Power conversion device and air conditioner

Abstract

Provided is a power conversion device or the like in which a power supply harmonic current is reduced while suppressing a decrease in efficiency. A power conversion device (100) comprises: a converter circuit (10) that converts an AC voltage applied from an AC power supply (E1) into a DC voltage; an inverter circuit (30) that converts the DC voltage on the output side of the converter circuit (10) into an AC voltage and applies the AC voltage to a motor (M1); and a control device (60) that controls the inverter circuit (30). The control device (60) adjusts the rotation speed and current phase of the motor (M1) so as to reduce the power supply harmonic current associated with the rectification in the converter circuit (10) by the motor harmonic current associated with the drive of the inverter circuit (30) and the motor (M1).

Description

Power conversion device and air conditioner

[0001] The present disclosure relates to a power conversion device and the like.

[0002] With regard to a power conversion device that converts AC power into DC power and further converts this DC power into a predetermined AC power, for example, the technology described in Patent Document 1 is known. That is, Patent Document 1 describes controlling the input current of the inverter unit so that the transfer characteristics of the input / output voltage of the inverter unit become attenuation characteristics due to a phase lead element and a second-order lag element connected in series.

[0003] Patent No. 4067021

[0004] As described above, in the technology described in Patent Document 1, the input current of the inverter unit is controlled so that the transfer characteristics of the input / output voltage of the inverter unit have predetermined attenuation characteristics. This reduces the power supply harmonic current on the AC power supply side, but the control of the input current causes distortion in the motor current waveform, which may lead to a decrease in efficiency.

[0005] Therefore, an object of the present disclosure is to provide a power conversion device or the like that is configured to reduce power supply harmonic currents while suppressing a decrease in efficiency.

[0006] In order to solve the above-mentioned problems, the power conversion device according to the present disclosure includes a converter circuit that converts an AC voltage applied from an AC power supply into a DC voltage, an inverter circuit that converts the DC voltage on the output side of the converter circuit into an AC voltage and applies the AC voltage to a motor, and a control unit that controls the inverter circuit, and the control unit adjusts the rotation speed and current phase of the motor so as to reduce power supply harmonic currents associated with the power conversion of the converter circuit using motor harmonic currents associated with driving the inverter circuit and the motor.

[0007] According to the present disclosure, it is possible to provide a power conversion device or the like that is configured to reduce power supply harmonic currents while suppressing a decrease in efficiency.

[0008] FIG. 1 is a configuration diagram of a power conversion device according to a first embodiment. FIG. 2 is an explanatory diagram including numerical examples of rotational speeds of motors that are candidates for suppressing power supply harmonic currents in the power conversion device according to the first embodiment. FIG. 3 is an explanatory diagram showing the relationship between the frequency of power supply harmonic currents, the rotational speed of the motor, and the frequency of motor harmonic currents in the power conversion device according to the first embodiment. FIG. 4 is a waveform diagram of three-phase power supply currents when motor harmonic currents are in phase with the power supply harmonic currents of a power conversion device according to a comparative example. FIG. 5 is a waveform diagram of three-phase power supply currents when motor harmonic currents are in opposite phase with the power supply harmonic currents of the power conversion device according to the first embodiment. FIG. 6 is a waveform diagram of DC reactor currents when motor harmonic currents are in phase with the power supply harmonic currents of the power conversion device according to the comparative example. FIG. 7 is a waveform diagram of DC reactor currents when motor harmonic currents are in opposite phase with the power supply harmonic currents of the power conversion device according to the first embodiment. FIG. 8 is a waveform diagram of three-phase motor currents when motor harmonic currents are in phase with the power supply harmonic currents of the power conversion device according to the comparative example. FIG. 1 is a waveform diagram of three-phase motor currents when the motor harmonic currents are in opposite phase to the power supply harmonic currents of the power conversion device according to the first embodiment. FIG. 2 is a diagram showing the results of high-frequency analysis of the power supply current of R-phase in the power conversion devices according to the first embodiment and the comparative example. FIG. 3 is a diagram showing the results of high-frequency analysis of the current I_DCL of a DC reactor in the power conversion devices according to the first embodiment and the comparative example. FIG. 4 is a configuration diagram of a power conversion device according to a first modified example of the first embodiment. FIG. 5 is a configuration diagram of a power conversion device according to a second modified example of the first embodiment. FIG. 6 is an explanatory diagram including a control device for a power conversion device according to the second embodiment. FIG. 7 is an explanatory diagram showing the relationship between a first rotation speed command and a second rotation speed command in the power conversion device according to the second embodiment. FIG. 8 is a configuration diagram of an air conditioner according to a third embodiment.

[0009] First Embodiment Configuration of Power Conversion Device Fig. 1 is a configuration diagram of a power conversion device 100 according to a first embodiment. The power conversion device 100 shown in Fig. 1 is a device that converts AC power supplied from an AC power source E1 into DC power, converts this DC power into predetermined AC power, and outputs it to a motor M1. The motor M1 may be, for example, a permanent magnet synchronous motor, or may be another type of motor.

[0010] As shown in FIG. 1, the power conversion device 100 includes a converter circuit 10, a DC voltage detection unit 20, an inverter circuit 30, power supply current detection units 41 and 42, motor current detection units 51 and 52, a control device 60 (control unit), and a gate drive circuit 70.

[0011] The converter circuit 10 is a circuit that converts an AC voltage applied from an AC power source E1 into a DC voltage. That is, the converter circuit 10 converts the AC voltage applied from the three-phase AC power source E1 into a DC voltage (a pulsating DC voltage) and further has the function of smoothing this DC voltage. As shown in FIG. 1 , the converter circuit 10 includes a diode bridge circuit 11, a DC reactor 12, and a smoothing capacitor 13.

[0012] The diode bridge circuit 11 is a circuit that performs full-wave rectification and includes six diodes D1 to D6. The diode bridge circuit 11 includes "legs" each configured by connecting a pair of diodes in series: a first leg (not shown, but the same applies below), a second leg, and a third leg. The first leg includes a pair of diodes D1 and D2 connected in series. The cathode of the diode D1 is connected to the positive DC line K1. The anode of the diode D1 is connected to the cathode of the other diode D2. The anode of the other diode D2 is connected to the negative DC line K2. The same applies to the remaining second and third legs. The first, second, and third legs are connected in parallel.

[0013] The connection point between diodes D1 and D2 of the first leg is connected to AC power supply E1 via R-phase wiring HR. The connection point between diodes D3 and D4 of the second leg is connected to AC power supply E1 via S-phase wiring HS. The connection point between diodes D5 and D6 of the third leg is connected to AC power supply E1 via T-phase wiring HT. The AC voltage applied from AC power supply E1 is converted into a pulsating DC voltage by diode bridge circuit 11.

[0014] The DC reactor 12 and the smoothing capacitor 13 are elements for smoothing the pulsating DC voltage applied from the diode bridge circuit 11. As shown in Fig. 1, the DC reactor 12 is provided on the positive DC line K1. More specifically, the DC reactor 12 is provided on the positive DC line K1 between the diode bridge circuit 11 and a connection point between the DC line K1 and the smoothing capacitor 13.

[0015] The smoothing capacitor 13 is connected to a pair of DC lines K1, K2 on the output side of the diode bridge circuit 11. That is, one end (one lead wire) of the smoothing capacitor 13 is connected to the positive DC line K1, and the other end (the other lead wire) is connected to the negative DC line K2. For example, a film capacitor or an electrolytic capacitor is used as the smoothing capacitor 13.

[0016] Film capacitors have a smaller capacitance per unit volume than electrolytic capacitors, but a larger rated ripple current. Therefore, film capacitors can be used with a lower capacitance than electrolytic capacitors, making them less expensive and enabling the circuit board (not shown) of the power conversion device 100 to be made smaller. Film capacitors also have the advantage of a long life. However, when a film capacitor is used as the smoothing capacitor 13, its small capacitance makes it more likely for harmonic currents to be generated on the AC power supply E1 side. Therefore, in the first embodiment, the control device 60 controls the inverter circuit 30 in a predetermined manner to suppress harmonic currents on the power supply side. The type of smoothing capacitor 13 is not limited to a film capacitor, and other types of capacitors may be used.

[0017] As shown in FIG. 1 , the output side of the converter circuit 10 is connected to an inverter circuit 30 via a pair of DC lines K1 and K2. The DC voltage detection unit 20 detects the DC voltage between the pair of DC lines K1 and K2. For example, the DC voltage between the DC lines K1 and K2 may be divided by a series connection of multiple resistor elements (not shown), and the DC voltage between the DC lines K1 and K2 may be detected based on the voltage division ratio or the voltage of a predetermined resistor element. The DC voltage detection unit 20 outputs the detected value at every moment to the control device 60.

[0018] The inverter circuit 30 converts the DC voltage on the output side of the converter circuit 10 into an AC voltage and applies this AC voltage to the motor M1. The inverter circuit 30 includes a first leg (not shown, but the same applies below) a second leg, and a third leg as "legs" each configured by a pair of switching elements connected in series. The first leg, second leg, and third leg are connected in parallel to the smoothing capacitor 13.

[0019] The first leg includes a pair of switching elements S1 and S2 connected in series. The second leg and the third leg are similarly configured. In the example of FIG. 1, IGBTs (Insulated Gate Bipolar Transistors) are used as the switching elements S1 to S6, but other types of switching elements such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) may also be used.

[0020] In the first leg of the inverter circuit 30, the connection point between the pair of switching elements S1 and S2 is connected to the U-phase winding of the motor M1 via a wiring HU. In the second leg, the connection point between the switching elements S3 and S4 is connected to the V-phase winding of the motor M1 via a wiring HV. In the third leg, the connection point between the switching elements S5 and S6 is connected to the W-phase winding of the motor M1 via a wiring HW.

[0021] Furthermore, in order to prevent breakdown of the switching elements S1 to S6 due to commutation in the inverter circuit 30, a free wheel diode (not shown) is connected in anti-parallel to each of the switching elements S1 to S6. Note that if the switching elements S1 to S6 have a parasitic diode (not shown), the parasitic diode functions as the free wheel diode, and therefore there is no particular need to provide a separate free wheel diode.

[0022] The power supply current detectors 41 and 42 detect the power supply current flowing through the wiring HR, HS, and HT (connecting lines) connecting the AC power supply E1 and the converter circuit 10. In the example of Fig. 1, the power supply current detector 41 detects the R-phase power supply current, and another power supply current detector 42 detects the S-phase power supply current. The detected values ​​of the power supply current detectors 41 and 42 are output to the control device 60.

[0023] Motor current detectors 51 and 52 detect the current in the windings of motor M1. In the example of Fig. 1, motor current detector 51 detects the U-phase motor current, and another motor current detector 52 detects the V-phase AC current. The values ​​detected by motor current detectors 51 and 52 at each moment are output to control device 60.

[0024] The control device 60 (controller) has a function of controlling the inverter circuit 30 via the gate drive circuit 70. For example, a microcomputer is used as the control device 60. Although not shown, the microcomputer is configured to include electronic circuits such as a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various interfaces, and reads out a program stored in the ROM and loads it into the RAM, allowing the CPU to execute various processes.

[0025] The control device 60 generates a predetermined PWM signal (Pulse Width Modulation) based on the detected values ​​of the DC voltage detection unit 20, the power supply current detection units 41 and 42, and the motor current detection units 51 and 52. The method of generating the PWM signal is well known, so a description thereof will be omitted. The PWM signal generated by the control device 60 is output to the gate drive circuit 70.

[0026] The gate drive circuit 70 applies a predetermined voltage to each gate of the switching elements S1 to S6 based on a PWM signal from the control device 60. This switches the switching elements S1 to S6 on and off in a predetermined manner, applies an AC voltage to the three-phase windings of the motor M1, and drives the motor M1.

[0027] <About Harmonic Currents> As described above, in the converter circuit 10, AC voltage is rectified to DC voltage (full-wave rectification in the configuration of FIG. 1 ). As a result, currents with waveforms in which multiple harmonic components are superimposed on a sinusoidal fundamental wave are generated in the power supply wiring HR, HS, and HT and the DC lines K1 and K2 as a result of power conversion in the converter circuit 10. Such currents with harmonic components that accompany power conversion in the converter circuit 10 are called "power supply harmonic currents." Furthermore, sinusoidal power supply harmonic currents that change at a frequency n times (n is an integer greater than or equal to 3) the fundamental wave of the power supply frequency (50 Hz or 60 Hz) are called "nth-order power supply harmonic currents." Furthermore, the frequency of the fundamental wave is called the "fundamental frequency."

[0028] For example, if the fundamental frequency is 60 Hz, the frequency of the fifth-order power supply harmonic current is 5 × 60 = 300 Hz. Similarly, the frequency of the seventh-order power supply harmonic current is 7 × 60 = 420 Hz. As described above, because rectification is performed in the converter circuit 10, fifth-order, seventh-order, eleventh-order, thirteenth-order, seventeenth-order, nineteenth-order, twenty-third-order, twenty-fifth-order, etc. power supply harmonic currents are generated in the wiring HR, HS, and HT, with the power supply frequency of 50 Hz or 60 Hz as the fundamental frequency. The orders of these power supply harmonic currents are mathematically derived based on the configuration of the converter circuit 10, etc.

[0029] On the other hand, in the DC lines K1 and K2, the power supply harmonic currents associated with the power conversion of the converter circuit 10 appear as power supply harmonic currents of orders that are integer multiples of six, such as sixth, twelfth, eighteenth, twenty-fourth, etc., with a fundamental power supply frequency of 50 Hz or 60 Hz. To give a specific example, the fifth- and seventh-order power supply harmonic currents in the power supply wiring HR, HS, and HT appear as sixth-order power supply harmonic currents in the DC lines K1 and K2. Furthermore, the eleventh- and thirteenth-order power supply harmonic currents in the power supply wiring HR, HS, and HT appear as twelfth-order power supply harmonic currents in the DC lines K1 and K2. The lower the order of the power supply harmonic currents, the larger their current values ​​tend to be. These factors can also be mathematically derived based on the configuration of the converter circuit 10, etc.

[0030] If the power supply frequency (i.e., fundamental frequency) of the AC power supply E1 is fs, the frequency fsh of the power supply harmonic current in the DC lines K1 and K2 is expressed by the following equation (1): where x is a natural number.

[0031]

[0032] In addition to the converter circuit 10, the inverter circuit 30 and the motor M1 are also sources of harmonic current. That is, as the inverter circuit 30 and the motor M1 are driven, a current with a waveform in which multiple harmonic components are superimposed on a sinusoidal fundamental wave is generated in the wiring HU, HV, and HW on the motor M1 side and in the DC lines K1 and K2. The current with harmonic components that accompanies the drive of the inverter circuit 30 and the motor M1 is referred to as a "motor harmonic current."

[0033] Specifically, with the electrical angular frequency of motor M1 as the fundamental frequency, 5th, 7th, 11th, 13th, 17th, 19th, 23rd, 25th, ... motor harmonic currents are generated in wiring HU, HV, HW on the motor M1 side. The orders of these motor harmonic currents are mathematically derived based on the configurations of inverter circuit 30 and motor M1, etc.

[0034] On the other hand, in the DC lines K1 and K2, harmonic currents appear as motor harmonic currents of orders that are integer multiples of six, such as sixth, twelfth, eighteenth, twenty-fourth, and so on, with the electrical angular frequency of the motor M1 as the fundamental frequency. To give a specific example, the fifth- and seventh-order motor harmonic currents in the wiring HU, HV, and HW on the motor M1 side appear as sixth-order motor harmonic currents in the DC lines K1 and K2. Furthermore, the eleventh- and thirteenth-order motor harmonic currents in the wiring HU, HV, and HW on the motor M1 side appear as twelfth-order motor harmonic currents in the DC lines K1 and K2. Note that the lower the order of the motor harmonic current, the larger its current value tends to be. These factors can also be mathematically derived based on the configuration of the inverter circuit 30 and the motor M1, among other factors.

[0035] If the rotation speed (number of rotations per minute) of the motor M1 is fm, the frequency fmh of the motor harmonic currents in the DC lines K1 and K2 is expressed by the following equation (2): P in equation (2) is the number of poles of the motor M1, and y is a natural number.

[0036]

[0037] As described above, power supply harmonic currents are generated in association with power conversion in the converter circuit 10, while motor harmonic currents are also generated in association with driving the inverter circuit 30 and the motor M1. As a result, currents with predetermined waveforms in which power supply harmonic currents and motor harmonic currents are superimposed on a fundamental wave flow through the DC lines K1 and K2 and the power supply wiring HR, HS, and HT.

[0038] Therefore, in the first embodiment, the control device 60 adjusts the rotation speed and current phase of the motor M1 so that the power supply harmonic current is reduced by the motor harmonic current. Note that the motor harmonic current may be configured to completely cancel out the power supply harmonic current of a predetermined order, or may be configured to reduce (partially cancel) the power supply harmonic current.

[0039] In order to reduce the power supply harmonic current by the motor harmonic current, the control device 60 makes the frequency of the motor harmonic current of a predetermined order coincide with the power supply harmonic current of a predetermined order. In other words, the control device 60 makes the frequency fsh of the power supply harmonic current in the above-mentioned equation (1) equal to the frequency fmh of the motor harmonic current in the equation (2). This relationship is expressed by the following equation (3):

[0040]

[0041] When formula (3) is rearranged for the rotation speed fm of the motor M1, the following formula (4) is obtained.

[0042]

[0043] For example, let us assume that 60 [Hz] is substituted as the value of the power supply frequency fs included in equation (4) and 6 is substituted as the number of poles P of the motor M1. If the maximum order of the power supply harmonic current to be suppressed is 25th, the maximum value of the natural number x is 4. Since the harmonic content rate decreases as the order of the motor current harmonics increases, the maximum value of y is 5. Furthermore, let us assume that the range of the rotation speed fm of the motor M1 is 600 to 7000 [min －１ ], then there are multiple candidates for the rotation speed fm of the motor M1 as shown in FIG.

[0044] FIG. 2 is an explanatory diagram including examples of numerical values ​​of the rotation speed of a motor that is a candidate for suppressing power supply harmonic current (see also FIG. 1 as appropriate). In the "Application" column of FIG. 2, it is noted that the rotation speed fm of the motor M1 is 600 to 7000 [min －１ ] are marked with a "○", and those outside this range are marked with an "×". x and y shown in FIG. 2 correspond to the natural numbers x and y included in equation (4). Also, fm shown in FIG. 2 corresponds to the rotation speed fm of motor M1 included in equation (4).

[0045] For example, if the values ​​of the natural numbers x and y included in the formula (4) are both "1", the value of the rotation speed fm of the motor M1 is 1200 [min －１ In this case, the order of the power supply harmonic current (six times the natural number x) and the order of the motor harmonic current (six times the natural number y) are both sixth order. If the value of the natural number x in equation (4) is set to "1" and the value of the natural number y is set to "2", the value of the rotation speed fm of the motor M1 becomes 600 [min －１ In this case, the order of the power supply harmonic current is 6th, and the order of the motor harmonic current is 12th. In this way, there are multiple cases where equation (4) holds true.

[0046] FIG. 3 is an explanatory diagram showing the relationship between the frequency of power supply harmonic current, the motor rotation speed, and the frequency of motor harmonic current. The explanatory diagram in FIG. 3 corresponds to the table in FIG. 2. The numbers enclosed in bold lines in FIG. 3 indicate that the frequency of the power supply harmonic current is equal to the frequency of the motor harmonic current. The "order" in FIG. 3 indicates the order of the power supply harmonic current and the motor harmonic current. In the example in FIG. 3, the power supply frequency is 60 Hz, so the frequency of the 6th order power supply harmonic current is 6 x 60 = 360 Hz. The same applies to the frequencies of the 12th, 18th, 24th, and 30th order power supply harmonic currents.

[0047] In the "Motor rotation speed" column in Fig. 3, the rotation speeds of the motor M1 are arranged in descending order, excluding those marked with an "x" from Fig. 2. The "Motor harmonic current frequency" column shows the frequency of the motor harmonic current, which is determined by the rotation speed and number of poles of the motor M1 (6 poles in the example of Fig. 3).

[0048] For example, if the rotation speed of the motor M1 is 1200 [min －１ ], the frequencies of the motor harmonic currents (the values ​​of fmh in the above-mentioned formula (2)) are 360 ​​[Hz] for the 6th harmonic, 720 [Hz] for the 12th harmonic, 1080 [Hz] for the 18th harmonic, 1440 [Hz] for the 24th harmonic, and 1800 [Hz] for the 30th harmonic. Similarly, the frequencies of the power supply harmonic currents (the values ​​of fsh in the above-mentioned formula (1)) are 360 ​​[Hz] for the 6th harmonic, 720 [Hz] for the 12th harmonic, 1080 [Hz] for the 18th harmonic, 1440 [Hz] for the 24th harmonic, and 1800 [Hz] for the 30th harmonic. In other words, the values ​​of each order of the motor harmonic currents and the power supply harmonic currents match each other.

[0049] The rotation speed of the motor M1 is set to 1200 [min －１ ], the frequencies of the 6th harmonic motor current and the 6th harmonic power supply current correspond to the case where x = 1, y = 1 in Fig. 2. Furthermore, the frequencies of the 12th harmonic motor current and the 12th harmonic power supply current correspond to the case where x = 2, y = 2 in Fig. 2. The same applies to the remaining 18th, 24th, and 30th harmonics.

[0050] Also, for example, the rotation speed of the motor M1 is set to 600 [min －１ ], the frequencies of the motor harmonic current are 180 [Hz] for the 6th harmonic, 360 [Hz] for the 12th harmonic, 540 [Hz] for the 18th harmonic, 720 [Hz] for the 24th harmonic, and 900 [Hz] for the 30th harmonic. Of these, the 12th and 24th harmonics match the frequencies of the power supply harmonic current. That is, the frequency of the 12th motor harmonic current (360 [Hz]) matches the frequency of the 6th power supply harmonic current. This corresponds to the case where x = 1, y = 2 in FIG. 2. Furthermore, the frequency of the 24th motor harmonic current (720 [Hz]) matches the frequency of the 12th power supply harmonic current. This corresponds to the case where x = 2, y = 4 in FIG. 2.

[0051] In this way, when the frequency of the motor harmonic current matches the frequency of the power supply harmonic current, the order of each harmonic differs depending on the rotation speed of the motor M1. In the example of FIG. 3, the rotation speed of the motor M1 is set to 1200 [min －１ ], the frequency of the motor harmonic current matches the frequency of the power supply harmonic current at each order, but in other cases, the frequencies match at some orders.

[0052] Therefore, the control device 60 (see FIG. 1) adjusts the rotation speed of the motor M1 so that the frequencies of the power supply harmonic current and the motor harmonic current match at a predetermined order, and further adjusts the current phase of the motor M1 so that the motor harmonic current is in opposite phase to the power supply harmonic current. As a result, the power supply harmonic current is at least partially canceled out by the motor harmonic current, and the power supply harmonic current can be reduced.

[0053] The rotation speed of the motor M1 when the power supply harmonic current is reduced by the motor harmonic current is set based on the frequency of the AC power supply E1 and the number of poles of the motor M1. Which of the 11 rotation speed candidates shown in Figure 3 the control device 60 uses as the specified rotation speed value of the motor M1 is appropriately set based on the operating conditions of the motor M1, etc.

[0054] To explain the method for adjusting the phase of the motor current, the control device 60 (controller) varies the current phase of the motor M1 while driving the motor M1 at a predetermined rotational speed. Based on the detected values ​​of the power supply current detectors 41 and 42 (see FIG. 1 ), the control device 60 adjusts the current phase of the motor M1 so as to reduce harmonic components contained in the detected values. For example, the control device 60 removes fundamental components from the detected values ​​of the power supply current detectors 41 and 42 (see FIG. 1 ) and calculates the effective value of the current on which multiple harmonic components are superimposed. The control device 60 then repeatedly varies the current phase at a predetermined interval and calculates the effective value of the current (on which multiple harmonic components are superimposed). The control device 60 then drives the motor M1 with a current phase that minimizes the effective value of the current. In this case, the power supply harmonic current is reduced by the motor harmonic current.

[0055] Alternatively, the control device 60 may use high-frequency analysis based on a discrete Fourier transform (FFT) as an alternative method for adjusting the current phase of the motor M1. In this case, the control device 60 drives the motor M1 with a current phase that minimizes the value of a predetermined order of power supply harmonic current.

[0056] In this way, the control device 60 (controller) adjusts the rotation speed and current phase of the motor M1 so as to reduce the power supply harmonic current associated with the power conversion of the converter circuit 10, using the motor harmonic current associated with the drive of the inverter circuit 30 and the motor M1. This reduces the power supply harmonic current, allowing operation to comply with power supply harmonic regulations and preventing failure or malfunction of equipment (not shown) connected to the AC power supply E1.

[0057] <Simulation Results> Next, a comparative example (see FIGS. 4A, 5A, and 6A) in which the motor harmonic currents are in phase with the power supply harmonic currents and a first embodiment (see FIGS. 4B, 5B, and 6B) in which they are in opposite phases will be described. As shown in FIG. 1, the three-phase power supply currents (AC currents) input to the converter circuit 10 are designated as Is_R, Is_S, and Is_T. Furthermore, the current flowing through the DC reactor 12 is designated as I_DCL, and the three-phase motor currents are designated as Im_U, Im_V, and Im_W.

[0058] 4A is a waveform diagram of three-phase power supply currents Is_R, Is_S, and Is_T when the motor harmonic currents are in phase with the power supply harmonic currents of a power conversion device according to a comparative example. Note that the comparative example is the same as the first embodiment except that the motor harmonic currents are in phase with the power supply harmonic currents. In the example of FIG. 4A, the power supply voltage of the AC power supply E1 (see FIG. 1) is 200 [V], 60 [Hz], the inductance of the DC reactor 12 (see FIG. 1) is 0.136 [mH], and the capacitance of the smoothing capacitor 13 (see FIG. 1) is 90 [μF]. In addition, the rotation speed of the motor M1 is 4800 [min －１ ], and the number of poles of the motor M1 is six (that is, the number of pole pairs is three).

[0059] In this case, the rotation speed of the motor M1 in FIG. －１ As shown in the column labeled "1440 Hz," the frequency of the 24th-order power supply harmonic current and the frequency of the 6th-order motor harmonic current are both 1440 Hz. The power supply frequency (60 Hz) of the AC power supply E1 and the number of poles (6) of the motor M1 in Fig. 3 are the same as those in Fig. 4A.

[0060] If the 6th-order motor harmonic current is in phase with the 24th-order power supply harmonic current, the power supply harmonic current will be amplified by the motor harmonic current, and the three-phase power supply currents Is_R, Is_S, and Is_T will have steep waveforms as shown in the comparative example of Figure 4A.

[0061] Fig. 4B is a waveform diagram of three-phase power supply currents Is_R, Is_S, and Is_T when the motor harmonic currents are in opposite phase to the power supply harmonic currents of the power conversion device according to the first embodiment. In Fig. 4B, the conditions such as the power supply voltage, the number of poles of the motor M1, and the rotation speed are the same as those in Fig. 4A (the same applies to Figs. 5A, 5B, 6A, 6B, 7A, and 7B).

[0062] When the sixth-order motor harmonic current is in opposite phase to the aforementioned 24th-order power supply harmonic current, the sixth-order motor harmonic current cancels out the 24th-order power supply harmonic current. Therefore, in the waveform diagram of Fig. 4B, the three-phase power supply currents Is_R, Is_S, and Is_T have rounder waveforms than in the comparative example of Fig. 4A. Note that whether the 24th-order power supply harmonic current has actually been reduced can be determined by frequency analysis of the power supply current (see Fig. 7B).

[0063] 5A is a waveform diagram of the current I_DCL of the DC reactor when the motor harmonic current is in phase with the power supply harmonic current of the power conversion device according to the comparative example. When the 6th-order motor harmonic current is in phase with the 24th-order power supply harmonic current described above, the power supply harmonic current is amplified by the motor harmonic current, and the current I_DCL of the DC reactor 12 (see FIG. 1) has a steep waveform as shown in the comparative example of FIG. 5A.

[0064] Fig. 5B is a waveform diagram of the current I_DCL of the DC reactor when the motor harmonic current is in opposite phase to the power supply harmonic current of the power conversion device according to the first embodiment. When the sixth-order motor harmonic current is in opposite phase to the 24th-order power supply harmonic current described above, the 24th-order power supply harmonic current is canceled out by the sixth-order motor harmonic current. Therefore, in the waveform diagram of Fig. 5B, the current I_DCL of the DC reactor 12 (see Fig. 1) has a rounder waveform than in the comparative example of Fig. 5A.

[0065] 6A is a waveform diagram of three-phase motor currents Im_U, Im_V, and Im_W when the motor harmonic currents are in phase with the power supply harmonic currents of a power conversion device according to a comparative example. As shown in FIG. 6A, three-phase motor currents Im_U, Im_V, and Im_W of different phases flow through the windings of the motor M1. Note that each of the motor currents Im_U, Im_V, and Im_W contains a predetermined harmonic component.

[0066] Fig. 6B is a waveform diagram of three-phase motor currents Im_U, Im_V, and Im_W when the motor harmonic currents are in opposite phase to the power supply harmonic currents of the power conversion device according to the first embodiment. The way in which the motor currents Im_U, Im_V, and Im_W change shown in Fig. 6B is similar to the comparative example of Fig. 6A, but the phases of the motor currents Im_U, Im_V, and Im_W are different from those in the comparative example. This is because the current phase of motor M1 is adjusted so that the 6th-order motor harmonic current is in opposite phase to the 24th-order power supply harmonic current described above.

[0067] FIG. 7A is a diagram showing the results of high-frequency analysis of the R-phase power supply current in the power conversion devices according to the first embodiment and the comparative example. The horizontal axis of FIG. 7A represents frequency, and the vertical axis represents the high-frequency content. In FIG. 7A, the solid line shows the results of the high-frequency analysis when the motor harmonic current is out of phase with the power supply harmonic current (first embodiment). The dashed line shows the results of the high-frequency analysis when the motor harmonic current is in phase with the power supply harmonic current (comparative example). The results of the high-frequency analysis shown in FIG. 7A are based on the data in FIGS. 4A, 4B, 5A, 5B, 6A, and 6B. Discrete Fourier transform (FFT) was used as the high-frequency analysis method.

[0068] As shown in the area surrounded by the dashed line in Figure 7A, the power supply harmonic current contained in the power supply current is reduced, particularly at 1380 [Hz] (the frequency of the 23rd power supply harmonic current). Furthermore, although not shown in Figure 7A, the power supply harmonic current is also reduced at 1500 [Hz], which is the frequency of the 25th power supply harmonic current. As described above, the 24th power supply harmonic current (1440 [Hz]: see Figure 3) in the DC lines K1 and K2 (see Figure 1) appears as 23rd and 25th power supply harmonic currents in the power supply wiring HR (see Figure 1). Although not shown in Figure 7A, the power supply harmonic currents near 1380 [Hz] and 1500 [Hz] are reduced compared to when no phase adjustment of the motor current is performed.

[0069] 7B is a diagram showing the results of high-frequency analysis of the current I_DCL of the DC reactor in the power conversion devices according to the first embodiment and the comparative example. The horizontal and vertical axes in FIG. 7B are the same as those in FIG. 7A. As shown in the area surrounded by the dashed dotted line in FIG. 7B, the power supply harmonic current included in the current I_DCL of the DC reactor 12 is reduced, particularly at 1440 Hz (the frequency of the 24th-order power supply harmonic current: see FIG. 3).

[0070] <Effects> According to the first embodiment, it is possible to reduce power supply harmonic currents even when a low-cost, long-life film capacitor is used as the smoothing capacitor 13. This makes it possible to prevent breakdowns and malfunctions of devices (not shown) connected to the AC power supply E1, and also enables operation in compliance with power supply harmonic regulations.

[0071] Furthermore, when a film capacitor is used as the smoothing capacitor 13, the smaller capacitance increases the resonant frequency between the smoothing capacitor 13 and the DC reactor 12. As a result, the power supply harmonic currents at frequencies close to this resonant frequency also tend to increase. Even in such cases, as described above, the power supply harmonic currents are reduced by the motor harmonic currents, so that breakdowns and malfunctions of devices (not shown) connected to the AC power supply E1 can be prevented.

[0072] Furthermore, in the first embodiment, the parameters adjusted when reducing the power supply harmonic current are the rotational speed and current phase of the motor M1. Therefore, compared to before the rotational speed and current phase were adjusted, there is almost no distortion in the waveform of the motor current, and therefore a decrease in the efficiency of the motor M1 can be suppressed. In this way, according to the first embodiment, it is possible to reduce the power supply harmonic current while suppressing a decrease in efficiency. Furthermore, since there is no particular distortion in the waveform of the motor current, fluctuations in the rotational speed of the motor M1 are suppressed. As a result, noise associated with driving the motor M1 can also be suppressed.

[0073] <<First Modification of First Embodiment>> Fig. 8 is a configuration diagram of a power conversion device 100A according to a first modification of the first embodiment. Note that Fig. 8 differs from the first embodiment (see Fig. 1) in that the power conversion device 100A includes a DC line current detection unit 80, but is otherwise similar to the first embodiment. Therefore, only the parts that differ from the first embodiment will be described, and a description of the overlapping parts will be omitted.

[0074] 8 is provided on the DC line K1 and detects the current flowing in the DC line K1 on the output side of the converter circuit 10. The DC line current detection unit 80 outputs the detected value from time to time to the control device 60.

[0075] In this configuration, the control device 60 (controller) changes the current phase of the motor M1 while driving the motor M1 at a predetermined rotational speed. Based on the detected value of the DC line current detector 80, the control device 60 adjusts the current phase of the motor M1 so as to reduce the harmonic components of this detected value. This method also makes it possible to identify the current phase of the motor M1 that can reduce a predetermined order of power supply harmonic current.

[0076] As described above, the harmonic components of the current in the DC line K1 also appear as predetermined harmonic components in the power supply wiring HR, HS, and HT. Therefore, when the harmonic components of the current in the DC line K1 are reduced, the power supply harmonic current is also reduced.

[0077] Fig. 9 is a configuration diagram of a power conversion device 100B according to a second modification of the first embodiment. Note that Fig. 9 differs from the first embodiment (see Fig. 1) in that the power conversion device 100B includes a DC reactor voltage detection unit 90, but is otherwise similar to the first embodiment. Therefore, only the parts that differ from the first embodiment will be described, and a description of the overlapping parts will be omitted.

[0078] 9 detects the voltage across the terminals of the DC reactor 12 provided on the DC line K1 on the output side of the converter circuit 10, and is connected to each terminal of the DC reactor 12. The values ​​detected by the DC reactor voltage detection unit 90 at each moment are output to the control device 60.

[0079] In this configuration, the control device 60 (controller) changes the current phase of the motor M1 while driving the motor M1 at a predetermined rotational speed. Based on the detected value of the DC reactor voltage detector 90, the control device 60 adjusts the current phase of the motor M1 so as to reduce the harmonic components of this detected value. This method also makes it possible to identify the current phase of the motor M1 that can reduce a predetermined order of power supply harmonic current.

[0080] Second Embodiment The second embodiment differs from the first embodiment in that a control device 60C (see FIG. 10) includes a rotation speed command regulator 61 (see FIG. 10). The rest of the second embodiment is similar to the first embodiment. Therefore, only the differences from the first embodiment will be described, and a description of the overlapping parts will be omitted.

[0081] Fig. 10 is an explanatory diagram including a control device 60C of a power conversion device according to the second embodiment. As shown in Fig. 10, the control device 60C includes a rotational speed command regulator 61. The rotational speed command regulator 61 (i.e., a control unit) converts a first rotational speed command for the motor M1 (see Fig. 1) based on the operating conditions of a device (not shown) that uses the motor M1 as a drive source into a second rotational speed command, and drives the motor M1 based on the second rotational speed command.

[0082] For example, when motor M1 (see FIG. 1 ) is used as the drive source for the compressor of an air conditioner, a command value (first rotational speed command) for the rotational speed of motor M1 is set based on various conditions, such as the operating mode, set temperature and airflow values, as well as detected values ​​of outdoor air temperature and indoor temperature. Therefore, in the second embodiment, if the absolute value of the deviation between the rotational speed of motor M1 at which the power supply harmonic current can be reduced by the motor harmonic current and the first rotational speed command is equal to or less than a predetermined value, rotational speed command adjuster 61 (i.e., control unit) sets this rotational speed as a second rotational speed command. Motor M1 is driven based on this second rotational speed command.

[0083] On the other hand, when the absolute value of the deviation between the rotation speed of the motor M1 (see FIG. 1) that can reduce the power supply harmonic current by the motor harmonic current and the first rotation speed command is larger than a predetermined value, the rotation speed command regulator 61 (i.e., the control unit) sets the same value as the first rotation speed command as the second rotation speed command. The motor M1 is driven based on this second rotation speed command. Note that the predetermined value (for example, 100 [min －１ ]) is a threshold value that serves as a criterion for determining whether or not to set the second rotation speed command to a value different from the first rotation speed command, and is set in advance.

[0084] FIG. 11 is an explanatory diagram showing the relationship between the first rotational speed command and the second rotational speed command. The horizontal axis of FIG. 11 represents the value of the first rotational speed command for motor M1 (see FIG. 1). The vertical axis of FIG. 11 represents the value of the second rotational speed command for motor M1. Values ​​F1 and F2 shown in FIG. 11 are rotational speeds of motor M1 that can reduce power supply harmonic currents by using motor harmonic currents. These values ​​F1 and F2 are stored in advance in control device 60 based on the power supply frequency and the number of poles of motor M1.

[0085] 11 is a function used for converting the first rotation speed command into the second rotation speed command, and is stored in advance in control device 60C (see FIG. 10). Note that instead of the function indicated by broken line G1, a predetermined data table may be set.

[0086] For example, when the first rotation speed command is equal to or greater than (F1-ΔF) and equal to or less than (F1+ΔF), the rotation speed command regulator 61 (see FIG. 10) sets the second rotation speed command to value F1. That is, when the absolute value of the deviation between the first rotation speed command and value F1 is equal to or less than value ΔF, the rotation speed command regulator 61 sets value F1 as the second rotation speed command. Similarly, when the first rotation speed command is equal to or greater than (F2-ΔF) and equal to or less than (F2+ΔF), the rotation speed command regulator 61 (see FIG. 10) sets the second rotation speed command to value F2. This makes it possible to expand the operating range (the range of the first rotation speed command) in which the motor harmonic current can cancel out the power supply harmonic current.

[0087] Furthermore, when the absolute value of the deviation between the first rotation speed command and the values ​​F1 and F2 is greater than the value ΔF, the rotation speed command regulator 61 sets the second rotation speed command to a value equal to the first rotation speed command. This prevents the operation of equipment such as an air conditioner from deviating from its original purpose (air conditioning). For example, when the room temperature is high in summer, it becomes possible to prioritize cooling operation over reducing the power supply harmonic current, and drive the compressor motor M1 at high speed.

[0088] <Effects> According to the second embodiment, it is possible to expand the operating range (range of the first rotation speed command) in which the power supply harmonic current can be canceled out by the motor harmonic current. Furthermore, instead of performing a process to reduce the power supply harmonic current uniformly, it is possible to appropriately set the second rotation speed command based on the deviation between the first rotation speed command and the values ​​F1 and F2.

[0089] Third Embodiment In the third embodiment, an air conditioner W1 (see FIG. 12) including the power conversion device 100 (see FIG. 1) configured as described in the first embodiment will be described. Note that the configuration and processing content of the power conversion device 100 (see FIG. 1) are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0090] FIG. 12 is a configuration diagram of an air conditioner W1 according to a third embodiment. The solid arrows in FIG. 12 indicate the flow of refrigerant in the heating cycle. The dashed arrows in FIG. 12 indicate the flow of refrigerant in the cooling cycle. The air conditioner W1 is a device that performs air conditioning, such as cooling and heating. As shown in FIG. 12 , the air conditioner W1 includes, as components provided in the outdoor unit U1, a compressor 91 (device), an outdoor heat exchanger 92, an outdoor fan 93, an expansion valve 94, and a four-way valve 95. The air conditioner W1 also includes, as components provided in the indoor unit U2, an indoor heat exchanger 96 and an indoor fan 97.

[0091] Although not shown in Fig. 12, the air conditioner W1 is equipped with the power conversion device 100 (see Fig. 1) described in the first embodiment. The power conversion device 100 (see Fig. 1) is mounted on a circuit board (not shown) of the outdoor unit U1.

[0092] The compressor 91 is a "device" that compresses a low-temperature, low-pressure gas refrigerant and discharges it as a high-temperature, high-pressure gas refrigerant. Although not shown in Fig. 12, an accumulator for separating the refrigerant into gas and liquid is connected to the suction side of the compressor 91. In addition, a motor M1 that is a drive source of the compressor 91 is electrically connected to the output side of the inverter circuit 30 (see Fig. 1) of the power conversion device 100 (see Fig. 1).

[0093] The outdoor heat exchanger 92 is a heat exchanger in which heat is exchanged between the refrigerant flowing through its heat transfer tubes and the outside air sent in from the outdoor fan 93. The outdoor fan 93 is a fan that sends the outside air to the outdoor heat exchanger 92. The outdoor fan 93 has an outdoor fan motor 93a that serves as a drive source, and is installed near the outdoor heat exchanger 92.

[0094] The expansion valve 94 is a valve that reduces the pressure of the refrigerant condensed in the "condenser" (one of the outdoor heat exchanger 92 and the indoor heat exchanger 96). The refrigerant reduced in pressure by the expansion valve 94 is guided to the "evaporator" (the other of the outdoor heat exchanger 92 and the indoor heat exchanger 96). The indoor heat exchanger 96 is a heat exchanger that exchanges heat between the refrigerant flowing through its heat transfer tube (not shown) and indoor air (air in the air-conditioned room) sent in by an indoor fan 97. The indoor fan 97 is a fan that sends indoor air to the indoor heat exchanger 96. The indoor fan 97 is equipped with an indoor fan motor 97a that serves as a drive source, and is installed near the indoor heat exchanger 96.

[0095] The four-way valve 95 switches the refrigerant flow path depending on the operating mode of the air conditioner W1. For example, during cooling operation (see the dashed arrow in FIG. 12 ), the refrigerant circulates in the refrigerant circuit Q1 sequentially through the compressor 91, the outdoor heat exchanger 92 (condenser), the expansion valve 94, and the indoor heat exchanger 96 (evaporator). During heating operation (see the solid arrow in FIG. 12 ), the refrigerant circulates in the refrigerant circuit Q1 sequentially through the compressor 91, the indoor heat exchanger 96 (condenser), the expansion valve 94, and the outdoor heat exchanger 92 (evaporator). Air that has exchanged heat with the refrigerant flowing through the indoor heat exchanger 96 is then blown out of the indoor unit U2 into the air-conditioned room.

[0096] <Effects> According to the third embodiment, the air conditioner W1 is equipped with the power conversion device 100 (see Figure 1) having the same configuration as in the first embodiment, so it is possible to provide a highly reliable air conditioner W1 that can reduce power supply harmonic currents.

[0097] <<Modifications>> Although the power conversion device 100 and the air conditioner W1 according to the present disclosure have been described in the above embodiments, they are not limited to these descriptions and various modifications can be made. For example, in the first embodiment, the converter circuit 10 (see FIG. 1) is described as including a diode bridge circuit 11 (see FIG. 1) for full-wave rectification, but this is not limited thereto. For example, the converter circuit may include a voltage doubler rectifier circuit. Furthermore, a switching type converter circuit may be used. The same can be said for the second embodiment.

[0098] In the first embodiment, the case where there is one smoothing capacitor 13 (see FIG. 1) has been described, but this is not limiting. That is, the smoothing capacitor may be formed by a plurality of capacitors (not shown) connected in series, parallel, or series-parallel. The same can be said for the second embodiment.

[0099] Furthermore, in each embodiment, the control device 60 reduces power supply harmonic currents using motor harmonic currents. However, other methods for reducing power supply harmonic currents may be used in combination as appropriate. Furthermore, in the first embodiment, a case where the power supply frequency is 60 Hz and the motor M1 has six poles is described as an example. However, this is not limiting. That is, the power conversion device 100 may be used under conditions of other power supply frequencies (e.g., 50 Hz). Furthermore, the motor M1 may have other numbers of poles, such as four or eight. The same applies to the second embodiment.

[0100] In the third embodiment (see FIG. 12 ), the power conversion device 100 is connected to the motor M1 of the compressor 91, but the present invention is not limited to this. For example, the power conversion device 100 may be connected to the outdoor fan motor 93 a. Furthermore, the power conversion device 100 may be connected to the motor M1 of the compressor 91, and the power conversion device 100 may be connected to the outdoor fan motor 93 a.

[0101] Furthermore, in the third embodiment (see FIG. 12 ), a configuration in which the air conditioner W1 includes a four-way valve 95 has been described, but this is not limiting. That is, the four-way valve 95 may be omitted as appropriate to configure an air conditioner dedicated to cooling or heating. Furthermore, the third embodiment (see FIG. 12 ) can be applied to various types of air conditioners, such as commercial air conditioners and multi-air conditioners for buildings, in addition to room air conditioners. Furthermore, each embodiment can also be applied to other devices such as water heaters and refrigerators. Furthermore, each embodiment can be combined as appropriate. For example, the second embodiment (see FIGS. 10 and 11 ) and the third embodiment (see FIG. 12 ) can be combined.

[0102] Furthermore, each embodiment has been described in detail to clearly explain the present disclosure, and is not necessarily limited to having all of the described configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. Furthermore, the above-described mechanisms and configurations are those considered necessary for explanation, and do not necessarily represent all mechanisms and configurations of the product.

[0103] REFERENCE SIGNS LIST 10 Converter circuit 11 Diode bridge circuit 12 DC reactor 13 Smoothing capacitor 20 DC voltage detection unit 30 Inverter circuit 41, 42 Power supply current detection unit 51, 52 Motor current detection unit 60, 60C Control device (control unit) 61 Rotation speed command regulator 70 Gate drive circuit 80 DC line current detection unit 90 DC reactor voltage detection unit 91 Compressor (equipment) 92 Outdoor heat exchanger 93 Outdoor fan 93a Outdoor fan motor 94 Expansion valve 95 Four-way valve 96 Indoor heat exchanger 97 Indoor fan 97a Indoor fan motor 100, 100A, 100B Power conversion device E1 AC power supply HR, HS, HT Wiring (connecting line) K1, K2 DC line M1 Motor U1 Outdoor unit U2 Indoor unit W1 Air conditioner

Claims

1. A power conversion device comprising: a converter circuit that converts an AC voltage applied from an AC power supply into a DC voltage; an inverter circuit that converts the DC voltage on the output side of the converter circuit into an AC voltage and applies the AC voltage to a motor; and a control unit that controls the inverter circuit, wherein the control unit adjusts the rotational speed and current phase of the motor so as to reduce the power supply harmonic current associated with the power conversion of the converter circuit by the motor harmonic current accompanying the driving of the inverter circuit and the motor.

2. The power conversion device according to claim 1, further comprising a power supply current detection unit that detects a power supply current flowing through a connection line between the AC power supply and the converter circuit, wherein the control unit changes the current phase of the motor while driving the motor at a predetermined rotational speed, and adjusts the current phase of the motor so as to reduce a harmonic component of the detection value based on the detection value of the power supply current detection unit.

3. The power conversion device according to claim 1, further comprising a DC line current detection unit that detects a current flowing through a DC line on the output side of the converter circuit, wherein the control unit changes the current phase of the motor while driving the motor at a predetermined rotational speed, and adjusts the current phase of the motor so as to reduce a harmonic component of the detection value based on the detection value of the DC line current detection unit.

4. The power conversion device according to claim 1, further comprising a DC reactor voltage detection unit that detects a voltage between terminals of a DC reactor provided on a DC line on the output side of the converter circuit, wherein the control unit changes the current phase of the motor while driving the motor at a predetermined rotational speed, and adjusts the current phase of the motor so as to reduce a harmonic component of the detection value based on the detection value of the DC reactor voltage detection unit.

5. The power conversion device according to claim 1, wherein the rotational speed of the motor when reducing the power supply harmonic current by the motor harmonic current is set based on the frequency of the AC power supply and the number of poles of the motor.

6. The control unit converts a first rotational speed command of the motor based on the operating conditions of the device having the motor as a drive source into a second rotational speed command, drives the motor based on the second rotational speed command, and when the absolute value of the deviation between the rotational speed of the motor capable of reducing the power supply harmonic current by the motor harmonic current and the first rotational speed command is equal to or less than a predetermined value, the control unit sets the rotational speed as the second rotational speed command. The power conversion device according to claim 1, characterized in that.

7. The control unit converts a first rotational speed command of the motor based on the operating conditions of the device having the motor as a drive source into a second rotational speed command, drives the motor based on the second rotational speed command, and when the absolute value of the deviation between the rotational speed of the motor capable of reducing the power supply harmonic current by the motor harmonic current and the first rotational speed command is greater than a predetermined value, the control unit sets the same value as the first rotational speed command as the second rotational speed command. The power conversion device according to claim 1, characterized in that.

8. An air conditioner comprising the power conversion device according to any one of claims 1 to 5, and further comprising a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, wherein the motor is a drive source of the compressor.

9. An air conditioner comprising the power conversion device according to claim 6 or claim 7, and further comprising a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, wherein the device is the compressor.

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