determined by the frequency of the AC current supplied from the commercial power source 110 and the configuration of the rectifier unit 130. Therefore, the control unit 400 can set the frequency component of the pulsating current superimposed on the current I2 to a component having a predetermined amplitude and phase. The frequency component of the pulsating current superimposed on the current I2 has a waveform similar to that of the frequency component of the current I1. As the control unit 400 brings the frequency component of the pulsating current superimposed on the current I2 closer to the frequency component of the current I1, it is possible to reduce the current I3 flowing through the smoothing unit 200 and reduce the pulsating voltage generated in the capacitor voltage Vdc.

[0029] Controlling the pulsation of the current flowing through the inverter 310 by the control unit 400 controlling the operation of the inverter 310 is equivalent to controlling the pulsation current due to the second AC power output from the inverter 310 to the compressor 315. The control unit 400 controls the operation of the inverter 310 so that the pulsation current due to the second AC power output from the inverter 310 has a smaller pulsation amount, i.e., a smaller pulsation width of the pulsation current, than the pulsation current due to the power output from the rectifier unit 130.

[0030] The control unit 400 controls the pulsation width of the pulsation current due to the second AC power output from the inverter 310 so that the pulsation of the current flowing in and out of the capacitor 210 is smaller than the pulsation of the current generated in the capacitor 210 when the second AC power output from the inverter 310 does not contain pulsation corresponding to the pulsation of the power flowing into the capacitor 210. Alternatively, the control unit 400 controls the pulsation width of the pulsation current due to the second AC power output from the inverter 310 so that the pulsation of the voltage of the capacitor voltage Vdc, i.e., the pulsation of the voltage generated in the capacitor 210, is smaller than the pulsation of the voltage generated in the capacitor 210 when the second AC power output from the inverter 310 does not contain pulsation power corresponding to the pulsation of the power flowing into the capacitor 210. Note that when the second AC power output from the inverter 310 does not contain pulsation corresponding to the pulsation of the power flowing into the capacitor 210, it refers to the control as shown in FIG. 2. The pulsation width is the difference between the maximum value and the minimum value of the pulsation current.

[0031] The above-mentioned control is called "power supply pulsation compensation control." That is, power supply pulsation compensation control is control that suppresses ripple current that may flow to capacitor 210 of smoothing unit 200 due to power supply pulsation. According to power supply pulsation compensation control, most of the ripple current caused by power supply pulsation is supplied to the load by bypassing capacitor 210. Therefore, by using power supply pulsation compensation control, it is possible to reduce stress on capacitor 210 and suppress deterioration of capacitor 210.

[0032] The AC current supplied from the commercial power source 110 is not particularly limited, and may be single-phase or three-phase. The control unit 400 may determine the frequency component of the pulsating current superimposed on the current I2 according to the first AC power supplied from the commercial power source 110. Specifically, the control unit 400 controls the pulsating waveform of the current I2 flowing through the inverter 310 to a shape obtained by adding a DC component to a pulsating waveform having a main component of a frequency component twice the frequency of the first AC power when the first AC power supplied from the commercial power source 110 is single-phase, or a frequency component six times the frequency of the first AC power when the first AC power supplied from the commercial power source 110 is three-phase. The pulsating waveform is, for example, a shape of the absolute value of a sine wave or a shape of a sine wave. In this case, the control unit 400 may add at least one frequency component of the components that are integer multiples of the frequency of the sine wave to the pulsating waveform as a predefined amplitude. The pulsating waveform may be a rectangular wave or a triangular wave. In this case, the control unit 400 may set the amplitude and phase of the pulsating waveform to predetermined values.

[0033] The control unit 400 may calculate the amount of pulsation of the pulsation current due to the second AC power output from the inverter 310 using the voltage applied to the capacitor 210 or the current flowing through the capacitor 210, or may calculate the amount of pulsation of the pulsation current due to the second AC power output from the inverter 310 using the voltage or current of the first AC power supplied from the commercial power source 110.

[0034] Next, the operation of the control unit 400 in the case where the power conversion device 1 is mounted on a refrigeration cycle application device will be described with reference to a flowchart. Fig. 4 is a flowchart showing the operation of the control unit 400 included in the power conversion device 1 according to the first embodiment.

[0035] The control unit 400 acquires required detection values ​​from each detection unit of the power conversion device 1 (step S11). The control unit 400 checks whether the operation of the refrigeration cycle application device is cooling operation or heating operation (step S12). The control unit 400 appropriately controls the pulsation width of the pulsation current by the second AC power depending on whether the operation is cooling operation or heating operation (step S13).

[0036] Note that the flowchart in Fig. 4 includes various operation modes. First, a first operation mode in the first embodiment will be described. The first operation mode is an operation mode in which the pulsation width of the pulsation current due to the second AC power has different values ​​depending on whether the operation of the refrigeration cycle application equipment is a cooling operation or a heating operation in a state in which a predetermined power is received from the commercial power source 110. Note that in this paper, operating the heat pump device of the refrigeration cycle application equipment in the cooling cycle is referred to as a "cooling operation", and operating the heat pump device of the refrigeration cycle application equipment in the heating cycle is referred to as a "heating operation".

[0037] For example, it is possible to control the operation of the inverter 310 so that the pulsation width of the pulsation current due to the second AC power output from the inverter 310 to the motor 314 is larger during cooling operation than during heating operation. In general, the ambient temperature of the refrigeration cycle application device is higher during cooling operation, and the life deterioration of the capacitor 210 is accelerated. Therefore, if the pulsation width of the pulsation current is controlled to be larger during cooling operation than during heating operation, or conversely, if the pulsation width of the pulsation current is controlled to be smaller during heating operation than during cooling operation, the power supply pulsation compensation control can be made more effective during cooling operation when the outside air temperature is high. As a result, the capacitor current can be effectively reduced under cooling conditions with a severe temperature environment, and self-heating of the capacitor 210 can be suppressed. This makes it possible to apply the capacitor 210 with a low heat-resistant temperature.

[0038] Also, for example, it is conceivable to control the operation of the inverter 310 so that the pulsation width of the pulsation current due to the second AC power output from the inverter 310 to the motor 314 is larger during heating operation than during cooling operation. When the refrigeration cycle application device is an air conditioner, in cold regions, the air conditioner may be operated for heating at an extremely low temperature. An extremely low temperature is, for example, -20°C or lower. It is generally known that the capacitance of a capacitor decreases with a decrease in temperature. If the capacitance of the capacitor 210 decreases significantly, it becomes difficult to perform air conditioning operation stably. Therefore, the pulsation width of the pulsation current is controlled to be larger during heating operation than during cooling operation. With this control, the condenser 210 can be heated during heating operation when the outside air temperature is low. As a result, even if the refrigeration cycle application device is placed in an extremely low temperature environment, it becomes possible to stably operate the refrigeration cycle application device.

[0039] According to the first operation mode described above, since the operation conditions can be set according to the operation requirements of the refrigeration cycle application equipment, it is possible to realize an appropriate protection operation of the condenser 210. According to the first operation mode, the pulsation width of the pulsation current due to the second AC power may become zero in at least one of the cooling operation and the heating operation in a state where a predetermined power is received from the commercial power source 110. According to the first operation mode, the pulsation width of the pulsation current due to the second AC power may not be zero in both the cooling operation and the heating operation in a state where a predetermined power is received from the commercial power source 110. The control according to the first operation mode may be useful or not useful depending on the function of the product, the place where the product is used, or the cost-effectiveness. For this reason, it is desirable to determine whether or not to adopt the control according to the first operation mode, taking into consideration the function of the product, the place where the product is used, or the cost-effectiveness.

[0040] Next, a second operation mode in the first embodiment will be described. In the second operation mode, when the operation of the refrigeration cycle application device is a heating operation, if the temperature of the condenser 210 or the ambient temperature is equal to or lower than a threshold value, the pulsation width of the pulsation current by the second AC power is increased or the phase of the pulsation current is changed to heat the condenser 210. For example, when the refrigeration cycle application device is an air conditioner, if the above-mentioned power supply pulsation compensation control is performed in the same manner as the cooling operation performed when the ambient temperature is high, both when the ambient temperature is low and when the ambient temperature is high, there is a problem that the heating of the condenser 210 is not sufficiently promoted during the heating operation performed when the ambient temperature is low. Therefore, when the temperature of the condenser 210 or the ambient temperature of the condenser 210 is equal to or lower than a threshold value, the pulsation width of the pulsation current by the second AC power is increased or the phase of the pulsation current is changed to actively heat the condenser 210. This control promotes the generation of heat in the condenser 210. As a result, even when the refrigeration cycle device is placed in an extremely low temperature environment, the refrigeration cycle device can be operated stably.

[0041] The phase of the pulsating current when heating the capacitor 210 by changing the phase of the pulsating current can be made the opposite phase to the phase of the pulsating current when suppressing the pulsation of the current flowing through the capacitor 210. The opposite phase means that the phase of the pulsating current is inverted by 180°. By using such a method, it is possible to easily and quickly switch between the power supply pulsation compensation control for the capacitor 210 and the heating control of the capacitor 210.

[0042] Next, a third operation mode in the first embodiment will be described. The third operation mode is an operation mode in which, when the temperature or the ambient temperature of the capacitor 210 is equal to or higher than the first threshold, the pulsation width of the pulsation current due to the second AC power is reduced so as to reduce the heat generation of the capacitor 210, and, when the temperature or the ambient temperature of the capacitor 210 is equal to or lower than the second threshold which is smaller than the first threshold, the pulsation width of the pulsation current due to the second AC power is increased so as to promote the heat generation of the capacitor 210. Also, instead of decreasing or increasing the pulsation width of the pulsation current due to the second AC power as in the second operation mode, the phase of the pulsation current may be changed. Note that, when the temperature or the ambient temperature of the capacitor 210 is greater than the second threshold and less than the first threshold, normal power supply pulsation compensation control is performed.

[0043] According to the third operation mode, it is possible to control the temperature of the condenser 210 according to the temperature conditions. This reduces the stress on the condenser 210 and suppresses deterioration of the condenser 210, so that the refrigeration cycle application device can be operated stably.

[0044] As with the control by the first operation mode, the control by the second and third operation modes may or may not be useful depending on the product's functions, the place where the product is used, or the cost-effectiveness. For this reason, it is desirable to determine whether or not to adopt the control by the second and third operation modes, taking into consideration the product's functions, the place where the product is used, or the cost-effectiveness.

[0045] Next, a description will be given of a hardware configuration of the control unit 400 included in the power conversion device 1. Fig. 5 is a diagram illustrating an example of a hardware configuration realizing the control unit 400 included in the power conversion device 1 according to the first embodiment. The control unit 400 is realized by a processor 91 and a memory 92.

[0046] The processor 91 is a CPU (also called a Central Processing Unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). The memory 92 can be exemplified by non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory). The memory 92 is not limited to these, and may be a magnetic disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc).

[0047] As described above, the power conversion device 1 according to the first embodiment performs control to suppress the current flowing through the capacitor 210 by controlling the operation of the inverter 310 so that the second AC power including pulsation corresponding to the pulsation of the power flowing from the rectifier 130 to the capacitor 210 is output from the inverter 310 to the motor 314. This control reduces the stress on the capacitor 210 and suppresses deterioration of the capacitor 210. As a result, the capacitance of the capacitor 210 can be reduced or a capacitor 210 with a low tolerance for deterioration due to ripples can be used, thereby suppressing an increase in size of the power conversion device 1.

[0048] The power conversion device 1 operates so that the pulsation amplitude of the pulsating current by the second AC power varies depending on whether the refrigeration cycle equipment is operating in cooling mode or heating mode when receiving a predetermined power from the commercial power source 110. The refrigeration cycle equipment equipped with the power conversion device 1 operating in this manner can perform cooling mode, heating mode, and operation suitable for temperature environment conditions. This allows the refrigeration cycle equipment to operate stably.

[0049] Embodiment 2 In the second embodiment, a refrigeration cycle-applied equipment equipped with the power conversion device 1 according to the first embodiment will be described. FIG. 6 is a diagram showing a configuration example of a refrigeration cycle-applied equipment 900 according to the second embodiment. The refrigeration cycle-applied equipment 900 according to the second embodiment includes the power conversion device 1 described in the first embodiment. The refrigeration cycle-applied equipment 900 according to the second embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In FIG. 6, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0050] The refrigeration cycle device 900 includes a compressor 315 incorporating the motor 314 in the first embodiment, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, which are attached via refrigerant piping 912.

[0051] Inside the compressor 315, a compression mechanism 904 that compresses the refrigerant, and a motor 314 that operates the compression mechanism 904 are provided.

[0052] The refrigeration cycle device 900 can perform heating or cooling operation by switching the four-way valve 902. The compression mechanism 904 is driven by a motor 314 that is variably controlled in speed.

[0053] During heating operation, as indicated by the solid arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910, and returns to the compression mechanism 904.

[0054] During cooling operation, as indicated by the dashed arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, passes through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902 and returns to the compression mechanism 904.

[0055] During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant to expand it.

[0056] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and may be partially omitted or modified without departing from the spirit of the invention. The operations shown in the above embodiments are merely examples, and may be combined with the first to third operation modes, and may be combined with other known technologies without departing from the spirit of the invention. [Explanation of symbols]

[0057] 1 power conversion device, 2 motor drive device, 91 processor, 92 memory, 110 commercial power source, 120 reactor, 130 rectifier section, 131-134 rectifier elements, 200 smoothing section, 210 capacitor, 310 inverter, 311a-311f switching elements, 312a-312f reflux diodes, 313a, 313b current detection section, 314 motor, 315 compressor, 400 control section, 501 voltage / current detection section, 502 voltage detection section, 504 temperature detection section, 900 refrigeration cycle applicable equipment, 902 four-way valve, 904 compression mechanism, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping.

Claims

1. A power conversion device mounted on a refrigeration cycle application device, a rectification unit that rectifies a first AC power supplied from an AC power source; A capacitor connected to an output terminal of the rectifier unit; an inverter connected to both ends of the capacitor, converting power output from the rectifier and the capacitor into second AC power and outputting the second AC power to a load having a motor; a control unit that controls an operation of the inverter so that the second AC power including a pulsation corresponding to a pulsation of the power flowing from the rectifier to the capacitor is output from the inverter to the load, and suppresses a current flowing to the capacitor; Equipped with In a state where a predetermined power is received from the AC power source, a pulsation width of a pulsation current caused by the second AC power has a different value depending on whether the operation of the refrigeration cycle application device is a cooling operation or a heating operation. Power conversion equipment.

2. The control unit controls the operation of the inverter so that a pulsation width of a pulsation current due to the second AC power output from the inverter is smaller during a heating operation than during a cooling operation. The power conversion device according to claim 1 .

3. The control unit controls the operation of the inverter so that a pulsation width of a pulsation current due to the second AC power output from the inverter is larger during a heating operation than during a cooling operation. The power conversion device according to claim 1 .

4. When the operation of the refrigeration cycle application device is a heating operation, if the temperature of the condenser or the ambient temperature of the condenser is equal to or lower than a threshold value, the control unit increases a pulsation width of a pulsation current generated by the second AC power or changes a phase of the pulsation current to heat the condenser. The power conversion device according to claim 3 .

5. The phase of the pulsating current when the phase of the pulsating current is changed to heat the capacitor is in the opposite phase to the phase of the pulsating current when the pulsation of the current flowing through the capacitor is suppressed. The power conversion device according to claim 4.

6. The control unit is When the temperature of the capacitor or the ambient temperature of the capacitor is equal to or higher than a first threshold value, a pulsation amplitude of a pulsation current generated by the second AC power is reduced or a phase of the pulsation current is changed so as to reduce heat generation in the capacitor; When the temperature of the capacitor or the ambient temperature of the capacitor is equal to or lower than a second threshold value which is smaller than the first threshold value, a pulsation width of a pulsating current generated by the second AC power is increased or a phase of the pulsating current is changed so as to promote heat generation of the capacitor. The power conversion device according to claim 3 .

7. During at least one of a cooling operation and a heating operation in a state in which a predetermined power is received from the AC power source, a pulsation width of a pulsation current due to the second AC power is zero. The power conversion device according to claim 1 .

8. In a state in which a predetermined power is received from the AC power source, the pulsation widths of the pulsation current caused by the second AC power during both a cooling operation and a heating operation are not zero. The power conversion device according to claim 1 .

9. A motor drive device comprising the power conversion device according to any one of claims 1 to 8.

10. A refrigeration cycle device comprising the power conversion device according to any one of claims 1 to 8.

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