JP2023144354A - Control device for electric motor - Google Patents

Abstract

To solve the problem that an electric motor in which winding inductance is small cannot be re-driven from an idle state because a large current ripple may occur and make the electric motor go into an abnormal state when re-driving the electric motor from the idle state.SOLUTION: A control device for controlling an electric motor having a plurality of phase windings has an inverter that converts DC voltage to AC voltage of a sine wave and supplies the same to the electric motor, a control unit that generates a switching signal in accordance with a frequency of the sinusoidal AC voltage, and phase detection means for detecting a phase of the electric motor during idling and outputting a phase signal when an output of the switching signal from the control unit is stopped. The control unit generates a switching signal on the basis of the phase signal after temporarily setting the control frequency of the inverter to a higher level when the electric motor is re-driven from idling. Further, the control unit returns the control frequency of the inverter to the normal state immediately after the motor is successfully re-driven and the control is stabilized.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control device for an electric motor, and particularly to a sensorless control method and device that omit magnetic pole position detection means and motor current detection means.

Conventionally, in electric motor control devices, sensorless control technology that eliminates the magnetic pole position sensor for detecting the magnetic pole position of the motor or the motor current sensor has been developed with the aim of improving reliability by reducing parts and eliminating restrictions on installation location. Proposed.

In Patent Document 1, in this sensorless control, when the switching operation of the inverter is stopped, that is, when the motor is idling, a phase detection means detects the actual phase during the idling, and when the switching operation of the inverter is resumed, By using the above-mentioned actual phase, re-driving from the idle state is possible. Further, in Patent Document 2, when an electric motor is controlled by a synchronous PWM control method, even if the electric motor is driven from an idle state, occurrence of an electric shock is suppressed and abnormal conditions such as overcurrent and step-out occur. A motor control device that can reduce the

On the other hand, demand for lightweight vacuum cleaners is increasing, and the motors installed in them are also required to be further downsized. Generally, the smaller the motor, the smaller the winding inductance.

Japanese Patent Application Publication No. 2005-137106 Japanese Patent Application Publication No. 2020-005472

In the technology of re-driving a motor from an idling state (also called idling re-driving) as shown in Patent Documents 1 and 2, when an attempt is made to re-drive a motor with smaller winding inductance, a large current ripple occurs. , there is a possibility of falling into abnormal conditions such as overcurrent or loss of synchronization. As a countermeasure, it is possible to drive the motor with the inverter control frequency set higher and execute the method described in Patent Document 1, but it is impossible to use it in combination with the synchronous PWM control of Patent Document 2. In other words, at a high control frequency, circuit loss increases and the temperature of the inverter circuit increases.

An object of the present invention is to provide a control device for an electric motor that suppresses large current ripples when redriving the motor from an idling state in an electric motor having a small winding inductance, and can normally redrive the motor without falling into an abnormal state. purpose.

In order to solve the above-mentioned problems, the present invention is a motor control device that controls a motor having multiple phase windings, and includes an inverter that converts a DC voltage into a sine wave AC voltage and supplies it to the motor, and a sine wave AC voltage. a control unit that generates a switching signal according to the frequency of the AC voltage; and a phase detection unit that detects the phase of the motor during idling and outputs a phase signal when the output of the switching signal from the control unit is stopped. The control unit temporarily sets the control frequency of the inverter to a high value when the electric motor resumes idling, and then generates a switching signal based on the phase signal. Furthermore, after the re-driving is successful and the control becomes stable, the control frequency of the inverter is immediately returned to the normal state.

According to the present invention, it is possible to provide a control device for an electric motor with low winding inductance, which suppresses large current ripples and does not fall into an abnormal state even if the motor is idled again.

1 is a diagram showing a configuration example of a control device for an electric motor according to the present invention. It is a figure showing the appearance of a vacuum cleaner. FIG. 3 is a diagram showing a control block of a processing section of the electric motor control device of the present invention. FIG. 2 is a diagram showing the overall operation flow of the electric motor control device of the present invention. FIG. 3 is a diagram showing a processing flow of a phase signal of the electric motor control device of the present invention. FIG. 3 is a diagram showing an example of a circuit of a phase detection means of the present invention. FIG. 3 is a diagram showing the relationship between a phase signal and a divided voltage signal according to the present invention. FIG. 7 is a diagram showing another circuit diagram of the phase detection means of the present invention.

The present invention relates to a control device for a motor 103 that controls a motor 103 having multiple phase windings.As an embodiment of the present invention, a case where the present invention is applied to a control device for a vacuum cleaner 10 including the motor 103 will be described in detail below. explain.

FIG. 2 shows an external appearance of a vacuum cleaner 10 according to the present invention. FIG. 1 is a basic configuration diagram of a motor control device according to the present invention. In FIG. 1, a motor control device includes a rechargeable battery 100 that supplies energy, a smoothing capacitor 101, a motor 103 to which a fan 102 as a load is attached, a motor 103 that converts DC voltage into a sinusoidal AC voltage, and uses the converted AC power to drive the motor. An inverter 104 that outputs output to a motor (permanent magnet synchronous motor in this embodiment) which is 103, a driver circuit 105 that drives it, a microcomputer 106 that is a processing unit that outputs a PWM signal to the driver circuit 105, and a microcomputer 106 that detects the power supply voltage. voltage detection means 107, a switch signal generation section 108 that transmits a vacuum cleaner switch on/off signal, and a phase detection means 109 that stops power output from the inverter 104 and generates a magnetic pole position signal when the motor 103 is idling. , a DC current detector 110, an overcurrent detection circuit 111, and a DC current detection resistor 117.

In this way, this embodiment has a sensorless configuration in which means for directly detecting the magnetic pole position and motor current is omitted.

In addition, although the rechargeable battery 100 is used as an energy supply means in this figure, it is also possible to utilize DC power by using means for converting AC power into DC power.

When the switch signal 112 from the switch signal generator 108 is turned on, the microcomputer 106 detects the voltage of the rechargeable battery 100 using the voltage detection means 107 and also detects the current information 114 obtained from the DC current detector 110 regarding the magnetic pole position. It performs an output calculation and outputs a PWM waveform to the driver circuit 105. Inverter 104 is driven upon receiving this output, and supplies DC power from power supply 100 to electric motor 103 as AC power. As a result, the electric motor 103 and the fan 102 attached thereto rotate, generating suction force and obtaining wind power to suck the dust.

When the switch signal 112 changes from on to off, the microcomputer 106 receives the phase signal 113 from the phase detection means 109 and monitors the state of the motor 103 during idle rotation. The phase detection means 109 detects each back electromotive force from the wiring 116 of each phase connecting the electric motor 103 and the inverter 104, and outputs it to the microcomputer 106 as a phase signal 113.

Further, the switch signal generation unit 108 has several types of operation modes in addition to the on/off information. The microcomputer 106 controls the number of rotations and the like according to each operation mode, and changes the suction force.

In this embodiment, the phase detection means 109 detects the phase of the electric motor 103 during idling and outputs a phase signal when the output of the switching signal from the PWM generation circuit 243, which is the control section, is stopped. Yes, it is configured as shown in Figure 6. In FIG. 6, a case will be explained in which U-phase and V-phase back electromotive forces are used.

The voltage dividing circuits 150 and 151 divide the U-phase back electromotive force, and the voltage dividing circuits 152 and 153 divide the V-phase back electromotive force, and output the divided voltages to a comparator 160, which is a comparing circuit.

The comparator 160, which is a comparison circuit, compares a plurality of voltages obtained by dividing line voltages applied to a plurality of wirings between the stator winding of the motor 103 and the inverter 104. Specifically, the comparator 160 is a voltage dividing circuit. It receives signals 154 and 155 obtained from signals 150 to 153 and outputs H or L as a phase signal 113.

The relationship between these waveforms is as shown in FIG. 7, and is equivalent to a circuit that outputs either H or L using the zero-crossing point of the UV line voltage as a threshold.

In this embodiment, only the phase signal 113 is detected to monitor the idling state, but when rotating forward or reverse, the rotation direction is output by outputting the second phase signal 170 as shown in FIG. It is also possible to detect.

Next, the operation within the microcomputer 106, which is the processing section, will be explained using FIGS. 3 to 5.

In FIG. 3, the operation of the microcomputer 106 is comprised of a vector control system 200 and an idle phase detection system 300.

The vector control system 200 is a smart vector method proposed in Patent Documents 1 and 2, and corresponds to a configuration in which a magnetic pole position sensor and a motor current sensor are omitted. Except for the carrier frequency controller 245 and the idle re-drive request generator 246, the details are described in Patent Documents 1 and 2, so only an outline will be described here.

First, the phase current reproducer 201 reproduces the motor current from information obtained from the current information I _DC of the direct current from the amplifier 114. The dq converter 202 converts the three-phase Iu, Iv, and Iw alternating current information into a rotating coordinate system, and converts it into a torque current component Iqc and an excitation current component Idc.

Furthermore, the rotor position estimator 220 uses the control system to estimate the torque current component Iqc, the exciting current component Idc, and the voltage command values Vdc* and Vqc* that are the outputs of the voltage command calculator 240. The deviation Δθc between the obtained magnetic pole position and the actual magnetic pole position of the electric motor 103 is calculated. The deviation Δθc is reflected in the frequency command value ω1 by the PLL controller 221.

The voltage command calculator 240 calculates voltage command values Vdc* and Vqc* to be output from Id*, Iq*, and ω1*.

The carrier frequency controller 245 varies the control frequency Fc of the PWM generation circuit 243, which is a control section. The idle re-drive request generator 246, which is one input of the carrier frequency controller 245, determines whether there is an idle re-drive request based on the measured command value ωr* of the electric motor 103 and the frequency ωfr when the electric motor 103 idles. Specifically, when the switch 108 is pressed other than OFF, that is, when there is an operation request (ωr*≠0), if the idling frequency ωfr is sufficiently large, the motor waits until it stops and then restarts. Since it is faster to re-drive the motor during idling than to let it idle, re-driving the motor is requested. A control frequency Fc is output from the carrier frequency controller 245 depending on whether or not there is a request for idle re-driving. When using the synchronous PWM control method as shown in FIG. 3, Vdc*, Vdq*, θdc, and ω1* are input to the carrier frequency controller 245, and a control frequency Fc synchronized with ω1* is output. . It is assumed that the Fc output due to the request for idling re-drive is given priority over the Fc output due to synchronous PWM control. Although this temporarily results in asynchronous PWM control, it is possible to return to synchronous PWM control after the idle re-driving is completed using the procedure described later.

The dq converter 242 converts the voltage command values Vdc* and Vqc* into three-phase AC components Vu*, Vv*, and Vw*, and converts the voltage command values Vdc* and Vqc* into three-phase AC components Vu*, Vv*, and Vw*, and converts the voltage command values Vdc* and Vqc* into Vu*, Vv*, and Vw* according to the carrier frequency Fc that is the output of the carrier frequency controller. *, Vv*, and Vw* are output to the PWM generation circuit 243, which is a control section.

The PWM generation circuit 243, which is a control unit, generates a switching signal according to the frequency of the sine wave AC voltage, and uses these Vu*, Vv*, Vw* and the information Edc obtained from the voltage detection means 107. Based on this, an output pulse is output to the driver circuit 105, and the driver circuit 105 outputs the pulse to the inverter 104.

Note that the excitation current command value Id* is obtained by the d-axis current generator 241, and the torque current command value Iq* is obtained from the torque current feedback value Iqc via the filter 244.

The idling phase detection system 300 operates when the pulse output of the inverter 104 is stopped and the electric motor 103 is idling, and enables the electric motor 103 to be driven again from the idling state.

The idling phase detector 301 receives the phase signal 113 from the phase detection means 109 and updates the phase θfr at the timing when the signal level changes from H to L or from L to H.

The idling frequency measuring device 302 receives the phase signal 113 similarly to the idling phase detector 301, and calculates the idling frequency ωfr of the electric motor 103 for each change in the signal level.

The switch 310 switches the command value to be used depending on whether or not the electric motor 103 is idling.

During idle rotation, switch 310 selects state A. Therefore, the phase signal 113 from the phase detection means 109 is detected by the idling phase detector 301 and the idling frequency measuring device 302, making it possible to monitor the state of the electric motor 103 during idling.

Further, 0 is selected as the current command values Id*, Iq* to the voltage command generator 240, and the idling frequency ωfr is selected as the frequency command. As a result, it is possible to constantly calculate the voltage command value during idling, so that this voltage command value can be immediately used when re-driving the electric motor 103 from idling.

Switch 310 selects state B when motor 103 is completely stopped or when inverter 104 is outputting power to motor 103. Therefore, the phase detection system 300 during idling does not affect the vector control system 200 at all.

The flow of operation of the system in this embodiment will be described below with reference to FIGS. 4 and 5.
FIG. 4 shows the overall operation flow of this embodiment.

First, whether pulse output processing is being performed to the inverter 104 is determined in an inverter output status determination 401. At this time, if the output has been stopped, determination 405 is performed based on the idle frequency ωfr. Determination 405 is to determine whether re-driving is possible or not, and is less than a predetermined rotation speed of the motor 103 where the signal from the phase detection means 109 cannot be detected, or a predetermined rotation speed where the signal from the phase detection means 109 can be detected. It is determined whether or not the rotation speed of the electric motor 103 is higher than or equal to the rotation speed of the electric motor 103. Specifically, it is determined whether the idle frequency ωfr is equal to or greater than a predetermined lower limit value. If it is determined that re-driving is not possible, specifically, if the idling frequency ωfr is determined to be equal to or higher than a predetermined lower limit value, the switch 310 in the idling phase detection system 300 is set to B in step 407. Then, a stop process 408 is executed to stop the electric motor. In addition, when it is determined that the re-driving state is possible after idling, specifically, when it is determined that the idling frequency ωfr is smaller than a predetermined lower limit value, inverter control frequency speed-up processing 406 is performed. Later, in step 410, the switch 310 in the idling phase detection system 300 is set to A to prepare for re-driving.

If it is determined in determination 401 that pulses are being output to the inverter 104, the switch 310 in the idling phase detection system 300 is activated in determination 402. At this time, if the state is B, determination 411 is executed.

A determination 411 determines whether the control is stable. Whether or not the control has stabilized can be determined based on things like ``a specified time has elapsed since the restart of idling'', ``the magnetic pole position deviation Δθc is within the specified range'', and ``the magnitude of the motor phase current is equivalent to steady state''. . Furthermore, control stability may be defined using other parameters. When the control is stabilized, the control frequency Fc of the inverter is returned from the high set value to the normal set value in process 412, and voltage calculation process 409 is performed. In addition, when returning the control frequency Fc to the normal setting value, for both asynchronous PWM control and synchronous PWM control, the change is large and there is a possibility of a shock if the normal setting value is returned immediately. You can also take a step-by-step approach. On the other hand, if the control is not stable, voltage calculation 409 is performed as is, and the electric motor 103 is controlled.

If the determination result of determination 402 is state A, this indicates that the re-driving process from the time of idling is still being continued. As shown in FIG. 3, the current command values at this time are both 0, Id* and Iq*, and the frequency command value remains as it was immediately before starting pulse output to the inverter 104.

Therefore, in order to perform normal vector control and return to state B, the phase current waveform reproduced from the phase current reproducer 201 needs to be accurate. Therefore, state A continues until the phase current waveform is normally reproduced.

If it is determined in determination 403 that the current can be reproduced, then in process 404 the switch 310 is changed to state B for the first time and normal control is performed.

Next, processing executed every time the phase signal 113 changes while the electric motor 103 is idling will be described using FIG. 5.

While the electric motor 103 is idling, the phase signal detection processing 501 detects the state immediately after the phase signal 113 output from the phase detection means 109 changes.

Further, the idle frequency calculation processing 502 measures the time interval at which the phase signal 113 output from the phase detection means 109 changes.

The timing at which the phase signal 113 changes from H to L and from L to H always shows a one-to-one correspondence with the waveform of the detection circuit, that is, the magnetic pole position, as shown in FIG. Therefore, accurate phase information and idle frequency of the electric motor 103 can be accurately obtained.

The inverter output start determination 503 monitors the signal from the switch 108 and becomes valid when it is turned on. When the switch 108 is turned on, the magnetic pole position setting process 504 matches the phase held in the software with the actual magnetic pole phase. Next, an inverter output start processing request 505 is output that permits outputting pulses to the inverter 104. Finally, while power is being output from the inverter 104 to the electric motor 103, the phase detection means 109 sends out a meaningless phase signal. In order to prevent this from being accepted, interrupt prohibition processing 506 is executed.

As described above, in the present invention, when the electric motor 103 is re-driven from idling, if it is determined that re-driving during idling is impossible, stop control is performed, and after the rotation is stopped, the motor is re-driven. If it is determined that re-driving during idling is possible, the carrier frequency controller 245 temporarily sets the control frequency of the inverter to a high value and controls the inverter until the control becomes stable. Once the control is stabilized, the inverter control frequency is immediately returned to the normal control frequency and normal control is performed, allowing even motors with low winding inductance to be driven again without large current ripples.

By applying the present invention to a product such as a vacuum cleaner, which continues to rotate for several seconds even if the motor output is stopped under light load, and which can be switched on and off frequently, it can be used until the product is restarted. The effect of shortening the time can be obtained.

Note that in the above embodiment, an example of a vacuum cleaner including an electric motor has been described, but the present invention may be applied to other home appliances such as an electric washing machine.

10 Vacuum cleaner 100 Rechargeable battery 101 Smoothing capacitor 102 Fan 103 Motor 104 Inverter 105 Driver circuit 106 Microcomputer 107 Voltage detection means 108 Switch signal generation section 109 Phase detection means 110 DC current detector 111 Overcurrent detection circuit 160 Converter

Claims (6)

This is a motor control device that controls a motor having multiple phase windings, and includes an inverter that converts DC voltage into a sinusoidal AC voltage and supplies it to the motor, and a switching signal that is controlled according to the frequency of the sinusoidal AC voltage. a control unit that generates a switching signal; and a phase detection unit that detects a phase during idling of the electric motor and outputs a phase signal when the output of the switching signal from the control unit is stopped, and the control unit When re-driving the inverter from idling, the control frequency of the inverter is temporarily set high, a switching signal is generated based on the phase signal, and after confirming that the control is stable after re-driving, the control frequency of the inverter is set high. A control device for an electric motor, characterized in that the control frequency is returned to a normal state. 2. The electric motor control apparatus according to claim 1, wherein the electric motor is a permanent magnet synchronous motor. 2. The motor control device according to claim 1, wherein the phase detection means includes a comparison circuit that compares a plurality of voltages obtained by dividing line voltages applied to a plurality of wirings between the stator winding of the motor and the inverter. A control device for an electric motor. 4. The electric motor control device according to claim 1, wherein if the rotational speed of the electric motor is less than a predetermined number of rotations at which the signal from the phase detection means cannot be detected, stop control is performed, and after the rotation has stopped. , a control device for an electric motor that generates a switching signal based on a phase signal from the phase detection means when the motor is driven again and the signal from the phase detection means exceeds a detectable predetermined rotational speed of the motor. 5. The electric motor control device according to claim 1, wherein the electric motor is a vacuum cleaner motor. 5. The electric motor control device according to claim 1, wherein the electric motor is a motor for an electric washing machine.

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