JP6074235B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device, and more particularly to a motor control device capable of driving a motor in a plurality of modes.

  Conventionally, in a motor control device, an inverter for motor control is employed to control the rotational speed of the motor. In the motor control device, since the DC power output from the rectifier includes fluctuations, an electrolytic capacitor for absorbing and smoothing the fluctuations is used.

FIG. 5 is a diagram illustrating a configuration of a conventional general motor control device.
Referring to FIG. 5, in order to drive synchronous motor 100 having a stator having a plurality of (three-phase) coils and a rotor having permanent magnets, the motor control device includes inverter 150, converter circuit 130, and AC power supply 160. , Coil 170, current sensor 180, and controller 110. In this example, it is assumed that the AC power supply 160 is 200 V and 50 Hz.

  Synchronous motor 100 is driven by inverter 150, and inverter 150 is supplied with AC circuit 160 converted from converter circuit 130 into a direct current.

  Specifically, converter circuit 130 includes a diode full-wave rectifier circuit 120 formed of a plurality of diodes and a smoothing capacitor 140 between buses, and the capacity of the smoothing capacitor is such that the ripple of the DC voltage waveform can be improved. Big enough.

  The converter circuit 130 converts the AC voltage of the AC power supply 160 into a DC voltage and supplies it to the inverter 150.

  The coil 170 is provided for the purpose of improving the power factor of the AC power supplied to the converter circuit 130.

  In the conventional configuration as shown in FIG. 5, when the motor is driven, the electrolytic capacitor is constantly charged and discharged and continues to self-heat regardless of the ambient temperature of the motor control device. The life of electrolytic capacitors is highly temperature-dependent, and as the temperature rises, the life is shortened. Therefore, especially when the electrolytic capacitor is operated under high ambient temperature, the life is greatly shortened. . That is, the lifetime of such a conventional motor control device is greatly influenced by the lifetime of the electrolytic capacitor included in the motor control device.

  Therefore, as a countermeasure for the above problem, AC power of AC power supply is obtained by a method of obtaining AC output by a PWM inverter after obtaining DC output from AC power supply by sine wave PWM converter operation, or by matrix converter operation of switching control by switching a switch circuit. A method for directly converting electric power into AC power having different amplitude and frequency, or the following method is disclosed.

  According to Japanese Patent Laying-Open No. 2008-048587 (Patent Document 1), an AC / AC power converter is disclosed. AC / AC power converter obtains AC output from voltage source inverter through full-wave rectifier circuit capable of bi-directional power transfer by performing constant current width control synchronized with diode rectifier and same power source from AC power source . For this reason, the AC / AC power converter can be configured without an electrolytic capacitor because bidirectional power can be exchanged between the AC power supply and the AC output, and the switching problem in the rectifier circuit section is reduced.

JP 2008-048587 A

  However, according to the method described in Patent Document 1, since the circuit is completely configured without an electrolytic capacitor, voltage smoothing by the electrolytic capacitor is not always performed. In this method, since it is necessary to control the motor without smoothing the voltage, there are many technical problems such as it is difficult to control the rotational speed of the motor finely and stably.

  The present invention has been made to solve the above-described problems, and provides a motor control device capable of extending the life of an electrolytic capacitor while ensuring the stability of driving of the motor. Objective.

  According to an embodiment, a motor controller for controlling a motor is provided. The motor control device includes a rectifier circuit that receives a single-phase AC power source, a smoothing capacitor that smoothes the DC power obtained by the rectifier circuit, and a switch that connects or disconnects the rectifier circuit and the smoothing capacitor. And an inverter that drives the motor by converting DC power to AC power, and a controller that controls the switch and the inverter. The controller controls connection or disconnection between the rectifier circuit and the smoothing capacitor by the switch based on a predetermined condition, and controls the inverter in the first control mode or the second based on the predetermined condition. Inverter control means for controlling in the control mode.

  Preferably, a temperature sensor for detecting a temperature around the motor control device is further included. The connection control means controls connection or disconnection between the rectifier circuit and the smoothing capacitor based on the detected temperature.

  Preferably, it further includes a time measuring means for measuring the usage period of the motor control device. The connection control means controls connection or disconnection between the rectifier circuit and the smoothing capacitor based on the detected temperature when the usage period exceeds a predetermined period.

  Preferably, the connection control means shuts off the rectifier circuit and the smoothing capacitor when the ambient temperature of the motor control device is equal to or higher than a predetermined temperature, and the ambient temperature of the motor control device is predetermined. When the temperature is lower than the specified temperature, the rectifier circuit and the smoothing capacitor are connected.

  Preferably, the motor control device is configured to be mountable on an air conditioner. The temperature sensor detects the temperature around the outdoor unit included in the air conditioner.

  It is possible to extend the life of the electrolytic capacitor while ensuring the driving stability of the motor.

1 is a block diagram of a motor control device according to a first embodiment. It is a figure which shows an example of the temperature dependence of the lifetime of an electrolytic capacitor. 5 is a flowchart for illustrating a control method in a controller according to the first embodiment. 6 is a flowchart for illustrating a control method in a controller according to a second embodiment. It is a figure which shows the structure of the conventional general motor control apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a block diagram of a motor control device according to the first embodiment.

  Referring to FIG. 1, a motor control device according to a first embodiment includes a synchronous motor 1 having a stator having a plurality of (three-phase) coils and a rotor having a permanent magnet, an inverter 2, a converter circuit 3, The AC power source 4, current sensor 5, motor current detection amplifier unit 6, zero cross detection unit 30, voltage sensor 31, and controller 7 that is a microcomputer are included.

  The synchronous motor 1 is driven by an inverter 2, and is supplied to the inverter 2 by converting the AC voltage of the AC power supply 4 from the converter circuit 3 into DC. The inverter 2 converts the supplied DC power into AC power and drives the synchronous motor 1.

  Specifically, the converter circuit 3 includes a plurality of diodes and forms a full-wave rectifier circuit 33 that receives a single-phase AC power supply 4 as an input. In this example, a small-capacitance capacitor 34 connected in parallel to the inverter 2 is provided between the buses. The small-capacitance capacitor 34 is 100 μF or less. Specifically, it is preferable to use a capacitor of about 10 to 20 μF in view of preventing breakdown of the semiconductor element of the inverter 2 due to regenerative energy of the synchronous motor 1 on the load side. The capacity of the small-capacitance capacitor 34 is about 1/100 of the smoothing capacitor 35 described later. The small-capacitance capacitor 34 is a film capacitor of a different type from the smoothing capacitor 35 made of an electrolytic capacitor. The converter circuit 3 may be configured not to include the small capacitor 34.

  Between the buses, a smoothing capacitor 35 for smoothing the DC power obtained by the full-wave rectifier circuit and a switch 36 for connecting or blocking the smoothing capacitor 35 to the buses are included. Specifically, the switch 36 is for connecting or blocking between the full-wave rectifier circuit 33 and the smoothing capacitor 35. The capacity of the smoothing capacitor 35 is sufficiently large to improve the ripple of the DC voltage waveform. Further, the smoothing capacitor 35 has characteristics as shown in FIG. 2 in accordance with “Arrhenius Law”.

FIG. 2 is a diagram illustrating an example of the temperature dependence of the lifetime of the electrolytic capacitor.
Referring to FIG. 2, smoothing capacitor 35 has a characteristic that the lifetime is halved when the temperature is increased by 10 ° C., and conversely, the lifetime is doubled when the temperature is decreased by 10 ° C.

  When a ripple current is applied, the smoothing capacitor 35 self-heats due to heat loss. Therefore, when calculating the life of the smoothing capacitor 35, it is necessary to consider the ambient temperature (ambient temperature) of the motor control device and the temperature rise due to self-heating.

  Even when the small-capacitance capacitor 34 is provided as in this example, as described above, the small-capacitance capacitor 34 is a film capacitor, so that deterioration in use under a high-temperature and high-humidity environment is considered. In addition, the life is longer than that of the smoothing capacitor 35 which is an electrolytic capacitor. Therefore, the product life of the motor control device as a whole does not affect the life of the small-capacitance capacitor 34 and is greatly affected by the life of the smoothing capacitor 35.

  Referring again to FIG. 1, current sensor 5 detects motor current a flowing in a specific phase (U phase in FIG. 1) among motor coil terminals U, V, and W. The motor current detected by the current sensor 5 is given to the motor current detection amplifier unit 6.

  The motor current detection amplifier 6 amplifies the motor current signal b by a predetermined amount and adds the offset to the controller 7.

  The voltage sensor 31 detects the voltage of the AC power supply 4. The AC voltage detected by the voltage sensor 31 is given to the zero cross detection unit 30.

  Then, the zero-cross detection unit 30 monitors the AC voltage detected by the voltage sensor 31, generates a zero-cross point signal when it crosses 0V, and gives it to the controller 7.

  The temperature sensor 40 is a sensor for detecting the temperature around the motor control device, and gives temperature information indicating the detected temperature to the controller 7.

  The time measuring unit 50 is a part for measuring time, and sends a signal corresponding to the time measured to the controller 7. In a certain aspect, the timer 50 measures the usage period of the motor control device. Here, the period of use refers to, for example, a period from the time when the motor control device is manufactured to the time of shipment. Based on the signal, the controller 7 executes a predetermined process when a predetermined time has elapsed.

  The controller 7 controls the switch 36 and the inverter 2. Specifically, the controller 7 includes an inverter control unit 10, a connection control unit 13, and a processing unit 14. These functions are basically realized by the controller 7 executing a program stored in a memory (not shown) and giving a command to the components of the controller 7. Note that some or all of these functional configurations may be realized by hardware.

  In one aspect, the processing unit 14 acquires temperature information from the temperature sensor 40 and determines whether or not the ambient temperature of the motor control device is equal to or higher than a predetermined reference temperature. In another aspect, the processing unit 14 acquires time information from the time measuring unit 50, determines whether or not the usage period of the motor control device exceeds a predetermined reference usage period, and the usage period is the reference level. When it is determined that the usage period has been exceeded, it is further determined whether the ambient temperature is equal to or higher than the reference temperature. The processing unit 14 outputs the determination result to the inverter control unit 10 and the connection control unit 13.

  The reference temperature is arbitrarily set according to the temperature characteristics of the life of the smoothing capacitor 35. The life of the smoothing capacitor 35 is preferably calculated by measuring the smoothing capacitor 35 under various temperature conditions during the evaluation of the prototype. Further, the reference usage period is arbitrarily set according to the life of the smoothing capacitor 35.

  The connection control unit 13 controls connection or disconnection between the full-wave rectifier circuit 33 and the smoothing capacitor 35 by the switch 36 based on a predetermined condition (result of determination by the processing unit 14). More specifically, the connection control unit 13, in one aspect, is based on the ambient temperature of the motor control device detected by the temperature sensor 40, and is connected between the full-wave rectifier circuit 33 and the smoothing capacitor 35 by the switch 36. Control connection or disconnection. More specifically, the connection control unit 13 blocks between the full-wave rectifier circuit 33 and the smoothing capacitor 35 when the ambient temperature is equal to or higher than the reference temperature, and when the ambient temperature is lower than the reference temperature. The full-wave rectifier circuit 33 and the smoothing capacitor 35 are connected. In another aspect, the connection control unit 13 performs connection or disconnection between the full-wave rectifier circuit 33 and the smoothing capacitor 35 based on the ambient temperature when the usage period exceeds a predetermined reference period. Control.

  The inverter control unit 10 controls the inverter 2 in the first mode or the second mode based on the predetermined condition (the determination result in the processing unit 14). More specifically, the inverter control unit 10 includes a first inverter control unit 11 for controlling the inverter 2 in the first mode, and a second inverter control for controlling the inverter 2 in the second mode. Part 12. More specifically, the inverter control unit 10 operates (functions) as the second inverter control unit 12 for controlling the inverter 2 in the second mode when the ambient temperature is equal to or higher than the reference temperature. When the ambient temperature is lower than the reference temperature, it operates (functions) as the first inverter control unit 11 for controlling the inverter 2 in the first mode. In another aspect, the inverter control unit 10 controls the inverter 2 in the first or second mode based on the ambient temperature when the usage period exceeds a predetermined reference usage period.

  Here, the first mode and the second mode which are control modes in the inverter control unit 10 will be described. From the above, basically, when the connection control unit 13 is in a state where the full-wave rectifier circuit 33 and the smoothing capacitor 35 are connected (a state where the switch 36 is turned on), the inverter control unit 10 The inverter control unit 10 operates as the first inverter control unit 11, and when the full-wave rectifier circuit 33 and the smoothing capacitor 35 are disconnected (the switch 36 is turned off), the inverter control unit 10 2 as the inverter control unit 12.

  When the switch 36 is in the ON state, since the full-wave rectifier circuit 33 and the smoothing capacitor 35 are connected, the DC voltage obtained by the full-wave rectifier circuit 33 can be smoothed, and the ripple of the DC voltage waveform can be reduced. Can be improved. Therefore, as the first mode of the inverter control unit 10, for example, a conventional general PWM (pulse width modulation) switching control method controlled by the controller 110 shown in FIG. 5 is adopted. The first inverter control unit 11 that controls the inverter 2 in the first mode turns on and off the drive element of the inverter 2 in order to create an AC voltage whose voltage and polarity change from the smoothed DC voltage. The first inverter control unit 11 changes the output voltage by changing the on / off time ratio, and changes the polarity by changing the combination of switching.

  On the other hand, since the full-wave rectifier circuit 33 and the smoothing capacitor 35 are cut off when the switch 36 is in the OFF state, the DC voltage obtained by the full-wave rectifier circuit 33 cannot be sufficiently smoothed. The ripple of the DC voltage waveform becomes large. Therefore, as the second mode of the inverter control unit 10, a control system that realizes stable driving of the motor is adopted even under the condition that a large ripple is generated in the DC voltage. For example, as described in Japanese Patent Application Laid-Open No. 2011-78153, the motor drive is stabilized by correcting the number of rotations of the motor in accordance with the elapsed time from the detection of the zero-cross point of the single-phase AC power supply. A control method is adopted.

  More specifically, the zero-cross detection unit 30 monitors the AC voltage detected by the voltage sensor 31, generates a zero-cross point signal when it crosses 0V, and gives it to the controller 7. The second inverter control unit 12 of the controller 7 sets a target rotational speed command for the synchronous motor 1 and stores correction rate data for the target rotational speed. The second inverter control unit 12 extracts correction rate data according to the elapsed time of the zero cross point signal generated by the zero cross detection unit 30 from the rotation speed correction rate data table, and the setting is performed according to the extracted correction rate data. Correct the rotation speed. The second inverter control unit 12 reads out sine wave data corresponding to each phase of the motor coils U, V, and W from the sine wave data table according to the corrected rotational speed command and the passage of time, and the U-phase sine wave U-phase motor drive voltage phase information is output from the wave data. And the 2nd inverter control part 12 outputs a PWM waveform to the drive element of the inverter 2 for every phase from sine wave data and a duty reference value.

  FIG. 3 is a flowchart for illustrating a control method in controller 7 according to the first embodiment.

  The controller 7 determines whether or not to start the operation of the motor control device (step S102). When the operation is not started (NO in step S102), the controller 7 repeats the process of step S102. When the operation is started (YES in Step S102), the controller 7 acquires temperature information around the motor control device via the temperature sensor 40 (Step S104).

  Next, based on the acquired temperature information, when the ambient temperature is lower than a predetermined reference temperature (NO in step S106), the controller 7 executes processing after step S112 described later. . In contrast, when the ambient temperature is equal to or higher than a predetermined reference temperature (YES in step S106), controller 7 turns off switch 36 (step S108). More specifically, the controller 7 controls the switch 36 to disconnect between the full-wave rectifier circuit 33 and the smoothing capacitor 35. Next, the controller 7 controls the inverter 2 in the second mode (step S110).

  Next, the controller 7 determines whether or not to stop the operation of the motor control device (step S116). If the operation is not stopped (NO in step S116), the controller 7 repeats the processing from step S104. On the other hand, when stopping the operation (YES in step S116), the controller 7 stops the operation and ends the process.

Here, the process after step S112 is demonstrated.
When the ambient temperature of the motor control device is lower than a predetermined reference temperature (NO in step S106), controller 7 turns on switch 36 (step S108). More specifically, the controller 7 controls the switch 36 to connect the full-wave rectifier circuit 33 and the smoothing capacitor 35. Next, the controller 7 controls the inverter 2 in the first mode (step S114), and executes the processing after step S116 described above.

  In the above, the controller 7 may be executed by changing the order of Step S108 and Step S110 or the order of Step S112 and Step S114. Or you may perform the process of step S108 and step S110, or the process of step S112 and step S114 simultaneously.

  According to the above, when the ambient temperature of the motor control device is equal to or higher than the reference temperature, the controller 7 has severe operating conditions for the life of the smoothing capacitor 35. The inverter 2 is controlled in this mode. That is, since the smoothing capacitor 35 is not operated under severe operating conditions where the ambient temperature is high, it is possible to prevent the life of the smoothing capacitor 35 from being significantly shortened.

  On the other hand, when the ambient temperature of the motor control device is lower than the reference temperature, the controller 7 does not have a severe operating condition for the life of the smoothing capacitor 35. Therefore, the smoothing capacitor 35 is connected to the bus, The inverter is controlled in the first mode. Rather than disconnecting the smoothing capacitor 35 from the bus and controlling the inverter in the second mode, it is more stable to connect the smoothing capacitor 35 to the bus and control the inverter in the first mode. This is because it can be driven and can contribute to energy saving.

  As described above, according to the first embodiment, the motor can be driven stably by switching the connection state of the smoothing capacitor and the control method of the inverter according to the temperature condition, and the life of the smoothing capacitor can be reduced. Can extend the life of the motor control device.

[Embodiment 2]
In the second embodiment, a modification of the control method in the controller 7 according to the first embodiment will be described. Since the configuration of the motor control device according to the second embodiment is the same as that of the motor control device (FIG. 1) according to the first embodiment, detailed description thereof will not be repeated.

  FIG. 4 is a flowchart for illustrating a control method in controller 7 according to the second embodiment.

  The controller 7 determines whether or not to start the operation of the motor control device (step S102). When the operation is not started (NO in step S102), the controller 7 repeats the process of step S102. When starting the operation (in the case of YES in step S102), the controller 7 determines whether or not the usage period of the motor control device exceeds a predetermined reference usage period via the timer unit 50 ( Step S202). If the usage period exceeds the reference usage period (YES in step S202), the processes after step S104 are executed. Since the process after step S104 is the same as that of FIG. 4, the detailed description thereof will not be repeated.

  On the other hand, when the usage period does not exceed the reference usage period (NO in step S202), the processes after step S112 are executed. Since the process after step S112 is the same as that of FIG. 4, the detailed description thereof will not be repeated.

  According to the above, when the usage period does not exceed the reference usage period, the controller 7 maintains the switch 36 in the ON state regardless of the ambient temperature of the motor control device, and the inverter 2 in the first mode. Control. When the usage period exceeds the reference usage period, the controller 7 controls ON / OFF of the switch 36 based on the ambient temperature of the motor control device, as in the first embodiment, and the first or The inverter 2 is controlled by switching the second mode.

  As described above, in the second embodiment, by setting the reference usage period to a period in which the life of the smoothing capacitor 35 remains to some extent, the motor control is performed so that the motor can be driven more stably during that period. The device is controlled. When the life of the smoothing capacitor 35 is reduced, the same control as in the first embodiment is performed.

  As described above, according to the second embodiment, it is possible to extend the life of the electrolytic capacitor, and hence the life of the motor control device, while ensuring the stability of driving of the motor and maximizing the contribution to energy saving. .

[Embodiment 3]
The motor control device described in the first and second embodiments can be used as a motor control device for a compressor mounted in an air conditioner or a refrigerator.

  For example, an air conditioner is configured such that a motor control device can be mounted on the outdoor unit. In this case, the temperature around the outdoor unit (outside air temperature) is detected by the temperature sensor 40 included in the motor control device.

  Therefore, even when an air conditioner equipped with the motor control device is used in a place with a high year-round temperature such as a tropical region, the stability is ensured by the control method described in the first and second embodiments. However, since the life of the electrolytic capacitor can be extended, the product life as an air conditioner can also be extended.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1,100 synchronous motor, 2,150 inverter, 3,130 converter circuit, 4,160 AC power supply, 5,180 current sensor, 6 motor current detection amplifier unit, 7,110 controller, 10 inverter control unit, 11 first Inverter control unit, 12 second inverter control unit, 13 connection control unit, 14 processing unit, 30 zero cross detection unit, 31 voltage sensor, 33 full-wave rectifier circuit, 34 small-capacitance capacitor, 35, 140 smoothing capacitor, 36 switch, 40 temperature sensor, 50 timing unit, 120 diode full-wave rectifier circuit, 170 coil.

Claims (3)

A motor control device for controlling a motor,
A rectifier circuit with a single-phase AC power supply as input,
A smoothing capacitor that smoothes the DC power obtained by the rectifier circuit;
A switch for connecting or disconnecting between the rectifier circuit and the smoothing capacitor;
An inverter that drives the motor by converting DC power into AC power;
A temperature sensor for detecting the ambient temperature of the motor control device;
A controller for controlling the switch and the inverter;
The controller is
When the ambient temperature of the motor control device is smaller than the reference temperature set from the relationship between the life and temperature of the smoothing capacitor, the switch connects the rectifier circuit and the smoothing capacitor, and the motor control device When the ambient temperature is equal to or higher than the reference temperature, connection control means for cutting off the rectifier circuit and the smoothing capacitor by the switch,
When the ambient temperature of the motor control device is lower than the reference temperature, the inverter is controlled in a first control mode, and when the ambient temperature of the motor control device is equal to or higher than the reference temperature, the first Unlike the first control mode, the inverter includes an inverter control means for controlling the inverter in a second control mode for performing control for correcting the motor rotation speed in accordance with the elapsed time from detection of the zero cross point of the single-phase AC power supply. , Motor control device. Further comprising time measuring means for measuring the period of use of the motor control device,
The connection control means controls connection or disconnection between the rectifier circuit and the smoothing capacitor based on the detected temperature when the use period exceeds a predetermined period. The motor control device according to 1. The motor control device is configured to be mountable on an air conditioner,
The motor control device according to claim 1, wherein the temperature sensor detects a temperature around an outdoor unit included in the air conditioner .

Images