JP2012090460A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller for synchronous motor, capable of achieving position sensorless sinewave energization with ensured stability by suppressing generation of a motor current pulsation even when a ripple of a DC voltage occurs.SOLUTION: A duty reference value correction section 18 corrects a duty reference value according to a duty reference value calculated by a PI calculation section 11 when the duty reference value is smaller than a predetermined threshold value. When the duty reference value is equal to or larger than the predetermined threshold value, on the other hand, a rotational speed correction section 16 corrects a target rotational speed according to a rotational speed correction rate following a lapsed time from the detection time of a zero cross point signal without correcting the duty reference value.

Description

  The present invention relates to a power converter control device including a converter that converts alternating current to direct current and an inverter that converts direct current to alternating current, and particularly when the synchronous motor is driven at a variable speed by the inverter without using a position sensor. The present invention relates to a motor control device suitable for suppressing a beat phenomenon accompanying commutation pulsation caused by commutation by a converter.

  Permanent magnet synchronous motors are widely used because they have excellent maintainability, controllability, and environmental resistance, and can be operated with high efficiency and high output. Synchronous reluctance motors that do not use permanent magnets are also actively studied as inexpensive and easy-to-recycle motors.

  In order to perform high-performance control of a synchronous motor such as a permanent magnet synchronous motor or a synchronous reluctance motor, it is important to pass a current corresponding to the position of the rotor. For this reason, a position sensor that detects the position of the rotor, such as a hall element, an encoder, or a resolver, is generally used in the motor control device, and self-controlled operation (speed feedback operation) is performed based on position detection information.

  However, when using a position sensor, it is not only a major factor that hinders downsizing of the device, but also requires multiple wires and receiving circuits to transmit the position sensor signal, so reliability, workability, cost, etc. There was a problem.

  In view of the above problems, high-performance sine wave drive is realized by controlling the phase difference between motor voltage and motor current by performing other control operation (speed open loop operation) based only on the speed command, not based on the position information. A method is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-112287.

  Here, in the converter / inverter power converter having a DC stage in the middle, when the AC power supply of the converter is particularly single-phase, the DC voltage converted to DC has a pulsation twice the AC power supply frequency caused by rectification. A frequency component is included. Although the pulsation frequency component can be reduced by increasing the capacity of the smoothing capacitor provided in the DC stage, it cannot be completely reduced, and the apparatus is increased by increasing the size of the smoothing capacitor. Therefore, a smoothing capacitor having a small capacity is used.

  When the DC voltage having the pulsation frequency component is converted into AC of variable frequency / variable voltage by an inverter and is supplied to a load such as an AC motor, the inverter output voltage and the motor current include the inverter operating frequency. In addition to the components, the difference component and the sum component of the pulsation frequency and the inverter operation frequency are included. Among these components, the difference component that becomes a low frequency component when the operating frequency and the pulsation frequency approach each other has a small impedance with respect to the low frequency in the motor, so that a large pulsating current flows by this component and the motor generated torque pulsates. The beat phenomenon may occur.

  FIG. 9 is a diagram for explaining the relationship between the waveform of the DC voltage and the U-phase motor current. The AC power supply is 200 V, the frequency is 50 Hz, and the waveform is shown when a 4-pole synchronous motor is driven at 3200 rpm using the above method.

  As shown in FIG. 9A, a ripple having a frequency twice that of the power supply is generated in the DC voltage. That is, when the AC power supply frequency is 50 Hz, a ripple of 100 Hz is generated.

  Here, the output frequency of the inverter when the rotation speed of the motor is 3200 rpm is 106.7 Hz because it is a 4-pole motor. Thus, when the inverter frequency approaches the ripple frequency of the DC voltage, a large pulsation occurs in the motor current on the inverter output side as shown in FIG. 9B, and the rotation of the motor becomes unstable. , Vibration and noise increase and efficiency deteriorates.

  As a method for suppressing this beat phenomenon, for example, Japanese Patent Laid-Open No. 2008-167568 can be cited. The suppression method of the beat phenomenon according to this publication is based on the estimated value of the pulsation frequency obtained by estimating the pulsation frequency of the DC voltage from the set value of the pulsation frequency calculated from the power supply frequency of the alternating voltage and the current detection value of the inverter. The beat phenomenon is suppressed by correcting the output voltage of the inverter using the detected current value.

Japanese Patent Laid-Open No. 2001-112287 JP 2008-167568 A

  However, the above Patent Document 2 does not describe the suppression of the beat phenomenon with respect to the phase difference control of the synchronous motor as shown in Patent Document 1, and other publications also relate to the technology. Is not found.

  Therefore, in the phase difference control of the synchronous motor as shown in Patent Document 1, when a power converter using a small-capacity smoothing capacitor is used, DC voltage ripple occurs and motor current pulsation occurs. Since the rotation of the motor becomes unstable, there is a possibility that vibration and noise will increase and efficiency will deteriorate.

  An object of the present invention is to solve the above-described problems, and is a position sensorless sine wave energization that ensures stable driving by suppressing pulsation of a motor current even when there is a ripple of DC voltage. The present invention is to provide a motor control device for a synchronous motor capable of achieving the above.

  A motor control device according to an aspect of the present invention is connected to a rectifier circuit that rectifies a DC voltage using a single-phase AC power source as an input, and converts the DC voltage obtained by the rectifier circuit into a multi-phase AC voltage. An inverter that drives a synchronous motor, a DC voltage detection unit that detects a DC voltage, and a motor current detection that detects a motor current of any one of a plurality of phases flowing through the synchronous motor and outputs a motor current signal Unit, a zero cross point detection unit that detects a zero cross point of the AC voltage of the single-phase AC power supply, and a control device that generates a pulse width modulation signal for controlling the inverter. The control device includes drive wave data creating means for creating drive wave data for driving the synchronous motor for each of a plurality of phases in response to the rotation speed command value for setting the rotation speed being given. The phase difference that detects phase information of a specific phase from the driving wave data created by the driving wave data creation means, detects the phase difference from the motor current signal output from the motor current detector, and outputs phase difference information A detection means, a phase difference control means for calculating a duty reference value for controlling the phase difference information output from the phase difference detection means to a target value, drive wave data created by the drive wave data creation means, PWM signal generating means for generating a pulse width modulation signal based on the duty reference value, and a correction unit for correcting to suppress the beat phenomenon, the correction unit according to the duty reference value Corrects the rotational speed command value of the synchronous motor according to the duty reference value calculated by the phase difference control means according to the pulsation of the DC voltage detected by the detection unit or the elapsed time from the detection of the zero cross point by the zero cross point detection unit .

  Preferably, when the duty reference value is less than the predetermined value, the correction unit corrects the duty reference value calculated by the phase difference control unit according to the pulsation of the DC voltage detected by the DC voltage detection unit.

  Preferably, the correction unit corrects the rotation speed command value when the duty reference value is equal to or greater than a predetermined value.

  The motor control device of the present invention includes a correction unit that suppresses the pulsation of the current waveform flowing through the synchronous motor, and the correction unit corresponds to the pulsation of the DC voltage detected by the DC voltage detection unit according to the duty reference value. The rotational speed command value of the synchronous motor according to the duty reference value calculated by the phase difference control means or the elapsed time from the detection of the zero cross point in the zero cross point detection unit is corrected. Depending on the duty reference value, it is possible to detect a stable waveform with a constant amplitude by suppressing the pulsation of the current waveform by correcting the duty reference value or correcting the rotation speed, and drive the synchronous motor stably. It is possible to reduce vibration and noise, and to suppress deterioration of efficiency.

It is a block diagram of the motor control apparatus according to the embodiment of the present invention. It is a figure explaining the system which correct | amends the duty reference value of the motor control apparatus according to embodiment of this invention. It is another figure which correct | amends the duty reference value of a motor control apparatus. It is a figure explaining the case where the rotation speed correction of the motor control apparatus according to the embodiment of the present invention is executed. It is a figure explaining the rotation speed correction | amendment of the motor control apparatus according to embodiment of this invention. It is a figure explaining the numerical value of the rotation speed correction factor data table according to the embodiment of the present invention. It is a figure explaining the relationship between the DC voltage waveform by the rotation speed correction | amendment according to embodiment of this invention, and a U-phase motor current. It is another figure explaining the relationship between a DC voltage waveform and a U-phase motor current. It is a figure explaining the relationship between the waveform of DC voltage, and a U-phase motor current.

  Embodiments of the present invention will be described below 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.

FIG. 1 is a block diagram of a motor control device according to an embodiment of the present invention.
Referring to FIG. 1, a motor control device includes a synchronous motor 1 including a multi-phase (three-phase) coil in a stator and a permanent magnet in a rotor, an inverter 2, a converter circuit 3, an AC power supply 4, It comprises a current sensor 5, a motor current detection amplifier unit 6, a zero cross point detection unit 30, a voltage sensor 31, a voltage sensor 32, a DC voltage detection unit 19, and a controller 7 which is a microcomputer.

  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.

  Specifically, converter circuit 3 includes a diode full-wave rectifier circuit 20, a smoothing capacitor 21 between buses, and a reactor 22.

  The reactor 22 is provided for the purpose of improving the power factor of the AC power supplied to the converter circuit 3. By this converter circuit 3, the AC voltage of the AC power supply 4 is converted into a DC voltage and supplied to the inverter 2.

  The current sensor 5 detects a motor current a flowing in a specific phase (U phase in FIG. 1) among the 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 point detector 30. Then, the zero cross point 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.

  Further, the voltage sensor 32 detects a DC voltage of a DC power source supplied from the converter circuit 3 to the inverter 2. The DC voltage detected by the voltage sensor 32 is given to the DC voltage detector 19. Then, the DC voltage detector 19 monitors the DC voltage detected by the voltage sensor 32 and gives the controller 7 a voltage signal indicating the voltage level of the DC voltage.

  The controller 7 includes a phase difference detection unit 8, a target phase difference information storage unit 9, an addition unit 10, a PI calculation unit 11, a rotation speed setting unit 12, a sine wave data table 13, and a sine wave data creation unit. 14, the PWM creation unit 15, the rotation speed correction unit 16, the rotation speed correction rate data table 17, and the duty reference value correction unit 18 are performed in software. In the present embodiment, the phase difference control is executed by a method similar to the phase difference control method described in JP-A-2001-112287.

  The phase difference detection unit 8 takes in and converts the motor current signal b given from the motor current detection amplifier unit 6 by A / D conversion at a predetermined timing, and samples each current sampled every two motor drive voltage phase periods. The data is integrated to obtain a motor current signal area, and the area ratio of the two motor current signal areas is output as phase difference information.

  The target phase difference information is stored in the target phase difference information storage unit 9. Error data between the target phase difference information and the phase difference information is calculated by the adding unit 10.

  The PI calculation unit 11 calculates proportional error data and integral error data with respect to the calculated error data, and outputs a duty reference value. The addition unit 10 and the PI calculation unit 11 constitute a phase difference control unit.

  The duty reference value correcting unit 18 takes in the voltage signal generated by the DC voltage detecting unit 19 by A / D conversion, and calculates the duty reference calculated by the PI calculating unit 11 according to the detected voltage level of the DC voltage. The value is corrected, and the corrected duty reference value is output to the PWM creating unit 15.

  The rotation speed setting unit 12 sets a rotation speed command targeted for the synchronous motor 1, and the sine wave data table 13 includes a table of a predetermined number of data.

  The rotation speed correction rate data table 17 stores correction rate data for a target rotation speed.

  The rotation speed correction unit 16 extracts correction rate data corresponding to the elapsed time of the zero cross point signal generated by the zero cross point detection unit 30 from the rotation speed correction rate data table, and uses this to calculate the rotation rate setting unit 12. The set rotation speed is corrected, and the corrected rotation speed is output to the sine wave data creation unit 14.

  The sine wave data creation unit 14 reads out sine wave data corresponding to each phase of the motor coil terminals U, V, and W from the sine wave data table 13 according to the corrected rotation number output from the rotation number correction unit 16 and the passage of time. At the same time, the U-phase motor drive voltage phase information c is output from the U-phase sine wave data.

  The PWM generator 15 outputs a PWM waveform to the drive element of the inverter 2 for each phase from the sine wave data and the corrected duty reference value.

  The current sensor 5 may be a so-called current sensor composed of a coil and a Hall element, or a current transformer.

  In this example, the case of detecting the U phase will be described. However, when the motor current of each phase as well as one phase is detected, higher accuracy can be achieved. Furthermore, the sine wave data may be created by calculation instead of being created based on the sine wave data table 13.

  Furthermore, although the constituent elements of the constituent elements 8 to 18 are processed by the controller 7 in a software manner, the present invention is not limited to this and may be configured in a hardware configuration as long as the same processing is performed.

  Although the motor drive waveform is a sine wave, the sine waveform allows a smooth motor current to be supplied, thereby reducing vibration and noise. However, the present invention is not limited to this, and if a drive waveform that provides a motor current that matches the magnetic flux of the motor rotor is energized, a more efficient drive is possible.

  The area ratio of the two motor current signal areas detected in the two motor drive voltage phase periods is calculated by the phase difference detector 8, and this result is used as phase difference information. PI calculation is performed by the PI calculation unit 11 on the error amount between the phase difference information and the target phase difference information. The duty reference value that is the calculation result of the PI calculation unit 11 is corrected by the duty reference value correction unit 18, and the PWM creation unit 15 is obtained from the corrected duty reference value and the corrected rotation speed separately from the rotation speed correction unit 16. The synchronous motor 1 is driven by calculating the output duty ratio in each case from the sine wave data, creating a PWM signal, and applying it to the motor coil via the inverter 2.

  That is, the magnitude of the drive voltage (duty width of the PWM duty) is determined by a phase difference control feedback loop for controlling the motor current phase difference with respect to the motor drive voltage (output duty) to be constant, and the synchronous motor 1 is rotated in a desired rotation. The number of rotations is determined by sine wave data output at a desired frequency in order to rotate the number. Thus, the motor can be driven and controlled with a desired phase difference and a desired rotation speed.

  It should be noted that when the motor is activated, each phase is forcibly energized, a rotating magnetic field is applied, forced excitation is performed, and control is performed by the above method during normal driving.

  Here, as described in JP-A-2001-112287, the synchronous motor can be driven and controlled by the phase difference control of the present invention.

  As described above, in the present embodiment, there is a possibility that ripple occurs in the DC voltage as described with reference to FIG.

  Therefore, as described with reference to FIG. 9B, a large pulsation may occur in the motor current on the inverter output side, and phase difference control may become unstable. Therefore, since the rotation of the motor becomes unstable, vibration and noise increase, and efficiency may deteriorate.

  In the motor control device according to the present embodiment, a method for suppressing the pulsation of the motor current by correcting the duty reference value will be described below.

First, the case where the pre-correction duty reference value is less than the predetermined threshold A will be described.
FIG. 2 is a diagram illustrating a method for correcting the duty reference value of the motor control device according to the embodiment of the present invention. Here, a case where the duty reference value is sufficiently smaller than the maximum duty reference value is shown.

  With reference to Fig.2 (a), the alternating voltage waveform is shown here. The AC power supply 4 is 200 V and the frequency is 50 Hz.

FIG. 2B shows a DC voltage waveform with respect to the AC voltage waveform shown in FIG.
As described above, a case where a small-capacity smoothing capacitor is used is shown. Since the capacity of the smoothing capacitor is not so large as to completely eliminate ripples, ripples may occur in the DC voltage waveform. It is shown. That is, as described above, a ripple having a frequency 100 Hz that is twice that of the AC power supply occurs.

  As described above, ripples also occur in the motor voltage applied to the synchronous motor 1 due to the occurrence of the ripples, and a large pulsation occurs in the motor current on the inverter output side.

  In the motor control device according to the embodiment of the present invention, the duty reference value is corrected so as to cancel the ripple generated in the motor voltage applied to the synchronous motor.

  The product of the duty reference value calculated by the PI calculation unit 11 and the DC voltage corresponds to the amplitude of the motor voltage applied to the synchronous motor 1.

  Therefore, when a ripple occurs in the DC voltage, the amplitude of the motor voltage applied to the synchronous motor 1 can be made constant by correcting the duty reference value according to the ripple.

  In the embodiment of the present invention, in the duty reference value correction unit 18 of FIG. 1, the DC voltage detection value detected by the DC voltage detection unit 19 by the A / D conversion, the reference DC voltage (for example, 280 V), and the duty reference before correction The corrected duty reference value is calculated using the value and output.

Specifically, the duty reference value is corrected based on the following equation.
Duty reference value after correction = Duty reference value before correction × Reference DC voltage / DC voltage detection value (1)
FIG. 2C shows the duty reference value before correction and the duty reference value after correction.

  As shown in FIG. 2C, the waveform of the pre-correction duty reference value is constant, but the post-correction duty reference value is a waveform that cancels the ripple according to the ripple of the DC voltage.

  FIG. 2D shows the amplitude of the motor voltage applied to the synchronous motor 1 obtained by multiplying the DC voltage by the duty reference value.

  As shown in FIG. 2D, the motor voltage amplitude before correction is a waveform affected by the ripple of the DC voltage, but the corrected motor voltage amplitude is after correction to cancel the ripple. Since the duty reference value is multiplied, a constant amplitude value is set.

  By correcting the amplitude of the motor voltage applied to the synchronous motor by correcting the duty reference value and canceling the ripple, the large pulsation generated in the motor current can be suppressed and the phase difference control can be stably executed. It becomes possible.

  In this case, the rotational speed correction described later is not executed in order to suppress the beat phenomenon by correcting the duty reference value.

  As will be described later, when the pre-correction duty reference value is smaller than the predetermined threshold A, the rotational speed correction unit 16 sets the rotational speed correction amount to zero, substantially does not perform the rotational speed correction, and corrects the duty reference value. Only do to suppress the beat phenomenon.

Next, a case where the pre-correction duty reference value is equal to or greater than a predetermined threshold A will be described.
The maximum duty ratio, which is the on / off ratio of the PWM signal supplied to the inverter 2, is 100%: 0%. Therefore, the duty reference value has a maximum value, and a duty reference value exceeding the maximum duty reference value cannot be taken.

  FIG. 3 is another diagram for correcting the duty reference value of the motor control device. Here, a case where the duty reference value before correction is larger than that in FIG. 2 and the duty reference value before correction is equal to or greater than the threshold value A will be described.

  3A and 3B show an AC voltage waveform and a ripple DC voltage waveform with a frequency of 100 Hz which is twice that of the AC power supply, as described in FIGS. 2A and 2B. Has been.

FIG. 3C shows the duty reference value before correction and the duty reference value after correction.
As shown in FIG. 3C, the duty reference value before correction is the maximum duty reference value.

  In this case, if the duty reference value is corrected based on the method according to the above equation (1), the maximum duty reference value cannot be exceeded, and the excess value will stick to the maximum duty reference value.

  FIG. 3D shows the amplitude of the motor voltage applied to the synchronous motor 1 obtained by multiplying the DC voltage by the duty reference value.

  As shown in FIG. 3D, the amplitude of the motor voltage before correction is a waveform affected by the ripple of the DC voltage, and the amplitude of the motor voltage corrected by the corrected duty reference value. However, the fluctuation of the DC voltage cannot be completely cancelled, and halfway correction is made, and the beat phenomenon cannot be suppressed.

  In other words, in order to cancel the fluctuation of the DC voltage by correcting the duty reference value and suppress the beat phenomenon, the corrected duty reference value does not stick to the maximum duty reference value, and the DC voltage is below the maximum duty reference value. The waveform needs to cancel the ripple according to the ripple.

  Therefore, in the motor control device according to the embodiment of the present invention, when the duty reference value before correction is greater than or equal to threshold A, specifically, the duty reference value after correction is based on the following equation (1). When there is a possibility of exceeding the maximum value, the beat phenomenon is suppressed by correcting the rotational speed without correcting the duty reference value. In this case, the duty reference value correction unit 18 does not perform the duty correction, and only the rotation speed correction is performed to suppress the beat phenomenon.

Next, a case where the beat phenomenon is suppressed by correcting the rotational speed will be described.
FIG. 4 is a diagram illustrating a case where the rotational speed correction of the motor control device according to the embodiment of the present invention is executed. Here, a case where the duty reference value before correction is larger than that in FIG. 2 and the duty reference value before correction is equal to or greater than the threshold value A will be described.

  4 (a) and 4 (b) show an AC voltage waveform and a ripple DC voltage waveform with a frequency of 100 Hz that is twice that of the AC power supply, as described in FIGS. 2 (a) and 2 (b). Has been.

FIG. 4C shows the duty reference value before correction.
As shown in FIG. 4C, since the duty reference value before correction is greater than or equal to the threshold value A, the duty reference value is not corrected.

  FIG. 4D shows the amplitude of the motor voltage applied to the synchronous motor 1 obtained by multiplying the DC voltage by the duty reference value.

FIG. 5 is a diagram for explaining the rotational speed correction of the motor control device according to the embodiment of the present invention.
With reference to Fig.5 (a), the alternating voltage waveform is shown here. The AC power supply 4 is 200V and the frequency is 50 Hz. The rotation speed command value (rotation speed before correction) of the motor is 3200 rpm. When the motor rotation speed command value (rotation speed before correction) is 3200 rpm, the output frequency of the inverter is 106.7 Hz because it is a 4-pole motor.

FIG. 5B shows a DC voltage waveform with respect to the AC voltage waveform shown in FIG.
As described above, a case where a small-capacity smoothing capacitor is used is shown. Since the capacity of the smoothing capacitor is not so large as to completely eliminate ripples, ripples may occur in the DC voltage waveform. It is shown. That is, as described above, a ripple having a frequency 100 Hz that is twice that of the AC power supply occurs.

  FIG. 5C shows a zero cross point signal corresponding to the AC voltage waveform shown in FIG. Specifically, the zero cross point detector 30 monitors the AC power supply 4 and outputs a zero cross point signal in which the AC voltage crosses 0 in the AC voltage waveform.

  In the present embodiment, the time when the rising edge of the zero cross point signal occurs is set to 0, and the elapsed time from this time is measured by the controller 7 which is a microcomputer.

  The rotation speed correction unit 16 reads the rotation speed correction rate data table 17 and extracts correction rate data according to the passage of time. The rotation speed correction unit 16 multiplies the target rotation speed set by the rotation speed setting unit 12 by the correction rate data. The calculated value is output to the sine wave data creating unit 14 as a target rotational speed (corrected rotational speed) corrected.

  FIG. 6 is a diagram illustrating numerical values in the rotation speed correction rate data table according to the embodiment of the present invention.

  Referring to FIG. 6, a data table of elapsed time and rotation speed correction rate is shown as a correction rate data table.

Specifically, a numerical value every 0.2 ms is shown with 10 ms as one cycle.
The numerical values in the rotation speed correction rate data table are obtained in advance by experiments to reduce the pulsation of the motor current so that the motor can be driven stably.

  FIG. 5D is a rotation speed correction rate data line based on the correction rate data of FIG. 6 with 0% as a reference.

  As shown in FIG. 5D, the rotation speed correction rate data line is a data line that matches the DC voltage waveform.

  For example, when the rotation speed before correction is 3200 rpm and the elapsed time is 7.0 ms, the correction rate data is 1.90% from FIG. 6, so the rotation speed correction value is 3200 rpm × 1.90% = 60.8 rpm. It becomes.

  That is, in this example, the zero cross point signal is detected, and the time when the rising edge of the zero cross point signal is generated is set to 0, and the rotation speed correction rate is set in accordance with this DC voltage waveform.

  By setting the rotation speed correction factor according to the DC voltage waveform, it is possible to suppress a pulsation in the current waveform and detect a stable waveform with a constant amplitude.

FIG. 5E is a diagram for explaining the pre-correction rotational speed and the post-correction rotational speed.
The case where the post-correction rotational speed is corrected according to the rotational speed correction rate data line is shown.

  FIG. 7 is a diagram for explaining the relationship between the DC voltage waveform by the rotation speed correction and the U-phase motor current according to the embodiment of the present invention.

  Referring to FIG. 7 (a), ripple is generated in the DC voltage as shown in FIG. 9 (a). By correcting the target rotational speed according to the method described above, FIG. 7 (b) As shown in FIG. 5, the pulsation of the motor current can be greatly reduced. Thereby, stable driving of the motor can be realized, vibration and noise can be reduced, and deterioration of efficiency can be suppressed.

FIG. 8 is another diagram for explaining the relationship between the DC voltage waveform and the U-phase motor current.
In this case, when the duty reference value is smaller than the threshold value A, the duty reference value is corrected and the rotation speed correction is also executed according to the above method. When both the duty reference value and the rotation speed correction are performed, the correction becomes too much and the beat phenomenon cannot be suppressed.

  In the motor control device according to the present embodiment, the correction method is switched according to the duty reference value, the duty reference value is corrected when the duty reference value is smaller than threshold A, and the rotation is performed when the duty reference value is greater than or equal to threshold A. By correcting the number, beat phenomenon can be suppressed, vibration and noise can be reduced, and deterioration of efficiency can be suppressed.

  As described above, in the motor control device according to the present embodiment, a small-capacitance capacitor can be used between the buses of the inverter, and in that case, even under conditions where a large ripple is generated in the DC voltage, Stable driving can be realized, vibration and noise can be reduced, and deterioration in efficiency can be suppressed. In addition, the motor output can be controlled with high accuracy.

  In addition, by using a capacitor having a considerably smaller capacity than the conventional smoothing capacitor between the buses of the inverter, for example, a capacitor having a capacity of about half that of the conventional capacitor, a small, light, and low-cost inverter device can be realized. Is possible.

  In addition, by performing inverter control using the detected AC voltage / current phase difference information, the rotor position is detected in motor drive by 180 degree energization including low noise, low vibration, and high efficiency sinusoidal energization. Therefore, it is possible to perform stable rotation without using a sensor.

  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 synchronous motor, 2 inverter, 3 converter circuit, 4 AC power supply, 5 current sensor, 6 motor current detection amplifier unit, 7 controller, 8 phase difference detection unit, 9 target phase difference information storage unit, 10 addition unit, 11 PI calculation , 12 rotation speed setting section, 13 sine wave data table, 14 sine wave data creation section, 15 PWM creation section, 16 rotation speed correction section, 17 rotation speed correction rate data table, 18 duty reference value correction section, 19 DC voltage Detection unit, 20 diode full wave rectification circuit, 21 smoothing capacitor, 22 reactor, 30 zero cross point detection unit.

Claims (3)

A rectifier circuit that rectifies a single-phase AC power source into a DC voltage as an input;
An inverter connected to the rectifier circuit and converting a DC voltage obtained by the rectifier circuit into a plurality of phases of AC voltage to drive a synchronous motor;
A DC voltage detector for detecting the DC voltage;
A motor current detector for detecting a motor current of any one of a plurality of phases flowing through the synchronous motor and outputting a motor current signal;
A zero-cross point detector for detecting a zero-cross point of the AC voltage of the single-phase AC power source;
A control device for generating a pulse width modulation signal for controlling the inverter,
The controller is
Drive wave data creation means for creating drive wave data for driving the synchronous motor for each phase of the plurality of phases in response to the rotation speed command value for setting the rotation speed being given,
The phase information of the specific phase is detected from the drive wave data created by the drive wave data creation means, the phase difference from the motor current signal output from the motor current detector is detected, and the phase difference information is output. Phase difference detection means;
A phase difference control means for calculating a duty reference value for controlling the phase difference information output from the phase difference detection means to a target value;
PWM signal generating means for generating the pulse width modulation signal based on the driving wave data generated by the driving wave data generating means and the duty reference value;
A correction unit for suppressing pulsation of a current waveform flowing in the synchronous motor,
In the correction unit, the duty reference value calculated by the phase difference control unit according to the pulsation of the DC voltage detected by the DC voltage detection unit or the zero cross point detection unit according to the duty reference value A motor control device for correcting a rotational speed command value of the synchronous motor according to an elapsed time from detection of a zero cross point.   When the duty reference value is less than a predetermined value, the correction unit calculates the duty reference value calculated by the phase difference control unit according to the pulsation of the DC voltage detected by the DC voltage detection unit. The motor control device according to claim 1, wherein correction is performed.   The motor control device according to claim 1, wherein the correction unit corrects the rotational speed command value when the duty reference value is equal to or greater than a predetermined value.

Images