Power conversion device and heat pump device

Abstract

To provide a power conversion device and heat pump device capable of heating a compressor by applying voltage corresponding to a compressor motor.SOLUTION: The power conversion device includes an inverter circuit that supplies power by applying a voltage corresponding to the frequency related to AC conversion to compressor motors of two or more compressors that compress refrigerant, a motor power detection unit that detects the power supplied by the inverter circuit to each compressor motor, and an inverter control unit that, in a heating mode in which the compressor motor is not operated and the compressor is heated, determines an output voltage command value on the basis of the power detected by the motor power detection unit, and generates a drive signal on the basis of the determined output voltage command value to drive the inverter circuit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device and a heat pump device including the power conversion device, and more particularly to a power conversion device that supplies power to a plurality of motors. [Background technology]

[0002] To extend the life of a heat pump device, it is necessary to suppress liquefaction of the refrigerant inside the compressor. Therefore, the refrigerant is preheated in the compressor. In order to achieve highly efficient heating, some systems apply a high-frequency voltage to the compressor motor of the compressor when the compressor is stopped to heat the compressor (see, for example, Patent Document 1). An inverter circuit applies a high-frequency AC voltage to the compressor motor just enough to prevent the compressor motor's rotating shaft from rotating, causing the compressor motor to generate heat through induction heating, thereby heating the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2013 / 157074 Summary of the Invention [Problem to be solved by the invention]

[0004] When applying a high-frequency voltage to a compressor motor to heat the compressor, conventionally, a voltage based on a preset output voltage command value is applied to the compressor motor to supply power. However, in reality, the impedance of a compressor motor varies depending on the axial position of the rotor of a stopped compressor motor. Therefore, even if a voltage based on the same output voltage command value is applied to the compressor motor, the power supplied may vary depending on the axial position of the compressor motor.

[0005] In particular, when heating the compressors by applying a high-frequency AC voltage to multiple compressor motors connected in parallel to an inverter circuit, if the impedance of the compressor motor in each compressor differs, it is difficult to supply the power required to heat the compressor to each compressor motor using only the set output voltage command value.

[0006] Therefore, an object of the present disclosure is to provide a power conversion device and a heat pump device that can heat a compressor by applying a voltage according to a compressor motor. [Means for solving the problem]

[0007] In order to solve the above problems, the power conversion device according to the present disclosure includes an inverter circuit that applies a voltage corresponding to a frequency related to AC conversion to the compressor motors of each of two or more compressors that compress a refrigerant, thereby supplying power; a motor power detection unit that detects the power supplied by the inverter circuit to each compressor motor; and an inverter control unit that, in a heating mode in which the compressor motors are not operating but the compressors are heated, determines an output voltage command value based on the power value detected by the motor power detection unit, and generates a drive signal based on the determined output voltage command value to drive the inverter circuit.

[0008] In addition, the heat pump device according to the present disclosure has a heat pump circuit in which two or more compressors, a condenser, a pressure reducing device, and an evaporator are connected by refrigerant piping, and is equipped with the above-mentioned power conversion device that controls the drive of each compressor motor. [Effects of the Invention]

[0009] According to the present disclosure, an output voltage command value is determined based on the power supplied to the compressor motors of two or more compressors, and power is supplied based on the determination to heat the compressors without rotating or moving the compressor motors. This allows power to be supplied according to the state of the compressor motors. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing a configuration of a system centered around a power conversion device 10 according to a first embodiment. [Figure 2] FIG. 4 is a flowchart showing a heating mode determination process when restraint current supply is started according to the first embodiment. [Figure 3] FIG. 4 is a flowchart showing an output voltage command value determination process in a multiple compressor heating mode according to the first embodiment. [Figure 4] FIG. 5 is a diagram showing a flowchart of an output voltage command value determination process in a single-compressor heating mode according to the first embodiment. [Figure 5] FIG. 10 is a diagram showing the configuration of an air conditioning system 1 according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, power conversion devices and heat pump devices according to embodiments will be described with reference to the drawings. In the following drawings, components with the same reference numerals are identical or equivalent and will be common throughout the following embodiments. The configurations of components shown throughout the specification are merely examples and are not limited to the configurations described in the specification. In particular, the combinations of components are not limited to the combinations in each embodiment, and components described in other embodiments may be applied to other embodiments. Furthermore, the levels of pressure and temperature are not determined in relation to absolute values, but are determined relatively in terms of the state, operation, etc. of the device. Furthermore, when multiple similar devices are distinguished by subscripts, the subscripts may be omitted if there is no need to distinguish or identify them. The size relationships between components in the drawings may differ from those in reality.

[0012] Embodiment 1 FIG. 1 is a diagram showing the configuration of a system centered around a power conversion device 10 according to a first embodiment. The system according to the first embodiment is an air conditioning system in which the power conversion device 10 converts power sent from a three-phase AC power source 0 and supplies the converted power to a compressor motor 111 of a compressor 110 included in a heat pump device (not shown) that is the power supply target, thereby driving the compressor motor 111. Here, as shown in FIG. 1, the power conversion device 10 drives a plurality of compressor motors 111a and 111b that are connected in parallel to the power conversion device 10. The compressor motor 111a is a component included in the compressor 110a. The compressor motor 111b is a component included in the compressor 110b. Here, the compressor motor 111 is a three-phase AC electric motor.

[0013] The switch 112 controls the connection of a power supply path from the inverter unit 30 of the power conversion device 10 (described later) to the compressor motor 111, based on, for example, an instruction signal from a control device (not shown) that controls a heat pump device (not shown). The switch 112 is, for example, a relay switch. For example, when the switch 112 is on, the switch 112 electrically connects the path and supplies power from the inverter unit 30 to the compressor motor 111, and when the switch 112 is off, the switch 112 interrupts the path and stops the power supply from the inverter unit 30 to the compressor motor 111. The system of the first embodiment has a switch 112a and a switch 112b corresponding to each compressor motor 111. Therefore, it is possible to switch the power supply to one compressor motor 111 or both compressor motors 111.

[0014] The power conversion device 10 according to the first embodiment includes a rectifier unit 20, an inverter unit 30, an inverter control unit 40, and a motor power detection unit 50. The compressor motor 111 is electrically connected to the inverter unit 30 via a switch 112.

[0015] The rectifier unit 20 is a circuit that converts AC power from a three-phase AC power source 0 into DC power. The rectifier unit 20 has, for example, a three-phase rectifier. The three-phase rectifier is, for example, a bridge-connected three-phase rectifier using six rectifier backflow prevention elements such as diodes. However, the rectifier unit 20 is not limited to this configuration. For example, the rectifier unit 20 may be a PWM (Pulse Width Modulation) converter having semiconductor switching elements.

[0016] The inverter unit 30 also has an inverter circuit that converts the DC voltage converted by the rectifier unit 20 into AC voltage at a desired drive frequency and supplies the AC power to the compressor motor 111. The inverter unit 30 has semiconductor elements that constitute the inverter circuit. The semiconductor elements are, for example, switching elements 31 such as IGBTs, MOSFETs, and HEMTs, and backflow prevention elements 32, which are diodes. The inverter unit 30 also has arms, each paired with two switching elements 31 and two backflow prevention elements 32. If the inverter unit 30 is a three-phase output inverter as in the first embodiment, the inverter unit 30 has three pairs of arms, one for each phase. The switching elements 31 of each arm are controlled by the inverter control unit 40, which performs a switching operation of turning them on or off at predetermined timing, thereby controlling the path of the current flowing through the compressor motor 111.

[0017] Here, we will explain the materials constituting the switching element 31 and the backflow prevention element 32. The switching element 31 and the backflow prevention element 32 are generally made of semiconductors based on silicon (Si). In this example, the inverter unit 30 uses wide-bandgap semiconductors, typically silicon carbide (SiC), gallium nitride (GaN), or diamond, as the substrate material for the switching element 31 and the backflow prevention element 32. The switching element 31 and the backflow prevention element 32 made of wide-bandgap semiconductors have high voltage resistance and allowable current, allowing for miniaturization of the elements. This allows for miniaturization of semiconductor modules incorporating the miniaturized switching element 31 and the backflow prevention element 32. Furthermore, the switching element 31 and the backflow prevention element 32 made of wide-bandgap semiconductors have high heat resistance, allowing for miniaturization and simplification of the cooling mechanism required for heat dissipation of the inverter unit 30, such as a heat sink or a water-cooling mechanism. Furthermore, the switching element 31 using a wide band gap semiconductor has a high switching speed, low power loss, and can improve power conversion efficiency.

[0018] The motor power detection unit 50 is installed between the three-phase power lines and each switch 112. The motor power detection unit 50 detects the current and voltage used when a motor power calculation unit 41 of the inverter control unit 40, which will be described later, calculates the power to be supplied to each compressor motor 111. For this purpose, the motor power detection unit 50 has a voltage sensor and a current sensor. However, if the motor power calculation unit 41 can calculate the power to be supplied to the compressor motor 111 in addition to the voltage and current, the motor power detection unit 50 does not need to have a voltage sensor and a current sensor. Here, the system of the first embodiment has a motor power detection unit 50a and a motor power detection unit 50b corresponding to each compressor motor 111 to detect the current supplied to and the voltage applied to each compressor motor 111.

[0019] Inverter control unit 40 controls the driving of inverter unit 30. To this end, inverter control unit 40 in the first embodiment has a motor power calculation unit 41, a voltage command value determination unit 42, and a drive signal generation unit 43. Motor power calculation unit 41 calculates the power to be supplied to each compressor motor 111 based on the current and voltage detected by motor power detection unit 50. Furthermore, voltage command value determination unit 42 determines an output voltage command value that becomes the high-frequency voltage that inverter unit 30 applies to compressor motor 111. Drive signal generation unit 43 generates a drive signal that drives inverter unit 30 based on the output voltage command value determined by voltage command value determination unit 42.

[0020] Here, the inverter control unit 40 has a normal mode in which the compressor motor 111 is driven to operate the compressor 110 during operation of the heat pump device, and a heating mode in which a high-frequency AC voltage is applied to the compressor motor 111 to heat the compressor 110 without rotating or moving the compressor motor 111. In the first embodiment, a case in which the inverter control unit 40 performs control in the heating mode will be mainly described.

[0021] Next, a case where a high-frequency AC voltage is applied to the compressor motor 111 to heat the compressor 110 will be described. When heating the compressor 110, the inverter control unit 40 drives the inverter unit 30 so that the rotating shaft of the compressor motor 111 does not rotate and the compressor 110 does not operate. Then, the inverter unit 30 applies a high-frequency AC voltage to the compressor motor 111 to cause the windings of the compressor motor 111 to generate heat, thereby heating the compressor 110. Hereinafter, this will be described as "constrained energization."

[0022] 2 is a diagram showing a flowchart of a heating mode determination process when constrained energization is started according to embodiment 1. Here, a process will be described in which the voltage command value determiner 42 of the inverter control unit 40 determines which of a plurality of heating modes to perform when constrained energization is started.

[0023] When starting the restraint energization, the motor power calculation unit 41 of the inverter control unit 40 calculates the power to be supplied to the compressor motor 111 based on the current and voltage detected by the motor power detection unit 50. Here, the power calculated by the motor power calculation unit 41 based on the current and voltage detected by the motor power detection unit 50a is referred to as "compressor power a." Furthermore, the power calculated by the motor power calculation unit 41 based on the current and voltage detected by the motor power detection unit 50b is referred to as "compressor power b."

[0024] The voltage command value determination unit 42 determines whether the compressor power a is greater than a power supply determination power value (step S1). The voltage command value determination unit 42 also determines whether the compressor power b is greater than a power supply determination power value (steps S2 and S3). The power supply determination power value is a threshold value set based on a power level at which the switch 112 is turned on and it can be detected that a high-frequency AC voltage is being applied to the windings of the compressor motor 111.

[0025] When the voltage command value determination unit 42 determines that the compressor power a and the compressor power b are greater than the energization determination power value, it determines that both switches 112 are on (step S4) and transitions to a multiple-compressor heating mode in which all compressors 110 are heated at once (step S5). Then, the drive signal generation unit 43 sends a drive signal based on the output voltage command value determined by the voltage command value determination unit 42 by executing the multiple-compressor heating mode to the inverter unit 30, and performs constrained energization control (step S8).

[0026] Furthermore, when the voltage command value determination unit 42 determines that either the compressor power a or the compressor power b is greater than the energization determination power value, it determines that one of the switches 112 is on (step S6) and transitions to a single-compressor heating mode in which one compressor 110 is heated (step S7). Here, in the first embodiment, since there are two compressors 110, the single-compressor heating mode will be described as heating one compressor 110, but this is not limited to this. If the heat pump apparatus has three or more compressors 110, the compressors 110 may be divided into multiple groups, one by one, and the compressors 110 may be heated on a group-by-group basis. Then, the drive signal generation unit 43 sends a drive signal based on the output voltage command value determined by the voltage command value determination unit 42 by executing the single-compressor heating mode to the inverter unit 30, and performs constrained energization control (step S8).

[0027] Then, when the voltage command value determination unit 42 determines that both the compressor power a and the compressor power b are equal to or less than the energization determination power value, it determines that both switches 112 are off (step S9) and does not perform constrained energization (step S10).

[0028] Here, in the system according to the first embodiment, as described above, the control device of the heat pump device controls the switching of switch 112. Therefore, here, voltage command value determiner 42 determines the heating mode based on the power supplied to compressor motor 111. However, in cases where inverter control unit 40 controls the switching of switch 112, or in other cases where inverter control unit 40 can determine whether switch 112 is on or off, the heating mode may be determined without making a determination based on power.

[0029] 3 is a flowchart of the output voltage command value determination process in the multiple compressor heating mode according to the first embodiment. Here, the upper limit of the total power, which is the sum of the powers supplied to the compressor motors 111 during constrained energization, is defined as the "power upper limit." Also, the target power value for the power supplied to the compressor motor 111 of one compressor 110 is defined as the "target power value." The total target power value for the compressor motors 111 of the compressors 110 to be heated is always set to be less than the power upper limit.

[0030] The voltage command value determination unit 42 starts constrained energization in the multiple-compressor heating mode based on a preset initial value of the output voltage command value. Then, the voltage command value determination unit 42 calculates a total power value, which is the sum of compressor power a and compressor power b based on the initial value (step S11). Furthermore, the voltage command value determination unit 42 determines whether the total power value is smaller than a preset power upper limit value (step S12). If the voltage command value determination unit 42 determines that the total power value is not smaller than the power upper limit value, it reduces the output voltage command value for the compressor motor 111 of each compressor 110 (step S13). Then, the process returns to step S11, and the voltage command value determination unit 42 continues control until the total power value becomes less than the power upper limit value.

[0031] On the other hand, if the voltage command value determination unit 42 determines that the total power value is smaller than the power upper limit value, it determines whether the compressor power a is greater than the target power value (step S14). Furthermore, the voltage command value determination unit 42 determines whether the compressor power b is greater than the target power value (step S15). If the voltage command value determination unit 42 determines in steps S14 and S15 that the compressor power a or the compressor power b is equal to or less than the target power value, it increases the output voltage command value for the compressor motor 111 of each compressor 110 (step S16). Then, the voltage command value determination unit 42 performs the processes of steps S14 to S16 until it determines that the compressor power a and the compressor power b are greater than the target power values.

[0032] If the voltage command value determination unit 42 determines that both the compressor power a and the compressor power b are greater than the target power values, it again calculates the total power value, which is the sum of the compressor power a and the compressor power b (step S17). Furthermore, the voltage command value determination unit 42 determines whether the total power value is less than the power upper limit value (step S18). If the voltage command value determination unit 42 determines that the total power value is not less than the power upper limit value, it determines that heating using multiple compressor motors 111 is not possible at the current shaft position, and switches the switch 112 to transition to the single-compressor heating mode (step S19). On the other hand, if the voltage command value determination unit 42 determines that the total power value is less than the power upper limit value, it finally determines the output voltage command value for the compressor motor 111 of each compressor 110 (step S20). Then, the drive signal generation unit 43 sends a drive signal based on the determined output voltage command value to the inverter unit 30 to perform constrained energization control.

[0033] 4 is a diagram showing a flowchart of the output voltage command value determination process in the single-compressor heating mode according to the first embodiment. As in the multiple-compressor heating mode, the voltage command value determination unit 42 starts constrained energization based on a preset initial value of the output voltage command value. Then, the voltage command value determination unit 42 calculates a total power value, which is the sum of compressor power a and compressor power b based on the initial values ​​(step S21). Furthermore, the voltage command value determination unit 42 determines whether the total power value is smaller than a preset power upper limit value (step S22). If the voltage command value determination unit 42 determines that the total power value is not smaller than the power upper limit value, it reduces the output voltage command value for the compressor motor 111 of each compressor 110 (step S23). Then, the process returns to step S21, and the voltage command value determination unit 42 continues control until the total power value becomes less than the power upper limit value.

[0034] On the other hand, if the voltage command value determination unit 42 determines that the total power value is smaller than the power upper limit value, it determines the compressor 110 to which power is to be supplied (step S24). The method for determining the compressor 110 is not particularly limited. For example, the order in which constrained energization is performed is determined in advance. Then, the compressor 110 is determined based on the order from among the compressors 110 whose corresponding switches 112 are on and to which power can be supplied. Then, the voltage command value determination unit 42 determines whether the compressor power to be supplied to the determined compressor 110 is greater than the target power value (step S25). If the voltage command value determination unit 42 determines that the compressor power is not greater than the target power value, it increases the output voltage command value for the compressor motor 111 of each compressor 110 (step S26). The voltage command value determination unit 42 performs the processes of steps S25 and S26 until it determines that the compressor power is greater than the target power value. On the other hand, if the voltage command value determination unit 42 determines that the compressor power is greater than the target power value, it determines an output voltage command value for the compressor motor 111 of the compressor 110 (step S27). Then, the drive signal generation unit 43 sends a drive signal based on the determined output voltage command value to the inverter unit 30, and performs constrained energization control. In the single-compressor heating mode, the inverter control unit 40 heats all of the compressors 110 by switching the compressors 110 that perform constrained energization in sequence at regular intervals.

[0035] As described above, according to the power conversion device 10 of the first embodiment, the voltage command value determiner 42 of the inverter control unit 40 determines an output voltage command value based on the power supplied to the compressor motors 111 of the multiple compressors 110. The drive signal generator 43 generates a drive signal based on the determined output voltage command value, drives the inverter unit 30 to supply power, and causes the compressor motors 111 to generate heat, thereby heating the compressors 110 through constrained energization. This allows the output voltage command value corresponding to the state of the compressor motors 111 to be determined, and power to be supplied through constrained energization. This prevents liquid refrigerant from accumulating in the compressor 110, thereby protecting the compressor 110. When constrained energization is performed on multiple compressor motors 111, the optimal amount of power varies depending on whether multiple compressor motors 111 are heated at the same time or a single compressor motor 111 is heated, making setting the output voltage command value complicated. The power conversion device 10 in the first embodiment can easily determine the output voltage command value for supplying the power required for the constrained energization by determining the output voltage command value based on the power detected by the power detection unit.

[0036] Furthermore, according to the power conversion device 10 of the first embodiment, the voltage command value determiner 42 of the inverter control unit 40 increases the output voltage command value until it determines that the power supplied to the compressor motor 111 is greater than the target power value. When the voltage command value determiner 42 determines that the total power value supplied when performing constrained energization to all of the compressor motors 111 is less than the power upper limit, the voltage command value determiner 42 executes a multiple-compressor heating mode in which constrained energization is performed all at once. When the voltage command value determiner 42 determines that the total power value supplied when performing constrained energization to all of the compressor motors 111 is equal to or greater than the power upper limit, the voltage command value determiner 42 executes a single-compressor heating mode in which constrained energization is performed one compressor at a time. Therefore, constrained energization can be performed without supplying power exceeding the power upper limit.

[0037] Furthermore, the voltage command value determination unit 42 of the inverter control unit 40 determines that the supplied power to the compressor motor 111 is less than the energization determination power value, and the power supply to the compressor motor 111 is cut off by the switch 112. Then, the voltage command value determination unit 42 executes the single-compressor heating mode for the compressor motor 111 that is determined to be equal to or greater than the energization determination power value. Therefore, it is possible to determine an output voltage command value corresponding to the state of the compressor motor 111, and supply power through constrained energization.

[0038] Furthermore, power conversion device 10 in the first embodiment uses wide bandgap semiconductors such as silicon carbide, gallium nitride-based materials, or diamond for at least one switching element 31 and backflow prevention element 32, which is a diode, in inverter unit 30. By using wide bandgap semiconductors with high voltage resistance and allowable current, it is possible to miniaturize the elements, suppress power loss, and improve power conversion efficiency.

[0039] Embodiment 2 Fig. 5 is a diagram showing the configuration of an air conditioning system 1 according to embodiment 2. Here, the air conditioning system 1 will be described as an example of a heat pump device having a power conversion device 10. Here, the configuration of the air conditioning system 1 in Fig. 5 is one example, and the configuration of the heat pump device is not particularly limited.

[0040] 5, an outdoor unit (outdoor unit) 100 and an indoor unit (indoor unit) 200 are connected by refrigerant piping 300 to form a refrigerant circuit that circulates refrigerant. The outdoor unit 100 has a compressor 110 (compressor 110a and compressor 110b), a four-way valve 120, an outdoor heat exchanger 130, an expansion valve 140, and an outdoor blower 150. The indoor unit 200 has an indoor heat exchanger 210.

[0041] The compressor 110 compresses and discharges the sucked refrigerant. Here, the drive frequency of the compressor 110 can be changed arbitrarily by the power conversion device 10 described in the first embodiment, and the capacity of the compressor 110 (the amount of refrigerant delivered per unit time) can be changed finely. The four-way valve 120 is a flow path switching valve that switches the flow of the refrigerant depending on whether it is in cooling operation or heating operation.

[0042] The outdoor heat exchanger 130 exchanges heat between the refrigerant and air (outdoor air). During heating operation, the outdoor heat exchanger 130 functions as an evaporator, evaporating and vaporizing the refrigerant. During cooling operation, the outdoor heat exchanger 130 functions as a condenser, condensing and liquefying the refrigerant. The outdoor fan 150 sends outdoor air to the outdoor heat exchanger 130, promoting heat exchange between the outdoor air and the refrigerant.

[0043] The expansion valve 140, such as a throttle device serving as a pressure reducing device, is a refrigerant flow rate adjustment valve that reduces the pressure of the refrigerant to expand it and control the flow rate of the refrigerant. For example, if the expansion valve 140 is configured to include an electronic expansion valve or the like, its opening degree is adjusted based on instructions from a control device (not shown). The indoor heat exchanger 210 exchanges heat between the air to be conditioned and the refrigerant. During heating operation, the indoor heat exchanger 210 functions as a condenser, condensing and liquefying the refrigerant. During cooling operation, the indoor heat exchanger 210 functions as an evaporator, evaporating and vaporizing the refrigerant. The indoor blower 220 sends the air to be conditioned to the indoor heat exchanger 210, promoting heat exchange between the air and the refrigerant.

[0044] As described above, the air conditioning system 1 according to the second embodiment is configured to include the power conversion device 10 described in the first embodiment, thereby enabling efficient restricted energization of the multiple compressors 110. This prevents liquid refrigerant from accumulating in the compressors 110, thereby protecting the compressors 110.

[0045] Various aspects of the present disclosure are summarized below as appendices.

[0046] (Appendix 1) an inverter circuit that applies a voltage corresponding to a frequency related to AC conversion to a compressor motor of each of two or more compressors that compress a refrigerant, thereby supplying power; a motor power detection unit that detects the power supplied from the inverter circuit to each of the compressor motors; an inverter control unit that determines an output voltage command value based on the power value detected by the motor power detection unit in a heating mode in which the compressor is heated without operating the compressor motor, and generates a drive signal based on the determined output voltage command value to drive the inverter circuit; A power conversion device comprising: (Appendix 2) the inverter control unit, in the heating mode, executes a multiple-compressor heating mode in which all of the compressors are heated simultaneously when it determines that a total power value of the power supplied to all of the compressor motors according to the determined output voltage command value is smaller than a preset power upper limit value, and executes a single-compressor heating mode in which the compressors are heated separately when it determines that the total power value is equal to or greater than the power upper limit value. (Appendix 3) 3. The power conversion device according to claim 1, wherein the inverter control unit determines the output voltage command value when it determines that the power supplied to the compressor motor is greater than a target power value. (Appendix 4) The power conversion device according to claim 2, wherein, when it is determined that there is a compressor motor to which the supplied power is less than a power-on determination power value, the inverter control unit executes the single compressor heating mode for the compressor motor to which the power is equal to or greater than the power-on determination power value. (Appendix 5) 5. The power conversion device according to claim 1, wherein the inverter control unit has a normal mode in which the compressor motor operates and the compressor compresses the refrigerant, and the heating mode. (Appendix 6) 6. The power conversion device according to any one of claims 1 to 5, wherein at least one of the switching elements constituting the inverter circuit is formed from a wide bandgap semiconductor. (Appendix 7) 7. The power conversion device according to any one of claims 1 to 6, wherein the diodes of the switching elements constituting the inverter circuit are formed of wide bandgap semiconductors. (Appendix 8) 8. The power conversion device according to claim 6 or 7, wherein the wide band gap semiconductor is silicon carbide, a gallium nitride-based material, or diamond. (Appendix 9) a heat pump circuit in which two or more of the compressors, condensers, pressure reducing devices, and evaporators are connected by refrigerant piping; A heat pump device comprising the power conversion device according to any one of Supplementary Note 1 to Supplementary Note 8, which controls the driving of each of the compressor motors. [Explanation of symbols]

[0047] 0 Three-phase AC power supply, 1 Air conditioning system, 10 Power conversion device, 20 Rectification unit, 30 Inverter unit, 31 Switching element, 32 Backflow prevention element, 40 Inverter control unit, 41 Motor power calculation unit, 42 Voltage command value determination unit, 43 Drive signal generation unit, 50, 50a, 50b Motor power detection unit, 100 Outdoor unit, 110, 110a, 110b Compressor, 111, 111a, 111b Compressor motor, 112, 112a, 112b Switch, 120 Four-way valve, 130 Outdoor heat exchanger, 140 Expansion valve, 150 Outdoor blower, 200 Indoor unit, 210 Indoor heat exchanger, 220 Indoor blower, 300 Refrigerant piping.

Claims

1. an inverter circuit that applies a voltage corresponding to a frequency related to AC conversion to a compressor motor of each of two or more compressors that compress a refrigerant, thereby supplying power; a motor power detection unit that detects the power supplied from the inverter circuit to each of the compressor motors; an inverter control unit that determines an output voltage command value based on the power value detected by the motor power detection unit in a heating mode in which the compressor is heated without operating the compressor motor, and generates a drive signal based on the determined output voltage command value to drive the inverter circuit; A power conversion device comprising:

2. 2. The power conversion device according to claim 1, wherein, in the heating mode, when the inverter control unit determines that a total power value of the power supplied to all of the compressor motors according to the determined output voltage command value is smaller than a preset power upper limit value, the inverter control unit executes a multiple-compressor heating mode in which all of the compressors are heated simultaneously, and when the inverter control unit determines that the total power value is equal to or greater than the power upper limit value, the inverter control unit executes a single-compressor heating mode in which the compressors are heated separately.

3. 3. The power conversion device according to claim 1, wherein the inverter control unit determines the output voltage command value when it determines that the power supplied to the compressor motor is greater than a target power value.

4. 3. The power conversion device according to claim 2, wherein, when it is determined that there is a compressor motor to which the supplied electric power is less than a power-on determination power value, the inverter control unit executes the single-compressor heating mode for the compressor motor to which the electric power is equal to or greater than the power-on determination power value.

5. 3. The power conversion device according to claim 1, wherein the inverter control unit has a normal mode in which the compressor motor operates and the compressor compresses the refrigerant, and the heating mode.

6. 3. The power conversion device according to claim 1, wherein at least one of the switching elements constituting the inverter circuit is formed from a wide bandgap semiconductor.

7. 3. The power conversion device according to claim 1, wherein the diodes of the switching elements constituting the inverter circuit are formed of wide bandgap semiconductors.

8. 7. The power conversion device according to claim 6, wherein the wide bandgap semiconductor is silicon carbide, a gallium nitride-based material, or diamond.

9. a heat pump circuit in which two or more of the compressors, condensers, pressure reducing devices, and evaporators are connected by refrigerant piping; A heat pump apparatus comprising the power conversion apparatus according to claim 1 or 2, which controls driving of each of the compressor motors.

Images