Motor drive device, blower, air conditioner, and motor drive method

Abstract

Provided is a motor drive device comprising a first current sensor that detects a first current signal indicating a current flowing through a first motor, a second current sensor that detects a second current signal indicating a current flowing through a second motor, the first motor and the second motor being connected in parallel, an electric power converter that supplies electric power to the first motor and the second motor, and a controller that controls the electric power converter using a speed command value and controls the frequencies of the first motor and the second motor, wherein the controller: uses a first estimated phase, which is an estimated value of the phase of the first motor, and the first current signal to obtain a first q-axis current estimated value, which is an estimated value of a torque current of the first motor; uses a second estimated phase, which is an estimated value of the phase of the second motor, and the second current signal to obtain a second q-axis current estimated value, which is an estimated value of a torque current of the second motor; and compensates the speed command value, a q-axis current command value of the first motor, or the first estimated phase on the basis of an estimated current difference between the first q-axis current estimated value and the second q-axis current estimated value, thereby reducing the phase difference between the first motor and the second motor.

Description

[Technical Field]

[0001] The present disclosure relates to a motor drive device for driving a plurality of motors, a blower, an air conditioner, and a motor drive method. [Background technology]

[0002] Conventionally, a drive device that controls magnetic flux current commands to reduce the phase difference between the two synchronous motors is known as a device for driving two synchronous motors, a main-side synchronous motor and a sub-side synchronous motor, connected in parallel to a single inverter (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-106499 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because magnetic flux current cannot generate torque, the drive device disclosed in Patent Document 1 cannot generate torque in the two synchronous motors to finely adjust their rotation even if a phase difference occurs between them, and therefore cannot reduce the phase difference. If the two synchronous motors continue to operate with a phase difference between them, the phase current of the sub-side synchronous motor will become unstable, and the operation stability of the sub-side synchronous motor will be impaired.

[0005] The present disclosure has been made to solve the above-mentioned problems, and provides a motor drive device, a blower, an air conditioner, and a motor drive method that improve the operational stability of the auxiliary motor of two motors connected in parallel to one power converter. [Means for solving the problem]

[0006] A motor drive device according to the present disclosure is a motor drive device that drives a first motor and a second motor, the motor drive device comprising: a first current sensor that detects a first current signal that indicates a current flowing through the first motor; a second current sensor that detects a second current signal that indicates a current flowing through the second motor; a power converter that supplies power to the first motor and the second motor, to which the first motor and the second motor are connected in parallel; and a controller that controls the power converter using a speed command value and controls the frequencies of the first motor and the second motor, the controller comprising: a coordinate converter that calculates a first q-axis current estimate that is an estimate of a torque current of the first motor using a first estimated phase that is an estimate of a phase of the first motor and the first current signal, and that calculates a second q-axis current estimate that is an estimate of a torque current of the second motor using a second estimated phase that is an estimate of a phase of the second motor and the second current signal; ,before and a compensation means for compensating for the first estimated phase to reduce the phase difference between the first motor and the second motor.

[0007] The blower according to the present disclosure has a first motor connected to a first fan, a second motor connected to a second fan, and the above-described motor drive device that drives the first motor and the second motor.

[0008] The air conditioning apparatus according to the present disclosure comprises a refrigerant circuit in which a compressor, a heat source side heat exchanger, an expansion valve, and a load side heat exchanger are connected via refrigerant piping, and in which a refrigerant circulates, and the above-mentioned blower that supplies air to at least one of the heat source side heat exchanger and the load side heat exchanger.

[0009] A motor drive method according to the present disclosure is a motor drive method for a motor drive device including a first motor and a second motor connected in parallel, the motor drive device having a power converter supplying power to the first motor and the second motor, a first current sensor detecting a first current signal indicating a current flowing through the first motor, and a second current sensor detecting a second current signal indicating a current flowing through the second motor, the motor drive method controlling the power converter using a speed command value and controlling the frequencies of the first motor and the second motor, the motor drive method including the steps of: determining a first q-axis current estimate that is an estimate of a torque current of the first motor using a first estimated phase that is an estimate of a phase of the first motor and the first current signal; determining a second q-axis current estimate that is an estimate of a torque current of the second motor using a second estimated phase that is an estimate of a phase of the second motor and the second current signal; and calculating a second q-axis current estimate that is an estimate of a torque current of the second motor based on an estimated current difference between the first q-axis current estimate and the second q-axis current estimate. ,before and compensating for the first estimated phase to reduce the phase difference between the first motor and the second motor. [Effects of the Invention]

[0010] According to the present disclosure, the phase difference between the first motor and the second motor is reduced by compensating the speed command value, the q-axis current command value of the first motor, or the phase of the first motor based on the estimated current difference between the q-axis current estimate value of the first motor and the q-axis current estimate value of the second motor. This eliminates the phase shift of the second motor relative to the first motor. This suppresses the occurrence of hunting in the phase current of the second motor, improving the operational stability of the second motor. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of a configuration of a motor drive device according to a first embodiment. [Figure 2] 2 is a diagram illustrating an example of the configuration of the power converter illustrated in FIG. 1. FIG. [Figure 3] 2 is a block diagram showing an example of the configuration of a controller shown in FIG. 1. FIG. [Figure 4] 4 is a hardware configuration diagram showing an example of the configuration of a controller shown in FIG. 3. FIG. [Figure 5] 4 is a hardware configuration diagram showing another example of the configuration of the controller shown in FIG. 3. FIG. [Figure 6] 4 is a flowchart showing an operation procedure of the motor drive device according to the first embodiment. [Figure 7] 10 is a graph showing a waveform of the frequency of the second motor under control of the comparative example. [Figure 8] 10 is a graph showing waveforms of phase currents of a second motor under control of a comparative example. [Figure 9] 6 is a graph showing a waveform of the frequency of the second motor under the control of the first embodiment. [Figure 10] 6 is a graph showing waveforms of phase currents of a second motor under control according to the first embodiment. [Figure 11] FIG. 10 is a block diagram showing an example of the configuration of a controller of a motor drive device according to a second embodiment. [Figure 12] FIG. 11 is a block diagram showing an example of the configuration of a controller of a motor drive device according to a third embodiment. [Figure 13] FIG. 10 is a refrigerant circuit diagram showing an example of the configuration of an air conditioner according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment 1 In the first embodiment, the q-axis current of each of a plurality of motors is estimated, and the speed command value is compensated based on the estimation result, thereby stabilizing the synchronous operation of the plurality of motors.

[0013] The configuration of a motor drive device according to the first embodiment will be described. FIG. 1 is a diagram showing an example of the configuration of a motor drive device according to the first embodiment. As shown in FIG. 1, the motor drive device 1 is connected to a first motor 2a and a second motor 2b. The first motor 2a has a first fan 4a coupled to its rotation shaft. The second motor 2b has a second fan 4b coupled to its rotation shaft.

[0014] The first fan 4a is a load for the first motor 2a. The second fan 4b is a load for the second motor 2b. The first motor 2a and the second motor 2b are AC synchronous motors. The first motor 2a and the second motor 2b are, for example, permanent magnet (PM) synchronous motors.

[0015] The motor drive device 1 includes a power converter 8, a first current sensor 3a, a second current sensor 3b, and a controller 5. A first motor 2a is connected to the power converter 8 via a first conductor 6a. A first current sensor 3a that detects the motor current flowing through the first motor 2a is provided on the first conductor 6a.

[0016] The first conductor 6a branches off between the power converter 8 and the first current sensor 3a to form a second conductor 6b. A second motor 2b is connected to the second conductor 6b. The power converter 8 connects the first motor 2a and the second motor 2b in parallel via the first conductor 6a and the second conductor 6b. A second current sensor 3b is provided on the second conductor 6b to detect the motor current flowing through the second motor 2b. Each of the first conductor 6a and the second conductor 6b is composed of three wires to carry a three-phase motor current consisting of U-phase, V-phase, and W-phase.

[0017] The controller 5 controls the power converter 8 using a speed command value ω* input from an external higher-level device (not shown), thereby controlling the frequencies of the first motor 2a and the second motor 2b. The speed command value ω* determines the frequencies of the first motor 2a and the second motor 2b. The voltages applied to the first motor 2a and the second motor 2b are controlled by PWM (Pulse Width Modulation) signals output from the controller 5 via signal lines 7.

[0018] The first current sensor 3a detects a current signal Iu1 indicating the U-phase motor current of the first motor 2a and a current signal Iw1 indicating the W-phase motor current of the first motor 2a. The second current sensor 3b detects a current signal Iu2 indicating the U-phase motor current of the second motor 2b and a current signal Iw2 indicating the W-phase motor current of the second motor 2b.

[0019] Fig. 2 is a diagram showing an example of the configuration of the power converter shown in Fig. 1. Under the control of the controller 5, the power converter 8 supplies power corresponding to the speed command value ω* to the first motor 2a and the second motor 2b.

[0020] The power converter 8 includes a rectifier circuit 54 connected to an AC power supply 9, and an inverter circuit 50. The inverter circuit 50 includes a plurality of switching elements 51u to 53u and 51d to 53d that convert the DC voltage output from the rectifier circuit 54 into a three-phase AC voltage and supply it to the first motor 2a and the second motor 2b. The rectifier circuit 54 converts the AC voltage supplied from the AC power supply 9 into a DC voltage. The rectifier circuit 54 is, for example, a diode bridge circuit. As shown in FIG. 2, a capacitor 55 may be connected between the DC buses. The capacitor 55 smooths and stabilizes the DC voltage.

[0021] In the inverter circuit 50, a pair of switching elements is provided for each of the U, V, and W phases. For the U phase, an upper arm switching element 51u and a lower arm switching element 51d are connected in series. The connection point between switching element 51u and switching element 51d is connected to a U-phase input terminal of the first motor 2a via a first conductor 6a, and is also connected to a U-phase input terminal of the second motor 2b via the first conductor 6a and a second conductor 6b.

[0022] For the V phase, switching element 52u of the upper arm and switching element 52d of the lower arm are connected in series. A connection point between switching element 52u and switching element 52d is connected to a V-phase input terminal of first motor 2a via first conductor 6a and to a V-phase input terminal of second motor 2b via first conductor 6a and second conductor 6b. For the W phase, switching element 53u of the upper arm and switching element 53d of the lower arm are connected in series. A connection point between switching element 53u and switching element 53d is connected to a W-phase input terminal of first motor 2a via first conductor 6a and to a W-phase input terminal of second motor 2b via first conductor 6a and second conductor 6b.

[0023] Each of the switching elements 51u to 53u and 51d to 53d is provided with a backflow prevention element in anti-parallel to the switching element. Each switching element is, for example, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

[0024] These multiple switching elements 51u to 53u and 51d to 53d perform switching operations based on a PWM control method. The multiple switching elements 51u to 53u and 51d to 53d perform switching operations in accordance with PWM signals input to their gate electrodes from the controller 5. Through this switching operation, the inverter circuit 50 converts the DC voltage into a three-phase AC voltage of an appropriate frequency for driving the two motors, the first motor 2a and the second motor 2b, and supplies the three-phase AC voltage to the two motors.

[0025] 2 shows a case where power converter 8 converts a single-phase AC voltage supplied from AC power supply 9 into a DC voltage, but the supplied AC voltage may be three-phase. Also, inverter circuit 50 may be connected to a DC power supply such as a battery, and in this case, generates a three-phase AC voltage using the DC voltage supplied from the DC power supply.

[0026] Next, the configuration of the controller 5 will be described with reference to Fig. 3. Fig. 3 is a block diagram showing an example of the configuration of the controller shown in Fig. 1. The controller 5 has a speed controller 10, a current controller 11, an inverse coordinate converter 12, a PWM signal generating means 13, a coordinate converter 14a, a coordinate converter 14b, a position and speed estimator 15a, a position and speed estimator 15b, and a compensation means 16. The controller 5 also has subtractors 21 to 25.

[0027] The coordinate converter 14a calculates a first current signal (Iu1, Iw1, Iv1) using the current signals Iu1 and Iw1 detected by the first current sensor 3a and the relational expression Iu1+Iv1+Iw1=0. The coordinate converter 14a receives an estimated phase θ1, which is an estimate of the phase of the first motor 2a, from the position and speed estimator 15a. The coordinate converter 14a calculates d-axis and q-axis current values ​​(Id1, Iq1) using the first current signals (Iu1, Iv1, Iw1) and the estimated phase θ1. The d-axis current estimate Id1 is an estimate of the d-axis current corresponding to the excitation current of the first motor 2a. The q-axis current estimate Iq1 is an estimate of the q-axis current corresponding to the torque current of the first motor 2a.

[0028] The coordinate converter 14a outputs the d-axis current estimated value Id1 to the subtractor 24 and the position and speed estimator 15a. The coordinate converter 14a outputs the q-axis current estimated value Iq1 to the subtractors 23 and 25 and the position and speed estimator 15a.

[0029] The coordinate converter 14b calculates a second current signal (Iu2, Iw2, Iv2) using the current signals Iu2 and Iw2 detected by the second current sensor 3b and the relational expression Iu2+Iv2+Iw2=0. The coordinate converter 14b receives an estimated phase θ2, which is an estimate of the phase of the second motor 2b, from the position and speed estimator 15b. The coordinate converter 14b calculates d-axis and q-axis current values ​​(Id2, Iq2) using the second current signals (Iu2, Iv2, Iw2) and the estimated phase θ2. The d-axis current estimate Id2 is an estimate of the d-axis current corresponding to the excitation current of the second motor 2b. The q-axis current estimate Iq2 is an estimate of the q-axis current corresponding to the torque current of the second motor 2b.

[0030] The coordinate converter 14b outputs the d-axis current estimated value Id2 to the position and speed estimator 15b, and outputs the q-axis current estimated value Iq2 to the subtractor 25 and the position and speed estimator 15b.

[0031] The position and speed estimator 15a receives the d-axis and q-axis current values ​​(Id1, Iq1) from the coordinate converter 14a and the d-axis and q-axis voltage command values ​​(Vd*, Vq*) from the current controller 11. The position and speed estimator 15a uses the d-axis and q-axis current estimated values ​​Id1 and Iq1, and the d-axis and q-axis voltage command values ​​Vd* and Vq* to determine an estimated speed ω1, which is an estimate of the angular speed of the first motor 2a, and an estimated phase θ1 of the first motor 2a. The position and speed estimator 15a outputs the estimated phase θ1 to the inverse coordinate converter 12 and the coordinate converter 14a. The position and speed estimator 15a outputs the estimated speed ω1 to the subtractor 22.

[0032] The position and speed estimator 15b receives the d-axis and q-axis current values ​​(Id2, Iq2) from the coordinate converter 14b and the d-axis and q-axis voltage command values ​​(Vd*, Vq*) from the current controller 11. The position and speed estimator 15b uses the d-axis and q-axis current estimated values ​​Id2 and Iq2, and the d-axis and q-axis voltage command values ​​Vd* and Vq* to calculate an estimated speed ω2 of the second motor 2b and an estimated phase θ2 of the second motor 2b. The position and speed estimator 15b outputs the estimated phase θ2 to the coordinate converter 14b. Although FIG. 3 shows that the position and speed estimator 15b outputs the estimated speed ω2, the estimated speed ω2 is not used in the control of the first embodiment. Therefore, the position and speed estimator 15b does not need to calculate the estimated speed ω2.

[0033] When the q-axis current estimated value Iq1 is input from the coordinate converter 14a and the q-axis current estimated value Iq2 is input from the coordinate converter 14b, the subtractor 25 calculates (Iq2 - Iq1) and outputs the calculation result to the compensation means 16. Hereinafter, Iq2 - Iq1 = ΔIq, and ΔIq is referred to as the inter-motor current difference. The subtractor 25 outputs the value of the inter-motor current difference ΔIq to the compensation means 16.

[0034] When the speed compensation value ωcomp is input from the compensation means 16, the subtractor 21 subtracts the speed compensation value ωcomp from the speed command value ω* to obtain a corrected speed command value ω**. The subtractor 21 outputs the corrected speed command value ω** to the subtractor 22. When the corrected speed command value ω** is input from the subtractor 21 and the estimated speed ω1 is input from the position / speed estimator 15a, the subtractor 22 obtains a speed difference Δω which is the difference between the corrected speed command value ω** and the estimated speed ω1, and outputs the value of the speed difference Δω to the speed controller 10.

[0035] When the speed difference Δω is input from the subtractor 22, the speed controller 10 performs feedback control to integrate the output so that the speed difference Δω becomes zero. Specifically, the speed controller 10 performs PI (Proportional Integral) control to determine a q-axis current command value Iq* that reduces the speed difference Δω. The q-axis current command value Iq* is a command value for the q-axis current. The speed controller 10 outputs the q-axis current command value Iq* to the subtractor 23.

[0036] When the q-axis current command value Iq* is input from the speed controller 10 and the q-axis current estimation value Iq1 is input from the coordinate converter 14a, the subtractor 23 subtracts the q-axis current estimation value Iq1 from the q-axis current command value Iq* to obtain the q-axis current difference ΔIq1. That is, the subtractor 23 calculates the calculation formula (ΔIq1=Iq*-Iq1). The subtractor 23 outputs the value of the q-axis current difference ΔIq1 to the current controller 11.

[0037] When the subtractor 24 receives the d-axis current command value Id*, which is a command value for the d-axis current, and the d-axis current estimate value Id1 from the coordinate converter 14a, the subtractor 24 subtracts the d-axis current estimate value Id1 from the d-axis current command value Id* to obtain the d-axis current difference ΔId1. That is, the subtractor 24 performs calculations using the formula (ΔId1=Id*-Id1). The subtractor 24 outputs the d-axis current difference ΔId1 to the current controller 11. In the first embodiment, the d-axis current command value Id* is a constant value. The d-axis current command value Id* may be output from an electric circuit (not shown), such as a storage, provided within the controller 5, or may be input from outside the controller 5.

[0038] When the current controller 11 receives the q-axis current difference ΔIq1 from the subtractor 23 and the d-axis current difference ΔId1 from the subtractor 24, it performs feedback control to integrate the output so that the q-axis current difference ΔIq1 and the d-axis current difference ΔId1 each become zero. Specifically, the current controller 11 performs PI control to determine dq-axis voltage command values ​​(Vd*, Vq*) that reduce the q-axis current difference ΔIq1 and the d-axis current difference ΔId1, respectively. Vd* is the d-axis voltage command value, and Vq* is the q-axis voltage command value. The current controller 11 outputs the dq-axis voltage command values ​​(Vd*, Vq*) to the position and speed estimator 15a, the position and speed estimator 15b, and the inverse coordinate converter 12.

[0039] The inverse coordinate converter 12 receives the d- and q-axis voltage command values ​​(Vd*, Vq*) from the current controller 11 and receives the estimated phase θ1 of the first motor 2a from the position and speed estimator 15a. The inverse coordinate converter 12 converts the d- and q-axis voltage command values ​​(Vd*, Vq*) into three-phase voltages (Vu, Vv, Vw) using the estimated phase θ1. The inverse coordinate converter 12 outputs the three-phase voltages (Vu, Vv, Vw) to the PWM signal generating means 13.

[0040] The PWM signal generating means 13 generates a PWM signal when the three-phase voltages (Vu, Vv, Vw) are input from the inverse coordinate converter 12 and the estimated phase θ1 is input from the position and speed estimator 15a. The PWM signal generating means 13 outputs the generated PWM signal to the power converter 8.

[0041] When the value of the current difference ΔIq between the motors is input from the subtractor 25, the compensation means 16 calculates a speed compensation value ωcomp that eliminates the phase shift between the motors. For example, the compensation means 16 calculates a transient change amount like a high-pass filter based on the value of the current difference ΔIq between the motors, and amplifies the calculated change amount to calculate the speed compensation value ωcomp. The compensation means 16 outputs the speed compensation value ωcomp to the subtractor 21.

[0042] The operation of the compensation means 16 is expressed, for example, by the transfer function G1(s) of equation (1). The transfer function G1(s) is formed by a combination of a high-pass filter having a determined time constant T and an amplifier having a determined gain K.

[0043]

number

[0044] The polarity of the speed compensation value ωcomp output from the compensation means 16 is positive when (Iq2-Iq1) on the right side of equation (1) is positive. In other words, when the inter-motor current difference ΔIq (=Iq2-Iq1) is positive, the speed compensation value ωcomp is also positive.

[0045] The operation of the compensation unit 16 will now be described in detail. For example, when the inter-motor current difference ΔIq is positive, the q-axis current estimate Iq2 is greater than the q-axis current estimate Iq1. In this case, it is assumed that a larger load torque is transiently applied to the second motor 2b than to the first motor 2a. Because the same voltage is applied to these two motors, it can be assumed that the rotational phase of the second motor 2b transiently changes in a delayed direction. The phase delay can be relatively eliminated by transiently reducing the frequency command of the inverter circuit 50. Therefore, the compensation unit 16 outputs a positive speed compensation value ωcomp to the subtractor 21. This reduces the corrected speed command value ω**, and the output frequency of the inverter circuit 50 decreases. Because the first motor 2a has a smaller load than the second motor 2b, the phase change is relatively smaller in response to fluctuations in the output frequency of the inverter circuit 50. As a result, the difference between the phase of the second motor 2b and the phase of the first motor 2a becomes smaller, and the phase lag of the second motor 2b is eliminated.

[0046] On the other hand, when the inter-motor current difference ΔIq is negative, the q-axis current estimate Iq2 is smaller than the q-axis current estimate Iq1. In other words, the load torque on the second motor 2b is relatively smaller than the load torque on the first motor 2a. In this case, it can be inferred that the phase of the second motor 2b is relatively advanced. Therefore, the compensation unit 16 outputs a negative speed compensation value ωcomp to the subtractor 21. This causes a transient increase in the corrected speed command value ω**, increasing the output frequency of the inverter circuit 50. Because the second motor 2b has a smaller load than the first motor 2a, its phase change is relatively smaller in response to fluctuations in the output frequency of the inverter circuit 50. As a result, the difference between the phase of the second motor 2b and the phase of the first motor 2a becomes smaller, and the phase advance of the second motor 2b is eliminated. The compensation unit 16 continuously performs the above frequency compensation operation at regular intervals to stabilize the synchronous operation of the second motor 2b.

[0047] In this way, in the first embodiment, the controller 5 controls the frequency of the first motor 2a by position sensorless vector control, and performs compensation control on the frequency of the second motor 2b by the compensation means 16. The first motor 2a corresponds to the main motor that serves as the reference for speed control. The second motor 2b corresponds to the sub-motor that operates in synchronization with the main motor.

[0048] 3 shows two coordinate conversion means, such as coordinate converters 14a and 14b, as separate structures, but a single coordinate conversion means having the functions of coordinate converters 14a and 14b may be provided in controller 5. Also, while FIG. 3 shows position and velocity estimators 15a and 15b as separate structures, a single position and velocity estimator having the functions of position and velocity estimators 15a and 15b may be provided in controller 5.

[0049] Furthermore, in the first embodiment, the first current sensor 3a and the second current sensor 3b each detect two-phase motor currents, U-phase and W-phase, out of the three-phase motor current, but the combination of the detected two-phase motor currents is not limited to U-phase and W-phase. Furthermore, the first current sensor 3a and the second current sensor 3b each detect two-phase motor currents out of the three-phase motor current, but the motor current for each of the three phases may be detected.

[0050] 3, the subtractor 23 may be provided in the speed controller 10, and the subtractors 23 and 24 may be provided in the speed controller 10 or the current controller 11. The subtractors 21 and 25 may be provided in the compensation means 16.

[0051] Here, an example of hardware of the controller 5 shown in Fig. 3 will be described. Fig. 4 is a hardware configuration diagram showing an example of the configuration of the controller shown in Fig. 3. When the various functions of the controller 5 are executed by hardware, the controller 5 shown in Fig. 3 is configured by a processing circuit 80 as shown in Fig. 4. The functions of the speed controller 10, current controller 11, inverse coordinate converter 12, PWM signal generating means 13, coordinate converter 14a, coordinate converter 14b, position and speed estimator 15a, position and speed estimator 15b, compensation means 16, and subtractors 21 to 25 shown in Fig. 3 are realized by the processing circuit 80.

[0052] When each function is performed by hardware, the processing circuit 80 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. Each function of the speed controller 10, the current controller 11, the inverse coordinate converter 12, the PWM signal generating means 13, the coordinate converters 14a, 14b, the position and speed estimators 15a, 15b, the compensation means 16, and the subtractors 21 to 25 may be realized by separate processing circuits 80. Also, each function of the speed controller 10, the current controller 11, the inverse coordinate converter 12, the PWM signal generating means 13, the coordinate converters 14a, 14b, the position and speed estimators 15a, 15b, the compensation means 16, and the subtractors 21 to 25 may be realized by a single processing circuit 80.

[0053] Another example of hardware for the controller 5 shown in FIG. 3 will now be described. FIG. 5 is a hardware configuration diagram showing another example of the configuration of the controller shown in FIG. 3. When the various functions of the controller 5 are executed by software, the controller 5 shown in FIG. 3 is configured with a processor 91 such as a CPU and a memory 92, as shown in FIG. 5. The functions of the speed controller 10, the current controller 11, the inverse coordinate converter 12, the PWM signal generating means 13, the coordinate converters 14a, 14b, the position and speed estimators 15a, 15b, the compensation means 16, and the subtractors 21 to 25 are realized by the processor 91 and the memory 92. FIG. 5 shows that the processor 91 and the memory 92 are connected to each other via a bus 93 so as to be able to communicate with each other.

[0054] When each function is performed by software, the functions of the speed controller 10, current controller 11, inverse coordinate converter 12, PWM signal generating means 13, coordinate converters 14a, 14b, position / speed estimator 15a, position / speed estimator 15b, compensation means 16, and subtractors 21 to 25 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in memory 92. The processor 91 realizes the functions of each means by reading and executing the programs stored in memory 92.

[0055] The memory 92 may be a non-volatile semiconductor memory such as a read only memory (ROM), a flash memory, an erasable programmable read only memory (EPROM), or an electrically erasable programmable read only memory (EEPROM). Alternatively, a volatile semiconductor memory such as a random access memory (RAM) may be used as the memory 92. Furthermore, the memory 92 may be a removable recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disc (CD), a mini disc (MD), or a digital versatile disc (DVD).

[0056] Next, a description will be given of a frequency compensation control method for the motor drive device 1 according to the first embodiment. Fig. 6 is a flowchart showing the operation procedure of the motor drive device according to the first embodiment.

[0057] In step S11, the coordinate converter 14a calculates the q-axis current estimate Iq1 of the first motor 2a using the estimated phase θ1 of the first motor 2a and the first current signals (Iu1, Iv1, Iw1). In step S12, the coordinate converter 14b calculates the q-axis current estimate Iq2 of the second motor 2b using the estimated phase θ2 of the second motor 2b and the second current signals (Iu2, Iv2, Iw2). In step S13, the subtractor 25 calculates the inter-motor current difference ΔIq by calculating the formula (ΔIq=Iq2-Iq1) using the q-axis current estimates Iq1 and Iq2.

[0058] In step S14, the compensation means 16 calculates a speed compensation value ωcomp based on the current difference ΔIq between the motors. For example, if the current difference ΔIq between the motors is positive, the compensation means 16 sets the speed compensation value ωcomp to a negative value. If the current difference ΔIq between the motors is negative, the compensation means 16 sets the speed compensation value ωcomp to a positive value. The compensation means 16 outputs the speed compensation value ωcomp to the subtractor 21. The subtractor 21 subtracts the speed compensation value ωcomp from the speed command value ω* and outputs the subtraction result to the subtractor 22.

[0059] 6 shows a procedure in which Iq1 is calculated in step S11 and then Iq2 is calculated in step S12, but steps S11 and S12 may be performed simultaneously. The order of steps S11 and S12 is not limited.

[0060] Next, the effects of the frequency compensation control executed by motor drive device 1 of embodiment 1 will be described with reference to Figs. 7 to 10. Figs. 7 and 8 show the case without frequency compensation control of embodiment 1. Figs. 9 and 10 show the case with frequency compensation control of embodiment 1.

[0061] Fig. 7 is a graph showing the waveform of the frequency of the second motor under the control of the comparative example. Fig. 8 is a graph showing the waveform of the phase current of the second motor under the control of the comparative example. Fig. 9 is a graph showing the waveform of the frequency of the second motor under the control of embodiment 1. Fig. 10 is a graph showing the waveform of the phase current of the second motor under the control of embodiment 1.

[0062] In Figures 7 and 9, the vertical axis represents the rotation speed [r / min] and the horizontal axis represents time [sec]. In Figures 7 and 9, the frequency command f* is the frequency corresponding to the speed command value ω*. f2a is the frequency of the first motor 2a. f2b is the frequency of the second motor 2b. In Figures 8 and 10, the vertical axis represents the phase current [A] and the horizontal axis represents time [sec].

[0063] Without frequency compensation control, the second motor 2b becomes unstable due to electric spring resonance, and the frequency f2b of the second motor 2b behaves unstably relative to the frequency command f*, as shown in Fig. 7. As a result, the phases of the applied voltage and induced voltage become unstable, and as shown by the dashed oval in Fig. 8, the current generated by the potential difference between the applied voltage and induced voltage also becomes unstable.

[0064] On the other hand, when frequency compensation control is enabled, the speed compensation value ωcomp increases or decreases in accordance with the increase or decrease in the q-axis current of the second motor 2b, reducing the phase difference between the first motor 2a and the second motor 2b. Therefore, as shown in FIG. 9, the first motor 2a and the second motor 2b operate so that their respective frequencies match the frequency command f*. As shown in FIG. 9, the rotation speeds of the first motor 2a and the second motor 2b remain constant after six seconds have elapsed. As shown by the dashed oval in FIG. 10, the waveform of the phase current of the second motor 2b stabilizes.

[0065] The motor drive device 1 of the first embodiment includes a power converter 8 to which a first motor 2a and a second motor 2b are connected in parallel via a first conductor 6a and a second conductor 6b, a first current sensor 3a, a second current sensor 3b, and a controller 5 that controls the frequencies of the first motor 2a and the second motor 2b. The first current sensor 3a detects a first current signal indicating the current flowing through the first motor 2a. The second current sensor 3b detects a second current signal indicating the current flowing through the second motor 2b.

[0066] The controller 5 includes coordinate converters 14a and 14b and a compensation unit 16. The coordinate converter 14a calculates a q-axis current estimate Iq1, which is an estimate of the torque current of the first motor 2a, using an estimated phase θ1, which is an estimate of the phase of the first motor 2a, and the first current signals (Iu1, Iv1, Iw1). The coordinate converter 14b calculates a q-axis current estimate Iq2, which is an estimate of the torque current of the second motor 2b, using an estimated phase θ2, which is an estimate of the phase of the second motor 2b, and the second current signals (Iu2, Iv2, Iw2). The compensation unit 16 compensates for the speed command value ω* based on the estimated current difference between the q-axis current estimate Iq1 and the q-axis current estimate Iq2, thereby reducing the phase difference between the first motor 2a and the second motor 2b.

[0067] According to the first embodiment, the speed command value ω* is compensated based on the estimated current difference between the q-axis current estimate Iq1 of the first motor 2a and the q-axis current estimate Iq2 of the second motor 2b, thereby reducing the phase difference between the first motor 2a and the second motor 2b caused by the load. This eliminates the phase shift of the second motor 2b relative to the first motor 2a. This prevents the second motor 2b from experiencing phase current hunting, thereby preventing a dead zone from appearing in the voltage-speed relationship, improving the operational stability of the second motor 2b. This reduces current pulsation in the second motor 2b, enabling operation that is highly robust against disturbances such as loads.

[0068] For example, when the inter-motor current difference ΔIq is positive, the compensation unit 16 decreases the speed command value ω*. When the inter-motor current difference ΔIq is positive, it is considered that the load on the second motor 2b is greater than the load on the first motor 2a. Therefore, when the output frequency of the inverter circuit 50 decreases, the phase of the second motor 2b, which has a relatively greater load, recovers, and the phase lag of the second motor 2b is eliminated. On the other hand, when the inter-motor current difference ΔIq is negative, the compensation unit 16 increases the speed command value ω*. When the inter-motor current difference ΔIq is negative, it is considered that the load on the second motor 2b is less than the load on the first motor 2a. Therefore, when the output frequency of the inverter circuit 50 increases, the phase of the first motor 2a, which has a relatively greater load, recovers, and the phase lead of the second motor 2b is eliminated.

[0069] Furthermore, because a magnetic attraction force acts on the stator of an AC motor according to the current amplitude, magnetic noise can become a problem when the current amplitude increases. In the case of the drive device disclosed in Patent Document 1, a decrease in current stability leads to an increase in current amplitude. As a result, there is a risk of increasing noise and vibration from the AC motor. In contrast, the motor drive device 1 of the first embodiment suppresses current pulsation of the second motor 2b through the above-described frequency compensation control, thereby suppressing the generation of noise and vibration. As a result, multiple motors can be operated with less noise.

[0070] Embodiment 2 In the first embodiment, the method for compensating the frequency of the auxiliary motor is described as compensating for the speed command value, but the method is not limited to the method described in the first embodiment. In the second embodiment, the frequency of the auxiliary motor is compensated for by compensating for the q-axis current command value. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0071] The configuration of a motor drive device according to the second embodiment will be described. FIG. 11 is a block diagram showing an example of the configuration of a controller of the motor drive device according to the second embodiment. As shown in FIG. 11, a controller 5a according to the second embodiment has compensation means 16a that compensates for the q-axis current command value Iq*, instead of the compensation means 16 shown in FIG. 3. The compensation means 16a has the function of the subtractor 25 shown in FIG. 3. The compensation means 16a outputs a q-axis current compensation value Iqcomp, which will be described later, to a subtractor 22.

[0072] In the second embodiment, the coordinate converter 14a outputs the q-axis current estimated value Iq1 to the subtractor 23, the position and speed estimator 15a, and the compensation means 16a. The coordinate converter 14b outputs the q-axis current estimated value Iq2 to the position and speed estimator 15b and the compensation means 16a.

[0073] The configuration of the compensation means 16a will be described in detail. The operation of the compensation means 16a is expressed, for example, by the transfer function G2(s) of equation (2). In equation (2), H(s) represents the transfer function of the speed controller 10.

[0074]

number

[0075] The transfer function shown in equation (2) is equivalent to the transfer function of equation (1) described in embodiment 1, and it is clear that embodiment 2 also achieves the same effects as embodiment 1. The compensation means 16a calculates a q-axis current compensation value Iqcomp that compensates for the q-axis current command value Iq* based on the inter-motor current difference ΔIq in accordance with equation (2). The q-axis current compensation value Iqcomp is output from the compensation means 16a to the subtractor 22. The subtractor 22 subtracts the q-axis current compensation value Iqcomp from the q-axis current command value Iq* output from the speed controller 10. The calculation result by the subtractor 22 becomes a new q-axis current command value. The current controller 11 performs current control using the new q-axis current command value.

[0076] For example, if the inter-motor current difference ΔIq is positive, it can be inferred that the load torque of the second motor 2b is greater than the load torque of the first motor 2a, causing the rotational phase of the second motor 2b to lag. The phase lag can be relatively eliminated by reducing the frequency command of the inverter circuit 50. If the inter-motor current difference ΔIq is positive, the compensation unit 16a sets the q-axis current compensation value Iqcomp to a positive value. The q-axis current command value is reduced by the q-axis current compensation value Iqcomp from the q-axis current command value Iq* output from the speed controller 10. When the q-axis current command value Iq* decreases, the output frequency of the inverter circuit 50 decreases. Because the first motor 2a has a smaller load than the second motor 2b, its phase change is relatively smaller in response to fluctuations in the output frequency of the inverter circuit 50. As a result, the difference between the phase of the second motor 2b and the phase of the first motor 2a decreases, eliminating the phase lag of the second motor 2b.

[0077] On the other hand, if the inter-motor current difference ΔIq is negative, it can be inferred that the load torque of the second motor 2b is smaller than the load torque of the first motor 2a, and that the rotation phase of the second motor 2b is relatively advanced. If the inter-motor current difference ΔIq is negative, the compensation unit 16a sets the q-axis current compensation value Iqcomp to a negative value. The q-axis current command value is increased by the q-axis current compensation value Iqcomp from the q-axis current command value Iq* output from the speed controller 10. When the q-axis current command value Iq* increases, the output frequency of the inverter circuit 50 increases. Because the second motor 2b has a smaller load than the first motor 2a, the phase change is relatively small in response to fluctuations in the output frequency of the inverter circuit 50. As a result, the difference between the phase of the second motor 2b and the phase of the first motor 2a decreases, and the phase advance of the second motor 2b is eliminated.

[0078] In the configuration example shown in Fig. 11, the subtractor 22 may be provided in the compensation means 16a. Furthermore, the operation of the motor drive device 1 of the second embodiment is the same as that of the first embodiment except for the processing of step S14 among the procedures described in the first embodiment with reference to Fig. 6, and therefore detailed description thereof will be omitted.

[0079] According to the second embodiment, the compensation means 16a compensates for the q-axis current command value Iq* of the first motor 2a based on the estimated current difference between the q-axis current estimate value Iq1 and the q-axis current estimate value Iq2, thereby reducing the phase difference between the first motor 2a and the second motor 2b. As a result, the phase shift of the second motor 2b relative to the first motor 2a is eliminated, and the same effect as in the first embodiment can be obtained.

[0080] Embodiment 3 In this third embodiment, the phase shift of the auxiliary motor is eliminated by compensating for the phase of the main motor. In this third embodiment, the same components as those described in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0081] The configuration of a motor drive device according to the third embodiment will be described. FIG. 12 is a block diagram showing an example of the configuration of a controller of a motor drive device according to the third embodiment. As shown in FIG. 12, a controller 5b according to the third embodiment has a subtractor 26. Furthermore, the controller 5b has a compensation means 16b that compensates for the phase of the first motor 2a, instead of the compensation means 16 shown in FIG. 3. The compensation means 16b has the function of the subtractor 25 shown in FIG. 3. The compensation means 16a outputs a phase compensation value θcomp, which will be described later, to the subtractor 26.

[0082] In the third embodiment, the coordinate converter 14a outputs the q-axis current estimated value Iq1 to the subtractor 23, the position and speed estimator 15a, and the compensation means 16b. The coordinate converter 14b outputs the q-axis current estimated value Iq2 to the position and speed estimator 15b and the compensation means 16b. The position and speed estimator 15a outputs the estimated phase θ1 to the subtractor 26.

[0083] The subtractor 26 receives the phase compensation value θcomp from the compensation means 16b and the estimated phase θ1 from the position and speed estimator 15a. The subtractor 26 subtracts the phase compensation value θcomp from the estimated phase θ1 to determine the output voltage phase command θref. The subtractor 26 outputs the output voltage phase command θref to the inverse coordinate converter 12 and the coordinate converter 14a. The inverse coordinate converter 12 receives the output voltage phase command θref from the subtractor 26. The inverse coordinate converter 12 coordinate transforms the dq-axis voltage command values ​​(Vd*, Vq*) into three-phase voltages (Vu, Vv, Vw) using the output voltage phase command θref.

[0084] The configuration of the compensation means 16b will be described in detail. The operation of the compensation means 16b is expressed, for example, by the transfer function G3(s) shown in equation (3). In equation (3), H(s) is the transfer function of the speed controller 10, and k is a constant.

[0085]

number

[0086] The compensation unit 16b determines the difference between the phase of the first motor 2a and the phase of the second motor 2b based on the inter-motor current difference ΔIq and calculates a phase compensation value θcomp corresponding to the determination result. The phase compensation value θcomp is output from the compensation unit 16b to the subtractor 26. The phase compensation value θcomp provides negative compensation for the estimated phase θ1, which corresponds to the output voltage phase command of the inverter circuit 50. In other words, when the inter-motor current difference ΔIq is positive, the phase compensation value θcomp acts to delay the estimated phase θ1, and when the inter-motor current difference ΔIq is negative, the phase compensation value θcomp acts to advance the estimated phase θ1. The compensation unit 16b does not directly compensate for the phase of the second motor 2b, but indirectly compensates for the phase of the second motor 2b by fine-tuning the output voltage phase command of the inverter circuit 50.

[0087] The compensation means 16b calculates a new output voltage phase command θref for the inverter circuit 50 based on the phase difference determined by the inter-motor current difference ΔIq. Then, using the calculated output voltage phase command θref, the compensation means 16b causes the inverse coordinate converter 12 to coordinate-convert the dq-axis voltage command values ​​into three-phase voltages, and causes the coordinate converter 14a to coordinate-convert the first current signals into dq-axis current values.

[0088] For example, if the load on the second motor 2b fluctuates and the inter-motor current difference ΔIq becomes positive, the compensation unit 16b sets the phase compensation value θcomp to a positive value. In this case, the output voltage phase command θref lags the estimated phase θ1 by the phase compensation value θcomp. If the load on the second motor 2b increases, the actual phase of the second motor 2b lags, and the q-axis current estimated value Iq2 increases, the output voltage phase command θref of the inverter circuit 50 decreases. As a result, the increase in the load torque of the second motor 2b can be transiently suppressed.

[0089] On the other hand, if the load on the second motor 2b fluctuates and the inter-motor current difference ΔIq becomes negative, the compensation unit 16b sets the phase compensation value θcomp to a negative value. In this case, the output voltage phase command θref advances the estimated phase θ1 by the phase compensation value θcomp. If the load on the second motor 2b decreases, the actual phase of the second motor 2b advances, and the q-axis current estimated value Iq2 decreases, the output voltage phase command θref of the inverter circuit 50 increases. As a result, the decrease in the load torque of the second motor 2b can be transiently suppressed.

[0090] In the configuration example shown in Fig. 12, the subtractor 26 may be provided in the compensation means 16b. Furthermore, the operation of the motor drive device 1 of the third embodiment is the same as that of the first embodiment except for the processing of step S14 among the procedures described in the first embodiment with reference to Fig. 6, and therefore detailed description thereof will be omitted.

[0091] According to the third embodiment, the compensation means 16b compensates for the estimated phase θ1 of the first motor 2a based on the estimated current difference between the q-axis current estimate value Iq1 and the q-axis current estimate value Iq2, thereby reducing the phase difference between the first motor 2a and the second motor 2b. This eliminates the phase shift of the second motor 2b relative to the first motor 2a, and provides the same effects as those of the first and second embodiments.

[0092] Embodiment 4 In this fourth embodiment, an air conditioner is provided with the motor drive device described in any one of the first to third embodiments. In this fourth embodiment, the same components as those described in the first to third embodiments are given the same reference numerals, and detailed description thereof will be omitted.

[0093] 13 is a refrigerant circuit diagram showing an example of the configuration of an air conditioner according to Embodiment 4. As shown in FIG.

[0094] The heat source side unit 31 has a compressor 33 that compresses and discharges a refrigerant, a four-way valve 34 that switches the flow direction of the refrigerant, a heat source side heat exchanger 35 that exchanges heat between the refrigerant and outside air, an expansion valve 36 that reduces the pressure of the refrigerant and expands it, a blower 37, and a control device 41. The blower 37 supplies outside air to the heat source side heat exchanger 35. The load side unit 32 has a load side heat exchanger 38 that exchanges heat between the refrigerant and air in the space to be air-conditioned. A temperature sensor (not shown) that detects the temperature of the air is provided in the space to be air-conditioned.

[0095] The compressor 33, heat source-side heat exchanger 35, expansion valve 36, and load-side heat exchanger 38 are connected by refrigerant piping 39 to form a refrigerant circuit 40 through which the refrigerant circulates. The blower 37 has a first motor 2a connected to a first fan 4a, a second motor 2b connected to a second fan 4b, and a motor drive device 1 to which the first motor 2a and the second motor 2b are connected in parallel. The control device 41 is connected to each of the four-way valve 34, the compressor 33, the expansion valve 36, a temperature sensor (not shown), and a controller 5 (see FIG. 1) of the motor drive device 1 via signal lines (not shown).

[0096] The control device 41 is a control device that controls the air conditioner 30. The control device 41 controls the refrigeration cycle of the refrigerant circulating through the refrigerant circuit 40. Specifically, the control device 41 controls the operating frequency of the compressor 33, the opening of the expansion valve 36, and the speed command value ω* of the first motor 2a and the second motor 2b of the blower 37 so that the temperature of the air in the space to be air-conditioned becomes a predetermined set temperature. When the air conditioner 30 performs cooling operation, the heat source side heat exchanger 35 functions as a condenser, and the load side heat exchanger 38 functions as an evaporator. When the air conditioner 30 performs heating operation, the heat source side heat exchanger 35 functions as an evaporator, and the load side heat exchanger 38 functions as a condenser.

[0097] The first fan 4a and the second fan 4b are installed in parallel in the same air passage in the heat source unit 31. In this case, the loads acting on the first motor 2a and the second motor 2b are equalized, and the operation of these motors can be stabilized.

[0098] 13 shows a configuration in which the blower 37 is provided in the heat source side unit 31, but the blower 37 may be provided in the load side unit 32. In this case, the blower 37 supplies air from the space to be air-conditioned to the load side heat exchanger 38.

[0099] According to the fourth embodiment, the motor drive device 1 described in any one of the first to third embodiments is used for the blower 37, so that the first fan 4a and the second fan 4b can operate synchronously in a stable manner. For example, when the blower 37 supplies air to the heat source-side heat exchanger 35, an even volume of air is supplied to the entire heat source-side heat exchanger 35, and the heat exchange efficiency of the heat source-side heat exchanger 35 can be improved. [Explanation of symbols]

[0100] 1 motor drive device, 2a first motor, 2b second motor, 3a first current sensor, 3b second current sensor, 4a first fan, 4b second fan, 5, 5a, 5b controller, 6a first conductor, 6b second conductor, 7 signal line, 8 power converter, 9 AC power supply, 10 speed controller, 11 current controller, 12 inverse coordinate converter, 13 PWM signal generating means, 14a, 14b coordinate converter, 15a, 15b position speed estimator, 16, 16a, 16b compensation means, 21 to 26 subtractor, 30 air conditioning device, 31 heat source side unit, 32 load side unit, 33 compressor, 34 four-way valve, 35 heat source side heat exchanger, 36 expansion valve, 37 blower, 38 load side heat exchanger, 39 refrigerant piping, 40 Refrigerant circuit, 41 control device, 50 inverter circuit, 51d to 53d, 51u to 53u switching element, 54 rectifier circuit, 55 capacitor, 80 processing circuit, 91 processor, 92 memory, 93 bus.

Claims

1. A motor drive device that drives a first motor and a second motor, a first current sensor that detects a first current signal indicative of a current flowing through the first motor; a second current sensor that detects a second current signal indicative of a current flowing through the second motor; a power converter connected in parallel to the first motor and the second motor and supplying power to the first motor and the second motor; a controller that controls the power converter using a speed command value to control the frequencies of the first motor and the second motor; and The controller a coordinate converter that calculates a first q-axis current estimate that is an estimate of a torque current of the first motor using a first estimated phase that is an estimate of a phase of the first motor and the first current signal, and that calculates a second q-axis current estimate that is an estimate of a torque current of the second motor using a second estimated phase that is an estimate of a phase of the second motor and the second current signal; a compensation unit that compensates the first estimated phase based on an estimated current difference between the first q-axis current estimated value and the second q-axis current estimated value, thereby reducing a phase difference between the first motor and the second motor. Motor drive device.

2. The controller a speed controller that calculates a q-axis current command value for the first motor that reduces a difference between the speed command value input from an external device and an estimated speed that is an estimated value of the angular speed of the first motor; a current controller that calculates a q-axis voltage command value that reduces the difference between the q-axis current command value and the first q-axis current estimate value, and that calculates a d-axis voltage command value that reduces the difference between a d-axis current command value that is a command value of an excitation current of the first motor and a first d-axis current estimate value that is an estimate value of an excitation current of the first motor; a position and speed estimator that determines the estimated speed and the first estimated phase of the first motor using the d-axis voltage command value, the q-axis voltage command value, and the first d-axis current estimated value and the first q-axis current estimated value, and determines the second estimated phase using the d-axis voltage command value, the q-axis voltage command value, and a second d-axis current estimated value and a second q-axis current estimated value, which are estimates of excitation currents of the second motor; an inverse coordinate converter that converts the d-axis voltage command value and the q-axis voltage command value into three-phase voltages using the first estimated phase obtained by the position and speed estimator, The coordinate converter is determining the first d-axis current estimate using the first estimated phase and the first current signal, and determining the second d-axis current estimate using the second estimated phase and the second current signal; The compensation means delaying the first estimated phase when a value of a current difference between the motors, which is a value obtained by subtracting the first q-axis current estimated value from the second q-axis current estimated value, is positive, and advancing the first estimated phase when the value of the current difference between the motors is negative; The motor drive device according to claim 1 .

3. The controller a frequency of the first motor is controlled by position sensorless vector control, and a frequency of the second motor is compensated for and controlled by the compensation means; 3. The motor drive device according to claim 1 or 2.

4. the first motor and the second motor are permanent magnet synchronous motors; 3. The motor drive device according to claim 1 or 2.

5. a first motor coupled to a first fan; a second motor coupled to a second fan; a motor drive device according to claim 1 or 2 that drives the first motor and the second motor; A blower having

6. The first fan and the second fan are installed in parallel in the same air duct. The blower according to claim 5.

7. a refrigerant circuit in which a compressor, a heat source side heat exchanger, an expansion valve, and a load side heat exchanger are connected via refrigerant piping, and in which a refrigerant circulates; the blower according to claim 5, which supplies air to at least one of the heat source side heat exchanger and the load side heat exchanger; An air conditioning device having the above.

8. a first motor and a second motor connected in parallel, the motor drive device including a power converter that supplies power to the first motor and the second motor, a first current sensor that detects a first current signal that indicates a current flowing through the first motor, and a second current sensor that detects a second current signal that indicates a current flowing through the second motor, the motor drive method controlling the power converter using a speed command value and controlling frequencies of the first motor and the second motor, the method comprising: determining a first q-axis current estimate that is an estimate of a torque current of the first motor using a first estimated phase that is an estimate of a phase of the first motor and the first current signal; determining a second q-axis current estimate that is an estimate of a torque current of the second motor using a second estimated phase that is an estimate of a phase of the second motor and the second current signal; a step of reducing a phase difference between the first motor and the second motor by compensating the first estimated phase based on an estimated current difference between the first q-axis current estimated value and the second q-axis current estimated value; A motor driving method comprising:

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