Power conversion device, motor drive device, and equipment for refrigeration cycle applications

Abstract

A power conversion device (1) comprises: a converter (130) that has a reactor (135), a diode (138), and a switching element (136), rectifies and boosts a first AC voltage applied from a commercial power source (110), and converts the boosted voltage into a first DC voltage; a capacitor (210) that smooths the first DC voltage into a second DC voltage; and an inverter (310) that converts the second DC voltage into a second AC voltage having desired amplitude and phase and outputs the second AC voltage to a motor (314). The capacitor (210) has capacitance that enables absorbing of first energy that is potentially received by the capacitor (210) as a result of a boosting operation performed by the converter (130) immediately after the commercial power source (110) returns from an instantaneous voltage drop.

Description

Power conversion devices, motor drive devices, and refrigeration cycle application equipment

[0001] The present disclosure relates to a power conversion device that performs power conversion, a motor drive device, and a refrigeration cycle application device.

[0002] Conventionally, there are power conversion devices that rectify AC voltage supplied from a commercial AC power source and boost it to a desired voltage. Power conversion devices connected to a commercial power source can encounter problems when the output voltage of the commercial power source temporarily disappears or drops due to momentary power outages, lightning surges, and other events. In this paper, this phenomenon, i.e., the temporary disappearance or drop in the output voltage of the commercial power source, is referred to as a "commercial power source momentary voltage drop."

[0003] An instantaneous voltage drop in a commercial power supply may resolve after, for example, 10 to 100 ms. If a boost operation is performed immediately after the instantaneous voltage drop in the commercial power supply is resolved, an excessive current may flow through a capacitor that stores DC power, exceeding its withstand voltage and potentially damaging the capacitor. To address this issue, Patent Document 1 below discloses a power conversion device that includes an energy absorbing buffer circuit, a current limiting means connected between the commercial power supply and an inductor, and a relay that shorts both ends of the current limiting means.

[0004] The power conversion device described in Patent Document 1 changes the circuit configuration by switching the relay from on to off so that a current limiting means is present in the current path from the commercial power supply to the capacitor. Then, when the momentary voltage drop is resolved and power is restored, the current limiting means suppresses the excessive current that may occur when power is restored, preventing damage to the capacitor.

[0005] International Publication No. 2022 / 009296

[0006] However, the technology of Patent Document 1 requires a buffer circuit for absorbing energy, a current limiting means, and a relay for short-circuiting both ends of the current limiting means, which poses a problem of increasing the circuit size.

[0007] The present disclosure has been made in view of the above, and has an object to provide a power conversion device that can appropriately respond to instantaneous voltage drops in commercial power sources while suppressing an increase in circuit size.

[0008] In order to solve the above-mentioned problems and achieve the object, a power conversion device according to the present disclosure includes a converter having a reactor, one or more diodes, and one or more switching elements, a capacitor connected in parallel to the converter, and an inverter connected in parallel to the capacitor. The converter rectifies and boosts a first AC voltage applied from a commercial power source to convert it into a first DC voltage. The capacitor smoothes the first DC voltage into a second DC voltage. The inverter converts the second DC voltage into a second AC voltage of a desired amplitude and phase and outputs it to a motor. The capacitor has a capacitance capable of absorbing first energy that the capacitor can accept when the converter performs a boost operation immediately after the commercial power source recovers from an instantaneous voltage drop.

[0009] The power conversion device according to the present disclosure has the advantage of being able to appropriately respond to instantaneous voltage drops in commercial power sources while suppressing an increase in circuit size.

[0010] FIG. 1 is a diagram showing a first configuration example of a power conversion device according to embodiment 1. FIG. 2 is a diagram showing a second configuration example of a power conversion device according to embodiment 1. FIG. 3 is a diagram showing a third configuration example of a power conversion device according to embodiment 1. FIG. 4 is a diagram showing a fourth configuration example of a power conversion device according to embodiment 1. FIG. 5 is a diagram showing a fifth configuration example of a power conversion device according to embodiment 1. FIG. 6 is a diagram showing a sixth configuration example of a power conversion device according to embodiment 1. FIG. is used to explain a first key point of a power conversion device according to embodiment 1. FIG. is used to explain a second key point of a power conversion device according to embodiment 1. FIG. is used to explain a third key point of a power conversion device according to embodiment 1. FIG. is used to explain a configuration example of a refrigeration cycle application device according to embodiment 2.

[0011] 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 accompanying drawings.

[0012] First Embodiment. Fig. 1 is a diagram showing a first configuration example of a power conversion device 1 according to a first embodiment. The power conversion device 1 is connected to a commercial power supply 110 and a motor 314. The power conversion device 1 converts a first AC voltage, which is a power supply voltage applied from the commercial power supply 110, into a second AC voltage having a desired amplitude and phase, and outputs the second AC voltage to the motor 314. In the example of Fig. 1, the commercial power supply 110 is a single-phase AC power supply, but it may also be a three-phase AC power supply. The power conversion device 1 includes a converter 130, a capacitor 210, an inverter 310, current detection units 501 and 502, and a control unit 400. The power conversion device 1 and the motor 314 form a motor drive device 2.

[0013] Converter 130 is a power converter that converts a first AC voltage applied from commercial power supply 110 into a DC voltage. Converter 130 includes rectifying elements 131 to 134, a reactor 135, a switching element 136, a freewheeling diode 137, and a diode 138. Converter 130 has a bridge circuit formed by rectifying elements 131 to 134, and rectifies the first AC voltage applied from commercial power supply 110 while boosting and outputting the rectified DC voltage. In the following description, the DC voltage after rectification and boosting, i.e., the DC voltage output to capacitor 210, may be referred to as the "first DC voltage."

[0014] The switching element 136 is, for example, but not limited to, an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a bipolar transistor, etc. When the switching element 136 is a MOSFET, the free wheel diode 137 can be omitted by using a parasitic diode formed inside the MOSFET.

[0015] 1 performs a boost operation using a combination of one reactor 135, one switching element 136, and one diode 138. Boost circuit 162 having such a configuration is called a "single-transistor boost circuit." Also, converter 130 shown in FIG. 1 is called a "single-transistor boost AC / DC converter."

[0016] In the example of FIG. 1 , the converter 130 includes a rectifier circuit 161, which is a bridge circuit configured with rectifier elements 131 to 134 such as diodes, and a boost circuit 162 configured with a reactor 135, a switching element 136, a freewheeling diode 137, and a diode 138. However, the configuration of the converter 130 is not limited to the example of FIG. 1 . For example, the converter 130 may be configured as shown in FIGS. 2 to 6 . FIG. 2 is a diagram illustrating a second configuration example of the power conversion device 1 according to the first embodiment. FIG. 3 is a diagram illustrating a third configuration example of the power conversion device 1 according to the first embodiment. FIG. 4 is a diagram illustrating a fourth configuration example of the power conversion device 1 according to the first embodiment. FIG. 5 is a diagram illustrating a fifth configuration example of the power conversion device 1 according to the first embodiment. FIG. 6 is a diagram illustrating a sixth configuration example of the power conversion device 1 according to the first embodiment.

[0017] In the converter 130, the reactor 135 provided in the boost circuit 162 is arranged between the rectifier circuit 161 and the diode 138 in the configuration of FIG. 1, but may be arranged between the commercial power supply 110 and the rectifier circuit 161 as shown in FIG. 2.

[0018] Furthermore, the boost circuit 162 of the converter 130 may be configured to include reactors 135a and 135b, switching elements 136a and 137a, freewheeling diodes 136b and 137b, and diodes 138a and 138b, as shown in Fig. 3. In the converter 130 shown in Fig. 1, the boost circuit 162 is a one-stage, single-transistor boost circuit, but in the converter 130 shown in Fig. 3, the boost circuit 162 is configured to be a two-stage, single-transistor boost circuit. Note that the number of stages in the boost circuit 162 may be three or more. That is, the boost circuit 162 may be configured to be multi-stage, including a plurality of single-transistor boost circuits that perform a boost operation.

[0019] 4, the converter 130 may be configured with a reactor 135, switching elements 131a and 132a, freewheeling diodes 131b and 132b, and rectifying elements 133 and 134. The converter 130 shown in FIG. 4 is configured as a rectifier boost circuit having two legs, each of which has two semiconductor elements connected in series, with the semiconductor elements of the first leg being switching elements 131a and 132a and the semiconductor elements of the second leg being rectifying elements 133 and 134. The converter 130 configured in this manner is called a "totem-pole AC-DC converter," for example.

[0020] 5, the converter 130 may be configured with a reactor 135, rectifying elements 131 and 133, switching elements 132a and 134a, and freewheeling diodes 132b and 134b. The converter 130 shown in FIG. 5 is configured as a rectifying boost circuit, in which the semiconductor elements of the upper arms in the first leg and the second leg are the rectifying elements 131 and 133, and the semiconductor elements of the lower arms are the switching elements 132a and 134a. The converter 130 configured in this manner is called a "half-bridgeless AC-DC converter," for example.

[0021] 6, the converter 130 may be composed of a reactor 135, switching elements 131a to 134a, and freewheeling diodes 131b to 134b. The converter 130 shown in FIG. 6 is configured as a rectifier boost circuit in which all semiconductor elements are switching elements 131a to 134a. The converter 130 having such a configuration is called a "full-bridgeless AC-DC converter."

[0022] As described above, converter 130 in the first embodiment may have reactor 135, one or more diodes, and one or more switching elements, and may be configured to rectify and boost the first AC voltage applied from commercial power supply 110 to convert it into a first DC voltage. Hereinafter, the power conversion device 1 shown in FIG. 1 will be described as an example.

[0023] The capacitor 210 is connected in parallel to the output terminal of the converter 130 and smoothes the first DC voltage into a second DC voltage. The capacitor 210 is, for example, an electrolytic capacitor.

[0024] The inverter 310 is a power converter connected in parallel across the capacitor 210. The inverter 310 has six switching elements 311 and six freewheeling diodes 312. The inverter 310 turns the switching elements 311 on and off under the control of the control unit 400, converts the DC voltage output from the converter 130 and the capacitor 210 into a second AC voltage having a desired amplitude and phase, i.e., generates a second AC voltage, and outputs it to the motor 314. In other words, the inverter 310 converts the second DC voltage into a second AC voltage and outputs it. The switching elements 311 are, for example, IGBTs, MOSFETs, bipolar transistors, etc., but are not limited to these. The circuit configuration of the inverter 310 is not particularly limited and may be a full-bridge circuit, a single-phase bridge circuit, a half-bridge circuit, or the like.

[0025] The current detection unit 501 detects the current flowing through the converter 130. The current detection unit 501 can detect the current flowing at the installation position using a current detection resistor or the like, but the configuration of the current detection unit 501 is not limited to this. The current detection unit 501 outputs the detection result to the control unit 400. The current detection unit 502 detects the current flowing through the motor 314. The current detection unit 502 can detect the current flowing at the installation position using a current detection resistor or the like, but the configuration of the current detection unit 502 is not limited to this. The current detection unit 502 outputs the detection result to the control unit 400. Note that the power conversion device 1 may be provided with a current detection unit that detects the current flowing at a position other than the position shown in FIG. 1 , or may be provided with a voltage detection unit that detects the voltage in a specific section.

[0026] The control unit 400 controls the on / off of the switching element 136 included in the converter 130 and the six switching elements 311 included in the inverter 310 based on the detection results of the current detection units 501 and 502, etc. Although not shown in the example of FIG. 1 , the control unit 400 may also control the on / off of the switching element 136 included in the converter 130 and the six switching elements 311 included in the inverter 310 using the detection results from a voltage detection unit that detects the voltage across the capacitor 210, i.e., the DC bus voltage which is the second DC voltage. In the first embodiment, the operation of the control unit 400 to control the converter 130 and the inverter 310 is a general operation, and therefore a detailed description thereof will be omitted.

[0027] The motor 314 is a load connected to the power conversion device 1 and is connected to the inverter 310. The motor 314 is, for example, a compressor motor for driving a compressor. The motor 314 rotates in accordance with the amplitude and phase of the second AC voltage supplied from the inverter 310 to perform a compression operation. For example, when the compressor is a hermetic compressor, the load torque of the motor 314 that drives the compressor can often be considered a constant torque load. The motor 314 may have a Y-connection or a Δ-connection with respect to the motor windings (not shown), or may be configured to be switchable between the Y-connection and the Δ-connection. Furthermore, the load connected to the inverter 310 is not limited to the motor 314 for driving a compressor, but may also be a fan motor or the like.

[0028] Next, a description will be given of the main points of the operation of the power conversion device 1 according to embodiment 1. Fig. 7 is a diagram used to describe the first main point of the power conversion device 1 according to embodiment 1. Fig. 7 shows the commercial power supply 110, the converter 130, and the capacitor 210 extracted from Fig. 1.

[0029] As described above, in the operation of the power conversion device 1, an instantaneous voltage drop of the commercial power supply, in which the output voltage of the commercial power supply 110 temporarily disappears or drops, becomes a problem. ２" is the energy that can be supplied from the commercial power supply 110 by the boost operation performed by the converter 130 immediately after the commercial power supply 110 recovers from the momentary voltage drop. In this paper, this energy is called "second energy." Also, "E ３ " is the energy that can be stored in the reactor 135 just before the boost operation is performed. In this paper, this energy is referred to as the "third energy."

[0030] These second and third energies E ２ , E ３ is energy that can be generated by the boost operation performed by converter 130. Since instantaneous voltage drops in the commercial power supply often resolve after, for example, 10 to 100 ms, it is difficult to stop the boost operation during operation, and this energy can flow to capacitor 210. In Patent Document 1, this energy is configured to be received by an energy absorption buffer circuit. On the other hand, power conversion device 1 according to embodiment 1 is configured to be able to receive this energy without using a special circuit such as an energy absorption buffer circuit.

[0031] Specifically, in the power conversion device 1 according to the first embodiment, the capacitor 210 receives the second and third energies E ２ , E ３ In this paper, the energy that the capacitor 210 can receive is called the "first energy" and the "E １ At this time, the capacitor 210 stores the second and third energies E ２ , E ３ The condition for accepting is expressed by the following equation (1).

[0032] E １ >E ２ +E ３ …(1)

[0033] The second energy E in the above formula (1) ２ can be expressed by the following equation (2).

[0034] E ２ = (1 / 2) CVｐｅａｋ ２ …(2)

[0035] In the above equation (2), "C" is the capacitance of the capacitor 210, and "V ｐｅａｋ ″ is the peak value of the voltage applied across capacitor 210 when commercial power supply 110 recovers from the momentary voltage drop.

[0036] In addition, the third energy E in the above formula (1) ３ can be expressed by the following equation (3).

[0037] E ３ = (1 / 2) LI Ｌ ２ …(3)

[0038] In the above formula (3), "L" is the inductance of the reactor 135, and "I Ｌ ″ is the peak value of the current flowing through the reactor 135 immediately before an instantaneous voltage drop occurs in the commercial power supply 110.

[0039] Also, the first energy E that the capacitor 210 can accept is １ can be expressed by the following equation (4).

[0040] E １ = (1 / 2) C(V ｄｃｍａｘ ２ -V ｐｅａｋ ２ ) … (4)

[0041] In the above formula (4), "V ｄｃｍａｘ " is the withstand voltage of the capacitor 210 or a derating value obtained by multiplying the withstand voltage of the capacitor 210 by a derating coefficient.

[0042] Fig. 8 is a diagram illustrating a second key point of the power conversion device 1 according to embodiment 1. Fig. 8 shows the commercial power supply 110, the converter 130, and the capacitor 210 extracted from Fig. 1 .

[0043] The arrows in the figure indicate the direction of the voltage drop, i.e., the polarity of the voltage drop. Specifically, when the tip of the arrow points to the high potential side, the polarity of the voltage drop is positive, and the value of the voltage drop is positive. Also, when the tip of the arrow points to the low potential side, the polarity of the voltage drop is negative, and the value of the voltage drop is negative. In the above equation (1), the acceptance condition of capacitor 210 during an instantaneous voltage drop of the commercial power supply is expressed in terms of energy, but it can also be expressed in terms of the voltage drop, as in the following equation (5).

[0044] V ｐｅａｋ -V Ｌ -V Ｆ <V ｄｃｍａｘ …(5)

[0045] In the above formula (5), "V Ｌ ” is a back electromotive voltage generated in the reactor 135 when the commercial power supply 110 recovers from an instantaneous voltage drop. Ｌ is the current i flowing from the commercial power supply 110 when the commercial power supply 110 recovers from a momentary voltage drop. ｓ This is a voltage that is generated in a direction that prevents the voltage from reaching the ground, and can be expressed by the following equation (6).

[0046] V Ｌ = -L(di ｓ / dt) ... (6)

[0047] In addition, in the above formula (5), "V Ｆ " is the total value of the forward voltage drop due to at least one diode present on the charging path of capacitor 210 when commercial power supply 110 recovers from an instantaneous voltage drop. In the example of FIG. 8, rectifier element 133, diode 138, and rectifier element 132 are present on the charging path of capacitor 210 in the order in which the charging current that charges capacitor 210 flows. The forward voltage drop of each is expressed as "V Ｆ１ ", "V Ｆ２ " and "V Ｆ３ ", the total forward voltage drop V Ｆ can be expressed by the following equation (7).

[0048] V Ｆ =V Ｆ１ +V Ｆ２ +V Ｆ３ …(7)

[0049] Fig. 9 is a diagram illustrating a third key point of the power conversion device 1 according to embodiment 1. Fig. 9 illustrates an example of how the circuit components of the converter 130 and the capacitor 210 constituting the power conversion device 1 are mounted on the substrate 250.

[0050] 9 is a plan view, and dashed lines indicate the approximate mounting areas of the relevant circuit components. As shown in the figure, a capacitor 210, a reactor 135, a rectifier circuit module 252, a booster switch module 254, and a booster diode module 256 are mounted on a substrate 250. The rectifier circuit module 252 has the rectifier elements 131 to 134 shown in FIG. 1, the booster switch module 254 has the switching element 136 and the freewheeling diode 137 shown in FIG. 1, and the booster diode module 256 has the diode 138 shown in FIG. 1.

[0051] 9 , the reactor 135 included in the power conversion device 1 according to the first embodiment is configured so as to be mountable on the same substrate 250 as the circuit components of the converter 130 and the capacitor 210 that smooths the DC voltage. In this document, the reactor 135 configured in this manner is referred to as an “on-board reactor.”

[0052] When the application example of the power conversion device 1 is an air conditioner, the substrate 250 has a size of approximately 20 to 30 cm square. In such a substrate 250, in order to use the reactor 135 as an on-board reactor while taking into consideration the occupied area and weight, the inductance L of the reactor 135 needs to be configured to satisfy the following formula (8).

[0053] L<L ｏｎｂｏａｒｄ …(8)

[0054] In the above formula (8), L ｏｎｂｏａｒｄis, for example, 1 mH. If the inductance L of the reactor 135 is configured to satisfy the above formula (8), when the power conversion device 1 according to the first embodiment is mounted in, for example, an air conditioner, it can be mounted on the same board as the circuit components of the converter 130 and the capacitor 210 that smooths the DC voltage.

[0055] The conditions expressed by the above formulas (1), (5), and (8) can be applied as they are to a power conversion device 1 having a single reactor 135, as shown in Figures 1, 2, and 4 to 6. On the other hand, in the case of a power conversion device 1 having a multi-stage configuration including multiple single-transistor step-up circuits, as shown in Figure 3, it is necessary to consider the total inductance of the entire reactor 135. In the case of the power conversion device 1 of Figure 3, two reactors 135a and 135b are provided, so the sum of the inductance of reactor 135a and the inductance of reactor 135b can be treated as the total inductance. By introducing this concept of total inductance, the conditions expressed by the above formulas (1), (5), and (8) can be applied as they are.

[0056] As described above, the power conversion device according to the first embodiment includes a converter having a reactor, one or more diodes, and one or more switching elements; a capacitor connected in parallel to the converter; and an inverter connected in parallel to the capacitor. The converter rectifies and boosts a first AC voltage applied from a commercial power source to convert it into a first DC voltage. The capacitor smoothes the first DC voltage into a second DC voltage. The inverter converts the second DC voltage into a second AC voltage of a desired amplitude and phase and outputs the second AC voltage to a motor. The capacitor has a capacitance capable of absorbing first energy that can be absorbed by the converter when the converter performs a boost operation immediately after the commercial power source recovers from an instantaneous voltage drop. With this power conversion device configured in this manner, the capacitor can absorb excessive current that may occur when the commercial power source is restored and excessive energy that may be generated by the converter's boost operation when the commercial power source is restored, without using a special circuit such as an energy absorption buffer circuit. This makes it possible to obtain a power conversion device that can appropriately respond to instantaneous voltage drops in the commercial power source while suppressing an increase in circuit size.

[0057] In the power conversion device according to the first embodiment, the first energy that can be received by the capacitor is greater than the sum of the second energy that can be supplied from the commercial power supply by the boost operation performed by the converter immediately after the commercial power supply recovers from an instantaneous voltage drop, and the third energy that can be stored in the reactor immediately before the boost operation is performed.

[0058] Furthermore, the power conversion device according to the first embodiment is a (1 / 2)CV ｐｅａｋ ２ +(1 / 2)LI Ｌ ２ <(1 / 2)C(V ｄｃｍａｘ ２ -V ｐｅａｋ ２ ) relationship is satisfied. ｐｅａｋ is the peak value of the voltage applied across the capacitor when the commercial power supply recovers from a momentary voltage drop, and I Ｌ is the peak value of the current flowing through the reactor just before an instantaneous voltage drop occurs in the commercial power supply.ｄｃｍａｘ is the withstand voltage of the capacitor or the derating value obtained by multiplying the withstand voltage by the derating coefficient. Also, L is the inductance of the reactor, and C is the capacitance of the capacitor.

[0059] In addition, the power conversion device according to the first embodiment is V ｐｅａｋ -V Ｌ -V Ｆ <V ｄｃｍａｘ The operation is performed so that the relationship between V and V is satisfied. ｐｅａｋ As mentioned above, V is the peak value of the voltage applied to both ends of the capacitor when the commercial power supply recovers from a momentary voltage drop. ｄｃｍａｘ As mentioned above, V is the withstand voltage of the capacitor or the derating value obtained by multiplying the withstand voltage by the derating coefficient. Ｌ is the back electromotive force generated in the reactor when the commercial power supply recovers from a momentary voltage drop, and V Ｆ is the total value of the forward voltage drop due to at least one diode present on the charging path of the capacitor.

[0060] In the power conversion device according to the first embodiment, the reactor included in the converter is configured as an on-board reactor that can be mounted on the same board together with the converter's circuit components and capacitor. The on-board reactor has an inductance of 1 mH or less. If the reactor included in the converter has an inductance of 1 mH or less, it can be mounted on the same board together with the converter's circuit components and capacitor, and can be configured as an on-board reactor. Furthermore, if the inductance of the reactor included in the converter is limited to 1 mH or less, the capacitor can absorb the excessive current and excessive energy described above.

[0061] In the power conversion device according to embodiment 1, when the converter is configured in multiple stages by including a plurality of single-transistor step-up type boost circuits, the total inductance of the reactors in the multiple stages is configured to match the inductance of the reactor when the converter is in a single stage. If the power conversion device is configured in this way, the above-mentioned conditions can be applied as is even when the single-transistor step-up type boost circuits are configured in multiple stages.

[0062] Second Embodiment Fig. 10 is a diagram showing a configuration example of a refrigeration cycle-applied apparatus 900 according to a second embodiment. The refrigeration cycle-applied apparatus 900 according to the second embodiment includes the power conversion device 1 described in the first embodiment. The refrigeration cycle-applied apparatus 900 according to the second embodiment may also include the power conversion device 1 shown in Figs. 2 to 6. The refrigeration cycle-applied apparatus 900 according to the second embodiment may be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In Fig. 10, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0063] The refrigeration cycle application equipment 900 includes a compressor 315 incorporating the motor 314 in embodiment 1, 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.

[0064] Inside the compressor 315, a compression mechanism 904 that compresses the refrigerant and a motor 314 that operates the compression mechanism 904 are provided.

[0065] 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.

[0066] During heating operation, as shown 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 the four-way valve 902 and returns to the compression mechanism 904.

[0067] During cooling operation, as shown by the dashed arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, and returns to the compression mechanism 904 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.

[0068] 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.

[0069] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention.

[0070] 1 Power conversion device, 2 Motor drive device, 110 Commercial power supply, 130 Converter, 131 to 134 Rectifier elements, 131a to 134a, 136, 136a, 137a, 311 Switching elements, 131b to 134b, 137, 136b, 137b, 312 Freewheeling diodes, 135, 135a, 135b Reactors, 138, 138a, 138b Diodes, 161 Rectifier circuit, 162 Boost circuit, 210 Capacitor, 250 Substrate, 252 Rectifier circuit module, 254 Boost switch module, 256 Boost diode module, 310 Inverter, 314 Motor, 315 Compressor, 400 Control unit, 501, 502 Current detection unit, 900 Refrigeration cycle application 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 converter including a reactor, one or more diodes, and one or more switching elements, which rectifies and boosts a first AC voltage applied from a commercial power source to convert it into a first DC voltage; a capacitor connected in parallel with the converter to smooth the first DC voltage into a second DC voltage; an inverter connected in parallel to the capacitor, which converts the second DC voltage into a second AC voltage of a desired amplitude and phase and outputs the second AC voltage to a motor; Equipped with The capacitor has a capacitance capable of absorbing a first energy that the capacitor can receive when the converter performs a boost operation immediately after the commercial power supply recovers from a momentary voltage drop. Power conversion device.

2. The first energy is greater than the sum of a second energy that can be supplied from the commercial power supply by a voltage boosting operation performed by the converter immediately after the commercial power supply recovers from an instantaneous voltage drop, and a third energy that can be stored in the reactor immediately before the voltage boosting operation is performed. The power conversion device according to claim 1 .

3. When the commercial power supply recovers from a momentary voltage drop, the peak value of the voltage applied across the capacitor is V ｐｅａｋ year, The peak value of the current flowing through the reactor immediately before an instantaneous voltage drop occurs in the commercial power supply is I Ｌ year, The withstand voltage of the capacitor or the derating value obtained by multiplying the withstand voltage by a derating coefficient is V ｄｃｍａｘ year, When the inductance of the reactor is L and the capacitance of the capacitor is C, These V ｐｅａｋ , I Ｌ , V ｄｃｍａｘ , L and C are (1 / 2) CV ｐｅａｋ ２ + (1 / 2)LI Ｌ ２ <(1 / 2)C(V) ｄｃｍａｘ ２ -V ｐｅａｋ ２ ) Satisfying the relationship The power conversion device according to claim 2 .

4. When the commercial power supply recovers from a momentary voltage drop, the counter electromotive force generated in the reactor is V Ｌ and the total amount of forward voltage drop due to at least one of the diodes present on the charging path of the capacitor is V Ｆ When these V Ｌ , V Ｆ , and the V ｐｅａｋ , V ｄｃｍａｘ teeth, V ｐｅａｋ -V Ｌ -V Ｆ <V ｄｃｍａｘ Satisfying the relationship The power conversion device according to claim 3 .

5. the reactor is an on-board reactor that can be mounted on the same board together with the circuit components of the converter and the capacitor, The inductance of the on-board reactor is 1 mH or less. The power conversion device according to claim 3 .

6. the converter is configured to have a single-transistor boost circuit in which a boost operation is performed by a combination of one reactor, one switching element, and one diode; When the converter is configured in multiple stages by including a plurality of the single-transistor step-up type boost circuits, the total inductance of the reactor in the multiple stages is equal to the inductance of the reactor when the converter is in a single stage. The power conversion device according to claim 3 .

7. A motor drive device comprising the power conversion device according to any one of claims 1 to 6.

8. A refrigeration cycle device comprising the power conversion device according to any one of claims 1 to 6.