阅读说明：本技术 马达驱动装置以及空调机 (Motor drive device and air conditioner ) 是由 清水裕一 畠山和德 于 2020-02-27 设计创作，主要内容包括：用1台逆变器(4)驱动马达(41、42)的马达驱动装置具备：失步控制部(30),该失步控制部(30)检测马达(41、42)中的至少1台马达的运行频率与逆变器输出频率不一致或至少1台马达的运行频率与另外1台马达的运行频率不一致的失步,在至少1台马达失步的情况下,切换逆变器(4)的通电状态而使马达(41、42)停止。(A motor drive device for driving motors (41, 42) by 1 inverter (4) is provided with: and a step-out control unit (30) that detects a step-out in which the operating frequency of at least 1 of the motors (41, 42) does not coincide with the inverter output frequency or the operating frequency of at least 1 of the motors does not coincide with the operating frequency of the other 1 of the motors, and switches the energization state of the inverter (4) to stop the motors (41, 42) when at least 1 of the motors is out of step.)

1. A motor driving device is provided with:

1 inverter for driving a plurality of motors; and

and a step-out control unit that detects step-out in which the operating frequency of at least 1 of the motors does not coincide with the inverter output frequency or the operating frequency of at least 1 of the motors does not coincide with the operating frequency of the other 1 of the motors, and switches the energization state of the inverter to stop the plurality of motors when at least 1 of the motors is step-out.

2. The motor drive apparatus according to claim 1,

the step-out control unit detects step-out of the motor based on a change in direction of a motor current flowing through each phase of the plurality of motors, a detected value of the motor current, or a speed estimated value of the plurality of motors.

3. The motor drive apparatus according to claim 1,

the step-out control unit detects step-out of the motor using at least two of a change in direction of a motor current flowing through each phase of the plurality of motors, a detected value of the motor current, and a speed estimation value of the plurality of motors.

4. The motor drive device according to any one of claims 1 to 3,

when at least 1 of the motors is out of step, first control is performed to apply a voltage for out-of-step control to the motors.

5. The motor drive apparatus according to claim 4,

in the first control, harmonic components are superimposed on motor currents flowing through respective phases of the motor.

6. The motor drive apparatus according to claim 4,

in the first control, the current command value used in the motor control is controlled to be zero.

7. The motor drive apparatus according to any one of claims 4 to 6,

when at least 1 of the motors is out of step, the first control is performed when the number of the out-of-step motors is different from the number of the motors already in operation.

8. The motor drive device according to any one of claims 1 to 3,

and performing a second control for bringing any one of 1 or more switching elements of an upper arm and 1 or more switching elements of a lower arm of the inverter into a conductive state when at least 1 motor is out of step.

9. The motor drive apparatus according to claim 8,

and when at least 1 motor is out of step, the second control is performed when the number of the out-of-step motors is the same as the number of the already-operating motors.

10. The motor drive apparatus according to claim 7,

and a third control unit configured to perform a third control of cutting off an output voltage from the inverter when a peak value of a current flowing through each phase of the motor after the first control is performed is smaller than a current threshold value in a case where at least 1 of the motors is out of step.

11. The motor drive apparatus according to claim 9,

and a third control unit configured to perform a third control of cutting off an output voltage from the inverter when a peak value of a current flowing through each phase of the motor after the second control is performed is smaller than a current threshold value in a case where at least 1 of the motors is out of step.

12. The motor drive apparatus according to claim 7,

and a third control unit configured to perform a third control of cutting off the output voltage from the inverter when the estimated speed value of the motor is smaller than a speed threshold value after the first control is performed when at least 1 of the motors is out of step.

13. The motor drive apparatus according to claim 9,

and a third control unit configured to perform a third control of cutting off the output voltage from the inverter when the estimated speed of the motor is smaller than a speed threshold value after the second control is performed when at least 1 of the motors is out of step.

14. The motor drive apparatus according to claim 7,

and a third control unit configured to, when at least 1 of the motors is out of step, perform a third control for cutting off the output voltage from the inverter when an elapsed time after the detection of the out-of-step after the first control is performed is longer than a time threshold.

15. The motor drive apparatus according to claim 9,

and a third control unit configured to perform a third control of cutting off the output voltage from the inverter when an elapsed time after the step-out detection is longer than a time threshold after the second control is performed in a case where at least 1 of the motors is out of step.

16. The motor drive device according to any one of claims 1 to 3,

when at least 1 of the motors is out of step, first control for applying a voltage for out-of-step control to the motors, second control for bringing any 1 or more of the switching elements of the upper arm or the switching elements of the lower arm of the inverter into a conductive state, and third control for cutting off the output voltage from the inverter are performed by switching in time series.

17. An air conditioner in which, in a state where,

a motor drive device according to any one of claims 1 to 16.

Technical Field

The present invention relates to a motor drive device for driving a plurality of motors by 1 inverter and an air conditioner provided with the motor drive device.

Background

In the case where the motor driven by the motor driving device is, for example, a permanent magnet synchronous motor, the driving of the permanent magnet synchronous motor requires positional information of the rotor. Therefore, in general, a position sensor for acquiring a rotor position is used for driving a permanent magnet synchronous motor. However, the use of the position sensor may cause problems such as an increase in size of the system, an increase in cost, and a decrease in environmental resistance. Therefore, driving of the permanent magnet synchronous motor requires application of sensorless control for driving the permanent magnet synchronous motor without using a position sensor. There are various types of sensorless control, and a method of using an induced voltage at the time of rotation generated by a magnetic flux of a permanent magnet embedded in a rotor of a motor is known.

In the sensorless control, an error between the estimated value of the position of the motor rotor and the actual rotor position may become large due to a factor such as an excessive load applied to the motor, and the motor may step out. When the motor is out of step, the motor needs to be restarted after being temporarily stopped. Therefore, the motor drive device is generally provided with a means for detecting whether or not the motor is out of step.

In addition, when a plurality of motors are driven by 1 inverter, it is necessary to detect step-out of each motor. Patent document 1 discloses the following technique: when a plurality of motors are driven by 1 inverter, step-out is detected based on the combined current of the motors, and if the motor is in a step-out state, the output voltage from the inverter is cut off and then the motor is restarted.

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. 2010-022184

Disclosure of Invention

Technical problem to be solved by the invention

When two motors are driven by 1 inverter, for example, the speed of the motor is reduced when 1 motor is out of step. When the speed of the motor decreases, the induced voltage of the motor also decreases. According to the method of patent document 1, when any motor is out of step, control is performed to cut off the output voltage from the inverter. However, even if the output voltage from the inverter is cut off, since the motors are electrically connected to each other, an excessive current may flow between the motors in response to the difference in the induced voltages of the motors.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a motor drive device including: in the configuration in which the plurality of motors are driven by 1 inverter, an excessive current that may flow between the plurality of motors in response to an induced voltage difference of each motor can be suppressed.

Means for solving the problems

In order to solve the above technical problem and achieve the object, a motor drive device according to the present invention includes 1 inverter for driving a plurality of motors. The motor drive device further includes a step-out control unit that detects a step-out in which the operating frequency of at least 1 motor does not coincide with the inverter output frequency or the operating frequency of at least 1 motor does not coincide with the operating frequency of the other 1 motor, and switches the energization state of the inverter to stop the plurality of motors when at least 1 motor is out of step.

Effects of the invention

According to the motor driving device of the present invention, the following effects are achieved: in the structure that 1 inverter drives a plurality of motors, the excessive current that may flow between the plurality of motors in response to the induced voltage difference of each motor can be suppressed.

Drawings

Fig. 1 is a diagram showing a configuration example of a motor drive device and its peripheral circuit according to embodiment 1.

Fig. 2 is a block diagram showing an example of a hardware configuration for realizing the functions of the control device of fig. 1.

Fig. 3 is a block diagram showing another example of a hardware configuration for realizing the functions of the control device of fig. 1.

Fig. 4 is a block diagram showing a configuration example of a control system built in the control device of fig. 1.

Fig. 5 is a diagram for explaining an operation of a Pulse Width Modulation (hereinafter, referred to as "PWM") signal generating section shown in fig. 4.

Fig. 6 is a diagram showing an example of the operation of each motor when the second motor is out of synchronization among the motors shown in fig. 1.

Fig. 7 is a flowchart for explaining the operation of the step-out detection unit according to embodiment 1.

Fig. 8 is a flowchart for explaining the operation of the second motor control unit according to embodiment 1.

Fig. 9 is a diagram showing an example of the operation of each motor when the step-out control of embodiment 1 is performed.

Fig. 10 is a block diagram showing a configuration example of a control system configured by the control device according to embodiment 2.

Fig. 11 is a flowchart for explaining the operation of the motor current determination unit according to embodiment 2.

Fig. 12 is a flowchart for explaining the operation of the motor speed determination unit according to embodiment 2.

Fig. 13 is a block diagram showing a first modification of the control system constructed in the control device according to embodiment 2.

Fig. 14 is a block diagram showing a second modification of the control system constructed in the control device according to embodiment 2.

Fig. 15 is a block diagram showing a configuration example of a control system constructed in the control device of embodiment 3.

Fig. 16 is a block diagram showing a configuration example of a control system configured by the control device according to embodiment 4.

Fig. 17 is a flowchart for explaining operations of the step-out detection unit and the second motor control unit according to embodiment 4.

Fig. 18 is a diagram showing an example in which the motor drive device of embodiment 5 is applied to an air conditioner.

Reference numerals

1: an alternating current power supply; 2: a rectifier; 3: a smoothing section; 4: an inverter; 4 a: a switching element; 6: an input voltage detection unit; 7: a power line; 8: a branch point; 10: a control device; 11. 12, 19: a coordinate transformation unit; 13: a first motor speed estimating section; 14: a second motor speed estimating section; 15. 16: an integrator; 17: a first motor control unit; 17 a: a current command value calculation unit; 18: a pulsation compensation control unit; 20: a PWM signal generation unit; 22. 22A, 22B, 22C, 22D: an out-of-step detection unit; 24. 24A, 24B: a second motor control unit; 30. 30A, 30B, 30C, 30D, 30E: an out-of-step control section; 41. 42: a motor; 41a, 42 a: a fan; 51. 52: a current detection unit; 70: an outdoor unit; 100: an air conditioner; 221: a current direction determination unit; 222: a motor current determination unit; 223: a motor speed determination unit; 224. 225: a logic OR circuit; 241: a current controller; 300: a processor; 302: a memory; 304: an interface; 305: a processing circuit.

Detailed Description

A motor drive device and an air conditioner according to an embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below. Hereinafter, the electrical connection and the mechanical connection are simply referred to as "connection" without distinction.

Embodiment 1.

Fig. 1 is a diagram showing a configuration example of a motor drive device and its peripheral circuit according to embodiment 1. The motor drive device of embodiment 1 is a motor drive device that drives a plurality of motors by 1 inverter. The two motors 41, 42 in fig. 1 are examples of a plurality of motors.

As shown in fig. 1, the motor drive device according to embodiment 1 includes an inverter 4 including 6 switching elements 4a, and a smoothing unit 3 operating as a dc power supply for supplying a dc voltage to the inverter 4. An example of the smoothing section 3 is a capacitor. The inverter 4 is connected in parallel to the output side of the smoothing section 3. In the inverter 4, 6 switching elements 4a are bridged, and constitute a main circuit of the inverter 4.

An example of the switching element 4a is an Insulated Gate Bipolar Transistor (IGBT) shown in the figure, but other switching elements may be used. Other examples of the switching element 4a are Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). A rectifier 2 is connected in parallel to an input side of the smoothing section 3. The rectifier 2 has 4 diodes bridged. The rectifier 2 is supplied with ac power from the ac power supply 1. Ac power from the ac power supply 1 is rectified by the rectifier 2 and smoothed by the smoothing unit 3, and the smoothed dc power is supplied to the inverter 4.

In fig. 1, the ac power supply 1 and the rectifier 2 are described as a single phase, but may be three phases. As the capacitor of the smoothing section 3, an aluminum electrolytic capacitor having a large capacitance is generally used, but a thin film capacitor having a long service life may be used. In addition, a capacitor having a small capacitance may be used. If a capacitor having a small capacitance is used, harmonic current of current flowing through the ac power supply 1 can be suppressed. Further, in order to suppress harmonic current or improve power factor, a reactor may be inserted in the electric wiring between the ac power supply 1 and the smoothing unit 3.

The inverter 4 includes 3 phases, that is, 3 branches (leg) in which the switching element of the upper arm (arm) and the switching element of the lower arm are connected in series in this order. The 3 branches constitute a U-phase branch, a V-phase branch and a W-phase branch. The U-phase branch, the V-phase branch, and the W-phase branch are connected in parallel between a P line and an N line, which are dc buses to which dc power is supplied.

A power line 7 is drawn from a connection end of the switching element of the upper branch and the switching element of the lower branch. The power line 7 is branched into two by a branch point 8, and connected to a motor 41 as a first motor and a motor 42 as a second motor, respectively. An example of the motors 41, 42 is a three-phase permanent magnet synchronous motor.

The dc power smoothed by the smoothing unit 3 is supplied to the inverter 4, and then converted into arbitrary three-phase ac power by the inverter 4. The converted three-phase alternating-current power is supplied to the motor 41 and the motor 42.

Fig. 1 shows a configuration in which each branch of the inverter 4 has only a switching element, but the configuration is not limited to this configuration. In order to suppress a surge voltage generated by the switching operation of the switching element, a free wheeling diode may be connected in anti-parallel to both ends of the switching element. In addition, when the switching element is a MOSFET, a parasitic diode of the MOSFET may be used as the free wheeling diode. Further, when the switching element is a MOSFET, the MOSFET is turned on at the timing of the backflow, and thus the function of the backflow can be realized only by the switching element. In addition, as a material constituting the switching element, not only silicon (Si) but also silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga) which are wide band gap semiconductors may be used₂O₃) Diamond, etc. If a switching element is formed using a wide band gap semiconductor-based material, low loss and high speed switching can be achieved.

Next, the sensors necessary for controlling the inverter 4 will be described. In fig. 1, the current detection unit 51 is a current sensor that detects motor currents of three phases flowing through the motor 41, and the current detection unit 52 is a current sensor that detects motor currents of three phases flowing through the motor 42. The input voltage detector 6 detects a dc bus voltage V, which is a voltage between the P line and the N line of the dc bus_dcThe bus voltage sensor of (1).

The control device 10 detects the motor current i based on the current detection unit 51_{u_m}、i_{v_m}、i_{w_m}And a motor current i detected by the current detection unit 52_{u_sl}、i_{v_sl}、i_{w_sl}And the DC bus voltage V detected by the input voltage detecting part 6_dcMotor control calculation is performed to generate drive signals for the respective switching elements of the inverter 4.

The current detectors 51 and 52 are exemplified by current transformers, but are not limited thereto. A method of detecting the motor current from the both-end voltage of the resistance without using a current transformer may be employed. As either one of the current detection units 51 and 52, a resistor for current detection may be provided between the connection point of the switching element of the lower arm of the inverter 4 and the connection point of the switching elements of the 3 lower arms, or a resistor for current detection may be provided between the connection point of the switching elements of the 3 lower arms and the connection point of the capacitor connected to the negative-side dc bus, that is, the N-line.

Although fig. 1 shows a configuration having two motors, 3 or more motors may be provided. It goes without saying that current sensors for detecting motor currents are provided for 3 or more motors, respectively.

Although the number of inverters is 1 in fig. 1, a plurality of inverters may be provided. The plurality of inverters each have a structure in which a P line and an N line, which are direct current buses, are connected to a common bus between the P line and the N line.

Fig. 2 is a block diagram showing an example of a hardware configuration for realizing the functions of the control device 10 in fig. 1. Fig. 3 is a block diagram showing another example of a hardware configuration for realizing the functions of the control device 10 in fig. 1.

In order to realize the motor control function by the control device 10 described below, as shown in fig. 2, the motor control device may include a processor 300 for performing calculation, a memory 302 for storing a program read by the processor 300, and an interface 304 for inputting and outputting signals.

The Processor 300 may be an arithmetic Unit such as an arithmetic Unit, a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). As the Memory 302, a nonvolatile or volatile semiconductor Memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash Memory, an EPROM (Erasable Programmable ROM), and an EEPROM (registered trademark) (Electrically Erasable Programmable EPROM) can be exemplified.

Specifically, a program for executing the motor control function of the control device 10 is stored in the memory 302. The processor 300 transmits and receives necessary information via the interface 304, the processor 300 executes a program stored in the memory 302, and the processor 300 refers to a table stored in the memory 302 to be able to execute motor control described below. The operation results obtained by the processor 300 can be stored in the memory 302.

In addition, the processor 300 and the memory 302 shown in fig. 2 may be replaced with a processing circuit 305 as shown in fig. 3. The processing Circuit 305 corresponds to a single Circuit, a composite Circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a structure in which these are combined. Inputting information to the processing circuit 305 and outputting information from the processing circuit 305 can be performed via the interface 304.

Next, motor control performed by the control device 10, which is one of the points of the present invention, will be described with reference to fig. 1, 4, and 5. Fig. 4 is a block diagram showing a configuration example of a control system built in the control device 10 of fig. 1. Fig. 5 is a diagram for explaining the operation of the PWM signal generation unit 20 shown in fig. 4.

The control device 10 includes coordinate conversion units (shown as "uvw/dq" in fig. 4) 11 and 12, a first motor speed estimation unit 13, a second motor speed estimation unit 14, integrators 15 and 16, a first motor control unit 17, a ripple compensation control unit 18, a coordinate conversion unit (shown as "dq/uvw" in fig. 4) 19, a PWM signal generation unit 20, and a step-out control unit 30. The step-out control unit 30 includes a step-out detection unit 22 and a second motor control unit 24. The first motor control unit 17 includes a current command value calculation unit 17a, the step-out detection unit 22 includes a current direction determination unit 221, and the second motor control unit 24 includes a current controller 241.

The step-out detecting unit 22 detects whether at least 1 of the motors 41 and 42, which are examples of the plurality of motors, is out of step. Here, "at least 1 out-of-step" means a case where at least one of the following phenomena (1) to (3) is assumed to occur.

(1) The inverter output frequency does not coincide with the operating frequency of the motor 41

(2) The inverter output frequency is not coincident with the operating frequency of the motor 42

(3) The operating frequency of the motor 41 does not coincide with the operating frequency of the motor 42

In the case where the number of motors is 3 or more, when the operating frequency of at least 1 motor does not coincide with the inverter output frequency or the operating frequency of at least 1 motor does not coincide with the operating frequency of the other 1 motor, it corresponds to the above-mentioned "at least 1 out of step".

The "inverter output frequency" mentioned above is a frequency of a voltage applied to the motors 41 and 42 by the inverter 4. The inverter output frequency corresponds to a motor speed command value ω to be described later_m ^*. The motor speed command value may be referred to as a "rotational speed command value" or a "rotational speed command" instead. The "operating frequency" described above corresponds to the motor rotation frequency. Further, the detection of whether the comparison object is inconsistent can be based on the comparisonThe difference information of the frequencies of the objects or the information of the ratio of the objects to each other is compared, but a method different from these is used in the present embodiment. Details will be described later.

When at least 1 motor is out of step, the second motor control unit 24 performs control for switching the energization state of the inverter 4 to stop the motor. The switching of the energization state is described as an example of a method of controlling the switching of the voltage command value input to the PWM signal generation unit 20 in embodiment 1.

Next, the operation of each part constituting the control device 10 will be described. First, the coordinate conversion unit 11 receives the motor current i, which is a current value in the stationary three-phase coordinate system detected by the current detection unit 51_{u_m}、i_{v_m}、i_{w_m}. The coordinate conversion unit 11 uses a motor phase estimation value θ to be described later_{m_e}Applying the motor current i_{u_m}、i_{v_m}、i_{w_m}Converted into motor dq axis current i_{d_m}、i_{q_m}. Here, the motor dq axis current i_{d_m}、i_{q_m}The current value of the rotating two-phase coordinate system in the motor 41. Motor dq axis current i converted by coordinate conversion unit 11_{d_m}、i_{q_m}The input is to the first motor speed estimating unit 13 and the first motor control unit 17.

The coordinate conversion unit 12 receives the motor current i, which is a current value in the stationary three-phase coordinate system detected by the current detection unit 52_{u_sl}、i_{v_sl}、i_{w_sl}. The coordinate transformation unit 12 transforms the motor current i_{u_sl}、i_{v_sl}、i_{w_sl}Converted into motor dq axis current i_{d_sl}、i_{q_sl}. Here, the motor dq axis current i_{d_sl}、i_{q_sl}The current value is the rotating two-phase coordinate system in the motor 42. Motor dq axis current i converted by coordinate conversion unit 12_{d_sl}、i_{q_sl}The input is to the second motor speed estimating unit 14 and the pulsation compensation control unit 18.

First motor speed estimating unit 13 estimates motor dq-axis current i_{d_m}、i_{q_m}Estimating motor speed estimation value ω_{m_e}. The integrator 15 estimates the value ω by estimating the motor speed_{m_e}Integrating to calculate motor phase estimation value theta_{m_e}. Motor phase estimation value θ calculated for coordinate conversion of current value, coordinate conversion of voltage command value, and ripple compensation control to be described later_{m_e}The input is input to the coordinate conversion unit 11, the ripple compensation control unit 18, and the coordinate conversion unit 19.

In addition, the second motor speed estimating unit 14 estimates the motor dq-axis current i based on the motor dq-axis current i_{d_sl}、i_{q_sl}Estimating motor speed estimation value ω_{sl_e}. The integrator 16 estimates the value ω by estimating the motor speed_{sl_e}Integrating to calculate motor phase estimation value theta_{sl_e}. Motor phase estimation value θ calculated for coordinate conversion of current value and ripple compensation control to be described later_{sl_e}The input is to the coordinate conversion unit 12 and the ripple compensation control unit 18.

Note that methods of calculating the motor speed estimation value and the motor phase estimation value are well known, and a detailed description thereof will be omitted. Details of a method of calculating each estimated value are described in, for example, japanese patent No. 4672236, and refer to the description. This description is incorporated in and constitutes a part of this specification. The method of calculating each estimated value is not limited to the contents described in the above publication, and any method may be used as long as the estimated values of the motor speed and the motor phase can be obtained. The information used for the calculation may be any information as long as it is information that can obtain the estimated values of the motor speed and the motor phase, and the information described here may be omitted or information other than the information may be used.

In the absence of the ripple compensation control unit 18, the first motor control unit 17 bases on the motor dq-axis current i_{d_m}、i_{q_m}And motor speed estimated value ω_{m_e}Calculating a dq-axis voltage command value v_d ^*、v_q ^*. Then, the coordinate conversion unit 19 estimates the value θ based on the motor phase_{m_e}And dq axis voltage command value v_d ^*、v_q ^*The obtained voltage phase theta_vWill beDq-axis voltage command value v in rotating two-phase coordinate system in motor 41_d ^*、v_q ^*Voltage command value v converted to static three-phase coordinate system_u ^*、v_v ^*、v_w ^*. Voltage phase theta_vThe phase angle of the voltage command value in the rotating two-phase coordinate system is shown. The motor phase estimation value θ is shown in the upper part of fig. 5_{m_e}Phase difference theta based on phase control_fAnd voltage phase theta_vThe relationship (2) of (c). As shown in the upper part of fig. 5, at the voltage phase θ_vMotor phase estimation value theta_{m_e}Phase difference theta from_fHas a theta between_v＝θ_{m_e}－θ_fThe relationship (2) of (c).

PWM signal generation unit 20 generates a voltage command value v based on the voltage command value v_u ^*、v_v ^*、v_w ^*And a DC bus voltage V_dcA PWM signal for PWM-controlling the switching elements of the inverter 4 is generated. An example of a PWM signal is shown in the lower part of fig. 5. UP is a PWM signal for controlling the switching elements of the upper arm of the U-phase of the inverter 4, and UN is a PWM signal for controlling the switching elements of the lower arm of the U-phase of the inverter 4. Hereinafter, similarly, VP and VN are PWM signals for controlling the switching elements of the V-phase upper arm and the switching elements of the V-phase lower arm, respectively, and WP and WN are PWM signals for controlling the switching elements of the W-phase upper arm and the switching elements of the W-phase lower arm, respectively. As shown in the middle of fig. 5, these PWM signals can be based on the voltage command values v of the three phases_u ^*、v_v ^*、v_w ^*A size relationship with the carrier.

Here, the motor 42 is driven only in accordance with the voltage command value calculated with reference to the motor 41, based on the control content described above, that is, the control content when the ripple compensation control unit 18 is not present. Thus, the motor 41 operates as a master motor, and the motor 42 operates as a slave motor. At this time, the motor dq axis current i of the motor 41_{d_m}、i_{q_m}Motor dq axis current i with motor 42_{d_sl}、i_{q_sl}Depending on the control state of the inverter 4, the control state may be changedA phase difference called an axis error is generated. By knowing the axis error, the motor phase estimate θ can be learned_{m_e}Estimated value of phase with motor_{sl_e}Delay or advance of the phase therebetween.

Here, the motor dq axis current i of the motor 41_{d_m}、i_{q_m}Motor dq axis current i with motor 42_{d_sl}、i_{q_sl}In a control state in which an axis error occurs, particularly in a low speed region of the motor speed, a motor current from the motor 42 of the motor may pulsate. When the current pulsation occurs, the motor 42 may step out, the loss in the motor 42 may increase due to heat generation caused by an excessive current, or the motor 41 may not be stopped due to a circuit interruption caused by an excessive current. In order to eliminate or suppress the current ripple, a ripple compensation control unit 18 is provided.

The pulsation compensation control unit 18 estimates the value θ based on the motor phase in the motor 41_{m_e}Motor phase estimation value θ of motor 42_{sl_e}And motor q-axis current i of motor 42_{q_sl}Generating a ripple compensation current command value i_sl ^*. Estimating the value theta by using the motor phase of the motor 41_{m_e}And a motor phase estimation value theta of the motor 42_{sl_e}The above-described axis error can be known. Then, based on the information of the axis error, a motor q-axis current i is generated to suppress the torque current of the motor 42_{q_sl}Ripple of the current command value i_sl ^*。

Ripple compensation current command value i generated by ripple compensation control unit 18_sl ^*Is supplied to the first motor control section 17. In the first motor control unit 17, the current command value calculation unit 17a controls the motor speed command value ω of the motor 41 by proportional-integral control or the like_m ^*Estimated motor speed ω of motor 41_{m_e}To calculate a q-axis current command value i to the motor 41_{q_m} ^*. The current command value calculation unit 17a also compensates the current command value i based on the ripple_sl ^*To calculate d-axis current command value i_{d_m} ^*. D-axis current command value i as an exciting current component for motor 41_{d_m} ^*The current phase can be controlled by changing the value. Therefore, the d-axis current command value i is used_{d_m} ^*Variably generated voltage command value v_u ^*、v_v ^*、v_w ^*The motor 41 can be driven by the strong magnetic flux or the weak magnetic flux. By utilizing this characteristic, the ripple compensation current command value i is set_sl ^*Reflected on the d-axis current command value i_{d_m} ^*The current ripple can be suppressed.

The first motor control unit 17 can control the motor dq-axis current i_{d_m}、i_{q_m}And dq axis current command value i_{d_m} ^*、i_{q_m} ^*The deviation of the voltage is subjected to proportional-integral control to calculate a dq-axis voltage command value v_d ^*、v_q ^*. In addition, any method may be used as long as the same function can be achieved. According to the above operation, the motor 41 and the motor 42 can be driven by 1 inverter 4 while suppressing current pulsation that may occur in the motor 42 as a slave motor.

Next, the operation of the main part of the motor drive device of embodiment 1 will be explained. First, the operation of the motor when the motor is out of step will be described. Fig. 6 is a diagram showing an operation example of each motor when the motor 42 as the second motor is out of step among the motors shown in fig. 1. In fig. 6, the horizontal axis represents time, the vertical axis of the upper waveform represents the motor speed, and the vertical axis of the lower waveform represents the current. In each waveform on the upper part, a thick solid line shows the speed of the motor 41, and a thick broken line shows the speed of the motor 42. In the lower waveforms, the thick solid line shows the U-phase current of the motor 41, the thick broken line shows the U-phase current of the motor 42, and the alternate long and short dash line shows the U-phase current output from the inverter 4.

In fig. 6, the motors 41 and 42 are appropriately controlled between time t0 and time t 1. Therefore, the motor speeds, the amplitudes of the motor currents, and the frequencies of the motor currents in the motors 41 and 42 are stable. On the other hand, in fig. 6, the motor 42 is out of step at time t1, and the motor speed decreases. Here, when the motor speed of the motor 42 decreases, the induced voltage of the motor 42 decreases. Since the motor current is proportional to the difference between the output voltage of the inverter 4 and the motor induced voltage, the current amplitude of the motor 42 that is out of step becomes large. In the motor 42 that is out of step, the direction of the motor current in the motor 42 changes because the motor speed and the phase of the motor induced voltage change. Therefore, if a change in the direction of the motor current in the motor 42 that is out of step is detected, the out of step of the motor 42 can be detected. The current direction determining unit 221 of the step-out detecting unit 22 performs this function.

Next, the operation of the step-out detection unit 22 according to embodiment 1 will be described. Fig. 7 is a flowchart for explaining the operation of the step-out detection unit 22 according to embodiment 1. The processing of each step in fig. 7 is performed by the current direction determination unit 221. In fig. 7, the motor current is determined for each motor for each phase current of three phases. To perform the processing of the flowchart of fig. 7, the motor current i detected by the current detection unit 51 is input to the step-out detection unit 22_{u_m}、i_{v_m}、i_{w_m}And the motor current i detected by the current detection unit 52_{u_sl}、i_{v_sl}、i_{w_sl}The respective motor currents. In the determination, if it is determined that the motor current of at least one phase is "yes", the process proceeds to the "yes" side. When the motor current of all the phases of all the motors is determined as "no", the process proceeds to the process on the "no" side. In the following, the motor current of one phase will be described for simplicity.

In step S101, the last value of the motor current is compared with the last value, and if the last value is smaller than the last value (yes in step S101), the process proceeds to step S102. In step S102, the previous value and the present value of the motor current are compared, and if the previous value is equal to or less than the present value (no in step S102), the process proceeds to step S103. In step S103, it is determined that the current direction has not changed, the elapsed time is counted up, and the process returns to step S101.

In step S101, if the previous value of the motor current is equal to or greater than the previous value (no in step S101), the process proceeds to step S104. In step S104, the previous value and the present value of the motor current are compared, and if the previous value is equal to or greater than the present value (no in step S104), the process proceeds to step S105. In step S105, it is determined that the current direction has not changed, the elapsed time is counted up, and the process returns to step S101.

Next, in step S102, if the previous value of the motor current is larger than the present value (yes in step S102), the process proceeds to step S106. In step S104, if the last value of the motor current is smaller than the present value (yes in step S104), the process proceeds to step S106.

The above-described processing in steps S101, S102, and S104 is processing for determining whether or not there is a change in the 1 motor current from the decreasing direction to the increasing direction and a change from the increasing direction to the decreasing direction. Then, when there is a change in both directions, it is determined that the current direction has changed.

In step S106, it is determined that the current direction has changed. In step S106, the frequency f _ dir of the motor current determined to have a change in the current direction is calculated based on the elapsed time. Further, in step S106, the count of the elapsed time is cleared.

In step S107, the frequency f _ dir of the motor current is compared with a predetermined threshold value f _ i. In determining the magnitude relationship with the threshold value f _ i, it is preferable to provide the threshold value f _ i with a margin in order to prevent erroneous determination or to prevent fluctuation in determination. In order to suppress erroneous determination due to noise or the like, filtering processing may be performed on the detection values of the current detection units 51 and 52 using a low-pass filter or the like.

In step S107, if the frequency f _ dir of the motor current is greater than the threshold value (f _ i + margin) (yes in step S107), the process proceeds to step S108.

In step S107, if the frequency f _ dir of the motor current is equal to or less than the threshold value (f _ i + remaining amount) (no in step S107), the process proceeds to step S109. Then, in step S109, if the frequency f _ dir of the motor current is smaller than the threshold value (f _ i — margin) (yes in step S109), the process proceeds to step S108, and if the frequency f _ dir of the motor current is equal to or greater than the threshold value (f _ i — margin) (no in step S109), the process proceeds to step S110.

In step S108, a process of step out, which will be described later, is performed, and the process of the flowchart of fig. 7 is ended. As shown in fig. 4, the determination result Sout1 of whether there is step-out is input to the PWM signal generation unit 20. In step S110, it is determined that there is no step-out, and the process of the flowchart in fig. 7 is ended.

The processing of step S106 described above is supplemented. In the case where the motor normally operates, since the motor current is a sine wave, the change in the direction of the current occurs at the peaks and valleys of the sine wave. Therefore, when the motor is normally operated, the frequency of the change in the direction of the current changes at 2 times the frequency of the motor current. As shown in the lower waveform of fig. 6, the period of the change in the direction of the current in the normal operation is generally longer than the period of the change in the direction of the current in the step-out operation. Therefore, the frequency 2 times the motor current frequency is set as the threshold f _ i, and the calculated motor current frequency f _ dir is compared with the threshold f _ i, whereby the presence or absence of step-out can be determined.

It is assumed that the frequency of the change in the direction of the current is sometimes lower than 2 times the frequency of the motor current depending on the operation of the motor that is out of step. Therefore, the process of step S109 is added to the flowchart of fig. 7.

In the determination process of step S101, the previous value of the motor current is equal to the previous value, but it may be determined as "yes". That is, the last value of the motor current may be equal to the last value, and the determination may be made as either yes or no.

In the determination process of step S102, the previous value of the motor current is equal to the present value, and it is determined as no, but it may be determined as yes. That is, the previous value and the present value of the motor current may be equal to each other, and the current value may be determined as either yes or no.

In the determination process of step S104, the previous value of the motor current is equal to the present value, and it is determined as no, but it may be determined as yes. That is, the previous value and the present value of the motor current may be equal to each other, and the current value may be determined as either yes or no.

In the determination process of step S107, it is determined as no if the frequency f _ dir of the motor current is equal to the threshold (f _ i + remaining amount), but it may be determined as yes. That is, the frequency f _ dir of the motor current may be equal to the threshold (f _ i + remaining amount) and determined as either yes or no.

In the determination process of step S109, it is determined as no if the frequency f _ dir of the motor current is equal to the threshold (f _ i — margin), but it may be determined as yes. That is, the frequency f _ dir of the motor current may be equal to the threshold (f _ i + remaining amount) and determined as either yes or no.

Next, the operation of the second motor control unit 24 according to embodiment 1 will be described with reference to fig. 8 and 9. Fig. 8 is a flowchart for explaining the operation of the second motor control unit 24 according to embodiment 1. The processing of the flowchart shown in fig. 8 shows details of the processing of step S108 of fig. 7. Fig. 9 is a diagram showing an example of the operation of each motor when the step-out control of embodiment 1 is performed. Fig. 8 shows current control for the U-phase current, and the V-phase current and the W-phase current are similarly performed.

In order to perform the processing of the flowchart of fig. 8, the motor current i detected by the current detection unit 51 is input to the second motor control unit 24_{u_m}、i_{v_m}、i_{w_m}And the motor current i detected by the current detection unit 52_{u_sl}、i_{v_sl}、i_{w_sl}The respective motor currents.

In fig. 8, in step S201, the absolute value of the phase current of each U phase of the motors 41 and 42 is calculated. In step S202, the absolute value of the U-phase current of the motor 41 and the absolute value of the U-phase current of the motor 42 are compared. If the absolute value of the U-phase current of the motor 41 is larger than the absolute value of the U-phase current of the motor 42 (yes in step S202), the process proceeds to step S203. On the other hand, if the absolute value of the U-phase current of the motor 41 is equal to or less than the absolute value of the U-phase current of the motor 42 (no in step S202), the process proceeds to step S204.

In step S203, current control is performed on the U-phase current of the motor 41 having a large absolute value of current. In step S204, current control is performed on the U-phase current of the motor 42 having a large absolute value of current. The current control here can be implemented by a normal PI control.

When step-out occurs, the peak value of the motor current increases in the step-out motor. When the motor is, for example, a permanent magnet synchronous motor, if a motor current having a large peak value flows, the permanent magnet of the motor may be demagnetized. Therefore, when step-out occurs, it is preferable to control the motor to be stopped while suppressing the peak value of the motor current.

In the flowchart of fig. 8, the case where there are two motors is described, but when the number of motors is 3 or more, the current control may be performed for the motor having the largest absolute value of the current among the motors. Accordingly, the current control can be performed preferentially for the motor in a state where the current is large among the plurality of motors, and the peak value of the motor current can be suppressed by a simple process.

In the determination processing of step S202, it is determined that the absolute value of the U-phase current of the motor 41 is equal to the absolute value of the U-phase current of the motor 42, but it may be determined as yes. That is, the case where the absolute value of the U-phase current of the motor 41 is equal to the absolute value of the U-phase current of the motor 42 may be determined as either "yes" or "no".

An example of the current control at the time of step-out is to superimpose a harmonic component on the motor current.

In step S203 of fig. 8, the current controller 241 generates the U-phase voltage command value v so as to add a harmonic component to the U-phase current of the motor 41_u ^*. At this time, in fig. 4, when determination result Sout1 output from step-out detection unit 22 is a signal indicating that there is step-out, PWM signal generation unit 20 bases on U-phase voltage command value v output from second motor control unit 24_u ^*A PWM signal is generated. That is, when the determination result Sout1 indicates that there is step-out, the voltage command value v output from the second motor control unit 24 is used_u ^*、v_v ^*、v_w ^*Instead of the voltage command value v output from the coordinate conversion unit 19_u ^*、v_v ^*、v_w ^*A PWM signal is generated.

In the flowchart of fig. 8, even when the result of determination in step S202 differs between the phases of UVW, the processing in step S202 and the processing in step S203 are performed independently. For example, when the U-phase current of the motor 41 is large and the V-phase current and the W-phase current of the motor 42 are large, the harmonic component superimposition control described here is performed for each of the large currents.

Note that, regarding the superimposition of the harmonic component on the motor current, other methods may be used as long as the harmonic component is superimposed on the current command value supplied to the current controller 241.

Fig. 9 shows an operation in which a harmonic component is superimposed on the U-phase current of the motor 41 having a large absolute value of current when the speed of the motor 42 is reduced by simulating step-out. In fig. 9, the horizontal axis represents time, the vertical axis of the upper waveform represents the motor speed, and the vertical axis of the lower waveform represents the current. In each waveform on the upper part, a thick solid line shows the speed of the motor 41, and a thick broken line shows the speed of the motor 42. In the lower waveforms, the thick solid line shows the U-phase current of the motor 41, the thick broken line shows the U-phase current of the motor 42, and the alternate long and short dash line shows the U-phase current output from the inverter 4.

By adding a harmonic component to the U-phase current of the motor 41, the peak value of each U-phase current of the motors 41, 42 is reduced to about 1/2 as shown in fig. 9. After the peak value of the current is reduced to a level at which demagnetization of the permanent magnet of the motor can be prevented, the motors 41 and 42 may be gradually decelerated by the inertia moment, and finally the motors 41 and 42 may be stopped.

In the above, the case where the harmonic component is superimposed on the motor current has been described as an example of the current control at the time of step-out, but the method is not limited to this. For example, the control may be performed such that the current command value supplied to the current controller 241 is 0[ a ], that is, the current command value used for motor control is controlled to zero. This control also suppresses the peak value of the motor current. In addition, when the control of superimposing the harmonic component and the control of setting the current command value to zero are performed, the output voltage of the inverter 4 is changed. Therefore, the first control can be also referred to as control in which a voltage for step-out control is applied to each motor.

In addition, fig. 4 shows that the second motor control unit 24 generates the voltage command value v in the stationary three-phase coordinate system_u ^*、v_v ^*、v_w ^*And supplied to the controller of the PWM signal generation section 20, but is not limited to this configuration. Instead of the structure of fig. 4, the generation of the dq-axis voltage command value v in the rotating two-phase coordinate system may be constructed_d ^*、v_q ^*And supplied to the controller of the coordinate transformation unit 19. In this case, a current value of dq axis in a rotating two-phase coordinate system may be used, or a current value of α β axis in a two-phase fixed coordinate system obtained by coordinate conversion to dq axis may be used.

As described above, the motor drive device according to embodiment 1 detects step-out in which the operating frequency of at least 1 motor does not coincide with the inverter output frequency or the operating frequency of at least 1 motor does not coincide with the operating frequency of the other 1 motor, and switches the energization state of the inverter to stop the plurality of motors when at least 1 motor is step-out. Accordingly, in the configuration in which the plurality of motors are driven by 1 inverter, it is possible to suppress an excessive current that may flow between the plurality of motors in response to the induced voltage difference of each motor.

Further, according to the motor drive device of embodiment 1, since an excessive current, that is, an excessive circulating current, which may flow between the motors can be suppressed, it is possible to suppress the risk of demagnetizing the permanent magnets of the motors when the motors are out of step.

Further, according to the motor drive device of embodiment 1, when applied to, for example, a fan motor of an air conditioner to be described later, the fan motor having a large moment of inertia can be stopped quickly. Accordingly, the time until the restart can be shortened, and the performance of the air conditioner can be improved.

Embodiment 2.

Fig. 10 is a block diagram showing a configuration example of a control system configured by the control device according to embodiment 2. In fig. 10, in the control system according to embodiment 2, out-of-step control unit 30 is replaced with out-of-step control unit 30A in the configuration of the control system according to embodiment 1 shown in fig. 4. In the step-out control unit 30A, the step-out detection unit 22 is replaced with a step-out detection unit 22A, and the second motor control unit 24 is replaced with a second motor control unit 24A. The step-out detection unit 22A includes a motor current determination unit 222 and a motor speed determination unit 223. The other structures are the same as or equivalent to those of embodiment 1, and the same reference numerals are assigned to the same or equivalent structural parts, and redundant description thereof is omitted.

The function of the second motor control section 24A is different from that of the second motor control section 24. Details regarding the function of the second motor control portion 24A will be described later. In order to distinguish between the control performed by the second motor control unit 24 and the control performed by the second motor control unit 24A, the former is sometimes referred to as "first control", and the latter is sometimes referred to as "second control".

Next, the operation of the main part of embodiment 2 will be explained. First, fig. 11 is a flowchart for explaining the operation of the motor current determination unit 222 according to embodiment 2. In fig. 11, the motor current determination unit 222 performs the processing of steps S301 and S302, and the PWM signal generation unit 20 and the second motor control unit 24A perform the processing of step S303.

In fig. 11, in step S301, the absolute values of the respective phase currents of the motors 41 and 42 are calculated. In step S302, the absolute value of each phase current is compared with a determination threshold value for step-out determination. If the absolute value of at least one phase current is greater than the determination threshold (YES at step S302), it is determined that there is step-out (step S303). When it is determined that step-out is present, a determination result Sout2 indicating that step-out is present is input to the PWM signal generation unit 20. In step S303, control is performed when there is step loss.

Specifically, in embodiment 2, a PWM signal is generated such that at least 1 of the switching elements of the upper arm and the switching elements of the lower arm of the inverter 4 are turned on. The control is based on the voltage command value v generated by the second motor control unit 24A_u ^*、v_v ^*、v_w ^*To be implemented. When 1 or more of the switching elements of the upper arm and the switching elements of the lower arm of the inverter 4 are brought into a conductive state, the windings of the motors, not shown, are short-circuited via the switching elements brought into the conductive state. Accordingly, a current proportional to the induced voltage of each motor flows to the inverter 4, and the regenerative energy of each motor is consumed. Accordingly, the motor can be stopped in a shorter time than when each motor is decelerated by the inertia moment.

When the process of step S303 is completed, the process of the flowchart of fig. 11 is ended. In step S302, if the absolute values of all the phase currents are equal to or less than the determination threshold (no in step S302), it is determined that there is no step-out (step S304), and the determination result Sout2 indicating that there is no step-out is input to the PWM signal generating unit 20. In this case, the control executed by the second motor control unit 24A is not executed, and the processing of the flowchart in fig. 11 is ended.

In the determination process of step S302, it is determined as no if the absolute value of the phase current is equal to the determination threshold, but it may be determined as yes. That is, the absolute value of the phase current may be equal to the determination threshold, and the determination may be made as either yes or no.

Fig. 12 is a flowchart for explaining the operation of the motor speed determination unit 223 of embodiment 2. In fig. 12, the motor speed determination unit 223 performs the processing of steps S401 and S403, and the PWM signal generation unit 20 and the second motor control unit 24A perform the processing of steps S402 and S404.

In order to perform the processing of the flowchart of fig. 12, the motor speed determination unit 223 receives the motor speed estimation value ω estimated by the first motor speed estimation unit 13_{m_e}And the motor speed estimated by the second motor speed estimating section 14Estimated value omega_{sl_e}。

In fig. 12, in step S401, the motor speed estimated value and the motor speed command value are compared with each other for the motors 41 and 42. In determining the magnitude relationship between the motor speed estimated value and the motor speed command value, it is preferable to provide the motor speed command value with a margin in order to prevent erroneous determination or to prevent fluctuations in determination.

In step S401, if the estimated motor speed value of at least one motor is greater than "motor speed command value + margin" (yes in step S401), it is determined that there is step-out (step S402). When it is determined that step-out is present, a determination result Sout3 indicating that step-out is present is input to the PWM signal generation unit 20. In step S402, control is performed when there is step-out.

In step S401, if the estimated motor speed values of all the motors are equal to or less than "motor speed command value + remaining amount" (no in step S401), the process proceeds to step S403. In step S403, if the estimated motor speed value of any motor is smaller than "motor speed command value — margin" (yes in step S403), it is determined that there is step loss (step S404). When it is determined that step-out is present, a determination result Sout3 indicating that step-out is present is input to the PWM signal generation unit 20. In step S404, control is performed when there is step-out.

In step S403, if the motor speed estimated values of all the motors are equal to or greater than "motor speed command value — margin" (no in step S403), it is determined that there is no step-out (step S405), and a determination result Sout3 indicating that there is no step-out is input to the PWM signal generation unit 20. In this case, the control executed by the second motor control unit 24A is not executed, and the processing of the flowchart in fig. 12 is ended.

On the other hand, when there is step-out, the control performed by the second motor control unit 24A is performed. The specific processing contents are as described above, and the description thereof is omitted.

In embodiment 2, the control executed by the second motor control unit 24A is executed when at least 1 of the determination results Sout2 and Sout3 is out of step, and is not executed when both the determination results Sout2 and Sout3 are out of step.

In the determination process of step S401, the case where the motor speed estimated value of the motor is equal to "motor speed command value + remaining amount" is determined as no, but may be determined as yes. That is, the motor speed estimated value of the motor can be determined to be either "yes" or "no" when it is equal to the "motor speed command value + margin".

In the determination process of step S403, the case where the motor speed estimated value of the motor is equal to the "motor speed command value — remaining amount" is determined as no, but may be determined as yes. That is, the motor speed estimated value of the motor can be determined to be equal to the "motor speed command value — remaining amount" as either "yes" or "no".

As described above, according to the motor drive device of embodiment 2, when at least one of the determination result of step-out based on the motor current and the determination result of step-out based on the motor speed is step-out, the second control executed by the second motor control unit 24A is executed. Accordingly, a current proportional to the induced voltage of each motor flows to the inverter 4, and the regenerative energy of each motor is consumed. Accordingly, the motor can be stopped in a shorter time than when each motor is decelerated by the inertia moment.

In fig. 10, the motor current determination unit 222 and the motor speed determination unit 223 are configured in the step-out detection unit 22A, and determination results Sout2 and Sout3 of these determination units are independently input to the PWM signal generation unit 20. Specifically, the structure may be configured as shown in fig. 13 instead of the structure shown in fig. 10. Fig. 13 is a block diagram showing a first modification of the control system constructed in the control device according to embodiment 2.

In fig. 13, in the control system of the control device according to the first modification of embodiment 2, the out-of-step control unit 30A is replaced with an out-of-step control unit 30B in the configuration of the control system of the control device shown in fig. 10. In the step-out control unit 30B, the step-out detection unit 22A is replaced with the step-out detection unit 22B. In fig. 13, the motor current determination unit 222 and the motor speed determination unit 223 are not shown. The step-out detector 22B includes a logical or circuit 224, and the determination results Sout2 and Sout3 described in the example of fig. 10 are input to the logical or circuit 224. The or logic circuit 224 outputs the logic of the determination results Sout2 and Sout3 to the PWM signal generation section 20 as the determination result Sout4 of the step-out detection section 22B. The PWM signal generation unit 20 performs the above-described second control of bringing any one of 1 or more switching elements of the upper arm and 1 or more switching elements of the lower arm of the inverter 4 into the on state, based on the determination result Sout 4.

In addition, the structure may be configured as shown in fig. 14 instead of the structure shown in fig. 10. Fig. 14 is a block diagram showing a second modification of the control system constructed in the control device according to embodiment 2.

In fig. 14, in the control system of the control device according to the second modification of embodiment 2, the out-of-step control unit 30B is replaced with an out-of-step control unit 30C in the configuration of the control system of the control device shown in fig. 13. In the step-out control section 30C, the second motor control section 24A is replaced with the second motor control section 24. The second motor control section 24 is the same as that shown in fig. 4. The other structures are the same as or equivalent to those of fig. 13, and the same reference numerals are assigned to the same or equivalent structural parts, and redundant description thereof is omitted.

In the case of the control device according to the second modification of embodiment 2, as described in embodiment 1, the second motor control unit 24 performs the first control of stopping the motor while suppressing the peak value of the motor current. In the first control, as described above, current control in which a harmonic component is superimposed on the motor current may be performed, or current control in which the current command value is set to, for example, 0[ a ] may be performed.

Embodiment 3.

Fig. 15 is a block diagram showing a configuration example of a control system constructed in the control device of embodiment 3. In fig. 15, in the configuration of the control system according to embodiment 3, out-of-step control unit 30B is replaced with out-of-step control unit 30D in the configuration of the first modification example of embodiment 2 shown in fig. 13. In the step-out control unit 30D, the step-out detection unit 22B is replaced with a step-out detection unit 22C, and the or circuit 224 is replaced with a or circuit 225. The step-out detection unit 22C is a unit obtained by adding the function of the current direction determination unit 221 shown in fig. 4 to the function of the step-out detection unit 22B shown in fig. 13. In fig. 15, the current direction determining unit 221, the motor current determining unit 222, and the motor speed determining unit 223 are not shown. The other structures are the same as or equivalent to those of embodiment 1, and the same reference numerals are assigned to the same or equivalent structural parts, and redundant description thereof is omitted.

The determination results Sout1, Sout2, and Sout3 of the current direction determination unit 221, the motor current determination unit 222, and the motor speed determination unit 223 are input to the or circuit 225. The or logic circuit 225 outputs the logical or of the determination results Sout1, Sout2, Sout3 to the PWM signal generation section 20 as the determination result Sout5 of the step-out detection section 22C. The PWM signal generation unit 20 performs the above-described second control of bringing any one of 1 or more switching elements of the upper arm and 1 or more switching elements of the lower arm of the inverter 4 into the on state, based on the determination result Sout 5.

The control device of embodiment 3 has 3 determination conditions, and performs out-of-step control when there is out-of-step in at least one of the determination conditions. This makes it possible to obtain an effect of performing out-of-step control capable of accurately grasping the sign of out-of-step.

In embodiment 3 shown in fig. 15, the second control is executed when at least one motor is out of step, but the present invention is not limited thereto. The first control may be executed when at least one motor is out of step, as in fig. 14. Further, the functions of both the first control and the second control may be provided, and both may be switched in time series to be implemented. That is, the first control may be executed first, and then the first control may be switched to the second control to be executed. Further, the second control may be first executed, and then the second control may be switched to the first control to be executed. This can reduce the peak value of each motor current in the initial stage of the step-out occurrence, and also reduce the stop time of the motor.

Embodiment 4.

Fig. 16 is a block diagram showing a configuration example of a control system configured by the control device according to embodiment 4. In fig. 16, in the configuration of the control system according to embodiment 4, the out-of-step control unit 30D is replaced with the out-of-step control unit 30E in the configuration of the control device according to embodiment 3 shown in fig. 15. In the step-out control unit 30E, the step-out detection unit 22C is replaced with the step-out detection unit 22D, and the second motor control unit 24A is replaced with the second motor control unit 24B. The second motor control unit 24B has functions of both the second motor control unit 24 and the second motor control unit 24A. In fig. 16, the determination information CS is input from the step-out detection unit 22D to the second motor control unit 24B. The other structures are the same as or equivalent to those of embodiment 3, and the same reference numerals are given to the same or equivalent structural parts, and redundant description thereof is omitted.

Next, the operation of the main part of embodiment 4 will be explained. Fig. 17 is a flowchart for explaining operations of the step-out detection unit 22D and the second motor control unit 24B according to embodiment 4. In fig. 17, the processes of steps S501, S502, and S505 are performed by the step-out detection unit 22D, and the processes of steps S503, S504, and S506 are performed by the PWM signal generation unit 20 and the second motor control unit 24B.

In fig. 17, it is determined in step S501 whether or not step-out has occurred. As to whether or not step-out is present, at least one of the current direction determination unit 221, the motor current determination unit 222, and the motor speed determination unit 223, or a determination unit using these is used. If step loss is not detected (no in step S501), the determination process in step S501 is continued. On the other hand, when step loss is detected (yes in step S501), the process proceeds to step S502.

In step S502, it is determined whether the number of motors out of step is the same as the number of motors already in operation. If the number of motors out of step is the same as the number of motors already in operation (yes in step S502), the process proceeds to step S503. In step S503, the second control suitable for the situation is selected and executed. As described above, the second control is control for bringing any 1 or more switching elements of the upper arm or the lower arm of the inverter 4 into a conductive state. The presence or absence of step-out is transmitted from the step-out detection unit 22D to the second motor control unit 24B using the determination information CS. The same applies to the subsequent processing.

If the number of motors out of synchronization is different from the number of motors already in operation (no in step S502), the process proceeds to step S504. In step S504, the first control suitable for the situation is selected and executed. As described above, the first control is current control performed by the current controller 241 provided in the second motor control unit 24 in fig. 4.

After the processing in steps S503 and S504, the process proceeds to step S505. In step S505, the peak value of each motor current is compared with a current threshold value, each motor speed estimation value is compared with a speed threshold value, and the elapsed time after step-out detection is compared with a time threshold value. In step S505, when the peak value of each motor current is smaller than the current threshold value, or each motor speed estimated value is smaller than the speed threshold value, or the elapsed time after step out detection is larger than the time threshold value (yes in step S505), the process proceeds to step S506. That is, the condition for transition to step S506 is when at least one of the peak value of each motor current, each motor speed estimated value, and the elapsed time after step out detection satisfies the determination condition based on each threshold value.

On the other hand, if the peak value of each motor current is equal to or greater than the current threshold value, the estimated value of each motor speed is equal to or greater than the speed threshold value, and the elapsed time after the step-out detection is equal to or less than the time threshold value (no in step S505), the process returns to step S501, and the processes from step S501 to step S504 are repeated. That is, the condition for returning to step S501 is when all of the peak value of each motor current, each motor speed estimated value, and the elapsed time after step out detection have not reached the determination conditions based on the respective threshold values.

In step S506, control is performed to make all the switching elements of the inverter 4 non-conductive. Hereinafter, this control is referred to as "third control" as appropriate in order to distinguish from the first control and the second control described above. By this third control, the output voltage to each motor output from the inverter 4 is cut off. Since the electrical connection between the inverter 4 and each motor is eliminated, a current flowing in proportion to the induced voltage of each motor flows as a circulating current between the motors. The circulating current can consume the regenerative energy of each motor, and each motor can be stopped in a shorter time than when each motor is stopped by the inertia moment.

As described above, according to the motor drive device of embodiment 4, based on the information of the difference between the number of motors that are out of step and the number of motors that are already operating, control suitable for the situation of the difference is selected. Accordingly, it is possible to safely and reliably perform control for shortening the stop time of the motor while reducing the peak value of each motor current in the initial stage of the occurrence of step-out.

Embodiment 5.

In embodiment 5, an application example of the motor driving device described in embodiments 1 to 4 will be described. Fig. 18 is a diagram showing an example in which the motor drive device of embodiment 5 is applied to an air conditioner.

In fig. 18, an inverter 4, a plurality of fans 41a, 42a, and motors 41, 42 for driving the fans 41a, 42a are mounted on an outdoor unit 70 of an air conditioner 100. In the air conditioner 100, when the two fans 41a and 42a are driven, the number of inverters 4 can be reduced by operating the two motors 41 and 42 with 1 inverter 4. This can reduce the cost of the air conditioner 100.

In embodiment 5, a case where the motor driving device of embodiments 1 to 4 is applied to an air conditioner is described, but the present invention is not limited to this example. The motor driving devices of embodiments 1 to 4 can also be applied to refrigeration circuit apparatuses such as heat pump water heaters, refrigerators, and freezers. In any case, the effects obtained by the respective embodiments can be enjoyed.

The configuration described in the above embodiment is an example of the contents of the present invention, and may be combined with other known techniques, and a part of the configuration may be omitted or modified within a range not departing from the gist of the present invention.

For example, in the above description, the step-out control unit detects the step-out of the motor based on a change in the direction of the motor current flowing through each phase of the plurality of motors, a detected value of the motor current, or a speed estimated value of the plurality of motors, but is not limited thereto. The step-out control unit may detect step-out of the motor using at least two determination elements of a change in direction of a motor current flowing through each phase of the plurality of motors, a detected value of the motor current, and a speed estimation value of the plurality of motors.

In embodiment 3, the case where the first control and the second control are switched in time series when at least one motor is out of step has been described, but the present invention is not limited thereto. The third control described in embodiment 4 may be added, and the first control, the second control, and the third control may be performed by switching in time series.